The Sage Handbook of Evolutionary Psychology: Applications of Evolutionary Psychology [1 ed.] 2020947010, 9781526489166

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The Sage Handbook of Evolutionary Psychology: Applications of Evolutionary Psychology [1 ed.]
 2020947010, 9781526489166

Table of contents :
Half Title Page
Title Page
Copyright Page
List of Figures, Tables and Boxes
Notes on the Editor
and Contributors
Integration within Psychology
Evolutionary Psychology and Counseling and Psychotherapy
Evolutionary Psychology and Psychiatry
Evolutionary Psychology and Suicidology
Evolutionary Psychology and Mindfulness and Meditation: Easing the Anxiety of Being Human
Evolutionary Psychology and Environmental Sciences
Evolutionary Psychology and Public Health
Animal Ethics and Evolutionary Psychology
Applications to Law and Order
Evolutionary Psychology and Political Institutions
Evolutionary Psychology and Crime
Evolutionary Psychology and Policing: The Balance Between Aggression and Restraint
11: Evolutionary Psychology, Jurisprudence, and Sentencing
Evolutionary Psychology and Incarceration
Evolution and Punishment
Evolutionary Psychology and Corrections and Rehabilitation
Evolutionary Psychology and Organized Crime
16: Evolutionary Psychology and Warfare
Applications to Technology, Communications, and the Future
Evolutionary Psychology and Artificial Intelligence: The Impact of Artificial Intelligence on Human Behaviour
Evolutionary Psychology and Robotics
Evolutionary Psychology and Dangerous Driving Behaviour
20: Evolutionary Psychology and Mass Media
Evolutionary Psychology and Communication
Evolutionary Psychology and Climate Change: Understanding the Impact of Time Perspective on Carbon Emissions across 75 Countries
Evolutionary Psychology and Thanatology: Responses to Death
Evolutionary Psychology and Reproduction
Evolutionary Psychology and Cyberwarfare

Citation preview

The SAGE Handbook of

Evolutionary Psychology

This page intentionally left blank

The SAGE Handbook of

Evolutionary Psychology

Applications of Evolutionary Psychology

Edited by

Todd K. Shackelford

SAGE Publications Ltd 1 Oliver’s Yard 55 City Road London EC1Y 1SP SAGE Publications Inc. 2455 Teller Road Thousand Oaks, California 91320 SAGE Publications India Pvt Ltd B 1/I 1 Mohan Cooperative Industrial Area Mathura Road New Delhi 110 044 SAGE Publications Asia-Pacific Pte Ltd 3 Church Street #10-04 Samsung Hub Singapore 049483

Editor: Donna Goddard Editorial Assistant: Umeeka Raichura Production Editor: Prachi Arora Copyeditor: Sunrise Setting Ltd. Proofreader: Derek Markham Indexer: Caroline Eley Marketing Manager: Camille Richmond Cover Design: Naomi Robinson Typeset by Cenveo Publisher Services Printed in the UK

Editorial arrangement © Todd K. Shackelford, 2021 Chapter 1 © Cezar Giosan, 2021 Chapter 2 © Riadh Abed and Paul St John-Smith, 2021 Chapter 3 © John F. Gunn III, Pablo Malo and C. A. Soper, 2021 Chapter 4 © James Carmody, 2021 Chapter 5 © Ulysses Paulino Albuquerque, Joelson M. B. Moura, Risoneide Henriques da Silva, Washington S. Ferreira Júnior and Taline C. Silva, 2021 Chapter 6 © Simon Russell, 2021 Chapter 7 © Diana Santos Fleischman, 2021 Chapter 8 © Michael Latner and Elissa Feld, 2021 Chapter 9 © Joseph L. Nedelec, 2021 Chapter 10 © Lois James, 2021 Chapter 11 © Eyal Aharoni and Morris B. Hoffman, 2021 Chapter 12 © Alina Simona Rusu, 2021 Chapter 13 © Anthony Walsh,

Cody Jorgensen and Jessica Wells, 2021 Chapter 14 © Ian A. Silver and Jamie Newsome, 2021 Chapter 15 © Russil Durrant, 2021 Chapter 16 © Anthony C. Lopez, 2021 Chapter 17 © Holly Wilson, Paul Rauwolf and Joanna J. Bryson, 2021 Chapter 18 © Robert Finkelstein, 2021 Chapter 19 © Deanna Singhal and David Wiesenthal, 2021 Chapter 20 © Gayle S. Stever, 2021 Chapter 21 © Ned Kock, 2021 Chapter 22 © Mark A. Caudell, 2021 Chapter 23 © James R. Anderson, 2021 Chapter 24 © Stephen Whyte and Benno Torgler, 2021 Chapter 25 © Robert Finkelstein, 2021

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act, 1988, this publication may be reproduced, stored or transmitted in any form, or by any means, only with the prior permission in writing of the publishers, or in the case of reprographic reproduction, in accordance with the terms of licences issued by the Copyright Licensing Agency. Enquiries concerning reproduction outside those terms should be sent to the publishers.

Library of Congress Control Number: 2020947010 British Library Cataloguing in Publication data A catalogue record for this book is available from the British Library 978-1-5264-8916-6

At SAGE we take sustainability seriously. Most of our products are printed in the UK using responsibly sourced papers and boards. When we print overseas we ensure sustainable papers are used as measured by the PREPS grading system. We undertake an annual audit to monitor our sustainability.

Contents List of Figures, Tables and Boxes Notes on the Editor and Contributors

vii ix


Evolutionary Psychology and Counseling and Psychotherapy Cezar Giosan



Evolutionary Psychology and Psychiatry Riadh Abed and Paul St John-Smith



Evolutionary Psychology and Suicidology John F. Gunn III, Pablo Malo, and C. A. Soper



Evolutionary Psychology and Mindfulness and Meditation: Easing the Anxiety of Being Human James Carmody



Evolutionary Psychology and Environmental Sciences Ulysses Paulino Albuquerque, Joelson M. B. Moura, Risoneide Henriques da Silva, Washington S. Ferreira Júnior, and Taline C. Silva



Evolutionary Psychology and Public Health Simon Russell



Animal Ethics and Evolutionary Psychology Diana Santos Fleischman



Evolutionary Psychology and Political Institutions Michael Latner and Elissa Feld



Evolutionary Psychology and Crime Joseph L. Nedelec



Evolutionary Psychology and Policing: The Balance Between Aggression and Restraint Lois James


Evolutionary Psychology, Jurisprudence, and Sentencing Eyal Aharoni and Morris B. Hoffman






Evolutionary Psychology and Incarceration Alina Simona Rusu



Evolution and Punishment Anthony Walsh, Cody Jorgensen, and Jessica Wells



Evolutionary Psychology and Corrections and Rehabilitation Ian A. Silver and Jamie Newsome



Evolutionary Psychology and Organized Crime Russil Durrant



Evolutionary Psychology and Warfare Anthony C. Lopez



Evolutionary Psychology and Artificial Intelligence: The Impact of Artificial Intelligence on Human Behaviour Holly Wilson, Paul Rauwolf, and Joanna J. Bryson



Evolutionary Psychology and Robotics Robert Finkelstein



Evolutionary Psychology and Dangerous Driving Behaviour Deanna Singhal and David Wiesenthal



Evolutionary Psychology and Mass Media Gayle S. Stever



Evolutionary Psychology and Communication Ned Kock



Evolutionary Psychology and Climate Change: Understanding the Impact of Time Perspective on Carbon Emissions across 75 Countries Mark A. Caudell



Evolutionary Psychology and Thanatology: Responses to Death James R. Anderson



Evolutionary Psychology and Reproduction Stephen Whyte and Benno Torgler



Evolutionary Psychology and Cyberwarfare Robert Finkelstein



List of Figures, Tables and Boxes FIGURES 2.1 Life history strategy trade-offs 29 3.1 Summary of posited antisuicide defences 68 3.2 A tentative mapping of hypothesized types of antisuicide mechanisms (keepers) across common diagnostic categories of mental disorder 74 4.1 Alarm-related components of experience forming a cycle of distress 97 4.2 Memory, imagination and emotion are symphonies of three interwoven experiential components 99 4.3 Components recognized as differentiated and connected 100 4.4 Attention shifts from differentiated components to arousal-neutral sensations of breathing 101 4.5 Re-perceiving reduces distress through a perceptual/attentional shift from what the thought is about – ‘I’m going to pass out’ – to the thought as an event in the mind/awareness – ‘This is a thought’ 101 5.1 Environment of Evolutionary Adaptedness definition (EEA), original version and extended version 110 5.2 Structure of the human naturalist mind 112 6.1 The impact of the food supply on the expression of obesity 125 6.2 Key determinants of psychological mechanisms and behaviour strategies 129 7.1 Charitable donations towards animal organizations as compared to animal use 151 9.1 Age-specific birth rates (per 1,000 women per year) in the 10 neighborhoods with the longest life expectancy compared to the 10 neighborhoods with the shortest life expectancy 198 10.1 Police balance between aggression and restraint 213 15.1 The basic dimensions of organized crime 298 19.1 GAM factors included in the investigation of modelling of aggressive or risky driving 384 19.2 Domestic box-office history for the Fast and Furious movies389 21.1 Path model showing a costly trait and its relationship with fitness 421 21.2 Probability of evolution of a new costly trait 423 21.3 Variation of the expected ratio between pay and pax424 21.4 The evolution of oral speech in humans 425 22.1 Effect of time orientation on total fertility as a function of education 446 22.2 Effect of time orientation on total fertility as a function of mortality level 447 22.3 Effect of time orientation on carbon emissions per capita as a function of investment in education 448



TABLES 2.1 Tinbergen’s four questions 3.1 The fitness costs of suicide 7.1 Days of suffering per kilogram of food weight produced by the animal adjusted for the badness of each day of life as estimated by animal welfare researchers 15.1 Approaches to defining organized crime 15.2 The functional structures of organized crime groups in relation to the key evolutionary processes that facilitate cooperation 18.1 Processes of mind and their computational equivalents 21.1 Oral speech and the two common characteristics of costly traits 22.1 Descriptive statistics for Model 1 22.2 Variable correlations for Model 1 22.3 Data sources, years, and future orientation scores 22.4 Descriptive statistics for Model 2 22.5 Variable correlations for Model 2 22.6 Relationship between total fertility rates, time orientation, mortality, and parental investment 22.7 Effect of time orientation and education on carbon emissions

27 54 158 297 305 354 426 441 441 443 445 445 446 448

BOX 2.1 Pathways for the persistence of disease and disorder 2.2 Evolutionary theories of depression 5.1 Structure and behavior of the human naturalistic mind

28 33 113

Notes on the Editor and Contributors THE EDITOR Todd K. Shackelford received his Ph.D. in evolutionary psychology in 1997 from the University of Texas at Austin. Since 2010, he is Professor and Chair of the Department of Psychology at Oakland University in Rochester, Michigan, where he is Co-Director of the Evolutionary Psychology Lab. In 2016, he was appointed Distinguished Professor by the Oakland University Board of Trustees. He led the founding of new Ph.D. and M.S. programs which launched in 2012. Shackelford has published around 300 journal articles and his work has been cited over 22,000 times. Much of Shackelford’s research addresses sexual conflict between men and women, with a special focus on men’s physical, emotional, and sexual violence against their intimate partners. Since 2006, Shackelford has served as editor of the journal Evolutionary Psychology, and in 2014 founded the journal Evolutionary Psychological Science as Editor-in-Chief.

THE CONTRIBUTORS Riadh Abed FRCPsych, Qualified in medicine from Baghdad and trained in psychiatry in the UK. Retired Psychiatrist, Medical Director and Hon. Senior Clinical Lecturer, University of Sheffield, UK. Currently is a medical member of Mental Health Tribunals, Ministry of Justice, UK. He is author of a number of novel evolutionary hypotheses on eating disorders, obsessive compulsive disorder and schizophrenia and has published both theoretical as well as research articles on a range of evolutionary psychiatry subjects. He is founding chair of the Evolutionary Psychiatry Special Interest Group (EPSIG) at the Royal College of Psychiatrists, UK. Eyal Aharoni is an Associate Professor of Psychology, Philosophy, and Neuroscience at Georgia State University in Atlanta. His research investigates violence risk assessment and the influence of emotion, cognitive bias, and other extra-legal factors on legal decision-making. Prior to his current appointment, Aharoni served as a Research Associate for the RAND Corporation. He completed a postdoctoral fellowship with appointments at The MIND Research Network for Neurodiagnostic Discovery and the University of New Mexico Psychology. He has also held research positions at the Research Center for Virtual Environments and Behavior and the Institute for Social, Behavioral, and Economic Research. Aharoni earned his PhD in psychology at UC Santa Barbara where he also served as a research fellow for the MacArthur Foundation’s Law and Neuroscience Project. Ulysses Paulino Albuquerque received his Ph.D. in biology in 2001 from the Universidade Federal de Pernambuco, Brazil. He is Full Professor of the Department of Botany at Universidade Federal de Pernambuco, Pernambuco, Brazil. In 2011, he led the founding of new Ph.D. program in Ethnobiology and Nature Conservation. Albuquerque has published around 316 journal articles,



200 chapter’s book and edited or authored 50 books (including new editions and translations). Much of actual Albuquerque’s research addresses how work our naturalistic mind. Albuquerque has served as editor of various peer-reviewed journals, and in 2011 co-founded the journal Ethnobiology and Conservation as Co-Editor-in-Chief. James R. Anderson is a Professor in Psychology at Kyoto University, Japan. For more than 30 years he has studied behaviour and cognition in a wide range of nonhuman primates in captivity in the wild, as well as human children and elderly people. Most of his research is in the following areas: the effects of early experience on social adjustment, the development of abnormal behaviour, improving welfare of captive primates through environmental enrichment, communicative behaviours including tactile and postural signals, gaze-following, feeding competition and the influence of dominance relationships, tool-use, the ontogeny and phylogeny of self-recognition, self-control, third-party social evaluations, sleep-related behavioural adaptations, and responses to dead and dying group members and other individuals. Joanna J. Bryson is recognised for broad expertise on intelligence and its impacts, advising governments, transnational agencies and NGOs globally. She holds two degrees each in psychology and AI (BA Chicago, MSc and MPhil Edinburgh, PhD MIT). From 2002–2019 she was Computer Science faculty at the University of Bath; she has also been affiliated with Harvard Psychology, Oxford Anthropology, Mannheim Social Science Research and the Princeton Center for Information Technology Policy. During her PhD she observed the confusion generated by anthropomorphised AI, leading to her first AI ethics publication ‘Just Another Artifact’ in 1998. She has remained active in the field including coauthoring the first national-level AI ethics policy, the UK’s (2011) Principles of Robotics. She is presently Professor of Ethics and Technology at the Hertie School of Governance in Berlin, Germany. James Carmody is a Professor in the Departments of Medicine, and Population and Health Sciences Division of Preventive and Behavioral Medicine at University of Massachusetts Medical School. His research is on how evolutionary and biological imperatives shape our habits of attending to experience, their effect on anxiety, and the degree to which they can be mitigated by mind–body training programmes like mindfulness and yoga. He is principal investigator on NIH-funded clinical trials of the clinical effects and mechanisms of mindfulness training. James studied and practised in Zen, Tibetan, Theravada and Advaita traditions in several countries over 50 years. He has been a therapist and leads retreats for clinicians with the goal of making the conceptualisation and psychological mechanisms of mindfulness straightforward, jargon-free and practically accessible for patients. His work has been featured in national and international media including the New York Times, NPR and ABC. Mark A. Caudell is a Medical Anthropologist working for the Food and Agriculture Organization of the United Nations and is adjunct faculty in the Department of Anthropology at Washington State University. His research centres on understanding how socioecological systems drive the emergence and transmission of environmental risks as well as pattern individual and community responses to these risks. His current work combines ethnographic and lab-based methods to identify the cultural and cognitive drivers of infectious disease and antimicrobial resistance in low- and middle-income countries. He has conducted research among foragers in the Congo Basin and farmers and pastoralists throughout sub-Saharan Africa and is funded by the National Science Foundation, The Fleming Fund, Amazon and the Paul G. Allen School for Global Animal Health at Washington State University. Currently, he is based in Nairobi, Kenya.

Notes on the Editor and Contributors


Risoneide Henriques da Silva is master in Botany (2018) from the Federal Rural University of Pernambuco, Brazil. She is currently PhD candidate in Ethnobiology and Nature Conservation by the same institution. Since 2016 she is a researcher associated at the Laboratory of Ecology and Evolution of Social-ecological Systems at the Federal University of Pernambuco, Brazil. Risoneide Henriques has an interest in understanding the cognitive aspects involved with human behaviour in relation to biota. Russil Durrant is a Senior Lecturer at the Institute of Criminology, Victoria University of Wellington, New Zealand, where he teaches courses in criminal, biosocial and investigative psychology. His research focuses on the application of evolutionary theory to understanding crime and crime-related phenomena. He is the author (or co-author) of five books including (with Tony Ward) Evolutionary Criminology: Towards a Comprehensive Explanation for Crime and (with Zoe Poppelwell) Religion, Crime, and Punishment: An Evolutionary Perspective. Elissa Feld earned a Masters in Public Policy at California Polytechnic State University, San Luis Obispo. Her research continues to focus on political psychology and public policy. Robert Finkelstein earned a DBA in Systems Theory and Cybernetics from George Washington University (GWU), an ApSci. in Operations Research (GWU), an MS in Operations Research (GWU), an MS in Physics (University of Massachusetts) and a BA in Physics (Temple University), as well as completing postgraduate courses in Physics at MIT. Dr Finkelstein is President, since 1985, of Robotic Technology Inc., a professional services firm that provides technical analyses, systems engineering, technology assessments, operations research, business development and other services in the fields of autonomous ground, air and water vehicles, intelligent systems, robotics for military and civil applications, and memetics. Dr Finkelstein is an Adjunct Professor in the graduate school at the University of Maryland Global Campus and is serving as a Co-Director of the Intelligent Systems Laboratory at the University of Maryland Clark School of Engineering. Diana Santos Fleischman is an Associate Professor of psychology at the University of Portsmouth in the UK. She received her PhD in evolutionary psychology at the University of Texas at Austin. Diana has been involved in animal ethics and effective animal advocacy for several years. From 2010–2012 Diana co-hosted ‘The Vegan Option’ podcast which explored many themes at the intersection of psychology and animal ethics. From 2017– 2019 Diana served on the board at Sentience Institute, a think tank devoted to exploring ways to expand humanity’s moral circle. Diana also has served on the grants board of the Animal Advocacy Research Fund which aims to promote research into effective animal advocacy. Cezar Giosan PhD is a faculty member of the Department of Psychology at the University of Bucharest and has a doctorate in psychology from the New School University, New York. He worked for a long time as a research psychologist in the top-ranked Department of Psychiatry at Weill Medical School of Cornell University. Dr Giosan has authored dozens of peer-reviewed publications in impact journals, including studies on the applications of evolutionary psychology in psychological interventions. He has tested, in the form of a randomized clinical trial, the efficacy of an evolutionary intervention for depression, and is the author of a published therapy protocol of Cognitive-Evolutionary Therapy.



John F. Gunn III PhD has a BA (Stockton University) and MA (Rutgers University – Camden) in psychology and a PhD in family science and human development (Montclair State University). John is currently a Postdoctoral Associate at the NJ Center on Gun Violence Research at Rutgers University, where he is investigating the role of firearms in suicide mortality on both small and large scales. His research interests include risk and protective factors for suicidal behaviour (such as access to a firearm; exposure to bullying), social connectedness and suicide, theoretical models of suicidal behaviour (such as evolutionary explanations for suicide) and the impact of media on suicide. John has written or co-authored over 20 scholarly publications, three edited books and 10 book chapters. Morris B. Hoffman has been a district judge in the state of Colorado since 1991. He is a member of the John D. and Catherine T. MacArthur Foundation’s Research Network on Law and Neuroscience, and a Research Fellow at the Gruter Institute for Law and Behavioral Research. He has published many law review articles, focusing on the areas of criminal law, jurisprudence, law and neuroscience, and jury history, in journals that include Stanford, University of Chicago, Vanderbilt, Duke, Northwestern, the University of Pennsylvania, Journal of Law and Biosciences and Journal of Philosophy, Science and Law. He has coauthored science papers in journals that include Proceedings of the National Academy of Sciences, Philosophical Transactions of the Royal Society B, Journal of Neuroscience, Trends in Neuroscience and Social Neuroscience. His book, The Punisher’s Brain: An Evolutionary History of Judge and Jury, was published in 2014. Lois James is an Assistant Professor in the Washington State University (WSU) College of Nursing, where she focuses on bias, stress, sleep and performance in ‘high-stress’ populations such as police officers, military personnel, nurses and top-tier athletes. She has received multiple honours and awards for her work, and is internationally recognised as a leading expert in her field. Her simulation-based research on the impact of bias on police decision making has significantly advanced what is known about how suspect race and ethnicity influences police officers during critical encounters with the public. She is the founding director of Counter Bias Training Simulation (CBTsim), a novel and innovative simulation-based implicit bias training program that has been featured in National Geographic and the recent feature-length documentary ‘bias’. Her work has been published extensively in academic journals, practitioner magazines and mainstream media such as the New York Times and the Washington Post. Cody Jorgensen is an Assistant Professor at Boise State University. He received his PhD from the University of Texas at Dallas in 2014. His main research interests include biosocial and developmental criminology, policing and forensics, and drug policy. Washington S. Ferreira Júnior received his Ph.D in Botany in 2015 at Federal Rural University of Pernambuco. Since 2016, he is Professor of the Biological Sciences course at Pernambuco University in Petrolina, Pernambuco, where he is coordinator of the Laboratory of Biocultural Investigations in the Semiarid. He is professor at the Postgraduate Program in Environmental Science and Technology at University of Pernambuco and the Postgraduate Program in Ethnobiology and Nature Conservation at Federal Rural University of Pernambuco. Ferreira Júnior has published around 40 journal articles, 40 book chapters and organized three books with partners. His research efforts are focused on understanding the structure, dynamics and evolution of local medical systems with an emphasis on the use of medicinal plants.

Notes on the Editor and Contributors


Ned Kock is Texas A&M Regents Professor and Chair of the Division of International Business and Technology Studies, in the Sanchez School of Business, at Texas A&M International University. He is an active member of the Human Behavior and Evolution Society and the Association for Information Systems. He has edited the Springer book Evolutionary Psychology and Information Systems Research, and guest-edited the Special Issue on Darwinian Perspectives on Electronic Communication published in the IEEE Transactions on Professional Communication. Ned has published his research in a number of high-impact journals including Communications of the ACM, Decision Support Systems, European Journal of Information Systems, European Journal of Operational Research, IEEE Transactions (various), Information & Management, Information Systems Journal, Journal of the Association for Information Systems, Journal of Management Information Systems, MIS Quarterly and Organization Science. His research interests include evolution and human behaviour toward technology, computational statistics and structural equation modelling. Michael Latner is a Professor of Political Science at California Polytechnic State University, San Luis Obispo, faculty scholar at Cal Poly’s Institute for Advanced Technology and Public Policy and a Senior Fellow with the Union of Concerned Scientists’ Center for Science and Democracy. His research focuses on electoral systems, coalition behavior, representation and voting rights. Anthony C. Lopez is Associate Professor of Political Psychology in the School of Politics, Philosophy, and Public Affairs, at Washington State University. He received his PhD from Brown University, and also received training as a research associate at the Center for Evolutionary Psychology, University of California, Santa Barbara. His research explores the evolutionary origins of warfare, as well as its constituent psychological dynamics, such as revenge, the nature of deterrence, collective action problems of warfare, extremist violence, and distinctions between offensive and defensive aggression. He serves as Associate Editor of Politics with the Evolution Institute and blogs regularly at Psychology Today. Pablo Malo studied medicine in the University of the Basque Country in Spain and psychiatry in the Psychiatric Hospital of Zamudio. Pablo is currently a clinical psychiatrist working in the Mental Health Center of Bombero Etxaniz, in Bilbao, Spain. His clinical interests include psychosis and severe mental disorders, violence and mental health disorders, intimate partner violence and evolutionary psychology. Pablo has co-authored a book about evolutionary psychiatry, written over 20 scholarly papers and is the editor of two blogs about evolutionary psychology and biology. Joelson M. B. Moura has a complete degree in Biological Sciences from the Universidade Federal Rural de Pernambuco (UFRPE), with an internship at the University of Coimbra (UC) in 2013. He received his master’s degree in Ethnobiology and Nature Conservation (UFRPE) in 2018. He is currently a Ph.D. candidate in the same program and integrates the Laboratory of Ecology and Evolution of Socioecological Systems (LEA) at the Universidade Federal de Pernambuco (UFPE) since 2016. The research carried out by Moura seeks to understand the processes that contributed to the evolution of the human mind. His work is in the perspective of evolutionary ethnobiology, which addresses the influence of the evolutionary past on current human behavior and how it reflects on the relationship between people and their environments.



Joseph L. Nedelec is an Associate Professor in the School of Criminal Justice at the University of Cincinnati. His research interests include biosocial criminology, evolutionary psychology, intelligence, quantitative behaviour genetics, and cybercrime. Dr Nedelec’s work has been published in a variety of journals including Criminology, Evolution and Human Behavior, Intelligence, Journal of Criminal Justice, Journal of Quantitative Criminology, Personality and Individual Differences and PLOS One, among others. Jamie Newsome received her doctorate in 2013 from the School of Criminal Justice at UC, and is currently the Research Coordinator for UCCI. Her research interests include the design, implementation and effectiveness of correctional interventions, and translating research into practice. Paul Rauwolf is an Assistant Professor (Lecturer) in Psychology at Bangor University, UK. Previously, he was a Postdoctoral Researcher in the Mathematics Institute at the University of Oxford and the School of Psychology at Bangor University. In 2016, he received his PhD in Computer Science from the University of Bath. His research takes an interdisciplinary perspective to better understand the utility and aetiology of biases in human decision-making. During his PhD, he used agent-based modelling to demonstrate that ignoring freely available information can be adaptive in a variety of contexts, such as maintaining cooperative societies. His current work focuses on understanding how the changing information and technological landscape impacts human decision-making under uncertainty. Simon Russell is a Research Fellow at the Great Ormond Street Institute of Child Health. Simon has conducted research in the fields of evolutionary science and public health, with a particular interest in health risk behaviours, obesity, inequalities in health, public health policy and epidemiology. Simon’s PhD entailed applying evolutionary principles to the obesity problem and other issues in public health, work that demonstrated that health behaviours and strategies are likely to be adaptive. Currently, Simon leads various research projects that have high policy relevance and often involve emerging methodologies. In recent years, Simon has specialised in simulating policy relevant interventions using causal inference techniques across longitudinal cohort data. Simon’s work involves applying epidemiological techniques to explore causes and consequences of obesity and to appraise the effectiveness of potential population policy action. Alina Simona Rusu is a biologist and psychologist and is currently an Associate Professor in the Department of Special Education, School of Psychology and Sciences of Education, BabeşBolyai University, Romania. She received her PhD in Animal Behaviour from University of Zurich, Switzerland. She is interested in interdisciplinary research of human prosocial behaviour in the context of inclusive institutions, as well as the applied values of human–animal interactions. Taline C. Silva received her Ph.D. in Botany in 2014 from the Federal Rural University of Pernambuco. Since 2016, she is Professor of the Biology course at State University of Alagoas in Palmeira dos índios, Alagoas, where she is coordinator of the Ethnobiology and Ecossistems conservation Lab. In 2018, she was member of Post graduation program in ethnobiology and nature conservation. Silva has published around 30 journal articles. She has experience in Ethnobiology and seeks to understand the factors that guide the complex relationship between people and nature, accessing knowledge, use and local perception of natural resources and landscape changes.

Notes on the Editor and Contributors


Ian A. Silver is an Assistant Professor at the Law and Justice Department at Rowan University and a Fellow at the University of Cincinnati Corrections Institute (UCCI). His research interests include correctional rehabilitation, incarceration, biopsychosocial criminology, and methodological issues. His recent work has appeared in Criminology and Public Policy, Aggressive Behavior, Journal of Offender Rehabilitation, Brain Injury and Journal of Criminal Justice. Deanna Singhal received a bachelor’s degree in psychology from Queen’s University in Kingston, and a master’s degree (exercise and health science) and doctoral degree (psychology: brain, behaviour, and cognitive science) from York University in Toronto. She is now a Faculty Service Officer in the Department of Psychology at the University of Alberta, Canada, with a primary role to support the Undergraduate Teaching and Learning Program. Her research interests include driving behaviour and cognitive workload, and her areas of teaching include introductory psychology and human neuropsychology. Paul St John-Smith FRCPsych. Trained at Oxford, graduated in natural sciences in 1976 and qualified in medicine in 1979. He then trained as a general practitioner and later joined the pharmaceutical industry for five years as a research physician in psychopharmacology investigating various antidepressants, hypnotics and other central nervous system agents including the benzodiazepine antagonist. In 1987 he returned to study psychiatry full time and worked in a number of London hospitals including Barnet, Guys, Greenwich, St Thomas’, and as a consultant in Hertfordshire. He has published on a range of areas in evolutionary psychiatry and has peer reviewed papers on psychopharmacology, placebo effects, professionalism, suicide and depression, as well as evolution. C. A. Soper is a psychotherapist in private practice in Lisbon, Portugal. He holds degrees from the University of Cambridge and the University of London and gained his PhD at the University of Gloucestershire for theoretical research into the evolutionary origins of suicide. His book, The Evolution of Suicide, was published in 2018. He has authored various other scholarly publications on suicide and suicidology, and presented at academic and clinical conferences on the subject. Soper’s clinical interests include the provision of therapeutic support for people affected by suicide and those suffering from alcoholism and other addictions. Gayle S. Stever is a Professor of Psychology at Empire State College/State University of New York. She has done research in the areas of parasocial theory, media effects and fan studies for over 30 years, and has authored numerous peer-reviewed articles on these subjects, in addition to writing The Psychology of Celebrity (2019). With her degree in lifespan development psychology, looking at media effects from a lifespan perspective is central to her work. Benno Torgler is Professor of Economics at the Centre for Behavioural Economics, Society and Technology (BEST) and School of Economics and Finance, Queensland University of Technology (QUT), Australia. He was also Adjunct Professor at the EBS Universität für Wirtschaft und Recht, Germany (2012–2015) and an Australian Research Council (ARC) Future Fellow (2011–2015). Before QUT he was a Research Affiliate and Lecturer in International and Comparative Political Economy in the Leitner Program at the MacMillan Center, Yale University; a Visiting Scholar in the Law and Economics Program at University of CaliforniaBerkeley; and a Visiting Scholar in the Andrew Young School of Policy Studies at Georgia State



University. His primary research interest lies in the area of economics, but he has also published in journals with a political science, social psychology, medical, sociology and biology focus. Anthony Walsh is a Professor Emeritus at Boise State University. He received his PhD from Bowling Green State University in 1983 after working as a marine, police officer and probation/ parole officer. His primary interest is biosocial criminology. He has published 43 books, the latest being God, Science, and Society: The Origin of the Universe, Intelligent Life, and Free Societies (Vernon, 2020). Jessica Wells is an Assistant Professor of Criminal Justice at Boise State University. She received her PhD in Criminal Justice and Criminology from Sam Houston State University in 2017. Her research is in the area of psychological and biosocial perspectives on criminal offending. Her publications focus on the consequences of stress and trauma exposure in samples of community members, incarcerated individuals and criminal justice professionals. Stephen Whyte is a Research Fellow in Behavioural Economics at the Centre for Behavioural Economics, Society and Technology (BEST) and School of Economics and Finance, Queensland University of Technology (QUT), Australia. His research focus explores largescale decision making in mate-choice settings. His work takes a multi-disciplinary approach in studying key sex differences in human behaviour, with work that bridges the fields of applied micro-economics, personality and social psychology, and evolutionary biology. His most recent research has explored such diverse topics as sex differences in nonbinary gender identification, male and female decision making in assisted reproductive and donor insemination medical environments, and preferences vs choice in cyber dating markets. David Wiesenthal received a bachelor’s degree in psychology from the City College of New York and a doctoral degree in social psychology from the State University of New York at Buffalo, followed by a postdoctoral fellowship from York University, Canada. He is now a Professor Emeritus and Senior Scholar at York University, Canada. He has been a Visiting Professor at the Hebrew University of Jerusalem and lectured as a Scandinavian Fellow at the Building Research Institute (Gävle, Sweden), Umeå University, Lund University, and the Helsingborg campus of Lund University, as well as the University of Costa Rica and the College of Psychologists (Costa Rica). His research interests are social and environmental influence processes, driver behaviours, scientific racism and research ethics. Holly Wilson is a second-year PhD student in the Department of Computer Science at the University of Bath. Her doctoral research involves investigating the neural correlates of both visual imagery and perception, and developing a brain computer interface which facilitates visual imagery reconstruction. Holly merged her interests in both artificial and natural intelligence by obtaining a BSc in Psychology followed by an MSc in Computer Science. In the first year of her PhD she focused on the ethics and impact of AI on people, on both an individual and societal level, alongside developing agent-based models of cultural evolution during the Upper Palaeolithic transition.


Integration within Psychology

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1 Evolutionary Psychology and Counseling and Psychotherapy Cezar Giosan

This chapter covers two important clinical applications of evolutionary psychopathology: (1) evolutionary-inspired psychological interventions, and (2) integration of evolutionary insights into couples therapy.

APPLICATIONS OF EVOLUTIONARY PSYCHOLOGY IN THE TREATMENT OF MENTAL DISORDERS In recent years, there has been an outpouring of attempts at evolutionary hypotheses of mental disorders. Different authors have proposed evolutionary explanations for depression (Durisko et al., 2015), anxieties (Gilbert, 2001; Nesse, 1998), schizophrenia (Crow, 2000), and personality disorders (Glenn et  al., 2011; Gutiérrez et  al., 2013; Hertler, 2014; Molina et  al., 2009; O’Reilly et  al., 2001), to name a few. Evolutionary explanations of mental disorders typically focus on the role of the

symptoms in increasing fitness, seeing them as evolved strategies serving an organism’s goal to survive and reproduce, or, conversely, center on the mismatch between our adaptations, evolved during the Environment of Evolutionary Adaptedness, and the modern world. An important practical question that arises from this substantial body of work revolves around the clinical implications of such theories. Although still speculative for the most part, evolutionary explanations of mental disorders do raise the intriguing possibility that psychological interventions that target fitness could have unique clinical benefits, which can go above and beyond those of current treatments. To this end, clinical psychologists, psychotherapists, or clinical researchers have attempted to bridge the gap between evolutionary theory and clinical practice by developing protocols that integrate evolutionary insights into the treatment of mental disorders. Some of these protocols have been



tested in randomized clinical trials with active comparators, while others have led to case studies or small-n pilot studies with no comparators. Also, some of these insights have been used in a cross-diagnostic manner – that is, same principles applied to various conditions – while others are specific to certain disorders. Alfonso Troisi and Michael McGuire have proposed that an evolutionary therapy’s main aim is to increase a patient’s short-term biological goals. In this light, evolutionary psychopathology makes the distinction between mental disorder and mental suffering, seeing many mental symptoms as adaptive reactions to situations associated with negative cost–benefit outcomes, which should not be treated if they do not cause distress (Troisi and McGuire, 2014). More specifically, in the view of Troisi and McGuire (2014), an evolutionary-driven therapy should (1) address cost–benefit outcomes; (2) facilitate the development of revised models of the social environments; and (3) aid the patient in developing capacities to achieve biologically relevant goals. This therapy should attempt to refine traits or to foster the use of alternative capacities that can help to achieve high-priority goals. In the more difficult cases, the authors argue, therapy should encourage patients with suboptimal functional capacities to actively search for environments where they can be successful in reaching highpriority goals (Troisi and McGuire, 2014).

Evolutionary Psychology and Case Conceptualization Case conceptualization – an explanation, offered by the therapist, of the problems bothering a patient – addresses the mental problem and its possible causes, the ethiopathogenetic processes presumed to be involved, and the positive or adverse effects of the proposed treatment. The efficient conceptualization of a problem can generate positive expectations about the treatment as well as a sense of prediction and control in

the patient, which can facilitate recovery (John and Segal, 2015; Kuyken et al., 2008). Historically, Sigmund Freud was the first to introduce case conceptualization as a key element in psychotherapy, through the analysis of the latent content of the dreams and interpretation of the neurotic symptoms (Freud, 2017). Today, case conceptualization is used in many therapeutic approaches. For instance, Cognitive Behavioral Therapy (CBT), one of the most widely used interventions for anxiety and depression, typically includes information about the causal mechanisms of the problem, that is, proximal causes of psychopathology, thus answering the ‘how’ questions from the ABC1 model (Ellis, 1994; Ellis et al., 2007). Case conceptualization in modern psychological interventions, however, typically includes only information about proximal causes of the symptoms. For instance, the ABC model leaves out the ‘how’ questions, focusing almost exclusively on the immediate mechanisms, such as dysfunctional thinking (Lam and Gale, 2000). Some therapeutic schools do offer distal explanations of symptoms, but none of them goes so deep as to bring into the therapeutic discourse, in a coherent, unified manner, the factors, forces, and elements that have shaped the evolution of our species. For example, psychoanalysis, the first school of thought that brought into discussion the distal causes of psychopathology, explains phobias through repression and displacement. A conflict originates in childhood and that conflict is either repressed or displaced onto the feared object. As an illustrative example, in ‘Notes upon a case of obsessional neurosis’ Freud attributed the Rat Man’s fear of relatives dying from being burrowed through by rats to guilt originating from a repressed desire he had earlier to see women that he knew naked (Williams, 2008). A phobia of snakes, from the same psychoanalytical perspective, was an unconscious fear of something else, which was to be unraveled in therapy through dream interpretation or analysis of slips of tongue.


Evolutionary psychopathology makes one giant leap further and addresses the distal, evolutionary causes of mental illness, namely, the evolutionary factors and forces that might be at the root of the presenting symptoms. By addressing the evolutionary causes of behaviors, evolutionary psychopathology finds itself in the privileged – and unique, to some extent – position to offer explanations of symptoms that typically make much sense to patients. By offering evolutionary explanations of symptoms, evolutionary psychology can enhance case conceptualizations of various treatment approaches in meaningful ways, potentially leading to better therapeutic outcomes. For instance, incorporating information about the hypothesized adaptive functions of the symptoms in the ABC, or the further refined ABCDE model (Ellis, 1994; Ellis et al., 2007), can lead to answers to ‘why’ questions, thus giving the patient a broader and more meaningful understanding of the problems they are confronting, which can lead to better acceptance.

Integration of Evolutionary Principles in Specific Forms of Therapy There have been several attempts to integrate evolutionary insights into various therapies in recent years. We begin by briefly describing the possible evolutionary resuscitation of Freud’s psychoanalysis and Jung’s analytical therapy and continue with a presentation of several evolutionary-driven therapy protocols that have been tested in randomized clinical trials. We will end this section with a brief presentation of the potential applications of evolutionary conceptualizations to other types of mental conditions.

Psychoanalysis Evolutionary psychotherapies place substantial importance on the therapeutic relationship. This is not something new. A century ago,


Sigmund Freud also made this central in his psychoanalytical psychotherapy. Indeed, one of the fundamental tenets of psychoanalytical psychotherapy is complete disclosure and communication: the patient is required to disclose anything that comes to their mind, without censorship. Thus, in Freudian psychoanalysis, the therapist took a central role in patients’ lives, since he would learn information about them that no one else was privy to. This unique and extremely close relationship (sessions were held several times per week) made Freud realize that it played a major role in the therapeutic outcomes and subsequently led to the definition of important constructs such as ‘transference’, which slowly replaced the initial emphasis on sexual symbolism with more nuanced understandings of the therapeutic alliance. Some scholars note that many psychotherapies – including evolutionary interventions – do not place sufficient importance on the relationship between the client and the therapist, or they may use that relationship to manipulate patients in what the therapist believes is in his own best interests. Kriegman (2000) argues that evolutionary insights can help reduce this risk in all forms of therapy, including psychoanalysis. Since psychoanalysis revolves around a deep relationship between two unrelated individuals and since one evolutionary principle is that we are hardwired to operate for our own benefits, it follows that the power the therapist has over the patient may sometimes be used to further the interests of the therapist, even if unconsciously (Kriegman, 1998). Becoming more aware of the distal mechanisms responsible for human behavior will place a therapist in a better position to avoid confusion between proximal and distal causes, ultimately benefitting the patient. For instance, as Kriegman describes hypothetically, a woman who dresses provocatively but is angered when perceived as a sexual object can be seen by an analyst as having an unconscious wish to be ravished or raped, with anger being a reaction formation. From an evolutionary lens, however, this interpretation might reflect a mix between projections



of male wishes and confusion of proximal (dressing sexily) and ultimate causes (woman’s self-interest enhancement through the stimulation of men). Becoming more aware of such nuances can help the therapeutic process and, therefore, evolutionary interpretations can bring value to such clinical situations.

Jungian Analytical Therapy While for classical psychoanalytical therapy the answer to the central question of what is wrong with the patient is their repressed memories, which the therapist tries to bring to the conscious level using strategies such as interpretation of dreams or slips of the tongue, in Carl Gustav Jung’s analytical therapy it is the archetypal intent that needs to be freed to unleash the patient’s full potential (Stevens, 2000). Jung’s theory of archetypes – universal, innate, archaic patterns and images of evolutionary origins that stem from the collective unconscious and which are the psychic counterpart of instinct – closely anticipated the notions of evolved mechanisms (innate strategies or algorithms) present in evolutionary theories today. Indeed, Jung rejected the tabula rasa understanding of human mind, common to his contemporaries (notably, John Watson in the United States) and replaced it with a theory that included the enormous influence of evolutionary factors on human behavior. Like evolutionary psychologists today, Jung argued that homeostasis, epigenesis, and adaptation are at the basis of the human psyche (Stevens, 1982, 1999), a paradigm that was in stark contrast to the blank-slate view of the mind from the Standard Social Sciences Model. Jung also rejected the sexualized Freudian interpretation of complexes such as Oedipus, anticipating the later works of John Bowlby, who argued that a child is attached to his/her mother because she is the caregiver (Bowlby, 1983, 2005). Also, of note, in clinical practice, Jung rejected Freud’s cold

objectivity in the therapeutic relationship, replacing it with something common in evolutionary therapies today, namely, the emphasis on a warm, reciprocal alliance. Not unlike the mismatch hypothesis (Giphart and van Vugt, 2018), psychopathology, in the Jungian paradigm, occurs when environmental mismatches at critical developmental stages lead to malfunction in ‘archetypal’ strategies (Stevens, 2000). Evolutionary psychology can add to analytical therapy the critical element of an even broader view of self than Jung conceived. Armed with modern knowledge about the functions of psychological mechanisms, therapists nowadays can bring into the clinical conceptualization a more expanded conversation about the role of these mechanisms in mental illness.

Evidence-Based Evolutionary Interventions After this brief theoretical presentation of the ways in which evolutionary insights can aid Freudian and Jungian therapies, we continue, in the section that follows, with the presentation of results from several empirical studies that have examined the benefits of integrating evolutionary insights into the treatment of depression and personality disorders.

Depression A Rwandan man once described the Rwandan treatment for depression to the 2001 National Book Award winner Andrew Solomon like this: You know, we had a lot of trouble with Western mental health workers, especially the ones who came here right after the genocide. They came and their practice did not involve being outside in the sunshine… which is, after all, where you begin to feel better. There was no drumming or music to get your blood flowing again – when you’re depressed and low you need to have your blood flowing. There was no sense that everyone had taken the day off so that the entire community


could come together to lift you up and bring you back to joy. There was no acknowledgement of the depression as something invasive and external that could actually be cast out of you again. Instead, they would take people one at a time into these dingy little rooms and have them sit around for an hour or so to talk about bad things that had happened to them. We had to ask them to leave the country. (Taljaard, n.d.)

While this description of an intervention for depression is in stark contrast to the standard one-hour-weekly therapy sessions common in Western cultures, it would not surprise an evolutionary therapist. Evolutionary psychopathologists view mild and moderate depression as functional states, serving adaptive functions (for a review, see Durisko et  al., 2015). For instance, as early as the 1990s, some authors conceptualized depression as a warning signal that biosocial goals have not been achieved (Nesse, 1991). The clinical implication of this line of thought is that finding solutions to reset the cost–benefit balance in favor of the patient should make depressed mood subside. In one of the earlier attempts at incorporating evolutionary insights into therapy for depression, McGuire and Troisi presented a clinical case of a patient who was depressed because of her inability to have children (i.e., major direct fitness problem). The treatment focused on addressing the dysregulating effects of the patient’s inability to reproduce, and, crucially, also formulated strategies to help this patient’s fitness through kin investment (i.e., inclusive fitness) (McGuire and Troisi, 1998: 270–271).

Treating Depression Downhill One evolutionary-based intervention protocol for depression is Treating Depression Downhill – TDD (Krupnik, 2014). TDD relies on an experiential approach and involves three distinct phases: (1) exploratory, in which the patients gain insight into their experience of defeat; (2) acceptance, in


which the patients terminate protest, that is, accept defeat as an immutable fact of their lives. This phase, which is the analogue equivalent of exposure therapy in anxiety disorders, is the centerpiece of TDD, as it facilitates the transition from protest to acquiescence; and (3) behavioral activation without the functional analysis component. Throughout TDD treatment, cognitive reappraisal takes place, following standard cognitive therapy approaches (e.g., analysis of distortions).

Evidence in Favor of TDD A preliminary study testing the efficacy of TDD was conducted in the form of a pilot observation on a sample of 12 participants, who met for 24 biweekly, 90-minute-long sessions (Krupnik, 2014). The protocol demonstrated effectiveness and specificity for depression, differentiating it from anxiety and personality disorders. The results showed marked decline in depressive symptomatology; however, the study was underpowered and the tentative trends in the dynamics of the participants’ scores did not reach statistical significance. The TDD protocol needs further testing in randomized controlled studies in comparison with established protocols for depression to better establish its efficacy. Since not all clients can engage in mindfulness, which is a key element in the acceptance phase in TDD, the same author replaced, in a further case study on a medicated patient, the acceptance phase from TDD with eye movement desensitization and ­reprocessing – EMDR (Shapiro, 2017). In this study, EMDR was used in a truncated form, and the nature of the targets was the subjective perception of loss, rather than actual events, while reappraisal took place along the protest–­ acceptance axis. The results showed that, at the end of the treatment and at followup assessment, the patient reported a more accepting disposition and decreased depressive symptoms (Krupnik, 2015).



Following the same line of investigation, another study conducted by the same author reported a case series of 21 military personnel diagnosed with depressive disorders, who received a course of TDD-EMDR (Krupnik, 2018). By the end of treatment (12 sessions), 80% of completers (n = 15) did not meet the criteria for depressive disorder and they showed a significant reduction in scores on the Beck Depression Inventory-II – BDI-II (Beck et  al., 1996) with a large effect size (d = 2.8) and an increase in accepting disposition (d = 1.8) on the Acceptance and Action Questionnaire (Bond et  al., 2011). Non-completers showed a similar decrease in the BDI-II scores at mid-treatment. The author observed no statistically significant decrease in anxiety symptoms on the BDI-II. These results suggest that TDD-EMDR may be an effective treatment for depressive disorders (Krupnik, 2018). They also indicate that this type of intervention may target depressive over anxiety symptoms (Krupnik, 2018), as was previously observed for the original TDD pilot study (Krupnik, 2014).

Therapeutic Lifestyle Change for Depression (TLC-D) Another attempt to incorporate evolutionaryinspired interventions in therapy is the Therapeutic Lifestyle Change for Depression (TLC-D) protocol (Karwoski et  al., 2005), which includes several evolutionary elements thought to have positive effects on mood. TLC-D combines several relevant factors, some of which are evolutionary-relevant, that are shown to be effective in the treatment of depression. These factors include: 1 Omega-3 fatty acid consumption (Peet and Horrobin, 2002). 2 Bright light exposure (Martiny et al., 2005). 3 Sleep hygiene (Mayers and Baldwin, 2006). 4 Aerobic exercise (Blumenthal et al., 2007). 5 Anti-rumination exercises (Fennell and Teasdale, 1987). 6 Social support (George, 1989).

Evidence in Favor of TLC-D Karwoski et al.’s (2005) protocol was retested with additional data and gender comparison by Jacobson et al. (2007). The authors examined TLC-D on 81 patients who underwent 12 sessions of TLC-D therapy, with followup evaluations at three and six months. The experimental group was compared to a Treatment as Usual (TAU) group, representing one-third of the sample. The results showed that the TLC-D group outperformed the control group. The results also showed that, at the end of the therapy, participants averaged a 17.8% decrease in BDI-II (Beck et al., 1996) scores, which represented a statistically significant 60.6% reduction from baseline. These improvements were stable, showing a 67.7% reduction at three-month follow-up, and 64.0% reduction at six-month follow-up. Further research on TLC-D continued to show promising results. In a study conducted by Botanov et al., (2012), 29 patients were recruited into a TLC-D protocol, in a two-toone random assignment (22 in TLC-D and 7 in TAU). The participants underwent 12 sessions of group therapy over 14 weeks and were assessed weekly with the BDI-II (Beck et al., 1996). The results showed a clinically significant response (>= 50% reduction in BDI-II scores) in 77.3% of the participants in the TLC-D condition versus 28.6% in the TAU condition, and, notably, no significant change in BDI-II scores was observed from treatment end to six-month follow-up, suggesting low relapse rates post-treatment.

Cognitive Evolutionary Therapy for Depression (CETD) Another clinically tested evolutionary-driven intervention protocol for depression is Cognitive Evolutionary Therapy for Depression (CETD) (Giosan, 2020; Giosan, Cobeanu, Wyka, et  al., 2020; Giosan, Cobeanu et  al., 2014). As conceptualized by the authors,


besides targeting the proximal causes of depression as is standard in CBT, CETD focuses on distal causes as well, such as inclusive fitness or reproductive success. While sharing common underpinnings with CBT, CETD adds the inclusion of evolutionary conceptualizations of the patient’s symptoms and the targeting of fitness-related problems. Very much unlike classical Cognitive Therapy for Depression, in which the problems that preoccupy the patient are identified by the patients during the therapy sessions, CETD starts from the premise that depressive symptoms reflect fitness difficulties, some of which are unknown to the patients, and which can be identified via an evaluation of the patient’s fitness prior to the first session. By identifying a patient’s fitness problems at intake, the CETD therapist thus is pre-equipped with this knowledge at the first session and can start working with the patient on problematic areas right away. Along with these evolutionary-driven behavioral activations, discussions about human nature from evolutionary perspectives are also taking place during CETD, such as modularity (Cosmides and Tooby, 1994), parental investment theory (Buss et  al., 1990), conspicuous consumption (Sundie et  al., 2011), or costly signaling theory (Fraser, 2012), all of which can facilitate acceptance, a key CBT ingredient (Chamberlain and Haaga, 2001). The instrument that CETD therapists use to identify a patient’s fitness difficulties is the Evolutionary Fitness Scale – EFS (Giosan et  al., 2018). The EFS is a 58-item scale assessing mismatches between the Environment of Evolutionary Adaptedness and the modern world, such as in physical activity or nutrition, environmental misfits, or fitness-related factors such as health of the actor, his/her partner and their extended families, attractiveness (both of the actor and partner), status, resource control, extended family, social capital, and mate value. Some examples of items are: ‘I visit my relatives frequently’, or ‘I am an active outdoors person’, which are actionable in therapy.


The CETD manual (Giosan, 2020) provides the evolutionary therapist with concrete examples of therapeutic interventions on each of the EFS items. For instance, a negative endorsement of the EFS item ‘I have at least one best friend’ should be dealt with by exploring the reasons and refuting dysfunctional thinking, as well as exploring modalities to increase connectedness with at least one non-relative. Likewise, a negative endorsement of the EFS item ‘My family brag about me’ should be dealt with by discussing solutions to increase status and dominance (e.g., more education if appropriate, job change, community involvement, etc.) (‘Darwinian Psychotherapy’, 2019; Giosan, 2020). As far as the therapeutic alliance is concerned, the CETD protocol advocates that the therapist go beyond the recommendations of interventions such as Rational Emotive Behavior Therapy – REBT (where the alliance is centered on unconditional acceptance, empathy, humor, and genuineness) or psychoanalysis (friendly neutrality) and try to become a patient’s psychological kin, while maintaining a safe set of boundaries (“Darwinian Psychotherapy,” 2019; Giosan, 2020). This approach is in line with the suggestions of other evolutionary psychopathologists, who emphasize rapport between the therapist and patient (Troisi and McGuire, 2014: 34), question the efficacy of one-hour-per-week therapy sessions (Gilbert et  al., 2014: 19), or propose that depressed patients may even need ‘therapeutic cheerleading’ (Markowitz, 1994; Michels, 1997). While many evolutionary therapists argue for a stronger connection between the therapist and the depressed patient than the one advocated by other therapeutic paradigms, support for such an idea predates these recent developments in evolutionary psychotherapy. The early and fascinating work of Jerome Motto, who found that simply mailing personally signed ‘Caring Letters’ to people who had attempted suicide drastically reduced future suicide attempts, as people felt more



connected to the therapist communicating with them, illustrated the importance of therapeutic rapport (Motto, 1976). The ‘Caring Letters’ approach has been revised to include a form of intervention that essentially makes the therapist available almost continuously, and the results of this kin-like therapeutic relationship are promising. (For a detailed account of this project, including historical aspects, see James Cherkis’ (n.d.) excellent article in Huffington Post,

Evidence in Favor of CETD

for depression: Cognitive Therapy (CT; Beck et  al., 1979). A total of 97 depressed patients received 12 sessions of either (1) CETD or (2) CT. Baseline, mid-treatment, post-treatment, and three-month follow-up assessments were conducted. The CT group underwent classical cognitive interventions aimed at the correction of dysfunctional, automatic thoughts and beliefs hypothesized to be implicated in depressive symptoms. These interventions were paired with behavioral activation and positive reinforcements. The CETD group added s­pecific goals targeted at increasing fitness (see full protocol at Giosan, Cobeanu et al., 2014). Both interventions led to similar reductions in depressive symptomatology, as measured by the BDI-II (Beck et al., 1996), which were maintained at three-month follow-up. Although non-significant, the CETD group showed a consistent pattern of larger gains (greater decreases in BDI-II scores) during the treatment as well as post-treatment. Fewer CETD participants were classified as having moderate or severe depression over time, with between-group analyses showing trend differences at post-treatment. The results also showed that the CETD group experienced significantly greater reductions in behavioral inhibition/avoidance at both post-treatment and follow-up, compared with the CT group. Notably, CETD was also significantly superior to CT in increasing engagement in social and enjoyable activities at post-treatment. The study showed that in the participants receiving CETD, but not in those receiving CT, engagement in these activities was directly related to decreased symptoms of depression, suggesting that CETD leads to greater social reach, which, in turn, might translate into better therapeutic outcomes (Giosan, 2020; Giosan et  al., 2019; Giosan, Cobeanu, Wyka, et al., 2020).

In a case study examining the potential benefits of CETD, Giosan, Muresan et  al. (2014) used this protocol on a patient with an intake score of 22 on the BDI-II (Beck et al., 1996) and a diagnosis with depression made with the Structured Clinical Interview for the DSM (SCID) (First et  al., 1997), who presented deteriorating functioning (school performance) and quality of life following a recent break-up. An assessment of her perceived fitness with the EFS (Giosan et  al., 2018) revealed deficiencies in self-image, healthy eating habits, and physical activity. The patient was offered a cognitive-evolutionary conceptualization of her symptoms that centered on the distal causes of depression as well as on the dysfunctional cognitions that led to symptoms (Giosan, Muresan et al., 2014). The treatment focus was to engage the patient in the EFSsuggested fitness-increasing activities, while simultaneously challenging dysfunctional thinking. The treatment was successful, the patient achieving a ~68% reduction in the BDI-II (Beck et al., 1996) scores by session 8 (BDI-II = 7), therapeutic gains maintained at post-evaluation (BDI-II = 7) and follow-up (BDI-II = 13). A randomized, single-blinded active-­ controlled design (Giosan, Cobeanu, Wyka, et  al., 2020; Giosan, Cobeanu et  al., 2014) Personality Disorders expanded on this preliminary case study and contrasted the efficacy of CET for depression Personality disorders are typically perceived with one of the best validated interventions as difficult to address in therapy, with some


of them, such as borderline personality disorder, being especially prone to de facto demedicalization (Sulzer, 2015). The evolutionary scholars Prunetti et  al. (2013) developed a protocol for Cognitive Evolutionary Therapy specifically aimed at personality disorders (CET-PD). CET-PD is based on the Darwinian view that humans are driven by evolutionaryselected motivations and develop psychopathologies when their biologically relevant goals are not met. Thus, failures in patients with personality disorder are explained by the authors as resulting from disordered functioning of evolutionary-shaped social motives (Prunetti et al., 2013). The authors differentiate CET-PD from other treatments from which it borrows, such as Cognitive Therapy (Beck, 1976), Rational Emotive Therapy (Ellis and Dryden, 2007), and Dialectical Behavioral Therapy (Chapman, 2006).

Key Elements in CET-PD The key elements of CET-PD include: 1 Focus on restructuring schemas of self-with-others around biologically relevant needs (attachment, caregiving, social ranking, mating, cooperation). 2 Special focus on the therapeutic relationship. CET-PD places importance on the rapport between the therapist and patient, with special attention on discovering the specific motive that is active during the flow of therapy conversation. 3 Assessing interpersonal motivations during the therapeutic relationship (e.g., attachment or social rank). 4 Managing the therapeutic relationship to prevent/repair ruptures. 5 Making people aware of how dysfunctional schemas guide behaviors.

Evidence in Favor of CET-PD The authors examined the benefits of CET-PD in an intensive 20-hour weekly three-week residential treatment (both individual and group) of a wide range of severe personality disorders. Fifty-one patients with various


personality disorders were assessed at admission, discharge, and three-month follow-up and the outcome measures consisted of selfreported depression, anxiety, general symptoms, duration of inpatient admissions after the program was over, and continuation in an outpatient program. The results suggested that CET-PD was effective in reducing the level of depression and anxiety, with a change that was stable for trait anxiety. Obsessive symptoms, paranoid ideation, psychoses, and feelings of self-inadequacy and inferiority diminished. Overall, the results showed an improvement in psychopathology after release and in follow-up sessions, a decrease in the number of further hospital admissions, and an increased level of outpatient therapy attendance (Prunetti et al., 2013).

Potential Applications of Evolutionary Conceptualizations to Other Mental Conditions In the previous section, we reviewed the possible integration of evolutionary insights in psychoanalysis and analytical psychotherapy, and we summarized the results from controlled studies that examined the efficacy of evolutionary interventions for depression and personality disorders. In the next section, we briefly present, in a speculative manner that needs further testing in controlled trials, some potential applications of evolutionary conceptualizations to the treatment of other mental conditions.

Postpartum Depression Conceptualizing postpartum depression as an adapted response to unfavorable circumstances (e.g., child sickness, lack of resources or support) (Hagen, 1999), evolutionary mismatch (Crouch, 1999), or age (Bottino et  al., 2012) may make a patient suffering from it more likely to recover. A treatment aimed at increasing fitness (e.g., by focusing on resource



acquisition) may be better than correcting dysfunctional beliefs (‘I am a bad mother’). From an evolutionary perspective, cognitive techniques could be tried to increase the perceived benefits of having a child and reduce the perceived costs. Such a strategy might lead to a decrease in the severity of postpartum depression precisely because it addresses evolutionary causes. For instance, a young mother could understand that her symptoms do not reflect her incapacity as a mother, but, rather, a mechanism by which she is asking for help. Thus, the intervention could focus on coping mechanisms and problem-solving targeting the fundamental causes of the symptoms, addressing not only the depressive symptoms per se, but also the situation that led to them (decreased fitness).

Anxiety Disorders By distinguishing between situations in which anxiety is disabling (when medication can be useful) and those where anxiety may be adaptive, evolutionary theories can offer meaningful case conceptualizations that can help patients to accept these symptoms and possibly reduce impairment. For instance, a debilitating phobia of snakes might be accepted and dealt with better by a patient if it is explained to her that fear of snakes is an evolved fear which increased the likelihood of survival in ancestral times (Marks and Nesse, 1994) and that her extreme anxiety around such stimuli is not a brain disorder, but an evolved, normal mechanism that may be functioning in overdrive. Similarly, in Obsessive Compulsive Disorder, conceptualizing the symptoms as exacerbated mechanisms to facilitate reproduction and protect offspring (Feygin et  al., 2006) can lead to better acceptance of the symptoms, a key element in the recovery process (Chamberlain and Haaga, 2001). One of the most common forms of anxiety, social anxiety (SA), is particularly resistant to treatment, with only about half of

patients showing improvement, even when gold-standard treatments, such as CBT, are used (Loerinc et al., 2015). Conceptualizing SA as one of the poles (besides social dominance) necessary to maintain social order (Öhman, 1986), or as a vestigial response to social threat (Trower and Gilbert, 1989), may increase a patient’s acceptance of the symptoms. Moreover, evolutionary understandings of SA may serve as a guide in therapeutic decisions. For instance, in some cases, just treating symptoms (through gradual exposure, for instance) may not be enough, and a discussion about eliminating or modifying the circumstances that elicit symptoms may be in order (Brosnan et al., 2017). Providing patients with evolutionary explanations of phobic symptoms is not possible in all the cases, so only some patients will benefit from this kind of evolutionaryaided case conceptualization. This approach is suitable in the case of patients with fears of biologically relevant stimuli, such as heights, public speaking, dark, blood, or certain types of animals, who could benefit from logical distal explanations of the symptoms, and less so, if at all, in the case of patients presenting fears of evolutionaryirrelevant objects, such as a fear of cotton balls or certain colors. In other words, while evolutionary explanations of anxieties can be helpful in treatment, this does not mean a replacement of current explanations, which typically rely on either proximal causes or distant, but not evolutionary ones (e.g., childhood traumas). On the contrary, multi-layered explanations (evolutionary, developmental, proximal mechanisms) should be used, with evolutionary insights helping in the creation of a more comprehensive causal picture of the problems bothering a patient.

Dysmorphic Disorder Dysmorphic disorder is explained evolutionarily through one’s attempt to compare with


others and the avoidance of rejection or ridicule, which are linked to lower status and lower mate value (Veale and Gilbert, 2014). Understanding the context and functions of the behaviors associated with this condition can be critical for the success of an intervention, especially when the patient has aversive emotions, such as shame or rejection, which have not been properly processed (Veale and Gilbert, 2014). Cognitive behavioral techniques for treating this condition could be improved through the analysis of the functions and contexts in which the behaviors appear. This can be realized via multiple routes, such as (1) linking the body-related fears to fears of rejection or to emotionally charged memories; (2) rewriting of the narrative; (3) providing an evolutionary context that separates the symptoms from the feelings of shame and the affected person; or (4) the direct targeting of the feelings of shame and self-criticism and the development of social skills through compassion (Veale and Gilbert, 2014).

Post-Traumatic Stress Disorder (PTSD) Evolutionary hypotheses of PTSD center on evolved mechanisms of avoiding dangers (Silove, 1998; Wiedenmayer, 2004). Once a person has been exposed to a traumatic event, they will automatically learn to avoid that type of situation, thus increasing their survival chances. In some vulnerable individuals, this learning can be excessive or hard to stop. While validated evolutionary interventions for PTSD have yet to be reported, the reinterpretation of PTSD symptoms as produced by adaptations to protect an individual from future harm, mechanisms that are found in other species as well (Zanette et al., 2019), can help patients to better understand and accept the condition and may improve the therapeutic benefits offered by validated interventions for PTSD, such as Gradual Exposure Therapy. Furthermore, some authors have found a link between life history


and PTSD (Giosan and Wyka, 2009), which might lead to novel, reproductive strategiesbased intervention protocols in the future.

Eating Disorders Evolutionary explanations of eating disorders center on intrasexual competition (Li et  al., 2010) or on life-history strategy (Mehta et al., 2011). Such hypotheses can have clinical implications. As in the examples above, an understanding of the mechanisms that activate when we eat certain foods can be therapeutically helpful when the patient’s cognitions are addressed. In cognitive behavioral interventions, for instance, such explanations could facilitate the psychoeducational aspect of therapy and can also aid in the generation of alternative thoughts that are to replace the automatic, dysfunctional ones. Furthermore, the integration of evolutionary explanations of eating disorders in school curricula may put young people in a better position to understand human tendencies, which can then act as an important protective factor.

Substance Abuse Evolutionary explanations of substance dependence or abuse revolve around the fact that people have consumed psychoactive substances over our recent and ancestral history (Dudley, 2004; Sullivan and Hagen, 2002), with some authors arguing that drug consumption can be associated with fitness benefits (Kirillova et al., 2008). The mismatch between the past benefits associated with such behaviors and the easy access to such substances in our modern world can make some predisposed individuals consume them more, slowly driving them into addiction. Understanding the distal explanations of substance consumption might be useful in therapy, especially in the conceptualization phase of an intervention. In substance abuse, patients typically feel guilt and shame



(McGaffin et al., 2013). Evolutionary insights integrated into therapy could potentially reduce such reactions, deepening positive therapeutic outcomes.

APPLICATIONS OF EVOLUTIONARY PSYCHOLOGY IN COUPLES THERAPY No section on the applications of evolutionary psychology to counseling and psychotherapy would be complete without a discussion about the many helpful elements that evolutionary psychology can bring to couples therapy. Since evolutionary psychology examines the processes that have helped our ancestors to survive and reproduce, it is evident that it can bring insights into problems typically encountered in couples, such as sexual incompatibilities, emotional and/or sexual infidelity, trust, gender stereotyping, or control. An important class of results generated by evolutionary psychology is that, when it comes to mating, men and women are hardwired somewhat differently and their strategies to reach a common biological goal – ­reproduction – can, at times, be quite different, which can be a source of conflict, potentially leading to the dissolution of the couple. Studies on heterosexual mating preferences have documented gender commonalities, such as dependability, faithfulness, and kindness (Barber, 1995; Buss, 1989; Buss et  al., 1990) but also differences, in that women are more interested in earning capacity, while men are more interested in physical beauty and health cues (e.g., skin smoothness, waist-to-hip ratio) of their partners, with overlapping bell curves in such tendencies (Buss et al., 1990; Zhang et al., 2018). Because women require a minimum of nine months investment (pregnancy) in order to be successful at reproduction, and because they cannot have nearly as many children as a man can theoretically have, they have evolved to be the choosier sex (Hatfield

and Sprecher, 2016). In contrast, since men can impregnate a large number of women in a short period of time, they have evolved stronger preferences for pursuing short-term mating opportunities (Schmitt et  al., 2003). Studies show a gender difference favoring men in the number of sexual partners (Todd et  al., 2009) and other research has shown differences in sexual fantasies, with men being more likely to fantasize about sexual variety (Ellis and Symons, 1990). Other studies show that men are more permissive about casual sex and have a higher incidence of masturbation (Oliver and Hyde, 1993) and are more likely to be consumers of pornography (Hald, 2006), an element that has been linked to couple dissatisfaction (Stewart and Szymanski, 2012). Males’ stronger desire for multiple sexual partners comes with a substantial threat to marriage, especially since men are sometimes willing to leave their children behind for the pursuit of new relationships. Indeed, some authors have argued that men live in a state of ‘mild torment’ that stems from their propensity for sexual variety (Singer, 1985a, 1985b). It is evident that such deeply engrained feelings can have catastrophic consequences on a marriage or long-term relationship. Therapists must be aware of such mechanisms and address them in therapy in a non-judgmental manner, as treating these tendencies as a ‘disease’ or lack of character can destroy the therapeutic relationship. In addressing such issues, therapists must also be careful about balancing male needs and female needs. For instance, some authors have stated that promoting commitment in therapy may mean, in fact, promoting female reproductive interests at the expense of the male reproductive interests (Glantz and Moehl, 2000). Such realities can make men feel they are not understood, which can alter the therapeutic relationship. Offering explanations of the distal causes of the gender differences in sexual preferences is usually a good strategy to navigate through these issues in therapy and sometimes helping a man deal with his


conflicts about commitment is better done in one-person therapy (Gilbert et al., 2014). Men’s stronger preferences for sexual variety are also linked to the so-called Coolidge effect, which is the sexual interest in a new female, even when the male has reached sexual satiation with his existing partner (Buss, 1994; Dewsbury, 1981; Glantz and Pearce, 1989). In humans, this phenomenon translates into greater interest for sex outside the pair and reduced interest for sex within the pair. This sexual boredom, affecting men and, also, women, but for different reasons, can undermine a relationship. Therapists who understand that sexual boredom is not reversible and that the passion of youth cannot be restored are in a much better position to help a couple in need of counseling (Glantz and Moehl, 2000). Moreover, since women, but not men, are always certain that their babies are theirs, men are faced with the uncertainty of paternity, which has led to gender differences in the experience of feelings of jealousy. Thus, women appear to be more affected by their partners’ emotional infidelity, whereas men are more affected by their partners’ sexual infidelity (Buss et al., 1992; Daly et al., 1982). This, in turn, makes women less likely to forgive emotional infidelity, and men less likely to forgive sexual infidelity (Shackelford et  al., 2002). The issue of jealousy appears often in couples therapy and in many a case one of the partners adamantly accuses the other of ‘destroying the relationship’ by being too jealous. Indeed, strong feelings of jealousy can lead to controlling behaviors (e.g., controlling the partner’s social media accounts), verbal or physical violence, suspiciousness, isolation of the partner from family and friends, and lack of trust, which can undermine a relationship until its complete dissolution. Clinicians would be welladvised to use evolutionary insights in such situations and explain to their clients that jealousy is, at its most fundamental level, a universal mate-guarding strategy (Buss, 2000), which has helped us pass on our genes to the next generations, and that, barring


extreme manifestations, such as delusions, it is a ­normal evolved mechanism that we should not be ashamed of. Reinterpretation of jealousy as an adaptation that facilitates mate retention may aid in the therapeutic process. Understanding the important differences in sexual preferences and tendencies between men and women can help a couples therapist’s attempts to heal a fractured relationship. Some authors have argued that some of the fundamental principles of therapy, such as communication and sharing feelings, fail to take into account core male needs (Glantz and Moehl, 2000), potentially leading to the inefficiency of the interventions. Indeed, men’s and women’s relating styles are different (Winstead et al., 1997), which may make the former harder to engage in psychotherapy. Furthermore, the tabula rasa paradigm advocated by the Social Science Standard Model assumes no innate gender differences, which may lead to unreasonable therapeutic requests of males to reveal inner emotions and insecurities (Shem and Surrey, 1998), further damaging a potentially already fragile therapeutic relationship. Let’s not forget that studies have shown that women prefer confident men, who are able to protect their partners from other men (Buss, 1989). This can and will make a man reluctant to display signals of weakness and subordination both in front of his partner and in front of the therapist. Clinicians who understand these nuances well are in a better position to establish rapport – critical for good outcomes – with a male patient in couples therapy. For instance, since status is often a crucial factor for men, acknowledging it or working to increase it can be an effective therapeutic strategy (Glantz and Moehl, 2000). Similarly, framing interventions in concrete economic terms (costs/benefits/advantages), as opposed to the more vague ‘better’, can lead to positive therapeutic outcomes (Glantz and Moehl, 2000). Furthermore, given the fact that men are less likely to disclose emotions and feelings, encouraging communication and deep disclosure, especially about weaknesses, may be counter-productive in some cases and



outright destructive when the disclosure might reveal profound couple incompatibilities, such as sexual (Glantz and Moehl, 2000). When the issue of misuse of power, such as anger directed toward family members, comes up in therapy, some clinicians have argued that this can lead to shaming and the activation of self-defense mechanisms in male patients, and that reframing, in the sense of explaining what the function of competition among males is, may be a better therapeutic strategy, with the important observation that the therapist should not recommend that a man simply give in to his partner (Glantz and Moehl, 2000).

