From Hand to Handle: The First Industrial Revolution 9780199604715

Table of contents :
Cover......Page 1
Contents......Page 8
List of Figures......Page 10
List of Tables......Page 14
Introduction: An Enigmatic and Anonymous Revolution......Page 16
1. What Is Combinatorial Evolution?......Page 30
2. Neural, Cognitive, and Anatomical Foundations......Page 48
3. Tools for Learning......Page 90
4. Something New from Something Old......Page 128
5. The Invention of Hafting......Page 192
6. After the Revolution......Page 258
7. A Revolution without Heroes......Page 292
Appendices......Page 298
Bibliography......Page 310
B......Page 366
F......Page 367
H......Page 368
L......Page 369
P......Page 370
T......Page 371
Z......Page 372

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FROM HAND TO HANDLE

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From Hand to Handle The First Industrial Revolution

LAWRENCE BARHAM

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Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries # Lawrence Barham 2013 The moral rights of the author have been asserted First Edition published in 2013 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2013942449 ISBN 978–0–19–960471–5 Printed and bound by CPI Group (UK) Ltd, Croydon CR0 4YY Links to third party websites are provided by Oxford in good faith and for information only. Oxford disclaims any responsibility for the materials contained in any third party website referenced in this work.

Acknowledgements This book was written with the support of an Arts Humanities Research Council Fellowship in the autumn of 2011, which followed a semester of research leave from the University of Liverpool in the spring of 2011. To both organizations I am grateful. There are many people to thank for their contributions to this book. In no particular order they are Sophie Bowness of the Hepworth Estate, Joanna Ostapkowicz (National Museums Liverpool), Elin Borneman (Pitt Rivers Museum, Oxford), Matthew Tocheri, Gabriele Zipf, and Robin Gerst (Lower Saxony State Service for Cultural Heritage, or NLD), Georg Meyer, Alfred Pawlik, Steve Rosen, Avi Gopher, Nick Taylor, Veerle Rots, John Whittaker, Dietrich Stout, Karl Lee, Dora Kemp, Kathryn Arthur, Mark Roberts, Matt Grove, Matt Pope, Ryan Rabett, Huw Barton, Sandra Mather, John Gowlett, Chris Stringer, Emiliano Bruner, and Tom Schoenemann. A special thank you goes to Natalie Uomini for your comments, especially on Chapter 2, and for your infectious enthusiasm for the project. Hilary O’Shea and Taryn Das Neves at Oxford University Press have been supportive from the start, and patient. Richard Mason’s diligence as my copy-editor is acknowledged with gratitude, as is Gail Eaton’s careful proof-reading. Kizzy Taylor-Richelieu managed the production process impeccably. Thank you all. This book would not exist without Mary Earnshaw—she transformed my disappointment on receiving the news of a failed grant bid into the idea for this book. She, more than anyone else, has helped bring it to completion, and in so many ways. Mary, I promise not to put you through this again! And, ‘more than that’. Lawrence Barham University of Liverpool October 2012

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Contents List of Figures List of Tables Introduction: An Enigmatic and Anonymous Revolution

ix xiii 1

1. What Is Combinatorial Evolution?

15

2. Neural, Cognitive, and Anatomical Foundations

33

3. Tools for Learning

75

4. Something New from Something Old

113

5. The Invention of Hafting

177

6. After the Revolution

243

7. A Revolution without Heroes

277

Appendices Bibliography Index

283 295 351

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List of Figures 1 Components of a hafted knife.

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2 The nest of the red-headed weaver bird (Malimbus rubriceps).

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2.1 (a) Anatomical areas of the left-hemisphere cerebral cortex, including numbered Brodmann areas (BA), main lobes and fissures; (b) the sub-cortical structures of the limbic system.

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2.2 Cortical areas involved in tool use and speech.

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2.3 The human thumb is long relative to our other fingers as seen in this comparison of the hands and digits of the apes.

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2.4 The power grip used to hold a handle.

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2.5 The precision pinch grip.

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2.6 Endocranial morphology of fossil humans and an australopithecine reconstructed from digital endocasts.

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2.7 The evolution of human brain size in the genus Homo.

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2.8 Boxgrove (Sussex) flint scatter typical of a right-handed knapper.

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2.9 Using the teeth as a clamp for holding and pulling taut materials for slicing.

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3.1 The interplay of social variables that make up the unique cognitive and ethical structure of hunter-gatherer societies.

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3.2 A twelve-month-old Aka girl learns to use an adult tool—the machete.

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3.3 The evolution of human life-history stages.

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4.1 Evolutionary tree showing the geographical and chronological distribution of human species.

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4.2 Location map of sites discussed in Chapter 4

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4.3 Long-term climate trends in the Pleistocene.

130

4.4 The spread of glacial-stage ice sheets on the distribution of vegetation zones across Europe.

133

4.5 The distribution of vegetation across glacial-stage Asia.

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4.6 The expansion of Africa’s deserts and the fragmentation of its tropical forests with glacial-stage conditions.

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List of Figures 4.7 Rick Potts’ model of variability selection as a system of interconnections between climate, landscapes, human culture, and genes.

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4.8 A late Acheulean hand-axe from Kathu Pan, South Africa.

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4.9 A late Acheulean cleaver from Kalambo Falls, Zambia.

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4.10 A small late Acheulean hand-axe from Boxgrove, England.

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4.11 A precision grip minimizes the risk of cutting the hand.

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4.12 Preparing a core to produce a large flake.

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4.13 A Victoria West core from South Africa.

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4.14 Blades from Qesem Cave, Israel.

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4.15(a) Making fire with a spindle (b) close-up of charred hearth board.

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5.1 Loadings and stresses applied to the joint of a scraper, knife, adze, and piercer during use.

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5.2 Basic types of hafts.

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5.3 A close-up view of the hafting of a heavy stone maul to a wooden handle.

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5.4 A pick with a juxtaposed joint.

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5.5 Location map of sites mentioned in Chapter 5.

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5.6 (a) A drawing of the two surfaces of the stone artefact from Quneitra, Israel (b) reconstruction of the hafting arrangement of a scraper from Quneitra, Israel.

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5.7 The double-haft zucano scraper and the single-cleft haft tutuma scraper as used by the Gamo of Ethiopia.

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5.8 A tapered and basally thinned (fluted) Folsom point.

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5.9 An array of backed flakes and blades from Mumbwa Caves, Zambia.

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5.10. The stone flakes with tar residues from Campitello Quarry, Italy.

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5.11. A replicated hafted core-axe from Sai Island, Sudan.

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5.12. A thick retouched spear point from the site of La Cotte de St Brelade, Jersey (United Kingdom).

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5.13. An asymmetrical pointed artefact (quartz) from the site of Twin Rivers Cave, Zambia.

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5.14. Three views of a possible ‘handle’ made of the trunk of a fir (Abies alba) from the site of Schöningen 12, Germany.

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6.1 The location of sites mentioned in Chapter 6.

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6.2 Potential independent centres where hafting was invented.

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List of Figures

xi

6.3 The atlatl (or spear-thrower) with dart about to be launched with an overhand throwing motion and a bent-knee posture.

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6.4 A replica of an English longbow.

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6.5 Replicated arrangements of Howiesons Poort microliths.

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6.6 (a) A hafted sting-ray spine from Niah Caves, Borneo, with (b) details of hafting traces.

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6.7 (a) A sprung snare trap, and (b) a deadfall trap.

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6.8 Model showing the linked impact of the invention of mechanical propulsion devices on population growth, social learning, and rates of innovation.

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6.9 Estimate of human population growth over the past 160,000 years.

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APPENDIX A2.1 The orbital drivers of glacial-interglacial periodicity are shown along with their periodicities: eccentricity (100,000 years), obliquity (41,000 years), and precession (22,000 years).

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List of Tables 4.1 The actions and understandings needed to make a thinned biface using a soft hammer made from an organic material.

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5.1 The actions and understandings needed to make a hafted tool.

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5.2a A cross-tabulation of haft types with artefact types.

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5.2b A cross-tabulation of the number of technounits with artefact type.

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5.3 The ‘hierarchy of certainty’ of the earliest evidence for hafting in the archaeological record.

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Introduction: An Enigmatic and Anonymous Revolution This book is about a revolution that took place so long ago that no one knows just when, where, or how it happened. We can’t even be sure which human species was responsible, but we are all still living with its consequences. It was gradual, a non-event for those involved, but it transformed the social and economic lives of our species. Without it we could not have survived in arctic environments nor landed on the moon. Archaeologists are uniquely placed to see this profound change in the making and chronicle its unfolding. That’s not because we are uniquely gifted with hindsight, but because we take a long view, because we are trained to detect faint traces of the new and to follow their development, or witness their extinction. In this case, the new took hold, became the norm, and is now lost to view through familiarity. But its legacy is to be found in everything we make and use today. This grand ‘revolution’ was an innovation in tool-making that in its simplicity seems obvious, if not trivial, until placed in the context of what went before and what came after. Until roughly 500,000 years ago all tools were made of single materials (bone, wood, stone, antler, ivory, and so on) and hand-held. A stone knife was just that—a sharp cutting edge of stone but without a handle. After 500,000 years ago, some tools were made with the addition of handles or shafts that were attached to a working edge. (The join between the two is what I call the haft and the process of planning and making such tools is hafting; Fig.1). Hafted tools were not only more efficient to use but ultimately improved their makers’ chances of survival. The knife edge, now bound into a handle, was easier to hold, allowed the user to apply

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Blade

Binder Glue Haft Handle

Fig. 1. Exploded diagram showing the components of a hafted knife, which in this example include an adhesive added to the joint or haft before the blade is inserted and the whole joint squeezed tightly using a rawhide binding. Each component represents separate areas of expertise that are brought together to make a working whole, and the result embodies the combinatorial principle.

extra force with less effort and protected the hand from cuts, thus reducing the risk of infection. The same advantages applied when binding a stone axe blade to a handle, a scraping edge to a handle, a drill bit to a handle, and so on. A sharp stone tip attached to the end of a shaft created a more effective hunting weapon than a sharpened wooden spear alone. Almost any activity that involved cutting, scraping, chopping, and piercing could be made more effective by incorporating a handle or shaft with a basic tool. These actions were, and still remain for most of humanity, part of our daily routines for getting and preparing food, not to mention meeting other basic wants such as shelter, warmth, and security. That’s the economic consequence of the hafting revolution: it made the quest for food more reliable and productive. From an evolutionary perspective, it enhanced the rates of survival of its makers and their offspring compared with those who lacked this innovation. But there is more to this revolution than a full stomach—the mind was involved as well. This innovation involved considerable planning based on expert knowledge of the properties of the various raw materials that would be incorporated into a working tool. (Hafting isn’t just sticking two parts together to make a tool, as we will see.) Each component must be considered in terms of its suitability to do the job at hand as part of a working whole, not just on its own. The

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hafted knife typically involves the cutting edge fitted into a wood or bone handle with another organic material (e.g. sinew or twine) used as a binder to squeeze the two together tightly. The binder also needs to be able to withstand the pull or tension created by the slicing movement of the knife. A filler may be added to minimize movement of the blade in the haft. The knife blade needs to be sharp, of course, and shaped to fit the haft. The haft needs to hold the blade securely without splitting during use as well as being a handle for the user to hold. Each component has its own distinctive properties and stress tolerances that the maker knows from experience. That is engineering. But the real innovation that underpins hafting lies in envisaging the final form of the tool as an integrated whole, and that level of imagination was arguably something new in human evolution. Before hafting, tools were designed to work as an object of just one part, such as a stone flake with a sharp cutting edge, and held in the hand. Our early ancestors understood well the properties of stone, bone, wood, and other materials used to make tools for cutting, scraping, piercing, and all the other tasks of daily life. The inventors of hafting drew on that wealth of experience.

WHAT YOU SEE IS NOT WHAT YOU GET Earlier hand-held tools had been made by a process of reducing and shaping materials for use, but now the process became additive, with components combined into a tool of multiple working parts (a composite tool). The concept of ‘combinatorial evolution’ as developed by complexity theorist W. B. Arthur (2009) neatly encapsulates the capacity for rapid innovation and the potential for endless novel combinations inherent in composite technology: tools beget tools in an almost self-generating process. The process is both incremental and radical; it builds on existing knowledge enhanced through experience, but it encourages and reinforces creative solutions founded on new combinations of components which in turn generate supporting technologies. The making of a car involves the manufacture and assembly of multiple parts each with their own production networks from raw material to finished product. And occasionally something very different comes along that changes our habits of tooluse and how we think about technology generally. The Internet and

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its offspring technologies, like the smartphone, are the most recent descendants of combinatorial evolution. The invention of hafting marks its inception, and we can see the principle at work in what to us seems the most simple of tools. To make our hafted knife in Figure 1 a hafted adze was used to shape the handle, a separate hafted knife was used to cut the tendons from a carcass to make sinew bindings. These strips of sinew would be applied while still wet and wrapped around the join where they would shrink and tighten the bond between the haft and blade. The stone blade had to be sourced from a material that fractured in a predictable manner and which produced a sharp edge. Perhaps the stone had to be quarried using antler picks, or transported some distance in a skin bag before being reduced in size using a stone hammer of an effective hardness and shape. The knife blank might need to be further shaped by thinning and this would involve a softer hammer of bone or wood of the right size, weight, and elasticity that thinned the blade without breaking it. Producing the filler involved collecting a sticky plant resin, letting it dry, then grinding the resin and mixing it with water before heating it to the right consistency, then adding some ground charcoal or sand to help it dry without cracking. A container of some kind would be needed to hold the mixture while it was heated and then applied with another tool, such as the tip of a twig chewed or beaten to form a brush. The fire used to heat the mixture itself involved the application of separate chains of knowledge, including the understanding of which woods make a good fuel, the need to generate heat through friction, or how to curate an existing source of fire. Once the tool was made then the maker had to consider how to extend the use-life of the cutting edge. The knife edge would become dull with use and would need resharpening. Could that be done with the blade in the haft or should the haft/binder/filler combination be designed to allow for the ready removal of the cutting edge and its repair or replacement? Clearly many decisions need to be made in advance of creating what appears to be a simple knife. There is, then, a significant cognitive foundation to the planning, making, and using of hafted tools. That foundation requires a good working memory linked to neural structures and networks that integrate decision-making with the coordination of eye, hand, and body movements. Conceptually and practically, constructing a hafted tool involves imagining and

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executing a sequence of events that collectively lead to a functioning whole made from interacting parts. That hierarchical or step-wise process resembles the forming of sounds into words and words into meaningful sentences based on rules of grammar and syntax. The link between tools and language is more than just a convenient analogy; the two activities share neural structures in the brain. Brain-imaging research and an improved understanding of the importance of memory in planning and decision-making give us a neural baseline for estimating when the capacity to make complex tools evolved. By looking at the fossil record of brain size and shape (see Chapter 2) we can discover when the neural capacity for making these complex tools was in place, but it is only by looking at the archaeological record (see Chapter 5) that we can see when the technology was actually applied.

JUST IMAGINE The ability to conceptualize an object and its future actions has its parallel in our ability to create stories peopled with fictional beings living imagined lives. Language allows us to share these imaginings with others, but that sharing depends on our understanding of others as being similar to ourselves; like-minded in the sense that they too have beliefs and knowledge and are independent agents. This ‘theory of mind’ is most developed in the construction of shared abstractions such as kinship rules, art, and religion. A hafted tool isn’t the equivalent of a belief in a god, but its initial conception required a level of imagination—a vision of something new. That something new, when made and tried, might need a new name to distinguish it from other objects in use. Was the first hafted knife the same thing conceptually as the hand-held knife of old? Naming expands not just our vocabulary but also our perception of the world. Objects can become metaphors or symbols of other realms of behaviour and meaning: consider the hammer and sickle, the Star of David, the Cross, and the scimitar. This realm of speculation that links the advent of composite technology with a developed theory of mind can’t be tested, but it shows the potential linkages between tools, cognition, and our social lives. Humans learn to craft tools from their parents, peers, and elders. That extended social network of learning distinguishes us from other tool-using animals which either have more limited networks

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From Hand to Handle

or genetically programmed patterns of tool-making. Take for example the nest-building behaviour of the red-headed weaver bird (Malimbus rubriceps) in Uganda. The male exhibits what appears to be a form of composite technology. To attach the long pendulous nest to a branch (Fig. 2), he first selects living twigs that will form the superstructure of the nest. These are stripped of their leaves then detached from their branch, and the detached twig carries with it a predetermined length of bark that will be wound around the home branch (Crook 1963). Before detaching the twig the male scores the point near the base of the twig where the bark strip will detach, ensuring it is the correct length for the job. As the bark dries it forms a tight bond, securing the twig to the branch. Other twigs are similarly selected and detached with a standardized length of bark tassel which is used to bind each to another to make a strong structure that can withstand high winds. The male weaver bird is technically using a hafting technology, but what differentiates this behaviour from that of human tool use is one of inheritance. The bird is apparently born with this nest-building

Fig. 2. The nest of the redheaded weaver bird (Malimbus rubriceps) is a complex construction held together by the use of carefully shaped strips of bark. (The intricate weaving pattern is shown in detail to the right.) This is an example of a hafting technology used by a non-human species, but this behaviour is restricted to nest-building and presumably inherited genetically as well as learned by observation. (After Crook 1963)

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expertise, and though its skill may improve with experience it does not need parental or peer guidance to learn the basic craft. Such standardized behaviour offers little scope for innovation in response to quickly changing circumstances. Humans, however, learn from observation, imitation, and teaching by others. Language reduces ambiguities in learning and enables us to share our expertise and solve problems communally, which gives human cultures their potential for rapid change, if needed or desired. Childhood learning lies at the core of the distinctively human ability to retain and transmit innovations over many generations. Our ability to accumulate and build on learned behaviours forms the basis of long-term cultural change, in the process known as the ‘ratchet effect’ (Tomasello 1999). Some social contexts are more conducive to ratcheting-up the process of cultural change than others, especially those that give children time to learn from people of differing ages and experiences. As children we are dependent on others for food, protection, and learning how to behave appropriately. The case is made here that our long childhood evolved in tandem with brain size and the need for extending social care to mothers and their dependent offspring. The nucleus of a distinctive form of human society emerged from this interplay of biological and social variables. Hafting is argued to be essentially a social technology, one that encouraged cooperation in its learning, making, and use. It brought individuals into close contact, enhanced empathy and understanding of others’ states of mind. Hafting also contributed to greater group cohesion by enabling greater task specialization. The basic division of labour seen in many hunter-gatherer societies between males hunting and women gathering meant that food-getting became more efficient, but also meant that food sharing became imperative for collective survival. Hunting is risky and often unsuccessful, but where gathering is possible it provides a reliable source of nutrition. In high-latitude environments where plant foods are scarce, the division of labour shifts towards a greater emphasis on hunting by men and greater involvement of women in essential supporting roles, such as maintaining tools and processing foods for storage during lean winter months. Hafting contributed to the efficiency of these separate tasks and in doing so changed us into a more sociable and interdependent species. It also offered new arenas for developing individual expertise and new tools for expressing personal and group identities.

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From Hand to Handle

The economic benefits of more efficient hunting and gathering tools based on hafting may have fed—literally—the growth of human population size over time. The knock-on effect is a potential increase in rates of innovation as populations grow and more minds interact to share and solve problems. All these social, biological, and demographic variables are considered in Chapters 3 and 6.

LONG LIVE THE REVOLUTIONS The interlinking of multiple technologies and expertise in the process of producing a composite tool is the basis of industry not just in the sense of the diligence needed to complete a complex task, but of a focus of manufacture on a product, such as the steel industry. Mass production of identical components and assembly lines are obviously recent developments, but they owe their ultimate origin to the innovation of composite technology. The first industrial revolution began, then, with the manufacture—literally the making by hand—of tools, and particularly hafted tools with their integrated components. Machine-based manufacturing is the more familiar product of the second industrial revolution, and it emerged only in the late eighteenth century. Five hundred thousand years separate the two, which is a relatively short interval compared to the chasm of more than two million years between the first appearance of tools in the archaeological record (c.2.6 million years ago) and the invention of hafting. All innovations (and inventions) arise from familiarity with existing materials and processes, and awareness of their limitations. A solution to a problem might come as a flash of insight, but that flash illuminates known territory, and that was the case with the first industrial revolution. It too had roots and these lay in the long human experience in the Old World (Africa, Europe, and Asia) of working stone, bone, and wood. These precursors (see Chapter 4) along with the control of fire (itself arguably a tool), are early integrative technologies whose making involved the bringing together of organic and inorganic materials and differing spheres of knowledge. These technologies provided the conceptual step towards combining separate parts into a functional whole. One stone-tool form in particular will be examined in more detail: the hand-axe. The making of this distinctive artefact, recognized by its three-dimensional

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symmetry, was a long-lived tradition that in its later phases (c.800,000–400,000 years ago) often incorporated the use of ‘soft’ hammers of bone, antler, and wood in the final shaping of the tool. The use of organic tools in the making of hand-axes not only brought different materials together in the sequence of manufacture, but made this association of materials a normal part of toolmaking. Such familiarity with the properties of each material and their respective roles in the manufacturing process was a precursor to an integrative technology. The common ancestor of Neanderthals in Eurasia and Homo sapiens in Africa made the various integrative technologies, and this species, Homo heidelbergensis, is also the likely innovator of the first industrial revolution.1 That H. heidelbergensis had the cognitive capacity to imagine, plan, and make complex tools should not come as a surprise given the large brain size of this ancestor. It had the capacity for language, as inferred from its fossil remains (see Chapter 2). The questions remain though: where and when did hafting originate, and of course, why?

NOW WE’VE GOT THEM, WHERE CAN I BUY ONE? The earliest archaeological evidence for hafting—indirect traces of the hafts themselves left on stone inserts, or the signs of preparation of inserts for hafting—is examined in detail in Chapter 5. There are few surviving examples of wooden hafts and plant-resin fillers, but they do provide material evidence that helps us understand the properties of the organic components involved in hafting and also helps narrow down the likely geographical origin of this innovation. The European record provides the earliest organic traces, but Africa and Southwest Asia have comparably aged stone-tool technologies that appear to be designed for hafting. A notable development in both regions is the systematic manufacture of long, thin, sharp blades. These make good cutting tools in their own right, but make even better ones when

1 The term ‘human’ is used throughout to refer to human ancestors attributed to the genus Homo.

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From Hand to Handle

hafted. Holding a blade without a handle risks cutting the hand, and there is a further drawback. The precision-grip used to hold a blade limits the amount of force that can be applied to the cutting motion when compared to a power-grip used to grasp a handle. These early blades (500,000 to 400,000 years ago) were relatively thick compared to their later counterparts; perhaps some were wrapped in skin or bark to provide protection, and in doing, offered a better grip. The act of applying a temporary protective cover may have been the precursor to the idea of a fixed handle. Blades were also being made 500,000 years ago in southern Africa, and here some blades and flakes were shaped into points and mounted as tips on spears. The invention of hafting was probably linked to hunting, but elsewhere it was applied early on to a variety of tasks and made daily chores just that bit easier than before. At this point, the ethnographic record of hafted tools can help us formulate some expectations for the early archaeological record. Collections of complete hafted tools were examined (in museums in Liverpool and Oxford) to reveal the basic range of haft types and arrangements for attaching working bits to their handles and shafts. The study looked at five common tool types (knives, axes, adzes, scrapers, and spears) to see whether there were underlying design principles for each type as well as any distinctive differences linked to task and environment. A relatively narrow range of hafting options was found for each, which reflects the physical constraints posed by the actions of each tool type: cutting, chopping, scraping, and piercing. The makers of the first hafted tools would have had to deal with these same considerations of force and motion. Returning to the archaeological record with our ethnographically enlightened perspective, we can see that blades and stone spearpoints are early African and Southwest Asian signatures of hafting. Across Europe and much of Asia, the signature takes the form of spearpoints, knives, and scrapers made using sharp flakes rather than blades. These three continents also share a technological innovation generally assumed to be linked to hafting through the production of sharp, thin flakes from preshaped blocks or cores of stone. The resulting flakes could be shaped and thinned further or used directly as cutting and piercing edges inserted into handles and shafts. These ready-made inserts and their distinctive cores offer another clue towards pinning down the likely regional origin of hafting. For the moment, southern Africa takes the prize in the origins sweepstakes, but the search for

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‘firsts’ distracts us from understanding the longer-term processes that characterize technological change. It also distracts us from grasping the reality that large gaps still remain in our basic knowledge of time and place when it comes to reconstructing the early history of hafting (Chapter 5). Three options lie before us: (1) there was no single centre of origin that can be detected with certainty; instead there appears to have been a vast network of information exchange operating across much of the Old World through which the invention spread too quickly to be visible by existing dating methods; (2) as sometimes happens, a good idea bubbles up independently from similar roots—think Charles Darwin and Alfred Russel Wallace on natural selection—and there was more than one independent centre of origin; and (3) there was a single centre or region of origin that existed from which the invention then spread with the movement of its makers and as an idea through social networks. For the moment, the second option best fits the existing data especially given its many limitations.

THE OTHER ‘REVOLUTION’—CLIMATE CHANGE Humans must live with their environment, adapt to changes, or, ultimately, face extinction. So how did global climate change affect human populations during the period in which hafting emerged? The ‘Middle Pleistocene Transition’ (or ‘Revolution’ to some climatechange scientists) marks a shift in the duration and intensity of global glacial cycles. That shift to longer cycles with greater extremes of cold and warm began about 900,000 years ago but became even more pronounced after 430,000 years ago. The impact on humans living through this Transition and particularly its more recent extreme phase would have been pronounced, with long-term shifts in the productivity of landscapes (availability of food and water) interrupted by periodic and abrupt changes in temperatures on a more human time scale—years rather than millennia. Annual seasonality also increased with greater fluctuations between summer and winter rainfall patterns. From the tropics to the high latitudes hunter-gatherer groups would have felt the effects of greater unpredictability in the availability of basic resources. The first industrial revolution may have been kick-started by climate change, but the limitations of the archaeological record make this a tough proposition to test.

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THE ARMS RACE AND OUR SECOND INDUSTRIAL REVOLUTION PREFIGURED Further innovations in hafting technology emerged in the Late Pleistocene (127,000–11,700 years ago) (see Chapter 6). The highlights include the first machines to propel spears and arrows and possibly the innovation of sprung traps. So far, the hafting revolution had been restricted to whole tools made of multiple components, but in the Late Pleistocene these innovations, or perhaps they should be called inventions, increased the effectiveness of hunting significantly. The spear-thrower added to the propulsive force of the spear and its effective killing range. The bow and arrow improved the accuracy, speed, and distance from which kills could be made. The lightness and portability of the bow and arrow as a unit made it an effective tool for hunting in all sorts of environments. Traps gave us the absentee hunter who could bring home the meat of large and small animals without the risks of a direct encounter. Together these innovations expanded our distinctive niche as communal super-predators. The new weaponry may also have given some human groups a competitive advantage over others as populations expanded and tussled for resources. (Plus ça change . . . ) These innovations marked a change in hafting technology, one that we are very familiar with today, in which two or more separate composite tools are really only effective when working together. What use is a windscreen wiper if not attached to a car, or a keyboard without its computer? An arrow and a bow separately are useless hunting tools, but together they are deadly. The relationship of dependency is not quite so equal for the spear and spear-thrower. The spear is still effective on its own, but the spear-thrower is only really designed to accompany the spear, though it can have secondary uses such as digging or carrying. The archaeological record reveals a trend towards greater specialization of components in the formation of these companion technologies, which in turn creates opportunities for craft (and later industrial) specialization. The invention of agriculture after 11,000 years ago established new technological needs, and the foundations for the current phenomenal world population growth and what appears to be runaway combinatorial evolution, at least from an archaeological perspective.

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This book attempts to weave together the sturdy warp threads of cognitive, social, and technological foundations with the finer weft of environmental change to form a new material with which to highlight what has been a largely overlooked period of our evolution. Our current utter dependency on technology for survival (and comfort) extends back to the first tools made; but only relatively recently, with the invention of hafting after 500,000 years ago, does it take its recognizable modern form. For those who fear that our technological dependency makes us supremely vulnerable, it is perhaps comforting to note that we have been innovating for a very, very long time, during periods of serious climate change, and we are still here to tell the story. Humans have the luxury of a history and a prehistory: it is up to us to learn what they can teach us.

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1 What Is Combinatorial Evolution? How do humans invent things? The underlying premise of this book is that inventions arise from intentional combinations of existing technologies, by a process that involves interplay between experience and knowledge, and with need—whether real or perceived—as the underlying stimulus (Arthur 2009). Archaeologists, anthropologists, sociologists, and historians have all considered the social processes by which technological change—and by implication, invention—takes place. Each discipline approaches the issue with different questions and with methods of analysis appropriate to its sources of data. In this study, the invention of hafting is argued to have taken place among one or more hunter-gatherer communities that lived c.500,000–300,000 years ago. Such long time spans blur human generations into inconsequential units, and in the absence of written records the individual plays no visible role in the process of innovation. We can see the handiwork of the individual in the artefact itself, but not the individual behind the invention. The search here is for the evidence of the foundational knowledge and experience on which the invention of hafting was based, and to consider possible stimuli to account for the timing and location of its emergence. Combinatorial evolution, as a concept, owes much to Darwin’s (1859) model of biological evolution in which small cumulative changes can, over time, lead to new and more complex forms. The driving force behind technological change, however, is human rather than natural selection. Before expanding on this formulation, some methodological background is needed to explain why the combinatorial concept is so apt for this study, and to place the contribution of the economist and complexity theorist W. Brian Arthur in its broader historical context.

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The material evidence is primarily archaeological, but behavioural models are needed to populate the past with cognizant and sentient social beings capable of making complex tools. The source material for such models is necessarily drawn from the social sciences, and especially those that focus on small-scale societies including huntergatherers and non-industrial farmers. The use of historic and contemporary societies as sources of comparative data involves a uniformitarian approach, one that assumes that behaviours seen today or in the recent past are similar to those exhibited by our distant ancestors. This assumption has obvious limitations, the first of which is the issue of species comparability. Five hundred thousand years ago the inventors of hafting were not Homo sapiens, and we cannot assume that they were behaviourally similar to us. That assumption has to be demonstrated, and if it cannot then some estimate of the degree of difference needs to be made. Secondly, modern and historic hunter-gatherer societies are not static; they have changed technologically and socially since the advent of hafting. The few that remain today have histories of contact with other societies that differed culturally, including technologically, such as farmers, pastoralists, and early states. Long-term contact typically leads to the exchange of ideas, goods, and marriage partners. Depending on the structure and intensity of interaction, the process can range from partial assimilation to complete acculturation or social extinction. Hunter-gatherer communities tend to be small in number and typically at a demographic disadvantage compared with their more numerous farmer neighbours. This demographic asymmetry is exacerbated by the differing economic strategies of the two types of communities: hunter-gatherers typically use mobility to meet their resource needs whereas farmers develop ties to particular areas of the landscape that support their crops and animals. Having a settled farming community in your midst as a hunter-gatherer community can be the social equivalent of the cuckoo in the nest, especially as the number of cuckoos grows. The physical extinction of hunter-gatherer societies also has occurred as a result of contact. The arrival of European whaling ships along the coast of Tierra del Fuego on the southern tip of South America in the early 1800s introduced a suite of diseases against which the indigenous population had no natural defences.

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A deliberate policy of extermination and acculturation by later colonial governments hastened the cultural and biological decimation of these hunter-gatherers. An unknown number of societies have been lost to our collective historical memory through long-term processes of cultural interaction. Our sample of contemporary and historic hunter-gatherers represents just a fraction of the cultural diversity that existed before the loss of land to the spread of farming societies. And the process of acculturation continues apace. In the Kalahari in southern Africa, hunting and gathering as a way of living has effectively ceased, and within just a generation, as communities opt for access to schools, clinics, and the convenience of shops over the rigours of mobility—a process hastened by government resettlement policies. A third limitation to the use of contemporary hunter-gatherers to model the social contexts of innovation and the origins of hafting arises from within the social sciences themselves. Anthropologists have, since the early twentieth century, paid intermittent attention to technology. Its study was considered an intellectually arid pursuit when contrasted to kinship structures, belief systems, and other complex behaviours (Pfaffenberger 1992: 491). Technology and its development became the preserve of historians, sociologists, and engineers rather than anthropologists. An interdisciplinary field emerged, known as ‘science and technology studies’, which filled the intellectual space vacated by social anthropologists. There were notable exceptions among more ecologically oriented anthropologists who recognized the central role that technology plays in a society’s adaptation to its physical environment (e.g. Forde 1934; Steward 1955; Oswalt 1976). Their work would have a lasting impact on the development of archaeological theory (e.g. Binford 1962, 2001; Torrence 1989), but sadly, as anthropological interest in technology reawakened in the late 1980s, the time for undertaking active fieldwork among hunter-gatherers had largely passed. We have at our disposal, then, a patchy ethnographic record of relevance for understanding not only the details of how tools are made but also the social contexts in which they are planned and used. From an evolutionary perspective we also lack comparative information on how small-scale societies—hunter-gatherers and subsistence farmers—transmit technological know-how from one generation to the next, how innovations arise, are perceived, then supported or rejected. There are the exceptions of course, such as Beatrice

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Blackwood’s study in 1936–7 of the technology of horticultural communities in highland New Guinea who cultivated sweet potatoes, gathered wild plants, hunted small game, and fished. She recorded in detail the materials used and the sequence of manufacture of the most versatile tool in their repertoire, the hafted stone-bladed adze. The sequence starts with the selection of the appropriate stone for the blade, the grinding of the preferred edge angle, the choice of wood for the haft, its shaping to hold the blade, the choice and application of binding material (cane in this case), and the uses to which the finished product are put. In the lexicon of contemporary stone-tool analysis, this is an early form of chaîne opératoire study in which each step of the decision-making process from start to finish is recorded, including the decision to repair or discard the tool. There’s certainly much more the modern archaeologist would want to know about the decision-making processes involved in adze-making and use. Who in the social group makes these tools, how is the knowledge learned, and just when do you decide an adze blade is no longer worth resharpening? Given that very few societies today still make hafted stone tools, we are left with limited opportunities to study the social contexts of toolmaking and use. One rare contemporary example from the highlands of Indonesia reveals how a system of apprenticeships lasting up to ten years introduces boys to the craft of making hafted stone adzes (Stout 2002). Tool-making in this community is not just about producing a functional adze, it is an integral part of the social process of inculcating values in the young and ensuring continuity of the group’s culture. Historians and sociologists have for good reasons not considered the potential of the early archaeological record as a source of information about the process of innovation. The arcane subtleties of stone-tool technologies elude the uninitiated, and the coarse timeresolution on offer—typically in the order of tens of thousands of years—makes this an unpromising field for investigating not just the role of the individual, but even wider social forces in the process of innovation. As one respected historian of technology states: ‘In the study of stone tools we search in vain for discontinuous jumps to wholly new forms’ (Basalla 1988: 31). Such a view not only reveals a limited understanding of the archaeological record, it reflects a perception that the crafts (a dismissive term in some circles) of hunter-gatherer societies were sparse and technologically simple,

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of little relevance to understanding the development of our own technology-dependent world. Redressing that misperception motivates this study—the principles of combinatorial technology that underpin so much of the technology we take for granted today originated not in the Industrial Revolution but during the Middle Pleistocene Transition. Given the limited ethnographic and historical database of relevance to archaeologists, we have increasingly come to rely on generating our own understanding of the process of technological innovation through experimentation. Experimental archaeology involves more than just knapping a flint knife and using it to butcher a sheep carcass. As informative as that kind of hands-on activity might be, a rigorous experimental approach requires the careful recording of tool use under controlled conditions in which actions are restricted to one kind of movement at a time, such as cutting with the knife blade moving away from the body, applied to one contact material and for a limited period of time. The experiment needs to be repeated to generate a statistically valid sample, and then a new variable introduced, such as a different contact material of similar hardness, to assess similarities and differences in edge damage from use. The analyst also needs to be blind-tested to assess his or her accuracy in identifying microscopic traces of use, hafting, direction of use, and likely contact material. Only with a well-developed understanding of the physical effects of different kinds of use on a particular type of stone can the analyst then move with some confidence to examining genuine artefacts themselves. Such painstaking analyses do generate valuable insights about decision-making steps in the making and use of tools. However, such studies are not only time-consuming and limited in the numbers of artefacts that can be examined, they are also necessarily artificial constructs divorced from the messy reality of tool-use in a huntergatherer’s camp. A knife might be used to dismember a carcass one minute, then used casually to scrape sticky meat scraps off the butcher’s hand, who while doing so saw a scorpion approach and used the knife tip to skewer the poisonous insect into the sand. Each action might leave a trace, one over the other in a potentially confusing sequence that stretches our use-wear analyst’s experience and powers of deduction. There are other problems with the experimental approach, such as the uncertain preservation of traces of use depending on the type of stone and the sediments in which an artefact

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was buried. This sub-field of archaeology remains a specialist’s preserve with as yet limited application to the periods and places relevant to the origin of hafting (see Chapter 5).

THE SOCIOLOGY OF INVENTION Against this background of far from ideal anthropological and archaeological sources, why should the work of an economist and complexity theorist such as Arthur be of relevance? Surely his insights are far removed from the low-tech world of hunter-gatherers and of little value to us. A superficial reading of Arthur’s The Nature of Technology (2009) would confirm this impression, for it uses the development of aircraft in the twentieth century, and in particular the jet engine, as supporting case studies to illustrate the cumulative foundations of complex technologies. Beneath the high-tech examples, however, lie principles that apply equally well to the early development of technology. Arthur’s idea of change through the slow accretion of cumulative innovations based on existing technologies is not new. He draws insight from an influential American school of thought that emerged in the 1920s and coalesced in the 1930s under the label ‘sociology of invention’ (Gilfillan 1935). Its proponents argued against the Victorian belief in progress as a series of stages that led ultimately to civilization, and in particular European civilization, as the inevitable pinnacle of achievement (Bowler 1989: 19). Rather than assume inevitability to history, this group of sociologists sought to understand how differences arose between peoples based on geographical constraints, the influence of learned cultural traditions, and how these affected a group or people’s responses to immediate social conditions. Inherited biological differences—racial differences—were downplayed in recognition of the inherent unity of our species. The facility by which ideas moved between cultures demonstrated the innate equality in the cognitive capacities of all peoples. William Fielding Ogburn outlined these principles in his influential volume Social Change (1922), which catalyzed the formation of this distinctive school of thought.

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Of particular relevance to this study is Ogburn’s insistence that social heritage conditioned the process of invention, noting that ‘The cave man, had he the ability of a modern genius, could not have invented the steam engine’ (Ogburn 1922: 34), given his lack of knowledge of all the prerequisite technologies needed to construct such a device. Inventions were not the product of any one individual but of the collective whole. Given the archaeologist’s lack of access to the individual, this is an attractive proposition, but the real value of Ogburn’s observation (1922: 73) is that innovation is a cumulative process: ‘The use of bone is added to the use of stone. The use of bronze is added to the use of copper and the use of iron is added to the use of bronze. So that the stream of material culture grows bigger.’ The additive quality of technological change set Ogburn apart from the Victorian model of stages of progress. Otis T. Mason, curator of ethnology at the Smithsonian Institution in Washington, DC, had made much the same observation a generation earlier in his study on The Origin of Invention (1895). Mason used his extensive knowledge of the technologies of ‘primitive peoples’, by which he meant hunter-gatherers and farmers, to outline a model of increasing technological complexity over time. Whereas Mason (1895: 27) felt that the ‘communistic’ organization of these societies stifled individual initiative and so technological progress, Ogburn took a more nuanced anthropological view that argued for the understanding of the sources of variability within individual cultures rather than lumping them into some generic stages of human progress. He made the still very relevant observation that we live in an age in which rapid technological change is the norm and we have grown accustomed to expecting a succession of inventions. That expectation colours our perception of other societies, leading us to pass judgement on progress in prehistoric and contemporary societies by our culturally conditioned standards. Before the development of science-based engineering, technological change was slow everywhere and what is exceptional ‘is the rapidity of change as found in modern western cultures’ (Ogburn 1922: 171). Rapidity of change is now the global expectation. (We will return to Ogburn’s relativism in Chapter 6 when considering the apparently slow adoption and elaboration of hafting technology once the first industrial revolution was underway.) By the mid-1930s, this school of thought had become mired in an intellectual trap of its own making (see McGee 1995). On the one

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hand, inventions were determined by culture and small-scale societies were inherently conservative when it came to innovation. Innovation was a slow cumulative process and did not require exceptional individual intelligence to meet basic needs. On the other hand, despite the unity of humankind, there were individuals in any social group with above-average intelligence, and Ogburn and others of this school assumed they would be the natural inventors. Habit derived from social heritage, however, dampened the impact of inventive genius and initiative. How then could truly significant inventions arise? The emergence of Western science in the mid-seventeenth century was an historical process that tested the assumptions of this school of thought. The way through this dilemma was to make recourse to a shift in the mindset of Western society that enabled exceptional individuals to challenge tradition and bring forth science with its rational, systematic approach to problem solving. These ‘great men’ (such as Isaac Newton and Erasmus Darwin) possessed a combination of superior ‘intelligence, moral traits, strengths of motives for inventing . . .’ plus the ‘. . . time available and mental and mechanical equipment for it’ (Gilfillan 1935: 10). There had to be a social context that enabled and then supported innovation, but ultimately the making of an exceptional discovery was attributed to the creative genius of the individual inventor. The critical element underpinning the process of invention had shifted from the collective power of social inheritance to the heroic achievements of the individual. The burden of explanation was placed on the still young discipline of psychology rather than the more established field of historical analysis.

The Social Constructionist’s Challenge The internal contradictions within the school’s model of invention contributed to its eventual dissipation as an intellectual force, though it had a brief revival in the 1950s and 1960s with the reissue of seminal works such as Ogburn’s treatise on social change. The rise of the post-modernist critique of science from the 1970s onwards (Heidegger 1977; Foucault 1998) hastened its demise. A new generation of scholars argued for the primacy of the individual as an active agent in constructing social worlds, not the passive prisoner of social heritage. Artefacts as well as institutions were fluid, changing

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constructs created by individuals and groups in a constant interplay between perceptions of reality and experience. Social constructionists, as members of this loosely defined group are called, do not adhere to a single core theory of human behaviour (Killick 2004: 571), and they eschew grand narratives of technological change driven by impersonal forces, such as natural selection and optimal efficiency (Pfaffenberger 1992). Social constructionists hold no truck with Victorian views of the inevitability of progress, and reject necessity as the driving force of innovation—‘culture, not nature, defines necessity’ (Pfaffenberger 1992: 496). There is also a clear rejection of the racist undertones of past attempts to equate technological complexity with intellectual ability (McGee 1995), as advocated by some of the earlier generation of sociologists of invention. The constructionists’ methods of studying technological change are varied, but they share an approach that aims to reveal the many social influences that consciously and unconsciously guide our decision-making as individuals and members of groups. The choices we make when presented with a range of tools that can satisfy a task reveal much about our perceptions of reality, such as the importance of social status or certain religious beliefs. Buying a washing machine, for example, is not always simply about selecting the best product for the price, it can be a social and perhaps a political act. Colour, design, brand, size, efficiency, price—each decision makes a statement about us, our aspirations, and perceived place in society. For archaeologists, social constructionists offer valuable insights into the process of learning about technology in pre-industrial societies, and in particular the importance of observation and imitation. They also remind us that so-called ‘primitive’ technologies are anything but; they integrate knowledge about materials and techniques, but also the social contexts of their making and use, including ritual (Pfaffenberger 1992: 509). Judging the social complexity of a past society by its tools alone smacks of intellectual laziness. Chastening thoughts, but for this study which looks at the early archaeological record there is a fundamental problem with their methodology. A constructionist interpretation requires that the group under study had a materially rich repertoire of tools from which choices were made, but that is rarely the case in the early record. Secondly, to reconstruct social organization and belief systems as well as other influences on individual and group decision-making demands a high-quality database. A fine-grained record is needed, one with well-constrained

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spatial information about the range of activities undertaken at the individual and group level. The sites also need to be contemporary in time. The vagaries of preservation make this a tall order, compounded by the mobility that characterized Middle Pleistocene hunter-gatherers. As a generalization, they made relatively few tools and left only sporadic traces of their activities spread across landscapes. We also cannot easily date sites accurately enough to capture a shared interval in the lives of a community. The Middle Pleistocene spans an interval of c.770,000 years (900,000–130,000 before present [bp]), and lies well beyond the effective reach of radiocarbon dating (40,000 bp). Current dating techniques at their very best can give us a resolution measured in thousands of years, and with wide error margins: certainly not on a scale able to pinpoint the life of an individual or a community. There are exceptions of course to the limitations of the archaeological record. Caves sometimes offer well-preserved glimpses of social behaviours such as burials, hearths, and living areas, and there is the rare glimpse of activities in the open. Four hundred thousand years ago beside a river in what is now eastern England, a knapper sat near a hearth crafting a hand-axe. A couple of flakes fell into the fire, but then the knapper struck a flaw in the stone and abandoned the unfinished tool (Gowlett 2006). Such moments in the life of an individual are essentially invisible to us except through individual artefacts preserved in exceptional circumstances. Dispiriting though these realities are, all is not lost in the study of decision-making at the individual and group level. The concept of the chaîne opératoire offers a practical approach to the study of choices made in the conception, manufacture, use, and discard of a tool. When this is combined with first-hand knowledge gained from experimental archaeology, the archaeologist can then begin to unravel some of the cognitive complexity embedded in a past technology. Experimental psychology has a role to play in this endeavour, especially given the advent of methods of observing brain activity linked to the planning and making of tools (see Chapter 2). There is also still value in the study of the sociology of technology among contemporary small-scale societies, limitations aside, and from extending that approach to include other tool-making species, especially primates.

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COMBINATORIAL EVOLUTION AND TECHNOLOGICAL CHANGE To examine long-term processes of technological change, however, we still need an evolutionary perspective; one that seeks to explain patterns of change on broad temporal and geographical scales, but one that also allows us to focus more narrowly on historical developments at a particular time and place. Such flexibility might seem contradictory, but its biological counterpart is Darwin’s general theory of evolution based on natural selection and its application to understanding the origin of individual species. In this analogy, combinatorial evolution provides the overarching theory of technological change and the origin of hafting is the particular ‘species’ of change to be understood. But the Darwinian analogy has its limitations. Combinatorial evolution is driven by human beings, not natural selection, and variability arises from cultural rather than genetic change. Arthur draws from Ogburn and the early sociologists of invention a model of innovation emerging from existing technologies through a process of incremental and cumulative change over time. It is the accumulation of many small changes that can lead to occasional spurts of rapid and radical change or invention. Where the sociologists resorted to individual genius and force of character to explain significant moments of technological progress in the face of the inertia of tradition, Arthur outlines a less heroic and more anonymous if not mechanistic process of the evolution of invention. It begins with simple technologies being combined into components, which in turn become the building blocks for new technologies that in time may be the components for other technologies (Arthur 2009: 21–2). The nested or recursive structure of combinatorial technology gives it the character of a self-reproducing organism in which tools create other technologies. Recursiveness is a principle familiar to mathematicians, computer programmers, and linguists. From basic building blocks and a set of rules for their combination, complex structures can emerge repeatedly and rapidly as in the case of language (Gibson 2007). Sounds make words, words make sentences, and sentences convey meaning, and from these basic components, plus rules of grammar, we can express an infinite number of thoughts (Pinker 1997: 88). In the realm of combinatorial technology,

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an increase in complexity depends on the harnessing of natural phenomena and applying them to particular purposes, such as heat from fire to cook meat or the force of motion when striking two stones together to make a sharp flake. The capture and application of phenomena does not happen automatically, but is the work of individuals who are also social beings. An invention is first a product of the human mind and then of the hands, but it is the social world that provides the stimuli for change in the form of perceived needs.1 A technology as a thing that can be changed through innovation or invention is more than just an object that provides a means to an end. Arthur (2009: 28) defines technology in three overlapping levels of increasing abstraction: first, as a method, process, or device that fulfils a human purpose, for example the knife that cuts. Second, by reference to what could be called a body of technology with integrated practices and components that develop around a particular natural phenomenon, for example flint-knapping using the properties of breakage patterns in glass-like stone or the heat generated by fire. And third, a technology is the collective body of knowledge of devices and practices that a particular culture or society has at its disposal, in essence, its material culture. Together these shades of meaning provide a more inclusive definition than that used by the early sociologists of invention, and to it we can add the constructionists’ emphasis that technology is also deeply embedded in social practices that give individuals a sense of belonging and meaning (Pfaffenberger 1992: 497). Our example of the hafted knife illustrates these multiple and coexisting meanings of technology. It is a device for cutting and so fulfils a humanly defined purpose. Its individual components are technologies in that they are based on separate bodies of knowledge 1 Is there such a thing as a real, biologically determined need? Social constructionists would say no, our needs are of our own making, that tools are not needed even to fulfil that seemingly most basic of needs, extracting energy and nutrients from the environment, and that we, like other animals, could live without even the simplest tools (Basalla 1988: 13). Perhaps this was so for our early hominid ancestors in the tropical forests of Central Africa, as is the case for gorillas today (with their specialized digestive system that allows them to live on a diet of leaves and fruit). But that toolfree option does not exist for humans now and probably hasn’t been a viable option since the onset of global glacial cycles 2.6 million years ago. Even though most chimp communities today rely on tool-use to enhance their food security, they are not absolutely dependent on tools for their survival (McGrew et al. 1999). What made us so?

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about stone-working, wood-working, and animal tissue as binding. Similarly, the resin filler and its preparation represents a body of knowledge and so a technology. Hafting technology, of which the knife represents one category of device, forms a part of the collective technical and social knowledge available to its makers for meeting perceived needs (see Fig. 1). Perhaps that hafted knife also served as an emblem of the social position of its owner, a status that continued into the afterlife, marked by a communal burial ritual in which the knife was deposited as a grave good. Reconstructing the social meaning of objects remains a methodological challenge for archaeologists, but with the principle of combinatorial evolution we have a sense of the structured integration of technological with social knowledge. From the deceptively simple act of making a tool by combining components into a whole, an extensive network of supporting technologies develops, one that, more likely than not, involves groups of individuals who share a learned tradition of ways of making and doing things.

OPPORTUNITY NICHES, INNOVATION, AND INVENTION Compared with the ease with which thoughts are expressed through language, the combinatorial principle of tool-making offers a far more limited capacity for innovation. That capacity is restricted by our existing knowledge, experience, and to some extent by our perceived needs or demands. If we feel these demands are currently being met, then why innovate? But our wants are not static; they change hand in hand with our increasing dependency on technology. Technology generates ‘opportunity niches’ (Arthur 2009: 174), in much the same way that environmental change can reconfigure habitats in favour of some species over others. Our current reliance on fossil fuels for energy may be driving global warming, but it has also generated an opportunity niche for the development of technologies which capture and store greenhouse gases, or which produce little or no carbon dioxide. At the more personal level, we could all live without a mobile phone, but this technology has become so integral to social and working lives that it has become a perceived necessity rather than

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a luxury. In contemporary industrial societies, social aspirations are a driving force of innovation, as is the profit motive, and the two are intertwined in the corporate world (Johnson 2010). For Middle Pleistocene hunter-gatherers the invention of hafting would have certainly expanded the range of material options for meeting existing demands. It may also have generated new perceived needs based on the effectiveness of inventions such as the bow and arrow. A good bow hunter might gain in social status as a reliable provider for the family and community. With each innovation in tool design there is an inbuilt opportunity niche for improving its efficiency. Optimizing efficiency may be a modern preoccupation in a global economy, but we shouldn’t assume that hunter-gatherers, past and present, wouldn’t also welcome labour-saving innovations. Lewis and Clark (1842) in their epic journey of exploration west of the Mississippi (1803–6) noted that those native communities in contact with European traders were quick to adopt iron over stone as their preferred material for making arrowheads. It was sharp, strong, light, and it did not break as easily as stone. The advantages of iron and especially steel over stone have been demonstrated experimentally (e.g. Saraydar and Shimada 1971), but there can be unintended consequences of adopting new more efficient materials. In a classic study, the American anthropologist Lauriston Sharp (1952) recorded the social impact that the shift from ground-stone to steel axeheads had on Australian aboriginal communities. The making of a stone axehead took considerable effort, and its production was the preserve of older men who gained in social standing from their control of this technology. The advent of cheap, ready-made steel axe blades not only made this a tool accessible to younger men and women, but it also altered the social order; the elder males lost their privileged status to this new opportunity niche. Modern parallels are easy to find, such as the rise of blogging and tweeting as challenges to the corporate and political control of news and commentary. As social constructionists would remind us, technology is intimately integrated into our social lives and they change as one. Sharp’s study also draws attention to a distinctive design feature of combinatorial technology. With its physical and conceptual separation of components, tool design can be altered and improved relatively easily. The iron axehead, if made to the same size as its stone counterpart, can be inserted into the shaft without requiring major

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design changes to the other components. But a more substantial modification of individual components will, more likely than not, result in a cascade of changes. A longer knife blade might need added support in the haft, so a slightly deeper notch is cut and the hafted end of the stone blade then tapered to fit the notch. The amount and extent of the binding might need adjusting as well, along with an increase in the thickness of the handle to minimize splitting with use. Improvements can also be made by refining components through specialist production, something common in automated manufacturing but rarely seen in small-scale egalitarian societies. This option is only viable if there is sufficient demand to justify the separation of tasks and expertise. Task separation among hunter-gatherers is typically organized by sex and to a lesser extent age. This basic division does allow for different pools of expertise or craft knowledge to be developed through trial and error, observation and discussion among sex peers (explored in more depth in Chapter 3). Ideas for improvements might come from familiarity with other technologies and then be transferred (Arthur 2009: 135), or they might arise from sheer frustration. In a process of ‘structural deepening’ an existing limitation to a technology can be addressed by adding more components. Eventually though, a point is reached when a problem cannot be solved by refining or simply adding more of the same. A new solution is needed, but in its absence you use what you know. If we accept that innovation takes place by a slow process of cumulative minor innovations, then how do novel, radical, and rapid inventions take place? Arthur (2009: 108–10) outlines the sociological contexts of invention as they apply in a world of market forces, but there are observations here of value to modelling the evolution of hafting. An invention is both an intellectual and practical act; it involves envisaging a fundamental change in the operation of a device and then putting that conception into action (Jewkes et al. 1969). Insight emerges from accumulated experience of materials, processes, and applications. That ‘deep craft’ knowledge (Arthur 2009: 160) is the foundation for drawing associations between a recognized need, known properties of a technology, its effects in one sphere of application and an imagined outcome if applied to another. That’s lateral thinking (‘thinking outside the box’, ‘pushing the envelope’), but this shorthand for intelligence doesn’t do justice to its foundation based on experience.

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The second part of the inventive equation requires putting it into practice—it needs to work physically as well as conceptually. The development of the microwave oven is a case in point. The need behind the invention wasn’t to cook food more quickly, but to develop a successful consumer product for a company struggling to survive after the end of World War II. Raytheon made radar equipment for the American military, but faced financial ruin with the end of the war. Its engineers were given the task of developing a commercial product, and one particular engineer, who had a deep working knowledge of the radar (microwave) tubes, made the conceptual link between the heat generated by the tubes and their potential for cooking food—a melted chocolate bar providing the spark of insight (Hammack 2005). The development of an affordable and practical oven for household use, however, took another twenty-five years of mechanical refinement combined with a sustained marketing campaign to create the demand. Today, the ability to cook a meal in a few seconds instead of hours is a well-entrenched domestic ‘necessity’ for some. As might be expected with such a lucrative invention, it has spawned a range of subsidiary technologies including new forms of packaging. If the process of invention involves the transfer of ideas across domains of knowledge to create a novel solution to a perceived demand, then can we say that hafting really was an invention? In a word—yes. A hand-held knife blade worked as a cutting tool, but the addition of a wooden handle created not just a more effective and safer device, but one based on a new principle of tool-making that could be applied across a range of activities. Hafting as a form of combinatorial technology changed the way humans thought about technology in all three senses of the word: as a specific device, a body of practice, and as a collective of knowledge and devices. The early sociologists of invention struggled with the disjuncture they created by insisting on a generic model of gradual change in preindustrial societies and its failure to accommodate rapid change in the form of the Industrial Revolution. Combinatorial evolution sidesteps the need for the creative genius driven by a mission to change the world. With the aid of a simple computer model based on logic circuits working to a limited set of rules, Arthur and Polak (2006) replicated the process of combinatorial evolution, including critical moments of change. From simple combinations of effective circuits in fulfilling specified tasks—the equivalent of tools—more complex

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circuits emerged. But the evolution wasn’t a smooth linear progression; it was punctuated by key building-block technologies that quickly enabled other technologies to emerge. What was important in the process was the order in which combinations were built, and the fact that certain effective simpler technologies were retained, serving as stepping stones to later ‘enabling technologies’. This modelling might make technological change appear to be a natural phenomenon freed of human input, but the modellers designed the rules by which certain innovations were retained. In the real social world, the individual is indeed an agent of technological change, but one working within existing socially generated understandings of perceived demands and available solutions. An individual invented hafting. Just where and when that person lived is unknowable, but we can say what was involved in the process. He or she had the insight (and cognitive capacity) to bring together socially learned deep craft knowledge of various materials, and apply it in a new way to solve a perceived need. This creative process probably happened more than once, in more than one place, in response to similar problems, but failed to take hold. Perhaps the invention was not socially acceptable—we know that some social contexts are more supportive of innovation than others. Or perhaps the available materials simply did not work well enough together to justify repeating the effort or to dislodge a tried and tested way of doing things. The challenge ahead is to try and extract from the scattered archaeological, fossil, and environmental evidence just where, when, and why the conditions were ripe for the invention of hafting. As Arthur (2009: 125) concludes, ‘the fact that all inventions are supported by a pyramid of causality means that an invention tends to show up when the pieces necessary for it, and the need for it, fall into place’. Five hundred thousand years ago the necessary cognitive, social, and technological pieces were in place for the invention of combinatorial technology. As for the need, its identification lies partly in the direct dependency of hunter-gatherers on the environment for survival, and partly in the integrative technologies that long preceded hafting. The latter provide the surviving record of the deep craft knowledge that existed across the Old World. They also reflect some of the real and perceived needs of communities of the time. From this starting point we can begin to consider technological and social responses to the great impersonal force that is climate change.

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Palaeolithic communities faced increasing extremes of temperature and seasonal variation, especially after 430,000 years ago. We can expect to see signs of structural deepening with the stretching of existing technologies in the face of changing ecological conditions, and perhaps too with shifting population pressures as habitats changed. The old ways of satisfying demands became more difficult to sustain, and probably in more than one place and at different times an individual combined insight with craft experience to create a new form of tool made of multiple parts. That invention probably made the daily tasks of making a living just a bit easier, less risky, and more productive. The new idea and the experience of using the tool were then shared in the intimate setting of a small hunter-gatherer community. From humble beginnings came a revolutionary idea that would gradually transform our world.

2 Neural, Cognitive, and Anatomical Foundations The invention of hafting took place in a technological world in which the hand holding a tool was the primary interface between the individual and the environment. Hand-held tools were used to cut, scrape, chop, and pierce. They compensated for our lack of claws and powerful jaws. Hafting enhanced the effectiveness of these basic actions and gave us a new way of thinking about how tools could be made and used. The impact was to extend our reach into the world both physically and conceptually. We have evolved into the most adaptable primate with an unrivalled intellectual capacity to innovate and invent. That capacity has a biological foundation, and to understand how and when hafting was invented we need to understand how the brain works. We then need to try and discover when the ability evolved to imagine a hafted tool and plan its making. Brain tissues and minds do not fossilize, but by working backwards from the known to the unknown we can estimate roughly when the invention of hafting might have been possible.1 We can do this with the help of recent innovations in neuroscience that allow us to see the brain at work when we are thinking about tools and making tools. The results lend support to the long-held theory that the making of tools co-evolved with language. This chapter reviews the techniques of brain research, provides a basic introduction to neural anatomy (Appendix 1 is there for supporting detail), 1 Brain tissues do survive in unusual anaerobic conditions that slow the process of decay, such as waterlogged peat. The largest number from a prehistoric context comes from the 7,000-year-old site of Windover Pond, Florida, where more than ninety individuals have been recovered with intact brain tissues (Milanich 1994). There are no surviving brain tissues relevant to the study of earlier humans.

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and then outlines those areas of the brain that are likely to have been engaged in the invention of hafting. The networks of the brain are the biological foundations of the mind, and we will consider which cognitive processes are needed to imagine and craft a hafted tool. The neural links between language and technology give us another potential route to identifying when the capacity for hafting evolved. We will also review the evidence for handedness in the archaeological record, as this provides a valuable historical insight into the evolution of language—and by inference the ability to make complex tools. There is also, of course, a blood-and-bone extension of the mind that is a necessary part of our search for when hafting evolved—the hand and the grip it forms. Certain grips are needed to hold a handle as well as make the tool, and, as we will see, there is enough fossil evidence to say approximately when this capacity existed.

WHAT IS A COGNITIVELY COMPLEX TOOL? We start with a simple definition of complex tools provided by cognitive neuroscientist Scott Frey (2007: 368). Complex tools do more than just extend our limbs, they transform their actions into something qualitatively different. A stick gives us greater reach but a knife enables us to cut and pierce, which are difficult to do with the hands (and fingernails) alone. From this perspective, hafting easily qualifies as a complex technology. It also combines practical skills with the reasoning needed to solve a particular problem or satisfy a perceived need. Simple tools do the same, but adding a handle changes not just what the tool can do, it also affects the coordination of hand and body movements and the mind’s perception of the tool as an extension of the arm. The term ‘body schema’ refers to this mental map of body shape and posture that is constantly updated as we use a tool (Maravita and Iriki 2004). The typical hafted tool has three basic components (handle, joint or haft, and insert) and when they are combined the binding of the haft obscures the shape and structure of the joint (see Chapter 5 for more detail). It might also obscure the adhesive inside the joint. The component parts also have separate histories of making and bodies of knowledge of the materials used. This is a complex set of embedded thoughts and actions, and as far as we know no other tool-using

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animal has the ability to imagine such an extended chain of reasoning. That chain includes materials with unobservable properties, and for most animals out of sight means out of mind. Visual clues are needed to trigger responses and trial and error is often the primary way to solve problems (Povinelli 2000; Wolpert 2003; Penn et al. 2008). Even chimpanzees, the most sophisticated of primate tool users, make conceptually simple tools that are task specific, though with some capacity to generate their own shared norms of how to make a tool (Whiten et al. 1999; Preutz and Bertolani 2007). Human technical reasoning involves the application of models of cause and effect across contexts, enabling us to imagine alternative solutions to a particular problem (Osiurak et al. 2010). We can imagine making or using more than one tool for the job, and as social constructionists remind us, the choice of tool is as much a cultural decision as a functional one. Hafting gives its users a template of cause and effect for constructing tools that can be adapted to suit a particular situation or a changing need. Most of our daily routines are just that—predictable responses to predictable activities. From such repetitious experience we form mental models about which tools, techniques, and actions to use for a particular task (Buxbaum et al. 2006). These models enable us to perform everyday tasks smoothly, such as driving a car, without having to think through each step of the process. Novel situations challenge these habitual responses to the familiar and test our creative problem-solving abilities. The invention of hafting may have been a particularly creative response to some persistent problem. We will never know just what the stimulus was, but we know that inventions are drawn from a well of practical experience combined with the awareness of the properties of other tools and materials. The creativity lies in making new connections between existing information, a kind of abstract reasoning which has its root in the workings of the brain (Wynn 2009). The location, functions, and interactions between particular neural structures are becoming increasingly well understood as a result of innovations in the technology for studying the living brain. These data, combined with research on brain injuries that affect mechanical reasoning, provide the insights needed to reconstruct the cognitive foundations that underpinned the invention of hafting.

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Before the 1970s, most of our knowledge of the structure and function of the brain came from dissections, clinical observations of braindamaged individuals, and from measuring the electrical activity of neurons (electroencephalography, or EEG). All three remain important sources of information, but they have been supplanted in more recent years by a suite of techniques that provide exquisite detail about neural anatomy and the function of the living brain (in vivo). While EEG does record levels of activity in the active brain, it lacks the fine spatial resolution offered by the newer generation of imaging techniques.2 By the late 1970s, that resolution became available in the field of medical imaging, where it was used as a diagnostic tool to detect a variety of diseases and abnormalities. The application to cognitive neuroscience soon followed and has since been applied to understanding the evolution of technology, as we will see shortly.3 But first, a little background information is needed on current imaging techniques so that their potential and limitations for archaeological research can be appreciated.

Innovations and Limitations Computerized axial tomography (CAT or CT) creates three-dimensional models of neural structures by combining multiple X-ray images of 2 EEG does have the advantage of almost instant recording of neuron activity compared to the delayed PET and fMRI signals that emerge from the study of blood flow and chemistry. The limited spatial resolution offered by EEG has been improved when combined with another electromagnetic recording technique, transcranial magnetic stimulation (TMS). The TMS device is placed on the scalp and an electric current is passed briefly through a coil. This causes disruption in the brain areas covered by the TMS, allowing the tester to see whether the functions being tested at the time are disrupted, thus showing they guessed at the right location. TMS enables researchers to manipulate directly activity in the cerebral cortex to locate the connections with sensory and motor areas (Taylor et al. 2008). Deep sub-cortical activity, however, cannot be detected. 3 These innovations in imaging techniques make a good case study of the cumulative development of combinatorial technologies. They were built with existing technologies, such as X-ray screening (CT), radioactivity counters (PET, SPECT), and spectrometers from particle physics (fMRI) that were then integrated with computer visualization programmes and equipment. The now widespread use of these imaging tools beyond the fields for which they were developed makes them examples of what Arthur calls ‘enabling technologies’.

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blood flow containing a radioactive tracer. The tracer is injected into the volunteer who lies still in the scanning chamber, and depending on how quickly the tracer decays a sequence of scans can be made at regular intervals to record increases in blood flow over a period of time (Shallice and Cooper 2011). The resulting images are summaries of patterns of activity. The volunteer is given a task to do, which then triggers a change in the activity of neurons which in turn leads to change in blood flow. Positron emission tomography (PET) and single photo-emission computerized tomography (SPECT) also use a tracer to monitor metabolic changes in neural activity, such as oxygen use and sugar (glucose) metabolism. Functional magnetic resonance imaging (fMRI) offers another approach to the detailed mapping of specialized neural areas. No radioactive tracer is needed as this technique measures differences in blood oxygen levels that reflect levels of activity among neurons. These imaging techniques offer full brain images that can reveal areas with specialized functions and the networks of areas involved in particular sensory, motor, or cognitive tasks (Price 2000). Previous studies of a brain-damaged site often assumed a direct correspondence between the location of the lesion and the lost function. Functional imaging techniques make no such assumptions and allow the researcher to identify multiple areas that might be involved in a particular task. They can also reveal the active interconnections between deep brain structures (i.e. diffusion tensor imaging, DTI) and surface regions, without the obvious limitations of dissection. Since the 1990s, fMRI has become the most widely used method for mapping brain activity given its comparative ease of use, good spatial resolution, and non-invasive procedures. (Before moving on, the reader needs to be aware that there is a vigorous debate underway about the interpretation of functional imaging results in terms of specific behaviours and their evolution. This reductive ‘neuromania’ is said to degrade our humanity by reducing consciousness and thinking to patterns of brain activity [Tallis 2011]. For those with patience and a science background I recommend Shallice and Cooper [2011] as a reasoned effort to bridge the philosophical and methodological divide.)

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Sample Size and Gender Bias Despite the impressive advances made in the understanding of brain structure and function, there remain significant methodological and practical limitations to these techniques for the study of the evolution of technology. Four are discussed here: sample size, gender and cultural bias, cross-species analyses, and the practical physical constraints on experimental design posed by the imaging techniques themselves. The number of individuals involved in any one imaging study tends to be small, typically fewer than thirty, which means that the results cannot be treated as representative of any population of modern humans, let alone past humans. Small sample sizes are a reality of experimental design given the need for repeated trials of each brain activity to establish the reliability of results. Experiments cannot be too long or too complex as a result (Lewis 2006: 213). There is also the issue of the cost of scanner time and expertise to process images. The problem of sample size is exacerbated by the common practice of using university student volunteers, which limits the age range sampled and raises a related issue of cultural bias, discussed below. Few studies have involved left-handed subjects, so most of what we know about the location of brain activity related to tool use comes from the right-handed majority, though that bias is well recognized. Genderbased differences in brain activity are another under-represented area of study. In time, these limitations of sample size will be overcome, especially as more and more studies begin to reveal consistent patterns. Neuroscientist James Lewis (2006) has shown one way forward in terms of revealing and understanding the neural networks involved in hafting. Lewis combined the results of sixty-four imaging experiments undertaken over a ten-year period involving a total of 461 participants. He used this expanded database to identify patterns in neural activity linked to practical tool-use skills and to the conceptual knowledge of how and when to use tools. The sample is still small in relation to the 7 billion human inhabitants of the planet, but it provides the most robust data set currently available and highlights areas for future research.

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Cultural Bias In addition to age, handedness, and gender biases, the functional imaging database reflects those of us who live in the urban, developed world. We do not yet know whether there will be differences in the development of neural networks between individuals who have significantly different lifestyles. Will the networks of a hunter-gatherer in the Arctic resemble those of a university student who relies on supermarkets to meet basic food needs and whose daily tool use revolves around a touch-screen phone? Probably not, is the answer. We know that our brain responds quickly to changing environmental stimuli and work routines. Studies of taxi drivers, musicians, and mathematicians show they develop especially expanded networks in particular regions of the brain that reflect the demands of their respective jobs (Draganski and May 2008; Debas et al. 2010). Brain scans of long-term users of chopsticks in Japan reveal that they have developed enhanced neural networks linked to holding the tools, and the perception that they are natural extensions of the hand (Tsuda et al. 2009). Such a study begins to address the issue of the skill gap between contemporary urban subjects and those who live in nonWestern societies where skilled manual tasks remain part of daily routines. There is another issue lurking in the undergrowth when we consider applying the results of brain scans to the evolution of tool use. There are very few expert makers of stone tools available for study and fewer living as hunter-gatherers. The relevance of this point is seen in an fMRI-based comparison of brain activity between expert and non-expert chess players. Experienced players used both hemispheres of the brain compared with the largely left-brain dominance among the less skilled players (Bilalić et al. 2011). The experts had added processing power at their disposal which gave them their greater speed of recognition of the chess pieces and ability to plan their moves far ahead of the novices. That kind of experience-based knowledge is relevant in any attempt to map the neural networks involved in making stone tools, not to mention the added components of hafts and handles. Even if we use expert modern knappers there is tantalizing evidence that hunter-gatherers and farmers do differ in their perceptions of three-dimensional space and reckoning of causality (Boesch 2007), so potentially they have differently developed neural networks. The cross-cultural database is very small,

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but illustrates the importance of extending experiments beyond the usual sampling of students.

Apes and Monkeys in the Scanner One fruitful avenue for generating an evolutionary perspective on tool use is experimentation with other primates, especially tool-using apes and monkeys. Chimpanzees are well-known users of tools in the wild, and functional imaging research enables us to identify those areas of the brain that have evolved in humans since we last shared an ancestor with chimpanzees some 6–7 million years ago (Iriki and Sakura 2008). We can also observe similarities in brain structures that are engaged during tool use and communication to see whether there are common and deep roots (Taglialatela et al. 2008). Working with these animals does have its practical challenges. A monkey is not going to lie still inside a scanner, and given the sensitivity of current equipment to movements of the head there is little realistic hope of recording real-time responses to actions. Instead, the subjects are immobilized and anaesthetized before undergoing scanning (Phillips and Hopkins 2007), and experiments are designed to record any changes to neural structures resulting from training or testing (Quallo et al. 2009). Comparative studies have been made of differences in neural activity between groups of New World capuchin monkeys that are habitual tool users and those that are not (Phillips et al. 2008), but to date the greatest amount of research on primates has involved macaques, and in particular Japanese macaques. These monkeys are not regular tool users in the wild, but can be readily trained to use tools and the changes in neural activity observed (Quallo et al. 2009). Research among macaques led to the identification of ‘mirror neurons’ which respond to the sight and sound of another monkey performing a task, and which prepare the monkey to imitate those actions (Kohler et al. 2002; Rizzolatti and Craighero 2004). These clusters of neurons may be critical components in the social learning of tools among primates generally, and in the evolution of human language (Corballis 2002; Aboitiz 2012). A consensus has emerged that they exist in humans and play a central role in our ability to

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recognize and understand what others are doing (Valyear and Culham 2009; Mukamel et al. 2010).

Restricted Movement The final limitation to be discussed is mechanical and will presumably be resolved in time, but for now it places real constraints on experimental design for humans as well as other primates. As mentioned, current imaging techniques scan the brains of subjects who are either lying or sitting still—not the ideal postures for replicating the tasks involved in making and using tools. Minimal movement of the head is required to ensure clarity of the images. Although image resolution is good with fMRI and PET scans, they are slow when compared to EEG in recording changes in activity over time (Lewis 2006), and movement compounds this limitation. As a result, studies of tool use must rely on either pretend (pantomimed) tool use or very restricted manipulation within the scanner chamber. Pantomimed tool use has its obvious limitations and comparative imaging reveals them: holding an actual tool activates areas of the brain involved with assessing the correct grip, whereas an imagined or acted tool provides much less precise information on the grip (Laimgruber et al. 2005). Pantomimes also involve a degree of abstraction in the process of imagining a tool which might activate extraneous networks and produce spurious results. On the plus side, pantomime does activate many of the same networks of the brain engaged in real tool use, at least in the planning stages (Hermsdörfer et al. 2007).

IMAGING TOOL-MAKING AMONG HUMANS Limitations aside, functional imaging research is leading to a much clearer understanding of the shared networks and structures linking complex tool use with language. That evidence supports a growing consensus that these two realms of behaviour co-evolved (Stout and Chaminade 2012). The collaboration of archaeologists with neuroscientists has been particularly important in developing experiments that work with the various limitations of the technology to address issues about the cognitive evolution of technology. The pioneers in

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this approach were archaeologists Nick Toth and Kathy Schick at the University of Indiana (Toth and Schick 1993). Their former student Dietrich Stout has expanded on this framework using a variant of PET scanning and the results will be described shortly, but first a word on their limitations before we draw conclusions relevant to hafting. These pioneering studies, as with other scanning-based experiments, involve few participants, and in the case of the expert stone knappers they practise their skill as academic researchers rather than as habitual users of stone tools. More problematic is the current state of scanning technology, which makes it difficult to capture the true complexity of hafting in an experimental setting. No one has yet to try and replicate the hafting process under these conditions. As a result the inferences drawn here about the neural basis of hafting come from the study of hand-held stone tools. There is another technology currently available—functional transcranial Doppler ultrasound (fTCD)—that is relatively unaffected by movement and is a non-invasive means of measuring blood flow in the brain. It has been used by psychologists studying differences in brain hemisphere activity during speaking (Groen et al. 2011), but it lacks the resolution of the scanning techniques. The ideal imaging tool would be portable, move with the user, and still record clear details of brain activity in real time. Such a device could be taken into the field and applied to skilled tool makers who still make hafted tools. A cross-cultural database could then be generated and comparisons made by task and tool type. That prospect seems a distant goal, but rapid advances are being made in imaging techniques, and we just need to look at the sociology of invention to predict that it will probably happen as and when the necessary economic and political conditions are in place to make it both desirable and feasible.

Two Streams in the Brain The left hemisphere has long been accepted as the portion of the brain most involved in the planning and preparation for tool use, and the right primarily involved in executing plans (Lewis 2006) (Fig. 2.1a). Before the advent of neuroimaging techniques, evidence for hemispheric specialization in tool use came from clinical studies of subjects with brain impairment; now, the areas and networks affected can

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Fig. 2.1 (a) Anatomical areas of the left-hemisphere cerebral cortex, including numbered Brodmann areas (BA), main lobes, and fissures. The occipital lobe (visual cortex) is the proposed starting point of the two streams that are engaged when we plan and make tools; (b) the sub-cortical structures of the limbic system (e.g. thalamus, basal ganglia shown here, plus the amygdala and hypothalamus) and the cerebellum are also closely integrated in the planning and making of tools. (Constructed from images freely available on Wikipedia Commons.)

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be pinpointed with functional imaging. Damage to the left parietal cortex causes apraxia, a disorder that affects recall and use of learned skills (Johnson-Frey 2004). Some apraxics lose the ability to associate the correct tool for the job, but retain knowledge about how to use a tool (Mizelle and Wheaton 2010). Others recall which tool to use when, but have lost the motor skills needed to use a tool properly. Lesions on the parietal lobe also interfere with the human capacity for technical reasoning when faced with unexpected situations (Goldenberg and Spatt 2009). These forms of apraxia demonstrate that practical skills can be separated from conceptual knowledge, and are associated with different, though overlapping, portions of the left parietal cortex (Goodale et al. 1994; Johnson-Frey 2004: 72). The separation of action and perception in brain-damaged humans supports an influential hypothesis that primates in general have two neural pathways for processing visual information (Ungerleider and Mishkin 1982; Goodale and Milner 1992). The pathways leave the primary visual cortex in the occipital lobe (Brodmann area 17) and separate into two streams of networks that link regions of the cerebral cortex. The ‘ventral stream’ leads to the lower temporal lobe cortex (see Fig. 2.1a) and carries information about an object’s identity (e.g. size, shape, colour, texture). (The ventral stream is active even with the eyes closed.) The ‘dorsal stream’ connects to the parietal lobe cortex and processes information about an object’s spatial location. These two kinds of information—what an object is and where it is— are essential for skilled tool use. As might be expected, the streams interact and exchange their information and both link with the prefrontal association area where other sources of information, such as working memory (below) are incorporated into planning tool use (Frey 2007: 369). In the left hemisphere, the prefrontal cortex assesses the likely physical demands of a task and this information is passed to the parietal cortex where it is integrated with information about the tool, its location, plus input from the hands and limbs (Buxbaum et al. 2006). The appropriate grip for the task is then selected in the parietal cortex (Frey 2008). This overlap in neural networks supports the hypothesis that both streams are integral to complex tool use (Frey 2007: 371). The two streams model has been tested, refined, and supported by neuroimaging studies (Goodale 2008; Bilalić et al. 2011), and there is evidence too for pathways of connective tissues that link the temporal and parietal lobes, and so potentially the two streams (Ramayya et al.