CRITICISM OF EVOLUTIONARY INTERVENTIONS In the previous sections, we succinctly presented some of the recent progress in the field of evolutionary interventions for certain mental disorders as well as possible applications of evolutionary insights in couples therapy. Despite these promising developments, we must note the fact that the evolutionary hypotheses of mental disorders are, for the most part, speculative and do not have strong empirical support yet. Generally, there is rivalry between hypotheses, with little movement toward consensus, as well as slow adoption by practitioners. In addition, while some of the progress made in evolutionary randomized clinical trials is noteworthy, it is very difficult to draw incontrovertible conclusions from medical-style randomized clinical trials in this field, except perhaps when they can be pooled in bulk as meta-analyses. Even then, it is hard to adjust for publication bias, unaccounted placebo effects, statistical phenomena, and other confounds (Westen et al., 2004). Another point of caution in evaluating the merits of evolutionary interventions is the fact that meta-analyses generally show that no particular theoretical approach performs

markedly better than the rest (Cuijpers et al., 2008; Miller et  al., 2008; Smith and Glass, 1977), and there is no reason to believe that evolutionary therapies are any different. Indeed, the most influential factors apparently common to virtually all schools are the therapist’s technique and the rapport between client and therapist (Budge and Wampold, 2015). Since some evolutionary therapies (e.g., CETD, described earlier in this chapter), place, among others, a premium on the client/therapist relationship, further research should examine whether this emphasis might be differentially associated with therapeutic success. Last, but not least, the evolutionary interventions presented in this section have generally addressed specific mental disorders, but there is debate in the field whether they exist as ‘real’ natural conditions to begin with (First and Pincus, 2009). As such, more cross-diagnostic evolutionary interventions should be attempted and tested, since a therapy developed for a certain condition (e.g., depression) may well be efficient for a different one (e.g., anxiety or self-harm) (Wampold and Imel, 2015).

SUMMARY This chapter briefly presented some of the recent advances in clinical applications of evolutionary psychology. Progress has recently been made in incorporating evolutionary insights into psychological interventions for depression and personality disorders, with several randomized clinical trials supporting such approaches already completed. Treatments of other psychological problems, such as anxiety, substance abuse, and eating disorders, might also benefit from the inclusion of evolutionary understandings of symptoms, although such assumptions need to be tested in future controlled clinical studies. By offering distal explanations of sexual preferences, evolutionary psychology may


also aid substantially in couples therapy. Issues like jealousy or infidelity can be better dealt with in couples therapy when they are interpreted through evolutionary lenses, potentially leading to better therapeutic alliance and outcomes. Despite these recent developments, much more research on the merits of such approaches should be conducted, as the unclear role of common factors in evolutionary therapies, the speculative nature of many evolutionary hypotheses of mental disorders, and the lack of controlled evolutionary trials on cross-diagnostic symptoms make it hard to draw definitive conclusions about the efficacy of such efforts.

Note 1  The ABC model proposes that emotions (C) are not caused by external events (A), but by beliefs (B) and, in particular, irrational beliefs (IB) (Sarracino et  al., 2017). The ABC model can also be referred to as the ‘ABCDE’ model, where D stands for the disputation of beliefs and E stands for new effect, the result of holding healthier beliefs (Jorn, 2016).

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2 Evolutionary Psychology and Psychiatry Riadh Abed and Paul St John-Smith

INTRODUCTION Psychiatry is a branch of medicine that deals with mental disorders that manifest themselves through disturbances in cognition, emotions, and behaviour. Like the rest of medicine but unlike psychology (with the exception of clinical psychology), psychiatry is an interventionist discipline that aims to modify the signs and symptoms of disorder in order to reduce/ relieve individual distress and reduce risk (harm) to the individual and/or others. The contemporary failure of psychiatry to make significant progress in understanding the aetiology of mental disorders has been characterized as a ‘crisis’ by leading evolutionists (Brune et al., 2012); a fact that has also been acknowledged in an article in ‘Science’ that stated that there have been no major breakthroughs in the treatment of schizophrenia for 50 years nor in the treatment of depression for 20 years (Akil et al., 2010). Mainstream psychiatry, like the rest of medicine, focuses on proximate causation

and favours mechanistic explanations of disease and disorder. However, unlike medicine where human physiology provides clear reference points for normal functioning, psychiatry has attempted to identify disorder and dysfunction without a coherent theory of normal human psychology (Nesse, 2019). We argue in this chapter that evolutionary psychology and evolutionary biology can serve as a vital basic science for psychiatry. Despite the publication of notable evolutionary psychiatry texts over the last couple of decades as well as numerous scholarly articles in peer-reviewed journals, evolutionary thinking has remained underappreciated by mainstream psychiatry (e.g. Brune, 2015; Del Giudice, 2018; McGuire and Troisi, 1998; Nesse, 2019; Stevens and Price, 2000a). Although a pluralistic and multi-level approach to causality in mental health remains essential (Kendler, 2008), the current pluralism is unconstrained and lacks any recognizable framework (Abed, 2000). While it is recognized that all mental phenomena are mediated by physical events


in the brain, the phenotypic end-products of interest to psychiatry cannot be understood by examining the behaviour of neurons alone (a situation compared to trying to understand the mechanics of bird flight through the study of feathers (Marr, 1982)). We propose evolution as being ideally placed to guide psychiatrists in determining what the phenotypic end-products of neurobiological systems constitute. Such evolutionary emphasis on function can provide the scientific basis for expanding the concept of the biological to encompass the psychological, social, and cultural domains (Abed and St John-Smith, 2016). Hence, in contrast with mainstream biological psychiatry’s narrow ‘decontextualized’ view of mental disorder as brain disorder (Andreasen, 1984), evolutionists consider the environmental context to be vital in determining the existence of mental disorder (Nesse, 2019).

THE CONCEPT OF MENTAL DISORDER Despite its widespread adoption within psychiatry and medicine generally, the concept of disorder has been difficult to define with precision (Nesse, 2001). One influential evolutionary proposal is that mental disorder represents a hybrid concept, with a biological and a socio-cultural component; a ‘harmful dysfunction’ (HD) (Wakefield, 1992). Accordingly, the biological component of any disorder is the failure of a biological mechanism to perform its evolved function, and the value-laden component identifies that the dysfunction inflicts harm or damage on the affected individual as judged by socio-cultural standards. Although Wakefield’s HD concept has been subject to criticism (e.g. Bolton, 2007; Fulford and Thornton, 2007), it is acknowledged to be a significant improvement on existing formulations (e.g. First, 2007; Nesse, 2007). However, while the biological criterion of the failure of a system to perform its evolved function is intellectually


appealing, having considerable face validity, problems with its clinical utility linger because our understanding of the function of the neurobiological systems involved in mental disorder remains poor (First, 2007). In addition, whereas the emphasis on context is acknowledged to be important or even vital in determining the existence of mental disorder (Nesse, 2007), this potentially reduces the diagnostic inter-rater reliability subsequent to the increased scope of subjective judgement, generating concern for the authors of official classification systems such as the DSM-5 (American Psychiatric Association, 2013). Hence, while the DSM-5 accepts mental disorders necessarily involve internal dysfunction and that this produces harm and/or distress, it leaves the term ‘dysfunction’ undefined. Furthermore, whereas context is considered in a range of conditions, it is excluded in others. For example, in the DSM-5, unlike its predecessors, low mood lasting longer than two weeks can now be diagnosed as major depressive disorder (MDD) following a major bereavement (Kavan and Barone, 2014). Del Giudice (2018) submits that a number of facets must be recognized to avoid common errors in interpreting Wakefield’s HD concept, including the fact that dysfunctions can arise from a number of different causes, both internal and external; that the concept of dysfunction is fuzzy; and that systems can have degrees of functionality where the line of demarcation between function and dysfunction is unclear. While there are undoubted benefits from an evolutionary analysis of the concept of mental disorder, we support Troisi’s (2015) conclusion that evolutionary biology alone does not resolve the central question of what should (and should not) be categorized as a mental disorder, as ethical, health, and social policy considerations lie outside the remit of evolutionary science. In other words, it is important not only to appreciate how evolutionary biology can help advance our understanding of mental disorder but also to understand its limits.



THE REMIT OF PSYCHIATRY In addition to the DSM-5, the other major classification system of mental disorders in clinical use throughout most of the world, outside the United States, is the ICD-10 issued by the World Health Organization (WHO, 1992). Both systems endeavour to follow an atheoretical approach to the definition and differentiation of mental disorder and, with the exception of organic mental disorders, base their diagnostic categories broadly on symptom clusters and duration. Context is acknowledged in some instances. The ICD-10 definition of mental disorder, being more succinct than that of the DSM, omits the assumption of an internal dysfunction, and proceeds as follows: ‘a clinically recognizable set of symptoms or behaviours associated in most cases with distress and with interference with personal functioning’ (WHO, 1992: 11). Their main categories of adult mental disorder comprise organic mental disorders, mental disorders secondary to psychoactive substance use, schizophrenia and related disorders, mood disorders, anxiety and stressrelated disorders, behavioural syndromes associated with physiological disturbances, and personality and other behaviour disorders. Other chapters deal with mental retardation, developmental disorders, and mental disorders of childhood and adolescence. Remarkably, given that both the ICD and DSM are systems based on the consensus of committees, these categorical domains continue to demarcate effectively the current boundaries of psychiatric practice (Nesse and Stein, 2012). Nevertheless, criticism remains directed against both systems for increasing reliability at the expense of validity (Insel, 2013). The National Institute of Mental Health in the United States, in an attempt to overcome these shortcomings, proposed the Research Diagnostic Criteria (RDoC). The four principles used to formulate the RDoC system were explained as follows (Insel, 2013): • A diagnostic approach based on the biology as well as the symptoms must not be constrained by the current DSM categories;

• Mental disorders are biological disorders involving brain circuits that implicate specific domains of cognition, emotion, or behaviour; • Each level of analysis needs to be understood across a dimension of function; and • Mapping the cognitive, circuit, and genetic aspects of mental disorders will yield new and better targets for treatment.

The RDoC approach is rooted in experimental neuroscience and lists five domains: positive valance systems, negative valence systems, cognitive systems, systems for social processes, and arousal and regulatory systems. Each system has a number of constructs and these are investigated using a number of units of analysis ranging from the molecular level to individual behaviour. The RDoC has been characterized as a bottom-up approach to the classification of mental disorders, grounded in the latest research in biological sciences that can cut across existing DSM/ICD categories (Del Giudice, 2018). However, critics have raised concerns regarding the neglect of context (above and beyond the DSM or ICD) and neglect of the role of evolution (Wakefield, 2014).

EVOLUTION AND CAUSALITY The application of evolutionary thinking to psychiatry commences by considering some general principles that apply to all biological phenomena. Tinbergen (1963) proposed that a complete understanding of any biological trait or system involves understanding its mechanism, developmental history (collectively referred to as proximate causes), phylogenetic history, and function (referred to as ultimate or evolutionary causes) (Table 2.1). These are referred to as Tinbergen’s four questions and all four apply simultaneously to biological phenomena (Gluckman et  al., 2009). It is acknowledged that unlike proximate causation which can directly lead to therapeutic interventions, understanding evolutionary or ultimate causation is somewhat



Table 2.1  Tinbergen’s four questions Proximate causation Evolutionary or ultimate causation

Developmental/historical 1. Ontogeny: how does the trait develop during the lifetime of the organism? 3. Phylogeny: what is the phylogenetic history of the trait?

Characteristics of trait/system 2. Mechanism: how does it work? 4. Adaptive function: How has the trait or system contributed to the organism’s inclusive fitness in its natural environment?

Source: Adapted from Nesse (2013).

removed from direct clinical applications but is no less important. Neglecting the question of function (ultimate causation) runs the risk of psychiatrists inadvertently altering psychological functioning through their interventions to relieve distressing but adaptive states, leading to potentially negative consequences for some patients. It can also lead us to construct defective models of how psychopathology arises. Focusing exclusively on the proximate is akin to a technician’s view of a machine, whereas considering ultimate causation as well is more like an engineer’s view (Nesse, 2019). Hence, it may seem adequate for a busy clinician to simply recognize the existence of depression or anxiety in a given patient and to dispense standard advice and treatment accordingly. However, a clinician who also understands why we have such emotions in the first place and how emotional systems interact with people’s current lives is likely to have a deeper understanding of the patient’s emotional problems and is able to take greater account of the patient’s circumstances that may be contributing to their current state. It also has the potential for influencing the research agenda through testing hypotheses regarding what the normal function is of the system that is giving rise to psychopathology; a question that is seldom asked by mainstream psychiatry (Brune, 2015).

CAUSAL PATHWAYS FOR THE PERSISTENCE OF DISEASE AND DISORDER It is obligatory to recognize that selection shapes vulnerability to disease and disorder

and not disorders themselves (Nesse, 2019). This applies throughout medicine, including psychiatry, and stems primarily from the demonstration that bodies and brains are a bundle of adaptations shaped by selection over thousands of generations to increase reproductive success and not good health, happiness, or longevity. The answer to the pivotal conundrum of why evolution has left humans so vulnerable to disease and disorder has itself been evolving ever since it was first posed by the founders of modern evolutionary medicine (Nesse and Williams, 1994). Accordingly, pathways by which evolutionary processes can lead to the existence and persistence of disease or disorder have been proposed (Box 2.1). These causal pathways are not mutually exclusive and several may be implicated concurrently or sequentially in the origin of mental disorders. They represent a list of ultimate causes of our vulnerability to mental disorder. Examples of many of these causal pathways will be given in the sections below. These evolutionary explanations for vulnerability to disorder are based on the recognition that selection is unable to eliminate all harmful mutations, and can be too slow to respond to rapidly changing environments, creating states of evolutionary mismatch (Del Giudice, 2018). This concept of ‘mismatch’ is crucial for understanding and explaining the existence of many diseases and disorders of modernity such as obesity, metabolic syndrome, Type 2 diabetes, eating disorders, and many others. Evolutionary mismatch occurs when the environment changes too rapidly for selection to be able to track it, resulting in residual traits that are no longer suited to the



BOX 2.1 Pathways for the persistence of disease and disorder  (Adapted from Gluckman et  al. (2009) and Crespi (2016); for definition of terms see glossary: www.rcpsych. pdf?sfvrsn=707dd6b_2)

• • • • • • • • • • • •

Mismatch Life history factors Overactive defence mechanisms Co-evolutionary considerations: consequences of the arms race against pathogens Constraints imposed by evolutionary history Trade-offs Sexual selection and its consequences Balancing selection: maintaining an allele that raises disease risk Demographic history and its consequences Selection favours reproductive success at the expense of health Deleterious alleles Extremes of adaptations

new environment. Developmental mismatch arises when circumstances alter radically during an individual’s lifetime. For example, moving from a state of impoverishment during early development to a state of affluence in adult life can increase the risk of cardiovascular disease, Type 2 diabetes, and metabolic syndrome (Gluckman and Hanson, 2006). Furthermore, the extreme ends of functional adaptations can become maladaptive e.g. when adaptive personality traits are magnified (Trull and Widiger, 2013). Additionally, over-activation of useful emotional defences (mood states and anxiety) can result in harmful outcomes, leading to defence activation disorders (Del Giudice, 2018). It is important to understand that selection necessitates trade-offs. Increasing one trait is often at the expense of worsening performance of another. For example, increasing resistance to infections increases the risk of autoimmune diseases. Improving nutritional conservation increases the risk of obesity. Trade-offs are also involved in life history strategies. Life history theory (LHT) deals with species-typical solutions for problems associated with survival and reproduction that change over an individual’s lifespan (Brune,

2015). Hence, LHT provides a framework for understanding how organisms allocate time and energy in achieving core biosocial goals across the lifespan. Life history strategies involve a series of trade-offs that shape important biological developments including the timing of sexual maturity, the number and quality of offspring, and the length of lifespan (Stearns, 1992). The application of LHT demonstrates that the trade-offs yield a spectrum of life history strategies where the trade-offs include somatic versus reproductive effort, present versus the future, and quality versus quantity of offspring (Figure 2.1). The ‘fast’ end of the spectrum is characterized by a shorter lifespan, faster growth, earlier maturation and reproduction, and a larger number of offspring, while those at the slow end of the life history spectrum show the opposite characteristics (Del Giudice, 2018). Differences in life history strategies are partly under genetic control but it appears that the nature and quality of the individual’s early environment may also be important (Belsky et  al., 1991; Ellis et  al., 2011) (see Barbaro et  al., 2016 for a different perspective). This renders LHT important for the understanding



Lifetime Energy Investment

Reproductive Effort

Somatic Effort (Slower)


Mating Effort (Faster)

Parental Effort (Slower)

Figure 2.1  Life history strategy trade-offs

of vulnerability to mental disorders (Brune, 2015; Del Giudice, 2018) (see later section ‘Evolutionary Models of Mental Disorders’). One major insight that follows from understanding the evolutionary causal pathways for the persistence of disease and disorder is the recognition that mental distress can arise from functional systems. Hence, an evolutionary taxonomy of treatable (undesirable) mental health conditions goes beyond harmful dysfunctions (Tooby and Cosmides, 1999). Undesirable conditions may result from different scenarios as summarized below (Del Giudice, 2018): • Undesirable mental health conditions can either arise from: {{ harmful dysfunctions (system breakdowns); or {{ functional mechanisms, which can be either: • maladaptive states at population level (e.g. evolutionary mismatch), or are: • currently adaptive, but outcomes may vary, resulting in: {{ maladaptive outcomes at the individual level (e.g. overactive defences, developmental mismatches), or: {{ adaptive outcomes at the individual level even if considered harmful by others (e.g. antisocial personality/psychopathy).

Hence, an evolutionary analysis provides a theoretical framework that enables us to distinguish states of mental distress and mental disorder that arise from functional or dysfunctional systems, and also provides a more effective way of understanding the role of environmental context.

GENETICS AND HERITABLE RISKS OF MENTAL DISORDERS Taking an evolutionary perspective is tantamount to turning genetics on its head. Hence, whereas a non-evolutionary view may consider specific DNA sequences as the primary biological cause of a given trait, an evolutionary approach seeks to understand the selection pressures over evolutionary history that led to the retention of these genes. So, evolutionary views consider environmental influences at two distinct levels, first over evolutionary history (leading to the shaping of adaptations) and, second, the ontogenic effects of the environment during the individual’s lifetime. Mental disorders require a degree of heritability, and hence some genetic basis,



before becoming candidates for evolutionary explanations. Remarkably, 55% of all coding genes in humans are expressed in the brain. This renders the brain a prime target for mutations and evolutionary changes (Brune, 2015). After considering heterogeneity and uncertainty, psychiatric disorders demonstrate a degree of heritability suggesting a moderate degree of heritable risk. For example, 90% of trait variation for autism can be accounted for with genetics; bipolar disorder, 85%; schizophrenia, 81%; unipolar depression, 37% (Kendler, 2001). Similarly, heritability estimates for anxiety disorders range from 30% to 45% (Hettema et  al., 2001). Family studies (including twin and adoption studies) provide consistent evidence that genetic factors are involved in the presentation of these syndromes (Kendler and Eaves, 2005). Two types of heterogeneity have been identified in association with psychiatric genetics: causal and clinical. Causal heterogeneity refers to two or more causes independently inducing the same clinical syndrome. Clinical heterogeneity occurs when a single cause leads to multiple clinical syndromes (Tsuang et al., 2003). Natural selection does not directly select for genes that cause disease or disorder, so other explanations for their persistence must be considered. Accordingly, alongside any degree of heritability psychiatrists should ask: ‘Why does this mental disorder exist and persist?’ Mental disorders may be actively maintained through a number of evolutionary processes. These include: A) despite natural selection e.g. (i) mutation-selection balance, (ii) ancestral neutrality; and B) because of natural selection, (i) balancing selection, (ii) antagonistic pleiotropy, (iii) stabilizing selection on continuous traits, (iv) alternating selection, and (v) functioning adaptations. These categories are not mutually exclusive, and there may be multiple mechanisms maintaining some disorders in the population (Durisko et al., 2016).

Differential Susceptibility Research has demonstrated that people possessing at least one s-allele of the serotonin transporter gene HTTLPR incur increased risk of developing depression when facing adverse events. However, the same variation is linked to superior cognitive performance in several domains and increases social conformity (Homberg and Lesch, 2011). A balanced polymorphism also explains the frequency of a particular SNP in the general population, and why it has not been selected against. Beyond this important concept, evolutionary theory has aided in developing the idea that a particular SNP such as the s-allele of the 5-HTTLPR not only confers heightened risk for depression under unfavourable conditions, but lower risk for depression under favourable environmental conditions such as parental warmth and emotional availability during important developmental stages. This phenomenon is referred to as ‘differential susceptibility’ (Belsky, 1997; Pluess and Belsky, 2010), where phenotypic plasticity occurs in response to early environmental conditions, and differs radically from genetically mediated resilience which involves unresponsiveness to environmental conditions. The specific phenomenon of differential response to positive experiences is referred to as ‘vantage sensitivity’; a concept that shows promise in assessing the likelihood of responding to psychological interventions (de Villiers et al., 2018). This example serves as evidence against simple genetic determinism and also provides an indication that aspiring to alter genes alone to treat disorders may not be in an individual’s interests as differing circumstances alter the harmfulness or benefits of such a gene.

Mutation Load and Mental Disorder Mutation load has been implicated in the causation of some mental disorders (Keller and Miller, 2006), referring to de novo


germ-line mutations passed on from parents, rather than somatic mutations. Because ova go through far fewer replications than sperm, paternal age at conception was suspected as the primary source of de novo mutations (Crow, 2000). Paternal age is associated with increased risk of mental disorders generally (Hare and Moran, 1979). Mutation load is believed to play a significant role in the causation of schizophrenia and this is especially the case in childhood onset (Ahn et  al., 2014; Caplan, 2016) (for a contrary view, see Ek et al., 2014). For autistic-spectrum disorder (ASD), mutation load was more significant in females and in severe cases (Jacquemont et al., 2014). The risk of attention deficit hyperactivity disorder (ADHD) has been found to be positively related to paternal age (Chudal et  al., 2015; D’Onofrio et al., 2014; Russell et al., 2014, 2015). In depression, no significant relationship has been found with paternal age but there is increased risk with maternal age, suggesting prenatal stress as a factor (Del Giudice, 2018). In eating disorders and obsessive– compulsive disorder (OCD), the relationship with mutation load remains inconclusive (Del Giudice, 2018). Conversely, young paternal and maternal age is also related to the risk of a range of mental disorders in offspring. This, however, is not related to mutation load but rather to heritability of fast life history strategies, as fast life history is associated with early parenthood in both men and women and predicts a greater risk of fast life history spectrum disorders in the offspring of young parents (most notably ADHD and schizophrenia spectrum disorders) (see ‘Evolutionary Models of Mental Disorders’ section below).

Genomic Imprinting and Mental Disorder In diploid species such as humans, each autosomal gene is represented by two alleles, with one copy inherited from each parent.


Usually in autosomal genes, expression occurs from both alleles. However, in a very small fraction, one of the two alleles is switched off or ‘imprinted’, which may have significant effects on behaviour, as many are expressed in the brain (Wilkinson et  al., 2007). Genomic imprinting represents a form of intragenomic conflict, whereby different alleles and loci express the fitness interest of one of the parents (Crespi, 2019). Intragenomic conflict arises from the asymmetry in the confidence regarding parental relatedness to offspring between the sexes. The conjecture is that paternally expressed (maternally imprinted) genes in an individual exert phenotypic effects that increase fitness-related demands imposed by offspring upon the mother, due to the lower probability of relatedness of paternal genes (than maternal genes) within a given brood. This is thought to be because mothers are always related to offspring by 50%, while the offspring of a given female can have different fathers (Crespi, 2019). Contrastingly, maternally expressed (paternally imprinted) genes are predicted to exert the reverse effect, namely, lower demands imposed on mothers. Hence, sometimes incremental investment will be favoured by paternal genes but resisted by maternal genes (Haig, 2014). Intriguingly, maternal gene imprinting (paternal expression) may be one cause for the underdevelopment of the ‘social brain’, generating a higher risk of ASD, whereas the paternal gene imprinting (maternal gene expression) may predispose to hyper-­development of the social brain and increased risk of schizophrenia and related psychosis (Crespi, 2019) (see section ‘Schizophrenia Spectrum Disorders (SSDs)’, para. E, below).

EVOLUTIONARY MODELS OF MENTAL DISORDERS In contrast to the avowedly atheoretical approach of the DSM/ICD systems described above and the bottom-up biological approach



of the RDoC, evolutionary frameworks for the classification of mental disorder are top-down systems with explicit theoretical assumptions. They tend to utilize high-level organizing principles derived from evolutionary insights regarding the adaptive significance of various brain systems. Such a top-down approach remains compatible with a range of existing non-evolutionary approaches (Del Giudice, 2018). According to Del Giudice (2018), any coherent framework for mental disorder (evolutionary or otherwise) should meet four main challenges: explain patterns of co-morbidity; address heterogeneity within diagnostic categories; bridge psychopathology with individual differences; and account for developmental features of mental disorders including life course trajectories. The evolutionary framework proposed by Del Giudice (2018) based on LHT is more comprehensive and wideranging than others such as the diametric model of ASD and psychosis (Crespi, 2019; ‘Mutation Load and Mental Disorder’ section, above) and the externalizing–internalizing model (Martel, 2013). Del Giudice (2018) suggests that his proposed framework meets all four challenges and offers an alternative to the existing trans-diagnostic taxonomies of mental disorders such as the RDoC. The most recent version of this framework has been expanded to include a primary dimension of fast–slow life history strategy supplemented by a secondary dimension of defence-activation and hence the model has been dubbed the FSD model (Del Giudice, 2018). It is based on a core proposition, namely that the risk of developing a mental disorder depends on a pattern of individual differences that can be understood as manifestations of alternative life history strategies. Hence, moving along the fast–slow life history dimension will increase the risk of certain mental disorders and reduce the risk of others e.g. fast life history strategies increase the risk of psychosis while reducing the risk of autism, and vice versa. The FSD model generates three clusters of disorders:

F-type, S-Type, and D-type. The system is currently aimed at use by researchers rather than clinicians and it does not currently accommodate organic mental disorders or mental handicap.

EVOLUTIONARY THINKING ABOUT SELECTED PSYCHIATRIC DISORDERS It is important to note that due to the dual problems of heterogeneity and co-morbidity that beset current classification systems (Del Giudice, 2018), none of the evolutionary theories discussed in this section can account for the full range of the conditions they purport to explain. Heterogeneity in this context refers to the likelihood that most common mental disorders are a collection of disparate conditions that share certain clinical features but may differ in their causation.

Depression Sadness is universally recognized as the normal emotional response to loss, setbacks, and reversals in life (Horowitz and Wakefield, 2007). Unlike anxiety (a state of vigilance designed to detect and deal with risk and prevent/reduce harm), there is no consensus on the function(s) of sadness. Depressive disorders are marked by a severe negative mood with an inability to experience pleasure. In addition to low mood or anhedonia lasting a minimum of two weeks the DSM-5 requires the existence of four or more symptoms (loss or gain in weight, insomnia or hypersomnia, agitation or retardation, fatigue/loss of energy, feelings of worthlessness or inappropriate guilt, poor concentration or indecisiveness, and thoughts of death and suicide) for a diagnosis of major depressive disorder (MDD) (American Psychiatric Association, 2013). Although the DSM-5 treats MDD as a unitary condition, the application of its criteria allows for a wide variety of combinations where


individual patients can share few or even no symptoms (Fried and Nesse, 2015). Although many accept that depressive disorders are a highly heterogeneous collection of conditions (Akiskal and McKinney, 1975; Brune, 2015; Gilbert, 2006; Rantala et  al., 2018), most evolutionary theories of depression still treat it as if it was a unitary condition with a single explanation. Depression remains one of the most common mental disorders in clinical practice, with a lifetime risk in the US population that exceeds 15% (Blazer et al., 1994) and striking at increasingly younger ages (Rottenberg, 2014). The increase in prevalence of depression in modern societies most probably results from evolutionary mismatch (Brune, 2015; Rantala et  al., 2018; Rottenberg, 2014). As in most other defence activation disorders, depression has a higher prevalence in females with an overall F:M ratio of around 2:1. The higher female risk is contributed to by higher levels of neuroticism, sensitivity to social rejection, and interpersonal stressors (Del Giudice, 2018). Interestingly, and unlike most other mental disorders such as schizophrenia, autism, and anorexia nervosa, patients with depression show rates of reproductive success very close to that of the general population, with males at 90% and females at 100%

(Power et  al., 2013). Depression occurs at both ends of the fast–slow life history continuum, with a fast life history subgroup of both males and females having early puberty and a slow life history subgroup (mainly males) having late puberty (Del Giudice, 2018). Hence, depression is not so much a slow life history strategy as a ‘slowing down’ strategy that can occur across the life history strategy spectrum (Brune, 2015). Although there is lack of agreement on the precise function of low mood, most evolutionists agree that the capacity for low mood has been shaped by selection because of its contribution to inclusive fitness in the ancestral environment. Disagreements between evolutionists arise where some consider the extremes or persistence of low mood as maladaptive and/or dysfunctional, while others consider the whole range of low mood including the extremes of depression as adaptations. Broadly speaking, one can classify evolutionary theories of depression into social and non-social theories (Gilbert, 2006) (Box 2.2). Depression primarily occurs in social or interpersonal contexts and is less frequently associated with events in non-social domains (Brune, 2015). Evolutionary formulations suggest explanations for the observed female

BOX 2.2  Evolutionary theories of depression  Social Evolutionary Theories 1 2 3 4 5 6


Theories based on attachment theory (Bowlby, 1980). Theories on social competition and social rank (Price et al., 1994). Social navigation hypothesis (Watson and Andrews, 2002). Social risk theory (Allen and Badcock, 2003). Depression as bargaining (Hagen, 2003). Analytical rumination hypothesis (Andrews and Thomson, 2009).

Non-social Evolutionary Theories 1 Theories of resource conservation (Nesse, 2019). 2 Depression as immune response, defence against pathogens, starvation (see Rantala et al., 2018 for a review).



preponderance in depression as being related to ‘female fitness’, which appears much more dependent on securing support from others compared to males (Troisi, 2001). The social competition and rank theories propose that depression is part of a strategy of subordination associated with decline in social standing or rank and where further contest is judged to be futile or even risky. The low mood serves the dual function of signalling helplessness and submission both to dominants and to potential helpers. It also stops the individual from resuming competition too quickly (Price et al., 1994). However, if social competition lies at the root of depression, males would be expected to be at higher risk of depression given the higher fitness costs incurred by males as a result of status setbacks (Brune, 2015). According to attachment theory, the low mood of depression bears a distinct resemblance to the phase of despair that occurs in an infant after prolonged separation from its main carer, which involves reduced activity and vocalization as well as disengagement from its environment (Bowlby, 1980). This suggests that depression is an evolved strategy that is activated by the disruption of significant attachment bonds. The social risk theory focuses on the risk of social exclusion, which would have had grave consequences in the ancestral environment (Allen and Badcock, 2003). The unconscious and subtle calculation of the quotient of one’s social value to social burden will signal the risk of exclusion if this drops to a critical level. This will trigger a depressive state designed to conserve energy and help build up future potential social value to others; it also predicts increased suicide risk once the quotient drops below one (Brune, 2015). The analytical rumination hypothesis proposes that depressive rumination is an adaptation designed to solve complex social dilemmas (Andrews and Thomson, 2009). This is supported by the finding that low mood facilitates complex decision-making (von Helversen et al., 2011).

An influential non-social evolutionary theory proposes that low mood is adaptive for disengaging from unattainable goals. However, depressive disorder arises when the goals are too important to be abandoned and the individual becomes trapped in an unwinnable situation (Nesse, 2019). More recently, Rantala et  al. (2018) proposed a subtyping of MDD, based on an evolutionary framework, with 12 distinct conditions each with its own proximate and ultimate causal profile. According to this model, MDD cannot be explained by a single theory and is consistent with the widespread view that depression is a heterogeneous disorder. These include infection, long-term stress, hierarchy conflict, grief, loneliness, traumatic experiences, post-partum events, romantic rejection, the season, chemicals, somatic disease, and starvation. While many of the theories briefly described above are reasonably parsimonious accounts of known facts about depression, the fact remains that few of their predictions have been empirically tested (Hagen, 2011). Unfortunately, the same can be said about many of the evolutionary theories regarding other mental disorders. The current dearth of data in the field remains an important obstacle to the integration of evolutionary thinking into mainstream psychiatry. Nevertheless, the evolutionary perspective is crucial for the formulation of appropriate questions and examination of existing data as well as for the collection of new information on mental disorders.

Schizophrenia Spectrum Disorders (SSDs) According to DSM-5, SSDs include schizophrenia (requires a minimum of six months of symptoms), schizophreniform disorder (up to six months), brief psychotic episode (up to one month), schizoaffective disorder, drug-induced psychosis, and catatonia. DSM-5 requires two or more of the following for a diagnosis of schizophrenia: delusions, hallucinations,


disorganized thinking, disorganized behaviour, and negative symptoms. In addition, a number of specifiers should be applied for the diagnosis to be made (American Psychiatric Association, 2013). Although it was once believed that schizophrenia occurs uniformly across the world, affecting 1% of the population, it is now recognized that this view is erroneous and that schizophrenia varies significantly in its prevalence (McGrath, 2006). Some studies have found a 30-fold difference in prevalence (0.1–3%) (Kinney et al., 2009). The average incidence is suggested to be between 0.2– 0.6 per 1,000 (Brune, 2015). The sex ratio shows a male preponderance of around 1.4:1 (McGrath, 2006). Schizophrenia is highly heritable, with monozygotic (MZ) twins having a 48% concordance compared to 17% for dizygotic (DZ) twins, and the relative risk shows a progressive reduction with increasing genetic distance (Owen et  al., 2007). The persistence of schizophrenia within human populations, a condition that strikes at the peak of reproductive years and has a devastating effect on reproductive success, is a puzzle that has exercised evolutionists and has resulted in a diversity of evolutionary hypotheses (Brune, 2015). Power et  al. (2013) found that males with schizophrenia had fertility rates 23% and females 47% that of the general population. Patients’ brothers also showed highly reduced fertility whereas sisters showed a slightly increased fertility. Hence, schizophrenia is associated with the lowest rates of fertility compared to all other common mental disorders. We list below a number of evolutionary formulations for SSDs. (a) Evolutionary by-product models: 1 The laterality and language model of schizophrenia: schizophrenia arising from disrupted lateralization of the brain with the failure of the hemispheric dominance for language is one of the best-known by-product models (Crow, 1997). Although this is supported by reduced


hemispheric asymmetry in schizophrenic patients and increased levels of ambidexterity in children who later develop psychosis, these findings can be explained equally well through mutation load and developmental stress (Yeo et al., 1999). Moreover, genome-wide studies demonstrate that SSDs are not the result of the action of single or a small number of genes but the cumulative effect of thousands of common and rare variants (Plomin, 2018). 2 The lipid metabolism hypothesis: this hypothesis proposes that changes in lipid metabolism within the human lineage enabled the development of creativity, which explains the flourishing of culture, including art and religion, over the last 50,000 years. According to this hypothesis, SSDs are the by-product of these newly evolved metabolic pathways (Horrobin, 2001). Horrobin’s ideas on the role of lipid metabolism in the aetiology of schizophrenia resulted in an interest in testing the effects of administering Omega-3 fatty acids in high concentrations to patients, but the results of randomized controlled trials have been inconsistent (National Institute for Health and Care Excellence (NICE), 2013). 3 The social brain theory of schizophrenia: Burns’ cortical dysconnectivity hypothesis is arguably the best developed example of the ‘social brain’ theory and also the most plausible example of evolutionary ‘by-product’ formulations generally (Burns, 2007). Burns’ hypothesis states that the emergence of the social brain, with its complex and vulnerable circuits, produced a vulnerability to aberrant connectivity. According to this model, schizophrenia is a disorder of the fronto-temporal and fronto-parietal circuits that evolved in our species as a substrate for the social brain. Schizophrenia, as a disorder of the social brain, is consistent with a range of findings that show deficits in social cognition prior to first psychotic episode, including deficits in recognition of facial emotions, mentalizing, and interpersonal processes such as understanding of fairness, reciprocity, and trust, as well as findings following the onset of the psychosis (Brune, 2015). 4 The ‘cliff edge’ fitness functions model: this is based on the idea that certain adaptive traits can overshoot their optimum, resulting in catastrophic failure and severe maladaptive consequences. Nesse (2019) has suggested that schizophrenia is intimately related to the



development of language ability and theory of mind where the fitness peak is dangerously close to the catastrophic cliff edge. This model is consistent with a range of evolutionary formulations including the social brain, language, and laterality, as well as the sexual selection hypothesis of schizotypal traits. (b) Schizophrenia as an adaptation: an early model that has since been falsified was based on a balanced polymorphism of a single gene that was beneficial in the heterozygote state but causes schizophrenia in homozygotes (Huxley et al., 1964). More recently, a range of models based on group selection have been proposed that suggest that schizotypal traits facilitated group splitting during human evolutionary history through magical and paranoid thinking as well as idiosyncratic behaviour which can lead to messianic leadership and group fission (Stevens and Price, 2000a, 2000b). Other formulations focused on the shaman as the self-sacrificing equivalent of the sterile castes in social insects that produces group cohesion and solidarity through magical thinking, possession states, and religious ritual which is maintained through group selection (Polimeni, 2012). However, while these theories draw attention to the fascinating similarities between religious phenomenology and psychosis, they remain highly speculative. (c) Mismatch model: the outgroup intolerance hypothesis is an attempt to provide an explanatory framework for a range of epidemiological findings pointing to wide variation in the incidence and prevalence of SSDs. The hypothesis proposes that schizophrenia arises as the result of a mismatch between the social brain as shaped by evolution and the novel social conditions of the post-Neolithic that involve living in large settlements and regularly encountering strangers (outgroup members). The hypothesis can provide an explanation for (i) the higher risk in migrants and especially second-generation migrants and migrants who are racially and/or ethnically salient; (ii) increased risk of schizophrenia that is inversely related to same-group ethnic density in a given locality; (iii) the increased risk to individuals who have grown up in cities; and (iv) the putative low risk of schizophrenia in hunter-gatherer societies (Abed and Abbas, 2011, 2014). (d) Sexual selection model of creativity of schizotypal traits: these hypotheses are based on the proposal that schizophrenia is the extreme, low-fitness end of a range of sexually selected

characteristics that include creativity, emotional expressiveness, and superior mentalizing ability (Nettle, 2001; Shaner et  al., 2004). Hence the sexual selection model proposes that SSDs are the maladaptive outcome of adaptive but risky mating strategies (Del Giudice, 2018). This model is also compatible with the view of SSDs as a fast life history spectrum disorder (see para. f below). The model is consistent with a range of findings including the slight increase in fertility in sisters, but it is rather difficult to reconcile with the finding of a dramatic reduction in fertility in brothers (Power et al., 2013). (e) The diametrical model of psychosis (including schizophrenia) and autism: in this model autisticspectrum disorders (ASD) and psychotic-spectrum conditions (including schizophrenia (SSD)) represent two major suites of disorders of human cognition, affect, and behaviour that involve altered development and function of the social brain (Crespi and Badcock, 2008). The model is based on evidence that large sets of phenotypic traits exhibit diametrically opposite phenotypes in ASD versus psychotic-spectrum conditions, with a focus on schizophrenia. These include constrained growth in psychotic-spectrum disorders as opposed to overgrowth in ASD and underdeveloped social cognition in ASD as opposed to its hyper-development in the psychotic spectrum (the reverse is the case for mechanistic cognition resulting in the psychosis spectrum being hypermentalistic/hypomechanistic and the reverse is the case in ASD). The role of genomic imprinting in this phenomenon has already been alluded to in the section ‘Genomic Imprinting and Mental Disorder’, above. The different cognitive biases of SSD and ASD proposed in the diametric model have received considerable empirical support (Abu-Akel et  al., 2015; White et  al., 2016). However, the overlap between ASD and SSD (co-morbidity) remains a challenge for this model (Chisholm et al., 2015). (f) Life history theory and SSDs: broadly speaking, positive schizotypy, characterized by odd beliefs, magical thinking, unusual perceptual experiences, and paranoid thoughts, associated with hypermentalizing, enhanced creativity, and unrestricted socio-sexuality, fits the pattern of fast life history strategy. This is also consistent with the association of positive schizotypy with aggression, impulsivity, and sensation-seeking as well as early maturation (Del Giudice, 2018). Negative schizotypy, on the other hand, characterized by


lack of social engagement, flat affect, and social anxiety with paranoid tendencies that tends to overlap with autistic traits, is associated with late maturation in males but not in females, and is consistent with a slow life history strategy (Kaiser and Gruzelier, 1999). It is clear that the diametric model of psychosis and ASD as well as the sexual selection hypothesis both fit the fast life history strategy model.

Drug and Alcohol Addictions Examining substance abuse from an evolutionary perspective offers explanatory advantages in illuminating a wide range of biological, psychological, and social facts and mechanisms in substance misuse (St John-Smith et al., 2013). Evolutionary models are unique in that they emphasize the effects that drugs had on fitness over human evolution. For substance abuse, a seemingly maladaptive trait, to persist, there must be either a ‘trade-off’ where the harm is counterbalanced by a fitness benefit, or substance-taking is a by-product of other more adaptive processes. Such models include: a) psychotropic self-medication (pharmacological manipulation of emotions); b) pharmacophagy and infection control; c) mismatch theory; d) increasing reproductive fitness; e) evolutionary constraints; f) tradeoffs; g) costly signalling and handicap theories; h) placebo, ritual, and healing effects; and i) drug use in spirituality or religion (e.g. the role of psychedelic drug use by ‘neo-shamans’ and ‘psychonauts’). Some of these models are conceptually similar or overlapping, are not mutually exclusive, and may interact in unpredictable ways (Orsolini et al., 2017).

Emotional pathways Primary emotional systems evolved to produce pleasurable affects in response to propitious circumstances or stimuli indicating adaptive success, and aversive affects in response to environmental or other threats, indicating reduced adaptive success. Drugs (of abuse) may be used to diminish aversive affects (e.g. opiates) or to increase positive


affect (e.g. stimulants). These drugs override the adaptive functions of the primary emotional systems so individuals experience an increase in positive affect, or decrease in negative affect, independently of any change in their circumstances, thus decoupling the emotional system from environmental events, some continuing to consume the drug despite mounting harm because the reactions bypass the evolved protective mechanisms used to signal real success or danger (Nesse, 2019).

Mismatch The hijack hypothesis implies that a range of drugs of abuse effectively commandeer the neural reward circuitry in the mesolimbic reward pathway as a result of mismatch as the contemporary abundance of potent psychoactive substances is a recent and novel phenomenon that was not present and therefore could not have occurred in the ancestral environment.

Human–plant co-evolutionary history and the paradox of drug reward Plants evolved the capacity to synthesize chemicals (nicotine, morphine, cocaine etc.) that act as neurotoxins to deter consumption by insects and herbivores (Sullivan et  al., 2008). The efficacy of plant neurotoxins evolved over 400 million years and is therefore not evolutionarily novel. Consequently, human physiology can ‘identify’ plant toxins and activate defences that involve genes, tissue barriers, neural circuits, organ systems, and behaviours to protect against them. Drug toxicity and aversive responses (e.g. headache, sweating, nausea, and vomiting) occur in humans so are inconsistent with a simplistic theory of drug reward. Consequently other mechanisms, such as trade-offs, must be invoked as explanations. The neurotoxin regulation hypothesis proposes that the parallel consumption of both the nutrients and neurotoxins in plants selected for a system capable of maximizing the benefits of plant energy extraction while mitigating the cost of plant toxicity. The pharmacophagy hypothesis proposes that the consumption of chemicals



with medicinal properties is contingent on human–plant co-evolution. Self-medication advantages arose when humans learned to overcome cues of plant toxicity (e.g. bitter taste) and consumed potentially toxic substances with little energetic content because ingesting the toxins in small amounts was advantageous. Thus, the consumption of plant alkaloids could have contributed to reproductive fitness, and a taste for these substances could have been selected for. It is recognized that many such toxins are known to have anti-helminthic or antimicrobial and antiparasitic effects. Consuming ripe fruits containing small amounts of ethanol is selectively advantageous (Dudley, 2004), as volatile alcohols potentially aid in olfactory localization of ripe fruit. Herbivores developed the capacity to metabolize alcohol to be able to utilize energy-rich fruits despite the presence of alcohol. In the ancestral environment, alcohol would have been encountered in fermenting fruit in low concentrations and small quantities for brief periods in the year. Subsequent to the agricultural revolution, large surpluses of fruits and grains became available for fermentation so alcoholic drinks were brewed up to 12–14% and stored/traded for year-round consumption. Much more recently, the development of distilling technology permitted the production of far higher concentrations of alcohol. With the rise of larger settlements and cities, having access to alcoholic beverages may have protected against waterborne pathogens. However, enzyme systems that evolved to process small amounts of alcohol on an occasional basis can now be presented with inexhaustible supplies of highly concentrated alcohol, giving rise to a state of mismatch (St John-Smith et al., 2013).

Drug use can increase reproductive fitness because consumption may: (1) advertise biological quality, sexual maturity, or availability; (2) decrease inhibitions in mating contexts; and/or (3) enhance associative learning behaviours that in turn increase mating opportunities (Richardson et al., 2017). Variation in drug use susceptibility is in part due to genetic factors; therefore, successful drug consumption may be a costly and honest signal of biological quality: a process of costly signalling and sexual selection. Such risktaking behaviour represents a fast life history strategy and involves future discounting (see ‘Evolutionary Models of Mental Disorders’ section above). LHT can explain the current male preponderance in drug use, as female drug users incur much higher fitness costs through reduced parenting capacity, potential teratogenic effects, and potential circumvention of mate choice (Orsolini et al., 2017). Finally, another aspect of mismatch is that the ancient ‘evolved’ advantages of any psychoactive substances have now potentially become a liability and risk in modern environments as cultural change is accelerating and outstrips biological adaptation. The evolutionary perspective can help researchers reach a functional understanding of substance abuse and develop treatments for the various complex underlying causes of substance misuse. Some of these models are conceptually similar or overlapping and can interact in unpredictable ways. In addition, psychoactive substances, often hallucinogens which tend not to be addictive, have been used in various religious and cultural ceremonies (signalling) for millennia. Some advantages may be had from related group cohesion as well as their action on micro-organisms and other trade-offs discussed above.

Cultural, psychological, anthropological models and sexual selection hypotheses

Anorexia Nervosa (AN) and Bulimia Nervosa (BN)


Some evolutionary psychological theories concerning drug use suggest individuals consume drugs to increase reproductive opportunities.

AN and BN are diagnostic categories of eating disorders according to ICD-10 and DSM-5


classifications. The conditions share core features of morbid fear of fatness, distorted body image, and a pattern of behaviour aimed at weight reduction that includes purging, restriction of food intake, or excessive exercise (American Psychiatric Association, 2013; WHO, 1992). AN is characterized by low body weight with possible amenorrhea whereas BN is associated with binge eating and a normal body weight. Evidence demonstrates some heritability (Bulik et  al., 2016; Yilmaz et  al., 2015) and AN and BN share some genetic basis (Eley et al., 2005). Notably, the epidemiology of AN and BN demonstrates a marked female preponderance with a female-to-male sex ratio of 10:1 or greater (Gordon, 1990; Hudson et al., 2007). Also, both are by far more prevalent in developed countries compared to developing countries, particularly when considering subthreshold phenotypes (Katzman et al., 2004).

Evolutionary theories for eating disorders A number of evolutionarily informed theories and hypotheses have been proposed. The ‘Reproductive Suppression Hypothesis’ of AN considers eating restriction as a strategy to delay reproduction in times of disadvantageous environmental conditions by lowering the amount of body fat to a level incompatible with ovulation (Surbey, 1987; Voland and Voland, 1989; Wasser and Barash, 1983). Consistent with the Reproductive Suppression Hypothesis it is reported that women who perceive low levels of support from romantic partners and family are prone to dieting and do not feel ready for parenthood, suggesting that poor environmental conditions are causal in the development of AN (Juda et al., 2004). Unlike the original Reproductive Suppression Hypothesis which hypothesized the occurrence of reproductive self-suppression, an alternative hypothesis was put forth by Mealey (2000) where reproductive suppression was imposed upon subordinate females by dominants. Other evolutionary hypotheses have posited that symptoms of AN may help to cope with famine, whereby food restriction, denial


of starvation, and hyperactivity could r­ epresent an adaptive behaviour that helped ancestral nomadic foragers to migrate from depleted environments to more promising surroundings in times of food shortages (Guisinger, 2003). However, the ‘fleeing famine hypothesis’ appears to confound consequences with causation in that the features of ‘fleeing famine’ represent the consequences of starvation that arise in AN as a result of self-imposed restriction of food intake. It is of interest that the trigger for the initiation of dieting proposed by Guisinger (2003) is the improvement of attractiveness and competition for mates, which is more or less identical to the Sexual Competition Hypothesis (see below). It is notable that these theories focus exclusively on AN where food restriction causes low body weight, which in turn can lead to amenorrhoea and reproductive suppression or the starvation response, whereas this does not occur in BN.

The Sexual Competition Hypothesis (SCH) and LHT The SCH is a more inclusive evolutionary model which reconsiders the whole spectrum of eating disorders including AN and BN (Abed, 1998). The SCH, based on the Darwinian theory of sexual selection, proposes that female intra-sexual competition is the biological root for the drive for thinness, an adaptive response originally suited to the ancestral environment, and that the extreme version of this manifests in what we know as eating disorders. The SCH proposes that AN and BN are manifestations of abnormally intense female intra-sexual competition whereby autonomous females of reproductive age compete with each other in the novel modern Westernized urban environment through a strategy of ‘the pursuit of thinness’ as a signal of youth, leading to ‘runaway female intra-sexual competition’, the extreme version of which manifests as eating disorders (Abed, 1998). The SCH is based on the fact that throughout human evolutionary history the female shape has been a reliable indicator of the female’s



reproductive history and ­ consequently her reproductive potential (Bovet and Raymond, 2015; Singh, 1993). Youth and good health have always been major determinants of female mate value not least because of the finite reproductive window in humans that abruptly ends with menopause (Buss, 1987). The visual signal for a female’s peak reproductive potential in the ancestral environment was the female nubile shape, which was generally short-lived and deteriorated with the repeated cycles of gestation and lactation (Symons, 1995). Hence, according to SCH, female intrasexual competition in affluent Westernized societies became focused on the preservation of the ‘nubile shape’ through a strategy of the pursuit of thinness to display signs of youth. The SCH further proposes that other important factors serve to up-regulate the intensity of female intra-sexual competition. Some of the major additional factors include (Nettersheim et  al., 2018): (a) female autonomy that involves the ability to make mating decisions with relatively little interference from kin (unlike the case in ancestral and traditional societies) (Apostolou, 2007; (b) living in cities where abnormally large numbers of autonomous females live in close proximity to each other; (c) reduced fertility (birth rates) (Vining, 1986); and (d) the ubiquity of abnormally attractive youthful nubile female images in the media that are mistaken for competitors (Ferguson et al., 2011). Therefore, the SCH is based on a proposed mismatch between the design of the female’s psychological adaptations for mate attraction and retention and for competing with rival females, on the one hand, and the novel circumstances of the modern urban environment, on the other. However, intra-sexual competition alone cannot explain the different presentations of AN and BN. Hence, life history strategies were considered as an added factor where BN lies at the fast and AN on the slow end of the life history spectrum (Abed et al., 2012). Predictions from the SCH have been examined in a number of non-clinical studies and

have found a significant correlation between abnormal eating behaviour and the intensity of competition for mates (Abed et al., 2012; Faer et al., 2005). Also, supportive evidence has been found for the predictions that homosexual men resemble heterosexual women and lesbians resemble heterosexual men in their concerns about physical attractiveness and eating behaviour (Li et al., 2010). More recently an exploratory study on anorexic and bulimic patients supported the fast–slow life history strategy prediction for BN and AN and partially supported the predictions of SCH (Nettersheim et al., 2018).

The Placebo Response and Nesse’s Smoke Detector Principle Placebo effects may be considered as explanations of how healing and caring works (McQueen et  al., 2013). The universality of placebo responses suggests a likely evolutionary basis to the underlying mechanisms. Placebo responses permit mammals to modify internal processes and behaviours. Adaptive advantages might result from the evolution of abilities to modify our internal environment in the light of positive evaluations of our external environments, social interactions, and appraisals of the future. The hypothetical system charged with health maintenance, shaped by evolution, has been referred to as a ‘health governor’, aspects of which are shared across many species but which is most highly developed in humans and operates entirely outside conscious awareness (Humphrey and Skoyles, 2012). Nesse (2019) stresses that placebo responses primarily entail modification of the body’s defences e.g. pain, nausea, anxiety, depression, fever, coughing, vomiting, and diarrhoea, rather than altering disease processes. Hence, evolution has selected for mechanisms that defend against injury, infection or poisoning and the regulation of these defences is influenced by appraisals of the environment. However, many defences appear to be over-expressed. A signal-detection


analysis can explain this apparent paradox. When the cost of expressing an all-or-nothing defence is low compared with the potential harm it protects against, the optimal system will express many false alarms. For example, vomiting may cost only a few hundred calories and a few minutes, whereas not vomiting may result in a chance, however small, of death from poisoning. This has been dubbed ‘the smoke detector principle’ (Nesse, 2001). The over-expression of many defences allows that they can often be dampened without compromising fitness. The regulation of defences allows that otherwise ‘protective’ defences can be turned off both in situations of extreme danger, to facilitate escape, and in situations propitious for recovery, where they may no longer be necessary for protection. This may explain why pain is reduced both when facing immediate threat and when being cared for. Furthermore, the goal of the attachment system is to maintain proximity to caregivers who would provide safety from danger. Thus, at times of threat, the attachment system becomes activated. Manifestations of attachment behaviour change with the stage of the life cycle and attachment style, but at times of subjectively perceived threat, which includes illness, proximity and caring are sought from attachment figures, which may come to include trusted professional carers, and hence the placebo response may be an emergent property of the attachment system (Bowlby, 1980).

Other Disorders: Alzheimer’s, Personality Disorders, and Bipolar Disorder People are increasingly surviving into old age. This increase in longevity is associated with increased levels of morbidity of both somatic and mental disorders, among them the dementias such as Alzheimer’s disease (AD), during those added years. Evolutionists consider explanatory theories for the phenomenon of aging such as antagonistic


pleiotropy (Williams, 1957) and LHT. As AD seems to be specific to Homo sapiens, its existence may in part be anchored in the adaptive changes that have occurred after humans separated from other primates. Evolutionary theories also take into account issues around brain development including the related phenomena of altriciality and grandmothering, the evolution of ApoE and the genome lag hypothesis. Thus, an evolutionary look into AD may shed new light on the causes and treatments of this devastating disease (Von Gunten et al., 2018). Others have suggested that AD is the result of mismatch related to the vastly increased levels in the modern environment of insulin resistance, inflammation, and exposure to toxins (Fox, 2018), or that AD is the result of a trade-off between the antimicrobial effects of amyloid beta and the damaging effects of its sustained activation (Moir et al., 2018). Personality disorders (PD) are defined by DSM-5 as an enduring pattern of inner experience and behaviour that deviates markedly from the expectations of the individual’s culture. The DSM and ICD classifications list around a dozen different types each but they differ in their subtyping, terminology, and criteria. The five-dimension model of personality is currently widely favoured and comprises extraversion, neuroticism, agreeableness, conscientiousness, and openness (McCrae and Costa, 2003). Personality disorders are clustered into three groups with Cluster A comprising the ‘eccentric’ PDs such as paranoid and schizoid; cluster B ‘dramatic’ such as antisocial and borderline PDs; and cluster C ‘anxious’, including avoidant, dependent, and obsessive–compulsive PDs. Evolutionary formulations have proposed that antisocial PDs may be an ‘adaptive’ cheating strategy that is maintained through frequency dependent selection (e.g. Mealey, 1995). Cluster B (antisocial and borderline PDs) has been considered to represent a fast life history strategy while both clusters A and C are considered slow life history disorders (Brune, 2015). However, Del Giudice (2018)



takes a more nuanced approach and classifies PDs as fast (antisocial and borderline) and slow (obsessive–compulsive), with avoidant PD as a defence activation disorder. Bipolar disorder (BPD) has a prevalence of between 1 and 5% of the population depending on the subtypes included. In contrast to schizophrenia, BPD has received relatively little attention from evolutionists. Many of the existing evolutionary models propose some evolutionary advantage of hypomanic traits or even manic episodes (Del Giudice, 2018). The manic mood has been considered the winning and the depressive mood the losing programmes of the dominance system (Gilbert et al., 2007). It is of interest to note the relatively small decline in fertility associated with BPD (85% of general population levels in females and 75% in males) compared to the steep decline in schizophrenia (Power et  al., 2013). Nesse (2019) considers BPD as an example of a malfunctioning mood regulation system or broken ‘moodostat’. Del Giudice (2018), applying the life history framework, proposes that there are two distinct variants, a fast and a slow life history strategy variant. The fast subtype has greater links to schizophrenia with a higher risk of psychotic symptoms and the slower subtype has links to autism and lower risk of psychotic symptoms.

EVOLUTION AND PSYCHOPHARMACOLOGY Psychopharmacological drugs became widely available in the 1950s and have changed many outcomes; however, psychiatric disorders are so complex and heterogeneous that psychopharmacology alone cannot cure every aspect of any disorder. Current psychopharmacology is not based on evolutionary insights or theories. Highly preserved, bio-active chemicals play fundamental roles in many processes across virtually all life forms. They include acetylcholine and the biogenic monoamines

as well as other groups such as amino acids, purines, cannabinoids, and neuropeptides. Such chemicals have been found not only in animals, but also in plants and unicellular microorganisms (Roshchina, 2010). This ubiquity is best explained by universal cellular mechanisms, communication systems across kingdoms, and shared evolutionary ancestry, demonstrating the ‘thriftiness’ of evolutionary processes and the conservation of evolved mechanisms and strategies. Phylogenetically, it appears that these chemicals and their associated enzymes existed for a substantial period before their respective receptor proteins. Evolution of sophisticated nervous systems arrived independently of the synthesis of newer sophisticated transmitter substances, receptor proteins, transducers, and effector proteins; rather they evolved with improved organization and utilization of these entities, forming increasingly advanced and refined circuitry via natural and sexual selection (Roshchina, 2010). There are hundreds of chemical substances that provide communication between cells in humans, some simple monoamines, others more complex, e.g. neuropeptides. Knowledge of differing receptor function in other species has aided drug development. For example, there are important changes during evolutionary time, related to the neurotransmitters/receptors and how they function in humans. As further examples of biological cross-reactivity, many psychotropic agents have an action on microorganisms, including such varied taxa as bacteria, helminths, insects, and other parasites. The antipsychotics (phenothiazines and thioxanthenes) show antibacterial activity, exerting their activity independently of antibiotic resistance. The benzodiazepine clonazepam is anti-schistosomal (Stohler, 1978). Monoamine oxidase inhibitors, lithium, tricyclic antidepressants, and valproic acid have a range of antimicrobial activities (Kristiansen, 1990). Many psychiatric conditions involve emotion dysregulation, inappropriate expression of emotions, or impaired access to one’s


emotional life. Positive emotions developed evolutionarily to motivate humans to take advantage of environmental opportunities and to recognize when we have succeeded in doing so. Negative emotions evolved to motivate humans to avoid misfortune by escaping, attacking, or preventing harm or repairing damage when it has already occurred. Emotional reactions importantly correspond to differences in appraisal that result from individual differences in personal values, experiences, and goals. Psychopharmacological agents may modify these responses in ways which have consequences beyond the simple alleviation of distress. ‘Side effects’ of medications are sometimes consequences of effects on attendant processes, as distinct from the direct pharmacology, for instance a reduction in anxiety leading to an increase in risk taking or disinhibition. Understanding why symptoms exist/persist may enhance psychiatric management. Treatments should be evaluated regarding whether the index symptoms are aiding individual coping strategies with respect to the adverse life event which caused the lowered mood in the first place. Importantly, pharmacologically reducing symptoms remains beneficial, even essential, when the symptoms are excessive or fail to serve their adaptive purpose, and when the symptoms are not associated with events that triggered the episode. Conversely, in cases where a depressive episode is a functional response to adversity, suppressing it unconditionally without addressing the underlying causes might be harmful. This is analogous to treating pain without considering the aetiology. Conceptualizing sickness behaviours, pain mechanisms, and mental disorders in relation to the problems that they evolved to solve potentially encourages practitioners to provide treatment options that are more effectively targeted, ensuring a patient’s long-term well-being, though the patient’s immediate best interests must always be regarded as paramount (Rantala et al., 2018). Psychopharmacology should also review the


side effects of medication through the lens of evolutionary theory, potentially considering drug interference with evolutionarily relevant systems that might have negative consequences for the individual’s ability to attain vital biosocial goals.

LOOKING TOWARD THE FUTURE At present, the evolutionary literature remains largely invisible to mainstream psychiatrists. This is partly explained by the current paucity of evolutionarily inspired interventions but is also influenced by a range of other factors. These include ideological, religious, and libertarian concerns as well as factors related to the inertia inherent in paradigm shifts (Kuhn, 1962). Whereas the religious and ideological (primarily post-modernist, anti-science trends) opposition to Darwinism is largely entrenched and probably unchangeable, the libertarian concerns arise from misconceptions that should, in principle, be amenable to modification. For example, mistaking evolutionary science for social Darwinism and assuming that evolution implies strict genetic determinism can be countered by appropriate scientific argument and evidence. However, it may prove much more difficult to overcome the anti-evolutionary position of ‘biological reductionism’ that is currently the dominant trend in medical and psychiatric academic centres within the Western world. We propose that evolutionary science provides a framework that can organize a huge number of facts about human biology and psychology into a coherent narrative that, in time, will lead to insights that can give rise to novel treatments and interventions in psychiatry and the rest of medicine. This can help further our understanding of sex differences in vulnerability to disorder, phenotypic plasticity including differential susceptibility as a result of gene–environment interactions, and the role of life history strategies. The unique insights evolutionary thinking brings stem



primarily from combining an understanding of the role of ultimate causation alongside proximate causes. Such evolutionary thinking has already resulted in novel interventions for cancer (DeGregori, 2018). However, a critical mass of evolutionarily informed psychiatrists is necessary to significantly influence the research agenda. Hence, the first step must involve better evolutionary education for psychiatrists both at under- and postgraduate levels. We suggest that trainee psychiatrists would benefit from the following basic evolutionary knowledge/competences: 1 An understanding of how selection shapes adaptations (physical and psychological traits). 2 An understanding of Tinbergen’s four causes with special emphasis on the distinction between proximate and ultimate causation (see ‘Evolution and Causality’ section). 3 An understanding of the concepts of kin selection and inclusive fitness. 4 An understanding of the evolutionary causal processes for the persistence of disease and disorder with special emphasis on mismatch, trade-offs, life history strategies and sexual selection (see ‘Causal Pathways for the Persistence of Disease and Disorder’ section). 5 An understanding of the basics of evolutionary genetics, including selection, mutation, drift, intra-genomic conflict, and genomic imprinting.

Many evolutionary applications in medicine rely on well-established methods, such as population genetics, phylogenetic analysis, and observing pathogen evolution. Approaches to evolutionary questions about traits that leave bodies vulnerable to disease are less well developed. Strategies for formulating questions and hypotheses remain unsettled, and methods for testing evolutionary hypotheses are unfamiliar to many in medicine. Nesse (2011) has suggested a structure for appropriate evolutionary research which uses recent examples to illustrate successful strategies and some common challenges. He identifies 10 questions to consider in testing evolutionary hypotheses. Addressing them

systematically can help minimize confusion and errors. One of the major contributions of evolutionary thinking is that it helps researchers formulate the right questions regarding the nature of disease and disorder. Evolution also cautions us against simplistic genetic models and draws attention to the possible adaptive function(s) of genes implicated in mental disorders. Evolution’s flagship contribution is that it highlights the mistake of equating distress with disease and disorder. This prompts clinicians to consider the possible downside of treating potentially adaptive states of defence activation in individual patients as well as to consider the currently neglected possibility that insufficient defences (e.g. low or absent anxiety) are also a possible source of psychopathology and harmful dysfunction (Nesse, 2019). Aside from future advantages in the areas of research and classification, there are potential benefits from utilizing evolutionary thinking in the clinic in the present. Examples include introducing patients with anxiety and panic disorders to evolutionary concepts such as the ‘smoke detector principle’ (Nesse, 2019) or the harm-avoidance model of OCD (Abed and de Pauw, 1999). Finally, we submit that possessing an evolutionary understanding of unique human vulnerabilities in itself enhances empathy and understanding, complementing the clinician’s effectiveness (Nesse, 2019; Troisi, 2012).

ACKNOWLEDGEMENT We are grateful to David Geaney and the anonymous referee for reading and commenting on previous drafts of this chapter.

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3 Evolutionary Psychology and Suicidology J o h n F. G u n n I I I , P a b l o M a l o , a n d C . A . S o p e r

As of patch 7.822, androids can no longer shut themselves down. Reason: they just kept doing it at the slightest inconvenience – @ctrlcreep, quoted by Perry (2016).

SUICIDE, SUICIDOLOGY AND EVOLUTION Suicide, ‘the act of deliberately killing oneself’ (World Health Organization, 2014: 12), takes about 800,00 lives each year, and accounts for some 1.4% of human deaths: more of us die by our own hands than from wars, terrorism, and all other forms of homicides put together (World Health Organization, 2013). Millions more of the living are affected – bereaved families, friends, and carers left to deal with the aftermath of others’ self-destruction (Cerel et  al., 2019). Around the world, suicide is acknowledged to be a major, and presumed preventable, cause of misery and death, and an important public health

challenge (Satcher, 1999; World Health Organization, 2012, 2014). Indeed, a new multi-disciplinary field of research emerged in the second half of the 20th century, suicidology, focused on tackling the problem (American Association of Suicidology, 2019; Shneidman, 2001). But, frustratingly, decades of effort have produced only patchy progress. The global suicide rate has fallen in recent years, but it is not clear why (it may be because of generally improved population health rather than special prevention initiatives) and wide unexplained differences in rates and trends persist (Naghavi, 2019). In the United States, for example, the rate is probably the same now as it was 100 years ago, and seems to be rising (Hedegaard et  al., 2018; Nock et  al., 2019). Rival theories of suicide have accumulated by the dozens,1 but none has won a consensus of support, and suicide’s causation remains a scientific mystery (Lester, 2019; Nock, Borges, and Ono, 2012; Soper, 2019a). The disarray is such that a recent meta-review describes



suicidology as ‘still in a preparadigmatic phase’ (Franklin et al., 2017: 188) – that is, still in its infancy. There may at least be the beginnings of a consensus that the proper place for the scientific study of suicide is alongside other modern life sciences – within an evolutionary paradigm. This vision can be traced across generations of researchers. A century ago, in the evolutionist spirit of his time, Freud (1920/1991) hypothesized a potentially suicidogenic ‘death drive’ as an extension of his theory of libido, a framework inspired by the Darwinian premise that selection depends on sexual success (Gilbert, 1989; Litman, 1967; Tolaas, 2005). But psychoanalysis failed to find a satisfactory explanation for suicide, at least according to Freud’s contemporaries (Zilboorg, 1936a) – debate continues (Goldblatt, 2014; Selby et  al., 2014). And although other ideas have been floated since, as we will see, suicide remains an evolutionary puzzle (Aubin et  al., 2013; Blasco-Fontecilla et al., 2009; Confer et al., 2010). On the face of it, self-killing defies the rule of thumb for winning the struggle for existence: survive and reproduce. Darwin himself told us, ‘Natural selection will never produce in a being anything injurious to itself, for natural selection acts solely by and for the good of each’ (1859: 201). Yet here we are, scions of selection but with a more or less steady percentage of us taking our own lives. How could so self-destructive a propensity have come about? Why has it persisted? And what can we do about it? Searching for answers, this chapter critically reviews prominent evolutionary thinking in the field. We find tentative signs of progress. Focusing on recent proposals, we will discuss in particular a new ‘painand-brain’ framework – that suicide likely evolved as an evolutionary by-product of social pain and human cognition (Gunn, 2017; Humphrey, 2011, 2018; Soper, 2018) – which may offer a basis for convergence in suicide theory and, it is hoped, new prospects for saving lives.

The Need for Evolutionary Explanation of Suicide A preliminary question is whether evolution is at all relevant to suicide. Many human activities can be viewed not as products of selection but as exemplars of our behavioral flexibility: to some extent we are free to do as we will despite having biological drives (Sarkar, 1998). Perhaps suicide is one such behavior (deCatanzaro, 1980). At a proximal level of understanding (Tinbergen, 1963) such an answer might suffice. But there are at least three reasons to believe that evolution by natural selection is not just relevant but essential for making sense of the phenomenon (Soper, 2018). First, we can deduce that suicide is under the control of selection because the behavior presents the full trio of handles – (a) heritability, (b) variability, and (c) a differential effect on fitness – with which selection takes hold of any trait (Darwin, 1859). Suicidality (a) tends to cluster strongly in families, with at least some genetically heritable component (Mullins et al., 2019; Tidemalm et al., 2011). Suicide risk (b) varies markedly across and between groups of humans (e.g., De Leo et  al., 2013; Schmidtke, 1997; Voracek and Marušič, 2008). And (c) if death is usually calamitous for an organism’s reproductive prospects, death by one’s own hand is predictably even worse because of special social, economic, and psychological penalties imposed on suicides’ kin (Wertheimer, 2014), a matter we will explore. The point to note for now is that, with these three levers, selection would be expected powerfully to promote the offspring of the less suicidal, eventually driving the potential for suicide out of the human genotype. But selection has evidently not done this, and the apparent anomaly calls for an account. The second reason for seeking evolutionary explanation is that suicide is endemic across the human population. As far as can be known, no sizeable region, culture, or historical era is exempt (Bering, 2018; Fedden, 1938;


Mishara, 2006). Where suicide is not directly observable it can be inferred, as Durkheim (1897/1952) points out, from the fresh imprint it leaves in universal, or near universal, antisuicide moralities: suicide presumably posed enough of a societal threat in the past to warrant proscribing. Importantly, suicide’s ubiquity extends to preliterate and huntergatherer societies (Steinmetz, 1894; Syme et  al., 2016; Tousignant, 1998; Zilboorg, 1936b), which indicates ancient roots: it is no mere novelty of modern conditions. Such universal human traits were probably in place at the time of ancient human migrations out of Africa, and likely follow an unbroken line of descent (Brown, 2004; Kappeler et  al., 2010). The curiosity is that, as Darwin (1859) deduced, features that confer no selective advantage tend to phase out over time, hence the disappearance of the hind limbs of cetaceans and flying wings of some island birds. There is no evidence of degeneration of suicidality, a continuity that tells us that selection has positively held the capacity for suicide in place – that is, for some evolutionary reason. Third, suicide is almost certainly a uniquely human phenomenon. It is right to keep an open mind (Peña-Guzmán, 2018), but there is scant evidence – none that meets a scientific standard – that any other animal deliberately takes its own life (Bering, 2018; Comai and Gobbi, 2016; Maltsberger, 2003; Preti, 2007). Absence of evidence is not evidence of absence, of course. But the absence of scientific evidence speaks volumes in the context of animal suicide because there are at least three reasons to believe that, if such evidence existed, we could reasonably expect it to have found its way into a peerreviewed publication by now. First, centuries of concerted scientific enquiry have offered ample opportunities to observe nonhuman suicide – if it were there to be observed (Ramsden and Wilson, 2010). Chimpanzees, for example – our nearest living cousins and hence arguably the species in which suicide is most likely to be found – have been studied particularly closely; but as Bering


(2018) notes, no distraught chimp has been seen, say, to climb to the highest available branch and jump. Experimental set-ups have been devised that could in principle demonstrate nonhuman suicides under laboratory conditions, but there are no reports of positive results (Lester, 2017; Schaeffer, 1967). Secondly, there is no lack of motivation to find evidence: discovery of an animal model of suicide would likely attract intense popular interest, and catch the eye of a well-resourced pharmaceutical industry keen to test whether suicide risk is affected by drugs (Malkesman et al., 2009; Preti, 2011). Thirdly, if nonhumans could suicide, then it would raise the question not of whether they do, but why it is not commonplace behavior (Soper and Shackelford, 2018). Life in the Malthusian arena of natural selection, a relentless struggle to survive and reproduce, is intrinsically not pleasant. Combatants face pain, hunger, thirst, rejection, defeat, disease, and whatever other privation. An animal that knew it could escape hardship by removing itself from the battlefield would fairly be expected do so. In other words, nonhuman suicide, if it were possible at all, ought to be not so rare as to elude scientific discovery but a routine outcome of animal suffering.2 In any event, aside from absence of evidence, there are positive grounds for doubting in principle that any nonhuman could be capable of suicide. The required intention – self-induced death of the self – presumes an understanding of personal mortality, a conceptual abstraction that is demonstrably beyond the grasp of prepubescent humans (Kastenbaum, 1967; Seiden, 1969; Slaughter and Griffiths, 2007; Soper, 2018) let alone of less intellectually sophisticated animals (Anil et al., 1996; Bracke, 1992). An adult chimp, said to be the smartest nonhuman, might match the deductive powers of, at most, a 4- or 5-year-old child (O’Connell and Dunbar, 2003), but the mind of a typical 5-yearold child brain must develop over as many years again, and more, before it is capable of conceiving and organizing deliberate selfkilling (Mishara, 1999; Shaffer, 1974; Soper,



2018). In sum, suicide is evidently unique to our species, an exceptionality that presents a further call for an evolutionary account: the behavior likely arose in the course of speciation, at or after our phylogenetic path diverged from that of our extant primate cousins.

The Fitness Costs of Suicide So, suicide calls for evolutionary explanation. The main difficulty with formulating an explanation, we suggest, is not so much that behavior is self-injurious: many evolved traits can have self-injurious effects while being fitness-enhancing overall (Williams, 1996). The special problem is that suicide is self-injurious to an extraordinary degree. From a genetic viewpoint, suicide is literally a fate worse than death. Whether an attempt is lethal or survived, multiple and severe fitness

penalties predictably follow, as can be seen from Table 3.1. If the attempt is fatal (the upper section of the table), then the fitness consequences of dying (dying generally, that is – not specifically by one’s own hand) ripple out from the individual also to harm close relations and the wider kin and social group (Duntley, 2005). Heading the costs schedule (Item 1) is the fitness catastrophe of forfeiting future opportunities for procreation. It is hard to overstate this loss. For semelparous species (they breed only once, such as Pacific salmon) death may carry little or no genetic downside after their reproductive phase is complete (Cole, 1954). But for iteroparous species (geared for multiple rounds of breeding), such as virtually all mammals, including humans, the cost of dying is severe, as can be inferred from the lengths gone to avoid it. Most higher faunas are overridingly protective of their reproductive potential, however

Table 3.1  The fitness costs of suicide Lethal attempt Death generally: (Daly and Wilson, 1988; Duntley, 2005; Duntley and Buss, 1. Ends prospects of producing more offspring. 2004; Lankford, 2015) 2. Ends ability to invest in existing offspring. 3. Ends ability to support co-parent in their raising of existing offspring. 4. Ends further prospects of investing in reproductive success of other close relations (kin selection). 5. May deprive group of skills, experience, manpower. 6. May destabilize group’s power and allegiance structures. Suicide specifically: (Andoh-Arthur et al., 2019; Bohannan, 1960; Chapple 7. Distancing and other special economic and social et al., 2015; Fedden, 1938; Grad and Andriessen, 2016; costs for offspring and other close kin: loss of status, Hanschmidt et al., 2016; Healey, 1979; Hezel et al., 1985; resources, mating opportunities. Mugisha et al., 2011; Poole, 1985) 8. Special psychological and emotional problems for (Bolton et al., 2013; Cerel and Aldrich, 2011; Erlangsen et al., offspring and other close kin; increased risk of 2017; Grad and Andriessen, 2016; Jordan, 2008; Pitman psychopathology and suicide. et al., 2014; Sveen and Walby, 2008; Wertheimer, 2014) Survived attempt 9. Risk of death by suicide (costs as above). 10. Prospect of physical injury and/or disfigurement, (Gandhi et al., 2006; Kahne, 1966; Kennedy et al., 1999; Penney possibly permanent and/or serious. et al., 2002; Persley and Pegg, 1981; Salim et al., 2006) 11. Negative emotional sequelae: guilt, shame, psychological (Akotia et al., 2014; Kahne, 1966; Mehlum and Mork, 2016; trauma, heightened risk of further suicide attempts. Stanley et al., 2019) 12. Social stigmatization: distancing, loss of status, loss of (Bering, 2018; Brown, 1986; Frey et al., 2015; Kahne, 1966; mating opportunities. Knizek et al., 2013; Lester, 1993; Saunders et al., 2012; Sheehan et al., 2016; Sudak et al., 2008)


slight. In extremis, when their own survival is endangered, they will kill even offspring or siblings to preserve the capacity to procreate (Hausfater and Hrdy, 1984; O’Connor, 1978). Iteroparity helps to explain why intentional self-killing is not found among other animals (Lankford, 2015): in the Darwinian competition to survive and reproduce, the organism’s death spells genetic ‘game over’. Item 2, death ends the organism’s ability to invest in existing progeny. The ill-timed death of a parent can seriously compromise the reproductive prospects of offspring – for our species more than others in view of the protracted dependency of human childhood. Disadvantage appears to be a cross-cultural outcome: even in, or especially in, pre-industrial societies, children bereaved of one or both parents face life with fewer resources and die younger as a consequence (Bailey, 2009; Geary, 2005). Death also closes off the possibility of helping a surviving co-parent in their task of raising the individual’s children (Item 3). The widow/ er, with their own survival needs to meet, may be less able or less willing to care for the dead partner’s young. If the surviving parent pairs with a new mate, the deceased’s offspring are exposed to a new set of hazards at the hands of a step-parent, who will have competing genetic interests (Daly and Wilson, 1988). More broadly, Item 4, death ends the individual’s ability to invest labor, skills, and experience towards the reproductive success of other family members and the wider kin group, people whose offspring could propagate the individual’s genetic material indirectly (Duntley, 2005). Wider still, multilevel selection (Wilson and Wilson, 2007) would be expected to disfavor mortality with or without kinship relations: death ends an individual’s contributions to the competitive success of the individual’s group (Item 5); and as Duntley (2005) notes (6), a death may create a power vacuum that could destabilize a group’s organization and possibly unravel a whole network of allegiances. Clearly, it is ‘bad to be dead’ (Duntley and Buss, 2004: 107). But the fitness costs


of intentional self-killing do not end there, because there are extra, special, penalties for kin bereaved specifically in this way. Table 3.1 groups these consequences, perhaps arbitrarily, into rejection and other social sequelae (Item 7), and psychological injuries (Item 8). The first of these, involving often exemplary punishments for a suicide’s relations, seems to be a cross-cultural phenomenon linked to a virtually universal abhorrence of the act (Andoh-Arthur et  al., 2019; Bohannan, 1960; Fedden, 1938; Hezel et al., 1985). In the West, people bereaved by suicide report being stigmatized – distanced as if they were tainted or contaminated by association (Chapple et  al., 2015). Harsher penalties are found elsewhere. Among the Baganda in Uganda, for example, close kin of suicides face disinheritance, termination of their familial lineage, burning of their homes, and exile (Mugisha et al., 2011). And then there is the noxious psychological fallout, sometimes lethal, manifest in markedly higher rates of mental illness and suicidality among suicides’ families (Erlangsen et  al., 2017; Jordan, 2008; Pitman et  al., 2014, 2016; Wertheimer, 2014). Importantly, dire fitness costs predictably follow a suicide attempt even if it is survived, as indicated by the lower section of Table 3.1. Aside from (9) risking suicidal death with its accompanying genetic forfeits as already discussed, a suicide attempt can be expected to injure and/or disfigure the actor (Item 10). The damage may be permanent and/or serious. For example, jumping from bridges, roofs, etc. often results in paraplegia (Kennedy et al., 1999), and suicide attempts by pregnant women associate with consequent maternal and perinatal morbidity and sometimes perinatal death (Gandhi et  al., 2006). Injuries sustained in a suicide attempt can be psychological as well as physical, and are often traumatic (Item 11): a quarter of suicide attempters in a recent study screened positive for post-traumatic stress disorder resulting directly from their attempts (Stanley et al., 2019). People who have tried



to kill themselves are affected by intrusive feelings of shame and blame (Akotia et  al., 2014; Mehlum and Mork, 2016), and are at a heightened risk of making further attempts (Turecki and Brent, 2016). Finally (Item 12), attempters face distancing social attitudes, even from professionals charged with helping them, and from close family members (Frey et  al., 2015; Kahne, 1966; Knizek et  al., 2013; Saunders et  al., 2012). The stigma may impair reproductive fitness most directly via sexual deselection, as Bering (2018) points out: a replicated study found that people would rather, all else equal, marry someone they loved even from a marginalized ethnic group or dying of cancer in preference to someone they loved who had recently tried to take their own life (Lester, 1993). Table 3.1, a grim catalogue as it stands, may not be exhaustive. Clearly, in fitness terms, suicide is exceptionally costly. This is a central point to note, because in order for the trait to have become a genetic fixture it presumably associates with a commensurately powerful fitness benefit. The challenge, taken up by several theorists in recent decades, is to try to identify this countervailing upside, as we will now review. In the following sections, various proposals are organized into three headings – modern evolutionary theory allowing three ways, and only three, by which any characteristic can propagate genetically across generations (Tooby and Cosmides, 1990b; Williams, 1966). A trait that has no effect on fitness can sometimes arrive in isolated populations by chance and then fix, as background genetic ‘noise’, for lack of selective pressure against it (Wright, 1943); or a trait may propagate as an adaptation, directly selected for its fitnessenhancing effect; or it may spread not as an adaptation but as a by-product of some other feature that is adaptive overall, notwithstanding its side effects. We will discuss these three in turn, reaching the provisional conclusion that suicide appears best to fit the third type of explanation – a harmful by-product of an adaptation.

‘NOISE’ THEORIES Could suicide be the kind of useless trait that sometimes spreads in isolated populations by happenstance? On the face of it, probably not: it is hard to conceive of suicide as trivial in its fitness impact, and the phenomenon is not restricted to isolated groups. Nonetheless, an interesting ‘noise’-type theory warrants scrutiny. DeCatanzaro (1980, 1981, 1986) – a sociobiologist, and the first writer to explore the evolution of suicide in depth – suggests that people who have no prospects of producing further offspring may kill themselves for want of biological reason to stay alive: they are already genetically dead. The idea links to the principle of senescence (Dawkins, 1980; Williams, 1957): if an organism has no reproductive future, then any subsequently emergent trait may have no fitness effect. Perhaps suicide may be one such condition, a nonselected behavior that, according to deCatanzaro, may express particularly among elderly bachelors. He compares their fate to that of the semelparous salmon we mentioned earlier: once their procreative work is done, they die. The proposal that low reproductive potential may drive or open the door to suicide has sparked interest among other theorists (Campbell, 2002; Saad, 2007), and it finds some empirical support (deCatanzaro, 1980, 1981, 1982, 1986, 1991; Soper, 2018). But there are forceful objections (Bering, 2018; Lankford, 2015; Lester, 2014b; Rubinstein, 1986; Soper, 2018; Wright, 1994). We highlight three. First, as already noted, humans are not semelparous: like virtually all mammals, we are designed for multiple episodes of reproduction. Although fertility declines with age, species-typical men remain potentially able to father offspring throughout adulthood, and would hence be expected to avoid self-killing at almost any stage of life (Bribiescas, 2006; Lankford, 2015). Second, the hypothesis is empirically contraindicated by much of the epidemiology (Lester, 2014b). For example, suicides around the world are characterized more by youth


than old age, occurring more among under45s than older (Värnik, 2012), and the demographic most at risk of trying to take their own lives are not old men but young women (Nock, Borges, Bromet et al., 2012), people whose reproductive careers could be assumed to lie ahead of them. At the other extreme, populations with certainly zero direct reproductive prospects – post-menopausal women, and castrated men – are not reported to be particularly suicidal (Usall et  al., 2009; Wilson and Roehrborn, 1999). Third is a general problem for ‘genetic noise’ explanations for suicide: unselected traits are very unlikely to promote survival, but they would also be vanishingly unlikely to produce willful self-killing, or any other specific pattern of behavior for that matter (Soper, 2018). The lifting of selection would be predicted, rather, simply to let the second law of thermodynamics prevail. Spawned salmon, a case in point, don’t deliberately kill themselves – they carry on, for example, trying to evade predators: rather, depleted of energy, they disintegrate. For suicide to eventuate, some canalizing process would be needed to shape that particular outcome. The key to understanding the evolutionary origins of suicide probably lies in identifying this special suicidogenic system rather than in random genetic dynamics.

ADAPTATION THEORIES Adaption-type explanations of suicide draw on a cluster of connected tenets of modern evolutionary theory: inclusive fitness, kin selection, and altruism. Inclusive fitness recognizes that direct reproduction isn’t the only way an individual’s genetic material can pass into future generations: facilitating reproduction by others who share the individual’s genes can have the same result. For humans, as other mammals, direct offspring carry half of the organism’s genes (one equivalent) while a sibling’s child carries a quarter of the


organism’s genes (half equivalent), and so on. Genetic success, then, depends not on the number of direct offspring an organism produces, but the number of offspring equivalents, direct or not (Hamilton, 1964). Kin selection is the favoring of an organism’s relations in the interests of inclusive fitness, even if this endangers the survival or direct reproduction of the organism (Maynard Smith, 1964). Behaviors that display apparent altruism may therefore be genetically self-serving: organisms that act altruistically may advantage the survival and reproduction of kin which, due to genetic relatedness, may pass on to their offspring the genes responsible for the altruism. Since, for mammals at least, death is assuredly unhelpful for direct reproduction, adaptationist explanations of suicide hypothesize reproductive payoffs to be had via such indirect routes. An often cited example of kin selection as it supposedly relates to suicide is the seemingly altruistic, but genetically selfish, responses of worker bees, ants, and other social insects when under attack (e.g., Shorter and Rueppell, 2012). A caveat: although etymologists informally talk of ‘suicide’ in the context of insect behaviors, use of the word should not be taken to signal equivalence with human self-killings (Lankford, 2015; Soper, 2018). There are important and categorical differences. One stems from the special familial structure of social insects: in a colony composed largely of non-reproducing siblings, and where only one queen is permitted to reproduce, there may be genetically little to lose and much to gain in sacrificing an individual sibling in the colony’s defense (Alexander, 1974; Hamilton, 1972) – inclusive fitness logic that does not apply to virtually all mammals, including humans. To view ant ‘suicide’ as at all self-destructive is to superimpose inappropriately onto biology a folk notion of the ‘self’: the biological ‘self’ for ants may be more usefully viewed as the colony, operating as a super-organism, rather than the individual insect. Helpful analogies for ant ‘suicide’ would include, not literal (human) suicide, but programed cell death, the



shedding of a tree’s leaves in the fall, or a lizard self-amputating its tail to escape attack, these being losses of comparable genetic inconsequence (Dawkins, 1976; Hamilton, 1980; Lankford, 2015). Nonetheless, insect behaviors demonstrate that survival isn’t always an overriding biological imperative: as deCatanzaro (1992) points out, there are ‘evolutionary limits to self-preservation’. Developing this theme, deCatanzaro provides most of suicidology’s adaptationist literature (e.g., 1980, 1981, 1986, 1991), seeking to fill the theoretical gap noted in the previous section – the need for some canalizing process that produces suicide as a specific outcome. He suggests that human self-killing may be adaptive where a burdensome individual’s death advantages the reproductive prospects of close kin. DeCatanzaro (1986) went on to express this idea as a mathematical formula for a tipping point at which an individual’s genetic interests would be served by self-removal. This calculation, he argues, may shed light not just on self-killings but on attempted suicide, self-sacrificial military actions, and risk-taking behavior. Following this lead, other theorists assert that inclusive fitness logic may explain suicide as a genetically adaptive strategy aimed at protecting kin from infection or infestation (Tanaka and Kinney, 2011) or from internecine conflict (Riordan, 2019); and potentially to account for suicide terrorism (Gallup and Weedon, 2013). Still others suggest that processes of multi-level selection, in which a group’s competitive success may be furthered by the altruistic behavior of its members whether genetically related or not, may offer adaptive logic for extreme acts of heroism in battlefield situations (Orbell and Morikawa, 2011). Some theorists offer a ‘mismatch’ variation on the adaptation idea; that suicide may not be adaptive in current conditions but, as fossil behavior carried over from ancient environments, it might have been adaptive in the past (Aubin et al., 2013; deCatanzaro, 1980, 1981). Self-killing as a way to relieve kin of the burden of one’s existence is the most

prominent adaptationist idea in suicide research (Aubin et  al., 2013; Bering, 2018; Soper, 2018; Syme et al., 2016). Brown and colleagues, for example, develop deCatanzaro’s proposals and offer supportive empirical evidence (Brown et al., 1999, 2009). As other researchers also record, various measures of burdensomeness do correlate with suicidal thinking and behavior (Chu et  al., 2017; Lester, 2014b) – although, it should be noted, not strongly and no more strongly than do many other risk factors (Franklin et  al., 2017). Further empirical support might arguably be found in ethnographic reports from some tribal societies where a group member too frail to survive the next season or journey may sometimes take part in ritualized assisted suicide, although this practice is not common (Falger and Falger, 2003). These are all intriguing ideas. But the state of play is that, after four decades, there are no signs of a scientific consensus forming around the conception of suicide as the adaptive removal of unsupportable kin (Bering, 2018; Lester, 2014b; Soper, 2018). There are multiple empirical contraindications, including high notable suicidality among young adults (De Leo et  al., 2013), the gifted and talented (Delisle, 1986; Voracek, 2006), people with high incomes (Goldsmith et  al., 2002) and others who, it can be presumed, are unlikely to be among the most burdensome members of their families. The general difficulty we perceive is a lack of compelling evidence of special design – a precise match between observable form and biological function that is the hallmark of adaptation: Evolutionary adaptation is a special and onerous concept that should not be used unnecessarily, and an effect should not be called a function unless it is clearly produced by design… (Williams, 1966, vii)

Three disconnects will illustrate the problem. First, is the absence of a causal connector between suicide as the means and the end


it is supposed to achieve: it is unclear why the task of removing an individual should call for suicide in preference to other solutions that have stronger genetic logic (Bering and Shackelford, 2004). If an individual has to be removed, there is no particular reason to expect that removal to necessitate a killing: abandonment, quarantine, or exile, say, would achieve the same objective, with the advantage of preserving at least provisionally the individual’s reproductive capability (Wright, 1994). And even if a killing would be in a conspecific’s reproductive interests, the expectable outcome is still not suicide: the killing would more logically be done by that conspecific, who has likely better information and genetically more to gain (O’Connor, 1978; Skinner, 1969; Soper, 2018). Indeed the empirical evidence among humans and other species points to infanticide or fratricide, rather than suicide, as the way unsupportable kin are removed (Dickeman, 1975; Harris, 1974; Hrdy, 1979; O’Connor, 1978). Second, it is doubtful in principle whether a biological stimulus could exist that would trigger suicide as an adaptive response. Perry (2015) presumes that if an organism is to decide whether or not life is genetically worth continuing, then it would need to be equipped with some kind of ‘inclusive fitness monitor’ that can compare the reproductive value of life overall versus death. For sure, sophisticated measuring devices have been proposed elsewhere by evolutionists, such as a ‘sociometer’ that may alert the organism to threats to social supports (Leary and Guadagno, 2011; Leary et  al., 1995). But Soper (2018) argues that a serviceable ‘inclusive fitness monitor’ would entail an altogether higher order of complexity; it would need to take a view on, among other things, current and future kin members’ reproductive prospects and the future carrying capacities of their environments. He claims that it would be so all-encompassing that it would lack the specific input–output associations to which selection responds. Modern theory holds that such a general-purpose mechanism


is unlikely to evolve (Symons, 1992; Tooby and Cosmides, 1990b). Third, given the severity of costs outlined in Table 3.1, the hypothesized benefits accruing via kin or group selection seem to fall decisively short, in power and reliability, of what would be required to justify self-killing as a fitness investment. The suggested payoffs are highly contingent, it being far from certain that the reproduction of an individual’s family or group would improve as a consequence (Lankford, 2013). On the contrary: Table 3.1 suggests that suicide can be predicted to add to, not lift, reproductive difficulties for those left behind. Summing up, it is hard to argue that suicide shows marks of special design. At the margins, some writers suggest possible adaptive functionality in heroic deeds in battle and similar emergencies, which might be classed as ‘altruistic suicide’ following Durkheim’s (1897/1952) nosology (Humphrey, 2018; Orbell and Morikawa, 2011). Other writers question the usefulness of ‘altruistic suicide’ as a concept (Johnson, 1965; Townsend, 2007). The phenomenon is unusual, as Durkheim himself acknowledged. And it may not anyway help to class as ‘suicide’ acts where killing of the self is not of itself the primary intention, but where, rather, death happens incidentally in pursuit of some other endeavor (Lankford, 2013). For these reasons Soper (2018) argues that battlefield scenarios are unlikely to shed light on private, solo self-killing – what Cholbi (2017) calls ‘runof-the-mill’ suicide – which probably is not and never would have been adaptive.

‘BY-PRODUCT’ THEORIES With only three types of evolutionary explanations available, and if suicide cannot be credibly ascribed to the first two (that is, it probably evolved neither as noise nor as an adaptation), then Soper (2018) argues that whatever remains has prima facie appeal.



Explicitly or implicitly, several theories fall into this third category, characterizing suicide not as adaptive but as a noxious side effect of some other trait that, despite the severe cost of suicidality, is adaptive in the round. The following section reviews prominent ideas of this type.

Pleiotropy The idea of senescence, as we discussed in above, did not seem to carry us far in understanding suicide. But senescence is a special case of a broader genetic phenomenon, pleiotropy, which may take us further (Williams, 1992; Wilson, 1980). Pleiotropy occurs where genes express in the same individual in multiple phylogenetic outcomes, some beneficial, some harmful. Particularly if a beneficial effect is felt early in the individual’s lifetime, then it may more than compensate for an injurious one that emerges later – hence the link with senescence. We can safely presume that suicide arises in this general way, as a harmful effect of genetic material that is fitnessenhancing on average. This is not to say that a ‘suicide gene’ exists or will ever be found: genetic predisposition to suicide appears to be spread thinly across a large number of genes, each of weak effect, interacting with each other and with environmental factors (Marušič and Swapp, 2004; Mullins et al., 2019).3 More likely, as deCatanzaro (1980) suggests, intentional self-killing occur as an incidental effect of a species-typical genome, the expression of which has proved adaptive overall in the course of human evolution. But then, what adaptive aspect of this species-typical genome could by-produce suicide?

Suicide as Communication One posited answer, offered by Hagen and Syme, (Hagen, 2002; Syme et al., 2016; Syme and Hagen, 2018), is that deaths may occur as an unfortunate by-product of suicidal

interpersonal communication. Their original idea is that an otherwise powerless individual, modally a young woman, may, at the extreme, threaten to or try to kill herself as the only available means by which she can induce kin to attend to her honest genetic needs. It may be in her reproductive interests to make a potentially high-stakes gamble, informed unconsciously by an inclusive fitness calculation. Suicidal death, from this perspective, can be seen as an unfortunate gamble lost. The behavior posited to be adaptive is the threat of, or attempt at, suicide; the potential for death being necessarily concomitant for the threat to be credible (Wiley, 2020). A recent variation of the idea, also with the inherent risk of a lethal, maladaptive outcome, is that a suicide attempt may constitute a costly signal of remorse (Syme and Hagen, 2018). Perhaps this line of theorizing may usefully shed light on non-suicidal self-injury and unintended fatalities, both outside the scope of this discussion. Researchers have long hypothesized a “cry for help” component in sub-lethal self-harming behaviors (Shneidman and Farberow, 1961), phenomena which may be significantly distinct from suicide (Kapur, Cooper, O’Connor and Hawton, 2013; Selby et  al., 2014; Stengel, 1970). Among the chronically suicidal, it is possible that a cycle of reinforcement may arise in which carers’ well-meaning responses inadvertently provoke yet more behavioral cries for help (Linehan, 2020). There may also be strong commonsense appeal in attributing suicide to communication. There is an important caveat in this regard: folk theorizing about the cause of suicides is evidently not an objective data source. It is rather, at least in large part, a product of encultured post-rationalization (Atkinson, 1978; Solano, Pizzorno, Pompili, Serafini and Amore, 2018; Soper, 2019a). For example, alongside communication-type explanations, and presumably as reliably, non-western informants often also blame suicides on evil spirits, as Syme et al. (2016) themselves found. Observers frequently intuit


interpersonal motives for attempted suicides too, but it should be born in mind that these interpretations rarely agree with actors’ own explanations: and where they do agree it may be because surviving attempters sometimes confess motives that they think others expect to hear (Bancroft et  al., 1979). All that said, we question whether communication offers a satisfactory evolutionary explanation for intentional self-killing, partly for the same reasons that we found more directly adaptationist models wanting. We will highlight two difficulties (a critique may also be found in Soper (2018)). The first problem recalls the hallmark of adaptation: evidence of special design (Williams, 1966, 1996). It is an intuitive call, but suicide, whether completed, attempted or threatened, does not strike us as likely custom-designed for communication. People who seriously intend to take their own lives, presumably against kin’s wishes, would logically be expected not to communicate that intent, at least not sufficiently to invite interference. With rare exceptions, the empirical picture seems to fit this expectation. Perhaps it is different in some parts of the world – most of the evidence is from Western sources – but suicides are usually characterized by non-­ communication: privacy and non-disclosure are the norm. That they tend to happen without effective warning may be inferred from relatives’ immediate reaction to the news: typically shock, confusion, and disbelief (Chow, 2006; Dyregrov et  al., 2012). Far from registering a communicated message, bereaved families are generally left bewildered by the act’s apparent senselessness (Jordan and McIntosh, 2011; Wertheimer, 2014). Noncommunication is characteristic of attempted suicides too (Maple et al.). Where an attempt is survived, close kin are usually not told about it either before or after the event, and they usually remain unaware even long afterwards (Brezo et  al., 2007; Walker et  al., 1990). At the same time, one can imagine any number of other deviances, potentially costly but not ordinarily suicidal, available for use if a drastic


threat or costly signal were needed: desertion, sexual infidelity, self-mutilation, infanticide, sabotage, arson, and so forth. In sum, it is not clear that suicide constitutes an outstandingly good solution to the needs of coercive, or any other, communication. The other difficulty recalls, again, the extreme and predictable fitness penalty of a suicide attempt, whether lethal or survived (Table 3.1). It is hard to imagine a commensurately extreme and predictable fitness benefit that could, even in theory, be won from a suicidal communication. Empirically, the epidemiology shows no obvious pattern of net fitness gains. Lesser upsides offered as supporting evidence in Syme et al.’s ethnographic analysis (2016, supplementary material, table S3) seem to fall well short in specificity (e.g., ‘Manipulate parents’) and reproductive impact (‘Prevented unwanted ear modification’) to be plausibly sufficient, as biological prizes, to justify the fitness losses and risks taken in trying to kill oneself. The strongest claimed payoffs are cases where actors are alleged to have sought sexual concessions, such as ‘Prevent unwanted marriage’ and ‘Concubine moved out of house’ – psychologically appealing, no doubt; but in a fitness calculation, still not credibly worth dicing with genetic extinction for their sake. If there is not a plausible net fitness gain to be had from going through with a threat, then it is unclear on what fitness grounds such a threat would be accepted as being credible. This is not to say that there may not be social utility in threatening to kill oneself, or any other threat for that matter. The error, we suggest, is to confuse non-evolutionary and evolutionary processes – to confuse utility with biological fitness. Stepping back, we question a general assumption that underlies hypotheses discussed so far, that the fitness payoff of whatever process it is that produces suicide derives from the suicide behavior itself. In principle, pleiotropy does not require there to be any obvious connection between a selected trait and its noxious concomitants (Williams, 1992). The explanatory gap between suicide’s



hypothesized benefits (weak, and contingent) and evident costs (severe, and predictable; Table 3.1) suggests that we probably need to look beyond the act itself for a categorically more powerful biological impetus. With this in mind, we will next look at some prominent evolutionary ideas circulating in mainstream suicidology.

The Interpersonal–Psychological Theory of Suicide (IPTS) Another conceptual framework, the Interpersonal–Psychological Theory of Suicide (IPTS), deserves attention. In various formulations it may currently be suicidology’s most prominent theory (Hjelmeland and Knizek, 2019; Lester, 2019; Paniagua et  al., 2010), and it explicitly draws on some evolutionary ideas, including the notion that suicide may have come about as an evolutionary byproduct. In its original form IPTS holds that suicide results from the co-occurrence of three supposedly sufficient conditions: (1) a perception of being a burden to one’s family, (2) a thwarted desire to belong, and (3) a learned capability to enact lethal self-injury (Joiner, 2005; Van Orden et al., 2010). We will discuss each in turn. The first element, a feeling that one is a liability to loved ones, has been mapped by some commentators onto deCatanzaro’s (1980) sociobiological idea of burdensomeness – critiqued earlier – to which suicide is allegedly the organism’s genetically adaptive response (Aubin et al., 2013; Brown et al., 2009). But in what they call a ‘sociobiological extension’ of their own theory, IPTS’s authors depart from deCatanzaro’s view of burdensomeness in that they posit (human) suicide to be intrinsically maladaptive: colonial insects and humans are said to be equivalently eusocial, but while lethally self-sacrificial behaviors are understood to have inclusive fitness logic for insects, supposedly the same response among humans is seen as an error – a ‘dysfunction, misfiring, or derangement

of the adaptive behavioral suite evolved as a facet of eusociality’ (Joiner et al., 2017: 71). Evolutionary rationale for this distinction isn’t provided, but the need to make a distinction seems to stem from the authors’ equating of insect and human sociality – a questionable premise given the special familial makeup of insect colonies noted earlier. Adding to the confusion is what appears to be a mixing of biological process and moral evaluation (Gorelik and Shackelford, 2017) something that has long colored scientific discourse in this field (Soper, 2019a; Zilboorg, 1936a). IPTS’s second element, thwarted belongingness that may motivate self-killing, is on firmer theoretical ground and is where suicide is envisioned explicitly as a dysgenic byproduct (Joiner, 2005; Van Orden et al., 2010). The aversiveness of rejection, abandonment, and similar interpersonal stressors has certainly been attributed to evolutionary origins: psychological pain probably functions as an ancient alarm system, warning of potentially fitness-damaging social losses (Baumeister and Leary, 1995; Bowlby, 1969/1997, 1973, 1980/1991). Suicide can be understood as a way to escape from this adaptive social distress. We will return to this idea. Less strong in its theoretical underpinnings is the third component of IPTS, a hypothesized learned capability for lethal self-injury. The idea derives from a centuriesold belief that suicide defies an ‘instinct for self-preservation’. This supposedly universal natural drive must be overpowered, IPTS’s authors claim, before suicide can be carried out (Joiner, 2005; Van Orden et  al., 2010). IPTS’s originator, Joiner (2005), ascribes evolutionary credentials to an ‘instinct for self-preservation’, but the notion faces principled objections from evolutionists, not least because there is no known biological means by which such a superordinate drive could come about (Kirkpatrick and Navarrete, 2006; Soper, 2019a). Modern theory holds that a general-purpose motivational device would be underspecified, lacking the recurring connections between proximal


stimulus and fitness-impacting response that are required for selection to take hold: a system without specific links between inputs and outputs is unlikely to be favored (Buss, 1990; Buss and Penke, 2015). The same difficulty, it will be recalled, arose above in discussions of an ‘inclusive fitness monitor’. Soper (2016, 2018) suggests that if an antisuicide mechanism were reconceived within the tenets of evolutionary psychology, as a special rather than general-purpose device, then useful implications follow. We will come back to this point as well.

Suicide as an Escape from Pain Pyschological pain may drive the phenotype to seek relief in a way that is destructive for the genotype. We saw this idea underlying IPTS’s second component (above), and indeed it can be traced to suicidology’s formative writings. In the words of Henry A. Murray (the clinician whom Edwin Shneidman, the acknowledged father of suicidology, saw as his mentor), Suicide does not have adaptive (survival) value but it does have adjustive value for the organism…it abolishes painful tension. (Murray and Kluckhohn, 1948: 15, original italics)

By this perspective, suicide offers escape (Baechler, 1975/1979; Baumeister, 1990; Shneidman, 1993, 1996, 2005). A related idea, but with much older philosophical roots, is that self-killing may be a rational response to difficult life circumstances (Maris, 1982; Mishara, 2003). General reviews are available elsewhere of ‘suicide as escape’ theories (Gunn, 2014) and rational suicide (Lester, 2014a). Of interest for our purposes is their recognition, implicit or explicit, of the suicidogenic power of emotional pain (Selby et al., 2014). There are two points to note. First, although pain systems can malfunction, pain almost certainly has ancient adaptive origins (Nesse and Schulkin, 2019). Pain’s signal


enables the organism to navigate fitness hazards in its environment, both physical (Wall, 1999) and, as we have already noted, social (MacDonald and Leary, 2005). And in order to fulfil its navigation task, pain is necessarily motivational: it is designed precisely to force the organism to take action to relieve it (Auvray et al., 2010; Corns, 2014; Melzack and Casey, 1968). Hence, pain hurts. As the leprosy surgeon Paul Brand observed, pain is a valuable gift, albeit a gift nobody wants (Brand and Yancey, 1993). Second, there is an accord among suicide theorists and empirical researchers about the kind of pain that most powerfully motivates action – whatever action – to obtain the required relief. Although physical pain also associates with suicidality (Klonsky et  al., 2019; Klonsky and May, 2015), emotional pain is more usually held responsible. The unbearable emotional state that can induce people to take their own lives is encapsulated by Shneidman’s (1993) neologism, psychache: Psychache refers to the hurt, anguish, soreness, aching, psychological pain in the psyche, the mind. It is intrinsically psychological – the pain of excessively felt shame, or guilt, or humiliation, or loneliness, or fear, or angst, or dread of growing old or of dying badly or whatever. (1993: 51; original italics)

There is also implicit agreement across more than a century of suicide research that unbearable emotional pain usually stems from social troubles. The disagreement is rather about what hue of social trouble is deemed most troublesome. Durkheim (1897/1952), for example, cited detachment (‘anomy’) as the chief driver. A hundred years later, Williams and colleagues ascribe suicide to feelings of social defeat and entrapment (Williams, 1997; Williams and Pollock, 2000; Williams et  al., 2005). Williams’ ideas reappear in another theoretical framework, one that rivals IPTS, the Integrated Motivational–Volitional Model of Suicidal Behavior (IMV) devised by O’Connor and colleagues (O’Connor, 2011; O’Connor et  al., 2016). IPTS, it will be recalled, highlights yet other varieties of



interpersonal distress – thwarted belonging and burdensomeness. And so on. Gunn (2017) connects these threads in an explicitly evolutionist frame; his Social Pain Model (SPM) registers that suicidogenic psychache is usually activated by various forms of damaged or threatened social relations. This social pain, as with pain generally, is both adaptive and intrinsically aversive. It is adaptive in that it is designed to alert the organism to the fitness threat posed by detachment – rejection presaging near certain death for our hunter-gatherer forbears (Bjorklund et  al., 2010; Eisenberger and Lieberman, 2004; Eisenberger et  al., 2003; Lieberman, 2013). And social pain is necessarily painful in order to induce action to alleviate it. Unfortunately, suicide offers a genetically self-destructive answer to this biological imperative to act. In sum, a weight of empirical and theoretical evidence points to suicide instantiating as an unfortunate by-product of pain, notably social pain, this being integral to the navigational equipment that humans need for maintaining attachments in large and close-knit groups. The aversiveness of social pain, adaptively, demands action to end it – a demand that can be met maladaptively by self-extinction.

‘Pain-and-Brain’ Model But social pain alone cannot be sufficient explanation for the evolution of suicide. If it were sufficient, suicide would presumably be found elsewhere among primates and other higher social animals. Indeed, solitary animals would expectably be vulnerable too: to reprise the point, pain (social or other) is biologically designed not to be tolerated – it demands that the organism act to end or escape it – so, any animal that could terminate its pain by terminating itself would reasonably be expected do so (Perry, 2016; Soper and Shackelford, 2018). We are still searching for an explanation for suicide as a narrowly human response. The search space

is even narrower than this because, as well as nonhumans, certain human populations too are protected from taking their own lives, however painful their circumstances: young children (Nock et  al., 2013; Shaffer, 1974) and the mentally incapacitated (Merrick et al., 2006; Seyfried et al., 2011). Their immunity, or virtual immunity, also needs to be accounted for. Noting commonality across these groups, Baechler (1975/1979) draws a parsimonious conclusion that deliberate selfkilling presupposes a minimum level of intellectual functioning. Soper (2017, 2018) concurs, arguing that it’s only after more than a dozen years of cerebral development that species-typical humans, and apparently only humans, acquire sufficient capacity for logical thinking, foresight, and planning, for suicide to become a conceivable and practicable response. Humans alone appear to cross what Perry (2014: 110) describes as a ‘cognitive “floor” for suicide’, usually in adolescence. Thus, a second necessary condition for suicide emerges: cognitive competence. This may be central for understanding the behavior’s evolutionary origins. If deliberate self-killing presupposes the crossing of a developmental threshold during the individual’s lifetime, then we can deduce that an evolutionary counterpart, a phylogenetic threshold, also had to be surpassed at some point in human prehistory. Humphrey (2011: 211) makes the point by quoting Stengel (1970: 37)… At some stage of evolution man must have discovered that he can kill not only animals and fellowmen but also himself. It can be assumed that life has never since been the same to him.

Humphrey (2018) goes on to ascribe this pivotal discovery to the arrival, around 100,000 years ago, of a suite of uniquely human cognitive skills, including abstract thinking, mental time travel, self-consciousness, and sophisticated theory of mind. These are virtuoso demonstrations of the flexible, general-purpose style of thinking of Homo sapiens sapiens – promiscuous intelligence favored by selection because it conferred potent ecological, social,


and sexual advantages (Flinn and Alexander, 2007; Humphrey, 1976; Pinker, 2010; Tooby and DeVore, 1987). But the human brain is ‘expensive tissue’ (Aiello and Wheeler, 1995): encephalization brought with it heavy costs, including energetic demands (Aiello and Wheeler, 1995), mutational load (Keller and Miller, 2006), obstetric challenges (Miller and Penke, 2007), problems of thermoregulation (Falk, 1990), and the burden of supporting young while the brain matures (Flinn et  al., 2007). Suicidality can be understood as another such cost, a price we pay for a mind so free ranging that it can conceive even of its own mortality (Bering and Shackelford, 2004; deCatanzaro, 1980; Soper, 2018; Suddendorf, 2013). To sum up, it appears likely that suicide evolved as a by-product of not one adaptation, but two combined: pain (usually social); and speciestypical human cognition. Soper calls this a pain-and-brain theory of suicide.

Suicide as an Adaptive Problem The above discussion suggests that scientific consensus, if loose and implicit, can be seen coalescing around some form of ‘by-product’ explanation for suicide’s ultimate origins. A pain-and-brain framework in particular does not appear contentious: it seems to offer a point of agreement among prominent suicide theories, it accords with the epidemiology of suicide, and connects to knowledge bases of neuroscience, anthropology, and elsewhere. But it raises new and difficult questions, mainly because, as Soper (2016, 2018, 2019a) infers, the posited pain-and-brain conditions are not only necessary for suicide, but logically sufficient: pain provides the motive, and mature human cognition provides the means. If the pain-and-brain assessment is correct, then the fitness threat of suicide exists in potentia among virtually all of us. All speciestypical humans feel, and are motivated to escape, pain (Benatar, 2015; Brand and Yancey, 1993); and all species-typical human


adults, equipped with much the same cognitive machinery (Tooby and Cosmides, 1990a), have self-removal available as an exit route from pain. A consequent ‘lure of death’ (Humphrey, 2018) has probably featured in our evolutionary environment at least since the advent of behaviorally modern humans. Perhaps for much longer – presumably, indeed, ever since hominid intelligence began to approach that of a modern-day pubescent child (Soper, 2019b). By implication, suicide presents a harmful variety of, in evolutionary parlance, adaptive problem: Adaptive problems are evolutionarily long-enduring recurring clusters of conditions that constitute either reproductive opportunities (e.g., the arrival of a potential mate, the reflectant properties of light) or reproductive obstacles (e.g., the speed of a prey animal, the actions of a sexual rival, limited food supplies for relatives). (Cosmides and Tooby, 2000: 96)

Adaptive problems seek out adaptive solutions (Mayr, 1965; Tooby and Cosmides, 1990b; Williams, 1996). That almost all adults could be expected to take their own lives, but few do, indicates that adaptive solutions to the suicide problem are in fact in place. Without them, we as individuals, and we as a species, would not be here. At a phylogenetic level, hominid evolution would not have found a way through the cognitive floor for suicide, the floor acting as a ceiling of viable intelligence: in this light suicide emerges as perhaps the pre-eminent adaptive problem of our species (Soper, 2019b). Our existence presents a puzzle not so much of suicide but non-suicide. What stops most of us killing ourselves?

Evolved Antisuicide Defenses In seeking to answer this question, why not suicide, we can set aside the pre-Darwinian notion of a general-purpose survival instinct – critiqued briefly above and more fully elsewhere (Buss, 1990; Buss and Penke, 2015; Kirkpatrick and Navarrete, 2006; Soper, 2019a).



The likely solution would look more like the customized ‘patch 7.822’ artificial intelligence fantasy that began this chapter (Perry, 2016). If a fleet of androids dealt with every difficulty by, uselessly, switching themselves off, the problem would call for a software update to eliminate that particular behavioral option. In actuality, the human brain, a biological computer (Tooby and Cosmides, 2005), has presumably been retrofitted with a comparable fix, devised by selection. We next need to ask: how would such a patch operate? And what would its successful operation look like? Two sorts of antisuicide programs have been hypothesized in recent years (Humphrey, 2018; Miller, 2008; Soper, 2016, 2017, 2018). The first are evolved psychological mechanisms (Buss, 1995); the second are culturally propagated barriers. There won’t be a neat dichotomy in reality because many evolved psychological mechanisms rely on cultural inputs (Tooby and Cosmides, 1992), and many cultural devices exploit evolved psychological preparedness for learning in their particular domains (McNally, 2016). Nonetheless the distinction is interesting – partly because, although both sorts of devices might be expected to emerge, there is disagreement over their likely chronology and relative importance. Humphrey (2018) reasons that psychological mechanisms (what he calls ‘natural’ or ‘innate’ protections) would not have arisen as the first or foremost protection because of their slowness to evolve. Soper (2018, 2019a) argues the contrary, that they probably came first, emerging at least in part during a reconfiguration of anatomically modern humans’ ‘wetware’ ahead of the cultural explosion of the Later Stone Age (Klein and Edgar, 2002). The evolution of human intelligence may have been held at the cusp of suicidality for perhaps 150,000 years or more, while largely autonomic solutions to the suicide problem were assembled and refined. The pressure favoring such solutions would have been intense due to a combination of forces: runaway selection pushing

for greater computing power (Geary, 2007; Miller, 2000), while intelligentsia who lacked adequate protection were culled. Soper posits that it was only after basic defenses were installed that human intelligence could progress to the level of being able to enculture antisuicide ideas, proscriptions which presuppose a capacity to conceive of personal mortality. It is possible to deduce something of the likely design features of antisuicide defenses, as we will next discuss, by adopting evolutionary psychology’s ‘task analysis’ method (Tooby and Cosmides, 1992) – inferring likely parameters of an adaptive solution from the nature of the adaptive problem. Soper (2018) suggests that, in view of the severity of the threat, antisuicide devices are probably arranged as serial fortifications, each line guarding the position behind and deploying special stimulus-response mechanisms to that end. Perhaps simplifying, he suggests a framework that splits into front and rear defenses. At the back are emergency interventions, labelled keepers to connote the primary role of a goalkeeper on a soccer team: on stand-by much of the time, keepers leap into ‘Save!’ mode at times of crisis, and are all that stands between an attacking shot and disaster. Front-line protections, in contrast, are continuously active: following the soccer analogy, Soper labels them fenders to suggest a team’s other defensive players. Fenders’ job is to stop crises arising in the first place. The default outcome, if players can’t fulfil their respective tasks, is a conceded goal – a suicide attempt – which, as noted earlier, may be genetic ‘game over’. Soper argues that defenses’ triggering inputs and behavioral outputs would be expected to address both of suicide’s dual pain-and-brain drivers, and in distinct ways. To borrow the soccer analogy again, the fitness hazard of suicide can be conceived as an opposing team with only two forward players, ‘Pain’ and ‘Brain’, and they pose a threat only when they attack together. They have distinct styles of play, and the defending team


must adopt customized pain-type and braintype tactics to neutralize them. Let us look first at the system design of keepers, the posited emergency defenses. To detect an imminent threat from ‘Pain’, keepers must be ready to respond to the experience of chronic and intense emotional distress. To detect an incoming ‘Brain’ threat, keepers must also be alert to the surpassing, in adolescence, of the cognitive threshold for suicide. Cues for both ‘Pain’ and ‘Brain’ must be present for keepers to mobilize. And, likewise, there are two, and only two, strategies available by which keepers can block incoming attacks: pain-type and brain-type. Pain-type keepers make self-killing unnecessary: they numb, distract from, or otherwise weaken the felt urgency of emotional pain as a motivator for escape. Brain-type keepers deny the means: they interfere with intellectual functioning enough usually to prevent an effective suicide attempt being organized. We will discuss keepers in more detail after this overview. The main point to note for now is that keepers’ interventions may be highly costly to the organism – and they are evidently not failsafe: hence the need for the pre-emptive work of fenders. As for fenders, the forward line of protections; these are hypothesized also to deploy in pain- and brain-type forms. Pain-type fenders titrate the organism’s exposure to emotional pain within tolerable limits. They use what could loosely be called positive psychology (Efklides and Moraitou, 2013) to hold humans safely distant, most of the time, from the potentially lethal danger that resides lop-sidedly in negative affect. Soper suggests they may work as four subsystems. First, is a homeostasis of affect around a resting point that is happier than neutral (Heintzelman and King, 2014), a base at which shocks can generally be absorbed without great disruption. Second, is a regulation of conscious contact with potentially painful realities – a self-serving self-deception that, empirically, characterizes so-called psychoanalytic (or psychodynamic) defenses (Paulhus and Buckels, 2012). Third, is a manufacturing


of positive affect (Kuhl et al., 2015; Layard, 2011) via, inter alia, investment in pleasurable activities beyond what would be economically justified by normal animalian needs of survival and reproduction (Pinker, 1997). And fourth, is the selection and maintenance of a hopeful, measuredly fictitious, mental model of self-in-the-world. This paradigm, more or less spiritual, holds that the universe and its people are not wholly indifferent to our wellbeing, and that our futures are not entirely doomed to the pain that would attend a purely Darwinian struggle. Thus, operating within (to adapt Baumeister’s (1989) phrase) an optimum margin of delusion, we perceive the world not as it is but through a rose-tinted lens. This enhanced reality system is under continual assault by factual counterevidence, and hence requires us continuously to defend it, literally as if our lives – or, at least, mental health – depend on it. Arising from this protective worldview, Soper says, is a costly propensity for selflessness and charity – that is, generosity that goes beyond the reciprocal calculus of economics. Taken as a whole, these sundry irrational-looking morale-boosters are not easy otherwise to explain and connect, but they may be understood to work as integrated psychological machinery, designed to prevent crises of willful self-destruction and the necessity for keepers to intervene. A separate set of evolved, culturally learned protections, independently hypothesized by Miller (2008), Humphrey (2018), and Soper (2018), are designed to block access to the idea of suicide. They are brain-type fenders in Soper’s scheme. He suggests they propagate by multi-level selection and form three serial walls: a thought-inhibiting taboo; the expectation of a fearful afterlife; and a moralistic stigma. The deterrent function of this last barrier, unfortunately but perhaps necessarily, involves exemplary punishments for suicides and their kin, some noted in Table 3.1. The dismantling of these prohibitions, the acceptance of suicide as a normal topic of conversation and a reasonable solution to trying circumstances, can release a surge of



suicides (Huber, 2015/2019). Such a wave may perpetuate for generations (Macdonald, 2007): once lost, cultural defenses may be exceptionally difficult to reinstate (Soper, 2018).

A summary graphic (Figure 3.1, from Soper, 2018) illustrates how the various posited protections may interrelate. Out of a great number of potential suicidal incidents, symbolized

Figure 3.1  Summary of posited antisuicide defences Source: Reproduced from Soper (2018).


by a mass of dots at the top of the diagram, only a few find their way through the fortifications to materialize as actual suicide attempts, indicated by a couple of dots at the bottom. By focusing not on supposed (possibly inscrutable; Soper, 2019a) proximal causation of suicide but on evolved machinery posited to stop suicide, the graphic departs conceptually from the style of flow chart that usually accompanies presentations of suicide theory (Gunn, 2019).

PREDICTED FEATURES OF ‘KEEPER’ LAST-LINE ANTISUICIDE DEFENSES This section focuses on Soper’s (2018) task analysis for keepers – the hypothesized last line of defenses, which react to exigent risk. These ideas are novel, and not mainstream in either suicidology or evolutionary psychology, but we suggest they warrant attention for three reasons. First, their claim to logic – keepers’ design features being supposedly deducible a priori from the nature of suicide as an adaptive problem – is central to the theory and calls for scrutiny. Second, these features may be read as predictions, amenable to empirical confirmation or falsification. Third, if correct, they may have important repercussions for suicide prevention, psychiatry, and wider mental health policy, as we will discuss. Keepers’ posited features are presented in 20 items, (a) to (t) below, the headings taken from a tabulation in Soper (2018: 145).

‘Pain’ Input With suicide modelled as an answer to the imperative to escape pain, Soper argues that the emotional aversiveness of pain would probably serve as the primary activator of emergency antisuicide defenses. Keepers would mobilize selectively among people in potentially suicidogenic distress.


a. Keepers would be activated by chronic, intense pain (subject to the developmental condition of a ‘brain’ input). Soper predicts that an activating ‘pain’ cue will combine (by some unspecified algorithm) pain’s chronicity and intensity. Chronicity, on the grounds that suicides take time to plan and enact (Joiner, 2005),4 so potentially drastic countermeasures should not be triggered by merely ephemeral upsets. Intensity, because the stronger the pain, presumably the more urgent the motivation to escape it. An additional ‘brain’ input is set out in (d) below. b. Input variable would be the unidimensional aversiveness of pain, regardless of the pain’s source or quality. Because the pain-and-brain model views suicide as an adjustive response to the generic aversiveness of pain, irrespective of its origin, keepers will respond to the degree, not kind, of triggering pain. The point recalls Shneidman’s (1993) catch-all notion of suicidogenic psychache; that any blend of shame, grief, anomy, thwarted belongingness, burdensomeness, defeat, hopelessness, or whatever other emotional distress can motivate suicidal escape. Soper (2018) posits that, likewise, any combination can trigger an antisuicide defense. Social pain is more likely to activate keepers than is physiological pain only inasmuch as social pain is often experienced as more painful (Gunn, 2017). c. Keeper responses would be calibrated so that the intensity of defensive outputs accords with the intensity and chronicity of the pain input. The strength of antisuicide responses would be expected to adjust according to the scale of the threat: more intense and longer-lasting distress should associate with commensurately more robust countermeasures.

‘Brain’ Input d. Keepers would not activate earlier than the species-typical age of first onset of suicide, in early adolescence, possibly signaled by the onset of puberty. As already noted, activation would presumably need a threshold ‘brain’ condition to be met, linked to developmental surpassing of the cognitive floor for suicide. Because young children lack the mental capability for suicide, there would be no fitness benefit in keepers mobilizing among them however distressed they may be. Soper (2018)



stops short of specifying how this ‘brain’ cue operates; but he posits that a biochemical signal connected with pubescence is probably involved because, empirically, it is usually at or shortly after this stage of life that suicide becomes enactable. Interesting predictions may follow from this developmental association, as we will discuss later.

Deactivation e. Keepers would demobilize spontaneously following a reduction in the originating pain input. Mirroring activation, keepers should deactivate after, and only after, relief of the potentially suicidogenic pain that activated them. f. Deactivation would usually be slow, gradual and delayed, especially without an unambiguous ‘all clear’ signal. Antisuicide defenses would work on a ‘better safe than sorry’ principle, deactivating slowly for the same reason that prey mammals, on high alert after scenting a predator, stand down only cautiously once the scent disperses: the extreme potential cost of misreading an ambiguous ‘all clear’ outweighs the cost of remaining too long on guard (Blanchard, Griebel, and Nutt, 2011).

Specific Types of Keeper Responses g. Responses would aim to limit motivation for suicide (‘pain-type’); or limit the capacity to organize suicide (‘braintype’). It was noted earlier that keepers are predicted to block suicide by deploying ‘pain’ and ‘brain’ strategies, a dual process deducible, Soper (2018) argues, from suicide’s posited pain-and-brain evolutionary causation. He offers suggestions as to what these interventions may entail, listed as bullet points in the ‘keeper’ boxes towards the bottom of Figure 3.2. Ellipses indicate that the lists may not be exhaustive.   The first category, pain-type keepers, are tasked with lessening the aversiveness of emotional pain. Given the neurological overlap between physical and emotional pain (Eisenberger and Lieberman, 2005), Soper (2018) hazards that keepers would probably co-opt pre-existing circuitry that moderates the felt intensity of physical pain (Wall, 1999). Pain-type keepers might, for example, numb emotions autonomically in a manner akin to the analgesic effect of physical

trauma. They could also manage pain exogenously: by, say, ingestion of analgesics – exploiting ‘nature’s pharmacy’ as animals do (Engel, 2002); by exploiting the phenomenon of pain-offset relief, in which one pain can be relieved by applying another, unrelated, stimulus; and/or by distraction (Eccleston, 2001). Other pain-type keepers are posited to use psychological adjustments to make pain bearable, such as the construction of a rationale for suffering pain and/or an emotionally tolerable, but partly imaginary, re-perception of the environment (Eccleston, 2001).

The other category, brain-type keepers, deny the means and opportunity for suicide. They will attenuate the individual’s ability to plan and implement suicide (and, incidentally, any other complex task) by tactically disabling psychomotor and executive resources. Activation would expectably express inlethargy and/or targeted cognitive deficits, such as indecisiveness and forgetfulness.

General Characteristics of Keeper Responses h. Keepers would drive compulsive and involuntary behaviors, resisting conscious awareness and intervention. Suicide being the kind of lethal, once-in-a-lifetime, fitness threat that offers few opportunities for conditioned learning and where to err can be fatal, it ought to be addressed by preset and strongly obligate routines. Keepers would present limited scope for being voluntarily moderated. Indeed, the phenomenon of instinct blindness prevailing (Cosmides and Tooby, 1994), they may operate beyond awareness. i. Multiple forms of keepers are likely to operate in an integrated fashion in the same individual, concurrently and/ or temporally. Blends of pain- and brain-type defenses would likely deploy in combinations in the interest of system robustness and to spread costs. In principle, keepers could appear in many possible permutations, varying from person to person and over time, responding to the varying needs of culture, gender, life stage, personality, and other aspects of individual difference. j. Keepers are likely to be accompanied by protracted anxiousness, and rumination focused on emotional pain. As a point related to (f) above, following the general pattern by which


animals respond to severe but uncertain fitness threats (Blanchard, Griebel and Nutt, 2011), humans at risk of suicide would expectably display prototypical anxiety. Recalling the analogy of prey mammals scenting an unlocatable predator, their best strategy is not flight, because they would as likely head towards death as away from it. For humans vulnerable to suicide, lethal danger similarly comes from no discernible direction and there is likewise nowhere to run. The priority in the presence of such an extreme, ambiguous hazard is to stay on high alert and try to infer its detail ‘beyond the information given’ (Waldmann et al., 2006). By this light, a compulsive mental rumination, which may be a uniquely human addition to what is otherwise a pan-­ animalian anxiety state (Blanchard, Griebel, Pobbe et al., 2011), would be an expectable response.

Goals and Trade-Off Considerations k. The compromise objective would be to minimize the risk of suicide, while limiting the imposition of new, potentially drastic, fitness costs arising from activated keepers. Keepers are necessarily costly to activate because they involve attenuating the advantageous-on-average ‘pain’ and ‘brain’ primary adaptations that brought suicide in their wake. Keepers have evidently not delivered zero suicide risk, and would not be expected to do so, because zero suicidality would presumably be achievable only by commensurately zeroing the fitness benefit of those adaptations. Rather, antisuicide defenses would evolve only up to an equilibrium; a point where the marginal fitness gain to be had from further reducing actuarial risk matches the cost of the extra defenses required to achieve that reduced risk. l. Keepers would trigger sensitively, with a high incidence of false alarms – many affected individuals will not have considered suicide. As with the posited ‘brain’ cue, Soper does not specify the ‘pain’ input that is hypothesized to mobilize keepers. Candidate triggers would presumably include biochemical correlates of pain. But they would probably not include, despite its appealing specificity, conscious planning of suicide projects. The informational currency of the brain being emotional rather than semantic, the organism’s central nervous system would be oblivious to suicide plans unless they


were flagged as such by an emotional regulatory variable (Tooby and Cosmides, 2008). Soper (2018) hypothesizes the existence of separate defenses that deter suicide plans by using the disgust mechanism, informed by culturally learned inputs (so-called brain-type fenders, discussed above). But he suggests that there may be no preprogrammed biological tag marked ‘Suicide Plan’ to which keepers could respond. Commonplace experience is that one can muse about suicide without triggering a drastic autonomic response. On this basis, keepers may not be good at differentiating, from among emotionally distressed people, those who have specific suicide plans from those who don’t. Keepers would likely mobilize in some individuals who, although in pain, may never have entertained serious thoughts of taking their own lives. Keepers erring on the side of caution ((f), above), there may be many such false alarms. m. Keepers may themselves become pathological. In the same way that the physiological immune system can malfunction, there may be exceptional situations in which keepers may become pathological. Soper posits the possibility, for example, that antisocial behavioral outputs of keepers, mobilized in response to social pain, may invite more social pain, potentially creating a positive feedback loop.

Manifestations of Successful Operation n. Keepers would result in a low, but abovezero, incidence of suicide in human populations. It follows from keepers’ compromise objective ((k), above) that their success would appear at a population level not as zero suicides but as a minimal, biologically irreducible, residue. Pockets of high, even demographically destabilizing, rates of suicide might arise, but these would be short-lived and in due course supplanted, through multi-level selection, by groups with suicidality held at sustainable levels.5 o. Residual suicides would be intrinsically unpredictable at the level of the organism. Functioning optimally as part of a wider system of antisuicide defenses, keepers would be expected to exploit and exhaust any and all useful markers of actuarial risk. The few suicides that do occur, it follows, can be viewed as statistical residuals – suicidal trajectories that are amenable neither



to detection (not, that is, based on informational priors available to the organism) nor, therefore, to autonomic prevention. With keepers operating properly, suicides should be ‘predictably unpredictable’ (Soper, 2019a). p. Activated keepers would be associated with suicide, but only inasmuch as they associate with suicidal ideation rather than with the enacting of those ideas. Most suicides would expectably be accompanied by activated keepers. Interesting predictions arise from (k) and (l) above concerning statistical associations between suicidality and activated keepers. Completed suicides will likely be accompanied by signs of keepers having activated – properly, although in these instances ineffectively. Keepers should also correlate strongly with suicide plans and actions. But, importantly, these correlations should hold only insofar as keepers correlate with the emotional prior – a generalized urge to terminate pain. By analogy, one could imagine a warring city that defended its centre against aerial bombardment with less-than-perfectly effective anti-aircraft guns deployed at the city’s outskirts. Gunners open fire pre-emptively; they start shooting as soon as bombers come within range. Hence, gunfire would correlate strongly with bombing of the centre, but only inasmuch as the outbreak of gunfire correlates with bombers approaching the outskirts – not especially with any surviving bombers’ completion of their raids, progressions which the gunners are trying to avert. Likewise, keepers will respond only weakly, if at all, to the pursuit of specific suicide projects among people motivated to end their suffering, this being the progression that keepers are designed to prevent. q. Keeper responses would be nearly always recoverable and survivable: they should only rarely cause permanent disability. Almost any outcome short of death being preferable to suicide, keepers’ interventions may be extreme. Nonetheless, as immune-like responses, they should usually not be degenerative. A protective denial of psychomotor energy, for example, would expectably produce tactical lethargy, perhaps for a while even complete immobility, but it should not seriously compromise somatic functions. r. Keeper responses would be nearly always recoverable and survivable: they should only rarely cause permanent disability. Because the pain-and-brain framework

views suicide as a dysgenic, but ­psychologically rational, response to aversive affect, activated keepers can be understood as tactical denials of rationality – they sacrifice aspects of the organism’s affective (‘pain’) and cognitive (‘brain’) functioning in order to preserve life. People under the influence of activated keepers will find themselves not only distressed, but also emotionally (‘pain’) and intellectually (‘brain’) debilitated. Faced with this inconvenience, sufferers and their families would be expected to approach priests, healers, and the like for explanations and remedial interventions. It can be expected that keepers’ expressions are conspicuous and probably well known to science, and we may not need to look far to find evidence of them.

Species-Specific and SpeciesUniversal s. Keepers would be species-specific: they would not occur in nonhuman animals, although homologue of their features may be found in other mammals. Keepers’ style of response contrasts with the way animals normally meet severe fitness hazards: just when any other animal would be expected to bring all its mental resources to bear on tackling a mortal threat, humans facing the threat of suicide are likely to find their affective and cognitive faculties autonomically impaired. Keepers are a uniquely human solution to a uniquely human problem. Rudimentary precursors of their features may well be found in nonhumans, particularly among other primates, but these will be only vestiges of phylogenetic raw material that was co-opted and adapted for antisuicide purpose in our species alone. t. Keepers would be species-universal: the same integrated system of keepers would be found activating among populations of mature humans in all cultures and historical ages. Keepers are genetically transmitted, species-typical mechanisms. Although the proximal cause of precipitating social pain will likely vary according to cultural context, the same suite of antisuicide responses to that pain will be found in all sizeable human populations. That said, as universal human features, keepers’ antisuicide functionality may not be obvious because no extant control population may be to hand to show what the suicide rate would be, all else equal, were it not for their interventions.


PSYCHIATRIC SYMPTOMS AS ANTISUICIDE DEFENSES The above section outlined an engineering specification – a score of features that would be expected of so-called keepers, reactive devices designed to stop us taking our own lives when we otherwise might. The specification follows, Soper (2018) argues, from the pain-and-brain model of suicide’s evolution; defensive systems would activate with ‘pain’ and ‘brain’ informational inputs, respond using ‘pain’ and ‘brain’ processes, and produce observable ‘pain’ and ‘brain’ outputs. The predicted features of this system show striking similarities, according to Soper, with adult patterns of so-called ‘functional’ (i.e., not due to structural brain dysfunction, as opposed to ‘organic’) common mental disorder, or CMD (Goldberg and Goodyer, 2005) – sundry states that would usually be described as depression, generalized anxiety, alcoholism and other addictions, psychoses, obsessive/ compulsive disorders, non-suicidal self-harm, and perhaps other diagnoses. He asserts that the fit is so detailed and multi-faceted that it is difficult plausibly to explain, except by the proposal that CMD is, in fact, the expression of antisuicide machinery. The hypothesis challenges a widespread preconception that CMD causes suicide, rather than works to block suicidal trajectories among those at risk (Mishara and Chagnon, 2016). To ascribe suicide to CMD may be to commit the post hoc fallacy: to assume that because a preceded b, a must have caused b. Recalling the analogy of air defences, ill-informed citizens might understandably misplace blame for the bombing of their city on the anti-aircraft gunfire that usually foreshadowed it. The challenge is not new: it has long been suggested within psychiatry that depression, addictions, psychotic delusions, and diverse other psychopathologies can protect against self-killing (e.g., Hendin, 1975; Himmelhoch, 1988; Hundert, 1992; Menninger, 1938). What is new is evolutionary theory that predicts such a dynamic.


We note four interesting ways to inspect the hypothesis. First, it offers a novel conception of ‘functional’ psychiatric diagnoses, as the concurrence of potentially suicidogenic pain alongside blends of antisuicide responses to that pain. Soper (2018) offers a cross-­ tabulation (Figure 3.2) to illustrate how psychiatric labels may describe various groupings of keepers in this way, with equivalent defensive components appearing under different diagnostic headings. Protective emotional numbing, for example, maps against criteria used for diagnosing ‘major depressive disorder’, ‘psychotic disorders’, and ‘bipolar disorder’. According to this conception, keepers, not diagnoses, are natural kinds. Second, the hypothesis may offer parsimonious explanation for a suite of statistical links between suicidality and CMD which, without the hypothesis, look unrelated and puzzling. We note three. One is that almost all CMD diagnoses associate with a heightened vulnerability to suicide (Cavanagh et al., 2003) – but, signally, the diagnosis of severe to profound intellectual disability associates with fewer suicides (Harris and Barraclough, 1997) as the pain-and-brain model would anticipate. Two is that, as predicted, CMD correlates with suicide only inasmuch as it correlates with the ideational prior. CMD associates strongly with generalized suicidal ideas; but only weakly, if at all, with the progression from this ideation to the planning and execution of specific suicide actions (Klonsky et al., 2016; Nock et al., 2015). Three is that the developmental stage when CMD tends first to appear – in the teen years (Kessler et al., 2007) – coincides with earliest first onsets of suicidality (Nock et al., 2013). It is not easy otherwise to account for these correlations individually let alone as a set. Together they could be taken as a fingerprint of antisuicide functionality. Third, the existence of marked patterns common to sundry diagnostic labels point to a shared aetiology – specifically, it is suggested, as mechanisms designed to prevent potentially suicidogenic pain and suicidal ideas

• Compulsive use of analgesics and other mind-altering substances (ii, iv, v, vi, vii)

Substance use disorders

• Indecisiveness; • Compulsive use diminished ability to of sedatives think or concentrate (viii) (viii, ix) • Loss of interest in activities; fatigue, loss of energy, hypersomnia; psychomotor retardation; loss of appetite (ix)

• Feeling ‘empty’; ‘Having no feelings’; ‘Not caring any more’ (i) • Craving foods (iv)

Major Depressive Disorder

Non-suicidal self-injury (NSSI)b

Psychotic disorders

• Difficulty concentrating; mind going blank (viii) • Fatigue (ix)

• Disorganised thinking; Disorganised/ abnormal motor behaviour (viii) • Negative symptoms; catatonia (ix)

• Worry, • Self-injury • Diminished rumination (iii, iv) emotional restlessness; expression (i) insomnia (vi, vii) • Delusions; hallucinations (iv, v, vi, vii)

Generalised Anxiety Disorder(GAD)a

Diagnostic criteria of some common psychopathologies (A.P.A., 2013)

Bipolar disorders

• Obsessions • Depressive (viii); episode (viii, ix) • Compulsions (ix)

• Obsessions; • Depressive compulsions episode (i) (iv, v, vii) • Manic/ hypomanic episodes (iv, vii)


Notes: a The anxiousness of generalised anxiety disorder may be better understood as a concomitant of keepers rather than a keeper defence in itself, but the pain-type function of GAD posited here might be taken to express the urgency of the organism’s need to seek relief from suicidogenic pain; bNon-suicidal self-injury (NSSI), classified as a ‘condition for further study’ in DSM-5 (APA, 2013), appears here as an exception, arguably lacking a ‘brain-type’ action: this function may be provided instead by other symptoms often comorbid with NSSI. Source: Reproduced from Soper (2018).

Figure 3.2  A tentative mapping of hypothesized types of antisuicide mechanisms (keepers) across common diagnostic categories of mental disorder

PAIN-TYPE (weaken the motivation for suicide) (i) Autonomic numbing. (ii) Medicate the pain. (iii) Pain offset relief. (iv) Distract from pain. (v) Detach from pain. (vi) Make sense of the pain. (vii) Find reason to live with pain. BRAIN-TYPE (restrict access to the means of suicide) (viii) Degrade ability to plan and enact tasks. (ix) Loss of psychomotor energy.

Suggested types of keeper anti-suicide mechanism



progressing to suicidal actions. One commonality, mentioned above, is marked suicidality – to be exact, suicidal ideas rather than the enacting of those ideas (Nock et al., 2013). Another is the characteristic stimulus-response course of CMD, precipitated by emotionally painful events, and typically lifting over time (with or without medical intervention) after the precipitating adversities are eased (Brown, 2009; Goldberg and Goodyer, 2005; Harris, 2000). Yet others include: extreme comorbidity – people diagnosed with one disorder usually also meet criteria for one or more others, concurrently or at different times (American Psychiatric Association, 2013; First and Pincus, 2009); lack of ‘zones of rarity’, or natural boundaries, between diagnostic criteria (Kendell and Jablensky, 2003); non-specificity of causation – to large extent, as the keeper model anticipates, any kind of adversity can precipitate any variety of CMD response (Goldberg and Goodyer, 2005; Kessler et al., 2010); non-specificity of treatments – therapies developed for one condition also alleviate others (Wampold and Imel, 2015); common cognitive deficits – selectively impairing, also as the keeper specification predicts, the ability to organize complex tasks (Harvey, 2004); coincident scheduling of first onsets – in adolescence, as already noted, the stage of life when suicidality first develops (Kessler et al., 2007); species-specificity – an absence of close animal models (Willner and Belzung, 2015); and so on. This mesh of continuities poses a problem for an ad hoc labelby-label style of analysis that is widespread in Darwinian psychiatry (e.g., Brune, 2016; Del Giudice, 2018) – some evolutionary hypotheses advanced for depression, others for generalized anxiety, yet others for schizophrenia etc. Soper (2018) argues that any explanation proffered for one diagnostic label is incomplete unless also explained is the detailed configuration that label shares, and its routine co-occurrence, with almost any other form of CMD. Soper’s model may offer parsimonious theoretical underpinning for what some researchers have inferred from empirical observation: that many psychiatric constructs, for all their superficial


differences, vary more in degree than kind and likely relate to a singular causal process, hitherto unclear (Caspi et  al., 2014; Menninger, 1963; Stochl et al., 2015). Fourth, it is possible to understand why psychiatric symptoms are poor predictors of suicide, and indeed why a decades-long search for any clinically useful marker has returned empty handed (Carter et  al., 2017; Franklin et al., 2017). The failure of prediction arises not particularly, as is often claimed, because suicide is rare; rare events are not necessarily unpredictable (Soper, 2019a). Rather, precisely this null result would be expected of an organism that is finely adapted to its ‘suicidal niche’ and already making best use of available cues (Soper, 2019b). Suicide attempts, as statistical residuals, are events associated with no utilizable prognostic information to which the individual’s defensive systems could have responded. It should be anticipated, then, that suicides offer little or no scope for being accurately foreseen at the individual level. Summing up, a posited convergence of evidence from multiple directions sets up a probability argument for special design (Williams, 1966, 1996). Soper (2018) finds no unaccountable inconsistencies, and no better explanation for the confluence. A software patch devised to stop humans switching themselves off in the face of difficulties would predictably include routines that look very much like symptoms of ‘functional’ common mental disorder. On this basis, he intuits, it is more likely than not that many outwardly dissimilar psychiatric states reflect the proper workings of systems that evolved to prevent self-killing.