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Fig. 2.2 Brain imaging research has identified the cortical networks involved in tool use and speech. Spatial and sensory information flows in both directions from the back to the front of the brain. It is in the frontal region of Broca’s area (BA44–BA45) that this information is assembled into hierarchically structured sequences for both language production and comprehension and the making of complex tools. These two areas constitute the inferior frontal gyrus (IFG). (Reproduced from Stout and Chaminade 2009 with permission of Dietrich Stout and the Cambridge Archaeological Journal.)

2010). There is an alternative model of a single interconnected stream which can separate action and perception depending on the kinds and duration of stimuli (Cardoso-Leite and Gorea 2010). For our purposes, the existence of one or two streams is less important than the realization that our ability to recognize tools and their use involves closely interconnected neural networks (Valyear and Culham 2009). We could not make or use complex tools appropriately without both sets of information. Where these

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streams connect to the frontal region there is an area of cortex of great importance for enabling hafting, the inferior frontal gyrus (IFG) (Fig. 2.2). The functions associated with this ridge or fold include speech production (Broca’s area) and the processing of hierarchically structured sequences in a range of activities including performing music, solving mathematical problems, and making complex tools (Koechlin and Jubault 2006; Higuchi et al. 2009). Hafting, of course, is this kind of sequentially organized activity.

PET Rocks The role of the IFG in tool-making has been identified over the course of several scanning experiments involving volunteers making stone tools (Stout and Chaminade 2007; Stout et al. 2008) or observing them being made (Stout et al. 2011). The making of simple flakes, much like those found in the early archaeological record, activated the dorsal stream but very little of the IFG (Stout and Chaminade 2007). The inference here is that little in the way of sequential thought is needed to strike a flake from a core using a hammer stone. Making a much more carefully shaped and thinned cutting tool (a hand-axe; see Chapter 4), on the other hand, does involve considerable planning, especially of the sequence of flake removals. That planning draws on craft knowledge gained from practice. The skilled knapper knows from experience what will be the likely outcome of each hammer blow as assessed against an imagined target shape. Adjustments can then be made with subsequent flake removals. The whole process also requires good visual and spatial awareness, and unsurprisingly the IFG in the left hemisphere is engaged with the two streams (Stout et al. 2008; Stout et al. 2011). In the right hemisphere, the IFG equivalent or homologue is involved in coordinating this protracted series of manual actions (Stout and Chaminade 2012). More generally, when it comes to active tool use there is imaging evidence that both hemispheres are engaged (Lewis 2006; Hermsdörfer et al. 2007: T116; Bilalić et al. 2011), whereas there is a left-hemisphere bias in the perceiving and planning of tool use (Lewis 2006; Goldenberg and Spatt 2009). Staying with the left hemisphere, the fact of the IFG’s involvement in speech production and the planning of tool use lends considerable support to long-held speculation that these two activities evolved in

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tandem (Darwin 1879; Holloway 1969; Greenfield 1991; Corballis 2002). Broca’s area has received much attention in the past as the primary functional area associated with speech production (e.g. Greenfield 1991), but we now have a much fuller understanding of how abstractions in the IFG are transformed into speech and tools. The work of Stout and colleagues provides the basis for speculating that hafting with its elaborate production sequence depended on a well-developed mental model of causality, but also piggybacked on the structures that supported language production (Gibson 2007; Glenberg and Gallese 2012). The two evolved hand in hand as well as by hand on handle. But this hypothesis remains to be tested.

COGNITIVE FOUNDATIONS—KINDS OF MEMORY The ability to plan and make complex tools has one more vital ingredient—a good memory. If you want to make a hafted knife, then you will need recall of the properties of the raw materials used to make the handle, the binding, and the knife blade itself. Recall is needed as well of where these materials are found, and how they should be prepared in advance of combining them into a single tool. And as you shape and assemble the components you will be using another kind of memory that comes with practice. You will make subtle adjustments to your posture, arms, and grasp—the body schema in other words—in response to your immediate surroundings. These many actions are likely to be separated by hours if not days and weeks, depending on the task and materials involved. This kind of episodic activity means holding and retrieving information as well as having imagination and patience. We are all familiar with the difference between the short-term recall of where we left our keys and the long-term memory of the faces of friends and family. Brain-imaging research shows that these different kinds of memories are in fact stored in separate but interacting networks (Roy and Park 2010). Like the two-streams model, the evidence comes from the neuroimaging of brain-impaired individuals, and from the study of monkeys. If you have read Appendix 1 then you will have fresh in your memory the three sub-cortical areas

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engaged in learning and using tools: (1) the cerebellum which is active in the acquisition and storing of manual and verbal skills (Quallo et al. 2009; Barton 2012); (2) the thalamus and the basal ganglia which play critical relay roles linking brain and body; and (3) the hippocampus, another deeply buried structure within the brain which forms part of the so-called ‘emotional’ area of the brain or limbic system that seems to control our ability to recall facts and recent events (see Fig. 2.1b). Patients with damage to this area are not only unable to recollect the past, but also have an impaired ability to imagine future events. The hippocampus is also involved in storing memories based on repeated experience. London taxi drivers are renowned for having ‘the knowledge’, which is their memory of the streets of the city and the fastest routes from A to B. They also have more grey matter in their hippocampus than the rest of us (Maguire et al. 2000).4 The most informative evidence for the role of the hippocampus in tool use comes from individuals with impaired memories. In one case, damage to this part of the limbic system affected the individual’s ability to recall the physical properties (colour and function) of a newly learned tool (Roy and Park 2010). Less severely affected was the memory of how to grasp it correctly and how to use it skilfully. Amnesia in this one individual did not affect access to long-term memory, the kind generated by repeated tool use, and which seems to work through a separate neural network that links the frontal cortex with the basal ganglia (Alexander et al. 1986). Other studies have since lent support to the existence of separate networks based on observations of individuals with Parkinson’s, Alzheimer’s and Huntington’s disease (Roy and Park 2010: 3,027).

Constructing memory The capacity to form complex objects and ideas is thought to operate on an expanded form of short term memory called ‘working memory’ (Baddeley 2007). Working memory is often described as the equivalent to a computer’s clipboard; it allows you to hold additional

4 The use of automated navigation aids, such as SatNav, may have an impact on the hippocampi of London taxi drivers, but they will still need to rely on experience to find those shortcuts through the backstreets at rush hour.

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material in your mind, temporarily, until needed (Read 2008). Having extra information and ideas on tap means you potentially have more options available for problem solving. Working memory is also activated in multitasking, which as any cook knows is an essential ingredient for preparing a three-course meal from scratch. The neural foundations of our working memory are not fully understood, but areas of the prefrontal and premotor cortex are known to be involved (Brodmann’s areas 6, 9, 44–7) (Blumenfeld and Ranganath 2006) (see Fig. 2.1a). These same areas of the brain are also engaged in building long-term memories. The chimpanzee’s limited working memory, when compared with ours, may account in part for its inability to make complex, multi-component tools. By extension, a well-developed working memory is probably necessary for managing the many tasks in hafting, and perhaps complex language. Archaeologist Stanley Ambrose (2010) has developed this observation further and makes the compelling case for recognizing a subset of working memory called ‘constructive memory’ in the invention of hafting. This kind of memory is also based in the prefrontal cortex and enables planning and imagining the future as distinct from just storing information (Schacter and Addis 2007). The idea of a memory involved in imagining the future seems counter-intuitive, but thoughts about the future are drawn from personal experience, habits, and general knowledge, which are all forms of memory. There are parallels with the invention of hafting. The tool has to be imagined before it can be made, and the actual making of the tool will draw on these other forms of memory. This degree of extended foresight involves mental time travel, and may be uniquely human (Suddendorf and Corballis 2007). It certainly is needed to make a hafted tool given the likely separation of materials in time and space. Ambrose suggests constructive memory co-evolved with complex (grammatical) language, and had the knock-on effect of enabling humans to form and maintain long-distance social networks in risky environments. Out of sight does not mean out of mind for those with the facility for constructive memory. These are interesting speculations that await the development of neuroimaging studies to test the proposed link between hafting and complex language.

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An Extended Mind There is one more form of memory that deserves mention here but which does not actually reside in a single brain. The concept of the ‘extended mind’ recognizes the importance of other people and tools as carriers of information (Clark and Chalmers 1998). The smartphone is a prime example of a technology which stores data that used to be held in the memory (e.g. phone numbers, birth dates), but also give us access to the Internet and its ever-expanding well of information. In the modern world the partitioning of tasks into specialized roles has been a necessity and consequence of urbanization (McLuhan 1964). We rely on others to remember certain things and to act on that knowledge on our behalf, such as doctors, lawyers, and refuse collectors. One consequence has been a rapid acceleration of technological development as expertise becomes focused and manufacturing more automated. Very few of us need to know how the tools we use are made, or are capable of understanding their workings (Taylor 2011). Tools themselves can trigger associations and specific memories. We associate a bread knife with food, the act of cutting, and maybe the need to add bread to the shopping list. In the context of the Middle Pleistocene world in which hafting was invented, a tool would be a reminder of a future action and supporting tasks. An adze may signal wood-working or perhaps the butchering of a carcass which in turn is a reminder of the need to go hunting. As new uses for hafted tools were envisaged so too could new tools be imagined in a spiral of linked innovations. A knife needs a sheath to protect its edge and the user from damage; the sheath needs to be attached to the wearer to keep the hands free and a cord is made into a belt, and so on in the chain of innovations that arise to solve new problems. The combinatorial principle as embodied in hafted tools becomes both a form of distributed memory and source of innovation.

TOO CLEVER BY HALF Neural networks underpin another cognitive ability critical in the process of invention and innovation—creativity. A creative idea is one that is novel and useful in a particular social context (Flaherty

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2005: 147). This simple definition has an inbuilt slipperiness. It recognizes the inherent variability that is likely to exist between communities about what qualifies as novel and useful. Creativity is contingent on time, place, need, and tradition. The fact that something also has to be useful excludes those ideas that have no accepted or agreed application. Again, this judgement is context-specific. A hafted knife would probably be judged useful in the context of butchering a large carcass when the existing option was a small flake of stone. Creativity is also a process rather than just a bright idea. The process involves the ability to perceive novel structured relationships between objects and ideas, and then to develop that understanding in a systematic way that can be applied to solving problems (Heilman 2005: 150). To ‘think outside the box’ expresses the intuitive sense that creative solutions can arise from looking at old problems from new perspectives. Psychologists use the term ‘divergent thinking’ in recognition of that ability to make novel combinations of ideas drawn from differing areas of knowledge or experience. The invention of the microwave oven from knowledge of early radar technology is a case in point in which the inventor recognized the potential of this source of radiation to cook food (see Chapter 1). Technological inventions are founded on deep craft knowledge of the properties and behaviour of differing materials in differing situations (Arthur 2009), but the divergent thinker—the inventor—must also be able to abandon the tried and tested ways of doing things when faced with an apparently intractable anomaly, and be persistent. The stereotypical ‘mad genius’ who shows an obsessive energized ability to block out all distractions and focus on one idea, or invention, represents part of the creative continuum (Jung et al. 2010). We are all capable of performing creative acts when faced with conceptual and practical challenges, and have experienced the satisfying flash of insight that says you have solved a particularly frustrating problem. It might be an almost instantaneous response to a problem at hand, or, in the case of an invention, the result of a long period of gestation.

Creative Engineering The creative processes can be applied to problem solving in any context, and in the case of the origin of hafting we are interested in

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the neural structures and networks supporting the initial insight that familiar but functionally separate objects could be modified and combined into something new. We now know that the left and right hemispheres have closely supporting roles in the planning and use of tools, and in the case of creativity it seems that connectivity is also key (Heilman 2005: 99, 151). As with language, there is no one single structure involved in creative problem solving. Lesion studies and neuroimaging research highlight the interdependence of the hemispheres in the creative process, and have identified important connections with the limbic system (Flaherty 2005). The limbic system seems to be involved in stimulating an individual’s creative drive in the form of self-motivation to improve skills, and stimulating the number of ideas produced (Flaherty 2005: 149). Most studies of creativity have examined it as applied in the visual and performing arts, language use, and mathematical reasoning. Making things—practical problem solving by engineering—is noticeably absent from current investigations of creativity, which probably reflects our cultural bias about the value of making things with the hands. At the risk of repetition, so few of us make things any more that we devalue manual skills, that is, when we do give them any thought. The separation of arts from crafts is revealing. In the largest imaging study to date, sixty-one college students were tested for their general creative ability and specific ability to extrapolate as many solutions as possible to a problem within a fixed time period (Jung et al. 2010). The tests were based on questionnaires and so did not engage the body as would a real-life tool-related challenge. Putting aside the limitations of age, cultural bias, and experimental design, the results reveal a complex interplay between both hemispheres and also highlighted regions with either more or less cortical thickness associated with higher creativity scores. Some overlapping areas can be identified with tool use and language, particularly in the left parietal cortex, but these may just reflect the use of language skills in answering the questionnaires. More significant is the evidence that the thinning of grey matter in the left frontal and parietal lobes, which accelerates through childhood into adolescence, is associated with more efficient information flow between these brain areas and with greater creativity (Jung et al. 2010: 404). The left orbitofrontal cortex (approximately BA 10, see Fig. 2.1a) is one part of this larger association area found in both hemispheres that receives inputs from the senses, including the sight of objects (and faces), but also their

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sound, smell, taste, and feel (Rolls 2004). The visual input comes through the same network involved in identifying the physical properties of an object (the ventral stream), and so we can expect the orbitofrontal cortex to be engaged in the planning and use of tools. The many interconnections of this cortex with areas of the brain involved in memory and emotion (e.g. amygdala, hippocampus, and especially the hypothalamus) (Kringelbach and Rolls 2004) make it particularly interesting in the understanding of the creative process, which ought to include technological innovation. The association of pleasure, pain, or disgust with an activity, and the memory of these emotional reactions, play an important part in learning as well as in making judgements about what are appropriate responses to changing situations (Rolls and Grabenhorst 2008). The orbitofrontal cortex looks to be a central player in our ability to set and change goals as circumstances change (Jung et al. 2010: 406). That flexibility feeds into the creative process of generating ideas linked to problem solving. To indulge in unsupported speculation for a moment, the orbitofrontal cortex may also contribute to the process of learning to make tools and deriving pleasure from their skilled use. Given that this area of the cortex transforms sensory inputs into feelings of reward or satisfaction, and given tool use engages all senses (even taste at times, as any cook knows), then strong reinforcing associations might emerge between tools and their actions. The smell of furniture polish and the sight of a clean surface are the learned sensory rewards for the effort of polishing a table. (Whether they are reward enough is another matter.) A neatly knitted scarf or immaculately cut lawn may evoke feelings of a job well done. These may in turn be reinforced by pleasurable associations such as the softness of the wool or the sweet smell of the grass. Such pride and enjoyment in tool use might be a rare experience for most of us today, but would have been the norm in pre-industrial societies. The application of neuroscience to the study of creativity (and emotion) is still in its relative infancy compared with work done on the subject by philosophers and psychologists. A conceptual barrier has been crossed, though, with creativity seen as a set of behaviours amenable to the tools of cognitive neuroscience (Jung et al. 2010: 398). Much work has already been done on the neural substrates involved in tool use (e.g. Lewis 2006; Frey 2008), and perhaps there is scope now to encompass creativity into the analysis. The process of

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innovation involves perception, planning, action, and imagination coming together to create something novel and useful. It is also time to devise experiments that involve skilled tool users not just the more accessible college cohort. No doubt, when the day comes that portable imaging devices become available, our neural maps will illustrate the areas and networks activated in the steps from thinking about, making, using, and enjoying tools, and among a broader spectrum of ages, cultures, and levels of experience than is currently feasible. To rephrase and expand the conclusions of Spunt et al. (2010: 72), makers of complex tools are more than moving bodies; they are also moving minds, and those minds are shaped by their social and physical worlds.

THE HAND ON THE HANDLE My left hand is my thinking hand. The right is only a motor hand. This holds the hammer. The left hand, the thinking hand, must be relaxed, sensitive. The rhythms of thought pass through the fingers and grip of this hand into the stone. It is also a listening hand. It listens for basic weaknesses or flaws in the stone; for the possibility of imminence of fractures. Barbara Hepworth 1970 # Bowness, Hepworth Estate

Those familiar with the work of Barbara Hepworth will appreciate her ability to shape stone and wood into evocative forms. Through the tools in her hands she transformed these natural materials into thoughts and feelings. Mind and body worked seamlessly to merge craft knowledge with the skilled movements needed to achieve a desired aim. The hands are central to the body schema of the tool user, whether sculptor or flint knapper, and in this section we look at the evolution of the hand in terms of the dexterity needed to make and use hafted tools. We know well from the work of anatomists how the central and peripheral nervous systems articulate, and from neuroimaging research we see the brain at work as it monitors the senses and coordinates muscular movements. If you have read Appendix 1 you will remember the location of the primary motor cortex (BA 4, parietal lobe) and premotor cortex (BA 6, frontal lobe) either side of the

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central fissure (see Fig. 2.1a), and recall too that the hand, and the thumb in particular, has the lion’s share of dedicated neurons in the motor cortex. That inequality reflects the importance of the hand, and especially the thumb, in our evolution and current status as the most tool-dependent of primates. Our hands provide sensory information about the texture, temperature, shape, and weight of an object, and enable us actively to manipulate our physical and social environments, including communication through gestures (Jones and Lederman 2006). Primate hands serve these same functions but they are also involved in locomotion, and that added functional demand has had a profound limiting effect on primate tool-making capabilities. Darwin (1879) recognized the anatomical freedom afforded to our hands by the simple fact that we walk on two legs. All other primates use their hands in locomotion, whether walking on the ground or on branches, climbing, or swinging (brachiating) from branch to branch. These evolved patterns of movement have configured the size and shape of the hand bones, joint movement, and muscle distribution to support the animal’s body weight. There is less flexibility of the shoulder, wrist, and hand by comparison with humans (Marzke et al. 1992).

The Evolving Hand Dexterity improved gradually after the evolution of bipedalism some 6–7 million years ago, and by roughly 3 million years ago, not long before the appearance of the first stone tools, the hand of at least one species of human ancestor (Australopithecus afarensis) had the capacity to hold and use simple tools (Alba et al. 2003), such as unmodified sticks and stones for nut cracking. Compared with other primates, the modern human thumb is long in relation to the fingers, which enables us to form a range of grips using the thumb and fingers working together (Napier 1965) (Fig. 2.3). A. afarensis had such a thumb, but in other respects its hand retained many chimp-like features that would have restricted the movement of joints and so in the range of grips formed (Marzke 1997). By about 1.98 million years ago, a more human-like hand had evolved as seen in a newly discovered species of australopithecine, Australopithecus sediba, from South Africa (Kivell et al. 2011). The nearly complete hand and wrist of a female was recovered and its anatomy shows an even more

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Fig. 2.3 The human thumb is long relative to our other fingers as seen in this comparison of the hands and digits of the apes. (This image was reproduced from Aiello and Dean 1990 [Fig. 18.2] with the permission of Elsevier Ltd.)

human-like pattern of short fingers and a long strong thumb combined with a more flexible wrist. These features would have been useful for stone tool-making, but there were still some limitations of grip and movement because this species retained an ability to climb trees as well as walking on two legs. The distinctive anatomy that characterizes the modern hand (below) evolved later, by about 1 million years ago in the genus Homo (Tocheri et al. 2008). Although it pre-dated the invention of hafting, it was an essential enabler of innovations in tool-making that would be the precursors to hafting. We will look at these innovations in some detail in Chapter 4, but the critical information now is that the anatomical capacity to create a hafted tool was in place in the ancestor of Neanderthals and ourselves.

The Power Grip A basic distinction has long been made between two categories of grip: power and precision (Napier 1956). When you hold a hammer the handle lies diagonally across your palm and is gripped firmly by the enclosing fingers and thumb (Fig. 2.4). This is the classic power grip and it effectively extends the force and reach of the upper arm. In the brain, the power grip activates a circuit of areas primarily in the left hemisphere (among right handers) that links the premotor cortex and primary motor cortex with those areas of the parietal lobe (BA 5, 7, 40) engaged in the dorsal stream and known to integrate sensory inputs, especially touch and vision (Ehrsson et al. 2000; Gentile et al.

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Fig. 2.4 The power grip used to hold a handle.

2011). The grip’s enabling effect of extending the reach of the arm also extends our mental image of our bodies operating in threedimensional space. The body schema (posture, limb movement) is adjusted to incorporate the tool as an extension of the hand, and that adjustment involves the firing of neurons in the parietal cortex involved with muscle control and engaging visual and spatial memory (intraparietal sulcus) (Maravita and Iriki 2004). To form a power grip requires a long, strong thumb combined with the ability to wrap the fingers around an object (Marzke et al. 1992). The thumb plays an important supporting role, as does the fleshy palm of the hand which acts as a buttress. As well as being long in relation to the fingers, the human thumb has the freedom to rotate across the palm giving us our distinctive ability to touch each fingertip and fleshy pad against the tip and pad of the thumb (full opposability). An opposable thumb gives added strength to the clamp-like power grip, and the grip is enhanced by the flexibility of the palm with its capacity to fold around and mould to an object, something chimpanzees cannot do. The muscles of the thumb and fingers form the pulpy mounds of the palm, and the palm, like the fingers, is ridged, which gives added grip (Napier 1976). The bone sandwiched between the fingernail and pad of each finger (distal phalanx) is wider than in any other primate, and that greater width provides not just added grip, but also enables more surface area of skin to come into contact with an object as the finger pad flattens as the grip tightens. More contact between skin and object means more sensory information being generated about the size, shape, texture, and weight of an

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object. For anyone who has had their fingertip pricked for a blood test, it will come as no surprise to learn that our fingertips are very sensitive, having a denser concentration of nerves than in any other part of the hand (Jones and Lederman 2006: 28). The power grip is central to the very concept and action of hafting. The human hand and wrist are well adapted to the forces generated by hammering, and the ability of the wrist to extend provides added leverage to the clubbing motion by aligning the club with the forearm (Young 2003: 171). The grip evolved long before hafting, and probably existed by 2.5–2.1 million years ago based on hand bones from the South African cave site of Sterkfontein (Member 4) (Marzke et al. 1992). An early evolution would not be surprising given the advantages of being able to use simple unmodified objects such as sticks or long bones as weapons or digging tools.

Precision Grips An opposable thumb and folding palm enables us to form a greater variety of precision grips than other primates. Precision grips involve contact between the thumb and one or more fingers, and sometimes the palm, to manoeuvre, hold, and grip an object (Marzke 1997: 92). In the brain, the variety of precision grips activates extensive circuits in both hemispheres, and especially in the right hemisphere among right-handers in contrast to the left-hemisphere dominance of the power grip (Ehrsson et al. 2000; Kuhtz-Buschbeck et al. 2001). The areas involved in both hemispheres include the expected motor and premotor cortex as well as the parietal areas engaged in judging the spatial location of objects (dorsal stream). An area largely buried within the frontal cortex (cingulate cortex, BA 32), which has connections to the limbic system and the prefrontal association complex, also comes into play in selecting movements based on expected rewards. As you might just recall, the prefrontal association complex was active in monitoring and selecting appropriate movements in relation to internal models of action. The extended neural networks involved in precision grips reflect in part the greater range of grips available, but also the need to integrate spatial and motor skills in the manipulation of small objects. Try picking up a very small thin object, like a pin, without the thumb and index pads touching—it is difficult. Humans are particularly adept at

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using the precision pinch grip between the thumb and index finger (Ohman et al. 1995). Other primates do use precision grips in feeding and grooming, but humans can form much stronger precision grips and more of them (Marzke 1997). We have joints in the thumb side of the wrist that are better suited to distributing the forces generated during a forceful pinch (Tocheri et al. 2008). The human wrist is also uniquely adapted to generating the force and accuracy seen in the motion of throwing a dart (Wolfe et al. 2006; Rohde et al. 2010). That forward snap of the wrist is used by tennis players to add power to the serve and illustrates that this wrist action is also advantageous when applied to objects held in a power grip (the racket handle). The added power and accuracy enabled by the movement of the wrist (carpal bones) contributed to the effectiveness of human throwing. A bowler in cricket or a baseball pitcher uses a precision grip when throwing, and on release of the ball the thumb gives way to the tips of the middle fingers which are the last point of contact, providing a final touch of thrust and guidance (Young 2003: 170). This same grip is used when throwing a stone or using a stone as a hammer to remove flakes from a block of stone. The sports-minded reader has probably already thought about the grips used to hold the variety of tools deployed to score points in a competitive game (some but not all include basketball/netball, golf, American football, rugby, pool/snooker, table tennis, bowling, badminton, squash, volleyball, hockey [ice and field], polo, jai-alai, and not to be forgotten, lacrosse). Soccer (football to most of the world) is one of the few sports in which the feet are the primary tool-using appendage.

Precision Tool-Making The flexibility allowed by the articulation of our finger, thumb, palm, and wrist joints also enables us to manipulate objects in one hand more easily, an ability that is particularly useful in tool making (Marzke 1997). We take these manipulative abilities for granted as we use them without conscious effort, but they have co-evolved along with our increasing dependency on tool-making. A small number of variants of the precision grip are involved in making the most commonly found stone tools in the early Stone Age archaeological record of Africa, Europe, and parts of Asia, namely flakes and hand-axes. The act of striking a stone core with a stone

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hammer to remove a sharp flake involves both hands, one to hold the core and the other the hammer. The dominant hand, the right hand for most, holds the hammer in a grip that involves three fingers and the thumb (the ‘3-jaw chuck’ grip, commonly used to hold a round object like a ball or remove the lid from a jar). Removing a flake involves coordinating the angle and force of the blow of the hammer against the core—a combination of skilled movement guided by visual calculation that certainly improves with experience and training. The hand holding the core resists the impact of the blow, keeping the core stable by using the fingers, thumb, and the palm as a buttress (cradle precision grip) (Marzke 1997: 95). The sequential removal of flakes from a core, or in the shaping of a hand-axe, also involves the non-dominant hand in the act of repositioning of the core to present the preferred edge angle to the hammer blow. Such precision handling engages the muscles of the thumb and the fifth or little finger as shown by measurements of electrical activity (electromyography) during knapping (Marzke et al. 1998). (Watch someone shuffle a deck of cards with one hand to witness an extreme version of human handling dexterity.) Electromyographic data also shows the thumb and index finger to be most active in the hand controlling the hammer stone. A strong pinch grip (thumb pad against side of the index finger) is typically used when gripping a flake and using it to cut a hard material (Marzke and Shackley 1986) (Fig. 2.5). Chimpanzees use precision grips to grab and hold objects, but cannot generate the

Fig. 2.5 The precision pinch grip used for precision work with a flint flake.

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force needed to form a strong pinch grip, and lack the ability to manoeuvre objects skilfully in one hand (Marzke 1997: 97). These anatomical limitations are also seen in the now classic case study of Kanzi, the captive and enculturated bonobo, who developed his own technique of flaking stone—throwing a core against a hard surface— to compensate for restricted precision control of hammer stone and core (Toth et al. 1993; Schick et al. 1999). The precision grips used by humans to make flakes and shape hand-axes cause relatively little muscle fatigue or pain in the hand joints, that is, once you have graduated beyond the beginner’s propensity to make jarring mishits. Precision handling also improves the efficiency of knapping as one-handed core reorientation takes place almost unconsciously with the skilled knapper for whom there is little need to stop and manually move the core before resuming knapping.

The Hand in Perspective The human ability to knap stone effectively and efficiently with little damage to the joints suggests a co-evolution between technology and anatomy (Marzke 1997). As joint mobility improved in response to the repetitive stresses of knapping and tool use, these activities became more effective and further embedded as habitual behaviours. The making of flakes, after being universal among human societies for 2.6 million years, has now been reduced to a marginal and dying practice among a handful of communities in remote regions. During most of this time span hand-held tools were the norm, with the development of hafting being comparably recent in human evolution. The human precision pinch grip involving the thumb and finger pads was not needed to make flakes or hand-axes (Marzke and Shackley 1986; Marzke 1997), but looks to have been critical to hafting small objects in the later archaeological record (Napier 1965). This grip would also be used in binding a stone axehead to a handle (Marzke 1997: 96), as was the case among the adze makers of New Guinea studied by Beatrice Blackwood (1950). They used a pinch grip to bind tightly the axe blade to the haft with cord made from plant fibres. Given that the anatomical capacity to form precision grips existed before the invention of hafting, the precision pinch grip in particular was co-opted for hafting and presumably the human hand and

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hafting subsequently co-evolved as small-object manipulation became an increasingly important part of combinatorial technologies. Experience as well as anatomy plays a formative role in conditioning our muscles and mind to routine activities. New manipulative routines arose with hafting to accommodate the step-wise process of combining separate components to make a whole tool and with them changes to the ever fluid neural monitoring of the body schema. Not to be forgotten in this speculative link between anatomical, neural, and technological evolutions is the importance of the facility for precision handling. The ability to reorientate objects in the nondominant hand—the hand holding the core or tool being shaped— and to keep the core stable when struck was already established by makers of hand-held flakes and axes (Faisal et al. 2010). Skilled engagement of both hands would also be needed in the making hafted tools in each of the many steps from start to finish.

TAKING THE LONG VIEW ON THE EVOLUTION OF THE BRAIN This chapter has been largely about the brain and its structures that support the ability to plan and make complex tools. To consider those structures from an evolutionary perspective, that is, to estimate when the neural capacity for complex tool-making had evolved, we would ideally examine well-preserved brains representing a range of human species over time. But neurons and connective tissues do not fossilize, at least not from the early human record. How then to reconstruct the likely evolution of left-hemisphere dominance in planning tool use, or the role of the prefrontal cortex and any other association areas involved in conceptual networks? The answer lies in a comparative approach that integrates multiple lines of neural, behavioural, and genetic evidence derived from extinct and living species (Schoenemann 2006). The evidence would ideally include data from fossils, from living primate species, from artefacts themselves, and all enveloped within a well-dated framework that pinpoints in time the where and when of mental evolution (e.g. Sherwood et al. 2008). The how and why questions are addressed with the application of evolutionary theory to the data itself.

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The fossil and archaeological records are the two most directly relevant sources of evolutionary information, but also the most limited in terms of the quality of the data available. Casts of the inside of fossil skulls (endocasts), either from natural infill or reconstructed replicas (now using CT scans to make 3D maps), provide information about the size and shape of the brain they once held and, depending on the quality of preservation, also the location of blood vessels and landmark fissures on the cerebral cortex (Holloway et al. 2004). The evidence extracted from endocasts is literally superficial; casts record just the external surface of the brain, and surface details of landmark folds and sulci are likely to be obscured by the protective tissues (meninges) that buffer the brain from contacting the inner surface of the skull. Sub-cortical neural networks and functionally specialized fields do not leave traces on the surface. There are few endocasts given the time span of human evolution; the largest sample available comprises ninety-two specimens that collectively span 3 million years (Holloway et al. 2004), which is on average one specimen per roughly 32,600 years. The geographical and chronological distribution is uneven as well, compounding the problem of unrepresentative sample sizes. Unfortunately, for our purposes, the ancestor of Homo sapiens and Neanderthals, Homo heidelbergensis, is one of the least well represented species. On the plus side, endocasts do offer a means of gauging gross trends in the evolution of brain size and the morphology of the lobes (Bruner 2010) (Fig. 2.6). Of particular interest in terms of complex tool-making and language is evidence for the evolution of the left-hemisphere language areas associated with the IFG and for the expansion of the neocortex and by inference its association areas. The fossil evidence for cognitive evolution also extends, perhaps surprisingly, to the pelvis, a hard bone that like the skull stands a better chance of being fossilized than other more fragile parts of the skeleton. The pelvis offers indirect evidence of the size of the brain at birth, a basis for making inferences about the evolution of the human pattern of an extended childhood that includes time for intensive social learning, including the making of complex tools (Chapter 3). The archaeological record, as the primary source of behavioural data for the past, also suffers from limitations of preservation, particularly of organic tools, leaving a record biased in favour of stone. Stone tools, especially flakes alone, may not represent the full range of cognitive skills and abilities expressed by early humans at any

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Fig. 2.6 Endocranial morphology of fossil humans and an australopithecine reconstructed from digital endocasts: (a) the main cortical areas are shown on the digital endocast of an Australopithecus africanus (Sts5); (b) Homo ergaster (African H. erectus) (KNM-ER3733); (c) Neanderthal (Saccopastore 1); and (d) a modern human (Mladech 1). The endocasts reflect developments in brain size and shape between 3 million and 30,000 years ago. (Image courtesy of Emiliano Bruner and José Manuel de la Cuétara, who retain all rights.)

particular place or time. Current experimental efforts to map the neural networks activated during stone tool-making are vital if robust links are to be made between the evolution of technology and the brain (e.g. Stout and Chaminade 2009), but as noted, the current sensitivity of imaging equipment to movement restricts our ability to assess very active tool-making, such as hafting. The limitations of the fossil and archaeological records have effectively forced neuroscientists to focus on comparative neurological data drawn from human and non-human primates in the effort to understand the evolution of the cognitive foundations of tool use. These data, as discussed in some detail above, highlight the importance of integrated networks in planning complex tool use, with a prominent role for the left hemisphere in the immediate preparation for tool use and the right hemisphere in the step-wise planning. Engagement of both hemispheres is seen among experienced tool users and in the use

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of skilled precision grips as well as in the process of creative problem solving. The various kinds of integrated memory look to be essential for generating abstract goals and maintaining the concentration needed to complete a long chain of actions. We still need the dimension of time to answer the questions posed at the outset of this long chapter. Power and precision grips were in place before hafting, but what about the brain?

Brain size and Adaptability To begin to answer that question, we can look first for evidence of when a large modern-sized brain had evolved. Endocasts provide information on shifts in absolute brain size over time, and when combined with other skeletal data they give a measure of brain-size change relative to body mass (encephalization quotient, or EQ) (Harvey and Krebs 1990). An animal with a big body can be expected to have a proportionally larger brain just to maintain bodily functions, and this trend is seen in the course of mammalian evolution (Jerison 1973). Large brains are energy-demanding organs, so any increase in brain above the expected correlation with body mass is probably signalling active natural selection for increased intelligence (Aiello and Wheeler 1995; Aboitiz 2001). Primates are notable for having larger than predicted EQs when compared with the average mammal, and Homo sapiens have an EQ three times larger than that of chimpanzees (Sherwood et al. 2008). If EQ is taken as a measure of increased information-processing ability and its application to problem solving in different situations, then clearly humans top the chart, and that position has evolved in the 6–7 million years since the split with the last common ancestor with chimpanzees (Alba 2010: 36–7). Establishing the evolution of EQ from fossils is difficult as it requires estimating body mass from incomplete skeletal remains as well as cranial capacity, but there is a convergence of evidence pointing to a substantial increase in relative brain size with the origin of the genus Homo (Ruff et al. 1997), and an increase in the Middle Pleistocene (Rightmire 2004; Alba 2010). By 600,000 years ago, the species Homo heidelbergensis (see Chapter 5) had an average absolute brain size of 1100 cm3, which is at the low end of the modern range (Neill 2007) (Fig. 2.7). Our relative and absolute brain size has increased slowly since then.

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A. afarensis A. africanus A. boisei A. robustus Homo habilis early Homo Homo Homo erectus H. heidelbergensis Archaic Homo sapiens Neandertal Homo sapiens (Modern males) (M0dern females)

400

0 3.5

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Fig. 2.7 The evolution of human brain (cranial) size in the genus Homo, showing the emergence of the modern human size-range in the Middle Pleistocene (c.600,000 years ago). (Image courtesy of Tom Schoenemann, who retains all rights.)

Having a larger brain does seem to make a difference to the survival of a species. In a test of the hypothesis that brain size evolves in response to novel or changed environments, large-scale observations were made of birds introduced to new habitats (645 introductions of 195 species) to see how they responded to the challenges of finding food and shelter in unfamiliar surroundings (Sol et al. 2005). Those with the largest relative brain sizes showed the most innovative behaviours and were most successful in becoming established. Numerous variables had to be controlled to make these comparisons, and the results cannot be transposed directly onto our evolutionary past, but the large sample size hints at a robust proposition. A big brain is probably always an advantage to a species, and among mammals a major constraint on the long-term expansion of brain size is ecological (Schoenemann 2006). Big brains are energetically expensive organs, and for humans the energy demands are especially high in childhood and then remain roughly constant as adults. We have been successful in reducing ecological constraints on brain size by improving the efficiency with which we extract energy from the habitats in which we live (Fonseca–Azevedo and Herulano–Houzel 2012).

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Technology has played a key role in this evolutionary process along with our capacity to form cooperative social groups that collectively meet the needs of its members (see Chapter 3). Increasing climate variability in the Middle Pleistocene may have been an additional driver of cognitive evolution (Potts 2001), including the invention of combinatorial technology. We will look at that nexus in more depth in Chapter 4, but for now relative brain size is just one indicator of intelligence and brain organization is another. As we know from the functional anatomy of the brain, the association areas play critical roles in thinking and executing actions, including complex tool use. These and other higher-order functions are rooted in the neocortex and this area of the brain has expanded by a factor of 6.6 compared with the rest of the brain (Neill 2007: 193). The frontal cortex accounts for 39 per cent of our neocortex, a larger proportion than in any other primate (Sherwood et al. 2008: 433). The frontal lobe includes not just the premotor cortex, but also the prefrontal cortex that plays a central role in decision-making, planning, controlling emotions, working memory, and of course language (Broca’s area and part of the IFG). The prefrontal cortex connects with the visual streams involved in identifying the attributes of objects and judging their spatial location. The underlying orbitofrontal cortex looks to play a critical role in generating creative behavioural responses to environmental challenges (Kringelbach and Rolls 2004; Jung et al. 2010). An expansion of the frontal lobe, then, has particular relevance for estimating when the cognitive capacity for making complex tools was in place (Semendeferi et al. 2010).