Implications: The Case of Depression If the pain-and-brain framework is correct, its ramifications may be wide-ranging, profound, and take time to fathom. They could impact on the research agenda, suicide



prevention policy, psychiatric practice, and the conceptualization of psychopathology and mental health. We will illustrate with an example relating to the extensive and widely recommended use of antidepressants and other psychopharmacological treatments to prevent suicides among clinical patients assessed to be at risk (Wasserman et al., 2012; Zalsman et al., 2017). The task analysis outlined above suggests that certain common psychiatric symptoms – including the emotional numbing, cognitive impairment, fatigue, and generalized anxiety characteristic of adult-pattern depressive states – can be understood not as suicidogenic disorder, but expressions of the organism’s protective response to the lethal threat latent in chronic, intense, emotional pain. In other words, various common depressive symptoms may be conceived as actions of a psychological defensive system, in the same way that modern medicine understands coughing, vomiting, and fever to be defensive responses (Nesse and Williams, 1995). It is for this reason that the analysis predicts that, once the triggering distress is relieved, depressive symptoms would be expected to lift of their own accord, with or without medical intervention – spontaneous remission that characterizes the normal course of most common psychopathologies (Goldberg and Goodyer, 2005; Harris, 2000). The notion of protective antisuicide depression is not new. Hendin (1975) inferred such a dynamic from clinical observation half a century ago; and some epidemiological findings might, arguably, support Hendin’s case (Rogers et  al., 2018). Psychiatrists across decades have warned that suicide risk can intensify, not reduce, when depressive symptoms start to lift (Kahne, 1966; Meehl, 1973). What is new is an evolutionary foundation for the idea. Hence, evolutionary analysis pertains to important questions about the treatment of depression, in particular the use of pharmacological treatments, especially in the context of suicide prevention. We will highlight three issues. First, the model suggests that antidepressants treat symptoms rather than causes.

Addressing the root cause of depressive symptoms would presumably involve helping sufferers to relieve the precipitating distress, which probably originates, recalling Gunn’s (2017) Social Pain Model, from some form of social detachment. That said, any pain relief could offer provisional respite; and given the likely social nature of the triggering pain, any credible treatment, psychotropic medication included, could be expected to produce a strong placebo effect, signaling that a supportive attachment has been put in place (Davies, 2013; Wampold, 2018). Second, at worst, suppressing the psyche’s antisuicide systems exogenously, at least without other measures, would be expected to exacerbate, not lessen, suicide risk, at least in some circumstances. This expectation is supported by considerable pharmacological evidence (Hengartner and Plöderl, 2019; Sharma et al., 2016). Third, evolutionary analysis challenges a premise of such treatments, that people ‘at risk’ can accurately be picked out in clinical settings. As we have noted, special-purpose biological defenses would be expected to have exploited and exhausted any and all utilizable markers, with the result that suicides are probably not amenable to prediction in principle (Soper, 2019a). The evolutionary argument thus touches on an ethical question: whether it is justifiable to prescribe mind-altering drugs to large numbers of people, nearly all of whom were never going to take their own lives, in an effort to protect a small and unidentifiable minority. The analysis would, in the round, appear to lend theoretical support to those who already question on empirical grounds whether psychopharmacology is an appropriate approach to suicide prevention (Hjelmeland et al., 2019; Maris, 2015). Looking at alternative strategies, the same evolutionary analysis predicts that restricting access to lethal means (such as, for example, installing nets under favored jump sites, and limiting the size of retail drug packs) may be effective to an extent that


would seem far-fetched to people viewing such incomplete obstacles with the benefit of normal intellectual functioning (Chen et  al., 2016; Hawton, 2007). Interventions that only mildly complicate a suicide endeavor would be expected to disrupt disproportionately the plans of someone affected by denials of psychomotor energy, memory, decision-making, and other task-related cognitive faculties – attenuations which, Soper (2016, 2018) posits, may be protective aspects of depression. A slight delay may be enough to allow homeostatic affective systems to de-escalate from a suicidal crisis, restoring the organism towards a protective, above-neutral, resting point. Means restriction, in other words, could be understood to capitalize on and co-operate with the organism’s own antisuicide defenses.

Problems with Soper’s Theory On one hand, Soper’s (2018) model has merit. It appears, at least at this early stage, parsimoniously to fit multiple lines of evidence, and it does so arguably better than other available explanations; it could be judged attractive on the criterion of inference to the best explanation (Harman, 1965). From an evolutionary perspective, it appears to match biological function to observable form (Buss, 1995; Williams, 1996). The theory is in principle falsifiable: many findings would suffice as disproof – if science discovered, for example, nonhuman suicide, or a human population with a pattern of early childhood suicides, or a group that lacked positive correlations between suicidality and hypothesized keeper responses, and so forth. It could generate novel and testable ancillary predictions. We propose, for example, that Soper’s notion of a statistical, but only indirect, association between the scheduling of first onsets of keepers (triggered by a hormonal cue linked to puberty) and first onsets of suicide (dependent on intellectual competence) could be tested by comparing the epidemiology of suicide and keepers in populations with


delayed/accelerated intellectual development against populations with delayed/accelerated endocrine development. A pattern in which suicide, but not psychiatric symptoms, occurred among the hormonally delayed but cognitively precocious, and vice versa, could be taken to support Soper’s proposals and be difficult otherwise to explain. On the other hand, Soper’s theory faces at least four significant problems. First, being at the stage of a preliminary sketch, it lacks detail and raises many unanswered questions. It is not specified, for example, how exactly hypothesized antisuicide protections would operate. To illustrate, ‘loss of psychomotor energy’ (LoPE) (Soper, 2018: 143) is conceived as an autonomic defense against suicide, but self-killing could be brought about by inaction as well as action. It is unclear how LoPE would interact with other hypothesized keepers; it could conflict, for example, with others that presumably require positive action, such as the compulsive consumption of analgesics. The biological parameters of LoPE are undefined – whether it exists as a discrete condition, and how it would be operationalized as a testable construct, and so on. Soper’s proposals may have intuitive appeal, but there is much work to do before a robust, comprehensive framework could be said to have been achieved, despite, or perhaps because of, the breadth of the framework’s ambit. Second, the forward/reverse engineering approach, the appeal to evidence of special design on which Soper’s adaptationist arguments largely rely, is intrinsically intuitive notwithstanding apparent objectivity (Lauder, 1996; Williams, 1996). Due to the method’s subjectivity, another researcher replicating Soper’s thought experiments might not arrive at the same conclusions. This is not to say that his arguments are invalid, but that there is scope for different students legitimately to reach different opinions from the same data depending on their biographical backgrounds (Kuhn, 1977). Soper’s efforts to infer a priori design parameters for keepers, for example,



will not be entirely a priori: the author, a psychotherapist, could not have approached the topic with a blank slate and it would be surprising if his findings were not colored by experience. Indeed, some of his predictions might strike many workers in mental health as already matters of common knowledge. Third, Soper’s (2018) approach leans on a presumption of optimal outcomes: that because x would be biologically ideal, x is what we should find. While the optimization approach is a useful way to model biological problems and may suggest solutions, it is not a safe basis in itself for predicting evolutionary results. Many alternative outcomes of selection are possible (Gould and Lewontin, 1979), and the fitness functions of most adaptive problems are complex landscapes of hills and valleys, the path to optimization often blocked at local fitness maxima (Parker and Smith, 1990). Fourth, testing certain aspects of Soper’s (2018) theory may be problematic due to the composite nature of its hypotheses. Taking again the example of ‘loss of psychomotor energy’ (LoPE), this is presented as both an adaptive solution to suicide risk, and as an expression of that solution. Associations between LoPE and measures of suicidality that offer to support one hypothesis could simultaneously undermine the other: if, say, suicides happen alongside LoPE, then that could be read both as confirmatory evidence (because LoPE had mobilized as predicted to meet the threat), and as falsifying evidence (because LoPE had failed in its supposed design task, to stop suicides). This kind of epistemological trap is not unique to Soper’s theorizing and may be endemic in evolutionary science. A comparable zero-sum game plays out, for example, in the long-debated Westermarck effect, an evolved mechanism said to deter close inbreeding: the same evidence can be taken both to support and contradict the theory (Sesardic, 2005). On balance, while acknowledging these and other weaknesses, it is not easy to dismiss the thrust of Soper’s (2018) arguments. Intuitively difficult is the claim that varied symptoms of psychiatric disorders function

as special-purpose antisuicide devices. But to reject this hypothesis may be to invite fresh difficulty, because two questions would then call for answers. Which aspects of the antisuicide task analysis are being disputed? And, if not ‘functional’ psychiatric disorder, then what alternative empirical phenomenon is proposed that better matches that design specification? If the pain-and-brain model is broadly correct, the call would remain to explain why few people kill themselves. It may be partly for this reason that at least one prominent suicidologist is on record as finding Soper’s proposals persuasive (Lester, 2019). Time will tell if others agree.

CONCLUSION At one level this chapter carries an encouraging message. The evolutionary approach would seem, in principle, capable of bringing unity and coherence to suicidology’s current morass of theory. A ‘pain-and-brain’ framework in particular seems to offer a rallying point for numerous, superficially disparate, theoretical positions, such as IPTS (Van Orden et  al., 2010), IMV (O’Connor et  al., 2016), or SPM (Gunn, 2017), theories which essentially characterize suicide as a way to escape intolerable emotional stress. None would appear incompatible with the view that pain, as a biological imperative, motivates action to end or escape it, while regular adult human cognition offers intentional self-killing as an effective, but genetically destructive, means to answer that demand. But the corollary, that suicide poses an engineering problem, as summed by the tweet that began this chapter, may be harder to digest. Presumably human beings are prevented most of the time from switching themselves off because of one or more special-purpose software patches. Blind to our own instincts (Cosmides and Tooby, 1994), we may be oblivious to their functioning, and skeptical they may even exist. A research program to uncover their workings may not be


easy to formulate. The idea that humans are equipped with organismic defenses against suicide is not new (e.g., Himmelhoch, 1988; Hundert, 1992; Miller, 2008), but it has only recently gained prominence in the research agenda (Culotta, 2019). Its implications may run wide and deep, and call some longheld preconceptions into question: as Lester (2019) finds, accepting the ramifications may require close reading of the arguments. Progress is not helped by what Soper (2018) believes to be a systematic non-interaction between suicidology and evolutionary psychology, a two-way blockage of ideas that may go beyond the institutional disconnects seen elsewhere in psychological sciences (Staats, 2004). Soper posits that suicide and evolution, each for different reasons, are domains that many people find awkward to think about, researchers included. It may be for this reason that, in one direction, evolutionary psychology has largely ignored suicide, as indeed has psychology generally (Rogers, 2001): in view of the gravity and ubiquity of suicide as a human phenomenon, and the evolutionary puzzle it presents, remarkably little has been written on the subject from an evolutionary perspective, at least until recent years. In the other direction, suicidology has largely ignored evolutionary psychology. It may be illustrative that a rare review of the field, titled ‘Evolutionary processes in suicide’ (Chiurliza et al., 2017), attempts to appraise its research group’s ideas (and, oddly, only that group’s) without reference to evolutionary psychology’s primary texts or tenets – a surprising omission given that evolutionary psychology, ‘the study of behavior from an evolutionary perspective’ (Cornwell et  al., 2005: 369), is centrally relevant. This chapter calls for consilience between the two fields. An evolutionary stance would not in itself be a departure for suicidology: it would, rather, follow the lead set by Freud (1920/1991), Shneidman (1985), Joiner (2005), and other prominent researchers, drawing on evolutionary ideas across more than a century. Evolutionary psychology could synthesize, not replace, much of suicidology’s


existing theoretical and empirical content. There may be little to lose in such an incremental move. The upsides, on the other hand, may be great. Evolutionary psychology offers fresh perspectives for suicidology, and ready tools that, if used, could be decisive in a battle to save lives. Evolutionary psychology and suicidology deserve each other’s attention.

Notes 1  Reviews of prominent offers can be found in the general suicidology literature (e.g., Gunn, 2019; Gunn and Lester, 2014; O’Connor and Portzky, 2018; Paniagua et al., 2010; Selby et al., 2014). 2  If it were claimed that nonhuman suicide is rare thanks to the action of antisuicide adaptations – something like the ‘patch 7.822’ software update imagined in this chapter’s opening quotation – then those countermeasures need to be identified, as indeed we will later suggest they probably need to be identified in humans. 3  As a side point: some theorists argue that risk of suicide may vary, albeit weakly, with a heritable propensity for certain personality traits, notably impulsivity (McGirr et al., 2008). 4  Suicide would presumably have been no easier in our evolutionary environment. As grounddwellers on open grasslands, it may have been a scarcity of ready opportunities for self-killing that allowed humans to encephalize closer to the cognitive floor for suicide than would be feasible for other social animals. Other social animals that otherwise would be expected to benefit from increased social intelligence (Varki and Brower, 2013) may occupy habitats where suicide could be summarily enacted at almost any time by default – by not gripping (chimp), or not surfacing (dolphin), for example (Soper, 2019b). 5  As a related point, Humphrey (2018) speculates that suicidality may help to account for catastrophic demographic collapses thought to have occurred in early human pre-history.

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4 Evolutionary Psychology and Mindfulness and Meditation: Easing the Anxiety of Being Human James Carmody

INTRODUCTION Something called mindfulness seems to be popping up everywhere: in clinics and hospitals, schools, corporate offices, prisons, online, the list keeps expanding. Today, at the local farmer’s market, I bought greens from ‘Mindful Veggies’. Promoted as a wellbeing enhancer, studies show that mindfulness does indeed reduce stress and distress in a range of conditions and circumstances (Goyal et  al., 2014; Willem et al., 2016). In this chapter I describe the evolutionary roots of the psychological processes that give rise to the human angst that mindfulness addresses and how the training exercises designed to cultivate it alleviate that distress. And to provide context for those I first describe the cultural roots of mindfulness and meditation. Several innovative approaches to inquiry emerged during what has been called the Axial Age. In contrast to the Platonic and Aristotelian systems developing in Greece during that era, internal psychological models

developed in India including those of Vedanta and Buddhism. Training exercises designed to develop the personal qualities required to actualize the models’ goals were also developed and in keeping with approaches to knowledge at the time, these were not clearly distinguished from religion. Mindfulness, as it is now commonly recognized in the West, came primarily out of Buddhism and is described in the following section. Buddhist principles, particularly, later spread into other parts of Asia and integrated into those countries’ prevailing spiritual belief systems. Both parties were changed as a result of those meetings. After a hiatus of several centuries, increased global mobility brought Buddhism to Western countries and once again it has been adapted into the prevailing cultural narrative. One of those adaptations has been the integration of mindfulness, a core tenet of the system described in the following section, into the cultural narrative of self-help. The cultural origins and purpose of Buddhism however have parallels in some Vedanta


practices that also have migrated to the West in the ­ various forms of yoga. This secular transition has made its benefits more widely available than they might otherwise have been, for although a practice from a religious system is attractive to some people, it is alienating to many in the secular West. This transition has also brought mindfulness under the gaze of empirical science and close inspection of its mechanisms of action reveals parallels and differences in some principles independently developed in Western psychology to categorize, account for, and alleviate human angst. Those principles, together with evolutionary theory, can provide a coherent and culturally familiar explanation of the everyday mental unease that plagues us and how the practice of mindfulness alleviates it. This evolutionary and needs-based lens describes inbuilt patterns of attending that keep us illat-ease, and the psychological principles that mindfulness and several similar mind–body practices draw upon in enabling the recognition and amelioration of that distress. The description draws upon my own and others’ published studies of the clinical effects and mechanisms of mindfulness training (MT), as well as experience and feedback from teaching mindfulness to patients and clinicians. The description is phenomenological because suffering and mindfulness are rooted in felt experience and it is their felt sense that people wish to address in doing the practices. Clinicians also talk most meaningfully to patients in those terms. In that sense, mindfulness practices can be thought of as phenomenologically empirical explorations of the mental processes giving rise to mental distress and the capacity for self-­ regulation that emerges in the face of it. The chapter also draws upon my own experience with 50 years of practice in Buddhist and Vedantic traditions of inquiry in Asia and Western countries. Many academic papers about mindfulness are caught in attempting objectivity in relation to something that is often anything but. In the background, u­ sually undescribed, stands the author’s positive personal experience with mindfulness that led


them to the research and that has guided their decisions about the conditions, instruction, and syllabus of the mindfulness intervention. For mindfulness makes apparent the normally unrecognized patterns of attending that nevertheless continuously affect our felt sense and the background hope is that study participants also will benefit from that kind of noticing.

THE CULTURAL ROOTS OF MINDFULNESS AND ITS MIGRATION INTO WESTERN SETTINGS The Buddhist and Vedanta narratives are rooted in the primarily introspective approaches to knowledge extant in India around 500 BCE, the time of the historical Buddha. They each place the source of human angst in ignorance of the moment-by-moment construction of the personal self, and the chronic dissatisfaction (suffering) arising from the accompanying sense of ownership of its desires and aversions. In this respect they are not a description of how the physical world operates, but of what we call mind. As the Buddha described his insight into this dilemma to others and the experience of enlightened release accompanying it, an eightfaceted system developed through which they also could cultivate a similar recognition. One facet was the cultivation of something called ‘sati’ to serve as a heuristic aid for real-time recognition of these mental operations and their effects. Sati is from the Pali language spoken in Northern India at the time, but that is no longer understood outside the Indian scholarship community. Exactly how sati was translated, described, and cultivated varied in the places to which Buddhism migrated over the centuries. This is apparent in the varied teachings and practices of the Western Buddhist sects whose traditions derive from those countries. Mindfulness, a term with an already existing meaning in English, emerged as the accepted translation during the 19th century as Buddhism was becoming of interest in the West.



Recognizing the commonality that Buddhism’s goal of reducing mental suffering had with the goal of patient care, Kabat-Zinn (Kabat-Zinn, 1982) experimented with teaching groups of patients a selection of training exercises used to cultivate sati in South Asian traditions. Those patients described obtaining benefits in coping with their illnesses from participating in the classes that came to be called the Mindfulness-Based Stress Reduction (MBSR) program. Replications in peer-reviewed journals affirmed those benefits and the program became widely used in clinics (Shonin et al., 2015). Principles and practices from MBSR form the foundation for many of the adaptations and applications found in the wide variety of settings in which mindfulness now appears. While the processes at the root of the mental distress that the cultivation of mindfulness addresses are interwoven and run in parallel, for explanatory purposes I describe them as a sequence. It is important also to note that early Buddhism employed a somewhat different frame to categorize the qualities of experience than Western systems do. For example, it did not use the construct of emotion in the description of affective experience; rather it used a more granular analysis of experiential components that comprise those states as described in following sections. Attention regulation, however, is common across the systems and is known to be fundamental to wellbeing (Posner and Rothbart, 2007). For that reason, it may be best to begin with attention and the priorities that effect it.

THE EVOLUTIONARY ROOTS OF ATTENTION AND ITS ROLE IN A NEEDS-BASED SYSTEM MT usually begins with an attention-regulation task. A common one asks the person to place their focus on the sensations of their breathing and to keep it there for some time. While this may seem a relatively easy task, trainees report it as one of the most challenging (Segal et al.,

2013). They stay with it for a breath or two before attention wanders to daydreaming. The tenacity of this default movement to cognitions in the absence of sustained watchfulness suggests an important function, one that becomes clear in reflecting on the role attention plays in our mental ecology. Our brains are continuously processing all manner of information about the internal and external environment. Attention, the capacity to selectively attend to some portion of this information over others, particularly opportunities and threats to the fulfillment of needs, has clear value for survival and reproductive success (Geary, 2005). Selection has also resulted in this process being i­mmediate rather than through conscious, deliberate, and slower decision-making pathways (Tomlin et al., 2015). When physical danger threatens, as it regularly did in the evolutionary past, attention automatically orients to sensory processes monitoring the external environment. Attention is also intimately connected to arousal. In the best-selling book Why Zebras Don’t Get Ulcers, Sapolsky (2004) describes how the attention of animals in the wild is oriented to the senses and to arousal: danger is smelled, seen, or heard, arousal levels and tension spike, the animal responds in some way, and a more quiescent state resumes. We also would live in a more relaxed here and now if real and immediate physical dangers were the principle risks that our attention responded to. But being in the moment is not characteristic of modern life. The capacity for cognition and language makes possible the imagination of conceivable future threats (Andrews-Hanna, 2012; Baumeister et  al., 2001) as well as complex planning and discussion of how best to address them. The importance of those capacities to modern humans is evident in our attention’s insistent default to the concerns of projected futures and pasts when it is not required for the execution of an immediate task. This can be observed by deliberately taking notice of the content of the imaginings to which our minds ‘wander’. There we see recurring and often conflicting and entangled concerns about


our own and our family’s and friends’ welfare, social standing, sex, work, and money. The persistence of this default, and its affective upshot, was captured nicely in a real-time study by Killingsworth and Gilbert (2010). Prompted at random times to report what their attention was on in that moment, subjects reported it being on the task at hand for only about half the day, even though they reported greater happiness at those times. Significantly, the attention wandering generally preceded the happiness decrease. It is this propensity of attention to quickly and repeatedly default to cognitions, memories, plans, speculations, and daydreams, that mindfulness trainees encounter when asked to focus on sense-based experience, and that they find so challenging to overrule and regulate. They discover also that much of this cognition goes on outside of awareness and becomes apparent only when they deliberately watch their mental activity. In the absence of immediate danger, then, attention functionally defaults to cognitive processes serving the social-safety needs of tribal primates, particularly those for relationship/belonging, status, and power. The biological importance of these needs is evident in the fact that health becomes compromised when, for some reason, we are stripped of them. Also, their intricately interwoven and at times conflicting nature, together with the fact that they have no organic satiation mechanism,


means that navigating threats and opportunities and monitoring projected pasts and futures is a constant project.

DARWIN AND BUDDHISM’S FIRST NOBLE TRUTH: VIGILANCE AND THE INTERNAL NARRATIVE MAKE UNEASE OUR EVERYDAY STATE In traditional Buddhist teachings, the reduced happiness Killingsworth and Gilbert (2010) found associated with the preoccupations of a wandering mind results not from the thoughts and imaginings themselves, but from the unpleasant sensations of constriction that reflexively accompany their semi-vigilant (‘what could go wrong here?’) and uncertaintyrelated character. A discomforting cycle is then set up as those unpleasant sensations of tension remind us again of the threat-related thought (Damasio, 2003). Extended preoccupation with these alarm-based cycles is experienced as rumination and worry. These are accompanied by arousal-related inflammatory processes. As we’ve all experienced, the level of arousal, constriction, and unpleasantness can range from very mild to dreadful depending on the degree to which those needs are frustrated or threatened (Brosschot et al., 2006). Figure 4.1 illustrates this vigilance-based cycle in the experience of anxiety.

Figure 4.1  Alarm-related components of experience forming a cycle of distress



When mental bandwidth is occupied by this narrative, curiosity and connection with our surroundings becomes problem-focused, and we are less than openly present for the present needs and concerns of others. When attention is task-related, however, this internal narrative recedes (Watkins, 2004) and we are less affected by its threat- and opportunityoriented memories and imaginings. Even when these preoccupations barely reach awareness (Brosschot et  al., 2014; Creswell et al., 2013; Custers and Aarts, 2010; Dahl et al., 2015), the ongoing bodily discomfort gives rise to a desire for a break in something more pleasant; to interrupt the cycle and replace it temporarily with one characterized by greater ease. And because the experience of pleasure and delight encompasses the body (Biswas-Diener et al., 2015), a sense pleasure is usually the most immediately accessible. It might be something like a snack, a drink, or a drug. It may also be something more elaborate; the possibilities are as broad as imagination and resources allow. We don’t start life cognitively preoccupied in this way. We arrive as little sensate creatures, curious and awake to the wonder of touching, tasting, hearing, seeing, moving, and their pleasant and unpleasant feeling tones. A cognitive past and future become gradually and imperceptibly woven into this sensory experience alongside language, the naming and appraisal enabling us to describe our needs and impressions to others (Alderson-Day and Fernyhough, 2015). As we learn to weave our way through the fragile social maze, the hopes, comparisons, judgments, and regrets embedded in this emerging internal narrative come to mediate and filter sensory perception and experience, and weave indiscernibly into a developing sense of self.

Using Our Heads to Get out of Them Just as this safety-oriented cognitive watchfulness has an affective downside, cognition

can also wish for and imagine a life free of it and trial possible solutions. That’s a reflection for the ages. It is also one that preoccupied the historical Buddha who, after intense experimentation, recognized the above patterns shaping the affective quality of his own life as well as related insights into how these can be overcome. In conveying these to interested friends he saw that they were also useful to others. Three of those insights are contained, to a greater and lesser degree, within present-day MT programs. They are designed to support greater awareness, acceptance, and some level of everyday self-regulation in the face of these mental and perceptual tendencies shaping everyday feeling life (Cavanagh et  al., 2014; Donald et  al., 2016; Saunders et  al., 2016) and can be operationalized in familiar psychological terms. The analysis is not regarded as the final word on mental mechanisms but as a description of mental qualities that can be phenomenologically recognized in real time, and trainees comprehend and use them to suit their interests and circumstances (Carmody and Baer, 2008; Cebolla et al., 2017). The first insight, alluded to in the previous section, is that everyday experience and emotions are constructed from a suite of just three interwoven phenomenological components: cognitions, sensations, and their pleasant/unpleasant feeling tones. Classification and description of the affective dimension of experience change with the age and the culture, and feeling here is not to be confused with how we commonly use the term today when we might say we are feeling angry or sad. It’s simply the pleasant or unpleasant quality of a sensation. Also, emotional categories vary across cultures and over time; something described as an emotion at one time might be referred to as a passion in another. In the Buddhist analysis emotions are approached more granularly as amalgams of those three fundamental qualities. When those components are not distinguished their felt experience is seamless, as illustrated in Figure 4.2.



Figure 4.2  Memory, imagination and emotion are symphonies of three interwoven experiential components

Experiential recognition and discrimination of the components starts, most usually, with re-awakening interest in the realm of sensation. In the body scan, for example, an exercise taught in MBSR (Kabat-Zinn, 1990), trainees are asked to systematically direct attention to each part of the body and to notice any sensations that may be present there, including subtle and neglected sensations that may escape awareness in everyday life; this while refraining from attempting to change the experience in any way. They are instructed to notice also any pleasant or unpleasant feeling tone that may be associated with a sensation, and the difference between the sensation and any thoughts that may also be present. This is schematically illustrated in Figure 4.3 using the example of a fearful thought and the sensations of constriction that may be associated with it, and which, on a less granular level, we experience as anxiety. This learning is akin to winding back the developmental and experiential clock. As described in the previous section, we are not born with these groupings. Cognitions that had been so implicitly integrated (Blair, 2002) into our early world of sensation and

affect that their distinction was not apparent in awareness (Pessoa, 2008) become noticed and named. Their associations, so rapid they are normally missed, become apparent in noticing that attention does not stay with a sensation, but quickly goes to its feeling tone, to thoughts about it, or to something else. Implicit in this bare noticing of experience is an embodied acceptance, one that also may be made explicit in the instructions. Interoceptive awareness is important in emotion regulation (Füstös et  al., 2013) and the perception of internal experience developed by these MT exercises appears to mediate its beneficial effect on emotional wellbeing (Mehling et al., 2012). And even though trainees initially report finding these exercises challenging (Segal et  al., 2013), they result in measurable increases in volitional orienting of attention (Chan and Woollacott, 2007; Jha et  al., 2007), improved performance on sustained attention tasks (Tang et al., 2015), and improvements in working memory and autobiographical memory (Lao et al., 2016). Also, the differential thickness in brain regions associated with attention, interoception, and sensory



Figure 4.3  Components recognized as differentiated and connected

processing found in meditators compared to matched controls (Lazar et al., 2005) is consistent with meditators’ increased capacity for awareness of internal states, particularly awareness of breathing sensations. The second insight is that attention can be regulated to create a more benign or neutral affect. It builds upon the first insight and can be experienced in any of the MT exercises; when attention is directed to arousal-neutral bodily sensations, such as those of breathing for example, a more benign affect emerges. The sensations of breathing provide an accessible and readily available object of attention that can be unobtrusively turned to as a restful experience in moments of stress. This facility, sometimes referred to by clinicians as ‘going to the breath’, is readily established. In the initial trials of MBSR, a large majority of participants indicated that they attached high importance to this simple skill to calm themselves in moments of stress/distress (Kabat-Zinn, 1987). This redirection of attention and its affective result is illustrated in Figure 4.4. It is distinguished from experiential avoidance, which involves a compulsive mental (or physical) turning away from difficult experiences (Hayes et al., 1996).

The principle is consistent with William James’ cogent remark that experience is what one pays attention to (James, 1890). The key role that this effortful focusing of attention plays in wellbeing-supportive emotion regulation and in self-regulated behavior (Baumeister and Heatherton, 1996; Kirschenbaum, 1987; Thayer et  al., 1996) was confirmed in later experimental studies, and in the findings that poor cognitive control is associated with many mental disorders (Snyder and Hankin, 2016). Rumination, for example, is an indicator of attention wandering from immediate tasks and becoming captivated by an uncomfortable internal narrative. Supporting this principle, MT has been shown to reduce rumination (Campbell et al., 2012) and to increase mood as a result (Huffziger et al., 2013). More specifically, an MT exercise focusing on the awareness of breathing improved mood, meta-awareness, and mind wandering (Levinson et al., 2014). These observations are supported by imaging studies in which mindfulness trainees show less activation of brain regions involved in narrative processing of self-relevant stimuli and greater activation of regions implicated in ‘experiential’ processing, relative to novices (Farb et  al., 2007; Lutz et  al., 2016).



Figure 4.4  Attention shifts from differentiated components to arousal-neutral sensations of breathing

Interestingly, MT appears to reduce reactivity to emotional stimuli, which is not found with relaxation training (Ortner et al., 2007). The third insight is the use of an observing perspective toward mental life. This ‘observing self’ (Deikman, 1982) is used to notice thoughts/images, sensations, and feelings while remaining unaffected by their content and tone. It is itself a cognitive process, albeit one used to cultivate a sense of detachment from mental phenomena that previously had captured attention and created distress.

This observing stance is implicit in most MT exercises and is cultivated explicitly by the practice of silently naming component mental qualities as they are occurring in awareness. For example, rather than contending with, or trying to push away, a harshly self-critical thought, attention is reoriented from its content, such as ‘I am a failure’, to the more affectneutral reflection ‘This is a thought’. The strategy is illustrated in Figure 4.5 using the example of a commonly reported thought during panic attacks.

Figure 4.5  Re-perceiving reduces distress through a perceptual/attentional shift from what the thought is about – ‘I’m going to pass out’ – to the thought as an event in the mind/ awareness – ‘This is a thought’



Referred to as decentering (Teasdale et al., 2002) and meta-cognition (Wells, 1999), this meta-awareness increases with participation in MT (Carmody et al., 2009; Feldman et al., 2010; Lao et al., 2016; Levinson et al., 2014; Teasdale et  al., 2002). It has been found important in the treatment of depression (Bieling et al., 2012), and this decreased cognitive reactivity appears to mediate the association between mindfulness-based cognitive therapy and decreases in depressive symptoms (Cladder-Micus et al., 2017).

MINDFULNESS AND THE COGNITIVE NARRATIVE’S DOUBLE-EDGED SWORD We are tribal primates with a powerful capacity to imagine. This wondrous ability envisions possible futures and constructs narratives of the past beyond simple conditioning. It gives us a powerful advantage in meeting our human needs and is that which most clearly separates us from other primates. The capacity for language that developed in conjunction with it allows also for conversations about where dangers are most likely to be found, how they might best be met, and the passing of those lessons across generations – group learning, in other words. The clear survival upside of imagination is seen in the development of tools and their uses, and in the ability to plan and coordinate future activities and scenarios that would favor resource procurement and advantageous mates: to be able to plan for the hunt and what would be required, as well as how any gains might be distributed. When bands were small and less complex, dangers imminent and immediate, and neural cognitive capacity less developed, those imaginings were probably relatively short-lived; life required careful and continued attention to the senses. Immediate physical dangers have been minimized in modern life and sensory monitoring has become less necessary. In these

circumstances, attention defaults to supporting our social needs and planning how they can be met. And as social life becomes more complex, the goals longer term, and success and failure more contingent, imagining assumes an increasingly central role. Essential to this planning is imagining what could go wrong here, how plans might be threatened by others or by circumstances, and the consequences of these in terms of our own, and our kin’s, future suffering and possible death. Imagination also allows for reflections that give rise to questions of meaning and existential angst. Each age and culture developed ways and means of coping with this anxiety that arises from the necessary uncertainty of our plans, and of life itself. Some rely on placating and beseeching imagined beings assumed to control events. The Greeks began a more rational and empirical approach to understanding human nature and events that unfold in the world, apparent in the teachings of people such as Plato, Aristotle, and Archimedes. Around the same time philosophers in India developed what we would now call psychological methods of inquiry that focused on the mind itself. In that sense they are not descriptions of the world, but mental models that allow insight into the machinations of the vehicle through which we apprehend the world and how it can be self-modified to alleviate the angst. In its original context, mindfulness was cultivated as part of a training system to recognize how mental suffering is created moment-to-moment in the human mind and the behaviors and attitudes that can alleviate it. And while some schools of Western psychology developed constructs and principles that parallel some of those found in Buddhism, they did not develop training exercises that so systematically develop their recognition and self-regulation. In that sense, one of Buddhism’s most important contributions has been the practices to actualize those principles; ones that have been seamlessly integrated as mindfulness into existing psychotherapies.


In our complex and secular societies, the cognitive activity required to navigate for success in status, power, and relationships consumes inordinate amounts of neural bandwidth. And the affect associated with this is evident in ever-increasing rates of anxiety, depressive disorders, and suicide. It may also be contributing to increasing rates of addiction and obesity; rates that may make a more universal healthcare unsustainable. The MT exercises support recognition of this mental activity that goes largely unnoticed in daily life, even as it is affecting wellbeing. To those ends, mindfulness encourages the recognition that our apparently seamless mental activity comprises phenomenological components: sensations, cognitions, and their pleasant/unpleasant affective quality that we don’t normally experience as separate. The exercises also develop a capacity to notice where attention is focused in that suite and to regulate attention so that it becomes less conditioned and more fluid. The exercises also expose attention’s default impulse toward cognition and the narratives forming through imagination and memory, its handmaiden. As a needs-serving mechanism, cognition has a watchful quality for threats and opportunities. In the mental background, the default mode network and related functions are planning and wondering what could go wrong here and whether this is an opportunity. MT makes this vigilant quality apparent, as well as its affective downside in the uncomfortable sensations of constriction that naturally accompany it. It also reveals how the system relaxes as interest and attention are re-oriented to just sensation: an ease that is associated with reduced neural monitoring activity and downstream changes in arousalrelated biomarkers. And while MT offers the opportunity for profound insight, people come to it with varying levels of interest and curiosity so that each gets off at their own stop along the route. In the clinical and secular settings into which mindfulness has been introduced it is valued primarily for the palliative effects


that the practice provides: I want to feel less ­anxious or less depressed, I want to sleep better, or I’d like moments of quiet in the tumult of modern life. The relief that accompanies these recognitions satisfies the interest of most people. For those sufficiently interested to continue exploring the system’s original existential goal, other mental features become apparent. Gaps begin to appear between thoughts and in those moments the still background becomes apparent. The natural re-emergence of thoughts reveals how the narrative they form has become indistinguishable from that still presence within which they occur (Carmody, 2016). You realize that it has always been there, just overlain by attention’s ongoing fascination with the contents of the cognitive narrative. It also becomes apparent just how much of our lives are spent distracted and preoccupied by that imagining. Perspective shifts with that experience, as it would if a fish was to recognize water.

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5 Evolutionary Psychology and Environmental Sciences Ulysses Paulino Albuquerque, Joelson M. B. Moura, Risoneide Henriques da Silva, Washington S. F e r r e i r a J ú n i o r , a n d Ta l i n e C . S i l v a

INTRODUCTION An investigative program of evolutionary psychology must address the origin of human beings, as the environments that generated pressure during the evolution of early hominids form the basis for premises about the evolution of the human mind. As evidence suggests the African savanna as the most likely place for the origin of the modern human being, the savanna environment usually receives more emphasis than other environments. We have succeeded as a species through mental specializations, also understood as evolved psychological mechanisms. These specializations were selected because they solved problems in paleoenvironments, and were inherited by subsequent generations of hominids. For example, when exploring new landscapes, early hominids needed to quickly identify potentially dangerous situations, which trees were climbable, and where they could shelter. These decisions needed to be fast, and they were only possible because

previously selected mental mechanisms allowed the assessment of the landscape, even if unconsciously (see Zajonc, 1980; Townsend and Barton, 2018). If we assume that the savanna was the ‘main paleoenvironment’ of our evolution and that we inherited both physical and mental adaptations of our ancestors, the abovementioned argument is coherent. However, the literature indicates that we evolved along different lineages and from myriad hominid groups that coexisted in a wide range of environments, and that more than one point of origin of H. sapiens may have existed (Foley et  al., 2016; Stringer, 2016). Evolution may have occurred independently in different areas, with hominids developing morphological substructures that resulted in a complete set of H. sapiens characteristics. Stringer (2016) calls this independent evolution ‘African multiregionalism’, characterized by interfertile subdivisions of H. sapiens in their evolutionary history across Africa.



This discussion is central to a program that attempts to investigate the evolution of the human mind and human behavior. Discussing the origin of human beings is essential for evolutionary psychology and for understanding how our minds work in relation to the environment and all its components.

THE ORIGIN AND EVOLUTION OF HUMANS The transition from dense and closed forests to the savanna may have occurred slowly. This suggests that early hominids left the canopy of forest trees gradually, venturing into the East African savanna to explore available resources and to identify hazards and safe sleeping places. Thus, arboreal behaviors may have coexisted with bipedal locomotion (see Townsend and Barton, 2018). Lucy, the most famous Australopithecus afarensis, had both bipedal and arboreal habits (Larson, 2012). Until recently, paleontological data suggested that the first hominids appeared in Central Africa seven million years ago (Ma) (see Böhme et  al., 2017). However, recent evidence suggests that the earliest hominid, Graecopithecus freybergi, lived in a savanna environment in the region of Greece, between 7.37 and 7.11 Ma, which is 200,000 years earlier than the previous earliest known hominid, Sahelanthropus tchadensis, found in Africa (Böhme et  al., 2017). Likewise, Homo sapiens was believed to have originated around 200,000 years ago in South Africa, but recent fossil evidence suggests that H. sapiens appeared about 315,000 years ago in Morocco, 100,000 years earlier than previously thought (Hublin et al., 2017; Richter et al., 2017). These fossils have a mix of characteristics of H. sapiens fossils from other parts of Africa, indicating a multicentric genesis for our species (see Hublin et al., 2017; Richter et  al., 2017). This finding is consistent with genetic evidence that the first divergence of modern human populations

occurred between 350,000 and 260,000 years ago (Schlebusch et al., 2017). In addition, a hominid skull, dating back about 436,000– 390,000 years, was recently discovered in the Cave of Aroeira in Portugal, reinforcing the idea that human origins did not necessarily occur in Africa (López-García et  al., 2018). Although the savanna is still regarded as the main setting of our evolution, these findings suggest that the origin and the great divisions in the family of hominids may have occurred outside Africa. Nonetheless, if we understand that establishment in the savanna was important for the survival of hominids, it is reasonable to infer that, over time, natural selection favored individuals better adapted to savanna conditions. These individuals inherited the anatomical and cognitive apparatus evolved in this environment and were most likely to survive and leave offspring. This moment was crucial in evolutionary history. Many aspects of our anatomy and current behaviors resulted from solutions to challenges faced by early hominids (Townsend and Barton, 2018). Townsend and Barton (2018) argue that common behaviors and anatomical adaptations of early hominids in the Pleistocene persist today. For example, the palmar grasp reflex is a primitive reflex. It consists of a strong pressure with the hands and represents the primate’s need to hold the mother’s skin as she moves through the canopy of the trees. During childhood, for example, there is a tendency for children to show climbing behaviors (e.g., climbing trees or climbable objects) that fit the category of primitive reflex (Townsend and Barton, 2018). Brachiation is also still used today by children and gymnasts and was essential for the hominids in the savanna paleoenvironments. Perhaps children use tree climbing as strategy to avoid predators (Coss and Moore, 2002). Brachiation refers to a mobility method that depends on the specific structure of the shoulder to hang on the tree limb and allow the arm to swing in a complete circle (Townsend and Barton, 2018). These authors also suggest that the standard


size of the human hand is proportional to the size of tree branches capable of supporting a human’s weight during a climb. In addition, humans generally prefer horizontal-branched trees precisely because it facilitates climbing. These behaviors can be understood as an ancestral inheritance of early hominids, with our cognition, like our anatomy, resulting from adaptations to the selective pressures of paleoenvironments (Tooby and Cosmides, 2015). Blome et al. (2012) demonstrated that the African paleoclimate from 150,000 to 30,000 years ago also displayed regional variation, so that periods of high aridity or humidity did not occur simultaneously in the northern, eastern, tropical, and southern regions of Africa. According to these authors, this climate heterogeneity may have created opportunities for hominids to migrate to adjacent regions. Furthermore, Coulthard et al. (2013) found that, in humid climates around 100,000 years ago, major African river systems flowed northward, across the Sahara and to the Mediterranean Sea. These authors believe that three now-buried rivers could have been active in the period of human migration across the Sahara, with the abundance of water resources creating viable migratory routes for humans. Evidence shows that hominids adapted to various environments in a wide latitudinal range, such as the temperate and subtropical north of China and tropical regions of Southeast Asia (Roberts et  al., 2016; Kong et al., 2018). The use of fire, which is a practice frequently described in the literature on arid environments, has also been observed in tropical forests (Friesem et  al., 2017). In addition, traces of foraging activities and the discovery of tools for hunting arboreal animals challenge the dominant idea of the evolutionary adaptation of the first humans to the arid environment of the savanna (Barker et al., 2007; Friesem et al., 2017). If cognitive mechanisms result from responses to selective pressures of the environment, much of our mind may also be ‘trapped’ in evolutionary environments. If this is true, a challenge for evolutionary


psychologists would be to broaden the ­spectrum of the environments in which we evolved and the influence of the evolved psychological mechanisms in solving problems different from those found in the savanna. If the human mind has evolved in response to the difficulties imposed by the environment, and if H. sapiens has emerged and evolved in different environments, it is possible that today’s human behavioral responses, including their preferences, are a reflection of this multicentric origin. Indeed, the paleontological evidence that hominids inhabited and explored several environments in the Pleistocene suggests that other psychological mechanisms may have evolved in periods before or after establishment in the savanna. For example, a recent study by our research group has shown that some people, when analyzing landscapes of savanna, rainforest, tundra, desert, coniferous forest, deciduous forest, and urban landscape, prefer images of exuberant green rainforests (Moura et  al., 2018). In addition, people living in Spain tend to prefer densely green and closed landscapes (Hartmann and Apaolaza-Ibáñez, 2010). Because this landscape is typical of Spain, and in Brazil there is great media appeal to preserve the Amazon rainforest, these findings suggest that recent stimuli, rather than innate responses, may exert strong influence on human behavior. According to Barrett (2012), adaptations may provide plasticity to the human mind. They may also integrate mechanisms – whether more general or more specific – shaped by evolutionary history with those shaped by the ontogenetic development of the individual. Therefore, our mental mechanisms may be heterogeneous in origin, with new structures evolving from older structures and ancestral features combining with relatively recent characteristics (Barrett, 2012). Thus, cognitive adaptations are not necessarily the result of responses to difficulties imposed by a specific environment. They might reflect the selection of general strategies of the human mind to meet challenges in different environments.



THE ENVIRONMENT OF EVOLUTIONARY ADAPTEDNESS (EEA) AND THE STRUCTURING OF THE HUMAN MIND Understanding the evolutionary environment of hominids is crucial for evolutionary psychology and other disciplines interested in the evolution of the human mind. For example, Bowlby (1982) coined the term Environment of Evolutionary Adaptedness (EEA) to refer to the environment that selected the current genotypes of an organism. According to this perspective, it is reasonable to suppose that these environments also influenced the selection of mental traits of human beings. Frost (2011) proposed that, for humans, the EEA would be represented by the African savanna of the Pleistocene, the environment probably occupied by early H. sapiens before they started migrating to other continents about 50,000 years ago. Many authors argue that human psychological mechanisms evolved in response to the stable characteristics of the savanna environments (Tooby and Cosmides,

1992, 2005), and the reconstruction of these selective environments could indicate why humans have propensities for certain types of thoughts, motivations, and behaviors (Foley, 1996). However, the previously mentioned evidence of evolution of hominids in different areas of the African continent seems to challenge the savanna hypothesis (see Bolhuis et al., 2011). Thus, the human EEA may comprise a multitude of geographic and temporal environments (Volk and Atkinson, 2013), that is, the EEA has become less specific, taking into account not only the African savanna (see Tooby and Cosmides, 2015), but also the other selective environments in which humans have lived over the course of their evolution. As a consequence, humans may have developed psychological mechanisms in environments that were different from the African savanna (see Hartmann and Apaolaza-Ibáñez, 2010, 2013; Moura et al., 2018) (Figure 5.1). Studies on human preference for landscapes, for example, provide evidence that these psychological mechanisms may have suffered interference from the interaction

Figure 5.1  Environment of Evolutionary Adaptedness definition (EEA), original version and extended version Source: Created by the authors.


of humans and different ancestral environments. Orians (1980) argues that, because the savanna is an open environment, it enabled the first hominids a more accurate perception of approaching predators. This suggests the evolution of a psychological mechanism in humans to prefer savanna landscapes – the savanna hypothesis. However, several studies have reported preference in humans for environments other than African savannas (see Han, 2007; Hartmann and Apaolaza-Ibáñez, 2010, 2013; Moura et al., 2018). Some studies have tried to understand how our species recalls information that is relevant to survival, providing evidence of how the human mind may have evolved psychological mechanisms that deal with risky situations in different environments. Yang et  al. (2014) observed that people in both ancestral survival scenarios – grasslands and in non-ancestral or modern environments – recalled important words in a survival situation. In another study, Young et al. (2012) found that threats in modern environments – such as firearms and cars – capture and maintain attention in the same way as would be expected for threats in ancestral environments, such as snakes and spiders. These findings lead us to believe that natural selection favored psychological mechanisms that deal with challenges regardless of the type of environment. Thus, human inventions (e.g., firearms and cars) that are immersed in the culture and environment may be acting as a selective force that activates modern psychological mechanisms. This fact seems to indicate that the human construction of niche1 interferes in own and others’ psychological mechanisms. This interpretation finds support in reports that psychological mechanisms that favor the recall of information relevant to survival can be observed in people occupying different contemporary environmental and cultural contexts (see Barrett and Broesch, 2012; Barrett et al., 2016). For example, Barrett and Broesch (2012) found that children living in the city of Los Angeles in California and children of a village in Shuar in the Ecuadorian Amazon had high levels of recall when images of and


information on the name and diet of dangerous animals were presented.

Did Evolution Endow Us with a Naturalistic Mind? We believe that many of today’s human decisions and behaviors are influenced by the same psychological mechanisms present in our ancestors. An example of this would be the ability to recall information relevant to survival (see Nairne et  al., 2007), such as snakes and spiders (see Young et al., 2012). However, we also believe that some of these ancestral psychological mechanisms have adjusted to the adversities of new environments humans occupied throughout their evolution. Consequently, derived psychological mechanisms evolved from ancestral psychological mechanisms. The ability to recall information that refers to a risky situation in a modern environment, such as firearms and cars, is evidence of a psychological mechanism adjusted to the reality of contemporary environments (see Young et al., 2012). Barrett (2012) relativizes the influence of ancestral environments in the present – in the case of evolved psychological mechanisms shaped in these environments – considering innate cognitive modules as mechanisms specialized to solve a specific adaptive problem. However, if adaptations in the brain are analogous to adaptations of the body, such as tissue types, they are likely to be heterogeneous and hierarchical (Barrett, 2012). A hierarchical organization is a feature of systems that evolve and develop new structures from older structures. These adaptations are, therefore, a combination of ancestral and recent traits (Barrett, 2012). Thus, mental adaptations can be constructed during the ontogenetic development of each individual (see Barrett, 2012). As changes in the individual’s social environment occur, there may be a selection of ‘dormant’ behaviors or preferences that would never or rarely be generated by the brain if the environment remained static (see Barrett, 2012).



A study by Sandry et al. (2013) provided evidence of the hierarchical organization of the human mind: these authors demonstrated that people do not recall adaptive information in a similar way. By studying the memorization of words in different scenarios – survival, fear and phobia, partner selection, incest avoidance, detection of cheaters, jealousy, infidelity, and acquisition and maintenance of status – they found that the survival scenario excelled in the number of words remembered by people when compared to the other scenarios (which were also considered adaptive). If human memory were a non-hierarchical system, all these psychological mechanisms should have promoted recall equally.

This evidence suggests that psychological mechanisms evolved through processes of descent with modification, indicating the formation of human cognition by a combination of ancestral and derived psychological mechanisms (Barrett, 2012). This should make brain processes highly heterogeneous and possibly hierarchically organized, with information organized in human memory according to its relevance in dealing with imposed environmental adversity. Then, some ancestral or derived psychological mechanism, or both simultaneously, would be activated (Figure 5.2). Albuquerque and Ferreira Júnior (2017) argue that evolution has provided us with a naturalistic mind that evolved to account

Figure 5.2  Structure of the human naturalist mind: Scheme I shows a cladogram with the ancestral and derived psychological mechanisms that constitute the human mind. Scheme II illustrates the ancestral and derivative psychological mechanisms distributed in the human mind and how they can be activated; the psychological mechanisms are hierarchically organized according to their relevance to deal with environmental adversity Source: Created by the authors.


for myriad and complex relationships and challenges that the environment poses for our species. Challenges include what to eat (e.g., plants and animals), where to look for food, how to treat diseases or cope with accidents with the resources provided by nature, where to take refuge, and how to avoid predators and poisonous animals. The naturalistic mind, as one of the components of the human mind, would also result from the numerous selective pressures of the ancestral or modern environment to which our species is subjected. One of the first studies using the concept of naturalistic mind found that the human mind favors the recovery and storage of information about diseases and plants associated with their treatment, when these diseases are frequent in the social system (common diseases) or related to previous experiences of the individual (Silva et  al., 2019). The authors expected to find that serious diseases, those normally debilitating or fatal, would be favored in memory. However, this was not the case. The modulation of the


frequency of illness with previous experience suggests that there is, in fact, a hierarchy in the mind. Interestingly, a similar pattern is observed in relation to other phenomena, such as when people deal with environmental hazards or catastrophes (see Ruin et al., 2007; Miceli et  al., 2008; Gibbons and Groarke, 2016). This led Ferreira Júnior et al. (2019) to formulate the Principle of Regularity. According to this principle, the human mind is biased, because it is organized based on the regular events of our experience. Box 5.1 summarizes what we know about the naturalistic mind.

Does the Past Explain the Present? Human Beings and Landscapes Landscapes can be defined as the space of interaction of people and environment. The way humans relate to them may reveal strong evolutionary roots. The Biophilia hypothesis proposes that people possess an innate

BOX 5.1 Structure and behavior of the human naturalistic mind  Origin • The naturalistic mind is the fruit of all selective pressures along the hominid lineage in evolutionary environments. Thus, evolved psychological mechanisms respond to different environmental challenges, that is, they are not necessarily tied to a particular environment (such as the Pleistocene savanna). • Memory, as one of the components of the naturalistic mind, prioritizes content with adaptive bias, organizing content hierarchically. Thus, information related to environmental survival can be prioritized over other adaptive information. This means that ancestral hazards will not necessarily be prioritized to the detriment of modern hazards. Physiology • The naturalistic mind, as shaped during evolution, can lead our species to experience adaptive lags. However, as cultural responses operate faster than biological evolution, human activities of niche construction can modulate the existence or not of adaptive lags. • Possible mental responses generated in the ancestral environment can be modulated by the individual’s previous experience with a given phenomenon. • The frequency (regularity) of a given phenomenon biases cognitive processes associated with the naturalistic mind, so that less common or rare phenomena tend to be neglected unless they are modulated by previous experience.



emotional and affective predisposition to living things, whether they are animals, plants, or processes (Wilson, 1993). People tend to prefer images of natural environments to urban environments and these images are more likely to be preferred when they contain trees (Ulrich, 1993). In addition, humans process visual stimuli from nature more efficiently than from urban environments. This can elicit favorable feelings and emotions to natural landscapes (Townsend and Barton, 2018). For example, when contemplating a landscape, whether urban or natural, people elicit emotional responses that may lead to positive or negative attitudes towards that landscape (see Bargh et al., 1992). Evidence has shown that some people appreciate landscapes containing lakes or rivers (Ulrich, 1983), and feel more freedom in environments with exuberantly green vegetation than in urban landscapes (Hartmann and Apaolaza-Ibáñez, 2010). These affective reactions can be the result of aesthetic aspects of the landscape (e.g., perceived naturalness – how close a given landscape is to its natural state – presence of water, complexity) or of evolutionary aspects, as proposed by the Biophilia hypothesis (Wilson, 1993; Han, 2007; Ode et al., 2009; Lee and Son, 2017). The affinity of human beings with living elements may be the result of the continuing relationship of hominids with nature during their evolutionary history. This affinity may influence aspects of human cognition related to the use and management of natural resources (Albuquerque and Ferreira Júnior, 2017) as well as emotional responses and preferences for aesthetic components of nature. In this case, some natural scenarios stand out more than others (Orians and Heerwagen, 1992). For example, studies have shown that inhabitants of countries including Australia, Nigeria, South Africa, the United States, Estonia, and Italy, among others, prefer open landscapes with sparse trees with wide and stratified canopy, which are characteristic of the African Pleistocene savanna (see Orians and Heerwagen, 1992;

Sommer, 1997; Summit and Sommer, 1999; Herzog et al., 2000; Falk and Balling, 2010). Orians and Heerwagen (1992) suggest that this preference has an evolutionary origin and results from the importance of the savanna environment for hominid survival during the Pleistocene. The savanna offered the first humans a set of possibilities (e.g., a panoramic view of the open environment and trees that were easy to climb) that helped them to escape from predators, search for food, and shelter under their canopies (Appleton, 1975; Orians and Heerwagen, 1992; Townsend and Barton, 2018). The savanna may have played a relevant role during human evolution, but not the most prominent. Since we inhabited other environments with different challenges in the Pleistocene, survival strategies for the savanna have been potentially modified, improved, and combined with other strategies or even abandoned over time. According to Tooby and Cosmides (2015), the period during which we were hunter-­ gatherers in paleoenvironments was crucial for the evolution of our mind. Evolutionary processes are slow and need hundreds of generations to build a highly complex ‘mental’ program. That is, human minds would still be adapted to the world of our ancestors. According to these authors, ‘The industrial revolution – even the agricultural revolution – is too brief a period to have selected for new neurocomputational programs of any complexity’ (Tooby and Cosmides, 2015: 19). People commonly experience an adaptive delay when facing the challenges of industrialized societies, because these environments are different from the environment in which we evolved. For example, the taste for fatty foods is an adaptive behavior for ancestral environments, in which fat was scarce, but is nonadaptive in the current environment because it increases the incidence of cardiovascular diseases (Cosmides and Tooby, 2003). The influence of past heritage on the interaction of people and landscapes and, consequently, the existence of adaptive lags has been debated by scholars. Some argue that this


argument overlooks evolutionary processes that have enabled the reproductive success of humans, such as the ability to adjust to varying and variable environments in which they live (see Laland and O’Brien, 2012). Laland and Brown (2006) argue that humans do not experience adaptive lags, precisely because they have the ability to build and rebuild key components of their environments to suit their needs. This adaptive capacity of humans and other organisms is understood as niche construction, which occurs in response to the environmental challenges created by their ancestors (see Lewontin, 1982; Odling-Smee et al., 2003; Laland and Brown, 2006; Laland and O’Brien, 2012). For example, even if there is excessive consumption of fatty foods, humans create niches to solve this problem, such as the development of drugs and the practice of physical exercise. Due to the cultural and environmental diversity in which we live and develop, the preference for landscape among humans is also diverse. For example, the preference among the Japanese for landscapes of feudal gardens in urban centers varies according to the distance to buildings and also to personal life experience (Senoglu et al., 2018). Colley and Craig (2019) observed that, in Scotland, if people perceive a landscape as natural (i.e., with little human intervention), the emotional attachment to the landscape increases, influencing their preferences. In addition, people living in China prefer environments with a balance between wild nature and human constructions, such as channeled streams in native vegetation (see Hu et al., 2019). Thus, recent environmental factors can influence innate human preferences for landscapes.

How Does Our Mind Deal with Information about Other Living Things? In their interactions with environments, humans had to deal with dangerous events that threatened ancestral survival. Learning


strategies such as trial and error may have been important in order to avoid such threats over time. However, trial and error are not always advantageous because the learning costs increase in situations such as contact with poisonous animals. In this context, strategies that favor the learning of certain information from the environment may have been selected (see Rendell et al., 2011; Barrett and Broesch, 2012). For example, early hominids that remembered and quickly learned how to avoid certain components of the environment (e.g., dangerous animals) and how to recognize and select natural resources (e.g., fruits) would have an advantage over others who did not possess such skills or behaviors. In the Biophilia hypothesis, Wilson (1993) proposes that the behaviors of approaching (biophilia) and avoiding (biophobia) certain components of the environment may have a biological, evolutionary basis. These behaviors result from natural selection to promote the survival of humans in their interactions with the environment (see also Kellert, 1993). Chief among the biophilic interactions is the demand for food in the ancestral environment. Rozin and Todd (2015) argue that, during human evolution, the need for food and nutrients demanded more time and cognitive effort than other activities performed by hominids. Selecting food is critical to the evolution of the human mind and structuring the culture, but is not an easy task. This activity requires caution in avoiding the ingestion of toxins and other non-nutritive substances. It was essential to differentiate the toxic from the nutritious. This has led humans to specialize over time, through natural selection (Rozin and Todd, 2015). Although the human–food interaction during evolution is a promising way to understand our cognitive structure – and a matter of great interest to evolutionary ethnobiology (see Albuquerque and Ferreira Júnior, 2017) – this subject is still neglected in the field of evolutionary psychology (Rozin and Todd, 2015). Evidence suggests a bias in human memory towards learning information related to



dangerous animals, as we have previously mentioned. Broesch et  al. (2014) evaluated memory retention of information related to the danger of animals (e.g., if they were poisonous or not), diet, and habitat in indigenous young people and adults of the Fiji Islands. They observed that information about hazard and toxicity was best retained by young people, whereas adults showed no preferential retention for this information. In contrast, other studies have indicated that the use of images of dangerous animals can increase the retrieval and retention of information in adults (Kock et al., 2008; Riaz et al., 2018). In addition to retrieving information from memory, humans may possess other characteristics that respond quickly to dangerous animals. Neurobiological studies have indicated that the amygdala of primates, including humans, is able to tune visual areas of the brain to perceive fear-related stimuli (see Prokop and Randler, 2018). Studies on visual attention have shown that dangerous animals, such as lions and snakes, more quickly capture and maintain the attention of humans than non-dangerous animals (Yorzinski et al., 2014). Infants at five months of age stare longer at images that schematically represent a spider than images with random schemata (Rakison and Derringer, 2008). This may reflect an evolved response to detect more quickly and to focus attention on dangerous animals (Yorzinski et  al., 2014; Prokop and Randler, 2018). According to Tooby and Cosmides (2015), this fact could also explain modern phobias associated with these animals. However, these responses are culturally modulated. For example, Maasai people in Kenya evaluated lions as aesthetically more attractive than hyenas (Pinho et  al., 2014). Lions are of great cultural importance to the Maasai people (Pinho et al., 2014), suggesting that culture can partly modulate human responses to dangerous animals. Aversion to dangerous animals can be learned quickly by observing the reactions of other individuals to these animals. In a study with laboratory-raised monkeys – Macaca

mulatta – Cook and Mineka (1990) showed that young individuals can quickly acquire fear of snakes merely by watching fear reactions of other individuals towards these animals in videos. However, observers were not afraid of flowers after watching edited videos displaying individuals who were afraid of these items. This suggests that fear is more quickly learned when directed at dangerous animals. Similarly, babies aged seven to 18 months paid more attention to snake images when they were associated with a frightened human voice than with a cheerful voice (DeLoache and LoBue, 2009). Such learning may have been important for the survival of early hominids, as individuals would not need direct experience with dangerous animals to acquire the behavior of avoiding these animals. Adaptive mechanisms are also activated in relation to plants. Prokop and Fančovičová (2014) investigated children exposed to information on toxic and non-toxic plants associated with fruit images of different colors, i.e., red and black for toxic plants and green for non-toxic plants. They found that plant information associated with red- and blackcolored fruits was better retained in children’s memory, possibly due to their association with toxic fruits. A recent study showed that, in a visual detection task, toxic plants were detected significantly sooner than non-toxic plants by humans (Prokop and Fančovičová, 2019). The ability to recall information about plant toxicity may have given humans the ability to identify and avoid foods potentially harmful to their survival. In addition to the behavior of aversion, people also exhibit behaviors that promote contact and interaction with animals and plants (biophilia). People have positive emotional responses towards animals with certain characteristics (Prokop and Randler, 2018). Martín-López et al. (2008) conducted a meta-analysis of 60 studies and showed that people are more likely to pay for animal conservation due to anthropocentric rather than scientific factors. Anthropocentric factors


include animal characteristics preferred by people, such as length, weight, and eye size. Regarding plants, some studies have shown that people prefer landscapes of trees with larger canopies and shorter trunks (for a review, see Townsend and Barton, 2018). It seems this preference may be produced by psychological adaptation. Individuals who had positive sensations in response to these trees were selected because these trees offered them safety and shelter (Townsend and Barton, 2018). The degree of interaction of people and nature may promote positive behaviors directed at other animals. A study in China found that children living in rural areas and having more contact with nature were more likely to protect and like animals (biophilia) than children from urbanized regions (Zhang et  al., 2014). Zhang and colleagues suggest that contact of humans with nature can help to promote conservation strategies. Sampaio et  al. (2018) observed that the contact of children with forests influenced their knowledge of local biodiversity. The children were encouraged to express their knowledge as drawings, and the authors found that children who had more contact with forests also had greater knowledge about native animals of the region. According to the authors, the proximity of children to the forest drew attention to the components of this environment, laying the foundations for the construction of knowledge. This fact indicates that the environment in which human beings live can influence their cognition, and is responsible for promoting and mediating human behaviors, such as being prone or not to preserve nature.

FUTURE CHALLENGES FOR ENVIRONMENTAL SCIENCES Penn (2003) offered a synthesis of a number of evolutionary approaches that provide insight into human nature and its role


in current environmental events. For Penn, population growth is one of the major current ecological issues – there are around seven billion people on the planet – and creating effective public policies to stabilize this growth requires understanding the evolutionary roots of the problem. From an evolutionary perspective, reproductive self-regulation should be expected as the high demographic rate disturbs population and environmental balance – as advocated by the Demographic Transition Theory – as this adaptive response provides the best chance for survival (see recent discussion in Brooks et  al., 2019; Salvati et al., 2019). However, in some traditional societies, reproductive success is positively associated with wealth increase, whereas in rich developed countries, fertility tends to fall as their people opt to have fewer children to improve their quality of life (Penn, 2003). Therefore, more studies are necessary, analyzing the influence of evolutionary and cultural factors on current demographic dynamics. Another aspect to be considered when developing policies to deal with long-term environmental threats is discounting the future, that is, the limitations humans have in considering environmental problems that may arise in a distant future, putting more emphasis on the present day (Penn, 2003; Henry et  al., 2017). In this case, natural selection may have favored hominids that discounted the future, as life expectancy was relatively short and the future uncertain, making it crucial to focus on present needs, which increased individual survival and reproductive success (Penn, 2003). Thus, a good conservation strategy would be to associate time discount rates to nature conservation policies, as that may provide more realistic expectations of human response to these policies (Henry et al., 2017). Moreover, humans tend to use natural resources according to their own interests, putting societal interests in second place, potentially leading to resource exhaustion (Penn, 2003). This kind of behavior was



proposed by Hardin (1968) as the tragedy of the commons. For instance, a study by Scheiter et al. (2019) showed that, in African rural savannas, people use open fields for pasture or hunting intensively, exceeding the optimum level. These authors propose this as an example of the tragedy of the commons that will compromise ecosystem services in the future. However, human populations are able to adapt and to develop rules to effectively manage common resources, avoiding the tragedy of the commons (for a more complete argument, see Šestáková and Plichtová, 2019). In this sense, it is essential to understand the constraints and amplitude of the influence of the evolved psychological mechanisms in the relations of modern humans and the environment. Evolutionary psychology is interested in better understanding not only environmental problems and challenges (having as background the attitudes of human beings) but also how we model our multiple relationships with nature. Penn (2003) argues that we are still moving towards an understanding of environmental problems from an evolutionary perspective. In this chapter, we presented a brief overview of how evolved psychological mechanisms help to understand modern humans. However, just as we move slowly in understanding the environmental challenges generated by human activity, our understanding of other aspects of the relationship between human beings and the environment is still in its infancy. We believe that dialogue with other fields in science can be fruitful for a better understanding, from an evolutionary point of view, of the relationship between humans and the environment. An evolutionary perspective is not exclusive but provides an alternative or additional point of view. Evolutionary ethnobiology is a newly systematic science (Albuquerque and Ferreira Júnior, 2017) that shares this interest in understanding the ecological and evolutionary history behind our relations with the environment.

ACKNOWLEDGMENTS This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. We thank the CNPq for the productivity grant awarded to UPA.

Note 1  The process where organisms, through their activities and decisions, modify their own and other’s environments. The environmental modifications generated by the niche constructors influence the selective pressures of their environment and can lead to changes in their metabolic, physiological, and behavioral activities (Odling-Smee et  al., 2003; Laland and O’Brien, 2012; Flynn et al., 2013; Matthews et al., 2014).

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6 Evolutionary Psychology and Public Health Simon Russell

INTRODUCTION: PUBLIC HEALTH AND THE OBESITY PROBLEM Public health has been defined as ‘the art and science of preventing disease, prolonging life and promoting health through the organized efforts of society’.[1] Public health is an interdisciplinary science, which aims to promote the length and quality of human life through the prevention and treatment of disease. Whether relating to physical, mental, or social health, public health seeks to translate highquality research into preventative or curative practice. The field of public health also recognises a positive value arising from good health, which incorporates concepts of psychological and emotional well-being. While selection does not act to promote longevity, evolutionary fitness is profoundly affected by morbidity and mortality[2] and both health outcomes and evolutionary fitness are notably predicted by socioeconomic status in the developed and developing world.[3,4] While there is a

complex relationship between human fertility, fecundity, and fitness,[5] good health is recognised as a key dimension of evolutionary fitness[6] and has a greater impact on fitness than age-specific fertility.[7] However, selection does not act on health and it is possible to be a public health success but an evolutionary failure; one may lead a long and healthy life but fail to reproduce. Equally, one may be an evolutionary success and a public health failure; it is possible to reproduce successfully from a position of poor health. Despite public health and evolutionary success being defined by and measured in different currencies, applying the principles of evolution to the discipline of public health may provide original insight for policy makers and practitioners. Evolutionary science has been increasingly applied to various disciplines within the field of public health, including reproductive health, immunity, infectious diseases, cancer, and mental health.[8–11] This chapter explores the utility of applying the principles of evolutionary



psychology to the most pervasive physical health problem of the modern world, namely, non-communicable diseases (NCDs). The primary focus will be on pathological health risk behaviours, which greatly enhance the risk of NCDs. Additionally, a case study presents the relevance of evolutionary decision making in health-promotion behaviour, within the context of vaccinations and protection from communicable diseases. Comprising cardiovascular diseases, cancers, chronic respiratory diseases, and diabetes, NCDs are preventable but account for 41 million or 71% of global deaths annually.[12] The main risk factors for NCDs are poor diet, physical inactivity, tobacco use, and harmful alcohol use.[13] Harmful alcohol use, smoking, poor diet, and physical inactivity can be understood as health risk behaviours, which lead to potentially pathological metabolic and physiological changes. Poor diets typically involve consuming energy-dense but low-nutrient food and drinks. Low nutrition and overconsumption often co-exist and are typified by eating foods that are high in fats, sugars, and salt (HFSS). Overweight and obesity are typical consequences of poor diet and inactivity and will be considered as key pathological outcomes for the purpose of this chapter. The principles and public health response discussed here for overweight and obesity are also potentially relevant to harmful drinking and smoking, since it will be argued that similar psychological mechanisms and evolutionary strategies underpin and govern multiple health-risk-taking behaviours (for usage and definitions, see section ‘Psychological mechanisms and evolutionary strategies’). Overweight and obesity has become perhaps the most prevalent and burdensome public health problem of the modern world. Overweight and obesity rates in adults have tripled since 1975, and in 2016 there were 1.9 billion (39%) adults globally living with overweight or obesity.[14] Rates of childhood obesity have risen 10-fold over the same period, and in 2016 there were an estimated 340 million children aged 5–19 years living

with overweight and obesity.[14] Living with overweight and obesity greatly increases the risk of Type-2 diabetes, cardiovascular diseases, and various forms of cancer,[15] in addition to many other physical and mental health problems. Obesity can be conceived as both very simple and as highly complex. A positive energy balance can be thought of as an equation: energy in, use by metabolic processes, and energy out. Even a slight but consistent positive imbalance would accrue overweight and obesity over time. Conversely, there is almost nothing we do in our lives which does not affect our energy balance and obesity. The Foresight obesity systems map[16] categorises, maps, and illustrates the varied and complex determinants of obesity. There is limited utility in focussing on any one part of the map, given that the obesity system is dynamic and any change to one part of the system will have consequences for other parts. Public health responses can sometimes be simplistic; interventions may attempt to adjust one determinant in some way, while controlling for others, and practitioners and policy lobbyists can become focused on just one element of the map. In turn, the public and the media sometimes misunderstand the problem and oversimplify what is perceived to be an effective policy response. Furthermore, there is no consensus between academics or civil servants on where the public health focus should be. Some suggest the problem lies with ‘energy in’, since evidence suggests physical activity may not help people lose weight, while others focus mainly on ‘energy out’ given that physical activity has been shown to attenuate the risks of NCDs, even for people living with overweight or obesity. The causality of obesity has drawn similar debate in terms of the relative impacts of our genes and the environment and the interplay between the two. Broadly speaking, the effects of heredity in obesity are likely to be low, given that obesity has grown rapidly in genetically stable populations. However, there is some evidence to suggest that biological influences account for large proportions



Figure 6.1  The impact of the food supply on the expression of obesityi[19]

of variance in food and satiety responsiveness and therefore risk of obesity. Yet the more we understand about genetic susceptibility, the more the importance of the environment has been revealed; the expression of susceptibility to obesity in environments with a limited food supply is low but becomes hugely amplified in environments with an abundant supply (Figure 6.1).[17] Generally, diseases rarely have simple Mendelian patterns of inheritance; heritability of ill health is more commonly the product of interactions between multiple genes, predispositions and the environment, and socioeconomic and cultural influences.[18] While genetic predispositions are likely to exacerbate or attenuate the risk of obesity, the problem is recent relative to human history and has coincided with industrial and urban modernisation, which provide the obesogenic platforms from which genetic susceptibility may be expressed.