Brain Shape Ralph Holloway has spent much of his career studying endocasts and has argued since the 1960s that a human-like reorganization of the brain was underway before the evolution of the genus Homo about 2.3 million years ago, with evidence for a relative expansion of parietal association areas among australopithecines compared to that of living apes. By 1.5–2 million years ago among specimens of Homo there is evidence for the neural foundations of language (Broca’s area) and complex behaviours supported by an expanded frontal lobe (Holloway et al. 2004). These interpretations of a mosaic evolution of different parts of the brain have generated articulate and well-

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supported challenges by those who see a more integrated rather than piecemeal enlargement of the brain of Homo (e.g. Falk and Clarke 2007). More recent studies focusing on changes within the human genus reveal that the modern pattern of wider frontal, parietal, and temporal lobes (compared to australopithecines) had evolved in Neanderthals and early modern humans by 150,000 years ago (Bruner and Holloway 2010). The widening of the frontal corresponds to the prefrontal cortex. The expansion may reflect an increase in grey and white matter as well as a reorganization of an evolving prefrontal cortex, or perhaps a shift in neural mass as part of a reshaping of the base of the skull (Ibid; 145). These differing interpretations remain in play, but regardless of their resolution the modern size and shape of the neocortex had evolved and so, presumably, had the linked frontal and parietal association networks (Bruner 2010) (Fig. 2.6). Earlier studies showed similar patterns in the widening of the parietal lobes among Neanderthals and modern humans (Holloway 1981; Bruner et al. 2003), and by inference an expansion of the neural networks we see today engaged in the planning and making of complex tools (the dorsal and ventral stream model). Given that H. heidelbergensis is the likely ancestor of both Neanderthals and modern humans (Rightmire 2004), then we can expect endocasts of this species to show similar patterns of frontal and parietal widening.

LOOKING FOR LANGUAGE IN HANDEDNESS AND GENES As mentioned many times already, the evidence from neuroimaging research points ever more convincingly to complex tool use and language as having evolved together (Frey 2008; Meyer et al. 2011; Stout and Chaminade 2012). There is another source of supporting evidence for this co-evolution that comes from the well-argued linkage between handedness, language, and technology (Gibson 2007). In modern Westernized populations, about 90 per cent of individuals use their right hand for skilled tasks, with the left hand in a supporting role (Guiard 1987). That preferred use of the right hand for precision grips is seen not just in the urbanized developed world but also

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among a sample of hunter-gatherers, herders, and subsistence farmers (Marchant et al. 1995). There is some geographical variability in the percentage of right-handedness among such ‘traditional’ societies, but in all cases it is by far the dominant hand (Faurie et al. 2005). It seems to be a universal and evolved human trait, and one that has a left-hemisphere neural basis. As a reminder, the planning, making, and use of tools activates distributed networks in the left hemisphere (Frey 2007, 2008), and that seems to be the case for many, but not all, left-handers (Lewis 2006). The right hemisphere looks to have a supporting role in coordinating spatially orientated tasks, such as moving chess pieces around a board (Bilalić et al. 2011) and in forming precision grips (Ehrsson et al 2000). Other primates show less consistent right-handed preference, but there are some righthanded tendencies when complex tasks are involved requiring precision and the use of both hands in different roles (Uomini 2009; Mosquera et al. 2012). The association of left-hemisphere dominance of handedness and language comes from the shared neural networks in the left prefrontal cortex and left temporal lobe that support the production and understanding of language (Hickok and Poeppel 2007). Overlapping lefthemisphere networks are involved in planning tool use and in making gestures with the right hand (Frey 2008). Language may have evolved through stages of increasingly complex manual actions learned by imitation, gesture, and then speech (Corballis 2002). An initial imitation of actions, supported by mirror neurons, developed into gestural signing representing complex sequences of actions. Social learning was involved in each stage, and especially with the development of sounds as symbols and word order to express more abstract thoughts. The shift to speech involved the left-hemisphere vocal network, and with it right-hand dominance (Arbib 2005; Aboitiz 2012). In this model of a gestural origin, any evidence for the preferential use of the right hand in the archaeological record is evidence for at least a protolanguage stage. There are other models for the linkage of handedness and language (e.g. Bradshaw and Nettleton 1982; Gibson 2007), but this has the potential for testing by the archaeological and fossil records.

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The Archaeological Evidence of Handedness The early archaeological record provides some indirect evidence for the appearance of right-handedness, though most claims (e.g. Toth 1985) have been shown to be based on unreliable methods or on approaches that have not been validated by large-scale controlled studies (see Cashmore et al. 2008 and Uomini 2009 for reviews). One avenue of study supported by experimental data is the spatial patterning of stone waste created in the process of knapping a core. Recall that for right-handed individuals, the hammer is held in the right hand with a 3-jaw precision grip and the core in the left hand in a supporting role. The distribution of knapping debris can reflect the handedness of the knapper, but the pattern is affected by the position of the knapper (Wenban-Smith 1997). A seated knapper produces a different pattern to one who is sitting directly on the ground, and if a protective pad is used it can disrupt the shape of the scatter (Newcomer and Sieveking 1980). Rarely in the archaeological record are intact knapping scatters preserved, but a notable exception is the site of Boxgrove, Sussex. Here, 500,000 years ago an individual sat on the ground and knapped a flint core leaving a typically right-handed scatter (Roberts and Parfitt 1999) (Fig. 2.8). The Boxgrove scatter is attributed to Homo heidelbergensis, and there is much more abundant evidence of right-handedness with this species, and for Neanderthals, in the fossil record. Teeth are the unlikely primary source of data, more specifically cut-marks on teeth created during tool use. The mouth offers a useful third ‘hand’ for holding objects that need securing while both hands are engaged. There is ample ethnographic evidence for hunter-gatherers using the teeth as a clamp to hold meat or hide while it is being cut into strips (Lalueza-Fox 1992) (Fig. 2.9). The dominant right hand does the precision job of slicing (avoiding the lips) and the supporting hand holds the other end. Slicing close to the front teeth typically leaves diagonal cuts or striations in the enamel. Experimental replication studies show that the direction of slicing is consistent with hand preference, and so an examination of fossil incisors should reveal patterns in handedness in past populations (Lozano et al. 2009). The largest study of its kind has been made on the teeth of twenty-eight individuals from the site of Sima de los Huesos, Spain (Frayer et al. 2012). In this sample, twenty individuals had cut marks on their front

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Fig. 2.8 Boxgrove (Sussex, UK) flint scatter showing a dispersal pattern of flakes, which is typical of a right-handed knapper sitting on the ground and holding the hammer in the right hand and the core in the left. The scatter is 500,000 years old and the product of Homo heidelbergensis. (Image courtesy of Mark Roberts and copyright the Boxgrove Project.)

Fig. 2.9 The habit of using the teeth as a clamp for holding and pulling taut materials for slicing can leave accidental cut-marks (striations) on the teeth. If we assume that the cutting tool was held in the dominant hand, then the direction of the slice can be used to infer the handedness of the individual.

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teeth, and of these fifteen were found to be right-handed including a child of three to four years, and the remaining five showed no signs of left-handedness. Right-handedness looks to have been established among these early Neanderthals, and there is supporting dental evidence from later specimens of this species (Lalueza-Fox and Frayer 1997; Frayer et al. 2010; Volpato et al. 2012). Look at the racket arm of a professional tennis player and chances are it will be more muscled and larger than the opposite arm. Habitual use of one arm in preference to the other will produce a skeletal asymmetry in upper-limb development as bigger muscles cause the bone to remodel and strengthen. Paired arm bones rarely survive in the early fossil record, but there are enough examples from Neanderthals to suggest that this species was right-handed (Steele and Uomini 2005; Uomini 2011). From this evidence we can infer that the last common ancestor of Neanderthals and Homo sapiens was also right-handed, and that this species—Homo heidelbergensis (see Chapter 4)—also had the capacity for complex language.5

‘The language gene’ Finally, almost in passing, brief mention needs to be made of the extraction of the modern human form of the gene known as FOXP2 from ancient Neanderthal DNA (Krause et al. 2007). A defect in this gene has the effect of impairing an individual’s ability to articulate words (verbal dyspraxia) and understand grammatical rules; in short, to communicate effectively (Fisher and Marcus 2006). That impairment arises from its impact on the networks that support the learning of complex sequences of movements, including connections between Broca’s area and the cerebellum (Ibid: 17). The gene is not unique to humans and is found in many vertebrates, including mice (who have language only in cartoons), but in humans it has a supporting role in language. The modern human form has two mutations that distinguish it from FOXP2 in chimpanzees, and until recently it was thought to be a uniquely human variant. The discovery of the modern form in ancient Neanderthal DNA suggests that it arose in Homo 5 The Sima de los Huesos skulls offer yet more tantalizing support for the capacity for language. They preserve the fossilized bony structures involved in speech production (hyoid) and language perception (outer and middle ear) (Martínez et al. 2004, 2008). Both structures were essentially modern in form.

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heidelbergensis (Krause et al. 2007). If this finding is substantiated by further discoveries then it will add to the growing interdisciplinary evidence for a Middle Pleistocene ancestor who had the capacity for not just language but also complex hierarchical thought. There may also be much earlier mutations in genes that supported the evolution of the human pattern of a left-hemisphere dominance of language areas (Priddle and Crow 2009), and by implication the capacity for making and using complex tools.

AN ANSWER AT LAST, MAYBE So, could Homo heidelbergensis have invented hafting? Well, academics are notorious for avoiding simple answers to direct questions. If a ‘maybe’ can be inserted or even better the woolly phrase ‘the evidence suggests that’, then we’ll opt for the cautious qualified answer every time, except this once. The answer is ‘yes’: Homo heidelbergensis could have invented hafting, but so could any other similarly largebrained and dextrous human ancestor. An invention will have a lasting impact only if it is shared with others and passed to the next generation. These are the essential social foundations of hafting, and we move now to the next critical pillar in this story of the first industrial revolution.

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3 Tools for Learning We now know that our ability to make hierarchically organized tools evolved along with our capacity for language and other similarly complex behaviours. Having the biological ability to make a hafted tool is one thing, but knowing how to make it is another. Can we learn to make a hafted knife from just watching an expert at work, or do we need the properties of the materials explained and instructions given on how to shape and prepare the components into a functioning whole? The components will need to be joined and that may involve the use of adhesives and binders as well as the shaping of the handle for the job. Just from this brief description of the hafting process it is obvious that there is more to the making a hafted tool than meets the eye or than can be understood by observation alone. The process will also involve other tools and require knowledge about how they are made and used. We will look at the mechanics of hafting in detail later (see Chapter 5), but for now our focus is on how humans learn complex tasks and when that capacity evolved. The capacity for learning is something we take for granted; it is something we all did in school and continue to do. Learning from others and sharing that learning lies at the core of our impressive human capacity for cumulative cultural change. Innovation and invention also require a degree of intelligence and by about 500,000 years ago humans had large brains within the modern size range and the potential for complex language (Dunbar 2007). Language plays an obvious role in teaching, but we learn in other more subtle ways that depend on our social surroundings, age, and sex. To reconstruct when the ability to learn to make hafted tools evolved we first need to know how humans learn. We need then to consider the social context in which the inventors of hafting lived. This means looking at contemporary hunter-gatherer societies, which are the most relevant

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From Hand to Handle Cooperation hunting & gathering

alloparenting & altruism

Egalitarianism food sharing

social learning Theory of mind

technology

language

Fig. 3.1 The interplay of social variables that make up the unique cognitive and ethical structure of hunter-gatherer societies. Technology has a linking role in the network of food sharing, alloparenting, and cooperation more generally. (After Whiten and Erdal 2012).

examples of life lived in small communal groups. But we need to go even further than this; we need to look at when and why societies founded on cooperation and food sharing evolved. This sounds simple, but in fact there is a complex interplay of social factors involved, linked with the biological requirements of giving birth to dependent young with rapidly growing brains. The interplay is perhaps best expressed graphically as in Figure 3.1. The first part of the chapter pieces together the social foundations of human learning starting with observations derived from ‘social learning theory’. We then extract the essence of ways of learning which are then linked to the distinctive pattern of human growth and cognitive development. The basic features of hunter-gatherer social life are outlined, and a model is put forward that links the evolution of our large brains with the need for group cooperation. The second part of the chapter looks at the fossil and archaeological evidence in support of a Middle Pleistocene origin of these social foundations of hafting.

SOCIAL LEARNING THEORY Social learning theory takes as a given that we are born into a social world and examines its impact on both the development of the individual and the group. As a body of theory it arose first among

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psychologists who reacted to the Freudian focus on the individual and the behaviourist’s emphasis on learning as an impersonal process of responses to external stimuli (e.g. Skinner 1938). Early proponents of social learning theory recognized that we learn by imitating others (Miller and Dollard 1941), and that approval from others can be a powerful motivation to change our behaviour (Rotter 1954). Albert Bandura (1977) incorporated these ideas and similar ideas from other social theorists (e.g. Vygotsky 1976) into his proposal that individual psychological factors and the social environment together influence how we learn and behave. He outlined what has become an influential model of three prerequisites for social learning: first, we must be able to observe closely how others behave, noting also how their actions are received by others; second, we need the capacity to recall and imitate what we have seen; and third, we need the motivation to adopt a new behaviour in the first place. We are all familiar with the power of peer pressure, and though it remains an influence throughout our lives we are most susceptible to the need to belong to a group when we are young and still developing our social identities. This desire drives us to adopt new behaviours, including the beliefs of those we respect or admire (Bandura and Walters 1963). The enduring success of soap operas, lifestyle magazines, and our consumption of celebrity gossip are hardly surprising in this context—we are intensely curious about the way others behave. We seek social approval and, when given, it acts as a reward that reinforces the learning process. Children are particularly receptive to learning by imitating others, and if socially inappropriate behaviours are learned then they can be modified by changing the kinds and scheduling of rewards, but also by punishment or withholding rewards altogether. These basic principles of social learning theory—simplified here— have had a lasting applied impact on the field of criminology (Akers and Jensen 2003), on the development of educational policies, and on corporate managerial strategies (Ormrod 1999; Elkjaer 2003). From our evolutionary perspective the value of social learning theory lies in placing the individual in a social context in which the variables of age, sex, and group size affect how and what we learn. It also emphasizes the importance of learning by imitation. The ability to imitate, as we know, has deep foundations in the primate brain.

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How we Learn Even though social learning theory emerged from the study of modern urbanized humans, its tenets can be applied between species and across cultures to establish what constitutes a recognizably human pattern of learning. That pattern can then be used as a benchmark for assessing roughly when a modern pattern of learning evolved. Our comparative approach summarizes the similarities and difference between chimp and human learning patterns, and then looks more closely at a couple of case studies of learning in contemporary hunter-gatherer societies. The hunter-gatherer sample is small and certainly not representative of all such societies today or in the distant past, but it reveals important differences in how learning takes place in small social groups when compared with our highly structured system of education. Limitations aside, we can assume that schools and universities did not exist in the Middle Pleistocene, and that the hunter-gatherer sample has greater relevance for imagining the social world in which craft knowledge was passed down the generations. A fine but important distinction can be drawn between emulation and imitation as separate strategies for social learning (Whiten et al. 2004, 2009). Emulation involves copying the outcomes of another’s action without investing time in understanding the steps involved. The interest lies in achieving the end and not in the means. Imitation on the other hand involves copying the actions of another as well as the outcomes and understanding the intention of the actions (Acerbi et al. 2011). Chimpanzees learn largely by emulation in contrast to children who learn primarily by imitation, and this distinction has important implications for the process of cumulative cultural change (Tomasello 1999). Without a well-developed understanding of the processes—including bodily actions—and intentions involved in reaching an outcome, chimpanzees are less able to generate innovations in response to novel challenges or build on existing knowledge (Tennie et al. 2009: 2,407). They often resort to routines and these hardly change regardless of the circumstances (Whiten et al. 2009: 2,426). In contrast, human copying with understanding makes it possible for innovations to be transmitted with relatively few errors to the next generation. They in turn can be improved upon and the innovations passed to the next generation in a process of continual development (Caldwell and Millen 2008). This is how changes

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accumulate with little loss of content, and given an inherent degree of inventiveness we have the makings of gradual and sometimes rapid change (Tomasello 1999). This is the ‘ratchet effect’ which gives human culture its great capacity for innovation and invention (Tomasello 1990). We can caricature chimps as impatient seekers of instant gratification with a limited capacity for learning, but this oversimplification ignores some important overlaps between their cognitive abilities and ours. They do share the capacity to imitate and copy as well as emulate, they do show at times an understanding of cause and effect and do develop socially learned traditions (Whiten et al. 2009). Chimp traditions, or cultures if you prefer, include relatively simple tools and other behaviours that are not genetically inherited (instinctual) nor just responses to environmental differences (Whiten et al. 1999; cf. Laland and Janik 2006). These similarities suggest a deep-seated core of cognitive abilities for learning that extends to our last shared common ancestor 6–7 million years ago, but still there is an enormous gulf that separates our capacities for cumulative cultural change (Levinson 2006). Language obviously plays a critical role in that divergence, but there is evidence too of a uniquely human pattern of childhood learning based on imitation (Galef 1992).

Overimitation Children are not just good at imitating others, they do it to the extent of copying behaviours that have no real functional purpose (McGuigan and Whiten 2009). By the age of two, overimitation becomes increasingly prevalent in Western children, a behaviour that might be attributed to intensive instruction from well-meaning parents (Nielsen 2006). Recent cross-cultural evidence shows similar levels of overimitation among children of former hunter-gatherers in the Kalahari. Two Bushmen communities were studied, and their children were found to learn largely by observation of adults and by some trial-and-error experience. A parallel study of children in suburban Brisbane, Australia, revealed a similar pattern of learning primarily from adults and by individual experimentaion (Nielsen and Tomaselli 2010). The results hint at a possible universal human pattern to learning which has not yet been found in other primates,

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but many more comparative studies are needed to test this theory. What is apparent from these studies is that overimitation occurs not because children lack an understanding of cause and effect, but because they readily accept adults as reliable sources of information worth copying (Csibra and Gergely 2011). This expectation is reinforced by early exposure to learning from parents and other adults who are perceived as trustworthy (Harris and Corriveau 2011). If we do have a unique ability to observe and copy faithfully the actions of others, this suggests that its neural basis lies in the mirror neuron system. To recap, mirror neurons play a central role in learning, especially new behaviours that involve physical movement such as tool making. They are active when we observe what others do and experience, including their emotions (Frith and Frith 2006), but are not active when we try to understand the intentions of others (Spunt et al. 2010: 72). There seems to be a separate network (located along the cortical midline and temporal lobes) activated when attributing purpose to the actions of others and their outcomes. That ability, called ‘theory of mind’, is discussed in more depth below. The supporting neural network may be involved in ensuring that knowledge of how others behave is not just learned but is remembered for later use (Rendell et al. 2011). Perhaps chimps and other primates either lack or have a less well-developed version of this network. In humans it seems to be engaged when an action cannot be understood by observation alone, in other words when the means to an end is unclear.

‘Natural Pedagogy’ in a Kalahari Camp We have all experienced being taught in a classroom by a person designated with the specialized social role of teacher. That kind of formal teacher-pupil arrangement is an alien concept to traditional hunter-gatherer societies because of the high value placed on individual autonomy at the expense of authority—no one individual has the socially recognized role of teacher and the right to tell others what to do (Hewlett et al. 2011). Also rare are apprenticeships that involve a structured arrangement of recognized experts teaching a small group of novices.1 Learning in hunter-gatherer societies happens in a much 1 Apprenticeships are another arrangement that can vary formally depending on the number of instructors and pupils. There might be one master to a group of

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less structured way. Observation and imitation are important as is subtle teaching by demonstration and the occasional correction of mistakes. We can see these processes in action in a small band of huntergatherers living near a waterhole in the northern Kalahari of Botswana. In this group of roughly thirty people, daily life takes place in full view of all in the camp regardless of age (Draper 1976: 200). Children wander freely around the camp and in their early years they rarely stray into the surrounding bush. They play under the watchful eyes of their parents, grandparents, and adults from other families. In such a small group the average child will have few friends of the same age, and so will play and learn from others across a wide age range. Individual learning also takes place in quiet moments of trial and error, but most learning involves two or more individuals. In the open layout of the camp, children also see most adult activities including ways of resolving social and practical problems as well hearing topical conversations. From such experiences the observant child absorbs the collective sense of what constitutes an appropriate behaviour for a particular situation. Casual observation is also the route to picking up survival skills as well as learning social roles. An example is the making of leather, which is a basic item of this group’s material culture. Its preparation involves several stages of planning and action as well as differing roles for men and women. A hide is first staked out and allowed to dry before being scraped clean with an adze. (The stripping of the hide from the carcass and

apprentices or many experienced individuals directing their attentions to younger members of a social group. Those who have been a Scout, Guide, Brownie, or Cub will recognize the format of older individuals guiding a younger generation. In a more appropriate ethnographic case study, some village communities on the island of New Guinea still produce hafted stone adzes and do so through an extended period of apprenticeship (Stout 2002). The apprenticeship as observed in 1999 involved three experienced men teaching three younger male novices, and traditionally the training process began at the age of twelve and would last up to five years, but ten years of experience was needed to make the longest adze heads (Stout 2002: 702). The learning process takes place in this small community with each step in the production from raw material to hafted adze involving communal interaction in the form of observation, demonstration, teaching, and assistance from others to correct mistakes or help with particularly difficult problems. There is more to this arrangement than the teaching and learning of a set of practical skills. The apprenticeship also serves as a forum for socializing the apprentices. They learn self-discipline and cooperation but also about their ancestors and the spirits that inhabit the rocks and how to respect them.

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the shaping of the wooden stakes are earlier steps in the process that also take place in full view of the camp.) The scraping clean is usually a man’s task. Children watching are sometimes rewarded for their patience with a nibble on the edible skin shavings that form during the scraping process (Draper 1976: 212). The softening of the hide is accomplished over many hours of rubbing in a bark powder and this is typically a woman’s job done in the company of other women and often watched by children. The camp is effectively the classroom and all adults are potential teachers. It is the place to observe essential tasks such as preparing, cooking, and sharing food, and the making of tools for gathering and hunting. It is also the place of socialization where the child learns the group’s language, beliefs, traditions, and what is expected of her or him as an adult member of society. The process of learning by observation in the Kalahari may seem too casual a way to impart core knowledge, but what the above characterization left out was the active intervention by adults to correct or change errant behaviours. On average, the behaviour of girls was corrected 1.5 times per hour and boys 2 times per hour (Draper 1976: 210). The correction might be verbal but it was also as likely to be by demonstration. Such directed and purposeful communication forms what psychologists Gergely Csibra and György Gergely (2009) call ‘natural pedagogy’ as distinct from institutionalized teaching. Learning by observation and imitation coupled with corrective intervention appears to be a distinctively human pattern that also incorporates what we would recognize as more formal teaching by deliberate instruction (Csibra and Gergely 2011). Natural pedagogy guides the learner through complex actions or ideas and helps make clear what might otherwise be conceptually opaque operations. If the means to an end are not obvious, then this form of guided learning eases the path to acquiring knowledge. It also improves the likelihood that information will be transmitted faithfully from one generation to the next with far fewer errors than if the learning was by trial and error (Tehrani and Riede 2008). Directed learning is of particular importance in the context of learning how to make hafted tools, especially when the making of the parts themselves involves separate spheres of knowledge (see Chapter 5). Depending on the complexity of the tool, the novice may need a range of expertise in sourcing and preparing different materials even before combining them into a functional whole. An object like an adze or hafted knife is conceptually and physically an

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opaque object. The finished tool represents a sequence of decisions and actions that are not obvious from the final form alone. The joint or haft that links the handle with the blade will be covered in a binding material which makes the shape of the haft invisible and obscures the adhesive inside. A novice might learn how to make a copy of a hafted tool from close observation alone, but chances are it will fail when used. Teaching improves not just the efficiency of learning but also the social efficacy of the process; pupil and teacher are engaged in an interaction with mutually understood roles (Tomasello 1999). The human developmental pattern of an extended period of childhood dependency on others gives added importance to this relationship. Given that children are particularly receptive to learning from trusted adults, this makes childhood a productive time to learn difficult behaviours, technological as well as social (Shennan and Steele 1999). Childhood also binds generations together, and not just immediate blood relations but also other members of a small community who take a share in ensuring the future of the group through the education of its young. We will return to this theme of the cooperative rearing of young shortly, as it is a key feature of hunter-gatherer sociality.

THEORY OF MIND AND LEARNING Learning by teaching is an inherently cooperative act. It involves at least two individuals, one willing to impart knowledge and the other willing to accept it (Cavalli-Sforza and Feldman 1981). A social contract is formed based on these expectations and on trust. The efficacy of that contract relies on the assumption that the other individual experiences the world as you do, and has the capacity to understand your wants, needs, and desires, as you do theirs. Psychologists refer to this heightened level of awareness of others as theory of mind or mentalizing (Baron-Cohen 1995; Frith and Frith 2006). The ability to read the mind of another is the foundation of everyday social interaction; we adapt our own behaviour in response to how well our predictions of others match the reality of their behaviours. We also deliberately use our mental models to manipulate the thoughts and action of others towards our own ends (Whiten and

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Byrne 1988, 1997). Through experience we can learn to gauge the mental states of others from subtle visual clues such as facial expressions and body language. Mirror neurons and the theory of mind neural network both play a role in this process. There may also be a molecular component to our interactions as particular neurotransmitters are released in the brain that enhance feelings of trust, which in turn encourage social bonding and altruism (Domes et al. 2007). The existence of neurobiological components of mind-reading and sociality means these behaviours are subject to natural as well as sexual selection. They are also potentially open to abuse by the more Machiavellian among us who might want to manipulate this knowledge to stimulate feelings of trust artificially (e.g. oxytocin aerosols) (Donaldson and Young 2008). Theory of mind underpins natural pedagogy as it does formal teaching. Pedagogy of both sorts also relies on some form of communication that enables the sharing of generic knowledge about objects, actions, and situations (Csibra and Gergely 2011). Teaching can involve gestures, sounds, or images with its effectiveness depending in part on the medium, but also on the level of shared understanding. Spoken language has the advantage over gestures in that it can convey complex abstractions and to do so where visual communication is limited by darkness or physical obstructions. Images and writing have the added advantage over language of transmitting information without the maker needing to be present, but the viewer and reader need to know the meaning of the images. A hafted tool such as a spear with a stone point is also a potential medium for expression. Its design can communicate much about the skill of the maker as well social status and group affiliation. Just how it will be ‘read’ by a viewer will depend on factors including their age, sex, social group, and the context in which the spear is seen. We often overlook the fact that technology is not just a medium for transmitting messages, but can be the message itself (McLuhan 1964). The Saturn V rocket that propelled Americans to the moon signalled to enemies and allies alike the technological prowess of its makers. How that message was received is another matter, but theory of mind was certainly involved in its decoding.

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MODES OF LEARNING AND GROWING UP Natural pedagogy may not be uniquely human, but it is certainly common in human societies. In our Kalahari case study children had their behaviour corrected by adults, but they were learning from each other as well as from adults. These other sources of knowledge can be classified into a small number of types based on the age, kinship, and the ratio of teachers to pupils. A typology of knowledge transmission helps visualize not just the way learning takes places within and between generations, but also in understanding how it can spread between communities. The ability to spread knowledge widely will be relevant later when we consider the diffusion of the combinatorial principle from its one or more centres of origin. The typology of knowledge transmission is based on analogies made with the inheritance of genes and the study of how epidemics spread between individuals and across population (Cavalli-Sforza and Feldman 1981: 55). The three basic modes of transmission—vertical, horizontal, and oblique—reflect the direction in which information moves. In the sections that follow, these modes will be shown to change in importance as we mature physically and emotionally from infancy to adulthood. This discussion may seem remote from the invention of hafting, but the linkage between modes of learning and growing up is relevant from an evolutionary perspective. If an extended childhood is needed to learn complex behaviours like hafting, then we can use that connection as a clue to detect roughly when the socio-cognitive capacity had evolved to transmit the combinatorial principle across generations. But there is an even more basic connection between the stages of childhood and the modes of learning; it stems from the changing nutritional demands of our growing brains. Those demands are the key to understanding how communities evolved based on cooperation and food sharing.

Vertical Transmission and the Needy Brain Vertical transmission is the parent–child relationship and in many small-scale societies it is the fundamental way of learning in the early years of life from infancy to childhood (Aunger 2000). Depending on the gender division of specialist skills in a band, a female child might

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learn gathering skills from her mother, and a male child, hunting skills from his father. This is a case of uni-parental vertical transmission, and the term also applies to single-parent families. Vertical transmission begins at birth with the close emotional bonds formed between the dependent infant, its mother, father, and other caregivers (Bowlby 1988; Hrdy 1999). The biochemistry of the bonding process is an active area of research with heightened levels of the ‘love hormone’ oxytocin reported in the brains of new mothers (Donaldson and Young 2008). The social and biological mechanisms that support learning as well as bonding appear to have co-evolved. The physiological needs of the newborn contribute to the formation of strong bonds with the mother that strengthens the effectiveness of vertical transmission. An infant’s brain size at birth is less than a third of its eventual adult size, compared with 40 per cent for the average ape infant (DeSilva and Lesnik 2006). Our smaller infant brain reflects an evolutionary trade-off between having a large adult brain with its many advantages in terms of problem-solving capacity, and the anatomical limitations posed by walking upright on two legs. The human birth canal reflects this compromise; if it was any narrower then the child’s head and shoulders would get stuck more regularly than they do now (with serious complications for all involved), and if it was much wider then the efficiency of walking would be affected (Rosenberg and Trevathan 2002). Human brain growth is rapid during the first year of life when the brain reaches 70 per cent of its adult weight (Devlin et al. 1994: 470). There is continued growth into childhood and adolescence, but the real spurt takes place during infancy. That first year also sees an increase in the density of neural cells and their connections in the brain, all of which is metabolically demanding. Brain tissues require about sixteen times more energy to support than the same amount of muscle tissue (Leonard et al. 2007: 312). Not surprisingly, most of a newborn’s energy intake (87 per cent) feeds its growing brain. That figure declines in childhood (44 per cent at age five), but it is still high compared with the adult average (23 per cent for men and 27 per cent for women) (Leonard et al. 2007: Table 4). We may find the sight of a chubby baby naturally endearing, but that extra body fat at birth is also a metabolic insurance policy; it provides a valuable reserve of stored calories that can be tapped in hard times (Ibid: 312). Our fat reserves decline in childhood to near the adult average once the brain

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has completed much of its growth. Those reserves are just that, a standby source of energy.

The Human Pattern of Four Stages of Development The day-to-day needs of infants in non-industrial societies are met through breast milk in the first twelve months and then supplemented by easily chewed and highly nutritious weaning foods (Pearson et al. 2010). This period of breastfeeding provides a natural physical context for vertical transmission from mother to child. In many hunter-gatherer societies weaning is not complete until the age of three, which might seem interminably long by modern standards but is early compared with apes who continue to breastfeed until their adult teeth are in place and they can forage for themselves (Locke and Bogin 2006: 262). Early weaning in humans should in theory allow the mother to replenish her nutritional reserves and to begin having children again (Bogin 2009). Compared with apes we do have a short birth interval, which helps account for the great disparity between the rate of human population growth and that of our evolutionary cousins. After weaning, the human child is unique among primates in the length of its dependency on others for food and slow growth during the next few years (Bogin 2009: 567). That dependency reflects the continuing growth of the brain with its high-energy demands combined with a small digestive tract and a set of ‘milk teeth’ not capable of processing tough adult foods (Bogin and Smith 1996: 705). A fouryear-old still requires a diet of high-quality fats, protein, and energy, but is simply too physically immature to care for itself. The four-yearold also makes a tempting meal for large predators and so needs protection from physical risks as well as feeding. Not until the eruption of its first molar (M1), which on average takes place between 5.5 and 6.5 years of age, can the child really begin to eat an adult diet that includes hard-to-chew foods. The growth of the brain is also nearly complete by the age of seven, which means the child’s energy demands decline and it should in theory have enough smarts to fend for itself, find food, and begin to compete for resources with adults (Bogin and Smith 1996). That greater independence marks the transition from childhood to the juvenile stage, which among hunter-gatherers lasts between the ages of six to ten for girls

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and six to twelve for boys (Bogin and Smith 1996: 706). Juveniles, however, remain small with little growth and their childlike size keeps them from being serious competitors with adults and so reduces the risk of threats from bigger more experienced individuals (Janson and van Schaik 1993). The onset of puberty draws this stage to a close and adolescence begins at age ten for girls and later for boys at age twelve (Bogin and Smith 1996). Adolescence is marked by a rapid growth spurt and the awkwardness of the teenage years as we make the transition to being an adult. This stage lasts until physical and reproductive maturity occurs around the age of nineteen for women and in the early twenties for men (Locke and Bogin 2006: 264). The juvenile and adolescent stages are the prime times for the learning of adult roles, consolidating language skills, and developing sufficient social maturity to function independently as a member of society. They are also the time for learning how to use tools competently as part of the essential tasks of hunting and gathering.

Horizontal and Oblique Transmission The parent-child vertical relationship is the most significant source of learning in the small social world of hunter-gatherer communities, but starting with childhood the individual is exposed to new ideas from playmates. Learning from friends and others of the same age, including siblings, constitutes horizontal transmission. When children play they often imitate others, which of course is essential to learning, but they also create mini-cultures of their own based on agreed sets of rules and roles (Nielsen and Tomaselli 2011). Play involves much pretending including the mimicry of adult roles. Play is also important in developing a theory of mind. The capacity to imagine the thoughts and feelings of others develops among Western urbanized children between the ages of two and four (Baron-Cohen et al. 1993), which is close to the time of weaning for hunter-gatherer children. The correlation in timing may be coincidental, but venturing into the playground equipped with a theory of mind makes for not just more interesting games: it prepares the child for learning rapidly from others. Learning from others of different ages is the essence of oblique transmission. This cohort may involve grandparents or other unrelated adults and they bring to the learning process a broader range of

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experience and perceptions of the world than can be gained from parents and peers. Our formalized system of education is a type of oblique transmission, with the teacher imparting information to a group of younger individuals. Horizontal and oblique modes of transmission are not restricted to childhood for we continue to learn from others as we age and move into new social roles (e.g. parent and grandparent) (Aunger 2000). But children are especially receptive to learning, and this aptitude is vital to hunter-gatherer societies in which all depend on each other for survival. Much of what we know of hunter-gatherer learning comes from long-term research in the Congo basin since the 1980s among Pygmy children, juveniles and adolescents. The sample is certainly not representatives of hunter-gatherers today or in the distant past, but it gives a sense of a pattern of learning over time in this forest environment. Learning by vertical transmission is intensive up to the age of five, after which horizontal and oblique transmission grow in importance to the age of twelve (Hewlett et al. 2011). Natural pedagogy is involved too and from a very early age. Aka infants (six to twelve months) and young children are routinely given miniature tools by their parents, such as axes, digging sticks, basket, and spears, and in some cases full-size knives and machetes (Hewitt and Lamb 2005: 4; Hewlett et al. 2011: 1,174–5) (Fig. 3.2). Giving a child a sharp tool might seem irresponsible to us, but the parents do watch closely and will intervene to correct mistakes and prevent harm. This active intervention is a form of natural pedagogy, and may involve the parent holding the child’s hand to demonstrate the action of a knife and pointing to objects made using the tool. By about the age of ten, Aka boys and girls have acquired almost all of the basic survival and social skills they will use in the years to come and learn little more as adolescents or adults (Hewlett and Cavalli-Sforza 1986: 930). Much of that core learning happens early through contact with their parents. Among the Aka there is also a small but significant proportion of learning that takes place collectively as a distinctive form of group oblique transmission. These are communal events, such as dances and hunting rituals, when everyone is expected to take part and to follow well-established traditions of how to behave. This kind of tradition is slow to change and it plays an important role in fostering a sense of belonging to a larger social entity (Hagen and Bryant 2003). Our reliance on vertical and oblique forms of social learning may

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Fig. 3.2 A twelve-month-old Aka girl learns to use an adult tool—the machete—through play and under the supervision of adults. (Photograph courtesy of Barry Hewlett, who retains all rights.)

explain the durability of human cultures over time (Laland and Hoppitt 2003: 158). By contrast, horizontal learning is effective in spreading innovations quickly, especially in highly unpredictable environments (Laland et al. 1993), but it is an inherently short-lived form of transmission in small groups. Individuals might leave or die, and with them goes their knowledge unless it has been transmitted to the next generation. Population size, density, and rates of interaction between individuals are the critical variables for understanding longterm patterns of cultural change including the loss of knowledge (Henrich 2004). We will return to this important theme.

‘COOPERATIVE BREEDING’ AND THE ROOTS OF A CARING, SHARING SOCIETY So far we have been discussing how individuals learn and how that learning process changes with age. It is time now to shift the focus to a particular relationship, that of a mother and her child. That

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relationship has far-reaching social consequences in the small world of a hunter-gatherer group. From pregnancy onwards the mother will need the help of others to provide food, to assist in the birth, and afterwards to continue offering food, shelter, and protection. We are unique among primates in the extent of maternal support needed and offered especially during childbirth (Hrdy 2009). The shape of the human birth canal means babies are born with the back of the head against the pubic bone and the child’s face looking away from the mother. This arrangement makes it difficult for her to reach down and guide the birth without risking damage to the infant’s spine (Rosenberg and Travathan 1995, 2002). The mother is also not in a position to check whether the baby needs help breathing or is being strangled by the umbilical cord. The presence of a midwife reduces these risks and increases the chances of survival for the child and mother. Cross-cultural studies show that older women are most often the midwives, but afterwards a range of potential helpers are on hand from the male partner, siblings, other kin, older children, and other members of the community (Hawkes et al. 1998; Gettler 2010). The support of these ‘alloparents’ enables humans to raise more offspring than other apes and it increases the likelihood that our children will be sufficiently well protected and nourished to have healthy offspring of their own (Crews 2003). They in turn are more likely to live to a ripe old age and become doting grandparents, as well as serving as a community’s collective memory (Dunbar 2008). There is a clear evolutionary advantage of increasing the survival chances of your offspring in exchange for offering support to other family members in the raising of their offspring. At this point, if the collective responsibility for child-rearing is extended beyond kin then we have the makings of a society based on mutual cooperation. But taking an interest in offspring other than your own or that of near relations seems an odd thing to do, as it takes away time and resources that would otherwise be devoted to promoting the survival of your own bloodline. At some point in the past, self-interest gave way to a form of communal altruism based on an ethos of fairness through cooperation (Boyd and Richerson 2009). The extent of cooperation included collective responsibility for rearing of the young, but also a shared dependency on others for the survival and emotional well-being of the group. The bonds of mutual dependency were reinforced by an ethos of egalitarianism with agreed rules governing the rights and responsibilities of individuals and of the

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group (Barnard 2011: 65). Finally, cooperative breeding led to an increase in interaction between individuals, and this extended sociability increased the effectiveness of social learning and with it the transmission of complex technologies to the young (Pradhan et al. 2012). This might seem a hopelessly idealistic vision of the past, but it describes the social principles that guide most contemporary huntergatherer societies. Such societies are unique among primates in having socially enforced sharing as their organizing principle. The issues of when, why, and how such societies evolved remain much debated (see Weissner 2002; Boehm 2004; Barnard 2008; Gurven and Hill 2009), but it is clear that without theory of mind a group-level ethos of fairness would fail to develop (Whiten and Erdal 2012). Language plays an important role too, facilitating the generation and enforcing of cultural norms as well as organizing the practicalities of sharing and other cooperative behaviours (Pinker 2010). Social learning has its place in transmitting core values and the essential interpersonal skills needed for group living. Figure 3.1 reminds us of the interplay of these and other social variables and how they reinforce each other.

Me Tarzan, you Jane Group-level cooperation expresses itself in two other key areas of behaviour, namely a sexual division of labour and the sharing of meat. We will look at each and how the invention of hafting could have contributed to the development of these social institutions. As a generalization, with many exceptions and permutations, men hunt large animals and women (and sometimes children) gather plant foods, hunt and trap smaller animals, and help in the processing of the large kills (Kuhn and Stiner 2006: 954). These roles are not rigid as individuals move between them depending on the availability of foods, need, preference, and changing physical ability. When a good opportunity arises a male hunter might gather plant foods or a female with young will take part in a communal hunt, or leave the child back at camp with other adults. This is the case among the Agta of the Philippines, where those women who do hunt use the same weapons as men (bows and arrows) and hunt the same range of large and small game. Physical strength and endurance is not an issue, but women

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hunters do adopt a different strategy from their male counterparts. They never hunt alone or range far from camp and they use dogs as hunting aids (Goodman et al. 1985). The local habitat with its abundance of game near to camp makes it possible to hunt and return quickly to look after dependent young. The Agta may be the case that proves the rule that women’s choice not to hunt large game is tied ultimately to the responsibilities of caring for children (Gurven and Hill 2009). There is an important geographical component to this basic division of labour. As we move further away from the equator and growing seasons shorten and plant foods become scarce, then meat accounts for an increasing proportion of the diet. The division of labour becomes more pronounced as a result. Arctic communities, such as the Inuit, can, during the long winter months, rely almost entirely on animal foods in the absence of plants (Hayden 1981). Here, women take part in fishing but not in hunting, which is a man’s role. Women are also involved in vital tasks such as preserving foods and the making and maintenance of tools including the carefully tailored clothing essential for survival (Waugespack 2005). This separation of roles makes practical sense as it allows for the development of areas of expertise that, when shared, contribute to the long-term success of the whole community. It also transforms human society into a uniquely successful entity that operates as a collective superpredator (Whiten and Erdal 2012).

The Benefits and Costs of Food Sharing Less dramatic but equally important from an evolutionary perspective is the adaptive value of food sharing for the rearing of dependent young who require high-quality diets for proper brain growth and development. Pregnant and lactating women require more nutrients and calories than other women, and a diet that contains a diversity of animal and plant foods is the best route to avoiding malnutrition for the mother and child (Hockett 2012). Hunting a range of game (terrestrial and aquatic) and gathering a variety of other foods (plants and insects) normally provides that necessary mix. But to be successful over the long term for the group as a whole, hunting and gathering

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needs to be organized along lines of specialized skills and knowledge (Gurven and Hill 2009: 57). Hunting, more so than gathering, involves higher risks and can takes years to master. The training of males to hunt makes sense, then, if we accept that childcare constraints limit the time a woman can devote to perfecting her skills as a hunter. For the male, being a good provider also offers potential social status in otherwise egalitarian communities, which can be used to attract mates, build alliances, and improve the long-term chances of survival for his family and close kin (biological fitness) (Hawkes and Bliege Bird 2002; Weissner 2002). The mix of the motivations for hunting and sharing will vary with time and place, but arguably without a division of labour this largely male activity would not be possible. The male-female division of labour creates an interdependent and highly effective economic unit. Food sharing as an organizing principle comes with a social cost. Perceptions of unfairness in the distribution of food or laziness as a hunter are persistent sources of tension that need to be resolved in the interests of group unity. In the very public setting of the Kalahari campsite, the accused may be the subject of a range of pressures to change their ways including shaming, ridicule, and ostracism. To be shunned and excluded from participating in the life of the group is a powerful deterrent to misbehaving, especially when everyone depends on everyone else for their survival and happiness. If disputes continue then the aggrieved party might simply move to another camp, but in extreme cases the group might execute the offender (Lee 1979: 392–5).

Tools for the Trade Hafting increases the efficiency of tools generally and provides a template for manufacturing a range of new tools that can enhance the effectiveness of hunting as well as gathering. The innovation of the stone-tipped spear, bow and arrow, spear thrower, and traps all contributed to the effectiveness and reliability of hunting as well as reducing the risks to the hunter. A hafted knife or adze makes the job of disarticulating a large carcass that much quicker and safer than using a hand-held flake. Hafted tools can, of course, be used to make

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gathering more efficient, such as a scythe with inset stone blades for harvesting the tough stalks of wild grains. The use of an adze in preparing leather, as happens in the Kalahari, forms part of the sequence of making a sling—a deceptively simple tool—which enables women to forage while carrying a child. It also provides a place to store gathered foods that are then carried back to the camp (Lancaster 1978). There are other examples of hafted tools used to make tools for foraging and fishing, but the basic point remains that the invention of hafting increased the efficiency of an existing sexual division of labour (Barham 2010). In doing so it consolidated food sharing as an essential part of the social contract of group living, not to mention the longer-term evolutionary advantage of increasing the chances of survival for individuals, their offspring, and the community in which they live.

GROUP SIZE AND RATES OF INNOVATION Brief mention has been made of the fragility of social learning in small groups, and hunter-gatherer societies are inherently small. The average band size is thirty individuals and this holds across landscapes from the Kalahari to the Arctic (Layton and O’Hara 2010). This number includes adults and children, which means that the loss of an experienced hunter or gatherer can have a significant impact on the immediate fortunes of the group. A group of thirty is not sustainable over the longer term, and hunter-gatherer bands typically establish extended social networks that offer allies in times of stress and potential marriage partners. At certain times of the year they may meet to socialize and exchange information before breaking up into the smaller band unit. But even at times of maximum community size they live in social worlds that are many magnitudes smaller than ours. Stephen Shennan (2001), a palaeodemographer, estimates that a group size of about seventy-five individuals brings substantially more opportunities for innovation and social learning than the huntergatherer average of thirty. There are more minds on tap to share and solve problems and a greater range of experience available through horizontal and oblique transmission. Conversely, smaller and relatively isolated communities are more likely to lose knowledge

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over time by a process of cultural drift as a decreasing pool of experts and learners offers fewer chances for innovations to become embedded in daily life. This seems to have happened on some of the more isolated island communities in the Pacific Ocean (Kline and Boyd 2010). But the most dramatic example of the loss of technological knowledge comes from the island of Tasmania off the southeastern tip of Australia. Tasmania was part of the Australian continent until relatively recently, becoming separated by water after the end of the last ice age (glacial cycle) about 10,000 years ago. As the sea level rose, the small and dispersed population of Tasmania became isolated from the flow of ideas and people on the mainland. When Europeans first encountered Tasmanians in the late eighteenth century, they found an island inhabited by small communities of people who had the simplest technology of any known contemporary society. Their technology was basic compared with that of hunter-gatherers on the Australian mainland, and, intriguingly, it was simpler than that of their own ancestors who had been living there before and after it became an island (Henrich 2004). The archaeological record of Tasmania shows that within just a few millennia after isolation they stopped fishing and making the tools needed to fish (spears, hooks, nets), and lost the arts of making hafted tools more generally. Their clothing became simpler despite the cold weather and they either lost or never developed the technology of making seaworthy canoes. (The widespread belief that they also lost the art of making fire has been shown to be an unsubstantiated myth [Gott 2002].) In Shennan’s model, a large pool of people learning from each other means that rates of innovation are not only going to increase but they also stand a good chance of becoming embedded in daily life. The reverse happened in Tasmania. Its small population offered fewer experts to learn from, and over time, as imperfections in the learning process accumulated, the range and complexity of tools gradually declined to a norm based on the types simplest to imitate (Henrich 2004). The level of expertise reached a low plateau, and at the time of European contact Tasmanians had developed an aversion to eating fish and found the European practice disgusting. This case study highlights the fundamental importance of population size, density, and the level of social interaction to rates of change. So, when we look back to the distant past of 400,000 or so years ago we should not be surprised if rates of innovation were painfully slow

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by modern standards. They were, and remained so until populations grew and social networks expanded 8,000 years ago following the rise of settled village life based on farming (Coward 2010; Mithen 2010).

TEETH, BRAINS, AND HORMONES—THE EVOLUTION OF CHILDHOOD AND COOPERATIVE BREEDING We have established that modern humans are unusual among primates in having a long childhood dependency on others, and use this extended interval to learn the complexities of social living. Technology is also very much part of the social world, especially in huntergatherer communities who live directly on the foods they collectively find and share. The progressive stages of childhood, juvenility, and adolescence give us the time to learn the many social and practical skills needed to function as an adult, including the use of language (Locke and Bogin 2006). So when did this distinctive human package evolve with its interlocking stages of biological and social development? The answer will give us a time frame in which to look for not just the invention of combinatorial technology but also its transmission over generations. We can expect then to see in the archaeological record evidence for hafting followed by increasing cumulative cultural learning. Evidence for the evolution of the human pattern of development comes from three indirect sources: teeth, brains, and hormones. We will consider each briefly in our search for any underlying trends.

The Tooth Fairy Revealed You may well remember losing a tooth as a child; the odd sensation of a wiggling tooth followed by a bit of blood and then a gap in the smile to show friends. Perhaps the tooth fairy left a small reward under your pillow as compensation for this little childhood trauma. The replacement of our childhood ‘milk’ or deciduous teeth by adult dentition begins around the age of six with the eruption of the first molar. Molars enable us to chew tough foods like meat, nuts, and roots, and as they and the rest of the adult dentition appear we are increasingly

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able to eat adult foods. In Barry Bogin’s (1999) model of human development, the appearance of the first molar (M1) marks the transition from childhood to the juvenile phase of increasing physical and social independence. Among primates (and other mammals) the growth and eruption of M1 is closely correlated with life-history patterns such as length of gestation and age of sexual maturity (Smith 1989). In those primates that mature early and die young, teeth other than the molars erupt first and the molars follow with all the adult dentition in place before sexual maturity has been reached. The relationship between the two sets of teeth is reversed in more slowly maturing and long-lived primates. The molars erupt before the other teeth, and individuals reach maturity before the full set of adult teeth is in place. The latter is the case for humans (slow to mature) when compared with chimpanzees (quicker to mature) (Conroy and Kuykendall 1995). This morsel of correlated anatomical and developmental trends means the age of the eruption of M1 gives us a key to unlocking when the modern pattern of an extended childhood evolved. Unfortunately, fossils of children and adolescents are extremely rare, but the few we have provide consistent evidence of a gradual evolution of an extended childhood. The application of the relatively new and nondestructive techniques of three-dimensional imaging of the structure of individual fossil teeth is revealing minute details of the growth process as well as providing more reliable measures of the age of eruption (e.g. Smith et al. 2010). Daily growth lines are sometimes visible on tooth enamel and in the dentine. Even more impressive is the identification of a line on M1 that occurs at birth and from this marker the subsequent growth sequence including age at eruption can be measured directly. Not all teeth can be studied in such detail for reasons of preservation, in which cases microcomputed tomography (microCT) provides another, though less accurate, means of estimating age of eruption. The earliest evidence for the evolution of a human pattern of delayed eruption of M1 comes from the Spanish cave site of Sierra de Atapuerca (Gran Dolina). A mandible (lower jaw) of a young individual was found in deposits dated to nearly 1 million years ago (stratigraphic unit TD6). The mandible holds an M1 which is estimated to have erupted between the ages of 6.3 to 6.5 years old based

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on comparison with modern human patterns of crown and root growth (Bermúdez de Castro et al. 2010: 11,741). The other teeth in the mandible are not molars and their early eruption schedule also resembles that of humans rather than chimpanzees.2 The TD6 child seems to have followed the modern pattern of slow growth and the potential for a long life, in other words it had an extended childhood.3 We can stretch the inferential chain to say that some degree of maternal support probably existed in the Atapuerca community as cooperative breeding would have been necessary not just because of long childhood, but also because of the likely small size of the newborn’s brain. The TD6 child lived in a community in which the adult brain size (volume) exceeded 1000 cm3 and the excavators argue that some form of language probably existed—with which they could have discussed childcare arrangements.

Little Brains and Long Dependency The average brain size of the TD6 adults provides another clue to the timing of the evolution of a modern-like childhood. A few years ago biological anthropologists Barry Bogin and Holly Smith (1996: 707) called attention to the research of Robert Martin (1983), who set an adult brain size of 850 cm3 as the evolutionary threshold for the emergence of a human pattern of delayed maturity. More recent supporting evidence comes from the relationship seen among living species of Old World apes and monkeys between the size (mass) of This child probably died just about the time of the eruption of its first molar (Bermúdez de Castro et al. 2010: 11,739), and its early death is a reminder that childhood mortality rates among contemporary hunter-gatherers are high by modern standards, but lower than that of chimpanzees. From an evolutionary perspective, our greater longevity gives humans a long-term reproductive advantage over other apes as our populations have the capacity to grow quickly (Locke and Bogin 2006: 279). 3 Comparative research among the great apes has shown that gestural communication is common between offspring and mother in the early months of life (Schneider et al. 2012). Young chimpanzees, bonobos, and gorillas used touch, visual signals (movement and gazing), and non-vocal sounds (e.g. chest beating, foot stomp) to initiate an activity, usually play. As they became more mobile and independent of their mothers they relied more often on visual signals to maintain contact. Orangutans differ in not using sounds and using their gestures primarily to get food. From an evolutionary perspective, the early importance of visual gestures across the great apes lends some support to a gestural model for the origin of language. The association of gestures with actions, objects, wants, and needs gives a deep-rooted foundation on which to develop more subtle and abstract forms of communication. 2

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the adult brain and the brain size at birth (DeSilva and Lesnik 2008). Those primates with relatively larger adult brains have relatively smaller brains as newborns. This size relationship indicates that most brain growth is taking place after birth and it has important implications for the evolution of cooperative breeding. The correlation between adult and newborn brain size can then be applied to the fossil record to estimate the evolution of brain mass at birth, and even the body weight of newborns (DeSilva 2011). The results show that 1.6 million years ago Martin’s adult brain size threshold had been reached among populations of early Homo erectus, but the rate of postnatal brain growth ranged between that of chimpanzees and modern humans. The amount of extra support needed by the infant and mother also probably fell somewhere between that seen among apes and living humans. The modern human pattern of postnatal brain growth evolved in the Middle Pleistocene sometime after 780,000 years ago and at least by the time of early Homo sapiens (about 160,000 years ago) when there is good dental evidence for the existence of a modern extended childhood (Smith et al. 2007). Neanderthals, however, seem to have evolved a slightly faster rate of childhood development by the Late Pleistocene (from 127,000 years ago) (Smith et al. 2010). Growing up more quickly may have improved the chances of surviving childhood in the harsher habitats of glacial Eurasia. There are hints in the recently sequenced Neanderthal genome that they did have a slightly different pattern of skeletal and neural development when compared with ourselves (Green et al. 2010). The significance of these genetic differences in terms of the sequencing of life-history stages is not yet understood, but they hint at natural selection operating on growth rates among these European populations. For now the earliest indirect evidence for cooperative breeding comes from Europe in the form of the TD6 mandible. If the claims made for this child withstand further scrutiny, then the human pattern of an extended social support network emerged with the Middle Pleistocene. That correlation may be a coincidence or it may reflect the impact of changing climate cycles and increased resource uncertainty that began about this time. We will look at the impact of the onset of longer and more variable glacial cycles in the next chapter, and for now it is worth noting that the TD6 child is a representative of a new species in the fossil record called Homo antecessor (‘Pioneer Man’) (Bermúdez de Castro et al. 1997). It

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evolved from Homo erectus but its ancestral relationship to later European populations (e.g. Homo heidelbergensis or Neanderthals) is still uncertain (see Chapter 4 for a fuller discussion). Stepping back from the detail of eruption records and brain size correlations, we can see the gradual evolution of a recognizable human sequence of development from infant to adult (Fig. 3.3). The human pattern of late maturity begins among early members of the genus Homo roughly 2.3–1.8 million years ago with the development of childhood. The slowed growth of childhood and dependence on older individuals for food is a distinctive feature of humans that is not seen among apes and which probably had not evolved among the australopithecines (Locke and Bogin 2006). Childhood and the following juvenile phase become extended at the expense of a shorter infancy. The growth spurt of adolescence is also peculiar to humans, and this time of rapid sexual development may have also been a critical interval for learning adult social roles before having to compete with adults and take on adult responsibilities (Bogin 1999). This would also have been a time for learning complex technologies and putting hunting and gathering skills into practice. Just when adolescence evolved is still uncertain. It may have existed at the time of the TD6 child at Atapuerca 900,000 years ago or developed later in the Middle Pleistocene among the ancestors of modern humans (Smith et al. 2007).

Implications for Social Evolution We can speculate from the above data that the need for alloparents to support mother and newborn also evolved along with brain size, language, and an extended childhood (Hawkes 2003). There are implications too for the evolution of social learning and social cooperation as more individuals become part of the social network involved in child-rearing. Perhaps there was an increase in longevity with more grandparents available for babysitting as well as being a source of reassurance and advice. We know that grandparents are an important part of the maternal support network among contemporary huntergatherer societies (Hewlett et al. 2000), and this was presumably the case in the past. An increase in male parental involvement in the learning process may also have contributed to the development of a

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Early H He1 He2* MP-H (2.3 Mya) (1.9 Mya) (*TD6 900 ka) (500 ka) Time

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Fig. 3.3 The evolution of human life-history stages showing the estimated time of emergence of the distinctive human pattern of an adolescent phase before reaching physical maturity. The age of eruption of the first molar (M1) and mean adult brain size are used as proxies for reconstructing the sequence. A.a = Australopithecus afarensis; Early H = early Homo; He1 = early Homo erectus; He2 = later Homo erectus and includes Homo antecessor (TD6) as a possible early outlier marking the potential for an adolescent stage 900,000 years ago; MP-H = Middle Pleistocene Homo; and H.s.= early Homo sapiens. The diagram is adapted from Bogin and Smith (1996), Locke and Bogin (2006), and incorporates cranial data from DeSilva and Lesnik (2008) with Atapuerca TD6 added from Bermúdez de Castro et al. (2010). Mya = million years ago.

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sexual division of labour through father to son transmission (Shennan and Steele 1999). The fossil evidence for potential grandparents is sadly elusive. There is little evidence for a dramatic increase in human longevity in the Middle Pleistocene. The problem lies partly with the poor preservation of human remains, especially before burial becomes a widespread practice. There are great regional variations too in the number of individuals represented for the Middle and Late Pleistocene, with far more specimens from Eurasia than from Africa and elsewhere in Asia (Trinkaus 2011). There are also preservation biases based on the robustness of bones. The fragile bones of the young are less likely to be preserved than adult remains, but it is also difficult to be certain of age estimates for individuals older than thirty-five (Miles 2001). This is particularly the case with hunter-gatherer groups in which there are higher mortality rates for the overthirties than in historic farming societies and in modern populations (Chamberlain 2006: 91). One way around this problem is again to use teeth, but rather than calculate a numerical age for individuals the aim is to establish their relative age, that is, whether they might be a young adult (about 15 years old) or an older adult (thirty or older) capable of being a grandparent. This method relies on the well-established observation that the eruption of the third molar (‘wisdom’ tooth) marks the transition to adulthood in the sense that an individual is old enough to have a child. Being sexually mature of course does not necessarily mean the individual is emotionally or socially mature, but that is another issue. Teeth from contemporary groups can then be examined for traces of wear on the assumption that the degree of wear increases with age and those old enough to be grandparents will have considerably more wear than young adults. Biological anthropologists Rachel Caspari and Sang-Hee Lee (2004) applied this comparative approach to a large sample of teeth representing 768 individuals drawn from four different hominin groups spanning the period from 3 million to about 20,000 years ago. Their results do show a slow trend towards increased rates of survivorship of older adults over time. The rate doubles between roughly 3 million and 300,000 years ago with older adults becoming increasingly common members of communities and available as potential grandparents. But the biggest jump in survival rates takes place very late in human evolution, just 20,000 years ago among the

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dental sample drawn from European hunter-gatherers (Homo sapiens) (Caspari and Lee 2004: 10,898). Another smaller study of age at death based on tooth wear also points to a lack of elders (older than forty) in human populations until quite recently (Trinkaus 2011). The rigours of a highly mobile hunter-gatherer way of life may be biasing the record as older infirm individuals were abandoned without burial, but it seems that only when human populations became more settled did we live longer. More comparative data is needed from Africa and Asia, but perhaps the increased longevity seen in the later European record reflects greater food security arising from technological innovations such as the bow and arrow (see Chapter 6), food storage, greater specialization of tasks, plus reliance on extended support networks. The dental evidence for the evolution of an extended childhood has been challenged, but the correlation remains strong between brain size at birth and the human pattern of kin-based care for mother and child. If the over-forties were thin on the ground for much of human evolution, then the opportunity and need to learn from others of different generations was condensed into a short time frame. A twelve-year-old Aka juvenile has learned almost all the skills it needs to function as an adult, and this accelerated socialization may have been the norm until recently.

BIG-GAME HUNTING AND FOOD SHARING Earlier on, the case was made for meat-eating as a focal behaviour in the formation and maintenance of small social groups based on food sharing. Meat as a high-quality resource has been part of the human diet from the first use of stone tools. The earliest claims for meateating in the human record come from the site of Dikika, northern Ethiopia. Two bones with surface traces of butchery in the form of cutmarks have been reported from deposits dated to about 3.4 million years ago, which also preserve the remains of a young individual of the species Australopithecus afarensis (McPherron et al. 2010). If the Dikika australopithecines were using sharp stones as knives, then this evidence long pre-dates the earliest accepted evidence of butchery and stone tool-making which is dated to 2.6 million years ago and also comes from Ethiopia (Semaw et al. 2003). No stone tools have

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been found at Dikika and the marks on the bones could result from unintentional actions such as trampling (Domíngues-Rodrigo et al. 2012). For the time being, there is no unequivocal evidence, for the use of stone tools in meat-eating before 2.6 million years ago remains. The Dikika juvenile remains intriguing, though, because of its estimated large size at birth, which was not far off that of modern human infants (DeSilva 2011). Carrying such a large child, both in pregnancy and after birth, would have placed extra nutritional demands on the mother as well as hampered her ability to feed. The estimated brain mass of the Dikika infant suggests it would have been born relatively helpless and needing considerable maternal support. The roots of alloparenting look to be deep, preceding the evolution of the genus Homo, but the human pattern of an extended childhood evolved much later. Given the importance of meat not just as a source of nutrition but as a food that can be shared, it is not surprising that much academic ink has been spilled over the issue of how to recognize the development of big-game hunting in the archaeological record. Early humans in Africa, Asia, and Europe would have faced competition for carcasses from other carnivores, such as hyenas and the big cats. Some australopithecines and members of early Homo may have been initially opportunistic scavengers, accessing abandoned carcasses after others had had their fill. More organized forms of scavenging as a cooperative activity may have then led to the innovation of active hunting that provided more predictable supplies of choice cuts of meat and foundations of sharing-based societies. This just-so story of increasing control over access to animal fat and protein has been the source of extended debate (see Domínguez-Rodrigo and Barbas and reply by Blumenschine et al. 2007 for a flavour of the debate). Far less controversial is the evidence for the active hunting of large game by Middle Pleistocene hominins in many parts of the Old World along with the controlled use of fire for cooking (e.g. Stiner et al. 2011; Thieme 2003; Villa 2009). Evolutionary anthropologists Rob Foley and Clive Gamble (2009) see a two-stage transition over the period 780,000 to 300,000 years ago culminating in the huntergatherer niche based on group cooperation. The first stage involved the development of the human family unit based on parents and extended kin. The second stage was marked by the emergence of

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hunter-gatherer bands linked into wider social networks. They note that human brain size increased by 30 per cent late in this period, and link its expansion with the co-evolution of group size, language, and theory of mind. The development of more effective hunting tools, in particular spears, provided more meat than before and so fed the demands of an expanding brain and increasing group sizes. Their model fits neatly with much of what has been discussed here, to which we can add a division of labour, and the long-term impact of demographic factors on rates of innovation.

THE ‘FEMINIZATION’ OF HUMAN SOCIETY A relatively new and still-developing source of information about the evolving structure of hominin societies is coming from the study of how exposure to hormones in the womb can affect the long-term development of ‘typical’ sex-based behaviours in males and females. These behaviours include aggression in males and nurturing skills in females (Geary 2002). The relevance of this biologically based psychiatry for us lies in the impact of such hormones on the formation of the kind of cooperative hunter-gatherer societies that promote innovations and their transmission. Hormones do not fossilize but these particular androgens, of which testosterone is the best known, do leave a physical trace on the human skeleton. Look at your right hand and note the length of your index or pointing finger compared to the length of your fourth or ring finger (to anatomists the thumb is also a finger). If the two are roughly the same, or if the index finger is the longer, then chances are you are a female. Males tend to have a shorter index finger. This basic ratio holds true across cultures, as well as among primates, and is determined at conception by exposure to androgen hormones (Manning 2008). The greater the foetal exposure to androgens the shorter will be your index finger and chances are you have inherited a suite of linked masculine behaviours that include heightened levels of aggression, competitiveness, promiscuity, and reduced levels of empathy. These are behaviours typically found in primate societies in which males compete with other males for mates, along with greater differences in body size between males and females.

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Exposure to low levels of androgen is likely to have left you with a longer index finger and made you inherently a more caring and sociable individual who works with others to form and maintain social bonds. These more feminine behaviours are associated with primate societies in which there are lower levels of competition between males and in which males and females form lasting relationships. In human evolution, there has been a gradual reduction in male-male competition, and in its place increasing levels of cooperation and intelligence not to mention the social conditions that favour innovation and learning. Increasing group size may have kick-started the formation of longer-lasting (semi-monogamous) bonds between females and males that served to protect the mother and offspring from other males (Dunbar 2010). Such pair-bonding led to the selection by females of males with more cooperative, empathetic traits, and crosscultural research bears this out. Human males, unlike males in most mammal species, do invest time in looking after their children, though to differing degrees from females (Geary 2002). That level of investment might seem derisory from the perspective of the hardpressed working mother, but it exists and is subject to social selection. Before you turn away in horror at the thought of genetically programmed behaviours established before birth, there is still plenty of room in our understanding of androgens for society to influence how an individual behaves. The construction and learning of gender roles is negotiated socially and not pre-determined genetically. An example from the Kalahari illustrates the point. The society actively discourages competitiveness between individuals and this starts in childhood games. If boys are predisposed to rough-and-tumble play you might expect to see rivalries and pecking orders emerge, but this is not the case. There are simply not enough children of the same age for team sports (Draper 1976: 202–4), and in their place games of skill are encouraged and no one keeps tabs on who is the top performer. This community depends on equality and cooperation for its survival and that ideology overrides the presumed male inheritance for aggression and dominance.

Fossil Fingers We are not held hostage by our hormones, but their impact on determining finger-length ratios does give us another window through

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which to view the evolution of human society. To date only a small number of fossil human hands from single individuals have been analysed from the perspective of Manning’s hypothesis, and the results show the potential of this technique as a measure of social bonding (Nelson et al. 2011). In theory, species with significantly larger males than females reflect higher levels of male-male competition for mates and resources (Foley and Lee 1989) and slower rates of male maturation (Lockwood et al. 2007). Compared with other primates we show relatively little dimorphism, with males only about 15 per cent larger (in mass) than females (Ruff 2002), but human males take a little longer to mature physically, emotionally, and socially. We are still a species with some degree of male-male competition at its social core—the popularity of sport and the prevalence of armed conflict are just two obvious manifestations. Measuring dimorphism in body mass in the living is easy, but much less so when working from fossils. There is the perennial problem of small sample size on which to base evolutionary interpretations, compounded by the uncertainties of identifying the sex and species of a specimen. Large bones do not necessarily equal a male nor small bones a female, and classic markers on the modern human pelvis used to determine sex may not be present in earlier humans (Walker and Ruff 1993). The analysis of larger samples of contemporaneous specimens has improved the accuracy of sex identification (e.g. Reno et al. 2003), and age differences between males can also be estimated using dental wear patterns (e.g. Lockwood et al. 2007). Middle Pleistocene fossils are rare compared with those of earlier humans and so trends in dimorphism are difficult to identify. The largest sample currently available comes from the site of Atapuerca (Sima de los Huesos), Spain, where the remains of at least twenty-eight humans have been recovered. Their attribution to a species and dating is discussed in Chapter 4, but for now the importance of the sample is that when compared with modern humans they show little difference in size between the sexes (Carretero et al. 2012). Later Neanderthals also appear to be similar to us in their degree of sexual dimorphism (Trinkaus 1980; Quinney and Collard 1997). The evidence from fossil finger bones supports the idea of a gradual feminization of human society, but for the time being the results need to be treated cautiously because of very small sample sizes and numbers of taxa (species) sampled (Nelson et al. 2011). In the absence of any Middle Pleistocene samples it is not clear whether there was a

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gradual steady decrease in male competition over time or whether the trend was uneven, and perhaps regionally and temporally variable. Among modern humans there is variation between populations in levels of male-male competition and these are reflected in slight differences in finger-length ratios (Manning 2008). Aggression, risktaking, and dominance-seeking have their adaptive place in certain social contexts such as on fractious frontiers between established communities, or on the sporting field, but maybe not in the world of high finance where they have contributed to our current state of economic insecurity.

THE SOCIAL FOUNDATIONS OF HAFTING This chapter has covered a wide range of ideas and observations made under the banner of social learning theory. What emerges from this collage of information is a mix of the obvious, the less certain, and the admittedly speculative. We learn from others; that is the starting point for understanding the social context in which the idea of combinatorial technology emerged and spread. Imitation and teaching combined with the capacity to innovate give human culture its stability but also its facility to accumulate useful (adaptive) information over the course of generations (Boyd and Richerson 2009: 3,286). By comparison with the pace of genetic evolution, cultural evolution is rapid and gives human populations the ability to respond to local problems—environmental and social—using a range of behavioural options including innovations in technology. Given the survival advantages offered by social learning to a population, we can expect natural selection to operate on the biological foundation of learning, such as the neural networks supporting language and memory as well as the genetic foundations of child growth and development. The social foundations of learning also presumably co-evolved to include ever greater reliance on cooperative breeding, shared teaching of the young, and the development of agreed rules for maintaining social order in a small community. Separating the biological from the cultural roots of learning becomes increasingly difficult as we come to realize that the two are intricately intertwined and subject to natural and sexual selection (Geary 1998). The impact that foetal exposure to androgens has on potential social cohesion is only

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now being considered for its long-term consequences. To this growing awareness of the co-evolutionary mix of the biological with the social we must add the effects of increasing group-size on the mental calculations needed to keep track of ever fluid social situations. Group-size has been highlighted as a driver of increasingly sophisticated means of communication, but increasing group-size also has a significant impact on the modes and pace of social learning. The more individuals there are in a community the more options are available for learning from others and for solving problems. Your peers may have one way of doing things, but grandparents might just bring a different perspective, if you are prepared to listen. The evolved trade-off between the advantages of having a big brain and the anatomical constraints of walking on two legs gave birth to a social system founded on cooperation. An expectant mother’s need for support from others and an extended period of childhood dependency established networks of cooperative kin that would develop into egalitarian, food sharing bands of interdependent families. Sharing as a form of reciprocal altruism only works well when there is trust between partners based on long-term relationships and some means for dealing with those who shirk their responsibilities (Winterhalder 1996). Meat-eating, and in particular the hunting of large game, offered a social focus around which rules of sharing could have come into being and extended to non-kin. The nutritional value of meat would also have benefited the band as a whole, including expectant and breastfeeding mothers with their added metabolic needs. Into this speculative scenario we can insert the invention of hafting. As well as offering more effective weapons, hafting increased the efficiency of the sexual division of labour which in turn cemented the benefits of communal sharing. A knock-on effect for social learning would be the need to teach the making and use of these new tool forms. Complex language based on rules of grammar would be extremely useful in this context and perhaps it is no coincidence that hafting and language both have combinatorial structures (Bickerton 2007; Balari et al. 2011). Finally, we move to another level of speculation to consider when the biological and social foundations of social learning evolved. The brain-size threshold for cooperative breeding was crossed 1 million years ago, and the lower reaches of the modern range were reached about 500,000 years ago (Rightmire 2004). The fossil evidence for the evolution of an extended childhood hints at a possible early

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emergence also roughly 1 million years ago, but the bulk of the dental data points to the Middle Pleistocene as the time in which the human life-history pattern evolved—and with it the potential for many years of social learning before becoming an adult. By 500,000 years ago, if not before, the cognitive and social foundations were in place to support the invention of combinatorial technology and its transmission across generations.

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4 Something New from Something Old The anonymous inventors of hafting—there was probably more than one—were skilled in working stone, bone, wood, and other organic materials. What drove them, and enabled them, to take that knowledge and create something wholly new, the hafted tool? Their personal motivations are lost to us, but by looking at the innovations which preceded the innovation of hafting, by identifying where they happened, the environmental conditions under which they happened, and what cognitive abilities were required, we can make a good guess at how it happened. We know that hafting is a technology based on hierarchical constructions and we can expect that its precursors shared this property. Three innovations are singled out as individual steps in the invention of the combinatorial principle: 1. the making of carefully shaped and thinned hand-axes 2. the production of specialized cutting edges—flakes and blades 3. the controlled use of fire. All three required extended planning and two of three integrated materials other than stone in their execution. These ‘integrative technologies’ as I call them, developed before the invention of hafting and all appeared in the Middle Pleistocene after 900,000 years ago. In this chapter we will look at the archaeological evidence for the precursors of hafting, but first we need to populate Africa, Europe, and Asia with tool-making humans. We also need to consider the environments in which they lived and how they changed. The Middle Pleistocene was a time of radical climate change that altered the distribution of basic food resources and in so doing shaped the process of innovation. In some areas climate change may have been the stimulus driving cumulative change and invention, but in others it may have

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resulted in the loss of expertise and, at its most dramatic, in local extinctions. We can make only educated guesses—admittedly very educated guesses—at the possible links between climate events and human responses at any particular place and time. But as we examine the archaeological evidence and correlate it with the location of finds and what we know about climate change, a clearer pictures emerges of those regions where hafting was most and least likely to have been invented and why.

DIVERSITY AMONG MIDDLE PLEISTOCENE HUMANS At the outset of the Middle Pleistocene, much of the Old World (Africa, Asia, and Europe) was inhabited by descendants of the genus Homo (Fig. 4.1). Between 800,000 and 200,000 years ago, brain size increased by 50 per cent (Potts 2011) with much of that increase (30 per cent) having taken place by 500,000 years ago (Foley and Gamble 2009). These rapid advances in cognitive capacity corresponded with a radical restructuring of the earth’s climate cycles, which became much longer and colder than before. The long-term result was the creation of increasingly variable and unpredictable habitats to which human populations adapted both biologically and culturally (Navarette et al. 2011). Many of these adaptations have been mentioned already, including increases in brain size and the corresponding development of extended social support in the raising of children. We can also infer the development of hunter-gathererlike practices of food sharing and a sexual division of labour, and an increased potential for innovation through social learning, aided by language in some form. By 500,000 years ago, therefore, the cognitive and social foundations were in place for the invention of hafting in more than one part of the Old World, and, potentially, by more than one species of human. The identification of fossil species depends on the analyst’s understanding of what constitutes a species, and on the significance attributed to variation in preserved anatomical traits (Rightmire 2009). A philosophical gradient underlies the construction of evolutionary

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Fig. 4.1 An evolutionary tree showing the geographical and chronological distribution of human species. This particular phylogeny places Homo heidelbergensis as a descendant of Homo erectus and ancestor of Neanderthals, Denisovans, and Homo sapiens. Homo floresiensis, Homo erectus, and Homo antecessor are extinct branches in this evolutionary sequence. (Permission to use this image was kindly granted by Professor Chris Stringer who retains all rights.)

trees of ancestor-descendant relationships (phylogeny). At one end of the spectrum is the view that Middle Pleistocene humans were are all in fact regional variants of a gradually evolving single species, Homo sapiens, which originated in Africa and subsequently spread across much of the Old World (Curnoe and Thorne 2003). This view is a variant of the well-known biological species concept in which a population that interbreeds and produces viable offspring can evolve into a separate species given time and isolation from other populations (Mayr 1966). Members of a species share a common ancestor and from this perspective Neanderthals are a Eurasian branch of H. sapiens and not a separate species, H. neanderthalensis, but a subspecies, H. sapiens neandertalensis (Henneberg and Saniotis 2011). (Note the subtle change in spelling with the dropping of the ‘h’ to mark this particular perspective.) The recent discovery of genetic evidence for very limited interbreeding (admixture) between Neanderthals and early H. sapiens (Green et al. 2010) lends some credence to the view that these populations were part of a single but regionally

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variable species. Evidence of interbreeding does not necessarily undermine the biological species concept as we know that species boundaries are often fluid among living primates, such as baboons, with interbreeding occurring between neighbouring populations (Jolly 2001). An alternative and more widely held perspective is that Neanderthals and anatomically modern humans (AMH) were closely related and only recently separated species. There are sufficient anatomical and genetic differences to justify dividing them into separate evolutionary lineages that shared a root ancestor in the Middle Pleistocene (Rightmire 2009). Who that ancestor was and where it originated is a matter of considerable debate. It is fuelled in part by the scarcity of fossils from Africa and Asia compared with their relative abundance in Europe. The cave site of Sima de los Huesos, Atapuerca (Spain), provides the single largest sample of Middle Pleistocene fossils known (Fig. 4.2). The skeletal remains of twenty-eight individuals are preserved—possibly as a result of deliberate burial, though this is disputed—and attributed to early Neanderthals or to H. heidelbergensis (Hublin 2009). The age of the skeletons is also currently disputed: they may be 550,000 years old (Bischoff et al. 2003, 2007) or younger than 400,000 years ago based on genetic and morphological features (Stringer 2012). The eventual outcome of this debate will have an important impact on how the scientific community views the status of H. heidelbergensis as a possible ancestor of Neanderthals and H. sapiens as well as perhaps another and very newly recognized population in east Asia called the ‘Denisovans’. We will return to the Denisovans shortly, but there is still more of relevance to uncover at Atapuerca. Ongoing excavations at the nearby caves of Gran Dolina and Sima del Elefante are revealing a considerably earlier human presence in the region. At Gran Dolina fossils have been found in one particular layer, TD6, that date to the very start of the Middle Pleistocene between 960,000 and 800,000 years ago (Bermúdez de Castro et al. 2010).1 We have already looked at this 1 There is an even earlier human from a third cave site at Atapuerca known as Sima del Elefante (Elephant cave). A lower jaw from this site, in deposits dated to 1.2 million years ago, is currently the oldest specimen from western Europe. It shares some inherited traits with African Homo and early Homo found in Georgia (Dmanisi), but also shows distinctive evolved traits (derived) that distinguish it from these other populations and so mark the start of a European lineage (Martinón-Torres and Bermúdez de Castro, in preparation).