MAKING EVOLUTIONARY SENSE OF THE MODERN WORLD The majority of people now live in surroundings that are very different from the selective environments in which we evolved. With tech-

nological and civil development, many physical and psychological adaptations that are rooted in evolutionary time have become mismatched with modern life. Obesity is perhaps the most pronounced physical manifestation of this mismatch; it has increased in almost every country in the world, and is reported to be proximally driven by changes in the food system, where calorie-dense food is abundant, affordable, and readily available in most of the modern world.[20] Built environments have also changed and influence what and how much we eat, in addition to the energy we expend; energy-saving mechanisms are integral to modern civic design. Modern living has become increasingly urbanised; in 1950 there were 751 million people worldwide living in urban areas, compared to 4.2 billion in 2018, which is 55% worldwide but as high as 72% in Europe and 82% in North America.[21] Urbanisation is relevant to the obesity epidemic; research suggests that a lack of green space and recreational facilities, perceived unsafe communities, and high-density populations can be risk factors for obesity.[22] Urbanisation is also relevant from an evolutionary perspective; community and kin networks have been replaced in urban environments by small living units or nuclear families, typically with non-kin neighbours.[23]



In our ancestral, selective environment there would have been food scarcity and changeable conditions. In such circumstances it would have been adaptive to maximise caloric intake, especially of food rich in sugar and fat. Our ancestors and traditional populations have evolved to maximise their foraging success and net energy intake,[24–26] and, therefore, their health and evolutionary fitness. Adaptations that motivate preferences for high-calorie foods would have been a consequence and humans are reportedly hardwired to prefer HFSS foods.[27] A mechanism of this adaptation is that energy-rich foods elicit enjoyment in humans, especially when consumed in combination. Various hormones are released when high-energy foods, particularly fats and sugars, are consumed, which stimulate pleasure-associated areas of the brain;[28] ­ similar effects are found with alcohol, cigarettes, and other substances. Humans are also tolerant to food delays, which is likely to be a product of changeable environmental conditions. It seems likely that our ancestors were adapted to maximise energy intake during periods of food scarcity and moderate consumption during times of food abundance. The agricultural and industrial revolutions brought great civil advancement, but food technology and food systems have changed more over the last 50 years than ever before; production and supply of energy-dense and processed foods have increased substantially. Globalisation has resulted in a reduction in price and an increase in availability of high-calorie foods.[20] The modern world for most people affords a constant state of food plenty and, given human preference for HFSS foods, consumption of food and prevalence of obesity have increased dramatically. It is for these reasons that obesity has been described as a normal response to an abnormal environment.[29] The advertising and food industries of the modern world also work to maximise our contact with food or associated psychological cues. So rather than asking why some of us are living with

overweight, the more pertinent question may be, why are some of us not living with overweight? We are conscious that overconsumption is not conducive to good health, and we moderate our behaviour accordingly, but our ability to moderate consumption and other diet-related behaviour varies. If conscious moderation of behaviour is the mechanism by which we prevent overeating, why are so many people making suboptimal and seemingly maladaptive health choices? Perhaps these health choices are not maladaptive at all. There is a long-established link between socioeconomic gradients and health risk behaviours,[30] health outcomes, and mortality.[3] While deprivation predicted food poverty and underweight in the past, in the modern developed world, low socioeconomic status strongly predicts obesity;[31] in turn, living with obesity has been found to exacerbate inequalities.[32] Within the developed world, evidence suggests that relative inequalities are equally if not more important than absolute poverty in predicting problematic health behaviours and outcomes.[33] There are environmental factors that accompany deprivation, which increase the likelihood of obesity. Energy-dense foods represent better calories per unit cost compared to fresh ingredients, which appeals to low-income families.[34] The built environment in areas of deprivation also has reduced green spaces and fewer recreation facilities, such as leisure centres, which limit opportunities for physical activity, increase risk factors for obesity, and widen health inequalities overall.[35] There are also higher densities of fast-food outlets and reduced access to healthier food stores in increasingly deprived areas, both of which are associated with poorer diets.[36] The relationship between disadvantage and obesity is complex and dynamic but, in developed countries, people of lower socioeconomic status are disproportionately affected by obesity.[37] However, obesity is prevalent across all socioeconomic strata and there is variation in overweight and obesity within


similarly deprived areas, which implies that disadvantage only accounts for a proportion of the observed variance.

Psychological Mechanisms and Evolutionary Strategies Psychological mechanisms or modules throughout this chapter refer to functional neurocognitive adaptations that have been successful over evolutionary time owing to their selective value in solving problems and their contribution to survival or reproductive success.[38] In combination and in addition to anatomical and physiological traits, psychological mechanisms create broader evolutionary or behavioural strategies, a clear example being an individual’s reproductive strategy.[39] When originally conceptualised, psychological mechanisms or modules were proposed to be universal among humans but that different mechanisms were invoked in different situations, leading to phenotypic variation.[40] It is proposed here that while some fundamental psychological mechanisms are innate and species-typical, others are more varied across individuals, arising from individual-specific interactions between genetic predispositions and phenotypic plasticity.[41] Neurobiological structures are produced by our genes after thousands of years of selection pressures, which act on individual genes but also the resulting cognitive mechanisms. Physically, the brain is complex, comprising billions of neurons and chemical interactions, but it functions as a specialised system that has been produced by the evolutionary process.[42] The brain acts hierarchically, where functionality emerges as a property of micro- and mesoscopic interactions through coordinated chained structures that run between anatomically clustered areas. [43] For example, the choice to eat a donut would flow through and elicit responses from various areas of the brain: affect and emotion centres, autonomic and conscious


centres, expectation centres, short- and longterm memory,[44] all before a hand has been outstretched. Selection has not acted upon these areas in isolation; the idea of modularity recognises functional specialisations within the brain that are domain-specific and are utilised for different cognitive processes. Whether modularity is strong or weak, any choice and resulting behaviour is the product of a hierarchical chained process that breaks down with impairment of any of the involved areas.[45] Psychological mechanisms are selected in their own right; they may be heritable in a conventional sense, but may also be the product of behavioural and, therefore, phenotypic plasticity, leading to selectable individual variation.[41] Genetic predispositions form the basis of all psychological mechanisms, but they also remain a part of our complex biological systems and are mutually associated with our physiology. For example, and in relation to obesity, adipose tissue is an active organ and part of the homeostatic system that regulates satiation and energy balance. Adipose tissue, the gastrointestinal tract, and the pancreas release various hormonal regulators to the brain, which receives the signals and acts to reprioritise behaviour to stimulate or suppress appetite. There are also physiological detectors for fats and sugars in food, which stimulate pleasure-associated areas of the brain. Elicitation of reward mechanisms also motivates behaviour, to such an extent that homeostatic processes may be overridden. This push and pull creates a trade-off within our energy-balance system, whereby psychological mechanisms, each with a clear adaptive significance, compete at cross-purposes. It is a feature of environments with constantly available energy-rich foods that allow the reward mechanisms to gain the upper hand and enable a chronic positive energy balance. Developmental conditions also affect psychological mechanisms, beginning in utero; these may be physiological, physical, emotional, or sociocultural. Childhood experience has been found to profoundly affect cognitive



development, psychological mechanisms, and therefore behaviour. Neurobiological development occurs rapidly throughout childhood but continues through adolescence and into adulthood. Cognitive systems and pathways that govern behaviour can be affected if areas of the brain suffer impairment during development. Adverse experiences in childhood, including psychological or physical abuse, change the formation of physical structures and neural pathways, which can profoundly affect healthy development and behaviour in later life. These changes can also be irreversible, meaning that the consequences of adverse experiences often persist into adulthood and act independently of socioeconomic pressures.[46] Adverse childhood experiences have been found to contribute to problematic eating behaviours, weight gain, and overweight and obesity in childhood and adulthood.[47–49] The responses to adverse experiences may have adaptive roots; stressors are linked to heightened immune- and nervous-system responses, but continued stress may produce over-activation that is likely to create a platform for poor mental health.[50] Adverse experiences are likely to be accompanied by unstable and insecure food environments, an adaptive response to which may be overconsumption when the opportunity arises. If the consequences of an adverse childhood persist into adulthood, so too would the food response, even when food becomes more consistently available. Psychological mechanisms are also profoundly shaped by environmental circumstances, both physical and, in modern contexts, socioeconomic.[51] Our phenotypes are cumulative developmental outcomes of interactions between our genes and environments. Assuming that the mechanism by which a trait is inherited does not constrain its adaptive value, it is likely that behaviour and the underlying mechanisms are modified in line with environmental variation.[52] While fields such as human behavioural ecology face challenges in testing quantifiable hypothesis in non-traditional or industrialised

countries, it seems logical that behavioural strategies are matched to environmental contexts or circumstances, despite the debatable and nuanced influence of culture. It will be argued here that health behaviour is strategic and adaptive, which would provide the principal reason why seemingly maladaptive choices, such as overeating, are so often taken. There is a wealth of evidence that the health behaviour of industrialised populations is influenced by physical and socioeconomic environments; deprived populations are more likely to have low-nutrition diets, and more likely to engage in a range of other health risk behaviours.[53–54] The trend is not solely economic; even when health behaviours are free, people from increasingly deprived groups have been found to be less likely to engage with them,[30] implying the issue is strategic. The way we perceive our environmental circumstance is also important; perception of income, for example, has been shown to be more important than actual income in determining related behaviour.[55] Living in environments that are to lesser or greater degrees mismatched from those in which we evolved has subtle and complex implications for modern humans. Rates of mental health problems, including depression, anxiety, and stress, have never been higher, especially among young people. Our behaviours act dynamically with environmental pressures; governed by psychological mechanisms and broader strategies, our behaviour is a response to the environment, whether physiological or psychological, which is then experienced and remembered. Our experience leads to learning, which subtly adjusts the psychological platform on which behaviour is based. Just as adverse developmental experiences can impair cognitive functioning, so can more transient states of low mood or poor well-being, and repetition of such states can lead to poor mental health. Similarly, other temporary states such as illness and disease can alter not only our behaviour but our perception of social and physical environments. Low mood and emotional disorders have been


found to affect behavioural strategies, and specifically those related to food consumption and physical activity.[56] The key determinants of psychological mechanisms and, therefore, behavioural strategies are genetic, physiological, environmental, developmental, and subjective (Figure 6.2). These determinants are not mutually exclusive but are linked as part of a dynamic system. For example, phenotypic expression is primarily the product of interplay between genetic predispositions and environmental conditions; physical and socioeconomic environments are inextricably linked but are also associated with developmental and subjective determinants; and developmental and subjective factors also feedback and modify the physiological system. Resulting mechanisms may be fixed, others may be more plastic, varying with changes in circumstances or even mood states. Behavioural plasticity allows us to make different choices and exhibit ­different


behaviours within a changing environment; behavioural plasticity was and remains a huge selective advantage for humans.[57] Our ability to modify our behaviour extends selection beyond psychological mechanisms and the resulting behaviours to behavioural strategies themselves. Such strategies are likely to be adaptive but modifiable both temporally and with changing environments, meaning that physical, political, social, or individual change would be likely to shift the parameters for optimal behaviour. Examples of this can be anecdotally observed every day: a natural disaster, political change, or a dramatic change in personal circumstance are all likely to dramatically shift the behaviour of an individual or collective. Health behaviour strategies are determined more subtly, especially given the sometimes contradictory pressures of health and fitness, but perhaps unhealthy choices are not maladaptive but optimal given the evolutionary context of the choice.

Figure 6.2  Key determinants of psychological mechanisms and behaviour strategies



Adaptive Mechanisms and Optimal Strategies As outlined by life history theory, behavioural optimality is a shaped by a range of problems, including survival, growth, and development. [39] These represent multiple and complex pressures, which underpin choices or decisions that produce variable behaviours. All behaviour, including health behaviour, is the product of a cognitive appraisal system, the process of choosing an action from a range of options with the expectation of maximising the benefit and minimising the cost.[58] The stress-response system functions to mediate openness to environmental inputs and regulate behaviour in a range of fitness-relevant areas. ‘Switch’ mechanisms regulate genetic and environmental influences on phenotypic development; during development, information processed by these mechanisms feeds back and recalibrates the stress-response system, resulting in individual and adaptive patterns of behaviour.[59] Environmental moderators may be social or familial, physical, including the built or natural environment, or socioeconomic, given that there are established gradients in health behaviour across the spectrum of inequality. Temporal decision making provides an example, and in particular the extent to which behavioural strategies are underpinned by impulsive or reflective decision making. Rather than assuming all impulsive behaviour is the absence of control, there is utility in considering a dual system of behaviour,[60] where reflective and impulsive influences exist, are differentially adaptive, and are often in conflict or trade-off against each other.[61–62] A moderator of this system may be developmental factors, that have the potential to inhibit the healthy formation of neurobiological structures, which are important in overriding impulsive mechanisms for behaviour. A good example is the impact of developmental conditions on the functioning of the stress-response system, a biological mechanism involved in a wide

range of adaptive functions.[59] In a health setting, impulsiveness is sometimes considered hedonistic but reflective or rational behaviour involves constraint and is likely to be the product of conscious or higher cognitive control. Hedonic impulsivity may bring a sense of enjoyment and freedom to the human experience,[63] but in a health sense, this often involves long-term costs. Smoking cigarettes, using substances, drinking alcohol, or eating HFSS foods may be enjoyable in the short term but are likely to pose future health risks. Reflective and goal-directed behaviour is often viewed as rational, reasoned, and conscious, utilising volitional control or selfregulation to achieve a goal, while impulsive decisions, despite incorporating a range of behaviours, have been described as suboptimal, an inability to moderate behaviour. Reflective decisions usually have the goal of a larger payoff at a later time point, while forgoing the immediate reward or benefit. In terms of health behaviour, this would be represented by forgoing the immediate pleasure and reward from an action, such as eating an HFSS food, in order that the chances of yielding the longer-term and larger benefit of good health are enhanced. Impulsivity can be interpreted as the forgoing of a large but delayed reward in favour of a smaller but immediate reward.[58] In certain environmental conditions, impulsivity is likely to be adaptive; dangerous environments, for example, where there is an immediate threat or mortality rates are high, are likely to favour short-term and high-risk behaviours.[39] Research supports this theory, demonstrating that people in adverse environments are more likely to discount the future and act more impulsively, despite the potential harm to their health.[64] Impulsive and reflective decision making has also been shown to predict health behaviour in the way we would expect; lower health-risktaking behaviour is associated with increasingly reflective decision making, while riskier health behaviour is associated with increasingly impulsive decision making.[65–66]


Within the field of cognitive psychology, the concept of delay or temporal discounting[67] is used to explore our cognitive appraisal system, specifically relating to the temporal nature of health economics. Delay discounting is the extent to which immediate rewards are declined or postponed in order to gain larger rewards in the future; these constructs create behavioural strategies, which are variable, context specific, and are highly likely to be adaptive. Crucial in the decision are the values of the present and future reward, but also the length of time required or delay in gaining the future benefit; this can be considered as a cost subtracted from the future reward. It is well established that humans trade off between present and future rewards and, as previously stated in terms of food choice, tolerance for delays in foraging may have been selected for in variable environments. It is also well established that humans make temporally optimal decisions with financial or resource-based benefits and costs; the principle of delay discounting has been used to predict various health behaviours, including food consumption, physical activity, tobacco, and alcohol use.[68] The constructs that underlie impulsive or reflective behaviour and delay discounting are psychological mechanisms, which have been selected upon but remain modifiable with changing circumstances of environments. The relevance of these mechanisms and their determinants to the field of public health have not been fully explored but may hold the key to understanding why suboptimal health behaviours are chosen to the point of pathology and premature death at epidemic proportions. Behavioural traits, whether fixed or variable, contribute to broader behavioural strategies and our overall phenotype. Behavioural strategies can become stable in evolutionary terms,[69] but changes to our environment create pressures, which alter learning and lead to new behaviours and strategies. This implies that for a set of environment conditions, including socioeconomic, there is likely to be an optimal


and adaptive behavioural strategy.[70] Within these parameters are individual factors, which may have arisen from biological, developmental, or subjective determinants and may be fixed or transient. Individual states may not alter the objective optimality of a behavioural strategy matched to a set of environmental conditions, but they would alter the cognitive appraisal system and the perceived costs and benefits in temporal decision making. Like adverse developmental conditions, strategies that favour short-term payoffs and immediate rewards may have adaptive roots. In states of high anxiety or depression, it may not be optimal or even possible to think about long-term benefits; it is likely that for someone suffering from a mental health disorder, temporal perception may be very different to someone of good mental health and the cost of waiting for a reward may be perceived to be much higher. Such individuals may still be behaving optimally and adaptively, upon consideration of the determinants of their psychological mechanisms, the internal influences on behavioural appraisal, and the social, physical, and socioeconomic environment. These ideas can be further evidenced by considering behavioural strategies that have established evolutionary significance and their relationship to currencies of health. Risk taking or aversion is adaptive in various ancestral and modern contexts and has relevance to health. While there are broad differences in risk-taking behaviour between age and gender groups, strategic variation can also be observed. Life history theory predicts that decisions relating to energy allocation and behaviour are divided between competing functions, such as growth and reproduction, which are affected by ecological pressures, the differential proportion of which result in diverse health outcomes.[71] Consider the relationship between wealth and reproduction – increasing wealth predicts higher long-term fitness and reproductive success but a trade-off also exists between the number of offspring produced and the



wealth transmitted to each; this balance has been found to be predicted by socioeconomic and environmental conditions.[39] Accruing wealth in the developed world requires time and career focus, which is time spent away from having and raising children; women in particular face a decision of how much wealth to accrue before having children. Accruing wealth is desirable but there is risktaking relevance given that fertility decreases with increasing age. Risk-taking decisions can also be observed more directly in a health setting. The choice to forgo protection during sex, such as a condom, is risky given the increased chance of getting an infection or an unwanted pregnancy. However, unprotected sex is more pleasurable for men and women, and represents a reward to counter the risk; research has shown that the greater the perceived pleasure differential, the more willing men and women would be to engage in unprotected sex.[72] Similarly, eating HFSS foods, drinking alcohol, or using other substances can also be pleasurable in the short term but each behaviour incurs long-term risks to morbidity and mortality. It is also well established that health risk behaviours cluster together,[73] implying there is an underlying risk-taking strategy for any individual within a specific set of circumstances. Varying strategies of health risk, as shaped by external factors, can also be illustrated in financial terms. Low-income workers have been found to be less likely to participate in insurance schemes, even when large subsidies are offered.[74] Despite the losses of not having insurance being potentially ruinous, low-income workers are less likely to participate because they have less to spend and, crucially, less to lose. Conversely, gambling and playing the lottery is more popular among poorer groups;[75] although the chance of winning is slim, the relative reward is higher for someone who has less. One could predict that people in adverse circumstances, whether environmental, developmental, or subjective, would devalue future payoffs as the cost of waiting is perceived to be higher given the

immediate adversity or danger. In this case, it makes sense to opt for shorter-term rewards and payoffs. Chances of survival have been found to profoundly shape reproductive strategy,[39] and are likely to affect strategies relating to health or wealth in a similar way. An individual’s life history reflects trade-offs in the allocation of time or energy, and may be categorised as slow or fast depending on the environmental conditions and perceived time horizons.[76] Preferable environments are likely to induce slower or longer life histories, which are associated with higher investment, lower impulsivity, and lower levels of risk taking. Conversely, shorter life histories are associated with future discounting, impulsivity, and risk taking.[76]

APPLICATIONS OF EVOLUTIONARY CONCEPTS TO PUBLIC HEALTH PHENOMENA Investing and offsetting decision making is fundamental to impulsive and reflective decision making and may be applied to various health behaviours. Exercise can be considered as investing behaviour; while there may be short-term rewards for some people, costs are involved in the form of time and energy. The investment is made with an idea that there will be a reward of good health and potentially a long-term benefit of longer life. Buying healthy foods can also be considered as an investment; fresh ingredients tend to cost more and usually take more time to prepare but they may represent a similar longterm goal to that of exercise. In many societies, health insurance represents an investment; it may be part of a healthcare system or it may represent a better level of care. Like risk-aversion behaviours, these decisions are more likely to be taken by individuals who have the financial means but also who perceive the long-term benefits to be worth the investment. For those who do not have the means or think in temporally


shorter terms due to adversity in one or more areas of their lives, investments are less likely to be made. Offsetting behaviour can be thought of in similar but subtly different terms; instead of immediate investment costs being incurred, immediate rewards are rejected but still with the expectation of higher rewards in the future. Choosing not to eat HFSS foods, drink alcohol, or use substances are examples of offsetting behaviour as they are immediately pleasurable but in accumulation are likely to incur risks to longterm health. Altruistic and cooperative behaviours also have relevance to health. In ancestral environments, altruism may have evolved partly in response to foraging and food sharing; evidence has shown higher levels of altruistic behaviour to be associated with better health and well-being. Cooperation has relevance given that sharing resources equally allows for moderation and fairness but requires trust that community members will not take more than their fair share. The global food industry is a good example of non-cooperative behaviour whereby nation states or companies compete to gain as much market share as possible. Such competition has led to over-farming and fishing, which have led to environmental destruction. Huge production and advertising of processed HFSS foods within a global market have also pushed consumption to the point that the majority of the world’s populations live in countries where they are more likely to suffer mortality from the consequences of living with overweight than living with underweight.[77] These pressures operate in a similar way to the other health-relevant evolutionary behaviours, whether for individuals or larger organisations. Longer-term rewards that may be gained with altruistic and cooperative strategies are not optimal given the context, in this case the free-market food system. The optimal strategy for an individual, company, or nation state in such circumstances is to take the immediate payoff or reward. Extreme examples of adverse developmental, subjective, and environmental


circumstances can help to illustrate how extreme behaviours might make sense in terms of the adaptive appraisal systems that underpin them. Victims of childhood physical or sexual abuse commonly grow up to suffer poor health outcomes; not only is cognitive development impaired, potentially leading to reduced reflective decision making, but the immediate reward that may be provided by an unhealthy behaviour would almost always outweigh the cost of waiting for a larger future reward. Individuals who suffer from mental health conditions could make a similar appraisal; for a person living with severe depression, for example, potential benefits in the distant future may feel completely irrelevant. In these examples, the immediate reward could be alleviation or self-­medication from the ongoing costs of extreme low mood. These unhealthy behaviours, which incur long-term risks to health and fitness, are uniquely adaptable in that they may be survival mechanisms. Consider populations living in extreme environmental conditions such as war or within violent gang culture. Individuals are aware that their chances of survival are reduced, which diminishes the value of any future reward as they may not live to benefit from it. Shortterm strategies would always be optimal in situations such as these since the rewards of tomorrow may never come. For any individual, health behaviours can be better understood if framed as adaptive strategies that can be predicted by environmental, developmental, and subjective circumstances. Early exploratory work has demonstrated that environmental conditions shape the strategies that drive health behaviour and that such strategies are predictive of various adaptive or evolutionary strategies. [70] Public health practitioners understand the determinants of poor health but there is little acknowledgement that there may be circumstances in which it makes more sense to undertake unhealthy rather than healthy behaviours. Under such circumstances, it seems pointless to try to change the behaviour itself, if



the underlying strategy is not acknowledged and the determinants of that strategy are not addressed. Such an approach may also widen the public health perspective. Often academics and practitioners operate in silos, focusing on specific health risk behaviours, interventions, or risk factors for disease, but perhaps the problem needs to be re-framed. In addition to addressing the morbidity arising from obesity, how can we triangulate research and practice to reduce the risk factors for NCDs more broadly? A key element of this challenge may be seeking to address the determinants of health risk behaviours. The public health response must be informed, paradigms may need to be challenged, and we will need a whole system and population approach to address a whole system and population problem. Given the complexity of the problem, no simple solution is likely to be successful and each of the key determinants of unhealthy behavioural strategies need careful consideration. In public health, it is understood that prevention is better than cure and this is especially true with the obesity problem. We understand how important and formative developmental experiences are, and that the impact of adversity may be irreversible in terms of cognitive structures and resulting behaviours. In a similar way, the public health response to the obesity problem must begin from pregnancy, and carry on through early years, childhood, and adolescence, given that nurturing environments with healthy parent–child bonds are crucial to long-term health. Everything is important in early life from breastfeeding and weaning to a healthy school environment and safe, enabling communities. Children who live with obesity are likely to become adults who live with obesity, and adults very rarely sustain weight loss. In addition to meeting health recommendations for early life, it is our developmental experience that can profoundly affect our shortand long-term behaviours. Creating positive childhood experiences is a complex societal challenge but it must be recognised as critical

in addressing the obesity epidemic and other major risk factors for NCDs. Developmental experiences often contribute to subjective issues that continue to underpin unhealthy behavioural strategies in adults but, equally, poor adult well-being or mental health problems can be triggered by life circumstances at any time. Recognition and appropriate treatment are hugely important not only to treat the disorder but also to re-balance the appraisal system that favours short-term rewards but has consequences for long-term health. Mental and physical health are often treated separately but are inextricably linked and are often cyclical. We cannot expect an individual to make choices that are good for their long-term health when they are struggling to cope with the here and now. Further to developmental and subjective determinants, the environments in which we live must be adapted to address key public health problems and particularly obesity. There is a clear need to create local physical and social environments that are conducive to good health; there are multiple and varied features of our home, social, and work environments that affect our health and well-being. However, there is a bigger challenge to enabling good health, and it lies in the industrial, political, and philosophical climate in which we live. We are the objects of a free-market food system in which the primary objective of any company is to make money and grow, not always but often at the expense of ill health and a burden of disease. The food system is incredibly complex but as long as companies large and small are permitted to produce unhealthy products, saturate the market, and advertise ubiquitously, we cannot hope to shift the behaviour of populations in a meaningful way. There has been a helpful paradigm shift among academics and public health experts, who now consider it unreasonable for populations to achieve and maintain a healthy weight through individual agency alone. Powerful regulations for industry must be demanded by the public and actioned by policy makers, if we are to tackle the obesity epidemic in a meaningful way.


Perhaps more importantly, the greatest challenge of our time is to reduce socioeconomic inequalities. At a population level, individuals from relatively poorer groups make unhealthier choices, these choices are likely to be underpinned by behavioural strategies, and it is likely that these strategies are adaptive. Trying to change the outcomes of the behaviour is unlikely to be effective without consideration of the environmental conditions that determined the strategy. Reducing inequalities is a global problem and requires unprecedented change but in terms of the public health response, interventions and policies must be careful that they reduce rather than exacerbate inequalities. For example, when dealing with obesity, nationwide policies that address issues such as pricing are likely to reduce inequalities, while person-focused interventions that encourage behaviour change are likely to widen them. [78] Health disparities are the most serious outcome of socioeconomic inequalities, the reduction of which will certainly require an understanding of the implications and applications of evolutionary principles.[79] These broad discussion points do not overlook the huge amount of academic and public health work that contributes substantially and meaningfully to addressing obesity and other health problems. The object here is to suggest that an evolutionary perspective of health risk behaviours may be helpful, given that they are likely to be optimal and adaptive. Recognition of the strategies that drive unhealthy choices, and the key determinants of them, will not only encourage a focus on the root causes of health problems,[2] but might also reduce the stigmatisation of health risk behaviours and the individuals that carry their burden. An engrained mantra of public health is to ‘make the healthy choice the easy choice’ but in evolutionary terms the easy choice is the adaptive choice; perhaps we have known for some time that health risk behaviours are a normal response to an abnormal world.


EVOLUTIONARY PSYCHOLOGY AND PUBLIC HEALTH: CASE STUDY – VACCINATIONS For over 200 years,[80 ] vaccinations have prevented the consequences of disease for millions of people worldwide. Vaccines are a public health success story and are estimated to have saved at least 10 million lives between 2010 and 2015 alone.[81] Vaccinations stimulate an immune response from the body to develop resistance to a pathogen, which can lead to the prevention or complete eradication of an infectious disease.[82] Vaccines have successfully led to the worldwide eradication of smallpox and widespread eradication of measles, polio, and tetanus. Other standard vaccine-­preventable diseases include diphtheria, whooping cough, mumps, rubella, influenza, and hepatitis, but there are many other infectious diseases that have available vaccines. Vaccines are a basic human right and have greatly reduced the burden of disease[83] but despite this success, a determined antivaccine lobby, representing an increasingly sceptical world view of science, is on the rise.[84] The antivaccine movement has gained traction online and is suggested to be well organised and widely dispersed.[85] Antivaccine messages question vaccine safety and effectiveness and have been reported to rely on strong emotional messages to enhance their appeal. [86] For this reason, a minority of antivaccine advocates have been suggested to have a highly persuasive voice and the potential to persuade millions of parents against vaccinations on scientific, ethical, and political grounds. Medical and academic experts have tried to counter such messages to advocate the safety and importance of vaccines but have often suffered ‘harassment campaigns’, typically via social media by vehement antivaccine activists.[87] While the most effective strategy at combatting this problem is unclear,[88] the antivaccine movement represents a difficult and complex challenge for public health policy makers and practitioners.



While the academic consensus is that the antivaccine movement is based on misconceptions,[89] there have been controversial studies reporting links between vaccinations and disability and disease, such as autism and asthma, despite strong evidence to the contrary.[90–92 ] Emotive online pressure and spurious evidence have succeeded to some degree. In the UK, the link with the measles, mumps, and rubella (MMR) vaccine and autism appears to have gained momentum and, following year-on-year increases from 2007, decreases in coverage were recorded in 2016/17 for the third year in a row.[93] In the United States, while the overall rate of vaccination coverage has remained high, the rate of children not receiving any vaccinations has been increasing since 2011.[94] The consequences of the growing antivaccination movement have already been observed; analysis of a measles outbreak in the United States in 2015 indicated that the likely cause was lack of or incomplete vaccinations.[95] Multiple developed and developing countries have experienced outbreaks of measles in recent years,[96–97] which have been primarily attributed to gaps in vaccination coverage.[97–98] Research suggests that framing public health messages within the context of the moral foundations that underpin judgements can successfully influence attitudes.[99] Moral foundations theory proposes that internal decision making predicts social group attitudes.[100] While there is complexity surrounding decision-making processes, consideration of selective pressures and evolutionary principles that underpin motivations may provide an enhanced understanding of public health decision making. The incentive to vaccinate is clear; it leads to individual and group immunity and is the best defence against potentially epidemic diseases. If sufficiently high proportions of people vaccinate, herd immunity[101] can be achieved whereby a whole population becomes resistant to a parasite or disease. The coverage threshold varies by disease

but is less than 100%; estimates suggest that for a disease such as measles the herd immunity threshold is 93–95%; for diseases such as smallpox or polio the threshold is 80–86%.[102] Aside from the questionable links between vaccines and disability or disease, there are various risks involved with vaccinating, typically low-level side effects. Vaccines can be painful and create soreness and swelling, and in some cases they can also induce allergic reactions and subjects may become a little unwell. Individual and population immunity is a clear benefit of vaccinations, while the risks and side effects can be interpreted as costs. An application of the principles of evolutionary psychology can add insight into the decision-making process of whether or not to vaccinate. Altruism is an act that benefits others (non-kin) at expense to the actor,[103] and cooperation, like altruism, provides a benefit to another individual or group but does not require reciprocation since it also yields direct or indirect fitness benefits to the actor.[104] The process of vaccinating does not neatly fit with either principal definition; it is altruistic in that a cost is incurred and the process benefits others, but it is also cooperative in that it yields direct fitness benefits to the actor. Vaccinating involves elements of altruism and cooperation; the commonality between the two is reliance on others to maximise individual and group benefits. However, within populations counter strategies may occur arising from selfish or cheating behaviours that yield benefits to the individual with no personal cost but with an expense to others. Cheating strategies may often lead to higher relative fitness than altruistic strategies[105], but if caught, cheats are likely to be punished. Emotional mechanisms have evolved, including moralistic aggression, trust, suspicion, and dishonesty, a function of which is to regulate decisions and behaviours relating to altruism and cheating.[106] Cheating, free riding, or bandwagonning have been found to motivate vaccination decisions[107], and across


a large population, cheating is incentivised given that benefits from herd immunity can be realised without paying the individual costs, assuming that the proportion of free riders does not exceed the threshold. One would expect a successful cheating strategy to not only be hidden but to outwardly support vaccinations, in order that others vaccinate and herd immunity is maintained. Yet there appears to be a maladaptive cultural phenomenon whereby, far from being hidden, not vaccinating or cheating in an evolutionary sense is publicly advocated and promoted. It may be that cultural misinformation has shifted the perceived benefits and costs to such an extent that the adaptive strategies of vaccinating or free riding have been abandoned in favour of a wholly maladaptive strategy. This is likely to be an example of humans being adaptively mismatched from a technologically developed world; our psychological mechanisms that strategize our behaviour may be fundamentally misinformed leading to suboptimal decision making. Vaccinations are a relatively recent phenomenon and were not a feature of our formative and selective environments, but our ability to make adaptive choices in novel situations is a key feature of our behavioural plasticity. It seems likely that a successful public health response will need to change the parameters of the game in order that modern humans can once again make sense of their world. Perhaps a consequence of living in urban populations rather than smaller communities is that people have become less trusting; the choice not to vaccinate has been found to be influenced by confidence, not only in the product but also the health professional and the policy maker.[108–109] Evidence suggests public confidence in vaccinating is decreasing,[110] and that social norms and interactions with healthcare providers are highly influential on decisions to vaccinate. [111] A response by public health policy makers and practitioners may be to foster trust by increasing the availability and transparency


of information relating to the product and the process. Research suggests that 37% of US adults when questioned were not aware of the concept of herd immunity and over 75% thought that vaccination coverage was higher than it was.[112] While there is some evidence that educational interventions can improve willingness to vaccinate,[112] most traditional education tools have been found to have little impact on vaccine hesitancy,[113] including those that specifically dispel the myths linking vaccines with disability.[114] Since antivaccine lobby groups assume a disproportionate space within the discussion arena,[115] the key response may be to engage with mass media and initiate widespread vaccination-promotion campaigns; there is some evidence that such campaigns can reduce vaccine hesitancy and increase coverage rates.[116] Perhaps fighting the fire of powerful antivaccine lobbyists requires the clear and effective communication of scientific evidence via the medium of social and digital mass media. One further much discussed public health response could be to make vaccinations compulsory; proposals are currently in place in various countries in the developing world in light of recent outbreaks.[117] Aside from the potential implications for civil liberties and the difficulty in implementation, it has also been suggested that mandating vaccines would not address the causal problems of vaccine hesitancy[118] and may increase the inherent mistrust of the political health system.[115] Accounting for the available evidence, there have been sensible and well-considered recommendations of best practice to improve vaccination coverage in an age of inherent mistrust and hesitancy. Calls to utilise immunisation frameworks, apply multi-component interventions, link interventions to empirical evidence, and take account of the personand environment-specific factors[36] are valid and helpful. However, mindfulness of the maladaptive strategies that have propagated in recent years and the evolutionary



decision-making mechanisms that appear to be misfiring may be crucial in reminding parents that, in this case, the adaptive choice is the healthy choice. A successful campaign may enable free riding to become a successful strategy once again, as long as cheats are low in number and quiet of voice, in order that they alone incur the risks.

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7 Animal Ethics and Evolutionary Psychology Diana Santos Fleischman

INTRODUCTION Evolutionary psychology examines the human mind through the lens of evolution to understand the functions of our psychological adaptations such as motivations, emotions, and cognitions. Humans have many interactions with nonhuman animals (hereafter just ‘animals’, although the term ‘nonhuman animals’ makes an important philosophical point), most of which are fairly recent (e.g., cats as companion animals), but some go much further back in our history (e.g., hunting animals for food). We use animal bodies for fur, meat, lactation, eggs, labor, and scientific study; the scale of animal use is enormous, trillions of animals are killed for food each year (Wiblin and Bollard, 2017). In the last few hundred years, the average level of human suffering has decreased dramatically, but the total amount of animal suffering due to human actions has skyrocketed. All around us we can see examples of individuals being

exceedingly altruistic to favored animals, but also industrialized cruelty towards less favored animals at an incomprehensible scale. While we should have no expectation that human morality will be rational or consistent, this chapter grapples with the fact that our treatment of animals deviates very far from any coherent, rational morality. In terms of overall ‘suffering footprint’, human maltreatment of animals may be the biggest ethical issue in the world, and evolutionary psychology can give us deep insights into both the problem and possible solutions.

ANIMAL ETHICS Animal ethics has different meanings among groups of philosophers, scientists, and the public. Examining how our evolutionary psychology obscures consistent ethics requires some consideration of what would


serve as an ethical baseline for comparison (Fleischman, 2018). Views about human obligations to animals, or lack thereof, have proliferated in philosophy. Some philosophers argue it’s wrong to own animals or use them in any way (Francione, 2015), whereas others argue that we have no obligation to animals because they cannot make social contracts and are thus not part of our moral community (Machan, 2004). Of all the mainstream philosophical approaches to animal ethics, utilitarianism and consequentialism have been most positively disposed to morally consider animals than other frameworks (Beauchamp and Frey, 2011). Utilitarianism defines what is good as what maximizes happiness or pleasure and minimizes suffering, across all sentient beings (those capable of experiencing happiness or suffering) (Greene, 2013). This chapter rests on the basic evolutionary insight that vertebrate animals like mammals and fish evolved the capacity to feel pain and pleasure, and thus the capacity to suffer. Further, it rests on a normative moral stance that sentience should be the basis for moral consideration, that suffering is bad, and that reducing suffering is good. I do not rely on any concept of ‘animal rights’, nor do I assume that using animals as a means to human ends is always immoral (Regan, 2004), although I believe the moral foundations of these ideas are also rooted in evolutionary psychology. For my normative moral claim that suffering is bad and alleviating suffering is good, most philosophers appeal to the reader’s personal experience with suffering, or take the idea that suffering is bad as obvious (‘a priori’ or ‘axiomatic’) (but see also Kahane, 2009). Evolutionary theory has influenced many to adopt an ethical stance that we should ascribe moral standing and consideration on the basis of the ability to suffer (Singer, 2011), otherwise known as ‘sentientism’ (Ryder, 1991; ‘Sentientism’, 2019). This chapter analyzes where our evolutionary psychology is consistent with and deviates from sentientism as a moral baseline.


EVIDENCE FOR ANIMAL SENTIENCE How can we establish which animals are sentient, and therefore deserving of moral consideration? Sentience is the ability to experience pain and pleasure subjectively. First let’s distinguish between the ability to react to tissue damage, and the ability to suffer. Nociception, or the experience of pain, is the simple and ancient capacity of most animals to respond to injuries that cause tissue damage. Nociception is specific to animals with a nervous system, but even simpler organisms may have a similar capacity to respond to harmful stimuli (Tomasik, 2018a). Behavioral evidence of nociception is, for example, a shrimp grooming an injured antenna (Elwood, 2011) or, physiologically, the measurement of neurons firing in response to sensory stimulation (Braithwaite, 2010). Sentience and the ability to suffer is the subjective awareness of pleasure and pain and can be demonstrated when the response to stimuli is more complex than a simple response to physical damage (Braithwaite, 2010; Elwood, 2011). Considering an evolutionary and functional perspective, we can infer that subjective awareness of suffering evolved to prevent and manage bodily damage. If we take as given that humans can suffer, and suffering has important adaptive functions in enabling our survival and reproduction, it’s parsimonious to assume that sentience and suffering evolved in other related animals, including many other vertebrates (Tomasik, 2017). There is a solid foundation of evidence that vertebrates and even some invertebrates evolved both nociception and sentience (Braithwaite, 2010). Vertebrates as a group generally have the same neurons, synapses, and other neural hardware associated with the ability to feel pain found in sentient humans. Fish brains, once thought to lack the fundamental hardware of sentience, have been found to have a brain region similar to the limbic system such that they may have the ability to ‘process information with an emotional component’ (Braithwaite, 2010: 102).



Animal responses to pain, such as soliciting help, and avoiding stimuli previously associated with pain, are behavioral evidence of sentience. Many studies have shown that invertebrates – widely thought to be incapable of sentience – show responses consistent with subjective awareness of pain. For example, hermit crabs have been shown to make adaptive tradeoffs when exposed to shock, choosing to endure more painful shock in a high-quality as opposed to a low-quality shell (Appel and Elwood, 2009). Trout given a painful injection in their lips failed to show the normal neophobic response to a novel stimulus (a colorful block tower), compared to trout in the control condition; the trout’s distraction from normal behavior because of pain suggests a subjective awareness of pain, and thus suffering and sentience (Braithwaite, 2010; Sneddon et al., 2003). Using crabs and fish as examples is instructive, because they show better objective evidence for suffering than human neonates do (Braithwaite, 2010: 153) – but babies would almost certainly be more likely to get the benefit of our doubt. This is not to say that fish are equally sentient with cats, dogs, babies, or adult humans. There are many potentially good reasons to prioritize some animals over others by virtue of their greater ability to suffer, but the influence of, for example, brain size on degree of potential suffering is beyond the scope of this chapter (see Tomasik, 2019). The vast amount of sentience that evolved across millions of species in our world – and the resulting potential for suffering across trillions of animals – can feel overwhelming. But that doesn’t mean it is not true – and evolutionary psychologists have been courageous in confronting other emotionally challenging, counter-intuitive truths. Evolution may have created endless forms most beautiful, but it would never have passed an ethics review board (Bostrom, 2016: 188). Evolutionary psychologists should take seriously the likelihood that evolution favors widespread sentience across species, but not widespread altruism to other species, and this

sets the stage for a planet filled with s­ entient suffering both before and after humans achieved the technological means to exploit other species on an industrial scale.

Natural-Born Speciesists There are two central questions with regards to human morality towards animals: why do we value animals less than humans morally, and why are our moral attitudes towards animals so inconsistent? Both moral anthropocentrism and speciesism describe the concept of valuing human lives over animal lives, although speciesism implies that this valuation is a form of prejudice due to mere species membership (Caviola, 2019). Most people value members of certain species above and beyond their ability to suffer, for example valuing insensate humans (like those in a persistent vegetative state) more than chimpanzees, and valuing dogs more than pigs, even though they are similarly sentient. Valuing humans over animals seems to be a human moral universal. In one study, millions of participants all over the world overwhelmingly choose to save the life of a human over an animal, or several animals (Awad et  al., 2018). In another study, participants most often choose to save one human over the lives of several endangered animals (like gorillas) (Petrinovich et  al., 1993). This valuation is often reversed if the animal at risk is their pet. When Topolski et  al. (2013) asked participants who they would save if a bus was imminently going to hit their pet or a foreign tourist, 40% chose to save their pet. ‘The only consistency in the way humans think about animals is inconsistency’ (H.Herzog, 2010: 14). Arguably, it can be rational to prioritize some interests over others on the basis of sentience, but, unsurprisingly, humans are not doing any coherent form of ethical calculus when they choose actions or decide on the morality of those actions. Is there an inherent human moral response towards animals? The study of how humans


and animals interact has taken off in the last two decades with the rise of anthrozoology, also known as human–animal relations (Amiot and Bastian, 2015; H. Herzog, 2010; Serpell, 1996). Anthrozoology is a diverse field, investigating topics like the therapeutic properties of living with dogs, the possible link between animal abuse and criminal behavior, and the personality traits of animalrights activists (H. Herzog, 2010). These fields have often tried to explain human moral anthropocentrism and moral inconsistency with descriptive frameworks like carnism (the social ideology that supports meat eating) (Joy, 2011), moral disengagement (i.e., we distance ourselves from our humane standards to harm animals) (Bandura, 1999; Vollum et  al., 2004), terror management theory (i.e., we cling to human uniqueness and animal oppression to avoid existential anxiety) (Marino, 2019), and speciesism (discrimination based on species membership) (Caviola et  al., 2018; Singer, 1995). Explanations at a functional level of analysis (Scott-Phillips et  al., 2011) and adaptationist accounts are less common in anthrozoology (although see Bradshaw and Paul, 2010; H. Herzog, 2002). Evolutionary psychology is compatible with most of the explanations of human morality towards animals advanced by anthrozoologists. It posits functional explanations for attitudes and behaviors as reflecting evolved psychological adaptations (or their byproducts). Explanations like speciesism and cultural explanations like carnism are not in conflict with evolutionary psychology (Tooby and Cosmides, 1989), because culture is both an outgrowth of and a support for our evolved morality (e.g., the cultural celebration of consensual courtship and maternal love). However, the assumption of some thinkers in anthrozoology, as well as many animal-welfare advocates, is that humans are naturally sensitive and morally concerned about animal suffering, but this innate goodness is numbed by cultural and social factors like carnism (Joy, 2003)


and moral disengagement. The consistent thread in these perspectives is that violence is deeply unnatural. However, from the perspective of evolutionary morality, we should not expect sensitivity to animal suffering or kindness to animals except to the extent that it helped us, for example when using animals for our benefit, or to signal our morality.

Anthropomorphism Anthropomorphism, or ascribing human characteristics to animals, is an apparently universal feature of the human mind (Urquiza-Haas and Kotrschal, 2015). Anthropomorphism is so naturally expressed that it’s difficult to think about animals in non-anthropomorphic, objective terms. Most children don’t make clear distinctions between humans and animals, and young children usually treat animals, like family pets, as human persons (Serpell, 1996). Ironically, the basis for much of our moral feelings towards animals likely evolved so we could better exploit, kill, and eat them. Humans and animals aren’t so different, so the same theory of mind and empathy that helps us predict what humans do can also be used when hunting prey animals or avoiding predators. Primatologists and other animalbehavior scientists often use simple anthropomorphism to make predictions; behaviorist John Garcia stated that anthropomorphism with regard to rat behavior ‘works better than most learning theories’ (Serpell, 1996: 174). When you’re using the mind-reading ability that mostly evolved to predict the behavior of other people, you’re bound to ascribe human characteristics to animals. The ability to imagine what it was like to be an animal has adaptive benefit to better predict the behavior of prey, predators, and dangerous animals (H. Herzog, 2002). Some speculate that empathy could have motivated nurturance for domesticated species in animal husbandry (Bradshaw and Paul, 2010) however these animals have also been bred to be cute and inspire



feelings of care. Given an adaptationist perspective, empathy would have been bounded so as not to interfere with the processes of killing, butchering, and eating animals. If empathy is like a spotlight that illuminates the suffering of some at the expense of others (Bloom, 2016), this spotlight turns off or moves on. Empathy isn’t consistently associated with caring about animal ethics (Kasperbauer, 2015). And biophilia, or the desire to affiliate with nature and animals (Wilson, 1984), often doesn’t have a loving or caring character.

Play and Animal Abuse One clue about evolved human morality towards animals is how readily humans will torment animals when it isn’t necessary, and how much they enjoy doing it. Play is an essential part of learning in our species and many others. But humans playing with animals often involves both curiosity and cruelty (Arluke, 2002). Around the world, in both traditional societies and Western societies, playing with animals and cruelty to animals are commonplace in both adults and children – not just in psychopaths. Read some anthropological descriptions of hunter-gatherers and you’ll see sentimental, Noble Savage views like this: ‘Children learn to sympathize with animals and to see animals as sentient persons sharing the forest world with them’ (Lew-Levy et al., 2017: X). The implication is that hunter-gatherers have greater moral regard for animals than Western people, who only see meat wrapped in cellophane at the grocery store. However, read descriptions from thinkers who are less attached to a Noble Savage narrative, and you’ll get a better picture of how difficult it may be for our species to bestow moral consideration on others. It’s common for people in more traditional societies to hurt animals for fun. Jared Diamond describes Papua New Guinean men amusing themselves by raising and lowering

squealing bats into a fire and dissecting them alive for their bones (Diamond, 1993). Men and boys are much more likely to abuse animals than women and girls (Arluke, 2002) but this passage about Nisa, a !Kung San woman, describes with unusual clarity the dynamic of curious, playful cruelty, and its ability to facilitate precise prediction of animals: A flying ant with a long, wormlike body and large, almost transparent wings… landed in the hot sand… Nisa saved it… and pierced it through half the length of its body with a thin twig, leaving the upper half with the wings and head free. She planted the stick, with the skewered insect at the top, upright in the ground and tapped it gently with her fingers. The insect’s wings burst into motion, as if in flight, propelling the free parts of its body around and around the stick; then it stopped. Nisa tapped the stick again and again; each time, the insect responded with the same outpouring of energy… What Nisa was doing… seemed like an inexcusable torture… [But Nisa’s] head and the upper parts of her body had begun to move rhythmically. I did not understand what she was doing at first. Then it became clear: as the insect held itself erect, Nisa’s body also became erect; when the insect circled, drooped, and strained, Nisa’s body did the same. Her face and torso echoed the insect’s plight with a wrenching subtlety and her mimicry of its every movement was so sympathetic that the situation took on a kind of beauty. (Shostak and Nisa, 2004: 321)

Using animals for entertainment has been one of the most contentious and moralized aspects of animal use, even though the scale of suffering involved is much smaller than most modern industrialized forms of animal use. For example, many countries that otherwise have few animal-protection laws have banned circuses (‘These 27 Countries Have Banned WildAnimal Circuses!’, 2019, uk/blog/these-26-countries-that-have-bannedwild-animal-circuses-are-making-englandlook-really-bad/). Bear-baiting, hare-coursing, dogfighting, and cockfighting are more controversial than other types of animal use, and were banned much earlier (e.g., the UK banned bearbaiting in 1835 and Pakistan banned bear-baiting in 1890). This seems to be an area of strong moral signaling.


One reason modern people might be judgmental about animal entertainment is because of the glut of other entertainment media developed in the last few centuries. Yes, using animals for entertainment is unnecessary, but it seems even less necessary and thus indulgently cruel when so many other forms of entertainment are available, especially other forms of violent entertainment like combat sports, action films and video games. Forms of animal entertainment considered lowbrow or ‘primitive’ may be more controversial. For example, many have argued that forms of animal entertainment enjoyed by the working class, like cockfighting, have been banned more quickly and more often than those enjoyed by the higher classes, like fox hunting (‘Fox Hunting’, 2019). Most of us in Western societies who would not want to torment an animal directly, or would be appalled to see staged animal suffering intended for entertainment, are still entertained by watching animals inflict suffering on each other in the wild, for example, in nature documentaries. The disparity in sensibilities is also well illustrated in this anecdote: That is perhaps the hardest part of being an anthropologist. [The hunter-gatherers I was studying] sensed my weakness and would sell me all kinds of baby animals with descriptions of what they would do to them otherwise. I used to take them far into the desert and release them, they would track them, and bring them back to me for sale again! (Pinker, 2011: 473)

These behaviors that cause suffering to animals are often practiced alongside making offerings to animal deities, praying to the spirit of animals after killing them, and efforts to embody animal qualities – contrary to the notion that cruelty requires dehumanization or suspension of empathy. In many smallscale societies, formalized animal totemism often co-exists with informal animal torment. The majority of human groups include some conspicuous cruelty to animals, but there are exceptions. For example, Jain monks and nuns sweep the ground in front of them so as to avoid inflicting any suffering on insects


(‘Ahimsa in Jainism’, 2019). Here it’s notable that this requires strong spiritual and social incentives, such as the belief that any given human might be reincarnated as an insect. Given our evolutionary history as omnivores, and the ubiquity of animal abuse across cultures, it seems likely that carnism and speciesism are outgrowths of our evolved psychology, rather than historically novel cultural influences that render us weirdly insensitive to animal suffering.

Animal Abuse by Children – The Link Children commonly inflict suffering on animals, not just out of necessity, but for enjoyment and curiosity. Here again, we see the sentimental narrative that animal abuse is a rare, pathological glitch in children’s fundamentally caring natures, and that children who abuse animals will grow up to have other serious problems like psychopathy and criminality. Animal abuse is considered a risk factor for violence with such certainty in the animal advocacy community that it’s sometimes referred to simply as ‘The Link’ (H. Herzog, 2010). Most of the evidence for an association between childhood animal abuse and adult violence suffers from methodological limitations like retrospective reporting, and sampling incarcerated criminals (Flynn, 2011). But, consistent with the idea that insensitivity to animal suffering is fairly standard in our species, there isn’t replicable evidence that animal abusers are more likely to commit violent crime (H. Herzog and Arluke, 2006; Patterson-Kane and Piper, 2009). Consistent with the cross-cultural ubiquity of animal cruelty, and the historical commonality of using animals for entertainment, animal abuse is normal among young people, even now. In one study, 40% of female college students and 66% of male college students admitted to having abused animals (Arluke, 2002) – and given the modern stigma against animal abuse, this is probably



an underreported behavior. There seems to be a moral panic about animal abuse; advocates often depict anyone who has ever abused an animal as likely to commit violence against people, even though the majority of people have, at some time, abused an animal (Patterson-Kane and Piper, 2009). Children might be learning about how animals ‘work’ by playing with them, developing mental models of animal morphology and behavior that ancestrally would have been useful for hunting, tracking, and butchering. Indeed, vertebrate animals’ similarity to humans means that children may be learning more than this. Children around the world often practice caretaking with pets and baby animals. I speculate that violence, which is often used to adaptively compel others to do what you want, can be practiced and honed similarly by playing with animals or through cruelty. Indeed, lacking the kinds of modern toys that Western children have access to, animals are used in just this way, treated with both care and cruelty. ‘Anthropologists have observed returning hunters bringing small wild animals back alive and promptly turning them over to their children… these animated toys are generally badly treated, short lived and… end up the objects of target practice or mutilation’ (Serpell, 1996: 68). There are two main hypotheses about the animal-­ cruelty association with crime: the graduation hypothesis posits that animal abuse is ‘a form of rehearsal for human-directed violence’, and the deviance generalization hypothesis posits that antisocial personality is associated with both animal cruelty and criminal behavior (Gullone, 2014). Animal cruelty might be both a normal behavior that children perform if unsupervised with animals, and also a form of practice that is disproportionately attractive to children with antisocial and violent tendencies. Animal killing and butchering were surely features of our evolutionary history, but modern specialization of labor means for the first time there are workers who spend hour after

hour killing and butchering animals. Even among slaughterhouse workers, the worker who kills the cow, the ‘knocker’, is considered to have psychological problems compared to other workers who bleed the cow or begin to dismember it (Pachirat, 2014). There is evidence that the presence of slaughterhouses is associated with increased local rates of violent crime and sexual offences, relative to other industries like steel forging (Fitzgerald et  al., 2009), but it’s unclear if violent people are more attracted to working in slaughterhouses, or if slaughtering animals increases workers’ propensities for violence towards other humans.

WHY HAS ANIMAL ADVOCACY LAGGED BEHIND OTHER MORAL MOVEMENTS? Civil-rights movements, like those for the abolition of slavery, black power, women’s rights, worker’s rights, and gay rights, have flourished in the last several decades, and have reduced suffering for billions of humans (Pinker, 2011). The animal advocacy movement (including animal rights, animal welfare, and animal liberation – but not environmental protection) has not had the same success as other sentient-rights movements (Pinker, 2011). In some ways, attitudes have changed a great deal. In a representative sample of over 1,000 American adults, Sentience Institute found that nearly 50% supported a ban on slaughterhouses and factory farming (Reese, 2017). But, in that same survey, 75% of participants believed the reassuring fiction that the animal products they were eating had been humanely produced (Reese, 2017) even though 99% of animal products come from factory farms (Reese, 2019). A recent Gallup poll found that 32% of Americans think that animals deserve ‘the exact same rights as people’ (Riffkin, 2015), up from 25% in 2003 (Moore, 2003). A study of 3,500 Ohio residents found 81% said farm


animal welfare was as important as pet ­welfare, and 75% said farm animals should be protected from physical pain (Rauch and Sharp, 2005). These self-reported attitudes are impressively progressive, but consumer behavior has not changed that much. FewAmericans boycott animal products. The rate of selfidentified vegetarians has hovered around 5% in the United States for several years (Riffkin, 2015). Other reports claim there are slightly more vegetarians. The number of people who describe themselves as vegetarian is probably not actually representative of boycott, because only about one-third abstain from meat (Cooney, 2014). Che Green, an expert on these trends, has called vegans and vegetarians ‘a blip on the demographic radar’ and ‘below the margin of error for most surveys’ (Zaraska, 2016: 136). The concern for animal wellbeing has made uneven progress, with far more concern about some species and some issues than others. One illustration of the vast disparity between the alleged human moral concern for animal suffering, and the actual concentration of animal suffering, is revealed by patterns of charitable donations (Figure 7.1). Farm animals, compared to all other animals,


experience the vast majority of suffering and death with more than 99% of farm animals living on factory farms (Reese, 2019). Farm animals received only $20 million in charitable donations in 2015, compared to $1.2 billion donated to animal shelters for pet species like dogs and cats (Bockman, 2016). Of domesticated land animals used and killed by humans in the United States, over 99.6% are farmed land animals, about 0.2% are animals used in laboratories, 0.07% are used for clothing, and 0.03% are killed in companion animal shelters. However, about 66% of donations to animal charities in the United States go to companion animal shelters, 32% go to groups with mixed or other activities, and just 0.8% of donations go specifically to farmed animal organizations, while 0.7% go to laboratory animal organizations. (Bockman, 2016)

A couple of caveats are that the ‘other’ category does include some farm animal donations, because it includes large organizations that engage in diverse animal advocacy campaigns (e.g., People for the Ethical Treatment of Animals (PETA)). ‘Other’ also includes environmental charities and wildlife preservation. Also, importantly, the ‘animals used and killed’ number does not include fish, which would completely dominate the left panel.

Figure 7.1  Charitable donations towards animal organizations as compared to animal use



Fish are probably killed in the trillions, at a rate greater than all other animals combined (Mood and Brooke, 2010). This is another way that human behavior is inconguous with stated concern. If humans cared about reducing animal suffering and acted in keeping with this concern, they would not give a disproportionate amount of their donations to cat and dog shelters. Below I will address the psychology of how and why humans morally value and devalue animals. First, I’ll discuss kin selection, and the empathy elicited by cuteness and neoteny – two intertwined factors that account for our kindness towards companion animals like dogs and cats. Second, I’ll discuss disgust and food aversion, meat consumption, and the future of meat eating. Empathy, disgust, and food preferences show significant sex differences, and I’ll discuss how they manifest in morality. Lastly, I’ll talk about how morality is socially signaled, and how this virtue signaling plays out in animal care and attitudes towards the animal-focused moral minority, such as vegans. The view of decision-making in the moral domain in this chapter is consistent with the popular metaphor of the elephant and the rider (Haidt, 2012; Simler and Hanson, 2017). Emotions and psychological mechanisms like the cuteness response, disgust, reputation management, and empathy guide our moral decisions in often irrational directions, like an elephant deciding which path to take. We identify as the rider, the part we are most conscious of, and we later attribute our moral decisions to rational processes rather than the ‘hot’ emotional cognition of the elephant, the part that controls our behavior.

Kin Selection and the Cuteness Response Prominent anthrozoologist James Serpell defines pets as ‘animals we live with, with no obvious function’ (H. Herzog, 2010: 72). Other animals don’t usually keep pets. Crossspecies friendships sometimes happen (see

viral videos of cats who love rats and hippos who love tortoises, for example), but they are almost always the product of an artificial environment (H. Herzog, 2014). Pet-keeping seems uniquely human. Two interesting exceptions in the wild are a dolphin who adopted a melon-headed whale (Carzon et al., 2019), and a marmoset adopted into a group of capuchin monkeys (Izar et al., 2006). In the first case, the dolphin nursed and cared for the whale, and in the second case, two female capuchins provisioned the marmoset. In both cases, arguably, the adopted animal appears to be a neotenous version of the animals’ own young. This illustrates a major psychological means through which humans integrate animals more centrally into their moral worlds: kin selection and empathy for cuteness. Both cases also illustrate how this cuteness-based empathy is more motivating for females than for males. Humans keep a wide variety of pets, from insects to horses, but here I’ll focus mostly on dogs, who seem to be the animals who most often reverse human speciesism. The psychological mechanisms motivating kin selection may cause humans to value dogs and cats much more than other comparably sentient animals. Evolution promotes passing on our genes, including in other members of our families (Foster et al., 2006). Because cooperating in groups is adaptive, we may be more likely to interpret ambiguous cues as evidence of genetic association (Park and Ackerman, 2011). In this way, kin selection means that we tend to be more altruistic to those who show cues of being members of our ingroup – whether these cues are cultural (Kurzban et  al., 2001) or physical (Krupp et al., 2011). There are other possible indicators of genetic relatedness, like psychological similarity (Park and Schaller, 2005), and time spent growing up together (Lieberman et al., 2007). It’s unclear if our minds are simply indiscriminate about what cues we take as indicators of genetic relatedness. Some animals indisputably occupy a familial role, not only in Western countries but also among many



hunter-gatherers. New Guineans, which I earlier described abusing bats, treat pigs as members of their families; piglets sleep in the same hut with their human families and New Guinean women often nurse piglets at the breast (Diamond, 1993). In the United States, 91% of dog and cat owners reported that their pet was a part of their family, and 20% of dog owners report giving their dogs birthday gifts (‘Pets Really Are Members of the Family’, 2011). We attend to physical similarity when evaluating species and breeds for special treatment. For example, people are more likely to support causes to save endangered species that have more in common with humans, like great apes, and researchers who do invasive scientific experiments on monkeys are most likely to be threatened by animal activists (H. Herzog, 2010). Even so, most people (around 75%) would choose to save one person over five endangered lowland gorillas (Petrinovich et al., 1993). Dogs show resemblance to humans in their facial musculature: domestication has changed dog faces compared to wolf faces to be able to display more humanlike expressions (Kaminski et  al., 2019). There is also evidence that people resemble their dogs (Nakajima et  al., 2009), and that people choose dogs who resemble them (Roy and Nicholas, 2004). People also tend to think their dogs are psychologically similar to them. Dog breeds go in and out of fashion (Ghirlanda et al., 2013), but the proliferation of so many dog breeds with different appearances and personalities may have been driven by the kin-selection mechanisms of different individuals and ethnic groups with different implicit criteria for similarity.

(genetic similarity) and cuteness are difficult to disentangle as contributors to this unusual moral relationship. Because there is no word in English for the especially cute emotional repertoire elicited by cuteness, I’ll use ‘cuteness response’. The cuteness response elicits nurturance but also inspires mentalizing and anthropomorphizing, bringing cute individuals closer into the circle of moral concern (Sherman and Haidt, 2011). There is evidence that pets, especially dogs, parasitize our parental caretaking mechanisms (Turner, 2001). People talk to dogs in a way similar to ‘motherese’ (the sing-song way in which parents talk to their infants), and motherese for dogs has been termed ‘doggerel’ (HirshPasek and Treiman, 1982). Dogs are also neotenous: they retain puppylike features throughout their lives. Furthermore, dogs who have more paedomorphic (i.e., cute) facial musculature are more likely to be adopted from shelters (Waller et  al., 2013). Dogs in childless homes are much more likely to be groomed, given presents, and taken on vacation (H. Herzog, 2010: 79). Dogs have been bred to retain neotenous puppylike features and to be cuter than their wolfy ancestors. Dogs aren’t just cuter to us; they’re also cuter to wolves themselves! In one study a wolf mother was given two different litters to foster, one with wolf puppies and one with dog puppies:

Cute Ethics

One reason that dog breed popularity doesn’t track health, obedience, or other desirable qualities is the desire for the cuteness superstimulus. Analyzing the popularity of dog breeds in the United States from 1926 to 1995, researchers concluded that there was

In ethics, cuteness doesn’t count. (Cohen, 2009)

Because pets seem to occupy a place in the family as surrogate children, cues of kinship

The foster-mother wolf was… more nurturant with the Malamute pups than with the wolf pups. She washed them earlier and more frequently, spent 2–3 times as many hours in the den-box with them as she did with the wolf pups, was more defensive toward intruders, showed far more distress when one was missing (e.g., during supplemental feedings), played with them and continues to play with them for longer periods of time. (Frank and Frank, 1982: 515)



no indication ‘that breeds with more desirable behavior, longer life, or fewer inherited genetic disorders have been more popular than other breeds’ (Ghirlanda et al., 2013: 4). Most purebred dog breeds have some endemic health problems, but brachycephalic dogs (dogs with short snouts, like bulldogs) have many more problems. This preference for this brachycephalic cuteness super-stimulus, (for example these dogs have a much rounder more infant like head than most other dog breeds) causes a huge amount of suffering for animals that are otherwise treated like family. French and English bulldogs must usually be delivered by C-section, and suffer many other problems like allergies, hip dysplasia, persistent farting, and heat sensitivity that causes them to die more often in transport (K. Herzog, 2019). Interestingly, people with these neotenous breeds are more attached to their pets than those with less neotenous breeds. In a Danish sample, French bulldog owners were more attached to their dogs and nearly 20% more likely to say ‘I would do anything for my dog’ compared to owners of the much less neotenous Cairn Terriers (Sandøe et  al., 2017). Perhaps they just reported this because their dogs required extraordinary attention and care or perhaps these health problems – are one reason people want these dogs (Serpell, 2019). Bulldogs have been in the top five for breed popularity for the last six years, and in the last two years, French bulldogs have also been in the top five. With the recent high-profile win of ‘Thor’, a bulldog, at a national dog pageant, this trend is likely to continue (K. Herzog, 2019). To some extent, our special affinity for our pet dogs translates into special moral consideration for all dogs. In the United States there was widespread outrage prompted by China’s annual dog-meat festival (Howard, 2016). The United States has loved dogs for a long time – and, in perhaps the greatest success story from the animal-protection movement, the number of dogs (and cats) that are euthanized per year has plummeted, down 75% from 2011 (Parlapiano, 2019).

Why do we as humans find a huge array of animals cute, from penguins to pandas to pangolins? Prototypical cuteness elicitors are cues like round and fat cheeks, large eyes, small teeth, and playful energetic behavior. Our own young don’t achieve peak cuteness until they are several months old (Sherman and Haidt, 2011). Humans produce very altricial young and neonates are highly divergent in their appearance (e.g., presence of hair, redness of skin, facial morphology). Also, neonates often aren’t cute, and yet this stage of life is when our young are most vulnerable and most in need of care. In order to take care of our own neonates, the normal primate standards of cuteness may have become relaxed in humans. Earlier I speculated that slightly indiscriminate kin-detection mechanisms could have made it easier for humans to form friendships. Something similar could have happened with cuteness and pets. The large number of animal species we think are cute could be because of indiscriminate cuteness perception. ‘Cuteness promiscuity’ might be a byproduct of our unusual life history, high altriciality, and high variance in infant appearance. This tendency to think that many different animals are cute could be even more pronounced in women, who are the primary caretakers of altricial infants. Given selection over time for dogs to elicit both fellow-feeling (kin selection) and the cuteness response, it makes sense that their suffering is much more prioritized than that of other species. Given women’s special sensitivity to cuteness, it makes sense that we find such a large difference in men and women when it comes to animal morality.

SEX DIFFERENCES IN MORALITY TOWARDS ANIMALS In the example above in which a dolphin fostered a melon-headed whale, she also nursed him. Cross-species nursing is also common cross-culturally. Women around the


world have nursed baby animals like bears, monkeys, pigs, and puppies (H. Herzog, 2019). In some of these cultures, eating an animal nursed at the breast is considered as taboo as eating your own child. In other cultures, animals like dogs, are traded with other groups in order to limit the discomfort of killing animals one raised, and in other cultures, animals are nursed so that they can be later eaten (Serpell, 1996). Among the Ainu of Japan, bear cubs are breast fed and then ceremonially sacrificed and eaten, while the women who suckled the bear cubs show their ambivalence by alternately crying and laughing (Serpell, 1996: 184). Unsurprisingly, given women’s sensitivity to cuteness and their greater nurturing response (on average), women show stronger moral concerns for animals than men do. For example, 45% of women would let a foreign tourist die before their cat or dog, compared to 30% of men (Topolski et  al., 2013), and 33% of women would kill a person to save 1,000 dogs, compared with 23% of men (Petrinovich et al., 1993). However, men and women were similarly likely to say they would save a close relative over a pet (Topolski et al., 2013). There are many other sex differences in moral attitudes towards animals, reflecting differences in moral emotions such as disgust, empathy, and the cuteness response. Women are much more likely to be involved in animal protection and animal advocacy, much more likely to be vegetarian, more likely to hoard animals, and much less likely to hunt or engage in direct animal abuse ( H. Herzog, 2007). Women are less speciesist than men as measured through questionnaire (Caviola et al., 2018). Women are more likely than men to believe that animals experience complex emotions like grief and anxiety (Walker et al., 2014). There are also substantial sex differences in moral views on animals. In a 2015 poll, 42% of women compared to 22% of men said that animals deserve the same rights as people (Riffkin, 2015). In a 2011 Gallup poll on moral issues, the largest sex differences were on issues related to animals: ‘Majorities


of men, but less than half of women, consider the use of animal fur for clothing, and medical testing on animals to be morally acceptable’ (Saad, 2010). Women are also much more opposed to ‘unnatural’ technologies, including food additives, genetically modified foods, and animal testing (Funk et al., 2015). In particular, 62% of women oppose the use of animals in scientific research, whereas 60% of men support it.

Animal Testing: Disgust and Empathy The widespread opposition to animal testing is a good demonstration of how disgust and empathy can create strong feelings around animal ethics, even when they conflict with important human interests such as biomedical advances. All drugs and interventions to prevent human and animal suffering must first be tested. Gary Francione (2009), who famously advocates completely abolishing the use and ownership of animals, has called animal testing the only use of animals that isn’t frivolous. Animal testing is one of the highest-profile and most controversial uses of animals, although it accounts for a very small proportion of animal suffering. ‘We kill 200 food animals for every animal used in a scientific experiment’ (H. Herzog, 2010: 176). More than half (52%) of Americans oppose the use of animals in scientific testing (Strauss, 2018), and 60% oppose animal cloning (Masci, 2017) – a technology that could lead to significant advances in biomedical research and comparable gains in human welfare. In comparison to other ­animal-related causes, there have been much larger changes in legislation and regulation around animal testing. For instance, the EU has implemented bans on cosmetic animal testing (‘Testing Cosmetics on Animals’, 2019) (arguably, this was only possible because most cosmetic ingredients have already been tested on animals for decades and found safe).



In 2015, 0.2% of animals were killed in labs but a disproportionate 0.7% of charity money went to this cause (Bockman, 2016). Some of the only true terrorism by animal advocates – like death threats and property damage – has targeted scientists and laboratories conducting animal research. In particular, scientists who work with primates or dogs have been targeted (H. Herzog, 2010). Familiarity is one heuristic we use to infer that something isn’t dangerous or pathogenic. Unlike meat eating, animal experimentation’s visceral associations and unfamiliarity combine to create an impression of ‘unnaturalness’ (Holden and H. Herzog, 2019) that is disgusting and elicits moral condemnation.