Fig. 4.2 Location map of sites discussed in this chapter: (1) Atapuerca sites (Sima de los Huesos, Gran Dolina, and Sima del Elefante), Spain; (2) Ceprano, Italy; (3) Broken Hill (Kabwe), Zambia; (4) Kalambo Falls, Zambia; (5) Victoria West and Fauresmith sites general location, South Africa; (6) Peninj, Tanzania; (7) Olorgesailie, Kenya; (8) Kapthurin Formation, Kenya; (9) Koobi Fora, Kenya; (10) Qesem Cave, Israel; (11) Gesher Benot Ya’aqov, Israel; (12) Boxgrove, England; (13) Cagny La Garenne, France; (14) Orgnac 3, France; (15) Narmada Valley, India; (16) Chikri, India; (17) Dingcun locality, China; (18) Bose basin, China; (19) Luonan basin, China; (20) Denisova Cave, Russia; (21) Ngebung 2, Java; (22) Mata Menge, Flores; (23) Liang Bua, Flores; (24) East Timor; (25) Korean Peninsula marking area of hand-axe sites.

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site for its dental evidence for the early evolution of an extended childhood. The definition of the species Homo antecessor is based on fossils from Gran Dolina, and the research team that defined this species has argued that it was descended from African H. erectus and was effectively the baseline population from which later European species evolved (i.e. H. heidelbergensis and then H. neanderthalensis) (Bermúdez de Castro et al. 1997). (A fossil skull cap of similar age from Ceprano, Italy, has been given the species name H. cepranensis and is also thought to be a descendant of H. erectus [Mallegni et al. 2003].) Further discoveries at TD6 have led to a revision of the European ancestry of species (phylogeny) for the Middle Pleistocene (Carbonnell et al. 2003). H. antecessor is now positioned as the root population of Neanderthals and H. sapiens, but distinct from both (Martinón-Torres and Bermúdez de Castro, in preparation). If the earlier date of about 550,000 years ago for the Sima specimens is correct, then Neanderthals and H. heidelbergensis coexisted and the former did not evolve from the latter. If the younger date of about 400,000 years ago is correct, then H. heidelbergensis remains a viable ancestor of Neanderthals in Eurasia and modern humans in Africa. This is the long-held view of evolutionary anthropologists Philip Rightmire and Chris Stringer. Both see this species as regionally variable, but with enough shared features to argue for an African origin from H. erectus (Rightmire 2008). The evolution of H. heidelbergensis marks a speciation event in the Middle Pleistocene recognized by an increase in relative brain size that exceeds H. erectus and which falls within the lower range of modern humans, plus the appearance of new cranial features found in more recent species of Homo (Rightmire 2001, 2004). In this model, H. heidelbergensis expanded 600,000 years ago into Europe and eastwards into Asia and in the more northerly climes it evolved into what we recognize as Neanderthals. Natural selection for cold-adapted features is seen in some aspects of the Neanderthal skeleton and adds support to the idea of a separate evolutionary history (Stewart and Stringer 2012). In Africa, H. heidelbergensis evolved into H. sapiens after 200,000 years ago and retained a more tropical body form. An alternative is to see H. heidelbergensis as a European species that evolved gradually into Neanderthals, but not H. sapiens (Hublin 2009). The African specimens would be reallocated to a separate species which by the convention of biological nomenclature would

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be Homo rhodesiensis, named after fossils found in 1921 at Broken Hill, Northern Rhodesia (now Kabwe in Zambia). There are other interpretations of the European and African records that incorporate elements of these models with more or fewer species (e.g. McBrearty and Brooks 2000; Brauer 2008): the dedicated reader might want to play the game of putting them into either a ‘lumpers’ (few species) or ‘splitters’ (many species) camp. This game has recently become considerably more complicated with the identification of new Asian species from fossil and genetic evidence.

An Increasingly Crowded Asian Record Chinese scholars have long made the case that H. erectus in east Asia evolved into H. sapiens (Wu and Poirier 1995), and more recently some have accepted the case for an African origin of H. sapiens and find evidence for interbreeding between the two populations before 100,000 years ago (Liu et al. 2010). That interpretation is controversial among most Western scholars who see a later date of after 60,000 years ago for the entry of modern humans into south Asia (Dennell 2010). They have also challenged the view of a single slowly evolving species in China, and interpreted the few Middle Pleistocene specimens not attributed to H. erectus as representing the easternmost spread of H. heidelbergensis sometime after 600,000 years ago (Rightmire 2001). The lone Middle Pleistocene fossil known from India (Narmada Valley) has been classified as H. heidelbergensis in support of the proposed eastward migration, but it also has its strong proponents as a specimen of H. erectus (Athreya 2007). There may even be an eastward incursion of Neanderthals based on anatomical features in one Chinese specimen (Pope 1992). More recently, Stringer (2012) has suggested that some of the younger Asian representatives of H. heidelbergensis are in fact specimens of a separate species (the Denisovans) who are more closely related to Neanderthals, but descended from earlier populations of H. heidelbergensis in the region. The non-specialist may be perplexed by the lack of agreement among researchers about which species lived where and when, and who was the ancestor of this or that species, or not. The debates appear arcane, but they reflect a healthy scientific process in which hypothesis testing is the norm, and emerging certainties are challenged by new methods or discoveries. Two discoveries in particular have challenged the existing phylogenies of the Middle Pleistocene.

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The first, from the Indonesian island of Flores, is the recovery of the bones of a new species, Homo floresiensis, which is distinguished by its short stature, ape-sized brain, and other features interpreted as evidence of an early Homo ancestry (e.g. H. habilis or H. erectus) (Brown et al. 2004; Falk et al. 2007; Gordon et al. 2008). H. floresiensis has generated fierce debate about its validity—maybe the type specimen was a dwarf or a pathological individual of H. sapiens and so not a separate species (e.g. Vanucci et al. 2011). If this is the case, then its proponents have made an embarrassing taxonomic blunder that will become a footnote in the history of evolutionary anthropology. Subsequent analyses of various distinctive components of its skeleton from head to toe (Jungers et al. 2009) have satisfied many doubters that this is indeed a new species of human, but the debate is not over. Of particular interest from our technological perspective, is the evidence that H. floresiensis may have used fire, definitely made stone tools, and probably hunted a local form of dwarf elephant (genus Stegodon), among other animals (Morwood et al. 2004).2 Assuming that they, rather than H. sapiens, left this evidence, then we have to reconsider just what cognitive abilities are needed to make integrative technologies, in this case fire, and we will return to this issue later. The real surprise, if not shock, in this story is the recent date of H. floresiensis; it may have existed just 17,000 years ago (Brown et al. 2004). H. sapiens had already entered southeast Asia about 40,000 years ago and so overlapped in time with H. floresiensis, but apparently not in space. There is no evidence for modern humans on Flores until after 10,000 years ago (Moore et al. 2009), though they probably passed through the area given their presence on East Timor 42,000 years ago (O’Connor 2007). H. erectus may also have been a neighbour, perhaps surviving in parts of the region, such as central Java, possibly as recently as 27,000 years ago (Swisher et al. 1996), though the dates are not secure (Yokoyama et al. 2008) and the ability of this species to live in forested environments has also been challenged (Storm 2001). 2 Island dwarfing evolves among animals living in areas with restricted resources, typically islands, with a smaller body size being a less energy-demanding adaptation. Well-known examples are the small extinct (pony-sized) adult elephants on the Mediterranean islands of Sicily and Malta and the dwarf hippos of Madagascar. The tiny brain of H. floresiensis relative to its body size has been argued as evidence of a pathological condition, but there is evidence from other species that brain size can decrease greatly under the selection pressures of island life (Weston and Lister 2009).

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The Denisovans Whatever was the local fate of H. erectus, the existence of H. floresiensis reminds us that until recently as a species we shared the planet with other humans and our current status as the sole representatives of Homo is an historical oddity. The more recent discovery of the Denisovans adds to an increasingly intricate picture of multiple coexisting human species in Asia. We know of the Denisovans by one bone from the little finger of a young girl and a single molar from a juvenile recovered from Denisova Cave in the Altai Mountains of southern Siberia. They were recovered from sediments dated between 50,000 and 30,000 years ago (Reich et al. 2010). This does not sound like a promising start to a major upheaval in the human record, but the finger bone is the key to unlocking the evolutionary history of this population. It preserves an unusually large amount of ancient DNA (mitochondrial and nuclear) from which the ancestry of the population can be reconstructed (see Barham and Mitchell 2008: 206–10). In the past few years ancient DNA has also been extracted from a number of Neanderthal fossils and a draft of the Neanderthal genome has been pieced together (Green et al. 2010). It reveals that Neanderthals and H. sapiens did interbreed, with between 1–4 per cent of the nuclear DNA of living Eurasians containing Neanderthal DNA. Neanderthal DNA is not found in African populations and that absence suggests the intermingling of these two populations took place after anatomically modern humans dispersed from Africa into the Near East. This may have happened 100,000 years ago or later around 60,000 years ago. A comparison of Neanderthal and Denisovan DNA shows that they are distantly related and diverged from a common ancestor about 600,000 years ago and from present-day Africans about 800,000 years ago (Reich et al. 2010: 1,055). The Denisovan input into present-day Eurasians is very low, almost undetectable, which suggests this Siberian population had a separate history after splitting from Neanderthals. A comparison of the molar with those of Neanderthals from Sima de los Huesos and teeth of Chinese H. erectus adds further support to the interpretation of the Denisovans as a distinct human population, if not species, with a Middle Pleistocene origin (Ibid: 1,059). Chris Stringer suggests they may be a third offshoot of H. heidelbergensis along with Neanderthals and H. sapiens (Stringer 2011, 2012) (see Fig. 4.1). In this view, some Chinese specimens and the lone Indian fossil attributed to

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H. heidelbergensis might in fact be Denisovans, but not all agree with this view of an ultimately African origin (Martinón-Torres et al. 2011).

The ‘Red Deer Cave’ People The Asian record of species and ancestral relationships has become even more complex following the analysis of four human fossils from two caves in southwestern China. The specimens are recent in age (about 14,000 and 11,500 years ago), show an unusual mix of early (archaic) and more modern anatomical features, but are unrelated to living Chinese populations (Curnoe et al. 2012). They may represent a new human lineage, or an unknown population that originated in Africa and which left no genetic traces, or possibly the result of interbreeding between anatomically modern humans and the Denisovans. No ancient DNA has been found in the bones to help clarify their ancestry, but we can say that these newly described ‘Red Deer Cave’ people—they ate a lot of this animal—highlight just how little we know about the population dynamics of the region, which were certainly more complex than imagined just a few years ago.

More than One Species in the Running Even if you are uneasy with the idea of defining a new population from a single finger bone, the growing fossil and genetic evidence points to the Middle Pleistocene as a time of increased regional diversity of species, or, more conservatively, of locally adapted populations or sub-species (‘paleo-demes’, Howell 1999). Setting aside the various interpretations of the fossil record, there is some consensus that the genus Homo was undergoing change early in the Middle Pleistocene including an increase in brain size that separates Middle Pleistocene populations from earlier H. erectus (Carbonell et al. 2005; Rightmire 2004, 2008; Stringer 2011). Given our interest in the invention of hafting, what can we extract from the fossil record that is relevant for understanding the process of technological change? These various species, with the exception H. floresiensis, had relatively large brains to an extent that required some degree of maternal support through cooperative breeding. By inference, these species also had some level of cultural intelligence (social learning and capacity to innovate), theory of mind, and had evolved the capacity for language and perhaps even complex rule-governed language. We

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can also speculate that they lived in small social groups that engaged in food sharing, supported by hunting and gathering with extended social networks. In some settings they may have also followed seasonal patterns of group fission and fusion that increased rates of interaction and the flow of information. This is the generalized cognitive and social context in which integrative technologies were learned, modified, and in which combinatorial technology was later invented.

RESPONDING TO SCARCITY AND UNCERTAINTY Having a big brain may be necessary for inventing complex tools, but capacity alone will not generate such technologies. We need to shift our attention to the necessities that drive innovation on an evolutionary scale, and the most obvious from the perspective of huntergatherer societies is food. These societies make a living directly from the habitats in which they live, and predictability of food resources is critical for survival. There is a range of options for coping with short and longer-term fluctuations in food, water, and other basic resources (Kelly 1995). A group can move camp to a new and hopefully better-stocked area, or tap into extended social networks and share the resources of distant kin and friends. If mobility is not feasible because of geographical or social barriers, then other options might be exercised or emphasized. A group can change its diet by eating foods that might not be the first choice in times of plenty, but which are available when needed and the technology exists to exploit them. There is also the option of preserving and storing foods that might be relatively abundant in the hope they will last through a period of scarcity. Reliance on food storage has its potential drawbacks as it reduces mobility and can create conflicts over ownership and distribution. New social rules for sharing may need to be negotiated as a consequence. In cases of sustained hardship, we might expect appeals for supernatural intervention to bring relief. Finally, though not by any means the last option we have is technological innovation. New or improved hunting, fishing, gathering, and foodprocessing tools might solve immediate and longer-term subsistence needs. In the long term they will have to be passed from one

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generation to the next if the innovation is to become an established part of the technological repertoire. A case study from the mountains of northern California illustrates how a community of hunter-gatherers used their knowledge of the landscape and its resources to cope with rapid climate change. The onset of the ‘Little Ice Age’ (ad 1350–1850) with its colder temperatures than today saw the expansion of ice sheets globally, and in the mountains of California the snowline moved down slope and the growing season was reduced (Morgan 2009). The grasslands and oak forests that once provided reliable sources of food (deer and acorns) were now squeezed into small patches by the expansion of resourcepoor evergreen forests. The shorter growing season also meant the nut harvest became more unpredictable. A scarcity of food and longer colder winters were serious threats to the survival of these mountain peoples. They responded by changing where and how they lived and with a shift in diet and technology. In the winter months they lived below the snow line, but now in large semi-permanent villages which was something new. The villages were located to maximize the remaining patches of forest and grassland from which they could collect and process enough food to see them through the long winter months. With more people in one place the gathering and storing of food was done quickly. In the spring and summer they dispersed into small temporary camps higher up the mountain slopes where they hunted deer and gathered nuts, berries, and seeds for immediate consumption. By being flexible in their settlement strategy they reduced the risk and uncertainty of the rapidly changing environment and managed to survive the Little Ice Age (though not the arrival of European settlers, but that is another story). Stories told of past experiences of harsh winters and short summers may have helped in devising a long-term and effective strategy to ensure that basic needs were met in a changing world.

Technological Buffers and the Value of Tradition We take for granted that there will be strawberries in winter and bananas year round. Global markets and technologies of food storage and transport help smooth out seasonal variations in supply. If there are prolonged regional shortages of particular foods, such as a reduced wheat or coffee crop, we face increased costs and can choose to pay more, buy less, or stop eating wheat and drinking coffee

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altogether. A coffee-free existence might seem too drastic to contemplate, but for hunter-gatherers the costs of food shortages are much more immediate and life-threatening in the form of hunger, malnutrition, and dehydration. The local extinction of whole families and bands was an everpresent risk in especially harsh or unpredictable environments. In the Arctic, extended blizzards can isolate communities and lead to starvation as stored reserves are exhausted. Extremes of temperature, cold or hot, will soon overwhelm the body’s regulatory system and lead to death from exposure. In the tropics there is another important risk to health and that is drought. We can live without food for a few weeks as studies of prisoners on hunger strikes have shown (Peel 1997), but we die within days without water (Gleick 1996). Prolonged drought is an ever-present risk in semi-arid regions, and especially in tropical areas dependent on seasonal monsoons to recharge rivers and revive dry landscapes. These generalizations apply today as they surely did to humans in the Middle Pleistocene. Death by starvation or dehydration is a particularly blunt force of natural selection that few of us can appreciate from the comfort of our homes. The fact that as a species we have not only survived but thrived reveals another more subtle side of selection pressures. They have driven the evolution of our capacity to learn, plan, and innovate. That capacity operates in response to immediate stresses at the day-to-day level as well as on the longerterm scale of seasons and even years. We know from contemporary hunter-gatherers that children learn basic survival skills from an early age through observation, imitation, and from instruction (Hewlett and Cavalli-Sforza 1986; MacDonald 2007). As discussed in the last chapter, children generally have an evolved psychological predisposition to trust and learn from adults that in some situations leads to over-imitation of the actions of their role models. The long-term survival of social groups does not involve just the young of course, but includes the experience of elders who have lived through difficult times and can advise the group on effective responses to a crisis. The fossil record provides some evidence for increasing longevity over the past 3 million years (Caspari and Lee 2004), and just occasionally the skeletal remains are found of older and infirm individuals who would have required some care from others in order to survive. These individuals could not contribute directly to the daily rigours of hunting or gathering and so

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presumably offered other benefits to the community. They may have been able to help with childcare, but more important in the context of small non-literate communities they may also have been valuable repositories of experience who offered emotional reassurance and practical advice in uncertain times. They may hold memories of past threats to the group caused by extremes of weather, other communities, and from internal conflicts. Elders can also be critical sources of information about tools and ways of hunting and gathering. A poignant example of their importance comes from the Polar Inuit of northwest Greenland. European explorers in the mid-nineteenth century found this isolated group struggling to survive because they lacked basic tools needed to hunt, fish, and to build heatretaining houses (Boyd et al. 2011: 8,996). An epidemic had selectively killed many of the elders and the surviving community lost more than just family members; with them lay buried centuries of accumulated knowledge of how to live in this harsh environment.

Learning Strategies and Environmental Change The fate of the Polar Inuit, and that of communities on Tasmania, underlines the importance of cultural learning as the primary means by which humans adapt to change. Having a large brain is important in terms of problem solving as is having the faculty to share complex ideas through language (Pinker 2010), but learning from others gives us our great adaptive flexibility as a species (Boyd et al. 2011). Imagine being a lone explorer entering a landscape of unfamiliar plants, animals, and seasons. Chances are you will struggle to survive, but your odds of survival would improve rapidly if you sought help from those with local knowledge and learned from them. Intelligence and language support the learning process, and though we do learn by individual trial and error, the learning process is much quicker and richer when it involves building on the experience of others. In the context of adapting to ecological change, it is the rapidity and extent of the change that affects which learning strategies are most adaptive. If change is imperceptible, then the smart strategy is to follow tried and tested ways of doing things rather than try to innovate individually (Sibly 1999). Learning from more experienced individuals is practical and saves time and energy; why reinvent the hand-axe when the existing version works perfectly? Such social

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conformity will create an archaeological record that appears static to us with little evidence of change. What change in technology there is will be in the natural variability that occurs between individuals in learning ability and in physical skills. This subtle process is known as ‘accumulated copying error’ by those who model rates of change (e.g. Hamilton and Buchanan 2009). Low copying error might also reflect strong peer pressure as well as the principle of least effort. Among the Aka of the Congo basin, for example, a high degree of conformity is expected by participants in communal rituals (Cavalli-Sforza and Hewlett 1983). Taking part in group activities such as rituals and larger gatherings involving other social groups can help stabilize traditions and at the same time introduce new ideas to a wider network. Hafting as a new technology might have spread this way from one small band into a larger community through the cycle of annual gatherings. If, on the other hand, the local environment is fluctuating so rapidly that the rate of change exceeds the cumulative experience of the group, then individual learning by trial and error might be a more effective strategy for meeting immediate needs (Sibly 1999). Most non-human species adapt to frequent changes in their surroundings through individual learning (Richerson and Boyd 2005: 230), but humans depend on each other physically and emotionally from birth. That dependency increases the likelihood that individual discoveries will be shared through the various modes of learning that exist in a community. At the population level, the adoption of innovations, whether by the movement of peoples or the sharing of ideas between neighbouring communities, offers another potential for coping with unexpected pressures. We will discuss the large-scale movement of ideas in relation to integrative technologies, and later hafting, but first we need to consider the generic environmental challenges posed by Middle Pleistocene climates.

THE MIDDLE PLEISTOCENE TRANSITION The onset of the Middle Pleistocene marks a dramatic shift in the duration and intensity of global climate cycles that began roughly 900,000 years ago. On this long timescale we quickly lose sight of elders and others in a local group who faced challenges to their

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survival. Our focus shifts instead to the generalized impact of decisions made by individuals and communities over the course of hundreds of generations. Socially mediated perceptions of needs and wants become invisible, and we are left with that old chestnut of necessity being the mother of invention. In Darwinian terms necessity equates with survival and reproduction, and that is the general evolutionary context in which to view the invention of hafting. The specifics of the time, place, and process of invention are much more elusive. Very few archaeological sites offer the tight chronological controls and environmental details needed to reconstruct specific pressures operating on a human scale of seasons, years, or a single generation. We are lucky if we can constrain the record to an interval on the order of a thousand years or less. At this point you might well ask why spend so much time reviewing the cognitive and social foundations of hafting when these are effectively invisible in the archaeological record? The answer lies in the artefacts themselves; they take us directly to the maker of the object from which we can make inferences about planning, memory, expertise, and social learning. Experimental archaeology also provides information on how tools were constructed and used. The analysis of individual tools feeds into our understanding of a particular technology as a body of knowledge. Correlations can then be drawn between changes in technology in general and new stresses on resources that affect the likelihood of survival and which may be linked ultimately to climate change. The external stresses will of course precede any technological responses. This simple, if not simplistic, formulation should enable us to construct models for the invention of hafting that can one day be tested. We are still a long way from achieving that goal (see Chapter 5), but for now we can get a sense of the stresses that faced Middle Pleistocene communities.

The Transition Revealed The Middle Pleistocene, as its name implies, is part of something larger—the Pleistocene geological epoch. Think ‘Ice Age’ and that is the Pleistocene in a misleading nutshell. Banish now the popular image of a single period of endless ice and snow with fur-clad early humans trudging after woolly mammoths. The Pleistocene as an epoch encompassed 103 stages of alternating cold and warm that began about 2.6 million years ago and ended just 11,700 years ago

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(Gibbard et al. 2010; Walker et al. 2009).3 The sequence has been developed over decades from careful comparison of long climate records extracted from marine sediments and the coring of polar ice sheets. The numbering of stages follows a convention starting with the prefix MIS (Marine Isotope Stage, see Appendix 2), then odd numbers for warm stages and even numbers for cold stages. The high resolution of these climate records enables us to identify global fluctuations within the general trends of each stage and these are recognized as sub-stages and numbered or labelled alphabetically. The Pleistocene is conventionally separated into three periods— Early, Middle, and Late (or Lower, Middle, and Upper)—based on significant changes in the duration of cold and warm stages and in extremes of temperature. A full glacial–interglacial cycle encompasses a gradual and step-like cooling from an interglacial high to a glacial period low followed by rapid warming leading to the start of the next interglacial. Appendix 2 outlines in detail the evidence for climatechange cycles and in particular the features of the Middle Pleistocene Transition. In brief, long-term variations in the earth’s orbit have changed the amount of sunlight received in each season and especially at the North Pole. Interglacials occur at times of maximum solar radiation in the northern hemisphere summer. Glacials start when the orbital cycle brings low summer temperatures, with the result that ice sheets expand. The overlapping orbital cycles are not the only drivers of climate change; the warming or cooling of oceans and continental landmasses affect the distribution of heat and rainfall across the globe. The Transition began slowly; between 1.2 million and 500,000 years ago the length of glacial–interglacial cycles more than doubled 3 Geologists have recently extended the timescale of the geological epoch known as the Pleistocene (Gibbard et al. 2009). Before 2009 its accepted start date was 1.8 million years ago, a point in time that could be readily identified in terrestrial as well as marine sediments that contain iron minerals. The minerals record the Earth’s long history of periodic switches of the direction of the magnetic poles from north to south and vice versa. We live in a period of ‘normal’ polarity, normal in the sense that it is the one we know. Our current normal phase began 780,000 years ago and was preceded by an extended period of reversed polarity that began 2.5 million years ago. Shorter-lived switches of polarity punctuate these long periods of magnetic stability and provide convenient markers for correlating sediments across continents and ocean basins. The start of the Pleistocene was until recently correlated with the ‘Olduvai event’, a relatively short normal period that started 1.8 million years ago. The revised start of the Pleistocene at 2.58 million years has its associated palaeomagnetic transition (a switch from normal to reversed polarity), and it marks what has come to be recognized as the beginning of a series of global glacial cycles.

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Fig. 4.3 The beginning of the Pleistocene about 2.6 million years ago is visible in an early peak in climatic variability, and the trend to cooler and more variable conditions continues into the Middle Pleistocene. Starting about 900,000 years ago, the periodicity of global glacial–interglacial cycles more than doubles from an Early Pleistocene pattern every 40,000 years to one cycle completed every 100,000 years. The cycles not only became longer but the extremes of cold and warm increased, as did their impact on the environments in which humans lived. (Figure courtesy of Matthew Grove who retains all rights).

from the previous Early Pleistocene pattern of 41,000 years to one of 100,000 years (Fig. 4.3).4 The duration of interglacials also increased 4 The Transition took some time to be completed, which is why some prefer to see it as a transition rather than a revolution. The first signs of a change to a colder glacial cycle appear 1.2 million years ago (MIS 36) with the formation of continental glaciers beyond the poles (Head and Gibbard 2005: 12) and the drying of the tropics as seen in ocean cores (Donges et al. 2011). For some researchers, these global changes mark the start of the Middle Pleistocene (e.g. Potts 2001), whereas the majority agree on a slightly later onset. A large increase in ice volume took place between 940,000 and 880,000 years ago with a reduced flow of the deep ocean currents that transfer warm tropical water northwards and cold arctic waters southward. This flow today keeps north-western Europe warmer than it would otherwise be for its high latitude. During the Transition, the intensification of cold (increased amplitude) and spread of ice sheets reached a peak during MIS 22 (880,000–870,000 years ago), and given the amount of seawater locked up in the ice we can infer that the sea level fell (Head and Gibbard 2005: 13). In terms of new selection pressures, I take this period as the start of the Middle Pleistocene given the severity of cold, even though the 41,000-year glacialinterglacial was still in place. The more widely accepted start is later at 780,000 years ago and is based on a convenient geological marker of a switch in the Earth’s polarity rather than a particular climatic event (Head and Gibbard 2005).

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from 5,000 to 10–15,000 years on average (Ashkenazy and Tziperman 2004). The Transition also continued the Pleistocene trend toward increasingly cool conditions over time, but now with even colder glacial stages and warmer interglacials. A long-term impact from an evolutionary perspective was an increase in the climatic and environmental variability experienced by Middle Pleistocene humans. By 460,000 years ago the 100,000-year glacial-interglacial cycle was firmly established (EPICA 2004), and the Transition was over. Its legacy continued in the duration and amplitude of succeeding cycles. There is one more and important wrinkle to add to the record of fluctuating global climates. It takes the form of short-lived and repeated cold (Heinrich stadials) and warm (Dansgaard-Oeschger interstadials) oscillations. These begin abruptly and then fade gradually over a period of a few hundred years. Deep-sea sediments, icecore sequences, and the thick glacial dust deposits that blanket parts of northern China all preserve records of these climate-change events. They stretch back into the Middle Pleistocene and are well represented in the Later Pleistocene. Their causes are less well understood than the astronomical cycles underlying glacial cycle patterns, but their impact on human populations was much more immediate. The most recent Heinrich cold event (16,000–17,000 years ago) caused extreme drought across the tropics of Africa and Asia (Stager et al. 2011). Monsoon rains shifted and weakened with the result that in Africa the Sahara desert expanded and the Nile ceased to flow. The rainforests of southeast Asia fragmented and dwindled in size. Human populations across a large part of the Old World were affected in just a few years as rainfall patterns changed dramatically. The accumulated wisdom of elders would have been put to the test in the face of such rapid and profound changes. The range of options available may have not been enough to avoid extinction for some communities, and conflict between others. Unfortunately for us, these brief intervals of stress are largely invisible in the Middle Pleistocene archaeological record. Our timeresolution is too poor to give us access to what undoubtedly were periods of enhanced natural selection. We can only speculate about the likely impact they had on the pace of technological innovation. If we broaden our perspective to the level of glacial and interglacial cycles, then broad correlations between climate change and innovation are more likely to come into focus.

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Continental Core Areas The long glacial stages of the Middle Pleistocene not only cooled the planet, they also reduced overall biological activity. The spread of polar ice sheets had the effect of squeezing environmental productivity more towards the equator than today (Trauth et al. 2007). A compressed temperature gradient from the poles toward the equator also drove stronger trade winds, which in turn increased continental drying. These processes would affect regions differently depending on the specifics of topography and latitude, but in general the structure of the food chain on which humans depended was altered over the course of glacial stages. We can use the distribution of hunter-gatherer diets today to imagine the impact of Middle Pleistocene climate change on essential resources for survival. In the tropics, plants form a substantial proportion of the diet along with animal protein, but the dependency on meat and fish increases with distance from the equator to the point of being the sole source of nutrients and energy in the arctic (Hayden 1981). There is a corresponding latitudinal shift in strategies for obtaining food from the equator northwards. As growing seasons become shorter and plant foods are less available, so hunting and fishing necessarily fill the gap. There are general patterns too in technologies related to getting food that change from the equator northwards (Torrence 2001). Tropical hunter-gatherers have less need to design specialized tools if a range of plant and animal food is available throughout the year. Where food is seasonally scarce or available in short-lived abundance, specialized tools for hunting, fishing, and storing food improve the chances of survival. Specialized clothing and housing may also be essential to cope with cold and wet conditions. In the more arid tropics the availability of surface water is an important constraint on where people can live.

Europe This highly simplified latitudinal model of hunter-gatherer subsistence and technology is based on our current interglacial environment. Now imagine this pattern applied to the coldest part of an average glacial stage in the Middle Pleistocene. The spread of ice sheets in the northern hemisphere shifted the high-latitude environment southwards and reduced rainfall in the tropics. We can get some

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appreciation of the impact on the distribution of vegetation by looking at a simplified map of the most recent peak of glacial cold 21,000 years ago. Figure 4.4 shows much of northern Europe and Asia would have been a polar desert with a gradient of vegetation from north to south of tundra, short grassland (steppe), evergreen forest to deciduous forest. An east–west gradient also existed with the spread of dry steppe westwards from Siberia and central Asia. The ‘mammoth-steppe’ of northern Eurasia brought an abundance of meat on the hoof in the form of woolly mammoth, woolly rhinoceros, steppe bison, reindeer (caribou), musk ox, and horse (Lister 2004). These species were adapted to grazing the short grasses and herbs of

Woodland Desert Savanna Steppe tundra Forest steppe Ice sheet and other permanent ice

Fig. 4.4 This simplified map shows the impact of the spread of glacial-stage ice sheets on the distribution of vegetation zones across Europe. The southern Mediterranean rim becomes a region of grassland and forest that could have sustained its human inhabitants. North of this core area lies a large zone of steppe and tundra that extended eastwards into Central Asia. (After Ray and Adams 2001.)

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the steppe. Other species with more flexible diets, such as the red deer, fed on grasses and browsed in woodlands. (North of the steppe the polar bear evolved more than 600,000 years ago as a species superbly adapted to life on ice floes [Hailer et al. 2012].) A core area capable of supporting continuous human occupation existed along the Mediterranean rim of Europe from Italy westwards to Spain. The glacial world of latitudinally compressed habitats and longitudinally expanded steppe was the world in which H. heidelbergensis and then Neanderthals lived (Hublin and Roebroeks 2009). H. erectus may have entered Europe from Africa (or Asia) before the onset of the Transition and its long glacial cycles (Cuenca-Bescós et al. 2005).

Asia The glacial phase deserts that spread from the Arabian Peninsula to central Asia, across north-western India and northern China, made this large area effectively uninhabitable by hunter-gatherers (Fig. 4.5). The rapid uplift of the Tibetan plateau made matters worse by blocking the northward flow of monsoon rains into northern China (Dennell 2009). The spread of deserts had the effect of separating populations of H. erectus (and perhaps H. heidelbergensis and Denisovans), but a few pockets or core areas remained to the south where human occupation continued uninterrupted during the harshest glacial stages. In southeast Asia, lowered sea levels opened a submerged land-bridge that linked the Asian mainland to what is now island Indonesia and Malaysia. This land mass, called Sundaland, was a mosaic of grasslands, woodlands, and remnant patches of rainforest and mangrove thickets (Sémah et al. 2010). H. erectus entered Sundaland early in the Middle Pleistocene and began to evolve into a separate lineage from its continental cousins in China (Antón 2003). On Flores, localized volcanic eruptions complicate the picture of what looks to be a similar pattern of extinctions and new arrivals linked to climate change (Brumm et al. 2010a). A permanent stretch of sea separated Sundaland from the land mass of Sahul to the east (Australia and New Guinea), and this barrier was not breached by humans until the Late Pleistocene.

Africa In tropical Africa the primary impact of the Transition was also one of aridity altering vegetation patterns and dependent animal

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Tropical rainforest, woodland Desert Savanna Semi arid temperate woodland or scrub Steppe tundra Forest steppe Ice sheet and other permanent ice

Fig. 4.5 This distribution of vegetation across glacial-stage Asia shows the vast expanse of arid and semi-arid zones with grasslands extending down through India and southeast Asia (Sundaland). Areas of tropical woodland and rainforest remained in southeast Asia with drier woodlands to the north in southern China, Cambodia, Thailand, and Burma. (After Ray and Adams 2001).

communities. There is a notable period of extreme climate variability at the outset (between 1.1 million and 900,000 years ago) marked by increased seasonality, the expansion of Rift Valley lakes and then their contraction (Trauth et al. 2007). The loss of reliable sources of surface water would undoubtedly have affected local human populations and concentrated others around remaining lakes and rivers. The monsoon belt was compressed and the rains weakened as colder ocean currents spread further towards the equator, so reducing the amount of moisture in the atmosphere. At times of maximum cold the equatorial rainforests fragmented, leaving isolated stands surrounded by more dry adapted woodlands and grasslands (Dupont 2011). The waxing and waning of the rainforest was also affected by the shorter roughly 22,000-year-long orbital cycle known as the ‘precession of the equinoxes’ which affects the amount of sunlight received in the tropics and with it rainfall (see Appendix 2). The Mediterranean coast of north Africa and the Cape Coast of south

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Tropical rainforest, woodland Tropical extreme desert Savanna Semi arid temperate woodland or scrub Forest steppe

Fig. 4.6 Glacial-stage conditions bring an expansion of Africa’s deserts and the fragmentation of its tropical forests. Grasslands become widespread south of the Sahara with open woodland savanna found in the Congo basin into west Africa. The northern and southern coastal margins remain habitable and potential population core areas. (After Ray and Adams 2001.)

Africa both offered potential refuges for hunter-gatherers as moister conditions prevailed (Chase 2010) (Fig. 4.6). East Africa might have been another core area or refuge at times of aridity in central Africa. As we learn more about past climates in Africa, it becomes clear that a simple one-size-fits-all model of dry glacials and wet interglacials no longer reflects the reality of the record (Beuning et al. 2001; Tisserand et al. 2009). Each of the major regions of Africa had its own distinctive response to climate change, which complicates our task of looking for correlations between fluctuating habitats and human responses (Blome et al. 2012).

Barriers, Corridors, and Speciation This extended discussion of past vegetation patterns has highlighted not just the existence of core areas or refugia on each continent, but

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also the creation and removal of barriers to the movement of populations. Geographical barriers are important in the context of the spread of people and innovations as well as the potential loss of expertise through isolation, as happened on Tasmania not so long ago (Henrich 2004). The most significant barrier in the Middle Pleistocene was the spread of glacial-stage deserts. At times of peak dryness the Sahara effectively merged with the Arabian desert and isolated sub-Saharan populations from north African communities and closed connections via the Levantine corridor into western Asia and beyond (Lahr 2010). Within Africa the expansion of the Kalahari towards the equator may have separated populations in western Africa from contacts with groups to the south and east (Thomas and Goudie 1984). Interglacials as times of increased ecological productivity and relative climate stability were also times of population growth and expansion (Powell et al. 2009).5 Connections between Africa and Eurasia reopened (van der Made 2011), allowing for the movement of people as well plants and animals. The reduction of ice sheets allowed the expansion of populations northward into Eurasia, but at the same time new barriers to communication formed in southeast Asia with the rise of sea levels and the inundation of large parts of Sundaland. The spread of tropical rainforests may also have restricted the movement to a species like H. erectus that was probably adapted to the more open glacial landscapes (Storm 2001). In Africa as in Asia and Europe, extinctions of animal populations occurred and new species evolved in response to glacial-stage conditions in the Middle Pleistocene. From the Rift Valley comes evidence 5 We know from detailed climate records spanning our current interglacial (also known as the Holocene, or most ‘recent’ geological era) that this has not been a period of stable climates. The early Holocene of 10,000 years ago was warmer and wetter than today with the Sahara covered in shallow lakes and savanna woodland. The Sahara we recognize today only began to form after 6,100 years ago when the global climate cooled and became drier. Short, sharp fluctuations in temperature and rainfall have occurred in the Holocene as well, some resembling sub-millennial events. More recently within the past 1,200 years there have been two short-lived shifts in temperature and rainfall, the ‘Medieval Warm Phase’ and the ‘Little Ice Age’, which had social and economic consequences for societies in both the Old and New World. An additional division of the geological record has been proposed, called the ‘Anthropocene epoch’, in recognition of the lasting impact that humans have made to the Earth’s climate and ecology since the start of the Industrial Revolution (c. ad 1800) (Zalasiewicz et al. 2011). The recommendation for a formal separation of the Anthropocene from the Holocene is currently being considered by the scientific community.

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that over the course of the Transition and afterwards (992,000 to 350,000 years ago) several species of specialized large grazers (elephants, hippos, zebra, and pigs) became extinct as climate variability increased (Potts and Deino 1995). They were replaced by the forms of these animals we know today, which are smaller and show greater flexibility in their diets. If you accept that a larger-brained form of Homo evolved in Africa about 600,000 years ago (H. heidelbergensis/ H. rhodesiensis) (Rightmire 2004), then its timing correlates well with the establishment of the 100,000-year cycle. Correlation is not causation, but there is at least a whiff of a smoking gun here as largerbrained humans would be better equipped to deal with the new adaptive challenges (Grove 2012).

VARIABILITY SELECTION—ADAPTING TO CHANGING TIMES Now that we have seen the large-scale impact of the Middle Pleistocene Transition it seems obvious that natural selection favoured those species with the most flexible adaptations under rapidly changing conditions. Specialization on the other hand was a recipe for extinction. That, in essence, is the concept of variability selection proposed by evolutionary anthropologist Rick Potts (1996). Potts has worked for many years at the Rift Valley site of Olorgesailie, Kenya, which is a former lake basin whose sediments preserve an exceptionally detailed record of habitat change and human responses spanning most of the Middle Pleistocene (1.2 million to 220,000 years ago). The lake waxed and waned over this time, leaving a record of alternating lake deposits and land surfaces. The large mammals that lived around the lake margins left their footprints and bones, and H. erectus exploited this abundant source of meat and marrow. Stone for making tools had to be carried from the surrounding volcanic highlands, and as the local habitat changed so did the strategies for finding and processing game. At times when the landscape was open grassland and game was dispersed, the hunters followed them and carried their toolkit of sharp flakes and large cutting tools (hand-axes) that could also serve as a source of fresh flakes if needed. When the landscape was more wooded, carcasses were brought to places on the lake margin

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where caches of stone had been placed in advance for making tools for butchering and breaking bone (Potts et al. 1999). The humans here planned their responses to changing circumstances, and the tight dating controls at Olorgesailie give us a rare opportunity to document these responses over relatively short periods of time. We can almost see variability selection in action. Potts has calculated that the residents lived through sixteen largescale changes to the landscape and two sustained periods of environmental change that coincide with the onset of the Middle Pleistocene Transition (Potts 2001). The period between 1 million and 960,000 years ago was probably the most challenging for the locals as they experienced successive upheavals to their habitats roughly every 4,400 years. Their collective response was, as we have seen, to adapt their food-getting strategies to the shifts from open to closed landscapes. This seems like an open and shut case of climate-driven behavioural change, but, as Potts makes clear, we need to be cautious about making snap correlations between apparent cause and effect. The Olorgesailie record shows the importance of understanding how local geological processes, such as tectonic uplift, affect the structure of habitats and how they can override or mimic the effects of climate change. There is, however, the second phase of prolonged environmental change from 800,000 to 600,000 years ago that results in the extinction of specialized large-bodied grass-eaters and their replacement by small species with more diverse diets. It is tempting to see the turnover in species as clear evidence of variability selection in response to climate change, but Potts remains cautious in drawing such a direct link. Despite the high quality of the data at Olorgesailie there are few ‘pure climate signals’ that stand apart from other processes that shape the landscape (Potts 2001: 11). What the long sequence does show is the ability of Middle Pleistocene humans to survive dramatic changes to their habitats by using their wits and tools. Earlier humans in east Africa seem to have been less flexible in the face of major environmental challenges, which points to an increase in cognitive ability in response to intensified pressures of natural selection (Potts 1998). Variability selection as a model offers a way of visualizing the web of connections between environmental complexity, new behavioural responses, and their genetic foundations (Fig. 4.7). Increased brain size, an extended childhood, social

Fig. 4.7 Rick Potts’ model of variability selection as a system of interconnections between climate, landscapes, human culture, and genes. (Used with the permission of the Western Academic & Specialist Press.)

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learning, language, food sharing, and technological innovation are all components of the evolving Middle Pleistocene web.

INTEGRATIVE TECHNOLOGIES Innovation came last on our list of hunter-gatherer responses to environmental stresses, which suggests it is difficult to do and an option of last resort. Not necessarily so. The early sociologists of invention observed that innovation is cumulative and usually incremental in response to changing needs—real and perceived. The inhabitants of Olorgesailie used old technologies (flakes and handaxes), but in new ways in response to changing needs. That is the everyday reality of innovation and it can be done quickly if based on a good understanding of cause and effect combined with craft knowledge. More rarely does an invention come along that offers a radical change in our understanding of the properties of materials and their uses. Hafting emerged from distinctive innovations made over the course of the Middle Pleistocene Transition that contributed to a deepening pool of expertise. The innovations labelled here as integrative technologies share in their making long chains of planning that are executed in a step-wise sequence to achieve a desired goal. They may also involve materials with different properties in the making of a tool, but this is not an essential requirement. Hafting as an invention may have emerged from any one of the integrative technologies or from experience of all three: hand-axes, core preparation, and fire. We will now look at the origin, geographical distribution, uses, as well as the social and cognitive foundations of each.

Large Cutting Tools of the Acheulean Take a close look at the objects in Figures 4.8 and 4.9; note the similarity in shape though one has the pointed end up and the other facing down. These are two especially fine examples of the craft of making large stone tools with extended cutting edges that converge (Fig. 4.8, hand-axe) or expand (Fig. 4.9, cleaver). Both are planned shapes and icons of what archaeologists call the Acheulean tradition or technocomplex. The hand-axe was already an ancient tradition by the start of the Middle Pleistocene with the earliest forms found in

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Fig. 4.8 A late Acheulean hand-axe from Kathu Pan, South Africa, showing highly refined symmetry in plan view.

deposits about 1.8 million years old from northern Kenya (Lake Turkana). These ‘crudely’ shaped tools were made by removing just a few flakes in a sequence from one or both surfaces to define the shape and long cutting edges (Lepre et al. 2011: 82). From an east African origin the craft knowledge of making large cutting tools spread into northern and southern Africa by 1.6 million years ago (Sahnouni 2005; Gibbon et al. 2009), but it never reached deep into the Congo basin. It first appears outside Africa 1.4 million years ago in the Jordanian Rift Valley (Ubeidiya, Israel) (Bar-Yosef and Goren-Inbar 1993). The Valley forms part of the Levantine corridor that links Africa with Eurasia, and from here the Acheulean tradition spread westwards through Turkey (Slimak et al. 2008) or into Europe via the Caucasus and around the Black Sea (Lyubin and Belyaeva 2006). Another potential route for movement of people and ideas was across the narrow stretch of water that separates Africa and the Arabian Peninsula (Bab al-Mendab strait; Derricourt 2005). Arabia

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Fig. 4.9 A late Acheulean cleaver from Kalambo Falls, Zambia, showing the typical broad cutting edges of this tool, but also the skilful tapering retouch on this unusually refined example.

and its coastline may have been the route eastwards into south India where the Acheulean is now known to be at least 1 million years old (Pappu et al. 2011). At the onset of the Transition 900,000 years ago, hand-axes are being made in southern Spain, possibly by humans who crossed the strait of Gibraltar from north Africa using watercraft of some kind (Scott and Gilbert 2009). (Sea crossings, whether from Africa or across island southeast Asia, are often considered as markers of the cognitive ability of H. erectus to plan in depth, but there may also have been the accidental rafting of humans swept out to sea by tsunamis and high tides.) From what seems to be a Mediterranean core region, the knowledge of hand-axe making spread northwards reaching a maximum extent of 52º N in Wales and Germany. Its distribution is not uniform, with hand-axes and cleavers rare in central Europe and across the Russian plain. Their rarity might reflect the lack of suitable sources of large stone with the right properties for knapping (Santonja and Villa 2006). Climate might also have played a

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role especially north of the Caucasus where dry Middle Pleistocene landscapes limited the extent of human settlement (Dennell 2009).

An East-West Divide Harvard archaeologist Hallam Movius (1948) observed long ago that hand-axes and cleavers in Africa, western Asia, south Asia, and western Europe were not only more abundant than in east Asia, but also more refined (thinner) tools. East of what is now known as the ‘Movius Line’ H. erectus used flakes as the primary form of tool and in effect the Acheulean tradition never really spread into eastern Asia, or if it did, it had little impact on entrenched traditions (Brumm and Moore 2012). That east-west distinction has remained largely intact despite more recent discoveries that have filled some gaps in this vast region. Hand-axes and a few cleavers have been found on the Korean Peninsula (Norton et al. 2006) and are probably not much older than about 400,000 years old (De Lumley et al. 2011). Hand-axes have also been found in south China (Bose basin) and here they are dated to early in the Transition (780,000 years ago) by their association with natural glass fragments (tektites) formed by a massive meteor impact in the region (Hou et al. 2000). The tools are generally thick and asymmetrical in keeping with Movius’s observations (Zhang et al. 2009). Thinner hand-axes do occur in central China (Luonan basin) along with cleavers (Wang 2005), and together they hint at a connection with the Acheulean further west, and perhaps they do represent an immigrant population (Petraglia and Shipton 2008). Unfortunately, the age of this material falls within a broad time span of 780,000 to 144,000 years ago (most of the Middle Pleistocene), which does little to help narrow its time or place of origin. On Java, H. erectus did make a few cleavers and thick hand-axes along with more abundant flake tools (Ngebung 2 [Simanjuntak et al. 2010]), but the Acheulean did not spread further east to Flores where stone flakes remained the primary tools starting 800,000 years ago (Mata Menge [Brumm et al. 2010]). The patchy distribution of the Acheulean east of the Movius line has been attributed to a lack of suitable stone in many areas and the use instead of organic materials such as bamboo and shell (Pope 1989; Choi and Driwantoro 2007). This might have been the case in some areas, but on Flores hand-axes could have been made on the local stone. Maybe they were never exposed to Acheulean technology, or if they had been, then the

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knowledge was lost. Archaeologist Robin Dennell (2009: 435) neatly summarizes the situation: humans were thin on the ground during the Middle Pleistocene in Asia, and faced real geographical obstacles moving from a core area like south Asia (India) into China and southeast Asia. The Ganges delta was a formidable barrier, leaving the foothills of the Himalayas as a logical route into east and southeast Asia (Corvinus 2006; Mishra et al. 2010). Those Acheulean-makers who did settle east of the Movius line were few in number, isolated at times, and some communities probably lost the critical expertise needed to maintain this complex technology (Lycett and von CramonTaubadel 2008). Given these geographical and demographic factors, it seems unlikely that east Asia would become the source area for the invention of hafting. That is not to say populations lacked the cognitive ability to innovate, but that limitations of population size, density, and low rates of interaction disrupted the ratchet effect of accumulated cultural change.

Refinements in the Making and Learning Acheulean technology was long-lived but not static. Comparisons of African, Asian, and European hand-axes have revealed regional variability as well as broad regional similarities in basic manufacturing strategies (Wynn and Tierson 1990; Gamble and Marshall 2001; Lycett and Gowlett 2008). For example, early in the Middle Pleistocene in east Africa a variety of different forms of hand-axes were being made at the site of Kilombe, Kenya (Gowlett 2006), and at the same time communities living on the eastern Mediterranean coast were making small tools on flakes struck from pebbles (Ronen 2006). The most interesting development from our perspective was the occasional making of thinner and more symmetrical hand-axes in some areas. These refinements involved additional steps in the planning sequence, considerable skill, and often, but not always, the use of organic materials in their shaping. Refined hand-axes were made in south Asia (Petraglia 2006; Paddayya 2007), western Europe (Roberts and Parfitt 1999; Scott and Gilbert 2009), in parts of Africa (Clark 2001; McBrearty 2001), and perhaps in central China (Petraglia and Shipton 2008). Small refined hand-axes occur late in the Acheulean in southern and eastern Africa (McBrearty 2001; Porat et al. 2010) and in western Europe at a time of considerable technological change (Moncel et al. 2011).

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A hard stone hammer is the basic tool for the initial shaping of a hand-axe or cleaver, but it leaves deep scars on the tool surface and sinuous cutting edges (Newcomer 1971). Further thinning and straightening of the edges usually involves a change from a hard to a ‘soft’ hammer. Soft hammers can be made of wood, bone, or antler, and spread the force of the blow over the surface of the tool. A skilled knapper can achieve the same effect using a hard stone hammer held at a particular angle and applied with the right force (Bradley and Sampson 1986). Thinning a hand-axe, regardless of the kind of hammer used, shows a practical understanding of the physics needed to create a thin tool with a fine straight working edge that is symmetrical in plan view, in cross section, and in side view. Early Pleistocene humans already had experience with using bone for tools, including shaping bone into hand-axes (Backwell and d’Errico 2005), and were certainly familiar with the properties of hard and soft woods (Domínguez-Rodrigo et al. 2001). The earliest indirect evidence of the use of organic hammers comes from early in the Middle Pleistocene Transition (about 800–700,000 years ago), as inferred from the experimental replication of hand-axes from east Africa (Texier 1996) and the recovery of soft hammer thinning flakes from the Jordanian Rift Valley (Gesher Benot Ya’aqov [Goren-Inbar and Sharon 2006]). The oldest antler hammer known is from northwestern Europe at the 500,000-year-old site of Boxgrove, England (Roberts and Parfitt 1999). Some of the flint hand-axes from Boxgrove have been thinned (Fig. 4.10) and the antler hammer bears elegant witness to its use with flint fragments embedded in its broad striking edge. With the innovation of soft hammer flaking using organic tools we move conceptually nearer to the invention of hafting. Two separate realms of craft knowledge are now being integrated in a step-wise sequence to produce a desired goal. The craftsmanship involved in making especially symmetrical pieces (e.g. Fig. 4.7) might reflect an evolving aesthetic sense (Hodgson 2011), and signal to potential mates, allies, and competitors the physical skills of the maker (Kohn and Mithen 1999, but see Machin 2008). At the other end of the skill spectrum, unrefined tools continue to be made throughout the long history of the Acheulean. Even rarer than the occasional masterpiece of symmetry are the perfect miniatures that could be interpreted as toys (e.g. White and Plunkett 2004: Fig. 8.13ii), much like the small bows made to prepare Agta boys for their adult role as hunters in the

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Fig. 4.10 A small late Acheulean hand-axe from Boxgrove, England, made with the use of a soft hammer.

Congo (Hewlett et al. 2011). These variants in the size and shapes of hand-axes remind us of the extent of social learning embedded in this technology. Experimental studies have shown that there are significant differences between novice and skilled knappers in their ability to detach flakes from a core (Nonaka et al. 2010) and to manage the complex three-dimensional form of a hand-axe (Geribas et al. 2010). Hand-eye coordination develops with practice and becomes embedded in the neural networks that link posture with the movement of the limbs.

What Were they Used for? There is much debate on the existence of socially transmitted traditions in the Acheulean, with some archaeologists seeing little evidence for social learning in the making of hand-axes, especially those with minimal shaping (McNabb et al. 2004). Others argue from a broad comparative perspective for the Acheulean being one long continuous tradition in which the basic form of the hand-axe was handed down from generation to generation (Lycett and Gowlett 2008: 309). Regional variants will arise over time that build on the basic form and that reflect local trajectories of differences in

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population size, resources, and learned traditions of use. Variations in the size and shape of individual artefacts can also reflect how often a tool was resharpened (McPherron 2000), but even the extent of resharpening could be a learned tradition. Such subtleties of behaviour are difficult to disentangle by shape and size alone. I keep several blunt and no longer functional screwdrivers in my toolkit because they are still useful for other purposes. The strong edge is good for opening tins of paint and then the whole blade for mixing the paint. They are still recognizable as screwdrivers, but they now have a new life. An archaeologist might be able to reconstruct this use history by looking at the overlay of microscopic damage to the tip of these tools and by the dried splodges of paint on the blade. The same process of deduction is being used to infer the use of hand-axes, starting with the making and use of replicas. Replica hand-axes have been used to butcher large game (e.g. Jones 1980; Schick and Toth 1993; Mitchell 1996), and in one experiment two professional butchers recorded the effectiveness of oval-shaped hand-axes as knives for dismembering deer. Their experience revealed the practical limitations of these tools when compared with modern steel knives—they blunt quickly and become clogged with flesh (Machin et al. 2007). These also reveal the advantages of having a handle on the blade. Imagine holding a tool in your hand that is heavy, thick, and has a sharp cutting edge all around its periphery. You don’t want to cut yourself. What kind of grip would you use? Recall that the thumb and forefinger are critical digits that make up the precision pinch grip (Tocheri et al. 2008). As Figure 4.11 shows, it is relatively easy to hold a hand-axe between the thumb on one side and the fingers on the other and to use it in a sweeping arc to cut (Mitchell 1996). A flick of the wrist helps to make finer, more controlled slices. The flexibility of the palm keeps it free of contact with the sharp cutting edge. I find this a tiring grip for prolonged use and prefer the comfort and strength of the power grip. Wrapping the hand-axe in thick hide or bark is a practical solution that allows you to grasp the tool, but if it is a large and bulky hand-axe then you will need to use both hands (e.g. Gowlett 1999). A protective wrapping or pad is the simplest and probably the earliest kind of added handle invented. Alternatively, you could make the hand-axe so that some of the natural worn exterior or cortex is left intact for ease of grip, but this comes at the expense of the length of the cutting edge.

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Fig. 4.11 This precision grip minimizes the risk of cutting the hand and is also effective for using the tool as a knife.

There is persuasive archaeological and experimental evidence from a very small number of studies that some hand-axes were used as butchery tools, but also to cut wood and other plant materials. Microscopic traces of use observed on excavated tools have been compared with traces on replicas used for a variety of purposes and on different materials. The experimental results show the hand-axe to be effective in cutting through the thick skin and tendons of large animals such as elephants (Keeley 1980; Schick and Toth 1993; Parfitt and Roberts 1999). Microscopic traces of acacia wood have been found adhering to the edges of hand-axes at one very early east African site (Peninj, Tanzania [Domínguez-Rodrigo et al. 2001]). Two hand-axes from the south African site of Wonderwerk Cave also show microscopic traces of shaving wood and cutting tough plant materials, perhaps used as bedding (Binneman and Beaumont 1992). Cleavers are thought to be specialized tools used in a chopping motion (Roe 2006: 320), and to the untrained eye the typically thin cutting edge looks too fragile to be used to work hard wood and bone, so maybe they were used for cutting meat or soft plants. There is tantalizing experimental evidence, however, that a hafted cleaver makes a very effective woodworking tool, especially when compared with its use without a handle (Watts 2006).6 There is certainly the 6 A claim has been made that traces of organic resins (palm tree) and binders (grasses) were identified on late Acheulean hand-axes from the site of Tabun, Israel

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need for more research on cleavers and hand-axes, and especially on carefully shaped and thinned specimens. The artefact in Figure 4.9 is an unusually symmetrical cleaver that was shaped to a tapering point opposite the broad cutting edge. The specimen, from the late Acheulean site of Kalambo Falls, Zambia, is a candidate for considering the possibility that some cleavers might have been designed for hafting, and there is clearly great scope for further experimental analysis of their uses.

The Mind behind the Artefact Looking at Figure 4.7 again, now draw an imaginary line along the long axis and the two halves are nearly mirror images of each other. That symmetry also exists in profile (side view) and in cross section. The books and DVDs on my shelves have this three-dimensional regularity, as do cushions on the furniture and bottles in the kitchen. Symmetry can be manufactured on a large scale using industrial processes—once the form or mould is made—but making symmetrical tools by hand and from hard stone requires considerable skill and time to learn (Edwards 2001). Thomas Wynn (2002), an archaeologist with a long-standing interest in the evolution of the human mind, sees three important developments represented in the more refined symmetry of later hand-axes. First, the knapper had to hold in mind three-dimensional views of the tool in order to guide the making. Second, the knapper understood the consequences of each step of flake removal, and compared the results against mental images. Third, these tools were ultimately abstract ideas (categories) imposed on stone and as such they reflect the existence of a distinctively human form of culture (Holloway 1969). Not all archaeologists and psychologists agree with Wynn’s interpretation (e.g. McPherron 2000 and replies in Wynn 2002), but most accept the reality of the

(Gorski 2002). This is potentially a very significant finding given the age of this level of the site (about 400,000 years ago). The report is unpublished, but I am grateful to Dr Ariel Gorski for allowing me to see photographs of the artefacts. Unfortunately, they are not hand-axes but Middle Palaeolithic flake tools, an attribution supported by Professor Naama Goren-Inbar. The identification of hafting traces is still important, as there are very few artefacts that have been examined systematically for traces of hafting (in this case using gas chromatography-mass spectrometry to identify the chemical signatures of the compounds).

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hand-axe as a repeated form and some later hand-axes as more skilfully produced than earlier forms. To this outline of the cognitive implications of hand-axe symmetry we can add the observations from neural-imaging research of the interplay between networks in the left and right hemispheres of the brain in the planning and making of more refined hand-axes (Stout et al. 2011; Stout and Chaminade 2012). The right hemisphere in particular was involved in the extended hierarchical planning needed to envisage the task, and the left-hemisphere networks (recall the inferior frontal gyrus or IFG) were active in coordinating visual and spatial information with the motor actions needed to shape the tool. In living humans, the networks engaged in hand-axe making are shared with those involved in speech production and other complex hierarchically organized activities such as music-making and mathematical reasoning. We cannot know for certain how the brains of late Acheulean tool-makers were organized, but if we assume that the neural organization was similar to that of today then the cognitive capacity for making hafted tools existed 500,000 or so years ago. That capacity co-evolved with the long tradition of hand-axe making over a period of more than a million years. The hierarchical structure of this technology gives it its pride of place in the small cluster of integrative technologies that pre-date and prefigure the invention of hafting. That sequential structure becomes extended further if we list the series of steps and decisions needed to make a refined hand-axe (Table 4.1). There are five basic actions involved from acquiring the raw material to discarding the used tool and between twenty-five and twenty-eight decisions to be made based on ‘understandings’ of the properties of materials, techniques of manufacture, actions of use, and appropriate places for these activities. The number of understandings increases if the tool has to be abandoned during manufacturing and the process restarted, or if there are multiple episodes of resharpening before the tool is deemed useless. In the rare archaeological cases where we can reconstruct the decision-making process by refitting the flakes to the artefacts, we can detect an extended attention span between the making and use of an artefact (Hallos 2005). There is a mind at work that can maintain a long-term goal even if its attainment involves delays and the physical separation of the sequence of actions. An extended working memory would be needed along with the ability to imagine and work towards a future goal. The concept of constructive memory embodies this

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Table 4.1. The actions and understandings needed to make a thinned biface using a soft hammer made from an organic material such as bone or wood. HAND-AXE Actions Get raw material

Rough-out

Shaping Thinning Use/Maintenance

Understandings (a) properties of material for task (b) distance to source (c) extraction methods (d) transport back or in situ ! (e) appropriate place, time of action (f) hammer stone properties (repeat a–d) (g) technique: core-preparation or direct reduction—grips, angles, force needed, etc. (h) managing dimensions against goal (i) discard or continue ! (j) select tools (repeat a–d) (k) managing dimensions against goal (l) discard or continue ! (m) choice of soft hammer (repeat a–d) (n) managing dimensions against goal (o) discard or continue ! (p) match skills to tasks (q) resharpen (repeat j–k), curate or ! (r) discard (repeat e).

hierarchical process that was essential for the invention of hafted tools (Ambrose 2010). Its roots can be seen in the technologies of the later Acheulean.

More than Hand-Axes and Cleavers Acheulean communities did not live by hand-axes and cleavers alone. They made a range of other large and small tools that deserve mention as part of the pool of craft knowledge from which hafting emerged. These are not integrative technologies because they require less planning in their making and use, but they were essential components of daily life. Archaeologists have long made a distinction between ‘light’ and ‘heavy duty’ tools that has been applied to the Acheulean and even earlier stone technologies (Clark 1974). Light-duty tools include small flakes that were deliberately shaped using another tool to serrate, blunt, or change the angle of the working edge. These small retouched flake tools were probably used for basic tasks such as scraping, whittling, sawing, cutting, and drilling or piercing. Heavy-duty tools

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are less easy to summarize because they were not made on one kind of blank. They could be made on old cores, on large flakes, or on cobbles. Their uses, like those of light-duty tools, are presumed rather than known with certainty, but because they are heavy their uses presumably needed the weight of the tool behind the action. Chopping wood, digging into hard ground, or breaking bone might be some of their uses, and we can add to the list stone anvils as supports for cracking hard objects (nuts, bone, pebbles), or for grinding. Stone balls (‘spheroids’) are also part of the heavy-duty repertoire in Africa. Various uses have been suggested for these objects over the years, including weapons, either thrown individually or tied together to make a spinning hunting weapon hurled into a flock of birds or herd of game. There is little evidence for such dramatic uses, and experimental replication combined with microscopic analyses of their surfaces points to more mundane roles as hammers and grinding stones (Willoughby 1987; Schick and Toth 1993). The longevity of these hand-held tools—many continue to be made right to the end of the Stone Age—reflects their usefulness in meeting basics needs. A hand-axe, which we could assume might be a robust butchering tool, for example, would be an awkward hammer stone. Light- and heavy-duty tools probably had another key role and that was to make other tools which might be used to make other tools, and so on (Keeley 1980). This extended supporting role makes them potential conceptual links to the invention of the combinatorial principle and hafting. In some regions of the Old World, the range and frequency of light-duty tools increases in the later Acheulean. This is the case in east Africa where scraping, piercing, and grinding tools become more common and are more carefully shaped than before (Kleindienst 1961; Clark 1970). The end of the Acheulean in western Europe is associated with an increase in the range of lightduty tools made (Moncel et al. 2011: 55).7 In central Europe, where hand-axes and cleavers were always rare, small tools were the norm, to the extent that archaeologists recognize a ‘small tool tradition’ in the Middle Pleistocene (about 600–300,000 years ago) (Burdukiewicz 7

Neanderthals in northwestern Europe made, after 60,000 bp, a form of small broad-based biface, the ‘bout coupé’, that is not considered here as the technological equivalent to Acheulean hand-axes (Villa 2009). This distinctive biface does demonstrate the principle of independent invention (convergence) or reinvention of an older approach to making a bifacial tool, though in this case we cannot assume that it served the same functions as larger hand-axes.

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and Ronen 2003). The rarity of hand-axes might reflect a lack of large cobbles in the region, but even where they were available the artisans of the region still preferred to make small scraping, cutting, and boring tools (Brühl 2003; Glaesslein 2009). Some of the tools are so small, just 2–3 centimetres in length, that it is argued that they could only have been used as hafted inserts (Burdukiewicz 2003: 71). We will revisit this claim in the next chapter. As mentioned, small flakes tools were being made 1 million years ago on the shores of the eastern Mediterranean and by choice rather than raw material-driven necessity (Ronen 2006). In the same region, flake tools, in particular well-made scrapers, gradually replace handaxes, marking the end of the Acheulean about 300,000 years ago (Gisis and Ronen 2006). In parts of south Asia there is also shift in emphasis late in the Acheulean towards flake tools as well as a trend towards the making of smaller hand-axes (Misra 1985; Chauhan 2010). The intriguing observation has been made that some of the small neatly crafted hand-axes might have been designed for hafting (Paddayya 2007: Fig. 17). In east and southeast Asia flake tools, large and small, were already the mainstay of the Middle Pleistocene toolkit and continued to be so after the disappearance of hand-axes (Moore and Brumm 2007; Norton et al. 2009; De Lumley et al. 2011).

PREPARING A CORE AND THE END OF A TRADITION The gradual abandonment of the hand-axe and cleaver has its modern parallels. Not so very long ago we were still using typewriters (manual and electric) at a time when personal computers began to infiltrate the home, having first colonized the office. How many of us now still use a typewriter? I have one in the basement, along with the blunt screwdrivers, that never now sees the light of day. The disappearance of large hand-held cutting tools probably followed a similar process of gradual displacement as other more efficient tools replaced their various functions. The process began with an innovation that is our second integrative technology; the preparation of cores for the removal of flakes of a more standardized shape, thickness, and size. Early in the Middle Pleistocene of southwest Asia and parts of Africa an innovation was made in the way large flakes were produced as blanks for making hand-axes and cleavers. We are familiar with

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hand-axes as symmetrical tools in three dimensions. They can be made by using a hard hammer to rough-out the basic shape and then thinned with a soft hammer. Alternatively, they can be made by first striking a large flake from a core and then shaping the flake by retouch if needed (Fig. 4.12). These two basic strategies are widespread and at the continental scale the choice of approach reflects basic differences in raw materials between flint and non-flint regions (Gamble and Marshall 2001). At the local scale there are cultural traditions that use both strategies, sometimes with cobbles for handaxes and large flakes preferred for cleavers (Shipton et al. 2009; Zhang et al. 2009). The innovation builds on the inherent advantages of a large flake with its already thinned form and long sharp cutting edges. Thinning by retouch takes time, experience, and runs the risk of breaking the tool, encountering a flaw in the rock, or creating a deep scar that is hard to remove. If you start with a thin blank then so much the better, as there is less to do before using the tool (Jones 1979). Producing flakes with predictable dimensions is the hallmark of prepared-core technology as an integrative technology.

4

2 1 3

Fig. 4.12 To prepare a core to produce a large flake the knapper needs to envisage the end product in the block of stone (in this case a cleaver) and then control the dimensions of length, width, thickness, before striking the blow (arrow) that releases the pre-shaped blank. (Courtesy of John Gowlett who retains all rights.)

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Whereas hand-axes are symmetrical, the prepared-core methods innovated in the Middle Pleistocene all relied on creating an asymmetrical form characterized by a domed (convex) flake removal surface opposite a thicker and steeply angled base. It is an odd combination that reveals a developed understanding—a folk physics—of the geometry of surface angles and the flow of force through a volume of stone. The angled base forms the periphery from which flakes are removed to form the convex surface with its interconnecting flake scars. The scars guide the shock waves from a hard hammer blow delivered at one end of the long axis of the core (Van Peer 1992). A large thin flake results and the core surface can be reshaped to produce more flakes with similar dimensions. This sequential and hierarchical process is generally known as the Levallois method of flake production (or prepared-core reduction) (Inizan et al. 1992). Sometimes a piece of stone might already have the necessary asymmetry of the surfaces and so less preparation is necessary, but conceptually the process shows the same understanding of core geometry but without the added fuss (Wilkins et al. 2010).

A Single Origin? Most archaeologists equate the Levallois method with the making of small flakes for hafting. That may have been the case later on, but the origin of this innovation lies in the Acheulean and probably from the long experience of shaping two convex surfaces that intersect along a plane (Rolland 1995). The folk physics were in place and given the widespread distribution of hand-axe making we can expect innovations in more than one place and at more than one time, based on a common conceptual foundation. That is the view taken here, but there are proponents of a single African origin among populations of H. heidelbergensis or its descendants who then spread into Eurasia about 300,000 years ago carrying the knowledge with them (Lahr and Foley 2001; Sharon and Beaumont 2006). In this view, local indigenous populations of Neanderthals learned how to make Levallois flakes from immigrant African groups and by implication also how to haft tools. The alternative view of multiple independent areas of innovation draws support from the archaeological evidence of the gradual emergence of the Levallois method in western Europe (Rolland 1995; White and Ashton 2003; Moncel et al. 2011) and before the proposed spread from an African source. This stance is accompanied by

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adherence to a strict set of technical criteria by which the Levallois method is recognized and all of which must be present to qualify, otherwise the term ‘proto-Levallois’ is used almost dismissively. Others take a more relaxed view of the definition and accept as Levallois those cores which were selected because their natural shapes would guide the force of the blow without the need for extensive surface preparation. With that looser definition in mind we can begin to detect the early roots of prepared-core technology in the Middle Pleistocene.

Southwest Asia, Africa, and South Asia There is evidence of prepared cores being made about 870,000 years ago in the Levantine corridor at the lakeside site of Gesher Benot Ya’aqov, Israel (Goren-Inbar and Saragusti 1996). In south Africa at about the same time the Victoria West technique of core preparation with its three specialized variants is widespread across the Karoo region (Kuman 2001; McNabb 2001; Sharon and Beaumont 2006) (Fig. 4.13). In both settings, large flake blanks were used to make hand-axes, cleavers, and other tools such as scrapers and knives. One variant of the Victoria West strategy was designed to produce large flakes that could be held comfortably in the hand with one edge left naturally blunt and opposite a sharp cutting edge. Though separated by the length of the African continent, the techniques used were conceptually similar with the convex surface struck instead from

Fig. 4.13 A Victoria West core from South Africa showing the scars from preparing the surfaces to remove a hand-axe or cleaver blank.

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the side or off-centre from the long axis (Goren-Inbar and Saragusti 1996). The resulting flake was short, broad, and had a pronounced bulge at the point of percussion. The bulge provided a ready-made grip or it could be thinned by further flaking to give a more symmetrical profile and continuous cutting edge. The Victoria West technique and its Levantine counterpart may not be the immediate precursors of the Levallois method (Lycett et al. 2010), but they do show a developed understanding of how to manipulate core geometry and the hierarchical relationship between the two surfaces. The full Levallois method appears in east Africa about 500,000–300,000 years ago as part of the late Acheulean sequence at the Kapthurin Formation, Kenya (Tryon et al. 2006). Cleaver blanks were struck on the long axis of carefully prepared cores, and though larger than Levallois cores from later in the sequence they are otherwise conceptually the same. There are examples elsewhere in Africa of Levallois-like methods used to produce cleaver blanks, but these remain to be dated (Tixier 1957; Clark 2001). It was not just in Africa that Acheulean technologists were actively developing new ways of making large cutting tools.8 A similar awareness of core geometry is seen in various parts of India (James and Petraglia 2009), and at the site of Chikri more than one method of core preparation was used to make cleaver blanks (Petraglia 2006). Chikri looks to be older than 600,000 years ago (Gillard et al. 2010), which makes it comparable in age to its technological counterparts in Africa and southwest Asia.

8 The ‘Kombewa’ technique is another method of producing flake blanks (Owen 1938). It involves striking a flake from a core and then using the flake as a core. The flake is turned over, and the bulbous projection formed by the force of the blow is struck to release a flake that has a bulb on both sides (‘Janus’ flake). The flake is convex either side of a continuous cutting edge which can be used with or without further shaping. The technique involves planning and a good understanding of geometry combined with skill to consistently produce large blanks. It is found in east Africa, north Africa, and dated to 870,000 years ago in the Jordanian Rift Valley (Gesher Benot Ya’aqov) where it was used as a blank for making bifaces (Goren-Inbar and Saragusti 1996). Its presence in the Levantine corridor is considered evidence for the movement of Acheulean technology (and presumably its makers) into the region from Africa (Ronen 2006). It also occurs in northwestern and central India where it was used to make blanks for cleavers (Gaillard et al. 2008, Gaillard et al. 2010), as was the case in south-central Spain (Santonja and Villa 2006: 436). In those parts of east Asia (south China) and island southeast Asia (Java) where bifaces occur, the Kombewa technique is also present (Wang 2005; Zhang et al. 2010).

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Separate Pathways In western Europe we see again the association of prepared cores with cleavers (Santonja and Villa 2006), but on the whole cleavers were a much less common part of the Acheulean toolkit in Europe than elsewhere. The roots of the Levallois method here may lie in a different set of priorities that emphasized the making of flake tools, such as scrapers as well as hand-axes. Early examples of simple core preparation to produce flake blanks (proto-Levallois) are found in northwest Europe between 400,000 and 300,000 years ago (White and Ashton 2003), and eastwards into the Ukraine (Adamenko and Gladiline 1989). There is also evidence that knappers applied their understanding of the process of thinning hand-axes to preparing the surfaces of broken and thick hand-axes for removing large flakes (e.g. Cagny La Garenne, France [Tuffreau and Antoine 1995]). By 300,000 years ago the period of experimentation seems to be over with the Levallois method now fully established in southern Europe (e.g. Orgnac 3, France [Moncel et al. 2011]). Perhaps it was no coincidence that the populations living in this core area—no pun intended—had perfected prepared-core technology. The area from Spain to Italy was continuously occupied during the Middle Pleistocene (Hublin and Roebroeks 2009), which allowed innovations to accumulate over the generations. East of the Movius line, there is only limited evidence of core preparation and that comes from northern China where it may be only 200,000 years old (Dingcun locality [Norton et al. 2006: 532]). Elsewhere in east and southeast Asia the Levallois method is effectively absent (Lycett and Norton 2010). Why? The answer lies in the same mix of geographical and demographic factors that limited the spread and retention of the Acheulean in these regions (Brantingham et al. 2000). And without a well-developed Acheulean foundation it was unlikely that core preparation would emerge independently or spread far (Lycett 2007). There are a limited number of strategies for removing large flakes from a block of stone, and over time they will be discovered by skilled knappers. Those areas that remained inhabited during the harshest periods of the Middle Pleistocene, such as southern India, the Mediterranean rim, and parts of eastern, central, and southern Africa were all potential centres for independent innovation. Current evidence leads to the conclusion that west of the Movius line experienced

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knappers converged on similar approaches to making tools on large flakes (Sharon 2009). Flakes as blanks maximized the extent of a useable cutting edge and minimized the need for further thinning. This is an argument for efficiency as the driver of these innovations with similar solutions arising from similar basic needs. Multiple centres of independent invention might seem unlikely given the complexity of prepared-core technologies, but as the archaeological record shows there was more than one path to the innovation of the Levallois method.

BLADES—A NEW KIND OF EDGE There is another kind of flake that was a product of the minds of Acheulean tool makers and that is the blade. Blades are flakes that are twice as long as they are wide. That is the barest definition, to which we can add the requirement that the cutting edges are parallel, which gives a blade its rectangular shape. Blades are also recognized by the one or two ridges that run down the spine and which carried the force of the hammer blow (Inizan et al. 1992). Until fairly recently, blades were considered as the hallmark technology of H. sapiens and the ability to make them signalled the cognitive superiority of our species over Neanderthals, who never progressed beyond Levallois flakes (Bar-Yosef and Kuhn 1999). That triumphant narrative has been abandoned in the face of powerful evidence to the contrary. Neanderthals made blades long before the arrival of modern humans in Europe, and H. heidelbergensis (or H. helmei) was making blades before the evolution of H. sapiens around 200,000 years ago. The invention of blade-making also fed into a presumed progression of ever more efficient technologies, with blade cores said to produce more cutting edge per volume of stone compared with flakes made on prepared cores (Bordaz 1970). That shibboleth too has been challenged, with blade-making shown in one study to be no more efficient than removing flakes sequentially around the periphery of a flake core (Eren et al. 2008). Blade-making can also be a fussy process, not just because more preparation is needed, but also for the high risk of failure with blades snapping on removal and leaving the core either unusable or needing reworking (Bar-Yosef and Kuhn 1999). Blade-making also requires a higher-

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quality raw material (more homogeneous and glassy) than is needed for ordinary flake-making. On balance, it is a strategy demanding on resources and expertise, but what it offers in return is very thin, sharp, and straight cutting edges; just what is needed for slicing soft materials like meat or plants. Blades are lightweight and portable too. From the perspective of our interest in the precursors of hafting, blades are important because they, like flakes, would make effective working edges when set in a handle or shaft. The hafting of blades is now well known in the archaeological record of southern Africa from 77,000 years ago (see Chapter 6), but they appear much earlier in parts of Africa and southwest Asia in the late Acheulean. Were these early blades also hafted or did they represent another option in the growing repertoire of light and portable cutting edges? These are key questions in piecing together the puzzle of the origin of hafting. Returning to the Kapthurin Formation, Kenya, there is now evidence for blade-making as early as 545,000 years ago, before the development of the Levallois method (Johnston and McBrearty 2010). The artefact numbers are very small, but the cores do show an understanding of the process of establishing a ridge to guide subsequent blade removals. That knowledge is also evident later in the Kapthurin sequence between 509,000 and 285,000 years ago when Levallois and blades cores are both used to produce consistently long, thin, and flat blades (McBrearty 2001). The Kapthurin blades are some of the earliest reported and are probably the handiwork of H. heidelbergensis (or H. rhodesiensis, depending on your reading of the fossil record).