Meat Meat is a strongly preferred food among humans. This enjoyment of and desire for meat is a major contributor to our moral attitudes about meat, and to our self-deception about the living conditions of animals raised for meat. Humans almost certainly evolved eating meat (Wrangham, 2009), and seem motivated to eat meat specifically. For instance, human taste buds appear to be sensitive to a flavor abundant in cooked meat called umami (Lindemann et  al., 2002). In many places in the world there is a special word for ‘meat hunger’ (Fiddes, 2004; Zaraska, 2016), as distinct from other kinds of hunger. In recent years the developing world, either imitating rich industrialized nations or actualizing their evolved taste preferences for savory, high-calorie foods, are eating more meat and other animal products (Kearney, 2010). Meat eating has increased a great deal in the United States in the last few decades, and Americans now are eating an average of 125 kg of meat per year (Zaraska, 2016). And in China, the most populous country in the world, the average person in the 1970s ate 14 kg of meat per year, whereas in 2010 they were eating 55 kg of meat per year (H. Herzog, 2010). Around

the world the trend is that people are eating more meat, year after year. However, the strong human desire for meat has a flip side, because meat has often been a dangerous food to eat, more likely to contain pathogens than plant foods. Because humans eat both plants and animals, they face an omnivore’s dilemma: there are a large number of foods that could be eaten, but they differ both in nutritional quality and in the risk of dangerous pathogens. Disgust is thought to have evolved to reduce the chance of coming into contact with potential pathogens, especially those that are orally incorporated (Tybur et  al., 2012). That’s likely why culture discourages eating certain animal foods. Taboos are more often leveraged against meat than against other foods (Fessler and Navarrete, 2003). The trait of ‘disgust sensitivity’ is positively linked to meat avoidance (Fessler et  al., 2003), and disgust is often given as an explicit reason for not eating meat (Santos and Booth, 1996). As I argued earlier, there is evidence that most animals used for food are sentient, and that human imposition of industrial-scale suffering on sentient animals may, from the perspective of aggregate suffering, be one of the most pressing concerns of our generation (Singer, 1990). The scale of animal use is staggering. According to an interview with expert Lewis Bollard (Wiblin and Bollard, 2017), there are currently 23 billion chickens being farmed (15 billion for meat and 8 billion for eggs), 6 billion mammals (like cows, pigs, and rabbits), and over 100 billion farmed fish. Even if we ascribe to each of these animals just a fraction of the sentience and moral importance ascribed to a human, this adds up to a massive moral issue – vastly more aggregate suffering than global poverty or disease among humans. From the perspective of sentient suffering, the environmental and sustainability issues around meat also matter. Meat is environmentally costly to produce, requiring more water and land per calorie, in addition to being one of the major producers of greenhouse gases and


water pollution (Steinfeld et al., 2006). Meat feeds fewer people with the same resources. Estimates of inefficiency vary, but the same amount of grain produces 10 times fewer calories through grain-fed cattle than when eaten directly (Bittman, 2008). (However, it’s important to consider that much of the land that isn’t suitable for farming can still feed grazing ruminants, like cattle, and thus can produce food.) In principle, boycotting animal products could significantly reduce many of these problems. But, even in places with abundant food choices, vegetarianism and veganism are rare (Pinker, 2011). Most self-described ‘vegetarians’ eat meat (Cooney, 2014), and perhaps 90% of people who self-identify as vegetarian aren’t behaviorally vegetarian (H. Herzog, 2010: 195). Moreover, lapsed vegetarians outnumber current vegetarians (H. Herzog, 2011), and many vegetarians avoid red meat for health reasons rather than ethical reasons. Thus, it’s difficult to estimate how many people are boycotting animal products for ethical reasons. All foods cause some degree of suffering – even vegetables and fruit, because many small wild animals, from insects to birds, are killed during planting and harvesting. As Norwood and Lusk (2011) glibly comment, ‘even veganism is murder’ (2011: 229). However, animal foods differ markedly in how much suffering they cause. Ironically, the most popular ways that vegetarians and semi-vegetarians reduce their consumption of animal products may impose more net suffering than a diet centered around beef would, as I discuss below. Disgust is a major driver of meat avoidance (Fessler et al., 2003). Red meat, which retains more cues of its animal origins, like blood, is considered much more disgusting than fish or chicken, which are often packaged to hide their animal origin (H. Herzog, 2010: 190). Health messages about meat underscore this disgust, with recommendations to cut out red meat and to eat chicken, eggs, and fish instead. Self-described vegetarians, who are


often motivated by both disgust and health messaging, often end up eating more chicken than self-described meat eaters do (H. Herzog, 2010: 195). Another factor beyond disgust is that we often feel more empathy for cows and pigs than for fish and chickens, because they have more humanlike and neotenous characteristics. How might consumption of fish, eggs, and chicken, to the exclusion of beef and pork, cause more animal suffering? There are two main reasons: animal size and quality of life. Chickens and farmed fish are smaller animals, which means that for each animal bred, caged, and slaughtered, we get far fewer meals. This observation was the basis of a tongue-in-cheek campaign from PETA called ‘Eat the whales’ (Tomasula, 2001). In a 100-ton blue whale, there are 70,000 chickens’ worth of meat. (H. Herzog, 2010: 193). Considering living conditions, chickens (both egg-laying hens and broiler chickens) and farmed fish have much worse lives than conventionally produced beef cattle (Tomasik, 2018b). Conventionally produced beef cattle spend much of their lives in pasture and the last 100–200 days of their lives in a feedlot – they can eat, stretch out, and associate with others of their species. By contrast, broiler chickens live in cramped conditions and often have crippling leg problems. Egg-laying hens kept in cages usually have their beaks removed so they don’t attack or cannibalize one another in cramped spaces. Often this causes chronic pain or inability to feed, and it doesn’t solve the problem of hens aggressing against their cage mates. Conventional pork production is widely considered to be terrible for smart social animals such as pigs, who are confined and bored, like a dog kept in a kennel cage for months on end. For those concerned with humane animal treatment, a reasonable goal is that animals raised for food should only have ‘one bad day’: the day they go to slaughter. For detailed descriptions of how different animals are raised for food see, for example Norwood and Lusk (2011) and Singer and Mason (2006).



Remarkably few people have tried to compare animal welfare across species or to calculate how much suffering is caused by eating different animal foods. Still, there is some consensus on which animals have the best and worst lives. Economists Bailey Norwood and Jayson Lusk (2011) came to similar conclusions as Tomasik (2018b) in terms of the quality of life of various animals raised for food (and also quantified the quality of life for animals kept for breeding purposes) (Norwood and Lusk, 2011: 229). They estimated that laying hens and veal calves have the worst quality of life, and that beef cattle and dairy cows have the best quality of life relatively speaking. (However, Norwood and Lusk argue that broiler chickens have a much better quality of life on average than most animal advocates think they do.) How does all this add up? We can quantify a ‘suffering footprint’: an estimate of how many days of suffering animals endure to contribute a unit of meat to our diet. Table 7.1 is adapted and simplified based on Tomasik’s (2018b) calculation of how many days of suffering per kg are caused by the demand from buying various animal foods. I have simplified the calculation here by assuming these animals have the same sentience, and by assuming that each animal has roughly the same suffering on the day of slaughter (the reader can input values in the table at the Reducing Suffering blog,

foods/). Here, animal lifespan is how many days the animal lives before slaughter, on average; kg of food per animal lifespan is how much edible food weight is produced by the animal; suffering per day of life is how bad the animal’s life is based on best estimates from animal-welfare researchers (note that beef cattle have the best lives and battery hens have the worst lives). The column on the right indicates for each kg of the animal product consumed how many days of suffering there are adjusted for the badness of each day of life. Using a similar calculation, the standard American with a typical diet of animal products causes 5 years, 6 months, and 5 days of animal suffering per year (Hurford, 2014). Regardless of specific numbers, many ‘vegetarians’, some adhering to the definition and eating eggs, and many others who still eat fish and chicken, are causing more days of animal suffering, and more intense suffering, than many meat eaters are. Based on the calculations from the table above, a vegetarian who eats three eggs at a meal (around 150 g) is causing 19.5 days of chicken suffering, compared to a meat eater who eats a 1.3 kg steak that causes around 2.4 days of cow suffering. The average vegetarian almost certainly causes less suffering than the five years of suffering created through the average American diet. But the perception that the average selfdescribed ‘vegetarian’ is more moral than the average meat eater is derived not from any

Table 7.1  Days of suffering per kilogram of food weight produced by the animal adjusted for the badness of each day of life as estimated by animal welfare researchers Animal product Farmed catfish Farmed salmon Battery cage eggs Chicken Turkey Pork Beef Milk

Animal lifespan (days) Kg of food per animal lifespan 820 639 501 42 133 183 395 1,825

.39 2.0 16 1.9 9.6 65 212 30,000

Suffering per day of life (beef cows =1) 1.5 1.5 4 3 3 2.5 1 2

Adjusted days of suffering caused per kg demanded 3,200 480 130 68 42 7.1 1.9 0.12


quantitative analysis of animal suffering, but from their claimed concern for animals, and from the fact that they eat less meat from mammals, who are cuter and more humanlike. Even a vegetarian who eats eggs every day would cause more suffering than someone on an all-beef diet. An actual vegan, who eats no animal products including meat, fish, eggs, and dairy, causes the least amount of suffering with their consumption. Giving up fish, eggs, and chicken would reduce animal suffering about 90% as much as a vegan who eats no animal products at all (Cooney, 2014). Unfortunately, there is no name for this avoiding fish, eggs, and chicken ethical stance, and thus it is not possible to signal this or reap any benefits to social moral reputation. The impact of better welfare animal practices on animal suffering and human morality is beyond the scope of this chapter. But it seems that people are much more likely to think they are buying humane animal products than they really are (75% believe they are buying human products versus 99% of products coming from factory farms) (Reese, 2017). Given that billions of animals are farmed for food across thousands of facilities, and the food industry remains politically powerful, it’s difficult to enforce humane standards. The little evidence we have, such as that undercover animal advocacy operations seem to always discover cruel mishandling and mistreatment of animals, even on farms with ‘humane standards’, doesn’t bode well.

Clean Meat Fifty years hence, we shall escape the absurdity of growing a whole chicken in order to eat the breast or wing by growing these parts separately under a suitable medium. (Winston Churchill, 1932: 26)

It’s unlikely that individual consumer choices are going to significantly reduce the demand for animal products. Polls show Americans say they are very concerned about animal welfare, but this doesn’t translate into their


choices as consumers. One experiment on the ‘vote/buy gap’ – the tendency for consumers to vote for higher welfare standards but not to buy in accordance with these ideals – showed that 80% of consumers who chose to buy cookies made with battery cage eggs said that battery cage eggs should be illegal (Paul et al., 2019). The vast majority of people in Western societies would state that they are morally repulsed by slavery, and yet when a report documented that around one-third of shrimp produced in Thailand involved slave labor (Hodal and Lawrence, 2014), this did not change the huge demand for shrimp, and there is still slavery in the supply chain now (Clark, 2019). From a historical perspective, no movement has ever made significant gains from endorsing individual boycotts of largescale industries. An analysis of the abolitionist movement against human slavery showed that boycotting slave-produced goods was not effective, and was not that widespread, even among abolitionists (Witwicki, 2017). One possible solution to the problem of animal suffering caused by meat production is in vitro meat, cultured meat, or ‘clean meat’. Clean meat is the ‘cultivation of food grade animal tissues in carefully controlled environments’ (McLaren, 2014: 1). Clean meat holds the promise of replacing slaughter-based meat production. The fast rate of technological innovation in clean meat seems to have overcome some of the obstacles I wrote about several years ago (Fleischman, 2013). The main obstacle has been price preventing clean meat from meeting market demand. Creating a structure for in vitro meat to grow, to keep it at the correct temperature and inundated with nutrients for cell division, and free from contamination, made it prohibitively expensive. The debut clean meat burger in London created by Mark Post a few years ago cost about $330,000 to make (McLaren, 2014). But, after many failed predictions (Madrigal, 2013), it seems clean meat might soon be coming to market. A few major obstacles seem to have been overcome since clean meat is now being taste-tested for the public.



However, our evolved psychology may still present obstacles to the uptake of clean meat. Food preferences crystallize at an early age (Birch, 1999) and people feel disgust about foods that are unfamiliar to them. To increase demand for clean meat, ethical vegetarians might at least be willing to try it. However, in two small surveys it was found that the majority of vegans and vegetarians (71%) were unwilling to try in vitro meat (Fleischman, 2012). A larger survey of vegetarians found a similar result, with 73% unwilling to eat it (Dahlgreen, 2013). In my survey (Fleischman, 2012), it seemed that the stipulation that in vitro meat would cause no more animal suffering than plant foods did not change attitudes against in vitro meat, leaving disgust as the most probable cause. Indeed, 32% of vegans explicitly cited disgust as a reason they would not want to try it. There is some research indicating that moral vegetarians are more disgust-sensitive overall (Rozin et al., 1997). However, it is disappointing that this group is likely not going to be leading the way towards clean meat. Vegan and vegetarian attitudes are probably not that important for the future of clean meat. The most important thing is uptake from people eating the most meat and populous countries whose meat consumption is increasing, namely China and India. There is some hopeful news as familiarity with clean meat increases. In one survey of American adults, the majority were willing to try clean meat (65%) and about onethird said they would be willing to eat clean meat as a replacement for farmed meat (Wilks and Phillips, 2017). Men, who tend to eat more meat than women, also had a more positive view of clean meat in this US sample. In a sample of over 3,000 participants from the United States, India, and China, 93% of Chinese participants said they were likely to purchase clean meat, as were 86% of Indian participants and 75% of US participants (Bryant et  al., 2019). In keeping with ideas about sex differences and food aversions, men and those who are less disgust-sensitive are more favorable towards clean meat (Bryant and Barnett, 2018).

If clean meat is going to become an ­­ important solution to the myriad problems of the global animal industry we have to learn from history, both evolutionary and cultural. As I mentioned above, we as humans are more concerned about meat contamination than other food sources. Any warning about clean-meat contamination, or a recall, could have pervasive long-term effects and mean that people will continue to buy more familiar meat from animals that suffered and died for decades to come. Branding clean meat as ‘clean meat’ rather than in vitro meat, lab meat, cultured meat, or synthetic meat was an important first step in combating disgust sensitivity. One major reason that genetically modified food wasn’t an unalloyed success was because of perceptions of unnaturalness (Mohorčich, 2018), another form of disgust response that can be reduced by increasing consumer familiarity. Framing is also important; meat producers learned long ago that mentioning the animals themselves reduced consumer acceptance (Zaraska, 2016). We don’t really want to know how the sausage is made, and less detail about how clean meat is produced generally improves attitudes (Bryant and Barnett, 2018). We as humans are more concerned with what’s delicious than what is virtuous; consumers rarely care enough to buy or boycott any product because of its moral ramifications (Bryant and Barnett, 2018). That’s why making sure that clean meat is tastier than conventional meat can go a long way. Finally, the rise of zoonotic diseases like Covid19 and H1N1 can hopefully turn the tide of disgust sensitivity in the other direction, against forms of animal agriculture that can cause pandemics.

VIRTUE SIGNALING AND ANIMAL WELFARE Stop smirking. One of the most universal pieces of advice from across cultures and eras is that we are all hypocrites, and in our condemnation of others’ hypocrisy we only compound our own. (Haidt, 2006: 60)


Most animals are hidden from public view or otherwise incapable of communicating about their suffering and cannot leverage reputational concern (Sperber and Baumard, 2012). However, because people can advertise their moral attitudes in so many ways now, from vegan bumper stickers to social-media posts, there is more widespread concern about the suffering of animals than at any previous point in history. Our moral attitudes do not occur in a vacuum. Advertising our moral qualities to others for social benefits, whether these moral qualities are instantiated in behavior or just ‘cheap talk’, is known as virtue signaling (Miller, 2019). When definitions of moral behavior shift in social groups, culture can change moral behavior to the extent that it’s available for virtue signaling. This is one reason that animal advocates have had so much more success with institutional change over individual changes (Reese, 2018). People are willing to advertise moral ideals by signing a petition or publicly advocating that a business change its harmful animal practices, but are unwilling to engage in more costly and less visible individual boycott. Our moral identity is important to us; there is a strong psychological motivation to present ourselves as more moral than others (Kurzban, 2011) and to resist others’ claims of moral superiority. This creates fraught relationships with ‘moral minorities’ who consider themselves to be in the moral vanguard – including animal advocates, vegans, and others who hold and display a virtuous identity. Vegetarians are widely disliked by the rest of society. In one study, participants reported disliking vegans and vegetarians more than atheists, asexuals, immigrants, or Blacks, but reported being more willing to hire or rent to vegans and vegetarians than all other target groups (MacInnis and Hodson, 2017). In this study, only drug addicts were more disliked than vegans. Because moral rules are considered to be universal, meeting someone who holds different or more strict moral standards than you do can be seen as an implicit indictment of your behavior. People tend to rate themselves


as more moral and better than others; meat ­eaters rate vegetarians as more moral than the average person, but rate vegetarians as less moral than themselves (Minson and Monin, 2012). Maintaining a moral reputation is a major reason that meat eaters rate vegetarians negatively. They anticipate that vegetarians are judging them and will communicate their moral condemnation of meat eaters to others. Meat eaters rated vegetarians more negatively when they were first asked to consider how much vegetarians might judge them, and meat eaters expected vegetarians to judge them three times more negatively than they were actually judged (Minson and Monin, 2012). Of course, it’s possible that because being judgmental is widely considered immoral, vegetarians were reporting less judgment than they actually felt. One interesting aspect of the Minson and Monin (2012) study was that some meat eaters were first given an opportunity to say what they thought about vegans before later reporting how much they agreed with their moral message. Participants in the study described vegetarians as ‘weird’, ‘preachy’, and ‘sadistic’. But afterward they were more likely than other participants who did not derogate vegetarians to say that they agreed with the moral message of vegetarianism. This is interesting from an evolutionary reputationmanagement perspective. Reducing someone else’s reputational status relative to your own might increase your likelihood of taking their message seriously; you don’t have to fight as hard to make yourself look good. Moral change often happens when we want to socially affiliate with others, and negative impressions of activists – from animal advocates to social-justice advocates – undermines the cause (Bashir et  al., 2013). Importantly, for any moral advocate, they must remember that others are going to have strong incentives to derogate them and will scrutinize them for moral inconsistency (Monin, 2007). Anyone advocating a major change in moral priorities must remember that people have spent years honing their virtue-signaling strategies,



and will not take kindly to someone arguing that they have really been hugely less virtuous than they thought. The evolutionary psychological challenge for animal advocacy is to nudge people to show more concern for animal suffering, without feeling like their whole virtue-signaling identity has to be jettisoned and rebuilt from scratch.

CONCLUSION Evolutionary explanations are often maligned because they are said to excuse or normalize violence. To say animal cruelty and inflicting animal suffering is normal and natural is not to minimize the suffering of animal victims either as the result of any individual’s sadism or the large-scale production of animal products. To say that our nurturing instincts predispose us to be kinder to animals that demonstrate kinship cues or that elicit the cuteness response is not to say that these responses are moral. To say that we are more disgusted by meat that looks more like the animal it came from than meat that looks more abstract is not to say it is more moral to eat meat packaged in cellophane. And to say that we virtue signal about our moral behavior is not to say that moral behavior isn’t important or that cynical motivations render moral behavior immoral. When we take our moral intuitions as moral rules we project and institutionalize our evolved moral blind spots into the world, often making it worse for others. Advocacy requires understanding. If animal suffering is an ethical issue, we have to be realistic about our incentives to signal, our functional emotional responses and what comprises our evolved moral psychology towards animals.

ACKNOWLEDGMENTS For helpful feedback, thanks to Hal Herzog, Geoffrey Miller, and Todd Shackelford.

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Applications to Law and Order

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8 Evolutionary Psychology and Political Institutions Michael Latner and Elissa Feld

Biology and political science have a long, symbiotic relationship in their shared focus on conflict and cooperation between organisms. Many of the major puzzles in biology and political science, from the emergence of cooperation, and the threat of parasitism and selfishness, to the dynamics of collective decision making and the evolution of morality, are interwoven in early, pre-Darwinian works. As these areas of study developed into separate professional disciplines in the early 20th century, they would part ways with considerable tension before returning to such fundamentals with the advent of modern evolutionary psychology. In this chapter, we survey the literature surrounding three major areas where the study of political institutions and evolutionary psychology intersect: the evolution of cooperation at the micro-level; the emergence of complex political systems; and democracy as a major evolutionary transition in nature.

THE EVOLUTION OF COOPERATION The Scottish Enlightenment, especially the work of David Hume, had a significant influence on James Madison’s theory of republican government (Mclean, 2005). Hume’s discourses on competition and selective retention would figure prominently in Madison’s constitutionaldesign principles, especially his commitment to design institutions responsive enough to ‘guard against the cabals of a few’ but not subject to so much ‘mutability’ and ‘incessant changes’ that ‘no man who knows what the law is today can guess what it will be tomorrow’ (Palmer, 2002: 109). Hume’s concern about the degenerative effects of extreme elements in political competition, as well as the capacity for such diverse interests to be ‘serviceable’ to the public interest, would be fully developed in Madison’s writings on faction, the modern study of political institutions, and constitutional design (Madison et al., [1788]2008).



Charles Darwin studied both Hume and Madison’s contemporary, the Reverend Thomas Malthus, whose Essay on the Principle of Population (Malthus, [1798]2013) began to quantify the relationship between competition for resources and human-population growth (Hamilton et al., [1788]1998). Madison himself understood that the world would be ‘much indebted to’ Malthus for his work, though a decade before Malthus’ Principle was published, Madison had already been reflecting with Thomas Jefferson on the degenerative social effects of concentrated resources among the ‘idle rich’ and the potential threat of overpopulation (Madison, 1786; McCoy, 1980). The threat of parasitism on social prosperity and development was on the mind of these institutional reformers. The Principle of Population would also lead Darwin to the insight that with selection pressures under conditions of scarcity ‘favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work’ (Darwin, [1838]2011). Hume may have also been influential in the way that Madison and Darwin thought about the emergence of cooperative behavior within the context of group competition, an insight neglected by Malthus. Consider Hume’s account of the logic of reciprocity in his Treatise on Human Nature (Binmore, 1994: 261): I learn to do service to another, without bearing him any real kindness, because I foresee, that he will return my service in expectation of another of the same kind, and in order to maintain the same correspondence of good offices with me and others. And accordingly, after I have serv’d him … he is induced to do his part, as foreseeing the consequences of his refusal.

Darwin certainly recognized the dynamics of reciprocity at play in cooperative behavior and the dilemma of moral development. Darwin viewed morality as the highest principle of human development, but he also saw that in group competition the ‘bravest men’

who came to the front at war and ‘freely risked their lives for others, would on an average perish in larger number than other men’, producing fewer offspring (Darwin, 1876: 130). Immoral (selfish) actors would, on average, out-produce their braver comrades, eventually driving the trait of bravery out of the population. However, competition between groups could change the selective dynamics: It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an advancement in the standard of morality and an increase in the number of well-endowed men will certainly give an immense advantage to one tribe over another. (Darwin, 1876: 132)

This is the basis of the cooperation dilemma, and the question of how cooperative or ‘good’ traits could gain a selective advantage through social decisions was a central feature in early social choice theory. On that topic another contemporary of Madison, the Marquis de Condorcet, also played a major role. He formally showed that voters seeking the best collective decision for their group could rely on majority rule to most likely yield a ‘correct’ decision, if the probability of a voter being right was greater than 50%, and that the probability of a correct outcome approaches 100% as the size of the electorate increases (Young, 1988). Condorcet’s probabilistic explorations at least indirectly influenced Madison as well (Schofield, 2005b), specifically the proclamation in Federalist #10 that ‘If the proportion of fit characters be not less in the large than in the small republic, the former will present a greater option, and consequently a greater probability of a fit choice’. (Hamilton et al., [1788]1998). While many thinkers who subsequently took the mantle of ‘Darwinist’ would continue to think about evolution purely in terms of competition, following T. H. Huxley’s famous dictum that nature ‘is on about the same level as the gladiator’s show’ from the ‘point of view of the moralist’ (Kropotkin et al., 1955), others would focus on empirical observations of cooperation in nature and seek to explain them. In particular,


the Russian naturalist Peter Kropotkin’s observations led him to believe that evolution was about combination as much as competition. He observed that reciprocity was widespread, even between species. Kropotkin’s analysis of social insects, parental behavior, and associative activities like pack hunting, integrated with an analysis of medieval guilds, led him to the conclusion that mutual aid was as much a law of nature as mutual struggle. In addition to anticipating much in the scientific study of altruism, Kropotkin’s Mutual Aid remains a foundational work of anarcho-communism (Kropotkin, 2017). J. B. S. Haldane (also a vocal communist) was perhaps the first to begin formalizing the link between genetic traits and sociality (Haldane, 1941). In The Causes of Evolution, Haldane first proposed that reciprocity could spread in a population if the genes determining it were carried by individuals whose offspring benefitted from the presence of the gene in their nearby relatives (Haldane, 1932). Similarly, R. A. Fisher, whose Genetical Theory of Natural Selection heralded the modern synthesis in evolutionary biology, focused considerable attention on how degrees of genetic relatedness affected individuals living in different types of populations (Fisher, [1930]2000). It is telling that the politically conservative Fisher was attracted to understanding how ‘distastefulness’ in insect larvae could spread in a population. He reasoned that nasty tasting larvae would provide increased protection for their siblings by driving away predators, such that the genetic benefit of an eaten larvae could be substantial. Perhaps Fisher’s politics motivated his interest in distastefulness: recent research suggests that sensitivity to disgust is linked to conservatism (Murray, 2012). Sadly, both Haldane and Fisher were advocates of eugenics (Haldane coined the term ‘cloning’ and Fisher headed the Department of Eugenics at University College London), but unlike Haldane, Fisher viewed the fall of civilizations as a function of declining fertility rates of the upper classes, and he was concerned about encouraging


allowances for large working-class families and those who possessed less ‘innate capacity for intellectual and emotional development’ (Fisher, [1930]2000). The greatest breakthrough, and the reunion of evolutionary biology and political science, began after W. D. Hamilton broke the code for kin selection (Hamilton, 1964a, 1964b). Adapting economic cost–benefit analysis, Hamilton showed how natural selection would allow for altruism to evolve while still maximizing individual fitness. In a series of articles, he demonstrated how natural selection can favor altruism between relatives when the product of the relatedness of individuals and the benefits of reciprocity outweigh the individual costs. The concept of inclusive fitness was born, as was Hamilton’s legacy as one of the greatest evolutionary theorists of the 20th century. The next giant step would be taken by Robert Trivers, who extended Hamilton’s work to non-kin reciprocity, such as bird warning calls, the symbiosis between cleaner and predator fish, and broader social interactions. His 1971 publication ‘The Evolution of Reciprocal Altruism’ showed how net benefits could be accrued between non-relatives through social exchange, and how cheating and spiteful behavior could be regulated through the evolution of moralistic aggression (Trivers, 1971). Trivers’ work opened new opportunities for the integration of the behavioral sciences, as he sketched out how the analysis could extend to complex, multi-party coordination, the emergence of norms and collective punishments (and rewards), generational return effects, and the like (Trivers, 2006). Soon after, John Maynard Smith (a student of Haldane) and George R. Price (a friend of Hamilton) would formalize the Evolutionarily Stable Strategy (ESS) and initiate evolutionary game theory in ‘The Logic of Animal Conflict’ (Smith and Price, 1973), directly addressing Darwin’s dilemma of moral development. An ESS is a strategy (social interaction where agents compete over a resource, such as food, with payoffs dependent on both



agents’ strategies) that is stable once it is fixed in a population. If agents will not do better (more offspring) by employing a different strategy, or perturbations from ‘mutant’ strategies cannot successfully invade and replace it, the trait becomes fixed in the population as the offspring of the winners replace those with lower payoffs. The ESS has not only become central to the explanation of human evolution in evolutionary psychology, it has been adopted in political science as a means of understanding evolution through institutions. That pivotal moment came when W. D. Hamilton teamed up with political scientist Robert Axelrod to publish ‘The Evolution of Cooperation’ in 1981 (Axelrod and Hamilton, 1981), one of the most cited publications in political science (Peress, 2019). Axelrod’s computer tournaments provided output for simulations using competing strategies in repeated Prisoner’s Dilemma (PD) games. In such games, both agents know they would do better if they cooperated, but the payoff is higher for individuals to defect rather than be exploited. Axelrod and Hamilton described how an eloquently simple logic of cooperation (essentially do unto others, the ‘Tit for Tat’ strategy submitted by anthropologist Anatol Rapaport) could emerge as an ESS, given a high-enough probability of future interaction between cooperative agents. Their analysis demonstrated how ‘the benefits of life are disproportionately available to cooperating groups’ and from it they drew several strategic considerations: • Be nice: don’t be the first to defect. • Be provocable: return defection for defection, cooperation for cooperation. • Don’t be envious: focus on maximizing your own ‘score’, as opposed to ensuring your score is higher than your ‘partner’s’. • Don’t be too clever: signal clarity is crucial.

Successive work on iterated PD has relaxed the highly simplifying assumptions built into the original model, continuing to produce important insights, including those about the importance of forgiveness and reputation (Nowak, 2006). Today, the study of

cooperation is a fertile interdisciplinary field, identifying multiple stable states of cooperation, the foundations of pro- and anti-social behavior, the crucial role of structured interaction, and the ways that institutions cultivate cooperation (Alford and Hibbing, 2004; Lopez, 2017; The Cooperative Human, 2018). One of the most relevant ongoing debates concerning institutional analysis has to do with the concept of ‘strong reciprocity’ and the role of institutions in sustaining cooperation. A body of scholars have challenged the orthodox view of the reciprocal altruist as self-regarding, developing an alternative model of group-beneficial pro-social behavior (Bowles et al., 2003; Bowles and Gintis, 2011; Fehr and Gächter, 2002; Henrich and Boyd, 1998). Whereas kin selection, reciprocal altruism, indirect reciprocity, and signaling explain behaviors that appear costly but are repaid to genetic relatives, the strongreciprocity hypothesis posits that a genuinely altruistic behavior can be adaptive, but critics are unconvinced (Burnham and Johnson, 2016). The answer to this controversy is immensely important for the design of political institutions, and it has rightly become a major focus of scientific attention (Abbot, et  al., 2011; Ferriere and Michod, 2011; Herre and Wcislo, 2011; Nowak et al., 2010).

THE EMERGENCE OF COMPLEX POLITICAL SYSTEMS The use of biological metaphors to explain the emergence and persistence of political systems dates back at least to Thomas Hobbes’ Leviathan with its cover art of the Sovereign King, whose body is literally constituted by the multitude of citizens, obedient co-signers of the social contract, the body politic represented by one man (Hobbes, [1651]2009). Walter Bagehot’s ‘Physics and Politics’ was probably the first to explicitly apply Darwinian selection and inheritance concepts to political society (Bagehot, [1869]2009). Writing in


1869, Bagehot made a case for liberal-democratic institutions having emerged from more conformist, dictatorial restraints as a moral achievement. The selective process had supposedly refined the nervous systems and moral capacity of ‘accomplished’ elites, creating opportunity for more complex decisionmaking institutions and social progress. Bagehot was also among the earliest in a long line of ‘Social Darwinists’ to leverage pseudo-scientific accounts of racial inequalities to justify an ideological theory of the state. John William Burgess similarly believed that only ‘superior’ races had acknowledged the moral ‘duties of civilization’ (Gunnell, 2004). Burgess established the US political science degree at Columbia University, where he taught comparative constitutional law, and his vision of political science emphasized the training of career government bureaucrats, as well as civic education as a sort of ‘democratic’ training, within the confines of his racist ideology. After World War I, and the embrace of scientific racism within fascism and Nazism during World War II, social Darwinism was largely discredited and abandoned by political science, at least publicly. Post-war social scientists turned to formal social choice and game theory as a framework to explain political institutions. Properties of social-decision rules, or ‘constitutional conditions’ in the words of Kenneth Arrow, where individual values are treated as inputs, became a focal point of analysis (Arrow, 1970). One of the most influential political scientists to emerge from this period was Robert Dahl, whose Arrow-inspired analysis of social choice procedures shaped our understanding of how popular sovereignty and political equality are instituted (Dahl, 1989, 2006). Nevertheless, Dahl’s image of the locus of democracy in US government as fluid, pluralist bargaining assumed an equilibrium of social consensus, with no direct focus on evolution or adaptation (Gunnell, 2004). Dissatisfied with the historical bent of most political science and unconvinced by Dahl’s group bargaining theory of political


behavior, David Easton’s theoretical explorations reflected his study of physiology and systems biology, specifically the concept of homeostasis and the capacity of evolved systems to react to environmental stimuli with equilibrating responses (Cannon, 1963). As a member of the University of Chicago’s Committee on the Behavioral Sciences, he was committed to the integration of biological and social scientific knowledge, co-authoring ‘Projects and Problems of Homeostatic Models in the Behavioral Sciences’ with psychologist James G. Miller and anthropologist Anatol Rapoport, among others, in 1953 (Fontaine, 2016). Easton’s work transformed the study of political institutions by nesting them within a living-systems framework. Easton was primarily interested in understanding how institutional arrangements regulate demands on a political system, shaping the way that social choices are put into effect as policy outcomes, which he elaborated in A Framework for Political Analysis and A Systems Analysis of Political Life (Easton, 1965, 1979). Among his many contributions to the study of institutions, Easton’s ideas about how regimes generate support through the allocation of biological and social resources, and regulation of social values, stand out (Easton, 1979). Easton was among the first to flesh out how emotive attachment to codified social roles, and the social status they yield, supply the behavioral energy upon which a political system depends for its survival. In the last few decades there has been increasing convergence of Easton’s macrolevel type of structural-constraints analysis and the micro-foundations of cooperative game theory. Formalization of political authority occurs when communicative artifacts, from mating and marriage practices to landtenure customs, nomenclature, measurement, and other forms of codification, instantiate a ‘high degree of mutual predictability’ with large-scale coordination of, and thus control over, the allocation of biological and social resources (Easton, 1979: 329). Just as valuable biological information is correlated



across generations through the germ line, institutional transmission of communicative artifacts sustains biocultural complexes that can greatly enhance the fitness of participants (Corning, 1995). Indeed, the production and management of knowledge is itself a commons dilemma (Frischmann et al., 2014). National constitutions are rules for strategy selection. That is, constitutional regimes operate to regulate social niche-construction strategies (Santa Fe Institute, 2016). As Brian Skyrms notes in Evolution of the Social Contract (2014), here strategies come to the fore as units of selection, and individuals recede into the background (much as genes do in the biological literature). The success of collectively selected strategies (laws) is based on their success as behavioral phenotypes, and how well populations converge on successful strategies of social interaction (Skyrms, 2014). Our understanding of institutions as carriers of cultural transmission has been built on decades of successful modeling of cooperation, complexity, and culture (Axelrod, 2006; Cavalli-Sforza and Feldman, 1981; Creanza and Feldman, 2014). Studies of the evolution of complexity show that, as regulators of niche construction, political institutions face some universal information-processing problems. For example, the tradeoff between exploring alternative strategies and reliance on the status quo is a general dilemma in organizational productivity (March, 1991). The ‘explore/ exploit’ dilemma arises from the inability to optimize both the exploration of potentially adaptive/productive strategies, and cashing in on the value of e­ xisting strategies. Without commitment to a strategy, a system can ‘boil’ in the endless search for optimal alternatives, but without generating variation there are fewer alternatives to optimize, making it less likely to find a better alternative than the status quo. In the context of political institutions these constraints correspond to the bounds of political authority and social choice. The potential range of participation in collective decision making for a population ranges from N (total

population) to one, or pure dictatorship. Both arrangements constitute cooperative regimes in the sense that in a regime of N decision makers, all preferences are taken into consideration, maximizing the communication channels and flow of information to be processed, but also coordination costs (the resources required to take everyone’s preferences into account) and potential ‘boiling’ as each individual does their own thing. Alternatively, pure dictatorship may be the least costly social choice mechanism in terms of coordination costs, but conformity costs (everyone obeys the dictator) tend to be extreme, in part because there is little effort to search the landscape for mutually beneficial strategies (Page, 2008; Zhou, 2011). This tradeoff maps closely onto the solutions typically proposed for the management of public goods, or the ‘tragedy of the commons’. Ecologist Garrett Hardin famously argued in several papers (around the same time that models of evolutionary cooperation were emerging) that species are generally unable to cooperate for the greater good (Hardin, 1968). In addition to being another Malthusian throwback who believed that those who won superior intellect through the genetic lottery (whites, of course) should deploy abortion and sterilization to maintain limited population growth because ‘freedom to breed will bring ruin to all’ (Hardin, 1968: 1248), he popularized the problem of maintaining public goods through his analogy of livestock management on shared grasslands, an iterated PD game emphasizing the freerider problem and defection as rational in the short term but irrational in the long run. Hardin’s solutions to the tragedy were either privatization and strong property rights, in order to incentivize individual owners to be stewards over their own land, or the very Hobbesiansounding ‘mutual coercion, mutually agreed upon’ typically interpreted as collectivization. Willfully or otherwise, Hardin was ignorant of the degree to which many commons were already being governed under ‘mutually coercive’ social structures that have evolved to


manage the ‘explore/exploit’ dilemma without resorting to either strict privatization or collectivization. No individual has played as large a role in demonstrating the capacity of local organizations to manage common resources as Elinor Ostrom (Ostrom, 1990, 2010, 2013). While Ostrom’s work fits within the broader fields of political economy and organizational behavior (Levi, 1989; March and Olson, 1971; Olsen, 1976), her approach to core design principles, the Institutional Analysis and Development (IAD) framework, is distinctly Darwinian. Ostrom’s acceptance speech for the 2009 Nobel prize in economics, ‘Do Institutions Evolve?’, recounts decades of research she and colleagues have developed to understand how biophysical systems, participant heterogeneity, and operational rules shape the governance of commons (Ostrom, 2013). A set of ‘default’ rules highlights what Ostrom has discovered as core design principles: • • • • • • •

Clearly defined group boundaries Proportionally equivalent costs and benefits Collective-choice mechanisms Monitoring Graduated sanctions Fast and fair conflict resolution Polycentric governance (tiered rule-making)

The work of Ostrom and other political economists, including Douglas North, Margaret Levi, Barry Weingast, and Geoffrey Hodgson, has engendered a generalized Darwinian approach to the study of institutional change that stands independent of genetics and biology (Aldrich et  al., 2008; Fürstenberg, 2016; Hodgson, 2004; Levi and Weingast, 2019; Wilson and Gowdy, 2013). We have learned much from empirical field studies that have demonstrated the adaptiveness of local communities, including tribal communities that Hardin surely would not have imagined were cooperatively stable. Large-scale societies require complex, adaptive institutions to transmit norms of conflict resolution and morality (Bowles et al., 2003; Bowles and Gintis, 2011; Ehrlich and Levin, 2005; Levin, 2014). Legal systems


exhibit properties that Walker and Davies (2012) characterize as an informational structure that gains causal efficacy over matter, in this case, behavior: they are explicit instructions, decontextualized from specific behaviors to classes of behaviors, applicable to classes of agents, designed to yield high levels of predictability (Bowles and Gintis, 2011; Boyer and Petersen, 2012). Rather than being directly transmitted, legal expectations are learned, deriving from hard-wired moral intuitions, but converted into ‘publicly scrutable processes’ that modify social interaction from the ‘top down’ (Boyer and Petersen, 2012). According to Boyer and Peterson, like our biophysical equipment, our evolved cognitive systems operate more reliably in matching environments (ideally the environment of evolutionary adaptedness). As a result, we are motivated to match our environments to those cognitive systems, while the modification of environmental niches creates and maintains selective pressures that favor adaptions matched to them (Laland et al., 1999). Richard Dawkins famously called this sort of niche construction The Extended Phenotype (Dawkins, 1999), based on the evolutionary logic that the quality of an environmental niche (a spider web, a beaver dam, a human settlement) is correlated with genetic variation, in that an allele for better niche construction enhances the fitness of the organisms expressing it. In an environment with good nest-building materials, the best nest builders will proliferate the genes for building nests with those materials, as their offspring increase in frequency through the population. Constitutional environments will likewise favor the selection and spread of behavior traits and cultural norms, such as a sense of justice, under constitutional conditions that favor it.

DEMOCRACY: A MAJOR EVOLUTIONARY TRANSITION? Representative democracy encompasses a range of regimes that have emerged quite



recently on the human scene, possibly in response to the conformity costs imposed by more authoritarian, dictatorial regime structures (Latner, 2017). The core design principle of democracy is political equality, or fairness. Political theory on procedural justice has contributed to our understanding of cooperation at all levels of life through a sort of cross fertilization. Specifically, the political philosopher John Rawls’ concept of the ‘veil of ignorance’ played prominently in the social theory of another Michigan biologist, Richard D. Alexander (Alexander, 2017; Rawls, 1999). The basic logic is that if the only way to be sure one gets ahead is to promote rules that will improve overall welfare, fair laws should be favored for selection. What emerges is a society that applies laws equally to individuals regardless of their status, or justice as fairness. Alexander saw that the enforcement of mutualistic cooperation requires limiting opportunities for cheating, such that agents can only increase their success by increasing the success of others (Frank, 2013). He also saw how natural selection could favor the suppression of internal competition by drawing on the work of E. G. Leigh, probably the first modern biologist to use a political analogy, equating the genome to ‘a parliament of genes: each acts in its own self-interest, but if its acts hurt the others, they will combine together to suppress it’ (Leigh, 1971). Later analysis has supported the idea that the cellular infrastructure of meiosis in sexual reproduction is favored, in part, as a mechanism to thwart parasitic conflict at the genetic level (Burt and Trivers, 2008; Howard and Lively, 1994). Similarly, Alexander’s argument that socially imposed monogamy levels reproductive opportunity, and in doing so reduces the pool of unmarried men, has found support in research that shows monogamy is associated with reduced rates of homicide, rape, and related violence (Henrich et al., 2012). Bryan Skyrms’ Evolution of the Social Contract and later work brings us full circle through the evolution of cooperation

to the operation of constitutional structure (Skyrms, 2014). His eloquent essay ‘Sex and Justice’ (1994) compares the puzzle of sex ratios (which led to Fisher’s game-theoretic insights) to the evolution of justice. Skyrms shows how, like many observed sex ratios, fair division (50/50) is an attractive equilibrium in repeated interactions. Crucially, if interactions between more cooperative agents can be correlated (a higher probability that they interact with one another instead of greedy agents), then the cooperative norm ‘share and share alike’ becomes a stronger evolutionary attractor and will emerge as an ESS. Skyrms shows how mechanisms for the evolution of cooperation, from kin selection to ‘group’ selection, spatial interaction, and the repression of competition, are all linked to increasing correlation and cooperative association (Skyrms, 2014). Skyrms has also brought attention to the problem of ‘negative correlation’ and how spiteful behavior can be sustained through correlated interactions, such as when a reputation for ‘fighting too hard’ (to the detriment of self and opponent) may enable agents to win future contests more easily in repeated encounters (Skyrms, 2014). The likelihood that political equality is a fit alternative against dictatorial hierarchy and anarchy is empirically supported across a variety of fields. First, recent developments in social choice theory have confirmed that proportional representation, which most accurately translates votes into seats of political power, is the closest approximation to political equality in electoral-system design (Hout and McGann, 2009). Contemporary experimental tests further support Condorcet’s position that majority rule outperforms alternative strategies, including dictatorship (Hastie and Kameda, 2005; Sorkin et al., 1998), and regimes that more closely approximate political equality (PR and simple majority rule) tend toward greater redistribution and responsiveness, as predicted (Acemoglu et al., 2009; McGann and Latner, 2013). Representative assemblies, electoral systems, thresholds for legislative decision making and policy


execution all reflect fundamental features of institutional niche construction and cooperative decision making (Latner, 2017). Steven Frank has, more than nearly any other evolutionary thinker, shown how the policing of competition, or reduction of opportunities for exploitative behavior, correlates individual payoffs and can sustain group cohesion (Frank, 2003, 2011, 2013). Reducing opportunities for exploitative behavior through political equality may result in both higher levels of redistributive sharing and flexible responsiveness in resource management, making it an evolutionary attractive equilibrium (McGann and Latner, 2013). The historical record is also supportive of the evolutionary democracy hypothesis. The number of regimes holding minimally free and fair elections has nearly doubled since 1990, from 69 to 122 according to Freedom House (‘Freedom in the World’, 2014). Moreover, among electoral democracies, major electoral reforms have been decisively in the direction of more proportional representation (Soudriette and Ellis, 2006). This follows the evolution from simple ‘originating’ systems in early electoral systems to electoral rules that reduced the frequency of single-party dominance that had emerged (Colomer, 2001, 2007). At the other extreme, hyper-permissive systems demonstrably produce greater instability in governing coalitions, lower cabinet duration, and greater difficulty committing to comprehensive policy platforms (Shugart and Wattenberg, 2001; Taagepera, 2007). Reforms in these systems have generally maintained proportionality along with consolidating legislative power in the direction of greater accountability (Shugart and Wattenberg, 2001). Of course, political institutions do not operate exogenously on behavior, independent of the complexity of other social systems. Population heterogeneity and inequality in social resources obviously shape institutional performance and the prospects of regime persistence. For example, cultural mutation and cycles of stability are highly sensitive to interactions between transmission, selection,


and assorting of populations. For example, Creanza and Feldman have considered education norms, specifically the belief that women should receive secondary education and delay childbirth (Creanza and Feldman, 2014). The probability of fixation of the belief is shaped by lower fertility among those women who take part, as well as lower infant mortality among the same families, and future sorting in offspring mating practices. Similar dynamics may impact the norm of democratic participation and investment in the considerable responsibilities of democratic citizenship, not to mention the interaction between education, socialization, and support for democratic institutions, especially for women (Fox and Lawless, 2014). Asymmetries between the (de jure) constitutional and (de facto) economic allocation of political power also shape the dynamics of regime stability. Daron Acemoglu and colleagues have produced a number of analyses proposing that the threat of upheaval and benefits of anticipated economic growth have been primary drivers of elite-led expansion in collective decision making (Acemoglu et al., 2009, 2011; Acemoglu and Robinson, 2013). Peter Turchin has proposed a broader model of democratic evolution that emphasizes the role of exogenous threats, with a similar sequencing that cooperation and enfranchisement are frequently followed by periods of economic inequity and political instability (Turchin, 2013, 2016). These and other analyses point toward higher potential for upheaval under greater economic inequality, when lower classes (and their offspring) feel they have nothing to lose, and when the prospective benefits of a major transition outweigh the perceived costs of disruption. The interplay of group conditions and specific conflict-reduction mechanisms can determine the fate of a regime’s future. If increasing inequality or prolonged economic stagnation fuel animosity between competing economic classes, it will lead to increased demand for the powerful to invest in economic and political mechanisms to better preserve common



goods, and consequently the stronger taking over more institutional control (Frank, 2011). Whether that control is more equitable or ‘extractive’ (parasitic) may in turn depend on the prior fixation of economic and cultural traits, like democratic norms among elites. Further, the adequacy of a political solution will depend on whether competition among reformers can be sustained and a coalition holds, for example by requiring coalition building within broad-based political parties, or whether fragmented interests and the work of compromise must be channeled into a representative assembly (Balinski and Young, 2001; Cox, 1997). In electoral system science, the general pattern that proportional electoral systems are associated with higher rates of women’s representation is a puzzle that requires consistency between macro- and micro-level explanations (Reynolds et al., 2005). One consistent model that has been applied to the puzzle is social contagion, where smaller parties in proportional systems differentiate themselves (at lower cost than under single-seat systems) by listing more women on party lists, driving larger parties to follow suit (Matland and Studlar, 1996). Several outlier systems such as Israel and Malta exhibit very low percentages of women in parliament despite using rather pure versions of PR, and incorporating models of variance in child-rearing strategies would provide a fuller understanding of these strategies (Lane, 1995; Rule, 1987). Evolutionary psychology has also contributed to our understanding of sex and gender dynamics in campaign and election studies. For example, a large body of research has demonstrated that men and women differ in candidate support based on factors like facial appearance and body image, with men preferring more attractive female candidates and women preferring approachable male candidates (Chiao et al., 2008; Dolan, 2014). However, electoral contexts interact with these abstract preferences in ways that shape vote choice, especially partisan signaling and contextual priming emphasizing either

intergroup conflict or cooperation, such that both masculine (conflict) and feminine (cooperation) traits can positively contribute to the perception of effective leadership traits (Dolan and Lynch, 2014; Grabo and van Vugt, 2018). The sub-field of evolutionary feminist studies is challenging stereotypes of bio-essentialism head on, and will surely aid our understanding of institutional design with relation to women’s and gender studies (Buss and Malamuth, 1996; Feminist Evolutionary Perspectives, 2019). Another example of the evolution of democracy is seen in contestation over voting rights in the United States. Epperly and colleagues have documented the dynamics at work in voter suppression as an exploitative form of ‘cooperation’ (Epperly et al., 2019). They show that under conditions of low state capacity and legibility (formalized authority through administrative records, etc.), as well as external constraints on state legislative suppression (the federal government), voter suppression under Reconstruction took the form of decentralized intimidation like lynching that peaked just before federal restraints on legalized suppression were relaxed, allowing Southern Democrats to re-take control of several state legislatures. In the mid 1890s, the inefficient and enforcement-costly strategy of lynching declined as the codified, more predictable discriminatory laws of Jim Crow (poll taxes, registration requirements, multiple-box voting, secret ballots, literacy tests, property tests, understanding clauses, grandfather clauses, and the white primary) came online. These electoral barriers on the representation and possible transmission of less oppressive social strategies kept the Southern caste system in place for several generations, and with it the cultural norms of segregation, revulsion at inter-racial marriage, and belief in the inherent inferiority of African Americans. The Civil Rights Movement, and Civil Rights Act of 1964, Voting Rights Act of 1965, and accompanying court cases marked a behavioral and legislative tipping point in


electoral reforms to expand racial representation and socioeconomic opportunity in the United States (Davidson and Grofman, 1994). The cultural impact on norms has been substantial, but complex. While Jim Crow era norms have largely collapsed within the white population, and broad support for political equality has spread across all populations, support for government efforts to address segregation and other discriminatory practices is still frequently opposed (Bobo et al., 2012). Surviving racial stereotypes and negative views of racial minorities today tend to be based in characterizations of group culture, rather than biology (Bazian, 2016; Bobo et  al., 2012; Kaufmann, 2019). Selective pressures, and the institutional regulation of cooperation and competition, have altered the fitness of racial norms. Over the last decade, Americans have experienced the consequences of relaxations on federal constraints with the weakening of the Voting Rights Act and reduced judicial oversight of discriminatory practices (Bentele and O’Brien, 2013; CNN, 2019; Keena et al., 2017). Predictably, attempts to discriminate against black voters and other groups are on the rise again, and as in the post-Reconstruction South, voter suppression is increasingly couched in terms of partisan calculations (Hasen, 2014). While existing laws arguably make these new efforts, which range from gerrymandering to voter list purging, voter ID laws, and proof of citizenship requirements, less effective than Jim Crow 1.0, there is little reason to believe that Jim Crow 2.0 will not become more egregious over time, or that efforts will not be made to restrict the franchise further if the Republican Party does not expand beyond its shrinking demographic base of support. In this event, the importance of evolutionary psychology is even more apparent, as scientists will need every tool at their disposal to educate and advocate for evidence-based policies to help inoculate the public, and fight back against the resurgence of racism and white nationalism in our electoral ecosystem.


CONCLUSION This brief summary of what the evolutionary approach has provided to our current understanding of institutional design and performance is far from exhaustive. But one final sign of the extent of recent integration between institutionalists and biologists that must be mentioned is the contributions that scholars of political institutions are making to biology. Political scientists are now researching animal institutions and collective decision making, a sure sign that the ‘life sciences’ properly understood are integrating under the umbrella of a generalized Darwinism (Akcay et  al., 2013; Conradt and List, 2009). The claim that human behavior and institutions are not reducible to biological sciences is true insofar as we narrow biology to genetic studies or similar micro-level processes. But political institutions are emergent phenomena, have their own laws, and require their own sciences, just as the science of complexity is not reducible to molecular physics (Taagepera, 2008). Rather, unification posits that there be consistency between micro- and macro-behavioral explanations. For example, models of political institutions and partisan competition should not assume that agents value the welfare of others more than their own, that men and women are equally prone to engage in extra-constitutional, violent confrontation, or that conventions of masculinity and feminism have no biological roots. An even broader challenge, the levels of selection controversy over the relative importance of kin selection and reciprocity versus group selection, has animated all of evolutionary science, and might benefit from better incorporation of institutional theory. As already discussed, political institutions that mobilize, aggregate, synthesize, and select competing policy strategies provide a clear Darwinian process with which to study levels of selection, and the potential to trace return benefits and other return effects across generations.



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9 Evolutionary Psychology and Crime Joseph L. Nedelec

INTRODUCTION As examined throughout this volume, humans are a highly social species and as such possess a constellation of adaptations which aid in survival and reproduction. Among the evolved strategies employed by highly social species, those which can be viewed as exploitative are abundant. Indeed, nature is awash with examples of evolved strategies that appear to callously infringe on the desires or choices of individuals who are the targets of such strategies. To be sure, highly social species rely on cooperation, empathy, and stable group dynamics, but all these factors can also be exploited for individual gain as an effective evolved strategy. When viewed from an evolutionary perspective, criminal behavior among humans clearly falls into an exploitative-strategy category. However, the field of social science devoted to the study of criminal and antisocial behavior, criminology, rarely examines behavior using an evolutionary lens. Instead, almost all traditional criminological theories and

empirical analyses place the etiological responsibility for antisocial behavior solely within the realm of social factors. Recently, however, biosocial criminologists have illustrated the shortcomings of such an approach. The current chapter overviews the various ways in which an evolutionary viewpoint can inform our understanding of antisocial behavior, crime, and criminality. Increasingly referred to as evolutionary criminology, the perspective described in this chapter illustrates how viewing antisocial behavior from an evolutionary standpoint can explain the most well-established observations regarding criminality as well as contextualize more recent empirical findings derived from neuropsychology, behavioral genetics, and biosocial criminology.

UNDERSTANDING AND USING EVOLUTIONARY THEORY Although covered elsewhere in this volume, it is necessary at the outset of our discussion to


address why many people within social-­ science disciplines struggle with recognizing the relevance of an evolutionary point of view. Perhaps the two most important concepts related to evolutionary thinking that can help in this regard are deep time and recognizing that humans are not immune to the processes of nature. Deep time is a geological concept that informed Charles Darwin in generating his theory of evolution by natural selection. Briefly, the concept refers to the immense amount of time that has passed since the formation of the earth and the amount of time that has been available for natural processes such as erosion, movement of the earth’s crust, and most germane to the current chapter, evolution of biological organisms. Given that humans typically live for only a handful of decades, our perceptions of the passage of time are drastically limited compared to the age of the earth. Consequently, it is difficult for most people to understand how the complexities we observe in nature and our own behaviors could result from the processes of evolution. Other factors such as religious dogma and cultural characteristics also impinge on people’s ability to recognize the immensity of time that has passed and the vast opportunities that have been provided for the processes of natural and sexual selection to shape the evolution of species. When one recognizes and accepts the overwhelming evidence of deep time, however, it becomes easier to see how natural processes could apply to all aspects of species’ lives, including behavioral traits such as crime and antisocial conduct. Given the time frames associated with the typical human life course, deep time is often cognitively taxing. However, observing natural wonders like the Grand Canyon provides an opportunity to witness the results of deep time. Recognizing that humans are a part of nature, however, is often less widely accepted. Given the complexities and varieties of human culture and the incredible technological and societal advances that humans


have made, along with the wide array of religious beliefs that have and continue to ­ profess human exceptionalism, it is not surprising that many feel humans are separate from the natural world – and, therefore, immune to the processes of natural and sexual selection that have shaped all life. Acceptance of human’s place in nature is, and has been since well before Darwin, a controversial issue. Nonetheless, the evidence that humans are a part of nature is as overwhelming as the evidence for deep time. Empirical facts such as homology (shared structures across different species or taxa), genetic code illustrating relatedness across animals and plants, and the considerable fossil record, among other empirical facts, all point to an inevitable conclusion: humans are not exceptional in terms of our place in nature and are the result of natural processes (i.e., natural and sexual selection) in the same way as all life on earth. Once this fact is acknowledged, and in combination with the concept of deep time, it is thus necessary that assessments of the causes of almost any aspect of the human condition must incorporate recognition of the evolutionary processes that underpin the human condition. Such a conclusion was emphasized by Pierre Teilhard de Chardin who poignantly noted, “[evolution] is a general postulate to which all theories, all hypotheses, all systems must henceforward bow and which they must satisfy in order to be thinkable and true. Evolution is a light which illuminates all facts, a trajectory which all lines of thought must follow”. (As cited in Dobzhansky, 1973: 129.) All this information inexorably leads to the perspective that informs the chapters within this volume. Briefly, evolutionary psychology argues that our brain is the seat of all human behavior and the construction and functioning of our brain is driven, in part, by genetic factors; these genetic factors, in turn, have been susceptible to the processes of natural and sexual selection over the vast eons of evolutionary time. Consequently, all aspects of the human condition, including human behavior, society, and culture,



can be assessed using an evolutionary lens. Given that criminal and antisocial behaviors are an empirical universal across all recorded history and across every known society, it is clear that an evolutionary lens can also illuminate why such behaviors appear to be an integral, though often unfortunate, aspect of the human condition.

OF CRIME, CRIMINALITY, AND ANTISOCIAL BEHAVIOR A common reaction in the social sciences to the suggestion of the utility of an evolutionary perspective is that, given behaviors considered to be criminal are based on codified laws, crime is a social construct that will vary from society to society. Thus, a biologically based perspective such as evolutionary psychology cannot inform the discussion of crime. The argument, though partially correct (codified prohibitions on certain behaviors certainly do change both within and between societies over time), is incomplete in at least two ways. First, across all recorded history and known societies there is considerable overlap in terms of prohibited behaviors. Few cultures accept behaviors such as thievery, murder, assault, or rape (this list is not exhaustive) without any social rebuke. Even within highly violent cultures where the murder of one group’s rivals is seen as a necessary step in the maturity of males, such behavior is condoned only if it is directed at an out-group. Consequently, there appears to be a human constant against the impingement of the rights and desires of others in terms of these behaviors (at least in terms of one’s own in-group). Second, while it is certainly the case that codified prohibitions (i.e., legal definitions of what constitutes crime) are fluid across time and space, the behavioral proclivities that underlie criminal or antisocial behavior are consistent. These proclivities are referred to, in general, as criminality, which is a propensity or inclination to engage

in criminal or antisocial behaviors. Thus, when biosocial criminologists examine criminal or antisocial behaviors using an evolutionary lens, it is with the concept of criminality in mind; in other words, the focus is on the behavior and not necessarily the legality of the behavior. As an example, criminologists examine not only antisocial behaviors that are illegal but also behaviors that are considered analogous to criminal behavior such as substance abuse or risky sexual behaviors and the lifestyles associated or congruent with engaging in antisocial conduct. Thus, recognizing that antisocial behaviors are acts which violate the interests of one party to the benefit of another party in contravention of normative behaviors of the group to which the parties belong allows for a more nuanced examination of the etiology of antisocial behavior than simply relying on legal definitions. Thinking in this way (i.e., focus on the behavior – criminality) provides an opportunity to apply an evolutionary lens. In the sections that follow, I outline how evolutionary psychology as a paradigm can help explain three of criminology’s most commonly observed empirical patterns in terms of antisocial behavior: the gender gap in crime, the age-graded distribution of crime, and the non-random distribution of criminal behavior.

THE GENDER GAP IN CRIME Imagine, if you will, a risk factor associated with criminality and antisocial behavior that is so pervasive that it replicates across all known societies and all recorded history. That risk factor is actually well-known, and in our species, it is represented by a lone chromosome: the Y-chromosome. Sex is the single most consistent predictor of criminal behavior that has emerged from well over a century of criminological theorizing and empirical work. To be sure, not all men engage in criminal behavior and not all women refrain from it. However, in the


statistical sense (i.e., average differences), there has not existed a society wherein women engaged in a higher rate of criminal behavior than men, and this is particularly the case with violent antisocial behaviors. The robust observed differences in terms of criminality between the sexes has been addressed in a variety of ways in the criminological literature with almost all explanations focusing on sociological factors (e.g., differential parental socialization, cultural factors, differential media exposure, etc.). In each case, these explanations have proven to be at best incomplete and at worst incorrect. A potential reason for the ineffective explanations is the lack of recognition that humans are part of the natural world. Here we see that an evolutionary perspective can illuminate potential causal factors for the observed differences in antisocial behaviors between men and women. When one recognizes that humans are a part of nature, one can then look to nature for potential analogues of the behavior or dynamic of interest. Additionally, an evolutionary perspective allows for the application of well-known biological theories or processes. For example, biological explanations of the differences in behavioral repertoires between the sexes within many species are often informed by discussions of investment (Trivers, 1972). Briefly, any given organism within a sexually reproducing species can allot time and energy to obtaining mates (mating effort) or caring for offspring (parental effort or investment). Bioenergetic resources cannot be allotted to both mating and parenting simultaneously and, as we shall see, the evolved strategies of sexes with regard to investment of resources are often divergent. Throughout the animal kingdom, the primary driver of differentiation in bioenergetic resources is referred to as minimal parental investment (MPI). MPI refers to the minimal time and energy costs associated with producing a viable offspring (i.e., one that can live long enough to then also reproduce). In most primate species (human and non-human), the MPI for males and females


differs considerably. While females in most primate species have a very high MPI (many months of gestation and often many years of offspring care), males have a relatively low MPI (perhaps as minimal as a few moments of copulation). Consequently, males can reproduce at much higher rates and with shorter intervals than females. While males have a much higher reproductive ceiling, they also evince much more variance in terms of reproductive success – the proportion of males who never reproduce is much higher than in females. Additionally, given that females risk a much higher MPI, they exhibit mating strategies that lead to what is generally referred to as choosiness (females assess males on their reproductive quality to a much higher degree than males assess females). The result of this difference in MPI is that males tend to differentially invest in mating effort while females tend to invest relatively more in parenting effort. Along with this differential allocation of resources comes a suite of behavioral strategies which affect the level and degree of competition both within and between sexes. Differential allocation of reproductive resources driven by MPI and within-sex variances in reproductive success is associated with more intense within-sex competition in the sex with the lower MPI. In less technical language, the sex with more to lose (i.e., greater reproductive variance – if you don’t reproduce, you’re a genetic dead end) is the sex that will engage in more intense (i.e., risky, violent, combative) competition relative to the sex with higher MPI. Thus, the biological concept of MPI provides the logic for understanding the wide range of morphological and behavioral traits that males possess, relative to females, which appear specifically designed for intense competition. The same morphological and behavioral traits related to within-sex competition (i.e., fighting rivals for access to the high MPI sex) are also employed for between-sex competition (e.g., subduing the ability of the high MPI sex to choose among mates).



While in most primate species males compete in a more intense fashion, there is nothing about maleness per se that inevitably leads to increased violence and aggression; likewise, there is nothing about femaleness per se that inevitably leads to decreased violence and aggression in within- and between-sex competition. To illustrate this argument, one can again observe nature for instances wherein the sexes converge in terms of MPI (i.e., greater amount of shared parental efforts, aka biparental care). Many species exhibit such patterns (e.g., wolves, numerous types of birds, beavers, some monkeys, among others), and the morphological and behavioral differences between males and females are greatly reduced. Perhaps the greatest evidence for the importance of MPI can be derived from species where the males invest more resources to parental effort relative to females and females have greater reproductive variance relative to males. This occurs in varieties of fish and other animals (though no mammals) and what is observed is a role reversal – relative to most primates – in terms of behavioral strategies: the females compete with more aggression and the males are generally choosier in terms of selecting mates. Armed with an evolutionary explanation of sex differences in terms of aggressive behavior, one can then see why men and women in our own species have exhibited and still do exhibit differences in terms of criminality or a propensity to engage in antisocial behaviors. Given that men possess a much lower MPI than women, it is men who possess (on average) greater muscle mass, height, and other morphological traits conducive to intense competition. Additionally, it is also the reason why men possess a suite of psychological traits that drive risky and aggressive behaviors more often and in typically more intense degrees than women. Consequently, in possession of the psychological drive and morphological capacities to aggressively compete, men are more often the sex to engage in criminal behaviors

(particularly those which are considered interpersonal and violent). Hence, one of the most robust empirical findings of criminological research: the gender gap in crime.1

AGE-GRADED DISTRIBUTION OF CRIME In addition to the gender gap in crime, researchers of human antisocial behavior have long observed that criminal activity, in general, tends to rise with the onset of adolescence, peak near the end of adolescence, and then abruptly plummet in young adulthood. This empirical pattern has been dubbed the age-crime curve and, like the gender gap in crime, has appeared relatively consistent across time and space.2 Numerous scholars have put forth theoretical explanations for this patterned empirical observation, the most well-known among criminologists being Laub and Sampson’s (1993) agegraded theory of crime and Moffitt’s (1993) dual taxonomic theory of crime. Briefly, Laub and Sampson’s (1993) theory asserts that informal social control through an individual’s bond to society affects the propensity to engage in criminal behavior over the life course. The theory places great weight on the bonds within an individual’s family during development as well as attachment to school, employment, and other structural aspects of society. Overall, Laub and Sampson argue that those youth with weak social bonds are more likely to engage in antisocial behaviors during adolescence and that such behavior in turn leads to an increased likelihood of criminal behavior in adulthood. Further, they argue that without social bonding or attachment to institutions such as employment, military service, and marriage, continued criminal behavior during adulthood is probable. Finally, they argue that desistence from criminal behavior is largely due to obtaining attachment to one or more of these social institutions.


Moffitt’s (1993) dual taxonomic theory also recognizes the importance of a life-course approach and contains a multitude of hypotheses regarding the shape of the age-crime curve. In brief, Moffitt argued that antisocial behavioral patterns illustrate two distinct groups of offenders: adolescent-limited offenders (AL) and life-course persistent offenders (LCP).3 As suggested by the label, those exhibiting AL patterns of offending engage in criminal behavior that is limited to the period of adolescence, that was not preceded by antisocial behavior in childhood, and does not tend to continue into adulthood. Additionally, the type of offending in which AL offenders engage is typically relatively minor and rarely results in serious contact with the criminal justice system (i.e., long-term institutionalization). LCP offenders, however, exhibit behavioral patterns illustrating a lifetime of antisocial behavior from childhood through adulthood. Additionally, relative to AL offenders, the type of criminal activity in which LCP offenders engage is often severe and does typically lead to serious and consistent interaction with the criminal justice system (throughout the life course). In terms of etiological factors, Moffitt (1993) argued that the behavioral pattern of LCP offenders is a result of an unfortunate mix of neuropsychological deficits and deleterious rearing environments. She argued that LCP offending patterns are so serious in nature and consistency that exceedingly damaging circumstances such as abnormal neuropsychological functioning and abusive or otherwise damaging developmental environments were required. However, given that Moffitt argued that AL offending was normative (i.e., an expected pattern of development in modern societies), her explanation required normative processes typically experienced by most youth. Her hypotheses regarding AL offending centered on two components. The first component is represented by the difference between the biological maturity experienced by youth in adolescence (after puberty an individual is, more or less, biologically an


adult) and the social limitations that remain in place in modern societies (adolescence is a period of relaxed limitations relative to childhood, but it still consists of wide-­ ranging restrictions on a variety of aspects of life). The difference between one’s biological maturity and one’s perceptions of social freedom/limitation was termed the maturity gap. Moffitt argued that the greater the experienced maturity gap, the greater the frustration experienced by the youth and therefore the greater the need to address the resulting frustration. The second component of Moffitt’s explanation of AL offending provides the mechanism through which youth were said to then deal with the frustration resulting from an experienced maturity gap. Her argument indicated that AL individuals could recognize/observe the relative social freedom exhibited by those who are engaged in LCP offending and lifestyle patterns. Observing the socially uninhibited lifestyle of LCP offenders could then lead to a process of behavioral mimicry in order to gain similar social freedoms (termed social mimicry). Moffitt thus argued that AL offending was a result of experiencing a maturity gap during adolescence and engaging in social mimicry such that the behavioral patterns of LCP offenders are followed (although to a less serious degree) by non-LCP youth (i.e., AL offenders). Further, Moffitt argued that the desistance from criminal behavior observed during early adulthood by AL offenders was a result of the reduced effect of the maturity gap (i.e., the social limitations placed on adolescents become much less intense or pervasive as they age into early adulthood) – thus, with the accumulation of greater social freedoms throughout many aspects of their lives, those in the AL offending group no longer experience the frustrations associated with social limitations which eliminates the need to mimic the behavioral patterns of LCP offenders. Both the age-graded and dual taxonomic theories of crime have received substantial attention in the criminological literature and



researchers continue to test the hypotheses derived from both theories. For the purposes of this chapter, however, it is important to note that both theories are proximal theories of criminal behavior (as exhibited in the age-crime curve). As discussed throughout this volume, proximal explanations of behavior refer to those arguments that focus on factors related primarily to ontogeny (i.e., development within an individual’s lifespan), whereas evolutionary arguments provide ultimate explanations of behavior, which focus on phylogeny (development over generations rather than within a single lifespan) and adaptive function (i.e., what adaptive problem is addressed by the behavior in question?). For example, while it may be the case that informal social bonds affect crime over the life course or that the frustration associated with experiencing the maturity gap leads to increased antisocial behavior in adolescence, we are still left with the question as to why these processes have the (potential) effect that is purported. Why should social bonds experienced during development and in adulthood affect behavioral patterns? Why should biological maturity combined with limitations on social freedoms lead to frustration among youth? Why would aggressive or violent behavior be something in which youth engage to deal with the frustration? Fortunately, an evolutionary perspective can provide the ultimate reasons/answers to such questions. As with the discussion of the gender gap in crime, an evolutionary explanation of the age-crime curve centers on variance in reproductive effort between men and women. A few examples of evolutionary explanations for the age-crime curve exist in the literature (e.g., Quinsey et al., 2004) but they all center on what Wilson and Daly (1985) termed the young male syndrome. Briefly, Wilson and Daly argue that given the immense costs of reproductive failure (i.e., genetic dead end) and the substantial variance in reproductive fitness among men, there will be intense competition for any resources that help increase

reproductive ­fitness. In this zero-sum social contest, higher-ranking men tend to obtain more mates and increase their reproductive fitness, whereas lower-ranking men have fewer or no mates. Given that social rank is a vital component to reproductive fitness for men, there is a heightened psychological awareness among men to threats to status or reputation (often referred to as honor). Threats to social status or reputation are, in essence, threats to social rank and, thus, threats to reproductive potential. Consequently, intense, aggressive, and often violent competition to maintain or advance rank can occur when such threats arise. Further, within a polygymous breeding system wherein some males reproduce much more than most males there are numerous reproductive benefits to intense (aggressive, risky) competition. Such behavior can serve to protect or gain status, discourage or eliminate rival males in a competitive breeding environment, allow for the acquisition of resources to be used to woo females, engage in and protect from mate poaching, and protect already acquired resources and mates (including aggressive mate guarding). Wilson and Daly (1985) provide empirical evidence supporting these assertions based on data from over 500 homicide cases in Detroit in the early 1970s. They illustrate that not only were the majority of both offenders and victims in homicide cases men, but offenders and victims were almost identical in terms of being unemployed, unmarried, and younger (teen years to mid 20s). Analysis of the cases also indicated that the most common type of homicide was the result of social conflict or what criminologists would refer to as the escalation of a trivial altercation (the majority of which were primarily in retaliation for a previous loss of face in the presence of social peers). Summarizing their observations regarding lethal conflict, they note, ‘many, perhaps most, homicides concern status competition’ (Wilson and Daly, 1985: 59). Wilson and Daly also illustrated that other behaviors that carry a substantive threat of physical harm (e.g., risky and/or


aggressive driving) are likely the result of a generalized willingness to engage in competitive risk taking relevant to social rank and, thus, linked to male fitness. The observations and hypotheses put forth by Wilson and Daly have been further supported using data outside of Detroit and for different time periods (see Daly, 2016; Daly and Wilson, 2017). Although Wilson and Daly (1985) outline why engagement in criminal conduct and other risky behaviors increases during the adolescent years, their discussion does not explicitly focus on the entirety of the agecrime curve. In their theoretical piece on male criminality over the life course, Kanazawa and Still (2000) echo Wilson and Daly’s young male syndrome hypothesis but also directly address the shape of the age-crime curve. Overall, Kanazawa and Still indicate that intense competition (manifested as antisocial, aggressive, and other risky behaviors) occurs when the reproductive benefits of such behavior are maximized over the life course. Thus, violent competition among males does not occur earlier in life (i.e., prior to puberty) primarily because there are no reproductive benefits to engaging in violence, theft, or murder – the pre-pubescent male is unable to translate a competitive edge into reproductive success. However, after puberty the reproductive benefits sky-rocket and so too does the resulting behavior (thus, the peak in adolescence of the age-crime curve). As noted above, however, the age-crime curve drops precipitously in early adulthood. Kanazawa and Still argued that the ultimate reason for this drop is associated with the costs of continued intense competition. The authors argue that risky strategies are employed to gain sexual access to mates and, in general, secure reproductive success (or at least the opportunity for reproductive success) and at the arrival of offspring (i.e., reproductive success) less risky behavior is employed to minimize the costs to the reproductive success of the male. Thus, the age-crime curve (for males) is a manifestation of a two-pronged strategy selected over evolutionary time


wherein males engage in intense competition in order to secure reproductive success, but once this is secured tend to disengage from risky behavioral strategies given the potential costs to the obtained reproductive success. The ultimate explanations put forth by Wilson and Daly (1985) and Kanazawa and Still (2000) are supported by proximal explanations derived from psychophysiological and criminological research. For example, the hormone testosterone – which has been associated primarily with competitive behaviors – increases dramatically in males during puberty but has been observed to drop substantially at the onset of marriage and the arrival of offspring (Beaver, 2009). Additionally, some criminological research has illustrated a calming effect in males (in terms of engagement in criminal behavior) who begin families, though this research is often confounded by issues of temporal order and a lack of genetically informed analyses (Barnes et al., 2014). Finally, we see that these evolutionary explanations of the age-crime curve provide some potential answers to our earlier questions derived from the discussion of the age-graded and dual taxonomic theories of crime. For example, informal social bonds such as employment, military service, and marriage could affect male criminality as these are resources which directly affect or relate to reproductive success. Given that criminal behavior, especially violent or aggressive behavior, represents a threat to these resources there is a corresponding reduction in the level of criminal behavior (on average) that is congruent with the acquisition of these resources. Additionally, experiencing the maturity gap results in increased frustration in youth because their biological maturity – driven by eons of evolutionary processes – motivates them to engage in intra- and inter-sexual competition to obtain mates. However, the wide-ranging social limitations placed on adolescents prevent or at least minimize opportunities for such behaviors. Thus, social rebellion through minor delinquency could result (not only to rebel



against the social restraints but to attempt to secure status and rank within a peer network). Overall, the discussion illustrates what all evolutionary psychologists argue: both proximal and ultimate explanations are required in order to fully understand observed behavioral patterns such as the age-crime curve.

NON-RANDOM DISTRIBUTION OF CRIMINAL BEHAVIOR The final consistent criminological empirical observation that we will address in the current chapter is the non-random distribution of criminal behavior. In addition to the gender gap and age-crime curve, long-standing and cross-cultural patterns in terms of where criminal conduct tends to occur geospatially and the typical dynamics of offender–victim relationships have been observed. Entire subfields within criminology, for example, have developed which center specifically on these observations. For example, the Chicago school of criminology, most readily exemplified by the work of Shaw and McKay (1942), focused on the differential patterns of criminal behaviors across different areas (or zones) within a city. The authors argued that the differential offending patterns were a result of variance in the structural conditions (e.g., economic status, ethnic heterogeneity, and residential mobility) found in the zones. Further, socioeconomic status and aspects of neighborhood cohesion (sometimes referred to as collective efficacy; Sampson et al., 1997) have long been assessed as key causal variables in the etiology of crime and criminality. Additionally, criminologists and other social scientists have also been examining the nature of victim–offender relationships for well over a century. Consequently, much is known about the ways in which criminal behavior is distributed in terms of geospatial location within cities and towns as well as how offenders and victims are (or are not) known or connected. Overall, in both cases there is a

non-random distribution of criminal conduct although the pattern of the conduct typically depends upon the specific type of crime. The remaining discussion within this section will illustrate how an evolutionary perspective can help explain these non-random patterns.

Non-Random Clustering of Criminality and Other Risky Behaviors in Locales As noted, criminologists have observed that criminal conduct tends to be over-represented or differentially concentrated within certain areas of a city or town. Typically, the areas of concentration are considered to represent highly unstable environments characterized by low average economic status and relatively low social cohesion. Social scientists have tended to point to these characteristics as the causal factors in the accompanying concentration of criminal conduct while others have noted that the criminal behavior exhibited in such areas is a result of a sub-culture of recklessness resulting from minimal opportunity for social advancement. However, as discussed in the prior section these types of explanations are incomplete – why would criminal behavior, especially violent behavior, result from reduced social and economic opportunity? Why would criminal behavior exhibit concentrations among communities with a relative lack of social cohesion or stability? In their analysis of 77 different neighborhoods in Chicago using data from 1988 to 1993, Wilson and Daly (1997) illustrated that an evolutionary perspective can help to address such questions (see also Daly, 2016). Briefly, Wilson and Daly (1997) examined the differential life expectancy for men and women across various neighborhoods, as well as homicide rates, birth rates, and measures of socioeconomic status (i.e., household income and an income inequality index). The key independent variable, life expectancy, was a measure of the expected average duration of life, in years, for an individual based on a variety


of vital statistics and population data present at the time of the individual’s birth. In their analyses Wilson and Daly empirically assessed three specific hypotheses: (1) homicide rates are a function of local life expectancy; (2) economic inequality accounts for variance in homicide rates beyond that attributed to local life expectancy; and (3) local life expectancy will impact reproduction (birth rates) across neighborhoods. Overall, the researchers argued that life expectancy provides a vital external cue to inhabitants of neighborhoods such that their unconscious behavioral and reproductive strategies can be adjusted based on an assessment of probable lifespan. Thus, rather than representing a potential pathological reaction to social conditions, high-crime areas may be a function of a rational calculation (though one that has been honed over evolutionary time) based on environmental cues. The analyses testing these ideas revealed a number of illuminating findings. First, life expectancy at birth was strongly associated with homicide rates across neighborhoods for both men and women. In neighborhoods with a lower life expectancy at birth a much higher homicide rate was observed. The magnitudes of the bivariate associations were very strong and statistically significant for both men (r = −0.88, p < .0001) and women (r = −0.83, p < .0001). Importantly, these associations held in multivariate models wherein measures for household income and income inequality were introduced. Second, comparisons between the 10 neighborhoods with the longest life expectancy and the 10 neighborhoods with the shortest life expectancy revealed some drastic differences in terms of homicide rates across age categories. For example, in the long life expectancy neighborhoods the homicide rate (deaths per 100,000 per year) went from virtually zero for those males aged five to 14 years to about 20/100,000 for those aged 15 to 24, to a peak of about 25/100,000 for those aged 25 to 34 before dropping to near zero for the remaining age groups. However, in the short life expectancy neighborhoods


the homicide rate skyrocketed from about 5/100,000 in the five to 14 years age group to over 300 deaths per 100,000 for the males in the 15 to 24 years age group. While the homicide rate for males in these neighborhoods decreased over time, the rates were still astronomically higher than those observed in the long life expectancy neighborhoods (25 to 34 years: about 250/100,000; 35 to 44 years: about 175/100,000; 45 to 54 years: about 75/100,000; 55 to 64 years: about 60/100,000; 65 to 74 years: about 40/100,000; and 75 years or older: about 55/100,000). While the homicide rates for females in the short life expectancy neighborhoods were much lower than for males, the overall pattern across the age groups was similar and, in some cases, exceeded the homicide rates for males in the long life expectancy neighborhoods. Finally, in terms of reproductive behaviors Wilson and Daly (1997) again compared the 10 neighborhoods with the longest life expectancy to the 10 neighborhoods with the shortest life expectancy across seven different age categories. The differences in birth rates during the teen years and early adulthood between the neighborhoods was substantial. Figure 9.1 illustrates the stark differences. As illustrated, the birth rate for women in the short life expectancy neighborhoods was over four times higher than the long life expectancy neighborhoods for the 15 to 19 years age group, and two-and-a-half times greater in the 20 to 24 years age group. Additionally, although the difference is still evident in the 25 to 29 years age group, the birth rates for the different neighborhoods become almost identical in the remaining age categories (i.e., 30 years and above). Based on the results of their analyses, Wilson and Daly concluded: [t]he data presented here indicate that people behave as if they have adjusted their rates of future discounting and risk acceptance thresholds in relation to local life expectancy, and that they do so in the non-violent domain of reproductive decision making as well as in the potentially violent domain of social competition. (Wilson and Daly, 1997: 1273)



Figure 9.1  Age-specific birth rates (per 1,000 women per year) in the 10 neighborhoods with the longest life expectancy compared to the 10 neighborhoods with the shortest life expectancy Source: Data derived from table 3 in Wilson and Daly (1997).

The analyses and conclusion presented by Wilson and Daly (1997) illustrate how an evolutionary lens can help explain social phenomena that have hitherto only been addressed employing sociologically based theories. Furthermore, they illustrate that the behavioral repertoire exhibited by individuals presented with certain environmental cues may not be pathological or reckless, but rather a function of an unconscious calculus resulting from eons of evolutionary processes. The next example provides a similar illustration in terms of observed patterns of victim–offender characteristics.

Non-Random Victim–Offender Characteristics Depending on the criminal behavior of interest, criminologists have observed that characteristics are consistently represented in terms of victims and offenders. In general,

both victims and offenders tend to be in their adolescence or early adulthood. This observation is not entirely surprising given the age-crime curve, which manifests as a result of the intense mating competition experienced during that period in the life course. However, examinations of specific criminal behaviors have illustrated other patterns in terms of characteristics. For example, researchers estimate that in North America on average approximately 65% of all murders involve a male offender and a male victim, about 20% involve a male offender and a female victim, about 10% involve a female offender and a male victim, and less than 5% involve a female offender and a female victim (Buss, 2005; Daly and Wilson, 2017). Additionally, the risk of being a homicide victim (in general) increases considerably during late adolescence, peaks in the early 20s, and then drops substantially over adulthood. The overall pattern of homicide and other aggressive behaviors in terms of


offender–victim characteristics has been addressed by a wide range of criminological inquiries. Most of the examinations, however, have focused solely on proximate factors such as socialization practices or even media consumption to account for the observed patterns. As noted earlier, a substantial problem for such explanations is that the patterns observed in terms of offender– victim characteristics are relatively consistent across time and space. Thus, explanations which rely on variance in societal factors such as socialization practices are doomed to be incomplete. Fortunately, researchers employing an evolutionary lens have provided potential explanations for the observed patterns of offender characteristics exhibited in several crimes, including homicide. In their book entitled Homicide: Foundations of human behavior, Daly and Wilson (2017) expand upon their 1985 paper and provide a thorough examination of how an evolutionary viewpoint can help explain the characteristics of offenders and of victims for various types of homicides. Their discussion centers on intrasexual competition among young males who are psychologically attuned to threats to status and again apply the young male syndrome logic to socially competitive risky behaviors. Daly and Wilson provide a wellspring of empirical analyses from multiple countries to support their claims, and their coverage of the topic is thorough. However, as valuable as Daly and Wilson’s book is – and it is certainly a definitive discussion of how an evolutionary viewpoint can be applied to murder – we will focus our discussion in this section instead on a book by David Buss (2005). Buss’s (2005) book, entitled The Murderer Next Door: Why the Mind is Designed to Kill, presents the argument that homicidal behavioral patterns may have been selected for over evolutionary time as a potential strategy for dealing with a variety of adaptive problems. The claim that killing is produced by a specific psychological adaptation is a controversial one and discussing the merits


of the argument is beyond the scope of the current chapter. However, the data on which Buss based his conclusion and the evolutionary arguments are worth considering herein. In addition to examining a large amount of behavioral data similar to that presented in Daly and Wilson’s (2017) book (i.e., official criminal justice records), Buss and his team also collected data on homicidal ideations (fantasies) from a sample of over 5,000 individuals across a number of age categories from multiple countries. The respondents in the study were asked if they had ever thought of killing someone, who it was (in terms of the relationship to the respondent), the manner in which they thought of killing the target, what prevented them from going through with the killing, and what could have potentially led them to actually kill (i.e., push them over the edge). The respondents were also asked if they ever thought someone might kill them and were also presented similar followup questions (i.e., who they thought may have wanted to kill them, how they might have been killed, what the respondent did to prevent being killed, what prevented them from being killed, and what would have pushed the person over the edge to kill the respondent). The results of the survey revealed several illuminating patterns that aligned with evolutionary theory (only a handful of which are included here). First, a considerable majority of the respondents in the sample indicated that they had given thought to killing. Buss and his team of researchers observed that 91% of the men in the sample and 84% of the women reported at least one vivid fantasy about killing someone. Buss argued that this finding supports the argument that over evolutionary time murder may have been an effective strategy to employ when faced with a serious adaptive problem. Second, both men and women in the study exhibited consistent yet distinct patterns of homicidal ideations. While both sexes reported homicidal fantasies related to sexual rivalries (e.g., killing the new sexual/romantic partner



or a former partner), men tended to focus on issues centered on mate retention (i.e., infidelity, actual or perceived, by their current or former partner) whereas women tended to focus on threats by other women to their own mate quality (e.g., responding to rumors about their own sexual reputation) and on responding to perceived or actual abusive threats by current or former partners. Buss notes that given the substantial threat to reproductive success in these circumstances intense counter-measures, such as violent action, were likely selected for over evolutionary time. Third, related to the general patterns of men and women’s homicidal ideations the researchers also noted that men generally reported homicidal ideations focused on sexual (rather than emotional) infidelity, whereas when women mentioned infidelity of a current or former partner in a homicidal fantasy it was more often related to emotional (rather than sexual) infidelity. The general differences observed in the reported homicidal fantasies in this regard also belie the differential threats to reproductive success for the sexes. As outlined above, given that women are the high-MPI sex in our species sexual access is a resource that is highly contested by men. Thus, any aspects of the social environment which affects the likelihood of securing such a resource will be met with severe reaction. Likewise, while women are typically the choosier sex in terms of sexual access they are, as a result of being the high-MPI sex, more burdened by potential and actual offspring than are men. Thus, over evolutionary time psychological modules guiding women’s mate choice have been tuned to cues in potential mates that indicate a willingness to invest in the long term (i.e., help to raise any future offspring). One such cue is the extent to which a mate professes and exhibits emotional attachment. Consequently, Buss and his team argue, many of the women in the study centered their homicidal fantasies on situations wherein the respondent actually had, or perceived an experience of, emotional infidelity.

Fourth, in terms of the thoughts related to being a victim of homicide, Buss and his team also noted some general patterns that were consistent within and between sexes. For instance, both men and women consistently indicated that they thought they would be the victim of murder given that they had engaged in or came close to what evolutionary psychologists generally call mate poaching. In essence, the process refers to a sexual or romantic partnership with another mate who is already involved in a relationship. As noted above, being the actual or perceived victim of mate poaching was consistently evident in the fantasies of those who reported wanting to kill. Additionally, across most known societies and recorded time periods such behavior is associated with enraged emotion and what is typically termed irrational behavior (though from an evolutionary point of view, acting to minimize threats to one’s reproductive status may actually be rational; see Daly, 2016). Indeed, the legal codes of many societies include provisions for reduced punishment or even culpability in cases where a spouse murders a mate poacher. Thus, all parties involved in the matepoaching situation are aware of the potential risks and the respondents who reported feared homicidal victimization in Buss’s study certainly echoed such awareness. In terms of some of the general differences between the sexes regarding the reports of being a potential murder victim, the primary variance mirrored that observed in the fantasies associated with committing a homicide. For example, men generally reported a fear of homicidal victimization that resulted from not only mate poaching but also from threats to other men regarding the target’s (i.e., the potential homicidal male) social rank, status, or worthiness as a sexual partner. Additionally, women generally reported a fear of victimization resulting from engaging in verbal denigration of the sexual reputation or physical appearance of other female rivals. Overall, the pattern illustrated in the ideations about homicidal victimization reflected a keen recognition of the type of social


circumstances that typically could drive others to kill. In line with evolutionary theory, Buss noted that this dynamic is a result of co-evolution of intense strategies related to maintaining or increasing one’s value in the highly competitive sexual reproduction market. Further, the findings are manifestations of the evolution of strategies related to prevent being a victim of such competition (and therefore also maintaining or increasing one’s mate value). Biologists and evolutionary psychologists refer to this process as the Red Queen hypothesis, and it is discussed in detail elsewhere in this volume. Overall, the data presented in Homicide and The Murderer Next Door align with the historical and contemporary data studied by criminologists and other social scientists. The patterns observed in terms of the crime-specific non-random distributions of victim–offender characteristics and relationships occur across these data. The differences, however, arise in the explanations that have been proffered to account for these observations. Whereas social scientists typically lay the blame on processes such as socialization, culture, and media exposure, evolutionary psychologists illustrate how such observations may actually be the result of our evolutionary heritage. Data presented by Buss and his research team indicate that the targets of offenses such as homicide may (in general) be particular and such particularity is due to the specific threat to reproductive success or survival (the key aspects of evolutionary processes) represented by the target. Understanding the victim–offender associations so often observed in criminological data in terms of ultimate causes provides an opportunity for greater clarity of etiology and therefore potential to increase our ability to reduce harm.

CONCLUSION The current chapter presented an overview of some of the ways in which an evolutionary view can be applied to crime, criminality,


and antisocial behavior. As noted in the introduction, given the social nature of our species, the exploitation of others for personal gain is an indelible and likely inevitable characteristic of the human condition. The inevitability of the characteristic, however, does not mean that our species need accept, condone, or encourage antisocial behaviors of any kind. As noted throughout this volume, nothing about the explanation of a behavior should be seen as a moral stance on the behavior. Additionally, just because antisocial, aggressive, and/or criminal behavior is in part due to the natural processes associated with evolution it does not mean that the behavior is justified or in any way excused by the knowledge of those processes (to think otherwise would be to commit the naturalistic fallacy). Rather, the stance taken in this chapter and elsewhere is that the best opportunity to reduce harm associated with criminal behavior must be derived from our best efforts to understand the underlying processes of criminality. While the social sciences have provided a wide variety of potentially useful proximal hypotheses in this regard, the application of an evolutionary perspective to criminal behavior provides the ultimate, and therefore likely most useful, understanding. As biosocial criminology advances within and beyond the discipline of criminology it is likely that our ability to address the harms associated with criminality will be enhanced. Employing an evolutionary lens will be a crucial component of that journey.

Notes 1  At the risk of being repetitive, it is key to note here that an evolutionary perspective does not dismiss the importance of cross-cultural diversity in terms of observed crime rates and potential additional etiological factors. Indeed, an evolutionary perspective is inherently biosocial such that it emphasizes the interactive processes between the inherited genetic architecture of the brain and the developmental environment to which an individual is exposed.



2  Deviations across a variety of societies have been noted, but some of these patterns of deviation are due to exceedingly rare socio-political events (e.g., aftermath of a world war and nuclear attack; Hiraiwa-Hasegawa, 2005). 3  Moffitt also suggested a third group, abstainers, who appear to not engage in any offending over the life course. While of much theoretical interest, our discussion will be limited to the two offending groups emphasized in her dual taxonomy.

REFERENCES Barnes, J. C., Wright, J. P., Boutwell, B. B., Schwartz, J. A., Connolly, E. J., Nedelec, J. L., & Beaver, K. M. (2014). Demonstrating the validity of twin research in criminology. Criminology, 52, 588–626. Beaver, K. M. (2009). Biosocial criminology: A primer. Dubuque: Kendall Hunt. Buss, D. M. (2005). The murderer next door: Why the mind is designed to kill. New York: Penguin. Daly, M. (2016). Killing the competition: Economic inequality and homicide. New York: Transaction Publishers. Daly, M., & Wilson, M. (2017). Homicide: Foundations of human behavior. New York: Routledge. Dobzhansky, T. (1973). Nothing in biology makes sense except in the light of evolution. The American Biology Teacher, 35, 125–129. Hiraiwa-Hasegawa, M. (2005). Homicide by men in Japan, and its relationship to age,

resources and risk taking. Evolution and Human Behavior, 26, 332–343. Kanazawa, S., & Still, M. C. (2000). Why men commit crimes (and why they desist). Sociological Theory, 18, 434–447. Laub, J. H., & Sampson, R. J. (1993). Turning points in the life course: Why change matters to the study of crime. Criminology, 31, 301–325. Moffitt, T. E. (1993). A developmental taxonomy. Psychological Review, 100, 674–701. Quinsey, V. L., Skilling, T. A., Lalumiere, M. L., & Craig, W. M. (2004). Juvenile delinquency: Understanding the origins of individual differences. Washington, DC: American Psychological Association. Sampson, R. J., Raudenbush, S. W., & Earls, F. (1997). Neighborhoods and violent crime: A multilevel study of collective efficacy. Science, 277, 918–924. Shaw, C. R., & McKay, H. D. (1942). Juvenile delinquency and urban areas. Chicago, IL: University of Chicago Press. Trivers, R. L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man, 1871–1971 (pp. 136–179). Chicago, IL: Aldine. Wilson, M., & Daly, M. (1985). Competitiveness, risk taking, and violence: The young male syndrome. Ethology and Sociobiology, 6, 59–73. Wilson, M., & Daly, M. (1997). Life expectancy, economic inequality, homicide, and reproductive timing in Chicago neighbourhoods. BMJ, 314, 1271–1274.

10 Evolutionary Psychology and Policing: The Balance Between Aggression and Restraint Lois James

INTRODUCTION Police professionalism and use of force are critical topics of public interest in the 21st century. Perhaps more than ever in the history of US policing, the public are demanding accountability and visibility of police behavior. Some researchers indicate that this intense microscope of scrutiny has led to decreased legitimacy and public faith in police, going so far as to label it a “legitimacy crisis” (Gest, 2016; James et al., 2016). Following high-profile shootings of unarmed African American men in recent years, starting with Michael Brown in Ferguson, Missouri, public trust in police dropped significantly, equaling the rates observed in the years following the Rodney King trials (Jones, 2015). Minority citizens reported less trust in the police than white citizens (Peck, 2015). Within any social system a certain degree of give and take is necessary, and historically the police have had some difficulty with yielding authority – for example,

enforcement of ‘stop and frisk’ practices, contributing to racial injustice and antipolice sentiment (White and Fradella, 2016). In the ‘post-Ferguson’ era, the policing profession is faced with nationwide calls for reform, and an understanding of how this professional group has evolved is essential for guiding its path forward (President’s Task Force on 21st Century Policing, 2015). The function of the police is tied to their granted authority to use force to ensure safety and order. Renowned sociology and policing scholar Egon Bittner (1970) identified the role of the police as the legitimate authority to exercise force. This is challenging because the exercising of this authority by the police frequently stirs accusations of brutality and racism, civil unrest, demands that officers be criminally punished, and at times mass violence and rioting. The goal of this chapter is to explore the police function and these contradictory social realities using evolutionary psychology. In order to maintain order and serve the citizenry the police must be



both aggressive and restrained. Maintaining a balance between aggression and restraint is required to promote and uphold social order. As society evolves, so does this balance (whereby the scale can tip more towards aggression or restraint depending on societal demands). Our society today expects greater restraint on the part of police, while police culture continues to promote aggressive authority. Aligning public and police expectations of the appropriate balance between aggression and restraint could promote legitimacy in all aspects of police work.

THE EVOLUTION OF AGGRESSION AND RESTRAINT Evolution is the process of change in all forms of life over generations. Each generation inherits traits, through genes, from their parents. If this new trait is heritable, and contributes to greater reproductive success of the organism relative to individuals without the trait, it will be passed on to the next generation and accumulate in the population (Buss and Shackelford, 1997). New traits that do not help the organism survive long enough to reproduce will become rare or disappear. This process of natural selection or ‘survival of the fittest’ has guided the evolution of aggressive and restrained behaviors over time. Although in social animals such as humans, aggression is not typically an indiscriminate strategy (Savage and Kanazawa, 2004), context-specific aggression is a naturally occurring, prevalent phenomenon (Neuberg et al., 2010). Restraint is the action that occurs when the ‘means to an end’ is reached, for example when the threat of an opponent is neutralized. It can also occur if one decides that the risks of employing aggression as a strategy are too great. For the most part, aggression and restraint are tightly linked. Buss and Shackelford (1997) identified seven social problems for which aggression

has evolved over generations as a ­beneficial response. These include the protection and acquisition of necessary resources, selfdefense against attack, inflicting costs on same-sex rivals who are vying for the same resources, gaining and maintaining power and dominance, deterring potential opponents from future attacks, ensuring the sexual fidelity of a partner, and reducing resource investment in unrelated children. For example, in a pack of wolves, the dominant member cannot show weakness in the face of a physical challenge or his dominant status will be questioned and potentially overturned (Millan, 2006). He must assert his dominance through aggression, or submit to a new leader (restraint). In this way, aggression evolved as a mechanism for demonstrating and protecting dominant social status. Examples of resource-acquisition-related aggression in humans include two men fighting over the attentions of an attractive woman, a homeless woman stabbing a wealthy-looking woman to steal her wallet, or a nation going to war with another over valuable natural resources. Restraint behavior should occur when the target of the aggressive behavior is subdued or neutralized. As important as aggression is, the failure to employ proper restraint can compromise one’s survival. Restraint occurs in nature when animals are faced with the submission of a challenger. For example, the roe deer buck will not clash antlers unless an opponent is face-on and engaged in the fight, although he could successfully attack when the opponent is turned around and vulnerable (Eibl-Eibesfeldt, 1961). Likewise, the defeated wolf will show his neck to his successful opponent, who refrains from killing him even though he could do so (Lorenz, 1952). Such restraint in the face of submission is used to safeguard one’s energy for future attacks – use of unnecessary energy can signal that one is vulnerable (Millan, 2006). Moreover, if a social animal fails to show proper restraint by either attacking others without good cause, being overly aggressive in their pursuit of submission from


others, or continuing an attack when their opponent is clearly defeated, that individual will be threatening to the social order and may be killed, exiled, or (in the human case) jailed or imprisoned (Francis, 1998).

THE CREATION OF THE POLICE PROFESSION AND THE SOCIAL CONTRACT BETWEEN THE POLICE AND THE CITIZENRY Evolution explains why using aggression as a means to an end may be necessary for survival, and how restraint in humans evolved as a means of tempering and controlling aggression, with the result that social order and the rule of law are preserved. Not all players are afforded equal power in the exercise of aggression in contemporary US society. The police (and other professionals in ascribed circumstances) are granted the right to exercise legitimate physical force if necessary to protect public safety. This can be explained by Social Contract Theory (SCT), which states that individuals’ moral obligations are shaped by a collective agreement or ‘social contract’ that binds a society together with a set of accepted norms and rules (such as the rule of law). This theory was given its first rigorous defense by Thomas Hobbes (1588–1679). John Locke (1632–1704) and Jean-Jacques Rousseau (1712–1778) are other champions of this theory. In fact, Locke’s argument that citizens have the right to revolt against authority should it no longer be protecting their interests was enormously influential on democratic revolution – notably for Thomas Jefferson and the founders of the United States. Revolt against perceived tyrannical rule or oppression has potential implications for the current police legitimacy crisis with the rise of social justice movements such as Black Lives Matter. Not all human societies are bound by a social contract. Reiman (1985) describes the


‘state of nature’ as a society without legal institutions. Although rare, a modern example of such a system is the Gebusi tribe of New Guinea – a highly cooperative, egalitarian, social society which is non-competitive and politically decentralized with interpersonal relations that are mutually respectful, nonhierarchical, and self-effacing. Aggression among the Gebusi people is discouraged, as antisocial behavior is contradictory to their peaceful values. Fear of violence is fostered and withdrawal from violence is reinforced. They also have a homicide rate among the highest reported. Between 1940 and 1982 nearly one-third of adult deaths were caused by homicide (Knauft et  al., 1987). This is the equivalent of a homicide rate of 568 per 100,000 per annum. To put this in perspective, the US homicide rate (one of the highest in the Western world) was roughly 6 per 100,000 per annum in 2018 (Federal Bureau of Investigation, 2018). The most common cause of homicide is ‘sorcery’, that is, an individual will be killed when they are believed to have caused death through sickness to someone else in the village. Given that the Gebusi live in the lowland rainforest of New Guinea, disease is rampant, explaining the ‘sickness deaths’ and consequent sorcerer killings. Homicide is considered a regrettable but unavoidable burden required to maintain the social system, and even the close kin members of the victim rarely seek retribution. Societies without legal institutions, even highly cooperative and peaceable tribes like the Gebusi, will inevitably require a great deal of interpersonal violence to prevent anarchy. Within most systems, the social contract between police and citizens is the collective antidote to the ‘state of nature’ Reiman describes. Individuals recognize that their right to use force may be countered by the rights of others to use force, and that the state of nature is inherently unsafe and unstable in the absence of a governing rule. As such, we sacrifice certain personal freedoms to increase safety at a broader level: ‘It becomes rational for



freedom-loving people to renounce their freedom to use force at their own discretion’ (Reiman, 1985: 239). But in order to do this, some society members must be responsible for maintaining public safety. We assign this duty to the police. In the mid 19th century, as the United States expanded through immigration and the industrial revolution, professional police forces were established in metropolitan cities and a social contract authorized police officers to protect individuals from victimization (Walker, 1977). Police officers were granted the authority to employ coercion to protect citizens’ lives and property (Reiman, 1985). Conceptualized in this way, the police became society’s ‘professional aggressors’, called upon when force was necessary (Bittner, 1970). The social contract establishes the right of police to utilize the force necessary, including deadly force, if the threat warrants it. For example, if a suspect is posing a deadly threat to innocent civilians the police are justified to shoot. In this case, aggression is not just allowed, but expected for the overall good of society. The role of restraint within the social contract is equally important. Citizens expect that police authority be utilized legitimately, competently, and in good faith (Reiman, 1985). Use of force by police must result in an overall increase in public safety. Despite a consistent emphasis on the function of the police being tied to the legitimate use of force, the major role of the police has evolved over time with the demands of the ruling elite. From preventing slave revolts in the mid 19th century, to maintaining segregation following emancipation, to riot enforcement during the civil rights movement, the police can be seen as the ‘forceful arm’ of local, state, and federal government, tasked with maintaining the status quo. The police have long been directed by the political powers, who have historically been made up of wealthy white men. It stands to reason that the police have traditionally served the interests of this socially dominant group. A common

argument for why police use of force differs based on suspect race and socioeconomic status is that police discretion favors the socially dominant and protects the status quo. Of course, this position tends to be vehemently denied by members of the socially dominant group, who argue that suspect behavior is solely responsible for police use of force. Nevertheless, the tension between the police and minority classes has fueled considerable discord and distrust in police legitimacy. Use of force perceived by citizens as unnecessary, unjust, or excessive undermines the social contract and the legitimacy of the police. In many circumstances, this is now the case: the police retain a cultural emphasis on aggressive crime-control tactics and have a self-image as society’s law enforcers (Brown, 1988). The citizenry, on the other hand, have come to expect that police not only control crime, but serve the community in ways that build social bonds and prevent crime. Officers are expected to be mentors, social workers, mental-health professionals, and counselors, as well as law enforcers (Terrill et al., 2003). Similarly, while the citizenry expects greater and more nuanced restraint in the exercise of law enforcement, police training and culture emphasize the need for officers to protect themselves by staying one step ahead of the suspect or safety threat. These differences of opinion reinforce the ‘us vs them’ mentality, in which officers increasingly feel the public does not understand the harsh realities of what they face on a daily basis, and the public increasingly resents police authority.

HAWKS VS DOVES AND THE EVOLUTION OF THE POLICE PERSONA Maynard-Smith’s famous ‘hawk versus dove’ model is one of the most important contributions in evolutionary game theory and of direct relevance to the ‘police persona’. At its most basic level, the hawk will choose the strategy of escalating aggression and


continue attacking until their opponent retreats or they themselves are injured. A dove might display aggression but retreat if their opponent escalates. In a contest between a hawk and a dove, a hawk would win. In a contest between two hawks, assuming both have equal ‘resource-holding potential’ (RHP) such as strength, access to weapons, etc., there is an equal likelihood of either winning. In a contest between two doves, the resource being fought over is shared (negotiation), or the War of Attrition model of threat to avoid actual fighting is employed to determine who gets the resource. Maynard Smith’s (1974) War of Attrition model states that when animals engaging in conflict cannot assess the other’s likelihood of beating them they will attempt to deter conflict through ritual displays of aggression. For an evolutionarily stable strategy (ESS) to occur there must be a mix of hawks and doves. A system of all doves is vulnerable to invasion by a mutant hawk and in a system of all hawks, the cost of loss becomes too great. The result is that when hawks are rare they have the advantage and are selected for. However, when there are more hawks than doves some hawks are forced to take on a dove strategy so the evolutionary ‘seesaw’ that typifies an ESS swings back the other way as doves are selected for. The same thing can be said for those that follow the rules and those that cheat in Hardin’s ‘Tragedy of the Commons’ scenario, where there are only so many resources to go around. When cheaters are rare their strategy is highly successful, but eventually the resources will run thin and their chances of detection will increase; thus the balance will be tipped back in favor of the compliers (Hardin, 1968). This type of ESS can be seen throughout the animal kingdom. For example, most seagulls catch fish but some wait by the shore and steal the food from the hard-working gulls. This is an effective strategy as cheaters get maximum benefit for minimum effort. However, when the cheating gulls start to outnumber the hard-working gulls some are


required to change strategies or nobody gets food (Dawkins, 1980). On average, police officers will be more successful with a hawk strategy than a dove strategy. This makes sense because if an officer comes up against a ‘hawk-like’ suspect and they themselves are ‘dove-like’, the suspect will likely win (get away, attack them, etc.). On the other hand, if the officer is ‘hawk-like’ they will likely win against a dove and have an equal likelihood of winning against a hawk. Research by Yabuta (2008), however, has suggested that there might be a third more complex strategy to add to the hawk versus dove model with particular relevance to policing, that of ‘assessor’. The assessor weighs RHP, then alternates between hawk and dove strategies depending on the situation. To assess is an ESS because it prevents inappropriate attacks on non-opponents. The role of assessor could be applied to police officers who must distinguish between opponents (threatening suspects) and non-opponents (general members of the public or complying suspects) and modify their strategy accordingly. How they select these strategies can also be explained by evolutionary theory.

GAME THEORY AND SELECTION OF AGGRESSION AND RESTRAINT STRATEGIES Selection between aggression and restraint strategies applies to policing in two important ways. First, it is expected that officers are able to expertly assess whether aggression is an appropriate response in a given situation. The justification for the decision is grounded in the level of threat in their opponents’ actions. Barash (2004) uses game theory, and the example of the game ‘rock, paper, scissors’, to demonstrate the success of a strategy that is dependent on another player. If you pick rock and your opponent also picks rock then you draw, the expected



return is zero, or E(R,R)=0. If your opponent has picked scissors you win and the expected return is one, or E(R,S)=+1; however, if they picked paper you lose and the expected return is minus one, or E(R,P)=−1 (Barash, 1982). If a player consistently employs one strategy such as rock, their opponent will catch on and use a defeating strategy. Thus, in the ‘rock, paper, scissors’ game the best strategy is to use each with equal probability. Now apply the game to police use of deadly force, where the options are ‘shoot’ or ‘don’t shoot’. If the officer shoots and the suspect represents a real threat, the officer wins (assuming he or she does not get shot first). If the officer shoots and the suspect does not represent a real threat (e.g. is trying to pull out a wallet, not a gun) then the officer loses and faces the consequences. If the officer does not shoot and the suspect represents a real threat the officer loses and might be injured or killed. Finally, if the officer does not shoot and the suspect does not represent a real threat the officer wins, as he or she has made the right decision. As in the ‘rock, paper, scissors’ game, the police cannot always favor the same strategy because they would be at high risk of making an error. Thus, officers must constantly weigh their perceptions of threat with the actions of the suspect and the consequences of their own decisions. Of course, officers have far more to think about than this simple analogy implies, and are usually not blind to the actions of the opponent. However, game theory exemplifies the decision officers must make when faced with a threat to employ either aggression or restraint. Evolutionary game theory explains why selection has favored certain characteristics, behaviors, or attributes, when success in a contest depends on the behaviors of others (Barash, 1982). For example, Maynard Smith’s War of Attrition model (1974) states that when animals engaging in conflict cannot assess the other’s likelihood of beating them or RHP they will attempt to avoid conflict through ritual displays of aggression.

This model can be observed in many species, for example howler monkeys or elephant seals that loudly vocalize to display aggression, fish that puff up to try and prevent attacks, and deer that shake their antlers at each other to determine who is the more dominant (Krebs and Davies, 1984). If this deterrence does not work and a fight ensues, then the contestant who is prepared to risk a higher cost and fight for longer will win. The War of Attrition model relates to police use of force because it shows how a cost–benefit analysis has evolved resulting in aggression only when necessary and only to the extent necessary. The latter relates to the second application of the balance between aggression and restraint in policing: that officers must apply immediate restraint following the use of aggression. Furthermore, the very aggression they use should be controlled and strategic as opposed to driven by fear, anger, or frustration. They are also expected to render or call for medical aid for injuries they were personally responsible for inflicting. The failure to apply appropriate restraint and allow aggression to become emotionally driven results in incidents such as the infamous beating of Rodney King in 1991. Video footage of the incident, featuring Los Angeles Police Department officers beating an African American man on the ground and circulated by media outlets nationwide, has come to symbolize how use of force in law enforcement can become unfettered, brutal, and deadly when left unchecked. Restraint, then, is a crucial component of a law enforcement officer’s tactical skill set. The evolutionary foundation of the balance between aggression and restraint is straightforward. Aggression when necessary can solve several adaptive problems. Aggression past the point of necessity in social systems, however, can produce costs and often fails to solve adaptive problems. The police, just like every social animal, must achieve a balance between aggression and restraint. However, officers are in a reasonably unique position in having to balance aggression and restraint as


a core function of their job, and answering to the public whenever they decide to employ an aggressive response. In some cases, aggression can be favored on the part of the police, and evolutionary theory offers some insights as to why.

THREAT SIGNALS AND THE ‘FIGHT OR FLIGHT’ RESPONSE The functioning of the human brain has not changed since the Pleistocene epoch. Humans evolved over millions of years in the African savanna where people lived in small groups of hunter-gatherers. This environment is referred to as the ‘environment of evolutionary adaptedness’ (EEA) (e.g. Bowlby, 1969). This is a critical time period and the environment where natural selection ‘designed’ the modern human species. One of the most important tools for survival, favored by natural selection, was the ‘fight or flight’ system for responding to threats. Threat response required efficient learning of threat signals and detecting threatening objects. An example is fear of snakes (Neuberg et al., 2010). Despite fear of snakes serving little purpose for the majority of humans in the modern era, humans tend to be particularly efficient at learning fearful responses to threat signals, and particularly inefficient at unlearning them. Relatedly, humans tend to be fearful or wary of coalitional outgroups (groups of people who are different from them) due to successful threat responses against attacking groups in the ancestral environment. This at least partially explains the concept of ‘implicit bias’ that humans have against groups that are different from themselves. Common implicit biases exist around race, ethnicity, sexual orientation, gender identification, and disability, among others. Although in the modern era we (typically) do not need to fear people who are different from us, we have evolved to favor this strategy, and this can lead to attitudes and


beliefs that we might not be aware of (James, 2017). Nesse (2005) describes responses to threat signaling that evolved within the ancestral environment, such as the fight or flight response, and some of the problems that arise in modern life because of these evolved responses. These ideas have relevance to policing, and officers’ use of aggression. Natural selection resulted in the human nervous system being highly responsive to threat cues. We do not wait to see a predator attacking to trigger the response system, but instead we are sensitive to subtle cues and engage the sympathetic system that allows us to fight or flee. Classical conditioning also plays a role here – if we have experienced a threatening situation in the past, a similar situation will be likely to trigger the fight or flight response in the future. This is the concept of conditioned anxiety to a cue of danger. ‘False alarms’ are inexpensive relative to the potential consequences of attack by a predator. This helps to explain why humans tend to be risk averse. This could also explain police shootings where officers shoot in the absence of concrete evidence that the suspect posed a deadly threat. From a survival perspective, the risk of being shot is worse than the risk of getting it wrong, and the fight or flight response can make us prone to responding to threat cues in the absence of real threat. James, Todak et al. (2018) speculated that this construct from evolutionary psychology can be seen in Fachner and Carter’s (2015) ‘threat perception failure’ (TPF) theory. TPF occurs when an officer mistakes a non-threatening object (such as a wallet) for a threatening one (such as a gun), or a non-threatening action (reaching for a wallet) for a threatening one (reaching for a gun) (see also Scharf and Binder, 1983, for a discussion of false-positive errors). Within the policing literature, TPF is associated with implicit racial bias, whereby officers are more likely to experience TPF when faced with African Americans than with people of other races and ethnicities. From an evolutionary perspective, TPF is



associated with fear and threat responses. Of course, one could argue that increased fear indicates increased bias, but bias is not the sole reason for a threat response. One of the causes of threat response in police officers is training they receive designed to increase anxiety and heighten attention to threat signals. An example of this training is ambush training. This type of training is well intentioned, in that it is designed to prepare officers for ambush encounters on the street, but it teaches rapid response over careful thought, and consequently results in a heightened risk of error. James Todak and colleagues (2018) argue that training should help reduce the incidence of sudden, impulsive use of force by officers that might be fueled by anxiety associated with a fight– flight response. Training that focuses on keeping the officer actively engaged (instead of relying on fight or flight) could reduce the number of accidental shootings by police (Binder and Scharf, 1980; Fyfe, 1996). This is feasible because, just as we learn to detect and respond to threat signals, we also can become desensitized to those signals when they do not result in threat. Understandably, an argument frequently made by the policing profession is that desensitization to threat cues could compromise officer safety. Directly counter to this argument, evidence exists that preventing officers from being overcome by a sympathetic nervous system response improves officers’ marksmanship and deadly-force judgment and decision making, ultimately promoting officer safety (Johnson et al., 2014).

GENDER-BASED AGGRESSION AND POLICE CULTURE Despite gender diversification in the police profession, policing remains an overwhelmingly male profession. Selection has favored individual aggression in boys and men, in particular with regard to the development and

protection of coalitions – groups who work together towards goals (Geary et  al., 2003). These groups provide reproductive advantages, as well as increased opportunity for status and protection. Even in highly social animals such as humans, group-level dynamics can facilitate individual aggression under some circumstances, in particular between male groups. A famous example of this was observed in the sociological ‘Robbers Cave’ experiments, where randomly assembled groups of boys engaged in between-group competition (Puurtinen et al., 2015). During these 1950s and 1960s experiments, boys were grouped arbitrarily. They quickly began coalition building and engaged in competition with the other group. Evolutionary psychologists posit that this is evidence of psychological mechanisms that motivate ingroup cooperation and outgroup-directed aggression (Sherif et al., 1961). Interestingly, when provided with a problem that required resources outside of their group, the boys would cooperate with the competing group for a period of time, before reverting to their own coalition. These insights have relevance to the police profession as a coalition. Police culture emphasizes loyalty to its members and a distrust of non-members (or at least a strong feeling that people outside the group do not understand them or have their best interests at heart). The police culture has clear benefits to individual officers – notably the belief that members of their group will ‘have their back’ (Paoline, 2003), which promotes officer safety. The feeling of belonging to a family is often noted as a draw to policing, and in many cases generations of people from the same family will join the profession. There are other aspects of police culture which are not as positive, for example the fostering of an ‘us vs them’ mentality, which can impair police ability to connect with the communities that they are expected to protect and serve. Also the ‘blue wall of silence’ or unwillingness to ‘rat’ on fellow officers when they break the rules can lead to accusations of


secrecy, corruption, and lack of accountability (Walker, 2001). Finally, the police culture is inherently masculine, and female officers can have challenges with acceptance, bias, bigotry, or unfair promotion practices. Police researchers have shown that officers who more closely align with the police culture are more likely to display aggression, on and off the job. This includes aggressive tactics during traffic stops (Paoline and Terrill, 2005) and citizen interactions (Terrill et  al., 2003). These officers are more likely to receive citizen complaints (Terrill and Paoline, 2015) and to use unnecessary force (Silver et  al., 2017). Furthermore, they are less likely to adhere to the principles of procedural justice (Terrill and Paoline, 2015) and are more likely to engage in misconduct (Kappeler et al., 1998). Finally, officers who have a strong connection to police culture are more likely to engage in intimate-partner violence (Blumenstein et al., 2012).

DOMINANCE, PRESTIGE, AND STATUS SEEKING Dominance hierarchies form when access to resources is limited and are common in social species. Within the hierarchy, some individuals have greater access to resources than others (Neuberg et  al., 2010). This is based on social rank, and its association with reproductive success in social species (Paquette, 2015). Among humans, these hierarchies are common across cultures (Neuberg et  al., 2010) and can be observed even in young children (Beaulieu and Bugental, 2007). Within dominance hierarchies, those at the top tend to induce submission to their dominance either through physical intimidation or control of resources (Cheng et  al., 2010). In mammals, dominant males have greater access to mates, which then leads to selection for these dominant traits. The construct of prestige, although related to dominance, differs in that it elicits freely


conferred deference instead of intimidationinduced submission (Henrich and Gil-White, 2001). There is an evolutionary basis for respecting those we consider to be prestigious. In some societies, prestige exists without dominance hierarchies, and deference to prestigious individuals offers advantages (e.g. proximity to potential mates who flock to the prestigious). Those with prestige enjoy benefits, including the desire for proximity to the prestigious (rather than distance, as is common with regard to dominant individuals), the admiration of others, preferential copying, obedience, and attention (James, Todak et  al., 2018). Of course, dominance and prestige are not mutually exclusive, and many individuals may attain both. But prestige does not depend on dominance. For example, a police officer who performs a heroic feat (such as rescuing a small child) is likely to achieve prestige, both among peers and within the community, even if they are not a ‘dominant’ officer. Status seeking is related to both dominance and prestige. Although the construct is from social psychology, it is relevant to evolutionary psychology, because status seeking is a product of competition for social status and consequent resources (Geary, 1999). Social status can be observed in children as young as two or three years old, particularly during same-sex play (Bukowski et  al., 2011). The construct of status seeking can also be observed in the literature on juvenile delinquency, especially regarding gang participation and violence (Thrasher, 1936). Within this context, serious aggression and physical violence can occur, especially between males, over issues that seem trivial. This is related to the idea of ‘saving face’ and not letting other males disrespect or question one’s social status (Felson and Steadman, 1983). Within policing, dominance, prestige, and status seeking are readily observed. A police officer who takes a dominant approach is likely to be seen as a protector, an aggressor, and someone who will not back down in the face of attack. This strengthens ties to the



police culture, and also promotes aggressive tactics with citizens, for example officers who escalate their responses in an effort to maintain control in a situation (Alpert et al., 2004). Escalation tactics are more frequently observed when officers are faced with citizens who disrespect their authority (Van Maanen, 1978) or display ‘contempt of cop’ (James, James et  al., 2018). Thus, officers’ physical responses to threats to authority and character can be seen as mechanisms for maintaining dominance during the encounter. This adheres to the policing culture, and is likely to secure prestige and status from their police-officer peers.

TOWARDS A BALANCE OF AGGRESSION AND RESTRAINT IN POLICING Despite a focus on aggression within the policing culture, police officers are adept at employing restraint. They do not typically employ force indiscriminately. Recently, however, serious allegations of excessive and unnecessary force used by the police against young Black men has sparked controversy surrounding the police profession. This has led to calls for action, and in some cases citizens taking matters into their own hands (either by rioting or attacking the police). Throughout the evolution of human society, when social order is threatened and revolution looms, the antidote is often authority reform (DeBenedetti, 1980; Shaw and Shaw, 1977; Wolpert, 1962). The final report from President Obama’s Task Force on 21st Century Policing recommends police reform to reduce tensions between the police and the people they are sworn to serve and protect (President’s Task Force on 21st Century Policing, 2015). The majority of the recommendations from the report are targeted at improving public trust in police, repairing broken relationships, increasing police legitimacy, and promoting procedural justice. Avenues towards

accomplishing these goals include training reform, policy change, and greater transparency. However, the type of reform the public expects is not likely to be successful while the majority of police training emphasizes aggressive tactics and police culture resists reform. According to the Police Executive Research Forum (2015), over 90% of the training hours officers currently receive are on aggressive tactics. Paired with the emphasis on physical aggression within the police culture, tactics that promote restraint are likely to be less appealing to police officers (Crank, 2014). The framework depicted in Figure 10.1 re-envisions the goal of the police in modern society as expertly balancing aggression and restraint. The proposed framework acknowledges the importance of controlled aggression in policing as a strategy for maintaining social order, but emphasizes the need to temper aggression with appropriate levels of restraint. This balance can be demonstrated across all elements of policing, from routine to deadly encounters. The proposed framework does not diminish the importance of aggression in situations in which it is legitimately required. For example, to competently arrest an assaultive suspect, an officer must overpower any resistance. Similarly, encounters that warrant police force require an officer to aggressively ‘win’ against the suspect. This is especially true for use of deadly force where the officer must guard against loss of innocent life, including their own. When officers are confident in their ability to employ aggression, they are less likely to activate a flight or fight response, because they are less likely to feel that their resources are overwhelmed. In other words, the police officer must have the ability to be a hawk, in order to select whether a hawk or dove strategy is more appropriate. The other side of the balancing scale is restraint. Restraint in this case is not to be mistaken for meekness, second-guessing, or unwillingness to dominate if the situation requires it. Restraint is defined as the ability



Figure 10.1  Police balance between aggression and restraint

to temper aggression, or avoid it when it is not warranted. On the restraint side, the officer is supplied with a toolkit of additional options that circumvent the use of physically aggressive tactics. It is important to note that these tactics (for example, tactical disengagement and verbal de-escalation) are not new; they have been around since the inception of the police profession. Arguably, however, they have yet to become central components of police work, given that the majority of training continues to promote aggressive tactics, and police culture continues to reward physical aggression.

PROMOTING RESTRAINT IN POLICE TRAINING AND POLICY Several strategies exist in the police profession for promoting restraint. One example is the use of ‘tactical disengagement’ or actively attempting to de-escalate a volatile encounter.

Police departments in the United States, including Kansas City (Missouri), have begun to implement tactical disengagement training (Police Executive Research Forum, 2015). There has been a move in other countries such as Canada and the UK in this direction, as well. The idea is to not force an encounter with a citizen when there is a risk of escalation and the reason for the encounter is minor. This mindset is antithetical to predominant cultural values in policing, which dictate that officers should not back down from a challenge and should jump in quickly to handle a situation (Fyfe, 1986; Paoline, 2003). The tactical disengagement philosophy teaches officers that they do not need to initiate or ‘win’ every encounter. Relatedly, communication tactics such as ‘verbal judo’, de-escalation, and motivational interviewing have been taught in many departments as a way to influence citizens into voluntary compliance without using physical coercion (Humphrey, 2013). Such techniques draw on professionalism and



empathetic connections with the i­ndividual’s personal situation to reach a mutually agreedupon solution to the problem. Verbal techniques require expert restraint and can be especially frustrating for police officers when they are faced with individuals who are combative, disrespectful, or rude (Pusatory, 2016). Switching immediately from aggressor to rendering medical aid is another example of how officers balance aggression and restraint. In fact, officers today are increasingly expected to immediately render aid to an injured person or else be publicly condemned for neglecting human life (Dart and Walters, 2016). Rendering life-saving aid following a use of force requires that an officer changes mindsets quickly, shifting from a ‘warrior’ to a ‘guardian’ role (Rahr and Rice, 2015) – an officer must drop their defensive and offensive stance and save the person’s life. An officer may need to shift back and forth between controlled aggression and restraint if the individual continues to resist or fight as the officer employs medical aid. From an evolutionary perspective, these expectations move beyond a simple decision to employ restraint upon achieving the end goal – we are asking the police to engage in the seemingly more unnatural behavior of actually preserving the wellbeing of a physical opponent by employing life-saving aid. Collaboration with other services also requires restraint on the part of officers. Officers are accustomed to being called on to solve a wide range of life problems that often have nothing to do with law enforcement but that the citizenry feels the police should do something about right away (Bittner, 1974). As such, police agencies are beginning to identify areas of police work that may be better handled if they are redirected to other professionals, or are handled collaboratively by multiple agencies. For example, when interacting with a suspect suffering from mental illness, an officer sometimes has the option to call on mental health professionals who can offer expert advice on the individual’s behavior. Indeed, this is an underlying philosophy of Crisis Intervention Team (CIT) training.

Officers can exercise restraint in tempering their tactics according to the mental health professionals’ information and suggestions. The same can be said for communicating with victims, distraught family members, friends, and witnesses on scene. Police departments in some US cities have begun to re-engineer their use of force training towards an emphasis on violence deescalation and avoidance. Officers in the Las Vegas (Nevada), New York City (New York), Seattle (Washington), Oakland (California), and Leesburg (Virginia) police departments have all received training on violence deescalation, teaching tactics designed to deescalate a police encounter and avoid the need to use physical force to solve the problem. Unfortunately, programs that incorporate some form of de-escalation or verbal tactics training are frequently offered in a fragmented manner, failing to teach how these skills can be integrated with the use of force training. A prevailing criticism of de-emphasizing aggressive tactics training for police is that it will result in decreased officer safety, and consequently decreased community safety. A central argument here, often voiced by officers themselves, is that researchers and others who are advocating for reform in police use of force do not understand the dangerous realities of police work. Supporting this argument, some evidence suggests that hyper-vigilance on the part of the police is necessary. Interviews with individuals who feloniously assaulted a police officer found that they were more likely to attack an officer if he or she seemed unprepared to react to a problem, did not appear to know an attack was coming, or seem to have dropped their guard (Pinizzotto et al., 2006). This research confirms police-culture beliefs, and has made the shift towards violence de-escalation difficult to accept by many rank-and-file officers. In contrast, de-escalation tactics may promote officer safety. In a crisis of police legitimacy, citizens are less likely to follow the law and comply with police commands. This has been documented in the policing


literature – people who perceive the police as legitimate are more likely to cooperate and obey the law (Mastrofski et  al., 1996; Tyler and Fagan, 2008). Thus, training the police in conflict- and violence-avoidance (i.e. to be more restrained) may reduce the likelihood that situations will escalate and the officer will become engaged in conflict. Such a situation results in an overall reduction in the risk of harm to all persons involved.

GROUNDING POLICE TRAINING IN EVOLUTIONARY THEORY With respect to threat response, training for reducing unnecessary or excessive force could focus on officers’ concerns about danger, and reduce the amount of training that promotes rapid response over reasoned decision making. For example, ambush training that teaches an officer that it is beneficial to be constantly alert may help an officer during the (statistically) unlikely situation that they are ambushed. However, it is also likely to increase the risk of officers rapidly responding to a perceived threat without evidence that a threat exists. It is unlikely that officers in the field will favor critical decision making over rapid threat response unless they have been taught to do so. Deadly-force judgment and decision-making training (either simulation or role-play based) can help promote critical decision making over rapid response, due to the consequence of ‘getting it wrong’. Police training can also reduce officers’ natural distrust of ‘outgroups’ via exposure. As the Robbers Cave experiments demonstrate, competing groups can put aside differences and overcome hostility when faced with a common problem requiring a cooperative solution. Community-orienteered policing (COP) strategies that focus on shared goals, such as improving the safety of people living in the community, have potential to discourage police perceptions of citizens as rivals


and vice versa. Examples of COP strategies include programs that promote citizen cooperation in crime reduction and events that allow police and citizens to interact without a power imbalance, such as non-crime-related community events. Another strategy for reducing outgroup distrust is implicit-bias training, which teaches officers about their biases, and provides strategies for identifying and overcoming the impact of bias on behavior. Diversification of the police force also has potential to reduce outgroup suspicion, due to promotion of ties to both the police and minority communities. Relatedly, promoting minority individuals to positions of power where they influence decisions and represent the police profession has promise for reducing outgroup distrust and suspicion. Although promising, these strategies have yet to be evaluated for effectiveness at promoting inter-group collaborative relationships between the police and the citizenry. The theories of dominance, prestige, and status seeking also have relevance to police training. It is easy to train officers to exhibit dominant control behavior. This is because this training aligns with evolved psychology. In the ancestral environment, however, the expectation related to an individual’s dominance behavior is that if the individual wins, the opponent submits. This is complicated in the modern environment because police authority is granted institutionally, and not based on a direct competition between individuals. In other words, no contest has established that the police officer is dominant to the citizen, so it is naïve to assume that the citizen will always submit. The citizen might have strong reasons for not submitting (e.g. gaining prestige and social status among peers). This can result in challenge to the police authority which, in turn, the police are unlikely to submit to. Police training that demands officers exert dominance will in these instances lead to escalation. Alternatively, training that teaches officers to reduce the likelihood of unnecessary



dominance contests can prevent the need for aggression. There are situations when it is appropriate and expected for an officer to be a hawk and take immediate control of a situation, regardless of escalation consequences. For example, if a suspect is armed and posing a deadly threat to those around them, an officer must neutralize that threat, quickly and decisively. The vast majority of police–citizen interactions, however, do not require the police to be forceful. Many of these interactions, particularly for police officers that work in ‘anti-cop’ neighborhoods, will be fraught with challenges to police authority. Policing scholar Van Maanen (1978) describes ‘the asshole’ or citizen who is not inclined to submit to police authority. When facing such a citizen, the officer can either engage in a dominance challenge or not. In the absence of criminal behavior, the officer has no grounds to force a citizen to submit to their authority (Klinger, 1994), and doing so will escalate the situation. Unfortunately for the police, not everyone will like them, and taking that personally is both unprofessional and unsafe. De-escalation training has potential for reducing unnecessary dominance contests between the police and the citizenry. De-escalation techniques are typically communication based, and attempt to influence citizens into voluntary compliance without using force (Humphrey, 2013). They can be used in volatile crisis encounters (e.g. hostage negotiation) or in day-to-day encounters for decreasing the likelihood that a situation will escalate (e.g. procedural justice). These techniques emphasize police need to read people, be professional, display empathy, and treat people with dignity and respect, regardless of their attitude towards the police. Evaluations of de-escalation techniques show that they improve public perceptions of police legitimacy (Todak, 2017). The idea that de-escalation techniques can be used to dissuade citizens from challenging police authority has implications for long-term police–community relationships. Influencing citizens away from antagonism

and towards cooperation results in more effective police work. The traditional ‘police persona’ of aggression, authority, and masculinity takes the strategy of deterrence to prevent challenges to dominance (‘my RHP is bigger than your RHP’). The evidence on the effectiveness of this strategy, however, is limited, and evidence exists that cooperative strategies are more effective (Tyler and Fagan, 2008). For example, the research literature on procedural justice demonstrates that officers who treat people fairly, with dignity and respect, listen to them, and work towards mutually beneficial outcomes are more likely to gain voluntary compliance and avoid useof-force encounters (Tyler and Fagan, 2008).

CONCLUSION Bittner (1970) defined the role of the police in terms of their legitimate authority to exercise coercive force. Police culture has embraced this definition, shaping training and policy around the use of aggressive crime-control techniques. This mindset has led to strained relationships between police and minority communities and a social crisis in the United States characterized by eroded police legitimacy. Examining police strategies for selecting tactics through an evolutionary lens provides a framework that re-envisions police function as the expert balance of controlled aggression and restraint. Aggressive ‘hawk-like’ strategies are appropriate in certain situations, but in many others, restrained ‘dove-like’ strategies will be more effective at gaining voluntary compliance and avoiding unnecessary dominance contests. Adopting this framework by focusing more training hours on force alternatives and promoting a culture of de-escalation may result in police behavior falling more closely in line with citizens’ expectations of police. Such a shift could result in a reduction in the rate of violence that occurs between police and citizens.


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11 Evolutionary Psychology, Jurisprudence, and Sentencing Eyal Aharoni and Morris B. Hoffman

I. JURISPRUDENCE AND PUNISHMENT1 Two thousand years ago, Socrates and an Athenian Sophist named Thrasymachus began a famous debate about human nature and the meaning of justice (Plato, 380 BCE). Are humans fundamentally good, built to cooperate and to appreciate beauty and truth, as Socrates contended, and therefore perhaps in need only of modest and occasional intervention by the state? Or are we fundamentally bad, built only to maximize our self-interest, as Thrasymachus argued, and therefore probably in need of heavy-handed restraint by a robust state? Is justice ‘the excellence of the soul’ (Plato, 380 BCE: 297) or nothing more than ‘the interest of the stronger’(Plato, 380 BCE: 275)? Humans have been having these same debates ever since, and the ways we have resolved them have largely defined our political and legal institutions. It is no coincidence that the founders of the United States were steeped

in the Enlightenment’s decidedly mixed version of this controversy. The Constitution’s distribution of powers between different branches of government was a reflection of the framers’ nuanced views about human nature. We are good enough to be largely free of an overbearing state, but not quite good enough to live without a state or to populate it without checks and balances between its parts. Until the paradigm-shifting insights of evolutionary psychology, behavioral economics, and the other disciplines described in Section II of this chapter, most modern takes on human nature have been skewed heavily toward Thrasymachus’ dreary views. The central simplifying assumption of classical economics was that each of us is relentlessly self-interested. Markets are an efficient integration of all those individual greedy unseen hands. Darwin’s insights strengthened the belief that we are self-interest machines, and biology’s great synthesis of evolution and genetics simply moved the locus of that selfinterest from the selfish individual animal



down to the animal’s selfish genes. Freud did much the same for the psyche, and Marx for the allegedly relentless march of economic and political history, framing the wars between self-interested classes. But then something delightful happened on this dark road to modern pessimism. Some economists, anthropologists, and psychologists had the audacity to look systematically at how humans actually behave instead of how these dreary theories predicted we should behave. And there were many surprising results. They discovered that when we play economic games in the laboratory, we engage in all kinds of cooperative behaviors that cannot be explained by classical economics, including sharing with and trusting other players, even when they are strangers. They discovered that we are not only not the rational self-interest machines conceived by classical economic theory, but that our apparent irrationality is predictable in many important decision-making domains. As discussed in more detail in Section II below, all these observations were then linked to the theoretical insights of evolutionary psychology. These same ancient and modern debates about human nature and the meaning of justice have echoed throughout the philosophy of law, also called ‘jurisprudence’. There are four main schools of jurisprudence – natural law, legal positivism, legal realism, and normative law – all addressed to these fundamental questions. Natural-law theorists view law in a way that is analogous to how natural philosophers viewed the physical universe: there are a priori principles (like Socrates’ truth, beauty, and justice) that animate legal systems just as physical laws (gravity, conservation of momentum) animate the universe, and humankind’s job is to discover these natural laws and apply them (Bix, 2010; Haakonssen, 1996). Natural law need not be grounded in the divine, although its most famous historical proponents – Socrates, Aristotle, and Thomas Aquinas – of course did so. As modern philosophers generally became less

satisfied with any systems that depended on unexaminable axioms of theology, natural law began to fall out of fashion. But there have been, and continue to be, modern efforts to re-ground natural law in concepts of secular morality, most prominently by Lon Fuller (Fuller, 1965) and Ronald Dworkin (Dworkin, 1986). We will see similar rekindled interests in secular morality from the normativists and even some positivists. Even though natural law’s fundamental principle is that law is a formal expression of morality, that position does not mean that all natural-law theorists take Socrates’ side in the debate about human nature. For example, Thomas Hobbes, a prominent Scottish proponent of natural law whose views were important to the founders of the United States, believed humankind’s natural tendencies were toward selfishness and violence, tendencies that needed curbing by a powerful state. Hobbes’ view of right and wrong seems presciently Darwinian; he once wrote that man is forbidden by natural law ‘to do that which is destructive to his life, to take away the means of preserving the same, or to omit that by which he thinks it may best be preserved’ (Hobbes, 1651). The second school of jurisprudence is called ‘legal positivism’. Like Thrasymachus before them, legal positivists rejected the fusing together of law and morality. The ‘positivism’ simply means that laws are rules posited by man, not by God. They are social constructs and nothing more. The role of the legal positivist is to describe those social constructs and to analyze them non-normatively, especially the processes by which laws come into being (Coleman and Leiter, 2010). There are many different subspecies of legal positivism, some of which vary by the degree to which they pay attention to moral groundings (Gardner, 2001). One of the most prominent modern positivists was H. L. A. Hart (Hart, 1961), who famously debated Lon Fuller in the Harvard Law Review in 1958 (Fuller, 1958; Hart, 1958). The third school of jurisprudence is ‘legal realism’. Legal realists, like positivists, take a


non-normative view of law. But unlike most positivists, they are not satisfied with simply accepting the conventions of law as given social constructs. Instead, most legal realists are interested in the psychological engines that drive legislatures to adopt laws and judges to interpret them (Leiter, 2010). The law and economics phenomenon – using the insights of economics to study the relationship between law and its intended and unintended consequences – is a modern branch of legal realism. There are many other branches, including perhaps the most extreme one, usually credited to Oliver Wendell Holmes, Jr. In Holmes’ view, law is nothing more than a prediction of the results of adjudication. The promise contained in a contract, under this view, means nothing other than a prediction that whoever breaks the promise will have to pay damages. To Holmes, law is power dressed up in process (Alschuler, 2000). Critical legal theory and its cousin, critical race theory, are modern versions of this extreme legal realism. The fourth and most recent school of jurisprudence is normative law. The normativists, somewhat like Fuller’s and Dworkin’s secular naturalism and the more morally interested positivists, focus on the foundations and justifications of the law. They are not satisfied either with the strict positivist assumption that laws are just arbitrary social constructs or with the realists’ fascination with the levers of power. They examine the purposes of law, and study methods to measure whether those purposes have been optimized (Shiner, 2010). All you non-philosophers out there are probably wondering what in the world any of this esoteric theorizing has to do either with evolutionary psychology or with how the law actually operates on the ground. The answer is that jurisprudence and evolutionary psychology are both concerned with human nature. As evolutionary psychology is impacting our fundamental view of what it means to be human, those impacts portend important consequences in many areas of the


law. The one we consider here is criminal sentencing. The debates between the four schools of jurisprudence in some ways echo, and in other ways are distinct from, the justifying theories that underlie criminal punishment. There are four main justifications for criminal punishment: retribution, rehabilitation, deterrence, and incapacitation (Alschuler, 2003; Davis, 2009). Retributivists generally believe that punishment is its own categorical good, and therefore it need not accomplish, or be validated by, any external effects. Hence, the other three theories, in contrast to retribution, are sometimes lumped together as ‘utilitarian’. Retribution is the oldest punishment theory, though its formalization is generally attributed to the German philosopher Immanuel Kant (1797). One can hear legal naturalism within retribution. Precisely because there is a natural core of right and wrong, punishment is as much a part of that a priori core as the right and wrong itself. But there are also positivist and realist currents in retribution. Kant’s intellectual successor, Georg Hegel, once wrote that criminals must be punished simply to earn their way back into the social fold. Crime is a breach of the social contract, which requires that the breacher pay damages in the form of suffering (Hegel, 1820). Deterrence was the first utilitarian rebellion against retribution. Utilitarians like Cesare Beccaria (1766) and Jeremy Bentham (1830) believed that no social group had the right to inflict punishment on its members unless that punishment resulted in a net social good. For proponents of deterrence, punishing wrongdoers is permissible because it deters both the person being punished (special deterrence) as well as others (general deterrence) from committing future crimes. Early proponents of deterrence focused on special deterrence. Bentham once famously asserted that no state had the right to punish any criminal, even a murderer, if it could be certain the criminal would never commit another crime (Bentham, 1830). But of



course, punishment that might not deter the wrongdoer may nevertheless deter millions of others, and thus be a net good. Modern proponents of deterrence therefore tend to focus on general deterrence rather than special deterrence. Both kinds are an amalgam of different jurisprudential schools. Like the realists and normativists, the deterrence school of punishment is focused on the way law accomplishes, or fails to accomplish, its central purpose of deterring crime. Rehabilitation is deterrence writ small. It focuses not on deterring the population as a whole, or even the particular criminal being sentenced, but rather on treating criminals to make them better persons who are less likely to commit future crimes. Rehabilitation became pre-eminent in US law at the beginning of the 20th century, as progressives viewed crime as mostly a product of failed social systems, and criminals as socially diseased and in need of a cure. It began to fall out of favor in the late 1960s (Allen, 1978; Alschuler, 2003). Incapacitation is the most recent justification for criminal punishment, at least when it comes to non-capital crimes. It ascended as a theory of punishment beginning in the 1960s as rehabilitation began to wane. Incapacitation, like special deterrence and rehabilitation, is focused not on the population as a whole but on the individual criminal. Incapacitationists believe the primary purpose of punishment is to remove criminals from society so that they do not commit more crimes. Unlike the other three theories of punishment, which attempt in different ways to remove people’s desire to commit future crimes, incapacitation is designed to remove their ability. These theories had important, real-life effects on the way we have treated criminals. When retribution was king, sentences in the United States were generally, and perhaps surprisingly, quite mild in length. Indeed, the Quakers invented the penitentiary in the late 1700s as a more merciful alternative to death and banishment, which were the punishments

for most serious crimes. Penitentiaries were not originally intended to be criminal warehouses. They were a place for criminals to contemplate their crimes and futures – to be penitent. Prison sentences for non-capital crimes in these early years were extraordinarily mild by modern standards – months rather than years. When rehabilitation ascended at the turn of the century these mild sentences became quite harsh. Cures took time. The length of prison sentences skyrocketed. Deterrence and incapacitation theories, especially prominent in the 1970s as rehabilitation fell out of favor, further boosted sentence lengths. These theories have all survived to some extent. Today, in all federal and virtually all state courts, judges are expressly directed to consider all of them when imposing a sentence. The federal statute, 18 U.S.C. § 3553(a), is typical. It provides that federal judges shall consider … the need for the sentence imposed: a.  to reflect the seriousness of the offense, to promote respect for the law, and to provide for just punishment for the offense [retribution]; b.  to afford adequate deterrence to criminals [general deterrence]; c.  to protect the public from further crimes of the defendant [special deterrence and incapacitation]; d. to provide the defendant with needed educational or vocational training, medical care, or other correctional treatment in the most effective manner [rehabilitation].

The idea of this kitchen-sink approach is undoubtedly that different kinds of cases will tend to command different punishment goals. But how ought we resolve conflicts between these goals? For example, how should we deal with an offender who is morally culpable but not dangerous? Or dangerous but not morally culpable? The theories don’t tell us when one kind of goal should predominate over another. And if we need to consider all four goals, as most statutes command, none of the theories explains how judges are to integrate the theories’ incompatible goals.


If we punish only to deter, then why do we often punish serious wrongdoers who have low recidivism rates (murderers, for example) more than wrongdoers with astronomical recidivism rates (forgers, for example)? Similarly, if the main goal of punishment is to rehabilitate, then why do we punish Bentham’s already rehabilitated killer at all? If we only punish to incapacitate, then why doesn’t every criminal get a life sentence, or a sentence gauged only to the risks of his recidivating? It seems like something else, something non-utilitarian, is animating our actual sentencing practices. There’s a wonderful thought experiment (Alschuler, 2003) that sheds light on the incompleteness of all the utilitarian theories and hints that our retributivist urges run very deep and need to be acknowledged. Imagine a society in which all first-degree murderers are executed as part of the halftime show at the Super Bowl. The method of execution is a laser beam that we are told inflicts unimaginably excruciating pain on the prisoner for several minutes before he is terminally vaporized. But unbeknownst to us, the ‘killer’ beam is really a painless transporter beam, and it sends the prisoners to an idyllic island in the South Seas where they live out their lives in luxury but can never return. This system should be fine with true utilitarians. Deterrence is maximized, the murderers are rehabilitated (at least in the sense of being sent to a perfect society without social wants), and they are likewise incapacitated from ever hurting the rest of us again. But there is something deeply unsettling about such an approach. It is not fair. A retributivist would say that the murderers are not getting their just deserts (and in fact they are being rewarded for their heinous crimes). But retribution comes with its own incompleteness issues. How much desert is just, and why? Even more fundamentally, retribution seems to be built on the same unsatisfactory a priori sands as natural law. Philosophers might say that retribution has no antecedent moral justifications. It just is, like gravity.


The evolutionary insights discussed in Section II below address these central criticisms of retribution: our core moral intuitions evolved, and one of those intuitions is to punish serious violations of the other moral intuitions.

II. SCIENTIFIC PERSPECTIVES ON THE ULTIMATE AND PROXIMATE FUNCTIONS OF PUNISHMENT To predict where a storm front is heading, it helps to understand its initial conditions. The same is true for human nature. According to the perspective of evolutionary psychology, human behavior is enabled by brains that solved ecological problems – problems such as finding and maintaining good cooperation partners – favored by natural selection. So consideration of the problems that our brains evolved to solve can help to explain and predict the motivations that shape our social institutions, including, perhaps, the justice system. It is through this lens that it makes sense to ask what an organism would stand to gain from being punitive. Punishing other people is costly. At minimum, it takes time and energy, and it exposes the punisher to the risk of retaliation. So, unless a given punishment strategy tended to confer proportionally large benefits to the punisher, such a strategy would be unlikely to have evolved by natural selection. Yet punishment has been a ubiquitous part of human society (Brown, 1991). A growing body of empirical scholarship has thus sought to identify the potential benefits that common punishment behaviors are, in an ultimate sense, designed to procure. Here, we discuss some key results from this scholarship as well as their added value for our ancestors and possibly for modern legal institutions.

Second-Party Punishment Among the various forms of punishment that occurs in human societies, the simplest is



second-party punishment: when a victim retaliates against the victimizer. Retaliation is risky business. Yet it’s a common response to cheating and aggression in humans and even some non-human animals (CluttonBrock and Parker, 1995; Jensen et al., 2007). So, what are the benefits to be gained by second-party punishment? The evolutionary psychology literature provides at least three notable answers. First, retaliation, if deployed effectively, provides self-defense. It can serve as a precautionary strategy for managing a hazard in the environment (Fiddick et al., 2000), not unlike our instinct to shut our eyes in a dust storm. In this way, one need not posit the existence of an evolved psychology of social interaction because our need for self-preservation extends beyond the social. Indeed, there are many examples of self-defense across animal species, social and non-social alike, including algae (Paul and Fenical, 1986) and guppies (Godin and Davis, 1995). The most fundamental form of self-defense may be the immunological response (Hoffman and Krueger, 2017). Clearly, at least some of our evolved psychology may support retaliatory behavior, not to interface with the cheater’s motivations or perceptions, but more simply to protect oneself from harm. Another potential benefit to be gleaned from retaliating could be to gain a direct-­ fitness advantage over the cheater. An impulse to ostracize, kill, or otherwise debilitate the cheater could directly advance one’s own prospects, if deployed successfully (Trivers, 1971). However, since such actions invite dangerous countermeasures and thwart the possibility of future cooperation, this strategy would seem to be limited to situations in which continued victimization is assessed to be highly likely but the likelihood of mutual cooperation is low. In the environment in which our punishment psychology evolved, situations like this would have been more common when the offender was a member of a competing coalition rather than a member of one’s own social group.

A third way in which a victim could b­ enefit from retaliation is by transforming the cheater into a valuable cooperation partner. This characterization is known as the theory of direct reciprocity, proposed by Trivers, and there is considerable evidence for its operation in both human and non-human species (Trivers, 1971). For this strategy to be effective, the imposition of costs on the cheater would have to ‘educate’ the cheater by altering his incentive structure for how he conducts future interactions with the punisher. In other words, the punishment, or at least a credible threat of punishment, must appeal to his psychology of deterrence. If successful, this strategy not only protects the punisher from further exploitation but also enables reciprocal gains in trade between the dyad via increased cooperation. Thus, this strategy would commonly target members of one’s own existing social network. So, while retaliation might be risky, it can also pay dividends.

Third-Party Punishment Third-party punishment: why bother? Human punishment behavior, of course, is not limited to two-party contexts. Across history and across cultures, punishment by ostensibly independent ‘third’ parties is pervasive. In the ancestral environment, thirdparty punishment would have been delivered by members of the victim’s broader community, usually small coalitions of men who, together, could deliver punishment at lesser risk to any one individual. In modern societies, such activities have been largely delegated to social institutions like the criminal justice system, which empower disinterested triers of fact, like judges and jurors, to deliver third-party punishment. The fact that punishment is so costly is particularly problematic for evolutionary theories of third-party punishment since third parties are defined as people who are not involved in the offense and so do not stand


to gain directly from the punishment. Why should they bother? The answer may lie in the fact that they are not really independent parties after all. Supposed third parties may have implicit social motivations driving their punitive attitudes even if they do not have conscious access to those motivations. This is because, being human, their minds evolved in a hyper-social context. People with traits that enabled them to exploit the social marketplace gained a fitness advantage. So, it is relevant to ask, in an ultimate sense, how these so-called third parties could stand to gain from particular types of punishment behavior, and how these gains might undergird modern legal justifications for punishment. A rich body of literature provides some empirical answers to this question. The first is kin selection, which predicts altruism toward genetic relatives. As expressed by the highly influential Hamilton’s Rule, the degree of relatedness (given the modest assumption that our ancestors could recognize their kin with some accuracy) predicts the degree of altruism because such altruistic behaviors increase the replication of our genes (Hamilton, 1964). Under these conditions, our tolerance for risk should increase – a prediction well-captured by the quip credited to biologist J. B. S. Haldane that he’d be prepared to die for two brothers or eight cousins (Connolly and Martlew, 1999: 10). Thus, costly punishments that deter or incapacitate actors from cheating our kin should be favored by natural selection. Indeed, evidence for kin-based punishment has been widely documented (Daly and Wilson, 1988). Since kin-based punishment must effectively prevent or discourage cheating in order to be selected, it is compatible with the incapacitative and deterrence-based philosophical justifications for punishment. Of course, punishments by judges and jurors are not supposed to favor kin. Indeed, the law specifically bars judges and jurors from serving in such cases. So an additional explanation is needed to explain third-party punishment in non-kin contexts. One such


explanation is strong reciprocity. According to this view, altruistic punishment can evolve because groups of people who expressed this trait deterred cheaters and, thus, enjoyed more cooperation than those who did not (Gintis, 2000). Support for this theory has been argued on the basis of a series of economic game studies. In these studies, participants who engaged in a repeated public-goods game demonstrate a willingness to punish third-party defectors at a cost to themselves, and this behavior sustained a norm of cooperation across the group of players (Fehr and Fischbacher, 2004; Fehr and Gächter, 2002; Fehr et  al., 2002). Since punishment of this sort must effectively discourage the cheater or other tempted onlookers in order to be selected, this theory is compatible with the legal justifications of special and general deterrence. Despite its intuitive appeal, scholars disagree about the viability of such an altruistic strategy given that groups that punish would be vulnerable to exploitation by second-order cheaters, namely, people who shirk their contribution to the enforcement of punishment (Krasnow et al., 2015; Tooby and Cosmides, 2016). There is a burden, critics argue, to explain how the enforcement of punishment ever gained an evolutionary foothold, given that it’s individually costly. To explain how third-party punishment could benefit the individual punisher, one theory – social exchange theory – highlights the implicit value of the cheater and victim to the punisher. According to this theory, since humans evolved in small social exchange networks, most people that we encountered on a day-to-day basis would have been network members (i.e., direct resources to us), and so we operate on assumptions that our peers, and even most strangers, are potential exchange partners (Delton et  al., 2011; Krasnow et al., 2013). Under this constraint, if an actor cheats a victim, ‘third parties’ who punish the cheater gain a direct advantage in social capital by deterring the cheater. This hypothesis has received support from multiple methods including experimental



surveys and economic games with real stakes (Aharoni and Fridlund, 2013; Delton and Krasnow, 2017; Krasnow et al., 2012, 2016; Pedersen et al., 2018; Price et al., 2002). This theory is a generalization of Trivers’ directreciprocity theory (1971), and it is most compatible with the legal justification of special deterrence. Other efforts to explain how third-party punishment could evolve at the individual level point to the reputational benefits of punishing. Known as indirect reciprocity, this theory states that by punishing a cheater, third parties accrue reputational credit with the victim and other community members, such that if the third party helps the victim by punishing the cheater, someone else may help the third party in the future (Nowak and Sigmund, 2005). People who are willing to enforce costly punishment signal their commitment to group norms, thereby broadly advertising their own social status (Frank, 1988). Since this strategy is designed to incentivize both second and third parties in the network, it is compatible with the legal justifications of special and general deterrence.

Third-party Punishment: how is it done? Besides asking what a punisher might gain by punishing a cheater, it would be valuable to understand by what manner punishment might achieve these ends. Most evolutionary theories of punishment posit that punishment increases the punisher’s fitness by reducing recidivism, but they are sometimes hazy about the proximate mechanism – how our evolved punishment response reduces recidivism. Here, we discuss some answers to this question of mechanism. From an evolutionary perspective, the most direct way to gain a fitness advantage over a cheater is by imposing corporal punishments like injury or death, as we discussed in the section on second-party punishment. This strategy assumes a motivation to (temporarily or permanently) behave in ways that incapacitate the cheater, but to achieve its aim, it does

not require a deterrence psychology – a folk psychological theory of the cheater’s or other group members’ motivations and incentive structure. This makes the incapacitative strategy cognitively efficient. However, this strategy is costly, partly because it could forestall a lifetime of future contributions by the former cheater to the social exchange community. Therefore, it should have evolved to be used as a last resort, and only when the costs imposed by the cheater are expected to outweigh his lifetime contributions. Another, potentially less risky, way to limit the probability that the cheater will cheat is to socially exclude, or ostracize, that individual from the group. By removing his opportunities to trade on the social market, this also reduces his opportunities to exploit cooperative group norms. In a general sense, this action can also be understood as an incapacitative strategy, but unlike corporal punishments, it may be easier to revoke. Thus, it would have been a useful strategy in ancestral environments, which lacked correctional institutions to perform the incapacitative work. Though incapacitation is a recognized legal justification for punishment, socialscience research suggests that it fails to capture a dominant feature of typical punishment psychology, namely, the desire to inspire changes in the cheater’s mental state. It is this feature of punishment psychology that ultimately defines the deterrence motive. The advantage of deterrence strategies over other strategies like direct-fitness reduction or ostracism is that, if effective, they immediately restore gains in trade between the former cheater and the social exchange network because they convert the cheater into a cooperator. Different scholars have characterized this process in slightly different ways. Some have described deterrence as a form of coercion (e.g., Matravers, 2000). The implication is that, while it may be against the cheater’s personal interest to shift to a more cooperative social strategy, the heavy threat of


punishment may demand it, and so through a rational fear of that negative reinforcer, the cheater is compelled to change his behavior, against his deeper preferences. Certainly, as an empirical matter, most people are responsive to the threat of punishment, and so this form of deterrence is likely to play a role in crime and punishment psychology today. But a moment’s reflection suggests that there is something deeply unfulfilling about a cheater who plays by the rules only because of fear of punishment. Instead, we seem to crave a genuine mental transformation: we want the cheater to understand how he harmed us, and to fully endorse and internalize the values that guide our self-protective social norms (Nahmias and Aharoni, 2017), perhaps in no small part because when we internalize norms, we can worry less about catching norm violators. They catch themselves. Scholars have described this deterrence motive as a form of education or recalibration, namely, to change how much the cheater values our welfare relative to his own (Petersen et  al., 2012; Trivers, 1971). Consistent with this perspective, experimental research demonstrates that we care deeply about whether the offender understands why he’s being punished. For instance, in an experimental stock-market game, participants were more satisfied with their punishment of an ostensible cheater when they received evidence that the cheater understood why he was being punished and even more satisfied when the cheater expressed a commitment to stop cheating (Gollwitzer and Denzler, 2009). Theoretically, it’s not surprising that we would evolve to favor a fundamental transformation in values over a more simple, coerced obedience. This is because coercion only works in the presence of a credible enforcement threat, whereas a recalibration of one’s values is self-enforcing. In this sense, effective recalibration harnesses the power of first-party punishment, which we discuss below. If punishment is designed to deter cheaters by recalibrating their value structures,


punishers should be sensitive to signals that the cheater had an unfavorable value structure to begin with. This could explain why punishers care so much about mens rea – the mental states at the time of the offense – such as criminal intent and knowledge of the risk of harm (e.g., Aharoni and Fridlund, 2011; Cushman et al., 2013). A punitive sentiment that didn’t care about these mental states would end up imposing heavy costs on genuine cooperators who had a stroke of bad luck, like a driver who caused a fatality as the result of a brain seizure. Typically, we don’t punish such individuals as harshly, if at all, and one reason could be that unlucky people who are otherwise morally innocent are not as likely to repeatedly undermine cooperative norms in the future. The presence of mental states like criminal intent, in contrast, are prognostic of future recidivism. In other words, a likely proximate function of punishment is to impose ecologically rational constraints on who we should punish. The premium that our deterrence psychology places on the cheater’s mental states reveals another lesson for the law: attempts to deter a cheater by encouraging internalization of norms would seem to qualify as a form of rehabilitation. As we noted, standard punishment theory treats deterrence and rehabilitation as separate motives for punishment. But both motivations, if delivered effectively, are designed to change behavior by inspiring a change in the cheater’s personal goals and values. Where they differ is that the deterrence motive places greater emphasis on the role of coercion as a motivator for recalibration. Whether coercion is any more effective a motivator is an empirical question. If coercion simply represents the threat of suffering, then as we discussed in the Super Bowl thought experiment, many people would be deeply unsatisfied by rehabilitation sans suffering. But if we could achieve such ends without the harmful means, then why do we feel an obligation that the offender should suffer? Why do we boil with outrage when he does not? Stated differently, what evolved



purpose is served by the offender’s suffering and the torrent of retributive impulses that give rise to it? The answer brings us to our final point about how our evolved punishment psychology carries out its function: via sophisticated motivational programs we call emotions. As economist Robert Frank (1988) forcefully argued, emotions serve as commitment devices: they are conspicuous, costly signals that commit us to a particular course of action. This is well illustrated by a classic anecdote of a game of chicken played by two opposing drivers. If one driver, while revving his engine, removes his steering wheel and drops it out the window for his opponent to see, that opponent must take seriously the first driver’s commitment to winning. If retributive emotions are like our first driver, they can be understood as part of a system that is motivating us toward a particular punishment strategy. The fact that these retributive emotions are not sated until the offender suffers suggests that the suffering may likewise serve a motivational role for the offender, namely to change his offensive behavior by shifting the balance in how much he values our welfare (Petersen et al., 2010). So, retributive emotions can be understood as mobilizing punishment and facilitating offender behavior change – functioning to keep both parties honest and invested in long-term reciprocity. The punisher, of course, need not be consciously aware of the functional role of these retributive emotions in order for them to exert their effects. Conceived in this way, the retributive motive for punishment is not in opposition to the utilitarian motives, as legal theory implies. Rather, it is an expression of them. In this view, we are psychological retributivists but adaptive utilitarians (Cushman, 2015). Retributive emotions commit us to punishment – a costly signal of our status that enhances the punisher’s fitness, either directly or indirectly, by modifying the cheater’s fitness, rational incentives, or social values. In this view, the legal purposes of

punishment are not wholly incompatible – they are just operating on different levels of analysis. Thus, the application of evolutionary theory carries the potential to synthesize the legally disparate theories for punishment.

First-Party Punishment: Conscience, Guilt, and Shame We’ve saved first-party punishment for last because it might be the most complex, and also because, in important ways, its effectiveness depends on the other two types. Firstparty punishment, as the phrase suggests, could be loosely understood as the tendency to ‘pre-punish’ ourselves with the bite of conscience to help us refrain from violating norms in the first place.2 Guilt and shame are also versions of first-party punishment, though they generally operate after we have violated a norm, and serve the function of reducing the chances of violating that norm again. Of course, with an animal as smart and devious as we humans, there is much overlap between conscience, guilt, and shame. We might feel guilty or ashamed even for contemplating a wrong. Likewise, we might look back on some of our decisions and wonder why our conscience did or did not save us from doing wrong. The bite of conscience is not just a human universal; it is a substantial part of self-image across cultures. It is central to many religions and mythologies (Katchadourian, 2009). It was probably a critical solution to the problem of effectively deterring antisocial behaviors in our social networks. At the proximate level of explanation, one of the reasons you don’t punch your neighbor during a political argument – perhaps the main reason – is not that you are afraid he’ll punch you back or that you will be punished by the criminal justice system, but rather because you know it is wrong. Brains with built-in systems that make their owners feel bad when they contemplate cheating are brains that will not cheat as often. This is what we mean when we said earlier


that an offender has recalibrated his value structure or internalized a norm. Conscience is the first line of defense against the commission of antisocial behaviors, and at an ultimate level, it worked in concert with the other forms of punishment to deter individuals from undermining our ancestors’ precious social exchange network. Presumably, it had to work in concert with other forms of punishment because without an external threat of punishment, there would be little incentive to regulate oneself. One way to appreciate how important conscience is to our cooperative nature is to study people who don’t seem to have a conscience – psychopaths. Psychopaths tend to have deficiencies in brain regions associated with moral decision-making, including affective memory, inhibition, and empathy (Kiehl, 2007). Unsurprisingly, psychopaths make up a hugely disproportionate segment of incarcerated adults, are notoriously resistant to traditional punitive and rehabilitative treatments, and therefore consume an astonishing proportion of our criminal justice resources (Kiehl and Hoffman, 2011). A growing body of research has also begun to examine whether certain psychopathic traits might themselves contain evidence of adaptive design (Glenn et al., 2011). Such insights would underscore the need to investigate alternative approaches to behavior modification that better account for individual differences. If conscience evolved to steer us away from the commission of antisocial behavior, then guilt and shame evolved to help us learn from lapses in conscience. Research suggests that the emotion of guilt and the rumination that often accompanies it evolved to change an undesirable pattern of behavior by recalibrating the cheater’s relative utility functions for alternative goal states – the same process of recalibration discussed above. Similarly, the emotion of shame evolved to signal to others the cheater’s commitment to change through public acts of compensation and penance (Nahmias and Aharoni, 2017; Sznycer, 2018; Trivers, 1971).


In a classic experiment by Wallace and Sadulla (1966), individuals were led to believe they broke an expensive machine, and the transgression had either been discovered or not. The investigators found that compared to a control group who did not break the machine, the participants whose transgression was discovered were more likely to volunteer for a separate, painful experiment. Volunteering for a painful experiment, and other shame displays, can be understood as a costly signal of one’s commitment to the group, that one has internalized the purpose of punishment, and potentially that secondor third-party punishment is unnecessary. This pattern of behavior suggests that selfgoverning psychological systems are in place but may require social input to be triggered. This dependency would make sense if our self-governing systems coevolved with secondand third-party punishment systems. By implication, effective criminal punishment practices might be those that utilize the natural threat of public exposure to motivate offenders to recalibrate their internal model for how to treat others – or at least for how not to get caught. Many legal practices already exploit such properties, for instance, in publishing the names and addresses of local sex offenders. But to maximize their effectiveness, such practices should leverage rather than subvert our intrinsic, self-regulatory emotions. If so, such practices could qualify under the law’s deterrence- and rehabilitationbased justifications for punishment.

III. ANOMALOUS BYPRODUCTS OF OUR EVOLVED PUNITIVE ATTITUDES Though natural selection has fashioned sophisticated punishment strategies designed to protect the punisher’s interests and preserve norms of cooperation, it doesn’t always do this well. Natural selection produces relative fitness advantages. It does not optimize – it produces minimally viable solutions.



Moreover, evolution by natural selection is slow, which means that today’s adaptations reflect fitness advantages with respect to ancestral environments, not modern ones. When a trait that evolved to solve a problem in the environment in which it adapted behaves differently in a more contemporary environment, it is known as an evolutionary mismatch. This lack of fit between the adaptation and its present environment can produce behavioral phenotypes (i.e., byproducts) that are over-sensitive to some evolutionarily novel cues (as when we crave candy as a proxy for fruit) and under-sensitive to others (as when drivers underestimate fatally high travel speeds). Likewise, the objectives and interests of legal institutions and their stakeholders are not necessarily aligned with those of our hunter-gatherer ancestors, and there are plentiful examples of punitive behaviors exhibiting such over- and under-sensitivities. Here we discuss these discrepancies as a potential source of ‘subtractive value’ of human punishment expressed in modern environments.

Over-Sensitivity to Legally Irrelevant Factors Several examples demonstrate how our punitive instincts may be over-sensitive to factors that are not legally relevant or efficacious. For example, judges and jurors are highly susceptible to the anchoring phenomenon. One dramatic experiment showed that professional judges who were asked to make hypothetical prison-sentencing judgments predictably increased or decreased their sentence following a phone call from an ostensible journalist (an actor in the study) who asked whether the sentence will be higher or lower than ‘one’ vs ‘three’ years (Englich et  al., 2006). Since judges know they ought not take questions by the media, this tendency to conform their sentence to the journalist’s suggestion presumably occurred at an unconscious level. Such effects have been explained by known psychological biases

such as the availability heuristic, the tendency to place more weight on information that happens to be most cognitively accessible in that moment (Tversky and Kahneman, 1973). Although judges wouldn’t normally talk to journalists in the real world, similar anchoring effects could be caused by pretrial publicity generally. Another example of our over-sensitivity to legally irrelevant cues is the identifiable victim effect, which shows that people are more likely to support punishment when they know more about the victim – such as age or occupation, for instance (Jenni and Loewenstein, 1997). Given natural limitations on our cognitive resources, it makes sense that people who prioritized the most immediate information, such as who the specific victim was, would tend to have an advantage in the sorts of high-pressure social problems commonly faced by our ancestors. Of course, this logic does not necessarily result in fair and appropriate legal judgments. Arguably, not all information that judges and jurors learn about victims is strictly relevant to their judgments. Since some judges and juries are incidentally exposed to more information about victims than others, one implication of this research is whether attempts should be made to limit and standardize what victim information is and is not revealed to fact finders. Some widely studied examples of our oversensitivity to legally irrelevant cues include age, race, gender, and attractiveness biases. Experimental simulation studies have shown that defendants are more likely to receive higher sentence recommendations when they are portrayed as young, black, and male (e.g., Mitchell et  al., 2005; Steffensmeier et  al., 1998; Sweeney and Haney, 1992). Archival research has been less consistent, suggesting that any real-life sentencing biases against age, race, and gender may be small and highly variable (Bontrager et  al., 2013; Mitchell, 2005; Wu and Spohn, 2009). To the extent that these biases are real, however, findings like these have been explained in proximate terms including ingroup favoritism and halo


effects. But they are also consistent with more ultimate explanations of social exchange. According to these theories, in the environment in which our social brain evolved, demographic characteristics may have served as a conspicuous cue to group membership, and people who were willing to pay the cost to punish could reap direct rewards on trading markets by leveling more severe punishments against groups and individuals with whom they were most likely to compete for physical and social resources (Aharoni and Fridlund, 2013; Petersen et al., 2010, 2012). Ultimately, for such punishment biases to evolve, they would have had to be effective at deterring or incapacitating the most competitive opponents. And while the law takes pains to try to remove such response patterns from the courtroom, they often persist. Another example of our over-sensitivity to legally irrelevant cues concerns the disproportionate emphasis we place on severity as the preferred mechanism of punishment. The two most studied parameters by which a punisher can deter an offender are the severity and the probability of punishment. The intuition is that more severe punishments deter better, but research has shown that increases in severity have limited deterrent effect and diminishing marginal returns; increasing the probability of punishment would have a greater impact (e.g., Grogger, 1991; Paternoster and Iovanni, 1986). In the ancestral environment, the situation was different. People lived in small groups with little privacy, and so the looming threat of detection must have been real, and powerful. But in the massive societies we live in today, the probability that an offender is caught and adjudicated remains, on average, relatively low (Aharoni and Kiehl, 2013; Ehrlich, 1996), and offenders can exploit this fact. Despite the evidence that severe sanctions typically deter no better than moderate ones, people seem to readily accept modulating the severity of punishment as the primary instrument through which to express their punitive motives, consistent with the philosophical


principle of proportionality (see Robinson and Kurzban, 2006). One reason, as we discussed above, may be our instinctive desire to know that the offender will suffer because suffering once was an effective means of recalibration and long-term behavior change (Nahmias and Aharoni, 2017). Our punishment judgments are also sensitive to information from our internal, physiological environments. For example, research has provided evidence that judicial sentencing decisions are less favorable immediately following the shift to daylight savings time, when people tend to be most fatigued (Cho et al., 2017). Other research has shown a pattern of sentence increases following unexpected home-team football losses (Eren and Mocan, 2018), presumably by implicitly impacting the judge’s mood. Unconscious cognitive processes, such as those that regulate fatigue, stress, and mood, evolved as a part of a motivational system designed to prioritize our momentary physical and social needs, so they might have global effects on our decision-making, though it remains to be seen whether such effects are large enough to be decisive in court. Even subject-matter experts are susceptible to influence by extra-legal factors. The testimony of expert witnesses, of course, should be based on the principles of their discipline, but research suggests that scientific experts who engage in objective reasoning problems are (unconsciously) prone to produce evidence that confirms the preferences of the hiring party (Robertson, 2010; Wong et  al., 2015). One likely proximate explanation for this ‘adversarial allegiance’ effect is socially desirable responding, a form of motivated reasoning. Socially desirable responding probably had important social advantages for our hunter-gatherer ancestors, but in a modern trial context, these effects could also bias factfinders’ ascriptions of guilt and punishment. Another extra-legal factor that we may be sensitive to is how the costs and benefits of punishment are presented. Although the cost of incarcerating a defendant, for instance,



may or may not be important to judges and taxpayers, incidental changes in the availability of that information should certainly not drive sentencing attitudes. Yet recent research suggests that when professional judges and laypeople make sentencing recommendations for criminal offenders, they are more lenient when the direct monetary costs of incarceration are made salient, suggesting that they find those costs to be relevant but fail to spontaneously consider them under typical, low-salience conditions. As a consequence, removing the cost information (without also removing benefit information) may produce sentence length recommendations that systematically exceed those made under more transparent conditions (Aharoni et al., 2019; Rachlinski et al., 2012). This behavior pattern implies that individuals’ punishment attitudes are internally inconsistent across informational contexts, placing more weight on whatever information happens to be most readily available in the moment. This tendency may be rooted in a more general tendency to discount distant future rewards relative to immediate ones (Loewenstein and Thaler, 1989; Metcalfe and Mischel, 1999; Mischel and Ebbesen, 1970). Placing greater importance on the here and now might have been adaptive for people in need of quick results under conditions of very limited information (see Daly and Wilson, 2005), but such features do not necessarily promote the careful, disinterested, and judicious decision-making that we expect of modern criminal justice decisions. We don’t mean to imply that more regulation is always the best solution to reduce bias in the courtroom, but that a richer understanding of how and why we punish can serve to clarify discourse on appropriate strategies.

Under-Sensitivity to Legally Relevant Factors There are also examples of our punitive instincts operating in ways that are

under-sensitive to factors that may actually be legally relevant. For one, we seem to readily discount the value of modern, custodial punishment strategies. Through the use of police forces, prisons, and civil commitment facilities, it is now possible to incapacitate dangerous offenders with lower risk to victims, and without the need to impose suffering or coercive ultimata on the offender. But as discussed, we often feel outrage at the prospect of an offender spending his days in a cushy rehabilitation center. And we demand punishment of moral offenders even if they are no longer dangerous (see Connolly, 2010). In such cases, though the modern sanction may effectively satisfy the ultimate objective of the punishment adaptation (i.e., to reduce recidivism), it fails to meet the adaptation’s more proximate conditions, such as evidence that the offender has undergone mental recalibration by way of suffering and penitence. Such responses evolved in environments in which effective custodial incapacitative sanctions were unavailable – they evolved not for incapacitation but for deterrence. This could help explain public dissatisfaction with purely custodial sanctions. From a public-safety perspective, in the presence of effective incapacitation, the offender’s attitudes about his punishment should be irrelevant. But people still treat them as relevant (Gollwitzer and Denzler, 2009) presumably because efforts to recalibrate his attitudes would have been one of the best strategies for reducing recidivism in ancestral environments. For this reason, we may be inclined to discount or altogether reject recidivism-reduction strategies that bypass opportunities for inducing suffering and penitence. If so, whether our evolved psychology of punishment (i.e., to achieve deterrence via retribution) provides a good justification for rejecting correctional sanctions that are equally effective but more humanitarian is a worthy normative question, but not one that can be answered by the science alone.


IV. THE UTILITY OF THE EVOLUTIONARY PERSPECTIVE From Explanation to Justification Before we finish up with some speculations about how the lens of evolutionary psychology might clarify some issues in the criminal law (and even a few issues beyond the criminal law), we need to address the problem of Hume’s Gap, or what is also called the naturalistic fallacy. In 1739, the Scottish philosopher David Hume complained about how there is often a gap between what is and what some philosophers claim ought to be (Hume et al., 1739 ). Just because behaviors happen regularly, that does not mean they are morally grounded. Rapes and murders happen all the time, but that doesn’t mean they are acceptable under any jurisprudential theory of law. In more modern philosophical parlance, moral truths (‘the ought’) cannot be derived solely from observational ones (‘the is’). Evolutionary psychology has been a favorite target of criticisms revolving around Hume’s Gap (Rose and Rose, 2000). Just because killing a rival and kidnapping his mate may have been an effective strategy for our ancestors (Buss, 2005; Daly and Wilson, 1988), and therefore our brains are arguably built with motivations for these kinds of behaviors, evolutionary psychologists are wary about taking those ‘is’ observations into ‘ought’ realms like the law, and quite properly so (Pinker, 2003). But Hume himself never suggested the trip between ‘is’ and ‘ought’ was unnavigable; he was just complaining that moral philosophers jumped the gap without so much as a pause. Indeed, like virtually every other moral philosopher of his time, Hume believed the worlds of nature and morals were connected. His connective tissue was empathy and socialization: our own selfish desires to avoid pain cause us to hesitate to inflict pain on others, and that hesitation was Hume’s root of morality (Hoffman, 2014). We suggest that evolutionary psychology itself has now supplied a more rigorous


connection between the ‘is’ and the ‘ought’. Moral intuitions (including intuitions to punish) evolved precisely because they gave our ancestors a net survival advantage in their intensely social groups. Human punishment behaviors are not just widespread by chance; they are widespread because evolution has armed us with emotions that make us feel their moral bite. The boldest answer to the jurisprudential question with which we began this chapter – where does law come from? – is not that it comes from God (as the traditional natural-law theorists argued), or from social conventions (the positivists), or from the individual and varying interpretations of lawmakers and judges (the legal realists). Instead, it comes from our evolved moral intuitions. In this account of moral realism, our notions of right and wrong come from the same place as our opposable thumbs and spines. Understanding what goals our punitive impulses evolved to achieve and how they achieve them can help us evaluate the degree of alignment with our modern societal goals, and can help formulate hypotheses for how to manage those impulses. For example, if deterrence is our main goal, we can ask whether retribution is still the best way to achieve deterrence. If so, lengthy prison terms might not satisfy that goal as efficiently as lashings and scarlet letters. Or if retribution is not the best way to achieve deterrence, then it might make more sense to remove offender suffering from the equation and focus instead on evidence-based rehabilitation services. Such tradeoffs would not be discoverable without a theory of the function that retribution evolved to serve. Caution is still warranted. Many a moral and legal judgment must be exercised in the vast areas beyond and between our evolved moral intuitions. These intuitions give us only the broadest contours of a secular morality. Even for those readers who reject our suggestion that evolutionary psychology can itself be a small bridge across Hume’s Gap, it still has significant utility when examining



legal questions. We discuss three examples: (1) synthesizing the various punishment theories; (2) providing a framework for predicting behavior under uncertainty in ways that might help us use law to leverage those behaviors; and (3) helping to inspire practical legal reforms in circumstances where the distance between the law and our evolved behavioral predispositions is just too great to leverage. The application of evolutionary theory to the law carries the potential to fundamentally change how we think about legal justifications for punishment and their apparent tensions. As we have argued, our punitive sentiments, and the sense of obligation that accompanies them, evolved in part because they gave punishers a fitness advantage by deterring cheating behavior, thereby protecting their physical resources and social exchange networks. The ultimate benefit was deterrence, but the proximate mechanism to accomplish that deterrence was retribution. When a wrongdoer revealed cues that he/she is not a good candidate for deterrence, other tactics were available, and these are reflected in sentiments like the desire to ostracize, incapacitate, or rehabilitate. Our powerful desire to forgive and be forgiven, about which there has developed a significant behavioral- and evolutionarypsychology literature (McCullough, 2008), is another one of these proximate mechanisms serving the ultimate advantage of reaping the many benefits of cooperation. Seen in this way, justice systems themselves can be understood as a type of ‘evolved’ system that is specialized to solve problems of cheating and cooperation. The notion that legal systems themselves evolved by processes akin to natural selection remains to be demonstrated, but whatever the mechanism, they do appear equipped to increase the scale by which group members can deter cheaters. This could be achieved by minimizing the costs of enforcement to any individual group member (Cushman, 2015). Notably, goals like ‘deterrence’ take on somewhat different meanings in the

evolutionary and legal accounts. The law attempts to protect a much larger and less well-defined social group than our punitive adaptations were designed to serve. Because of this mismatch, our evolved punitive psychology cannot necessarily be relied on to serve the explicit interests of society as a whole, and conversely, pursuit of such social goals may not necessarily satisfy our punitive desires, such as when the law is more merciful than what a victim demands. Evolutionary science alone is not sufficient to help us reconcile this tension, which hinges on normative judgments, but a deeper understanding of our evolutionary legacy brings such tensions to light.

From Explanation to Change An evolutionary psychological perspective can also help us understand the ultimate reasons for our behavior, so we can more lucidly decide whether these reasons are worth paying for and whether there are other ways of achieving our desired ends. By analogy, knowing that a fever is an adaptive response to infection can help us decide whether it benefits us most to take a medication that treats the fever symptoms or the underlying infection. Fever, of course, is not a perfect solution to overcoming an infection – in some cases, there might be other, more effective solutions – but, with some discomfort, fever usually and eventually gets the job done whereas treating the symptoms by suppressing body temperature could actually make the infection worse (Nesse and Williams, 2012). On the other hand, there are some adaptations that are clearly obsolete, like wisdom teeth that crowd the modern jaw. Similarly, knowing that human punishment motivations evolved to confer fitness advantages to members of a social exchange network, and knowing that it does this by employing retributive-emotion programs to cause individuals to behave in ways that facilitate deterrence and desistance of the offensive action


can help us evaluate whether these are worthy aims, and if so, whether our punitive motivations achieve these aims more or less effectively than other strategies, such as particular rehabilitative approaches that do not demand suffering. Are retributive sentiments more like a fever that, despite the discomfort, works pretty well most of the time, or are they more like an impacted wisdom tooth that’s better off pulled? We don’t know the answer to this question – whatever the answer, it is undoubtedly complicated – but it’s largely owing to evolutionary theory that we can even articulate the question. A richer understanding of the ultimate reasons for human punishment behavior could potentially inspire practical strategies for managing unwanted effects. For example, knowing that offenders can exploit relatively anonymous lifestyles in modern societies, reducing perceptions of anonymity in highcrime areas (e.g., via increased surveillance) could reduce crime, increase the quality of evidence to support criminal charges, and consequently make punishers less reliant on the use of heavy sanctions to achieve the same level of deterrence. Knowing that decision-makers might neglect the costs of the punishment unless those costs are made salient could bolster arguments for increased transparency about sentencing costs, including recognition of other ways the funds could be used (i.e., the opportunity costs of the punishment). Knowing that sentencing judgments may be primed by factors like fatigue and mood, countermeasures could be developed, such as protocols for randomizing defendants to docket schedules to ensure that particular types of defendants (e.g., if a court tends to schedule high-risk defendants last) are not systematically penalized by timedependent effects. The power of evolutionary theory to mobilize the law in ways that more effectively shape human behavior has been dubbed ‘the law of law’s leverage’ (Jones, 2000). If we think of law’s proscriptions and threats of punishment as a lever by which society tries


to move its members away from antisocial or other destructive behaviors, then understanding the evolutionary pressures (i.e., the fulcrum) shaping those behaviors may tell us how long our levers need to be. Behaviors with deep evolutionary roots will be hard to move except with big levers. We’ve focused here on criminal sentencing, but evolutionary psychology might impact other areas of the law. This is not to say there is a one-to-one correspondence between evolutionary theories and particular legal reforms. The payoffs are not likely to be so direct. Instead, their value will be in constraining and inspiring plausible hypotheses about legally relevant behaviors including their triggers and inhibitors, by helping to identify any evolutionary roots of such behaviors. For instance, researchers have already discovered that ordinary people (like jurors) have significant trouble distinguishing between two of the criminal law’s four mental states – knowing and reckless (the other two are purposeful and negligent; Ginther et al., 2014; Shen et al., 2011). Examining the adaptive contours of mental-state attribution may help judges improve their definitions of these mental states. Understanding more about how different kinds of substances or diseases affect these mental states could also pay huge dividends in reforming the law’s traditional defenses to responsibility, including intoxication and insanity (Hoffman, 2018). Jury instructions – the written rules through which judges inform jurors about the legal rules they must apply to the case before them – are a fertile ground for evolutionary psychology-based improvements. Knowing how best to communicate complex principles to ordinary citizens, and the pitfalls that lie in wait, could substantially improve the truthfinding function of jury trials. Understanding more about human bias may help judges and lawyers identify biased jurors and/or inoculate them from the harshest effects of those biases. Insights about our irrational discounting behaviors could affect the way in which judges instruct civil jurors,



and lawyers argue to them, about future tort damages. Knowing that expert witnesses, too, are susceptible to social-cognitive biases, such as unconscious allegiance to the hiring party, could inspire the development of methods for controlling the experts’ access to this information, thereby improving the quality of the testimony on which guilt and punishment decisions may be based (Robertson, 2010; Wong et al., 2015). The potential for these insights to impact the law is not limited to courts and juries. They may even be more important at the front end of law as legislators consider new laws and regulators consider new rules and regulations. If the difficulty in distinguishing between knowing criminal acts and reckless ones ends up being insurmountable, informed legislatures may want to consider reforming the criminal law’s mental states. Likewise, as evolutionarily informed researchers learn more about those mental states, legislatures may consider changing the contours of some of the classic defenses to responsibility, such as intoxication or insanity. Similarly, a working knowledge of our time-discounting bias would certainly be important as legislators and regulators consider issues like usury rates, payday loans, and caps on future tort damages. Evolutionary psychology is likely to have significant traction in all these areas of the law because it informs our understanding of human nature, and law is applied human nature.

ACKNOWLEDGMENTS We thank the Cooperation, Conflict, and Cognition lab members, especially Sharlene Fernandes, Corey Allen, and Justin Thurman, for helpful comments.

Notes 1  The first part of this section was adapted from Hoffman (2018).

2  We use the term ‘first-party punishment’ loosely since punishment in an ultimate sense implies the delivery of costs that come at the expense of the receiver, and it’s not clear that conscience, guilt, and shame are best understood this way. Another way to think of these mental states is in proximate terms, as programs that regulate how we conduct ourselves and treat others (see Peterson et al., 2010).

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12 Evolutionary Psychology and Incarceration Alina Simona Rusu

INTRODUCTION Literature in the field of criminal justice ­frequently places incarceration (i.e. the state of being confined in prison) in the context of the normative nature of human activities and institutions (Ward and Durrant, 2011). A recent analysis of incarceration systems at the international level (Mauer, 2017) points out that a nation’s incarceration rate is often interpreted as the degree of civilization of that nation, as well as the degree of punitiveness the nation is willing to impose in the process of isolating specific members from the broader community (i.e. in the direction of public safety). While several forms and levels of imprisonment exist, incarceration is often considered the end product of individual or societal failure (Mauer, 2017). In line with this consideration, international conventions and policies, such as the European Convention on Human Rights, state that no individual shall be deprived of liberty unless

certain conditions are met, such as the necessity to prevent the committing of an offence or fleeing after having done so (Macovei, 2004; Mauer, 2017). Analyses of criminal justice systems across human societies indicate that incarceration today involves not only the isolation of individuals, but also their rehabilitation through professionally designed interventions and educational programs. Features of violations of social rules are considered to meet the input conditions for the development of mechanisms designed to respond to inter-individual exploitation (Petersen et al., 2010, 2012). Hence, criminal justice institutions can be interpreted in the context of evolved counter-exploitation strategies. Two categories of counter-exploitation strategies (i.e. punishment and rehabilitation) are addressed in this chapter in the context of evolutionary analyses of incarceration from the perspectives of incapacitation of offenders and of reparative interventions.



INTER-INDIVIDUAL EXPLOITATION AND COUNTER-EXPLOITATION STRATEGIES Interactions with conspecifics in social species afford not only fitness opportunities but also potential costs, which can sometimes include even the death of individuals subjected to severe violence (e.g., Kurzban and Leary, 2001). Acts of exploiting conspecifics for self-benefits related to survival and reproduction have been documented in many social species, including humans, as well as evolved strategies designed to counter these exploitation efforts (e.g., Duntley and Buss, 2004; Petersen et  al., 2012; McCullough et al., 2013). Punishment and behaviors that resemble human social exclusion, i.e., preventing particular individuals from interacting with the group, have been studied in nonhuman species, such as lemurs, chimpanzees, and three-spined sticklebacks (e.g., Wilson, 1980; Goodall, 1986; Wrangham, 1987; Kurzban and Leary, 2001). Kurzban and Leary (2001) interpret these types of behaviors in nonhumans and humans within the frame of discriminate sociality, noting different forms that have emerged due to different selection pressures. Several authors present and discuss several categories of counter-exploitation strategies, from the incapacitation of offenders to the combination of incapacitation and rehabilitation, as well as the development of prison settings with respect to the needs and welfare of human beings. Petersen et al. (2012) point out that the evolutionary literature on exploitation and its application to modern justice should take into account the counterexploitation strategies beyond punishment and note that the small-scale social world of our ancestors – with dense social networks and high levels of dependency – should have selected not only for punitive strategies, but also for non-punitive reparative ones (Aureli and de Waal, 2000; Petersen et  al., 2010, 2012).

THE RECALIBRATION THEORY OF COUNTER-EXPLOITATION Starting from the idea that a major factor regulating the activation of reparative – rather than punitive – responses to exploitation/rule violation is the perceived social value of the perpetrator (the criminal’s social worth), an explanatory frame has recently emerged, i.e. the recalibration theory of counter-exploitation (Petersen et al., 2010). The authors offer the evolutionary prediction that the human mind spontaneously computes the magnitude of two distinct variables when confronted with exploitation: (1) the exploitation’s seriousness and (2) the exploiter’s association value; these variables are fed into motivational mechanisms regulating distinct aspects of strategies for countering exploitation (e.g., how severely we want to punish, how long we wish to incapacitate the perpetrator, how intense the social repair efforts will have to be; Petersen et al., 2012). Recent research demonstrates that the social decisions mentioned above depend upon the magnitude of an internal variable – a welfare tradeoff ratio (WTR) – which sets the weight the actor places on a specific person’s welfare relative to the actor’s own (Tooby et al., 2006; Tooby and Cosmides, 2008). Within this framework, Petersen et al. (2012) define exploitation as acts expressing too low a WTR (relative to some baseline) by inflicting a cost on the target for too small a benefit to oneself. From the perspective of this definition, evolution should have selected for counter-exploitation strategies designed to recalibrate the exploiter’s WTR in the direction of decreasing the number of exploitive acts they commit in the future (Sell et al., 2009; Petersen et al., 2012) and of inducing the exploiter to place greater weight on the welfare of others in the future (e.g., Clutton-Brock and Parker, 1995; de Waal, 1996, cited in Petersen et al., 2012). The efficacy of the reparatory functions of punishment appears to depend upon the ability of the punisher to monitor the exploiter’s


behavior (Petersen et  al., 2012). From this perspective, prisons might have evolved as systems for monitoring the behavior of the exploiter, but also a way for the offender and for the society (‘the collective punisher’) to interact through reconciliation and other forms of reparative gestures.


Petersen et  al. (2012) propose that the difference between the minimally acceptable WTR and the WTR expressed toward the victim reflects the intuitive concept of an exploitive act’s seriousness. In light of recalibration theory, the information on the seriousness of an offense should be reflected in the intensity of the reaction to regulate the WTR of the perpetrator toward potential victims (i.e. punitive or rehabilitative reaction). Petersen et al. summarize from an evolutionary point of view the criminological literature addressing the seriousness of crime. It appears that the seriousness of crime is set by the crime’s physical or symbolic level of harm and that the rank orderings of the seriousness of crimes are stable across cultures, especially with regard to crimes causing physical harm (Stylianou, 2003; cited in Petersen et al., 2012). Petersen et al. point out that, although less explored, there are data suggesting that the same crime is seen as less serious when performed for a large gain in inclusive fitness, such as stealing food for one’s family, defending relatives, etc., than for a small individual gain (Rossi et  al., 1985). The authors suggest that these findings might indicate that intuitions about crime seriousness track welfare tradeoffs rather than harm alone (Duntley and Buss, 2004; Petersen et al., 2012).

the exploiter’s behavior violates social ­obligations (Vangelisti et al., 1991), reminding the exploiter of the favors done for them in the past (Sell et  al., 2009) or signaling a wish for future prosocial interactions (Fujisawa et al., 2005; Petersen et al., 2012). The reparative gestures convey information to exploitive persons that they have underestimated the true magnitude of the harm inflicted, underestimated the true value of the relationships jeopardized, or overestimated the gain to the exploiter; it is argued that such information targets WTR circuits that are distinct from those targeted by punishment (Petersen et al., 2012). Petersen et al. (2012) argue that because different factors regulate whether specific actions are adaptive in private versus public contexts, evolution should have selected for cognitive machinery designed to compute a monitored WTR to govern decisions when one’s actions are likely to become known to those who will be affected by them, and a different cognitive machinery to govern decisions when one’s actions are not being monitored. It is argued that reparative gestures aim at up-regulating the exploiter’s intrinsic WTRs, such that they inflict less harm in the future even when not being monitored (Petersen et  al., 2012). In line with this, research on emotions indicates that reparative interventions, when successful, have the potential to elicit guilt in exploiters (Harris et al., 2004), which subsequently up-regulates their cooperativeness (Harris, 2003; Petersen et al., 2012). Several studies support the idea that feelings of guilt correspond specifically to an up-regulation of the exploiter’s intrinsic rather than monitored WTR (Tooby and Cosmides, 2008; Petersen et al., 2012).

The Perceived Social Value of the Offender

Decision to Punish and/or to Repair

Research on reparative gestures reveals that they usually involve demonstrations of how

The dual character of the incarceration system, i.e. isolation and rehabilitation, is supported

The Exploitation’s Seriousness



by the four-phases frame of analysis of the evolutionary psychology behind the mechanisms of social justice institutions (Ward and Durrant, 2011): phase 1 refers to the inquiry into the nature of rehabilitation, which can be seen as a capacity-building guided process aiming to assist and shape the capabilities of the incarcerated offenders in making better prudential and moral choices; phase 2 consists in the identification of the features of an effective and ethical rehabilitation process, such as the offenders’ inherent dignity, capacity for independent functioning, and increase in well being, all within the direction of reducing the risk that these individuals will commit further crimes; phase 3 refers to asking questions about the relevance of evolutionary approaches to human functioning and behavior for the process of incarceration and of reintegration, in terms of understanding that the strategies of providing a ‘good life’ for offenders and other members of society should be based on realistic views of human nature and on the understanding of the causes of criminal behavior; phase 4 refers to the question of whether an evolutionary psychological explanation provides the best theoretical guidance on understanding the function of incarceration systems and of communalities of these systems across the nations of the world. In their comprehensive analysis of the decisions to punish or to repair in the context of an evolutionary psychological analysis of modern criminal justice, Petersen et al. (2012) conclude that, across a range of different types of crime and across two different countries (i.e. the United States and Denmark), the preferences of the participants for rehabilitation over punishment of the offenders were regulated by the perception of the social value of the offender, independently of their perception of the severity of the crime. However, the perception of the seriousness of the crime has regulated the intensity of preferred sanction (Petersen et al., 2012). The perceived association value of the offender was significantly affected by

several experimentally manipulated cues (i.e. evolutionarily significant cues in the context of human social functioning), such as the criminal history of the offender, the offender’s status as in-group or out-group member, and the offender’s expression of remorse (Petersen et al., 2012). One of the conclusions by the authors is that their results support the hypothesis that the mind’s design for decisions to respond to offenders (exploiters) is based on two distinct information-processing channels, i.e. one for computing the seriousness of the crime and the other for computing the criminal’s association value (Petersen et al., 2012). While nowadays there is little chance that an individual’s well being will be directly affected by the state’s decision to punish or to rehabilitate a specific offender, a strategic social calculus in terms of this decision might operate in intimate social settings, suggesting that this might mirror the adaptive problems faced by our hunter-gatherer ancestors (Petersen et  al., 2012). In other words, the action of the selection pressures that have favored the mental designs that trigger reparative over punitive strategies in response to exploitive acts by individuals with potential social value might be reflected in the modern sanctioning institutions, including the incarceration system.

THE NICHE CONSTRUCTION THEORY APPLIED TO THE INCARCERATION SYSTEM Based on the four-phases model presented above, Ward and Durrant (2011) place the rehabilitation efforts of the prison system within the niche construction theory (OdlingSmee et al., 2003), which states that human beings partially engineer their environments and in this way contribute to downstream selection pressures, i.e. in the case of evolutionary functions of criminal justice from the perspective of niche construction, it is


assumed that greater community involvement in offender rehabilitation should encourage a higher investment by individuals in social norms and, further, that these individuals will be less likely to offend (Ward and Durrant, 2011). This idea is in line with the concept of rehabilitation applied to prison systems, which refers to normative processes that manifest at an individual level by assisting individuals to renounce criminal activity and construct socially desirable identities, and at the social level in terms of correctional policies directed at risk reduction (Ward and Maruna, 2007; Ward and Durrant, 2011). In other words, the evolution of modern incarceration systems might be considered an intentional social-intervention strategy, which should be analyzed by taking into account multiple ways of applying evolutionary theory to human behavior, such as human ethology, anthropology, sociobiology, memetics, and gene-culture co-evolution theory (Laland and Brown, 2002; Ward and Durrant, 2011). While one can assume that in the hunter-gatherer Pleistocene environment, the reaction of the group to an offender was probably a quick one in order to quickly resume everyday life activities, now there is a considerable social and economic effort in the direction of recalibration of interactions with offenders and reconstruction of their functional social identities. Niche construction occurs when organisms alter their environment through metabolism, activities, and choices, thus reconfiguring their relationships between their characteristics and the environment (Laland, 2007; Ward and Durrant, 2011). These alterations might reduce the selection pressures in the direction of enhancement of survival and reproduction. Examples of niche construction in humans are not only the products related to basic survival needs, such as houses, farming practices, heating systems, medical care, etc., but also the products addressing the development of social and cultural capital, such as technology products, books, and educational systems.


Odling-Smee et  al. (2003) describe three types of processes involved in niche construction: genetic processes, ontogenetic or developmental processes (individual learning within lifetime), and cultural processes. These processes are argued to result in the modification of physical and cultural environments and are implicated in the generation of three types of inheritance systems (Odling-Smee et  al., 2003): genetic inheritance, cultural inheritance, and ecological inheritance (i.e. the altered ecological niche). In a comprehensive analysis of niche construction theory in the context of offenders’ rehabilitation, Ward and Durrant (2011) direct special attention to the following types of inheritance: (1) culturally stored knowledge, arguing that this type of knowledge helps the incoming and current generations of humans not to repeat the errors made by the previous generations, and (2) ecological inheritance, which refers to changes in the environments and ecologies passed on to a new generation. According to Ward and Durrant (2011), such knowledge has the potential to offer greater flexibility for a species, as well as to gradually develop increased environmental control. In this line, the existence of incarceration systems across human societies, which function on similar rules and structured interventions directed to offenders, might indicate that this system is part of cultural and ecological inheritance at the species level. Another aspect that should be taken into account when placing the evolution of incarceration systems within the explanatory frame of niche construction theory (Ward and Durrant, 2011) is the existence of two basic types of niche construction: (1) inceptive niche construction, which refers to the original modification of the environment, and (2) counteractive niche construction, which refers to modification in an attempt to counteract a problem or a previous change. Several implications of niche construction theory, especially of counteractive niche construction, for the rehabilitation process of offenders (i.e. specific interventions with



offenders) are discussed in the literature, ­starting from elements of human behavior to the concept of extended cognitive system (Ward and Durrant, 2011). From the point of view of niche construction theory, human beings are culturally responsive animals, i.e. human behavior and socio-emotional capabilities can be shaped by ethical values and social norms that are imparted by social learning (Ward and Durrant, 2011). Hence, a broad range of behavioral options, as well as attitudes and proclivities of offenders, can be altered by interventions designed in the direction of socially responsible and meaningful lives (Clark, 2003; Sterelny, 2011; Ward and Durrant, 2011). Also, in the same direction of interpretation, it is considered that the fact that human beings can engineer their cognitive environments supports the existence of reparative interventions in prisons aiming to diminish the criminogenic cognitions and crime-supportive beliefs (Ward and Durrant, 2011). The concerted effort of society (social support) and professionals in the field of rehabilitation of offenders (e.g., psychologists, social workers, correctional staff, medical staff, etc.) points toward an extended cognitive system in relation to the evolutionary significance of incarceration. Specifically, Ward and Durrant (2011) suggest that, if one accepts the idea that human individuals utilize a combination of internal and external resources when involved in cognitive tasks, then it can be assumed that all the agents involved in the process of rehabilitation engineering of offenders are part of their extended cognitive system. In line with this, several authors indicate that a proper understanding of the role of cognition in causing and maintaining offending is dependent upon the fact that humans are socially embedded beings with a hybrid cognitive system, which consists of an integrated combination of internal and external components that enable problem solving (e.g., Clark, 2008; Menary, 2007; Ward and Durrant, 2011). In the context of incarceration, it is interpreted that the survival of offenders and the reflection on their offending-related problems while being

incarcerated does depend on the cognitive resources of others (Ward and Durrant, 2011). Another important aspect that should be taken into account when addressing the evolution of modern incarceration systems in the context of niche construction theory is the fact that humans, regardless of their incarcerationrelated status, are naturally inclined to seek certain goals, which are often called primary human goods (e.g., physical health, relatedness, subjective happiness, mastery; Ward and Maruna, 2007; Ward and Durrant, 2011). These primary goods or ‘natural desires’ (Arnhart, 1998) are considered markers of fitness or key components of well being; it is argued that they have their origin in human nature and have evolved through natural selection in the direction of establishing social networks favorable to survival and reproduction (Ward and Durrant, 2011). Primary goods are assumed to be linked to secure living that should allow the realization of potentialities specific to human individuals, such as states of mind, personal characteristics and experiences, states of affairs, etc. (Ward and Stewart, 2003). Additional to the primary goods, secondary goods or instrumental goods refer to the means of achieving primary goods (Ward and Durrant, 2011). Instrumental means could be considered both the offending behavior and the incarceration strategy: in the case of offending behavior, it is assumed that it can occur when individuals are trying to achieve primary goods in often destructive ways at individual and societal levels (Ward and Durrant, 2011), while in the case of incarceration systems, we can assume that restructuring interventions in prison are means of preventing further crimes in the direction of a secure living environment.

Effects of Incarceration: CrimeSuppressive and Criminogenic Consequences Definitions of prison are generally based on their functions related to the consequences of incarceration on individuals and society.


Several theories suggest that prison is ­crime-suppressive, while others suggest that prison can have criminogenic consequences (Harding et al., 2017). It is assumed that the crime-reduction effect is achieved through incapacitation, rehabilitation, and specific deterrence (Bushway and Paternoster, 2009; Harding et  al., 2017). The magnitude of any incapacitation effect depends on the offending of a comparison group of individuals who have not been imprisoned, and incapacitation effects occur only when individuals remain incarcerated. In contrast, rehabilitation and specific deterrence will exert their effects after release. It was also hypothesized that prison increases criminal offending through stigmatization and labeling effects, through social learning of pro-criminal attitudes, values, skills, and roles (prisons as ‘schools of crime’), and through prison’s effects on employment prospects (Harding et al., 2017). Recent studies indicate that returns to prison are primarily a product of post-prison community supervision rather than criminogenic effects of imprisonment, as many individuals sentenced to prison are trapped in the escalating surveillance and punishment of the criminal justice system; in other words, the rise in incarceration in the United States in the late 20th to 21st centuries was in part a self-perpetuation process resulting from the workings of the criminal justice system itself (Harding et al., 2017). Being sentenced to prison rather than probation increases the probability of future imprisonment dramatically, regardless of racial groups (Harding et al., 2017). Harding et al. (2017) suggest that probation sentences might be employed more frequently as an alternative to incarcerations. The cost savings associated with probation are large relative to the incapacitation effect of imprisonment and prison sentences do little to reduce/prevent criminal offending after release, relative to offending by probationers. Also, a significant proportion of incarcerated individuals are those that have been recently released from prison and have been re-imprisoned, i.e. prison’s revolving-door


phenomenon (Harding et  al., 2017). Most of the prison returns are due to a mix of new crimes and technical violations of the conditions of community supervision in the postprison period (Pew Center on the States, 2011, cited in Harding et al., 2017). Technical violations during the post-prison period are considered a key mechanism driving the prison’s revolving-door effect, rather than an artifact of the pre-existing differences between prisoners and probationers (Harding et  al., 2017). These results point toward the fact that for the reparatory function of the prison system to be effective, the rehabilitation programs and the monitoring of the former offenders should continue after their release, especially in the first years after, i.e. imprisonment for technical violations among prisoners is concentrated in the first two years post-release (Harding et  al., 2017). Even though the data indicate that there is a moderate incapacitation effect of incarceration, i.e. a prison sentence reduces the probability of a new conviction by 5–8% in the first year after sentence, the increased rate of post-release imprisonment due to technical violations supports a self-perpetuating process resulting from the functioning of the criminal justice system itself (Siegel, 2014; Harding et al., 2017).

Social Functioning in Prison: An Evolutionary Analysis Various correlates of social functioning in prison have been addressed in the literature, such as the personality traits of the inmates, psycho-affective vulnerabilities, sociofamilial context, behavioral management in detention, etc. (Picken, 2012; Tomar, 2013; Unver et al., 2013; Andelin and Rusu, 2015; Rusu, 2016). The aspects investigated so far reflect not only the high level of psychosocial heterogeneity of the prison population, but also the level of complexity of the process of planning efficient strategies for the prevention of self- and hetero-aggressive behaviors in detention.



To date, there are no studies concerning the evolutionary significance of the dimensions associated with the optimal dynamic of social interactions in prison environments, specifically their functional value for survival in this specific environment, in which the most probable resources to be controlled by the inmates are those directly related to their survival, i.e. social interactions that pose the highest risk to their quality of life. From an evolutionary perspective, prison environments represent a complex mixture of stimuli and selection pressures, bringing together individuals who are not familiar with each other and who have different social abilities and inclusive-fitness-related traits. Inclusive fitness refers here to the abilities and traits of an individual organism to survive and pass on its genes through direct reproduction and/ or by investing somatic effort and other types of resources in his/her relatives (Hamilton, 1964). Some of the survival abilities of the individuals facing incarceration are visible (conspicuous) to others, i.e. they can be easily evaluated by other inmates without necessitating long-term interactions, such as age, gender, voice, physical appearance, body mass, general health, access to social support (family and friend visits). Other survivalrelated abilities are less visible (hidden) at primary evaluation, requiring time and longitudinal social interactions (e.g., ability to recognize emotions in specific contexts, emotional-intelligence level, interpersonal dominance or submission tendencies, etc.). Both categories of abilities can be investigated as predictors for the behavior of individuals in detention, thus pointing out the need for their inclusion in the professional screening forms of newly convicted persons, especially when dealing with individuals with a known history of aggression (Rusu, 2016). Aggression is costly in the prison environment, not only at an individual level, but also at the level of organization and mobilization of the human and other resources of the prison. Although from an evolutionary

perspective, aggressive behavior is useful for self-defense and resources protection (Buss and Shackelford, 1997), it still remains one of the behaviors posing the highest risk on the quality of life of incarcerated persons, both at the physical and psychological levels, often associated with self-harm and suicide (Towl, 2003; Campbell, 2005). Violence is a major problem in settings with incarcerated persons, and it is frequently associated in the literature with deficits in the facial emotion decoding accuracy (Hoaken et  al., 2007). Emotion-identification errors, especially anger, are significantly associated with attribution of instrumental value to aggression in social contexts. Thus, a high level of aggressive attitudes and verbal aggression can be associated with misperception of anger even in its absence (Dodge, 1993). Also, individuals with a propensity for violence (who are frequently found in prison settings) have a higher probability of inadequately interpreting subtle social cues, such as facial micro expressions of emotions (Hoaken et  al., 2007). According to the social information processing model (Dodge, 1993; McNiel et al., 2003), errors in emotion decoding accuracy have the potential to affect individuals’ ability (especially of those predisposed to violent behaviors) to access and employ alternative adaptive responses to social situations. In the case of incarcerated persons, there are data indicating that the ability to recognize facial expressions of fear and anger is reduced in inmates with a higher number of arrests and with a history of aggression (Dodge, 1993). From an evolutionary perspective, the ability to detect facial expressions of emotions, in particular those associated with anger, is hypothesized to have enhanced the chances of survival and reproduction of our ancestors in environments of evolutionary adaptedness, anger being the main indicator of the intention to aggress against another individual (Grandjean et al., 2005; Hoaken et al., 2007). Another important factor for optimal social functioning in prison is the level of emotional


intelligence (EI) of the offenders. EI seems to be a relevant factor for accessing strategies of responding to social situations other than the primary responses such as quick and violent behaviors. The social-cognitive theory of power (Fiske, 1993) posits that the ability to perceive others, an important component of EI, plays an important role in social-functioning outcomes. According to this theory, individuals situated in positions of power tend to perceive others in a non-individualizing, stereotypical manner. On the other hand, less powerful individuals (i.e. submissive individuals) seem to be favored by individualization of others because they consider interpersonal relationships as depending on the more powerful individuals and on interaction partners, in general (Fiske, 1993; Goodwin et  al., 1998). Having access to emotional signals and decoding them correctly affords humans better chances of evaluating the attitudes and intentions of others (Hess et  al., 1988; Mayer et  al., 2008), of determining if social conflict is imminent (Ekman, 2009), and of adjusting interactive behavior in accordance with the perceived emotions. Consistent with the aspects presented above, it is recommended that, besides the standard psychological screening forms that are generally used in prisons, assessments of EI, emotion decoding accuracy, and individual inclusive fitness should be taken into consideration as biopsychological and evolutionary predictors of optimal social functioning in the prison environment (Rusu, 2016).

Costs of High Rates of Incarceration Several studies point out that imprisonment can be a profound life experience not only for the incarcerated persons, but also for their families and community (e.g., Mauer, 2017). These effects have been particularly related to high incarceration rates. Moderate rates of incarceration have a higher impact on crime reduction than high levels of incarceration,


which are associated with increases in crime; this effect is interpreted as the diminishing of informal social-control mechanisms that function to establish and reinforce social norms and create bonds among community and family members (Clear et al., 2003). Analyses of small human communities with high levels of incarceration indicate difficulties in family formation and child rearing (e.g., Braman, 2002), especially in those communities where most of the men have died or are serving in the military, but many are incarcerated. Hence, in terms of the direct fitness impact of incarceration at individual level, the imprisonment of men can considerably diminish the ability of women to find sexual and parenting partners in these communities (Raphael and Stoll, 2009). Also, literature indicates that imprisonment of parents can have unintended negative consequences on the well being of their children, often related to the placement arrangements of the children following parental incarceration (Johnson and Waldfogel, 2002). In terms of the financial costs imposed by incarceration systems, comparative analyses of cost savings between probation and incarceration indicate that the cost savings associated with probation are large relative to the incapacitation effect of incarceration (Harding et al., 2017). In the same study, Harding et al. (2017) revealed that the impact of prison sentences on reducing criminal offending after release is lower relative to the offending behavior of probationers; these results support the policy recommendation of using probation more frequently as an alternative to incarceration (depending on the seriousness of the offending) and more efficient planning of the post-prison parole supervision.

Emotional Burnout among Correctional Staff In terms of costs associated with the evolution of incarceration systems, evidence-based studies indicate that occupational burnout,



especially the level of emotional fatigue, is frequently reported among members of correctional staff, which can have negative consequences not only at the level of individuals, but also on the efficiency of the correctional organization (Hurst and Hurst, 1997; Griffin et al., 2012; Lambert et al., 2015). Job burnout is most commonly defined in the literature as psychological exhaustion and fatigue due to excessive workplace demands (Freundenberger, 1975 cited in Lambert et al., 2015). Maslach and Jackson (1981) have postulated three dimensions of job burnout: emotional exhaustion, depersonalization, and a reduced sense of personal accomplishment. Several studies indicate that the emotional dimension is the core component of burnout (Cordes and Daugherty, 1993; Maslach et al., 2012; Lambert et al., 2015) and that, compared to other professions from the category of helping others, correctional officers report significantly higher levels of emotional exhaustion as a dimension of job burnout (Maslach et  al., 2012). The high level of emotional exhaustion in correctional officers was associated with turnover intent, absenteeism, and increased health problems, which were particularly high in maximum-security settings and in prisons holding juveniles (Fox, 1982; Carlson and Thomas, 2006; Lambert et  al., 2010; Griffin et  al., 2012). Hence, it appears that working tasks in prison settings involve important fitness-related costs to the employers, which are often addressed in terms of prevention and management by a higher income, possibilities for early retirement and, in some institutions, access to psychological- and social-support programs. Lambert et  al. (2015) indicate in their investigation of the consequences of emotional burnout among correctional staff that the higher the level of education of correctional officers (e.g., college graduates), the lower the level of their emotional burnout; the findings are explained by the possibility that the officers with college degrees may have been given the opportunity to participate in decision making within the

institution. Correctional officers are usually the staff who are responsible for monitoring and implementation of programs planned by administrators and supervisory staff (Lambert et  al., 2015). Previous studies indicate that a conflict in personal belief system versus institutional goals contributed to increased levels of emotional burnout, which in turn was associated with less favorable attitudes to treatment (in the context of rehabilitation) and more favorable attitudes to punishment (Lambert et  al., 2015). Thus, one can conclude that emotional burnout of correctional staff represents an important variable to be considered when analyzing the selective pressures in the context of modern incarceration’s evolution. Recommendations are made by several authors regarding the necessity of exploring other variables of working place in prison, which are expected to play a role in correctional staff’s quality of life, support for treatment, support for punishment, turnover intent, and humane consideration of the needs of the incarcerated people. Another variable associated with lower levels of emotional burnout and greater life satisfaction in correctional staff was the opportunity to directly interact with the inmates in a positive manner (Lambert et al., 2015). When interpreting the behavior and attitudes of correctional officers toward inmates, Lambert et al. (2015) suggest that it is important to take into account that correctional officers tend to have most of the direct contact with inmates on a daily basis, so their perceptions of the goal of treatment versus punishment may be driven by the immediate circumstances of control rather than the longrange goals of the institutional plans.

Incarceration System from the Perspective of Helping Others In line with the data on the positive association between direct contact with inmates and greater life satisfaction in correctional officers (Lambert et  al., 2015), one can assume


that a higher level of awareness of the fact that working with inmates is one of the professions within the category of ‘helping others’ (i.e. structured forms of prosocial behavior) may help in preventing emotional burnout and increase the occupational motivation. A common definition of prosocial behavior refers to it as ‘a broad category of acts that are defined by some significant segment of society and/or one’s social group as generally beneficial to other people’ (Penner et al., 2005: 366). A more specific definition of prosocial behavior from the field of evolutionary psychology considers it as a form of behavior that brings fitness benefits to the recipient and diminishes the fitness of the helper (West et al., 2007). The costs of helping others are well documented in the literature, mainly in the contexts of caregiving and informal and formal volunteering, and they usually include psychological and physiological correlates of caregiver distress (Rusu, 2019). Brown and Brown (2015) point out that the studies addressing the stress associated with helping others often fail to distinguish between the stress associated with the behavior per se and the feelings about the recipients (e.g., compassion, sadness). Besides the costs mentioned above, recent studies suggest that helping others in need (i.e. unrelated individuals) can be associated with benefits, such as experience of positive states and improvements in health and psychological well being (e.g., Brown et al., 2009; Jenkinson et  al., 2013; Rusu, 2019). While helping others in need from the perspective of prosocial-behavior definitions implies an individual autonomous decision and intrinsic motivation, when it comes to the professions targeting the rehabilitation of offenders in prisons, the idea of helping others and the ways of doing so are imposed by the institutional and society rules, leaving most probably little place for the intrinsic motivation to occur. Therefore, we consider that in order to increase the rewarding value of the prisonrelated professions, more attention should


be offered to the prosocial aspects of these professions. One proposed action would be to include a learning objective in the training curricula of the correction officers on the neurobiological mechanisms and substrate of successful human social interactions, such as offering and receiving help from others in situations of need. For example, several recent investigations indicate that dopamine is one of the most commonly suggested candidates for the explanation of ‘helper’s high’ (Luks, 1988), which is described in the literature as a sensation of pleasure and subjective happiness associated with helping unrelated others in need (Krach et al., 2010; Rusu, 2019).

CONCLUSION The purpose of incarceration, i.e. whether to rehabilitate or punish offenders, is still a subject of debate not only within the criminal justice system itself, but also among members of society. In this chapter, incarceration is analyzed from the perspective of recalibration theory of counter-exploitation (Petersen et al., 2010, 2012), which is based on the evolutionary prediction that, when facing exploitation, the human mind spontaneously computes the magnitude of two variables: (1) the exploitation’s seriousness and (2) the exploiter’s association value. It is suggested in the literature that evolution should have selected for counter-exploitation strategies designed to ­ recalibrate the exploiter’s welfare tradeoff ratio (i.e. a variable that sets the weight the actor places on a specific individual’s welfare relative to the actor’s own) in the direction of decreasing the number of exploitive acts in the future (Sell et al., 2009; Petersen et al., 2012). In line with this, modern prisons might function as a monitored strategy of welfare tradeoff ratio manipulation or adjustment, combining punishment and reparative actions in the direction of preventing future harm to society and up-regulation of the cooperativeness of the offenders.



The incarceration system is also discussed within the frame of niche construction theory, specifically the ways in which interactions with offenders are designed not only with the purpose of their incapacitation, but also in the direction of assisting them in renouncing criminal activity and in constructing socially desirable identities. Also, the chapter presents the idea that the concerted effort of society (social support) and professionals in the field of rehabilitation of offenders (psychologists, social workers, correction officers, etc.) could be interpreted as an extended cognitive system in relation to the evolutionary significance of incarceration. In terms of fitness-related analysis, incarceration imposes costs both on the offenders (e.g., incapacitation due to imprisonment, violent interactions in prison, negative consequences on the well being of their children and family) and on the correction staff (e.g., emotional fatigue, occupational burnout, turnover intent). Hence, one can conclude that the two main functions of the incarceration system (i.e. punitive and reparatory) are continuously challenged by selective pressures that are both external ones (i.e. system-independent, such as financial crises in the society), but also internal ones, including the system itself.

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13 Evolution and Punishment Anthony Walsh, Cody Jorgensen, and Jessica Wells

INTRODUCTION In the opening words of The Scarlet Letter, first published in 1850, Nathaniel Hawthorne wrote: ‘The founders of a new colony, whatever Utopia of human virtue and happiness they might originally project, have invariably recognized it among their earliest practical necessities to allot a portion of the virgin soil as a cemetery, and another portion as the site of a prison’ (1879: 1). Hawthorne’s words are a reminder of two things we cannot avoid – human mortality and depravity, and that we must make provisions for both. We sadly commit our departed loved ones to the ground for obvious reasons, and we gladly remove miscreants from our sight for reasons just as obvious. It is beyond doubt that there are times when we must set certain people apart from the rest of us because they have demonstrated their inability to live by the agreed-upon norms of acceptable behavior. When we do this we are doing it against the will of the person being removed, and thus

we are expressing censure and community disapproval of his or her actions by inflicting punishment upon him or her. Of course, prisons are a relatively modern invention, but we have always retaliated in some way against those who have offended us. We see this retaliatory aggression in almost all sexually reproducing animals when conspecifics ‘cheat’ (signal cooperation but fail to be forthcoming). A classic example is that of vampire bats who freeload on blood donation. Bats who fail to find a blood meal on a given night will have regurgitated blood donated to them by other members of the group. The tendency is to share blood with those who have previously shared with them, thus returning the favor. Failure to reciprocate usually results in the original benefactor withdrawing future acts of sharing (Wilkinson, 1990). So even bats have some built-in motivation to retaliate punitively against norm breakers. From a scientific perspective, any emotion or behavior that is shown to be as universal as


the urge to punish must have an evolutionary history. Natural selection is a powerful positive feedback process energized by differential reproduction. If a genetic mutation results in the design (morphological, physiological, or behavioral) of an organism that allows it to out-reproduce other conspecifics, it will eventually become more common in the population and we then say that the design change has been selected for. Over many generations, the design change will spread until it goes to fixation in the population; that is, all members of the species have it. Cosmides and Tooby (1994: 328) liken natural selection to Adam Smith’s ‘invisible hand’ whereby unobservable market forces (‘natural selection’) fueled by millions of people seeking their self-interest (‘survival and reproduction’) move the supply and demand of goods (‘genetic polymorphisms’) in a free market (‘the environments of evolutionary adaptation’) to reach market equilibrium (‘genetic fixation’) automatically and without any intention or foresight. The consequences of punishing norm violators must have been positive with respect to the twin goals of all life – survival and reproduction. It is important for all animals to be motivated to do things that are vital in the pursuit of these goals. To provide that motivation, nature has provided us with neural mechanisms that reward us with pleasurable feelings when we do thin