Evidence of Use What these blades were used for and how they were held remains a matter of guesswork, but the Israeli site of Qesem Cave offers a rare early blade assemblage that preserves microscopic traces of use (Lemorini et al. 2006). The human occupation began between about 420,000 and 320,000 years ago and ended roughly 200,000 years ago, with the archaeological material all belonging to a final phase of the Acheulean known regionally as the Acheulo-Yabrudian Cultural Complex (Gopher et al. 2010). The Complex contains several industries including the Amudian, which is composed largely of blades and blade-based tools. The cores are designed to produce a series of blades including those that retain the natural exterior (cortex) on one edge

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opposite a sharp cutting edge (Shimelmitz et al. 2011). The blunt cortex edge provided an inbuilt grip that would not cut the hand (Barkai et al. 2005). Known as naturally backed knives, these blades could be used on their own without further shaping (Fig. 4.14). Some thicker blades were selected for shaping into scraping tools or deliberately blunted forming a curved edge opposite a sharp edge. Perhaps the blunting improved the grip or possibly it was done in preparation for hafting, but most of the blades from Qesem Cave were naturally backed and probably intended for hand held use.

Fig. 4.14 Blades from Qesem Cave, Israel, showing the retention of the natural cortex (stippled) on one edge opposite the sharp cutting edge. This natural backing provides a ready grip that protects the hand. (Reproduced from Barkai et al. 2009 with the permission of Elsevier Ltd.)

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The microscopic examination of traces of wear (e.g. polishes and small flake scars) on the Qesem blades has revealed that naturally backed knives were primarily used to cut soft materials such as fleshy tissues or herbaceous plants (Lemorini et al. 2006: 925). The thicker retouched blades were used to scrape soft and moderately hard materials, such as skin and wood. The long, thin sharp edges of the knives made them effective slicing tools, and the retouched edges of the thicker blades gave them the added strength needed for dragging across tougher materials. We can be a bit more specific about the likely uses of these blades given the preservation of the bones of the animals hunted, butchered, and eaten by the occupants. The hunters focused on a small range of large and medium-sized game of which fallow deer seems to have been the meat of first choice followed by aurochs (wild cattle), horse, wild pig, red deer, and wild ass (Stiner et al. 2011). Tortoise was also on the menu. The big mammals were all Eurasian species which suggests that at this time the Sahara was at its full extent and blocking movement between Africa and Eurasia. Later, about 170,000 years ago, African and Arabian mammals (e.g. mountain gazelle) would move into this coastal region of the Levant. The occupants of Qesem brought the meaty upper limbs (and heads) to the site where they were then defleshed, with stone tools used to cut connective tissue that held the muscles to the bone. We know this because the tools left tell-tale cut-marks on the bone of straight sharp edges, which suggests blades were used. The tools were discarded before they became blunt ,which probably means the knappers had a clear idea in mind about the purpose of the blades, and once used, new ones could be made quickly.

Blades in Perspective We should not generalize about the use of blades in the late Acheulean on the basis of this one study, but—and it is a Big But—it is tempting to see in the lightweight, thin, sharp, and straight cutting edge a set of practical advantages over the heavy, thicker-edged handaxe as a butchery tool. If you recall, the modern butcher’s experience with ovate-shaped hand-axes was that the edges soon clogged with fat and tissue (Machin et al. 2007). The exception awaiting experimental trial is the clean cutting edge of the cleaver, which is blade-like in form but which offers the weight of the body of the tool behind it for heavy-duty work. We still do not know what cleavers were used for,

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but—and it is another Big But—if they were primarily tools for butchery then the invention of smaller more expedient alternatives might explain the eventual abandonment of these bifaces. Many flakes and blades can be made from a single block of raw material, and used immediately for cutting or reshaped into other tool forms, then discarded after use. Their small size and sharp edges in fact limit the extent to which they can be resharpened when compared with large bifaces. The trade-offs between the potential longevity of handaxes and the immediacy of flakes/blades were weighed in the balance as their makers considered their food-getting strategies in relation to the availability of high-quality local stone (Delagnes and Rendu 2011). The Levallois method and blade methods extended the range of subsistence options available to a community, and in doing so had the potential evolutionary impact of not just increasing their odds of survival but also their numbers over time. If that was the case then the advent of hafting would have hastened this process. Looking beyond Qesem and the Kapthurin Formation, early blade technology is also found in southern Africa in the Middle Pleistocene Fauresmith industry. The Fauresmith, named after a locality in the Northern Cape, resembles the Acheulo-Yabrudian Complex in having a range of old and new technologies. The old is represented by bifaces, including some finely retouched small hand-axes, and the innovations by long blades and prepared cores (Levallois) for the making of points (Mitchell 2002). The age range of the Fauresmith remains a matter of contention (Herries 2011), but the earliest dated deposits are from the spring site of Kathu Pan 1. They are roughly 500,000 years old, making them comparable in age to the early blade sites in the Kapthurin Formation (Porat et al. 2010), but there the similarity ends. The makers of the Kathu Pan blades invested more effort in making blades from prepared cores, made more blades and shaped some into points (Wilkins and Chazan 2012). The points may have been used as spear tips or knives as part of hafted tools, but for the moment we simply do not know how they were used or held. Evidence of blade technology is also found in the late Acheulean of India (James and Petraglia 2009), but it remains poorly dated. For now, eastern and southern Africa are the two earliest centres of blademaking with the Levant a close runner-up. In each of these areas, blades developed as part of the increasingly diverse ways of making lightweight tools. Hand-axes and cleavers were still part of the craft knowledge, but the toolmakers of the time now had more options in

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the collective toolkit. There are regional differences too that point to separate pathways to development rather than a single origin of blade-making. Blades precede the Levallois method in the Kapthurin Formation, but they are coeval in the Fauresmith. Recall too that the prepared flakes used to make cleavers in southern Africa were struck from one side of the core, whereas in the Kapthurin Acheulean they were struck from the end of the core. These subtle variations reflect the process of cumulative change in the craft knowledge of communities over time. They also remind us that the tedious detail of stone-tool analysis is an essential source of information about how technology evolved. They are our analytical equivalent to Darwin’s observation of variation in the beaks of finches on the Galagapos Islands.

FIRE AS INTEGRATIVE TECHNOLOGY AND SOCIAL GLUE Chances are you no longer rely on a naked flame to heat your home, cook your food, to keep you safe from predators, and to light the long night. If you do have a fireplace and live in a city, then maybe there is a gas flame lit with the touch of a button to give a sense of warmth and homeliness. With a gas fire there is no need to plan ahead about keeping a wood pile or any other fuel in storage. No need either to learn the skill of lighting a fire by friction or how to rekindle a fire from a glowing ember in the morning. No need either to keep fuelling it; that chore is handled by a long chain of industrial infrastructure. It is easy then to take the use of fire for granted because it is no longer a central part of our lives. At some point in the past the means of making fire at will was invented, and as argued here it was an integrative technology based on an understanding of the process of combustion. Fire was also a tool in that it was used to do work, but unlike hand-held tools it was not a physical extension of the body. It was an extension of an understanding of how to manipulate a natural source of energy to fulfil certain basic needs, but it had unforeseen consequences on human evolution. The archaeological record points to an early use of natural sources of fire in the Pleistocene and the later development

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of fire-making technologies in the Middle Pleistocene. There is good ethnographic and archaeological evidence, too, of the many ways fire can be made across a range of environments. Before looking at this evidence, it is worth considering briefly the impacts of this invention on human social and biological evolution, given they have a direct relevance to our model of Middle Pleistocene societies organized around food sharing, an extended childhood, delayed brain growth, a division of labour, and now the hearth. As well as its obvious uses of providing heat and protection, fire also changed our patterns of waking and sleeping. The light of a fire has lengthened our working and socializing day beyond that of any primate (Gowlett 2010). We have extra time in the evenings for interacting with others, to plan, to repair tools, or simply slump in front of the television. There are other practical advantages, including ridding campsites of vermin, managing plant growth, increasing habitat diversity (Bird et al. 2008), and in terms of tool-making the charring of wood makes it easier to work and may harden the tip of a spear or digging stick. Cooking has changed us biologically as we no longer need large teeth for chewing tough raw foods, and our digestive system has evolved to be efficient at extracting energy and nutrients from cooked meats and root vegetables (Wrangham et al. 1999). Cooperative hunting and food sharing become even more viable and valuable behaviours that in turn contribute to the co-evolution of brain size (Fonseca–Azevedo and Herculano–Houzel 2012) and an extended childhood. The hearth has now become a valuable source of evidence not just for the control of fire, but also for its evolutionary impacts.

The Spread of Fire in the Middle Pleistocene Given the many benefits of fire, we might expect that once this source of energy was controlled that the knowledge would spread like, well, wildfire, but that does not seem to have been the case. There is a long interval between the first appearance of fire in the archaeological record 1.6 million years ago in east Africa (Clark and Harris 1985) and clear evidence for its controlled use. That earliest widely accepted evidence for the ability to make fire at will and repeatedly over time comes from the now very familiar site of Gesher Benot Ya’aqov, Israel (about 780,000 years ago). This lakeside site preserves ‘phantom hearths’ recognized by discrete clusters of burnt flint, wood, and

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other plant materials (Alperson-Afil 2008).9 There is also evidence of different kinds of activities taking place around and away from the hearths (Alperson-Afil et al. 2009). Crab, fish, and nuts were eaten at the hearths with the nuts roasted first for ease of cracking on stone anvils. Stone tools were resharpened around the fire, including handaxes, and the variety of discarded light-duty tools hints at a range of other food-preparing and tool-maintenance tasks. The messy and potentially dangerous activity of stone knapping took place at a safe distance from the hearths. The processing and discard of fish also took place away from the heat of the fire. The Gesher evidence highlights the importance of hearths as social magnets—places where people were drawn to carry out basic tasks and interact—but these ghost hearths also highlight the two problems that hamper our efforts to document when and where fire was invented. First, fire is a destructive process that leaves relatively little to be preserved, especially in open settings. Secondly, there are natural sources of fire that can mimic human fire-use by creating scatters of charcoal, burnt bone, and fire-damaged stone tools (James 1989). Lightning strikes in the monsoonal tropics are a recognized cause of bush fires that sweep across landscapes leaving scatters of ash, charcoal, charred animals, and setting trees alight. A burning tree stump might leave behind a roughly circular patch of baked sediment that resembles a hearth, and if that stump just happens to be near a scatter of artefacts then there is the risk of a mistaken association. Archaeologists now have at their disposal a range of analytical tools that can help distinguish between natural and cultural fire-making (e.g. Bellomo 1994, Karkanas et al. 2007), and their application has revealed what appears to be the earliest 9 Ash is generally poorly preserved in most archaeological sites, especially those in open settings. Caves are more conducive settings for its preservation and recently the claim has been made that traces of ash exist as early as about 1.7 million years at Wonderwerk Cave, South Africa (Beaumont 2011). The scientific evidence in support of this claim has yet to be published in detail, but there is clear evidence for burning later at 1 million years ago in an Acheulean level (Berna et al. 2012). Burned bone and plant remains show that temperatures were reached of up to 700ºC and that the fuel was primarily grass, brush, and leaves rather than wood. There are no recognizable hearths and given the rapidity at which grass and leaves burn, the fires would have required constant stoking. Perhaps what we are seeing are the remains of bedding that caught fire rather than the use of these materials as fuels. For the time being, the consensus remains that Gesher provides the most convincing case for the controlled use of fire.

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deliberate fire-making 1.6 million years ago at Koobi Fora, Kenya. Others remain sceptical that this is evidence of controlled fire use as opposed to the opportunistic use of a natural source such as a smouldering stump (Roebrooks and Villa 2011). Gesher remains, for the moment, the earliest accepted evidence of the controlled use of fire. Maybe it is a coincidence that it dates to the start of the Transition with the onset of prolonged glacial cycles. There is another gap in the record before we see fire again being used regularly and that occurs very widely about 400,000–300,000 years ago in Europe, Asia, and Africa (see Dennell 2009, Gowlett 2010, and Roebrooks and Villa 2011 for summaries of the data). This correlates roughly with an increase in the extremes of glacial cold seen in the ice-core records following the end of a particularly long interglacial around 430,000 years ago (MIS 11). The expansion of human populations across Eurasia during this warm phase came to a halt with the onset of a new glacial cycle. The control of fire would have been of particular importance to communities living in more northerly latitudes, but as we know there is much more on offer with fire than just warmth. The mid-latitude site of Qesem Cave in the Levant gives us a glimpse into the social importance of hearths as places for the sharing of meat 400,000 years ago. The occupants squeezed into its narrow confines to cook the meat and marrow-rich legs of deer. In such a space it would be hard to resist the social pressure to share, and the charring patterns on the bones reveal what looks to be the planned distribution of meat between the hearths (Stiner et al. 2011: 229). If this was the case, then we may be looking at the best indirect evidence available for a social group bonded through sharing and the cooperative hunting of large game. We cannot say with certainty that they had an extended childhood with all that implies about cooperative breeding and social learning, but chances are that they did. These makers of fire (and blades) would have been the large-brained descendants of H. heidelbergensis, and that means the sharing of childrearing was a necessity for group survival. Beyond Qesem Cave there is evidence from Middle Pleistocene sites in Africa (Barham and Mitchell 2008), Asia (see Dennell 2009), and Europe (Villa 2009) for the systematic hunting of large game, but rarely do we get such an insight into the social lives of the time.

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Not as Easy as Rubbing Two Sticks Together In thinking about the many benefits of fire we have yet to consider how it is made and its cognitive demands, in other words what realms of knowledge and practical skills are needed to make and maintain a fire? How might these have contributed to the development of combinatorial technology? As a Boy Scout I never managed to make a fire using two sticks (nor did the rest of the troop), and even with the aid of the more advanced bow drill at best I generated heat and a wisp of smoke. Much later in life on my first visit to Zambia—where I have been working since—I came to appreciate what I was doing wrong all those years before. I used the wrong kinds of wood, did not prepare a notch in the ‘hearth board’, and did not prepare some tinder to bring the glowing ‘char’ to light. All this was revealed on a walk through the Zambian woods. I asked our guide whether he knew how to make fire the traditional way and within minutes he came back with two pieces of wood, one soft (fig tree), the other hard, plus some dry grass. Using a pocket knife he trimmed the thin branch of hardwood into a

Fig. 4.15 (a) The use of a spindle rotated between the sides of the hands to generate enough heat by friction to develop a smouldering char with which tinder can be lit; (b) close-up of the charred hearth board.

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straight stick. The piece of fig tree, which was broad and flat, was then prepared to receive the stick. A shallow hole was cut and next to it a v-shaped notch on the edge. One end of the drilling stick (‘spindle’) was placed in the hole, and then holding the spindle between his palms he began to rotate it starting at the top and working down to the base, pushing hard all the time (Fig. 4.15). He repeated this downwards motion rapidly and as the spindle spun it widened the hole and generated sawdust that began to fill the notch. In less than a minute of vigorous spinning a wisp of smoke rose from the hearth board and the sawdust glowed. The glowing sawdust (known as char, or the coal) was turned into a bundle of dry grass (tinder) that had been placed there at the start. With a puff of breath the grass burst into flame. The speed of the process from start to finish was impressive. In no more than five minutes a fire was made from just wood, grass, and the help of a knife.

Social Learning and Cooperation around the Hearth So it seems that fire-making is quite simple, except for some Boy Scouts, and all you need is the knowledge of which woods and tinder to use, how to shape the components, how to generate enough friction, and then when to administer a little extra air to coax an ember into life. That simplicity, of course, is deceptive because it reflects a well-learned routine and a good deal of folk physics too. Fuel, heat, and oxygen are the foundations of the combustion process and obviously need to be combined in sequence and in the right quantities to produce a flame. To sustain a fire requires the addition of kindling and then larger pieces of wood. Some woods burn longer than others and by adding large logs to an open fire it can be kept burning and smouldering through the night. In the morning, the glowing embers can be turned quickly into a full blaze with the addition of tinder and judicious blowing. Once you understand the process of firemaking and maintenance, it can be repeated over and over, and there is often little need to make a fire from scratch unless you are travelling long distances. Our Zambian fire-maker learned his craft from his father, and the learning started when he was a boy. His father in turn learned it from his father and so on back through a long line of vertical transmission over generations. (I do not know whether women learn fire-making from their mothers or fathers in this particular society, the Tonga, but

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they too have this essential knowledge.) In traditional Tonga villages fires were always burning and glowing coals were transported (between potsherds) around villages and on short trips away (Smith and Dale 1968). The maintenance of fires requires the collecting of firewood on a regular basis, and in the case of the Tonga this is largely the responsibility of women. A more general point can be made about the maintenance of fires and that is they involve planning, and, potentially, a division of labour, or at least the taking of turns. This cooperative element of communal fire-making may have existed as early as 400,000 years ago in northwest Europe (Preece et al. 2006). To this speculation we can add another: children would have been a part of the hearth-based community, and from this vantage point they observed their future social roles and the integral place of this and other technologies in their lives.

REGIONAL VARIATIONS ON THE THEME OF FIRE BY FRICTION Returning to the present, the physical skills involved in fire-making come with practice and in the case of Zambia they are rapidly being lost as matches have replaced the friction method. There is still a residual understanding of which woods are best and how the process works even if the details are fuzzy. Soon the knowledge and skill of fire-making will be a relict of a bygone age, but there is fortunately a large body of ethnographic information and experimental data available for reconstructing the basic methods of fire-making. In Africa the spindle and hearth board method was widespread across the continent, but in the tropical rainforest and around its margins another friction method could be found (Lagercrantz 1954). The ‘fire plough’ involves either cutting a trough into the hearth board or creating the trough by the act of pushing a fire stick along the hearth board to generate heat and an ember. This variant of the friction method might be a particularly good design in the damp conditions of the region or a cultural tradition with no functional advantage. This comparative efficiency of the spindle versus plough techniques can be tested, but there is little doubt about the

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effectiveness of the compound drill as a means of generating heat with minimum effort. This type comes in two forms, the more complex of which uses the spindle and hearth board, but instead of the spinning generated between the hands the hard work is done by a cord or string wrapped around the spindle and attached to either end of a wooden bow. The bow keeps the cord taught and the user holds the bow-spindle alignment in one hand and pushes down on the top of the spindle with the other, which is protected by a cap or pommel of wood, stone, or some other hard material. Alternatively, this can be a one-person tool with the spindle cap held in the mouth (Hough 1890). A simpler method involves wrapping a cord around the spindle, which is then pulled side to side by one person whilst another holds the spindle in place. Fire-making can be a sociable activity, and it is easy to imagine a simple apprenticeship involving a young assistant learning the craft from helping a more experienced adult. As well as generating heat by drilling and pushing there is another effective variant, the fire saw. In the Gibson Desert of Australia, the making and use of a fire saw is a team effort involving three people. A branch is split and put on the ground with wedges inserted to hold the crack open and help anchor the wood to the ground. As one person stands astride the branch another fills the split with tinder (dry kangaroo dung) and then begins the sawing motion between the outstretched legs using a wooden board designed to throw spears (Gould 1969: 122–3). The third pair of hands now comes into play to hold the other end of the ‘saw’. In island southeast Asia there are a variety of fire-making techniques involving the scraping of the tough outer surface of bamboo with a stone or other hard material to create sparks. Where wood is scarce, such as in the Arctic or Patagonia, then stone on stone ‘strikea-lights’ offer a means of generating a shower of hot sparks, but the right kind of stone needs to be used, one which contains iron and sulphur such as pyrite or marcasite (Hough 1890). Strike-a-lights are also highly portable with the stones and tinder easily carried in a pouch. The stone also has the advantage over wood of not being affected by damp, but the tinder needs to be kept dry. It is not surprising then that strike-a-lights have a wide distribution beyond Arctic and sub-arctic settings including Australia, Tasmania, and Melanesia (Gott 2002; Roussel and Boutié 2006). They are still used

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on the southeast Asian island of Flores, but today steel hacksaw blades provide the sparks (Brumm 2006).

A Disappointing Archaeological Record The ingenuity shown in innovating different ways of fire-making to suit local materials and conditions reflects the central importance of fire in the lives of so-called traditional communities. Unfortunately, the archaeological record provides little evidence for their antiquity, as organic fire boards are unlikely to survive long and stones with grooves made for striking sparks might easily be interpreted as having been used for other purposes. Occasionally, fire-making tools survive as in the dry caves of south Texas where spindles and hearth boards are found (hard and soft woods respectively) along with tools used to maintain fires (Shafer 1986: 114). These include tongs made of split sticks bound by cord at the handle end and a fire stick to rake the coals. A fire stick, like that used in Australia for controlling the growth of vegetation, can be carried on short trips from camp with its smouldering end providing a ready source of heat for lighting a fire. The capacity to control fire long pre-dates the archaeological evidence for any of the friction-based methods, but we have to assume that in areas where natural sources of fire were rare or unavailable (e.g. volcanic eruptions, lightning strikes. or spontaneous combustion of organic matter in caves), then friction was the only means of generating sufficient heat to ignite tinder. These friction tools are also very portable, or if the right materials are available then they can be made on the move. Alternatively live coals can be carried wrapped in leaves, bark, shell, or similar materials that are slow to burn, but these are unlikely to survive or their use be identified with certainty in the archaeological record.

Thinking about Fire The making of fire is an integrative technology in that its making involves a hierarchical sequence of steps to generate combustion. If they are not followed then the goal will not be achieved. It also integrates different spheres of knowledge, mostly to do with organic materials, and a kind of folk physics that is not needed to make stone tools. The generation of heat is essential to fire-making, and yet this ingredient is ephemeral and invisible until the first wisps of smoke

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rise from the hearth board. The understanding of cause and effect is based on a dramatic transformation from one physical state to another: friction ! heat ! tinder = combustion. Once lit, a fire will also need to be fuelled, and that anticipation requires an awareness of a future state based on an understanding of the process of combustion. Making a fire is not like the shaping of stone by force in which the mechanical properties of the stone and hammer remain unchanged. It is an additive process more akin to hafting; something new is created from multiple parts and it has a property that differs from its components. Fire-making appears to be cognitively demanding, and in the absence of neural-imaging data we can only speculate that it engages similar networks to those used to plan and make hand-axes. We can also expect constructive memory to be involved given the separation of tasks in time and space. The fact that some of the earliest evidence of hafting is associated with the use of fire (see Chapter 5) adds support to its role as a precursor to the combinatorial principle.

HAFTING IN THE MAKING The Middle Pleistocene Transition ushered in dramatic changes to the earth’s climate cycles and in doing so affected the lives of humans everywhere. The long glacial cycles changed the kinds and abundance of basic resources as the landscape adjusted to drier cooler conditions. Human populations were fragmented and some were isolated in refugia or core areas, and then released with the rapid shift to warmer interglacial conditions. Short-lived warming and cooling events repeatedly disrupted this longer-term pattern. Variability selection operated on the more human scale of seasons and years as communities responded to immediate stresses. Those with the ability to respond quickly and imaginatively to widely fluctuating environments stood a chance of surviving this climate-driven roller-coaster ride. When combined with social learning theory, variability selection also points to the kinds of environments that would favour not just the capacity to innovate, but also the social conditions that supported learning across the generations. Core areas existed on each continent where human populations persisted during the harshest of conditions. Elsewhere, disruptions of habitats were, to

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put it mildly, less conducive to cumulative cultural change because they reduced population size, density, and the extent of social interaction. Small and isolated communities risked losing the expertise of elders and so the capacity to develop innovative solutions to new problems. Those problems might be posed by climate change or arise from competition with other humans. The archaeological record of the Middle Pleistocene is too coarse for us to make direct correlations between particular climate-driven stresses and technological innovations in one core area or another. We can say that after 900,000 years ago three integrative technologies did emerge, and in a very general way they are the collective responses to this new harsher world of colder and more unpredictable environments. If the climate Transition drove innovation indirectly it did so using the vehicle of Acheulean technology. By that I don’t mean just hand-axes and cleavers, but the full suite of technical knowledge of working organic materials using a variety of large and small tools as well as an understanding of fire. Bone and wood-working technologies were already well-established parts of the technological repertoire, but the shaping of hand-axes using soft hammers brought the technologies together to form longer sequences of planning and action than before. That extended ability was built on solid neural and cognitive foundations of networks and differing kinds of memories to achieve imagined goals. Prepared-core technology, the controlled use of fire, and the making of blades all probably piggybacked on these foundations, but for now that remains a matter of guesswork. When it comes to anticipating where hafting might have been invented we can exclude most of east and southeast Asia. Large parts of this region lacked two of the three precursors to hafting. A sustained tradition of hand-axe making was absent and without it there would be no prepared-core technology. The controlled use of fire was present, but this largely organic technology on its own was not the likely inspiration for hafting. There may have been early complex combinations of bamboo, rattan, and shell with stone, but these remain to be discovered. The evidence we do have points to multiple centres of independent innovation of prepared-core technology, including blade-making, in Africa, south and southwest Asia, as well as Europe. It is to these areas we now turn in the search for the earliest evidence of hafting.

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5 The Invention of Hafting At long last we come to the actual invention of hafting. We have identified its precursors in the integrative technologies of the Acheulean and we have seen that by about 500,000 years ago the cognitive, anatomical, and social foundations were more or less in place to enable its inventor to be creative. So, we must now be close to answering the basic questions of when and where hafting was invented, to speculate, in an informed way, on how and why it came about. Sadly, that is not the case. We still have more detective work to do. The organic components of hafted tools rarely survive and we must rely on indirect evidence of varying quality to piece together even the most general patterns of time and place. Because the evidence is so rare, we need to understand exactly what is involved in making a hafted tool so that we can recognize even the slightest traces that might survive. We have also claimed repeatedly that hafting is a cognitively demanding technology and now the time has come to substantiate that claim with evidence gleaned from ethnographic and experimental sources. This will give us the background we need to develop a framework for assessing the quality of the archaeological evidence. Only then can we systematically review the record for the Middle Pleistocene. By the end of this long process we will have a clearer view of the limitations of the record itself, of our methods of analysis, and of our interpretive biases. We will, at last, be in a position to consider where hafting might have been invented and how it spread—a discussion developed further in Chapter 6—as well as potential stimuli that spurred the inventive process.

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Next time you reach for a carving knife or potato peeler have a look at its construction. Chances are that the tool is made of at least two parts—the handle plus the cutting edge. Then, consider how the parts are attached. If the knife has a wooden handle, then it is probably glued and riveted to the cutting edge. If the handle is plastic, then it is probably moulded around the metal, or it may be riveted. The knife, of course, is designed to cut and be used in a slicing motion (one direction) or in a sawing motion (back and forth). A soft flexible cutting edge would be pretty much useless and the handle also needs to give some resistance to the forces imparted while holding the blade tight. The forces are also transmitted from the handle to the hand, arm, and upper body, which means the design of this tool must meet several physical needs at once, some more obvious than others. Imagine that your knife had a handle that was the same shape, size, and weight as a clay brick—it would be awkward and tiring to hold. Now, consider the humble potato peeler. It too has a job to do and in this case the cutting motion skims the surface of the vegetable. The hand holding the potato is also actively engaged, and you may also be using your thumb on your handle hand to help guide and push the potato skin through the slot in the cutting edge. The forces are directed away from or perpendicular to the handle and into the hand and arm. A brick-shaped handle would be useless for this tool and if the cutting edge was not perforated with a long slit parallel to the edge, then the tool would scrape rather than peel. Now imagine a spade with its cleaver-like edge set perpendicular to the shaft and handle. What is the direction of force, how is the body engaged, and what are the properties needed to make an effective tool? These questions can be applied to all the hafted objects in our homes and workplaces, but we rarely consider them unless something goes wrong and needs repairing. Someone else has already worked through the engineering issues, so that we just need to know which tool is appropriate for the job. As craft specialization has grown and the complexity of tools has increased, fewer individuals have had the knowledge, skills, or time to be able to make everything they use. The separation of the knowledge of tool manufacture from its use is a consequence of cumulative cultural evolution, and one that has unintentionally increased our dependence on others (engineers,

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manufacturers, retailers, and advertisers) to meet real and perceived needs. If for some reason you wanted to make your own smartphone from scratch, it would be impracticable if not impossible; there are simply too many layers of knowledge to master, let alone the time and costs involved. If, on the other hand, you lived 400,000 years ago, then it would be both practicable and feasible to learn the technologies used by your community. If a division of labour existed, then there could have been some specifically female and male tools, but also much shared practical knowledge connected with everyday tasks. Those tasks would involve the actions of cutting, scraping, sawing, adzing, piercing, and digging. This limited range of activities is so useful, if not essential, that we find them among recent hunter-gatherers and other preindustrial societies across a broad range of habitats from deserts to tundra (Oswalt 1976). (Of course, we still use and even rely on an adze or axe, though few of us probably need one to get by.) We can assume too that in the Middle Pleistocene humans structured many of their technologies around these basic activities. In which case, there were—as there are now—just a small number of hafting options that could work with the mechanical loadings and stresses generated by each action (Rots 2010). Given that these have remained constant, we can discuss with some confidence the folk physics (or more properly, the folk materials science) needed to make the earliest hafted tools as well as later ones. There will undoubtedly be some variations of hafting that are lost forever, but we can still generate an understanding of the mechanical principles that were understood by the designers of the earliest hafted tools.

The Folk Physics of Hafted Tools Starting with the knife, we will identify the stresses that affect the components during use and which are incorporated into the design of the handle and haft (Fig. 5.1). The distinction made between handle and haft recognizes the handle’s role as the support to which the working edge is attached and the haft as the form of the attachment. Some archaeologists refer to both components together as the haft, but to appreciate the level of understanding needed to make a hafted tool we need to consider each component as part of a set of engineering challenges. These had to be solved before the tool would work

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Fig. 5.1 Loadings and stresses applied to the joint of a knife (a), scraper (b), adze (c), and piercer (d) during use. The heavy arrows show the primary direction of use and the smaller arrows indicate the resulting forces affecting the joint. The design of these tools involves incorporating an understanding of these engineering principles into each component, but especially at the joint which is the weakest part of the tool.

effectively. The resulting design reflects a combination of practical experience with a general understanding of cause and effect. We learn from experience which materials and shapes work best for a particular job and how far we can bend, push, or pull them before they break or fail. That is practical engineering. The inventors of hafted tools used this folk understanding of the strength of materials to adjust each component to improve the effectiveness and durability of the whole tool. In contemporary engineering terms they understood the difference between compression, tension, and shear stresses, and how these were generated during tool use. (Compressive forces squeeze a material, whereas tension pulls it apart, and shear arises as opposing forces slide past each other in parallel.) They would have learned quickly that the haft joint was probably the weakest part of the tool, as it experienced the most stresses and strains. When you use a garden rake the join (haft) between the tines and the shaft experiences a greater loading of force than the shaft itself. This might seem obvious, but the maker of the rake had to incorporate this knowledge into the tool design and selection of materials. The

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modern rake embodies a long history of accumulated learning from individual trial and error, and social learning by imitation and perhaps instruction. Over time small improvements have been made to the various parts to make the tool more effective as a working whole, but the basic design has probably changed very little over time. Likewise, the design of the hafted knife, scraper, adze, and spear are broadly similar whether made by hunter-gatherers, farmers, or in factories. Long craft experience has honed them into efficient forms with relatively little room for improvement except in the materials used. There is plenty of scope still for cultural expression in the style of the handles, hafts, and inserts.

Cutting The apparently simple hafted knife with a stone blade embodies in its design much of the folk knowledge of the mechanical stresses that need to be considered in the design of hafts generally. In this case, imagine you have a long carving knife and a joint of beef on the bone to be cut into thin slices. First, downward pressure is applied through the handle via the haft into the blade, and without this pressure the tool will not cut. At the same time the blade is being pulled roughly horizontally (or pushed if a sawing action is used) along its long axis. The resistance of the meat also imparts a loading into the blade, haft, and handle. If the blade gets unintentionally stuck into the bone, you the carver might just give the handle a twist to free the cutting edge. That twist imparts opposed forces perpendicular to the long axis. The haft needs to hold the blade securely in response to each of these competing loadings with their differing stresses. As a knife is pushed into the meat there is compression of the haft and handle. Depending on the type of haft (below), compression may be needed to hold the blade in the haft and that is the role of the binding. As the knife is drawn back there is tensile stress imparted as the haft handle resists the pull of the blade. The twist of the knife imparts opposing or shear forces on the blade and haft. If the blade lacks the strength to cope with the shear then it might snap, and if the haft is not designed with shear in mind then the blade might become loose and will need re-hafting. The main movement of the knife is the back and forth of cutting and so we should expect hafts to be designed accordingly, with torsion or twisting a secondary concern.

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The choice of knife blade also involves consideration of the stresses imparted. Obviously an edge needs to be sharp to cut, but a thin edge (angle of 20º) is likely to break on use and replication experiments have shown that edge angles in the 35º–45º range are a good compromise between efficiency and resilience when cutting soft materials like our joint of beef (Wilmsen 1974: 91). The brittleness of the stone also needs to be factored into the equation as some materials, such as obsidian (volcanic glass), are less durable than crypto-crystalline flint-like rocks.

Adzing This tool is designed to be used with the cutting edge perpendicular to the long axis of the shaft (a vertical setting would make an axe or hatchet). An adze blade is typically set at an acute or right angle to the long axis of the handle, and this arrangement is also found on hoes. These versatile tools can be used for wood-working, butchery, or for scraping, but are not designed for use in a knife-like cutting or sawing motion (Clark 1958). The adzing motion imparts a force into the cutting edge that is perpendicular (transverse loading force) to the long axis of the handle. The resulting stress is compressive as the bit or working edge pushes into the haft and against the handle. (The force and stress would be similar in an axe.) There is a clear need for a resistant haft with high-impact strength, and a good strong haft should also allow for some torsion. The choice of stone and angle of the chopping/slicing edge must also match the stresses imposed. Coarse-grained metamorphic (e.g. quartzite) and igneous rocks (e.g. rhyolite) are often used for their durability. Where stone adze blades are still made, artisans grind or peck the blade (or bit) to form a robust edge angle (between 50º and 75º) (Blackwood 1950; Stout 2002), and the smooth surfaces reduce friction on contact, making for a cleaner cut compared with the irregularities of a knapped edge.

Scraping There is a common assumption that scrapers are just used for defleshing skins as part of hide preparation, but they can be used on wood, soft stone, bone, and antler. They are versatile tools. The scraping motion involves pressing down and dragging across a surface, creating transverse loadings and compressive stress on the haft

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Fig. 5.2 Basic types of haft: (a) juxtaposed, (b) inclusion, (c) cleft, (d) composite, (e) applied, (f) clamp, and (g) a variant of the juxtaposed haft (see Fig. 5.3). The ‘sandwich’ haft with rivets is relatively uncommon and is not illustrated. (The applied haft is drawn from artefact 47.1.a and the clamp haft is drawn from artefact 56.26.710, both in the collections of the National Museums Liverpool.)

in particular (Fig. 5.1b). Depending on the haft arrangement, there may also be some loading applied to the long axis of the handle, which will also be a compressive stress. Unlike the adze, the force is not applied suddenly, but evenly and continuously. The angle of the edge used to prepare a hide should not be too sharp (acute) or it will cut the skin, and should be robust enough to resist the transverse loading caused by the dragging motion (about 50º) (Tringham et al. 1974; Wilmsen 1974: 91). Scraping harder materials may require an even larger edge angle with its greater concentration of mass.

Piercing This category encompasses a range of tools designed to create a hole in soft or hard materials. The hole might be the result of pressure

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applied in a drill-like action (torsion loading with shear stress), or by force directed down the long axis (axial loading with compressive stress), which includes the hunting spear with its hafted tip (see Fig. 5.1d). The folk physics involved in piercing will be task specific and as with the other three categories of movement the artisan will need to consider the haft design, the properties of the insert and its edge angles in relation to the stresses on the tool as a whole.

A TYPOLOGY OF HAFTS The haft is typically the weakest part of a hafted tool because it joins the working edge to the handle, and joins are inevitably not as strong as a one-piece handle. The joint is also the focal point of the loadings and stresses and so will need to be designed with these in mind. There are four main types of hafts found in the ethnographic record and on rare surviving hafted tools from later prehistory. These are inclusion, cleft, juxtaposed, and composite hafts (see Fig. 5.2).1 There are an additional three haft types—applied, sandwich, and clamp—that are less common and these are discussed separately below. Each haft type has its set of tolerances in relation to the angle of use and the hardness of the materials being worked (Rots et al. 2006). The inclusion haft is simply a hole cut into the handle, into which the bit is inserted. Some raw materials, such as long bones with a marrow cavity, lend themselves to this kind of haft (Rots 2010). Appearances can be deceptive, as the inclusion haft involves a bit more thought than just sticking a stone into a bone. If the hole is too tight, then the bit has no leeway to move during use and chances are it will snap (Barham 2010). If it is too wide, then the bit will be too loose to be effective, and once the hole is cut it cannot be made narrower. The user would soon learn the lesson of making an incorrect size of hole, and one response would be to standardize the size of the bit to match the haft. Standardization might include shaping the bit so it fits snugly, and tapered stems do occur in the later archaeological record. Another option for coping with a loose fit is to pack the hole with wedges, but this is 1 The term ‘adhesive’ as used here includes glues, but I am aware that some analysts do distinguish between the two.

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a temporary solution. An adhesive combined with wedges would give added durability, but that option brings with it an extra layer of planning and takes us into another realm of folk chemistry. The inclusion haft withstands compressive stress directed into the long axis of the combined tool. We see this arrangement today in chisels, and in the haft of a ball-point pen and pencil. Screwdrivers are also usually hafted this way and designed to withstand torsion. The screw is a relatively recent invention (see Rybczynski 2000), and if we are to imagine an analogous twisting action in an early tool then it is likely to be in the act of drilling. Modern screwdrivers (and chisels) made with a wooden handle are often finished with a metal cap or ring over the join (ferrule) to prevent splitting and to help hold the bit in place. Before the invention of metal joints, the choice of haft would have to withstand torsion and minimize the snapping of the inserted bit. An inclusion haft offers less room for play than a cleft haft and increases the likelihood that a stone bit will break or the haft will split. The cleft haft is also deceptively simple, and one of the most versatile. Almost any action can be supported (cutting, scraping, piercing, sawing, and chopping) so long as the components of the haft are designed to work well together in response to particular stresses. The bit is inserted into a v-shaped split, and unlike with the inclusion haft, friction alone will not hold the working edge in place.

BINDERS AND ADHESIVES Integral to the success of the cleft haft is the integration of at least one other material to secure the bit, which will be a binder, adhesive, or a combination of the two. Bindings are typically flexible materials that can be wrapped tightly around the join to compress the split so it holds the insert with minimal movement. Depending on the kinds of plant or animal tissues used, the bindings will have differing properties of flexibility, durability, and compressive strength. They will also involve different steps in their manufacture, such as the soaking of intestines, rawhide, or sinews, so that as they dry they contract and form a tight join between the handle and the bit. If needed, the join can be easily undone by soaking it in water, which allows the bit to be

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replaced or resharpened. Fresh rawhide seems to be the strongest material in terms of its ability to hold fast against a range of stresses (K. Lee, personal communication). Bindings made from plants also involve processing to turn their fibres into cordage. A wide range of sources can be used including bark (inner, outer), roots, stems, and leaves (Westcott 1999). The extent of processing depends on the properties of the plant fibres and may involve simple stripping into useable lengths or pounding then twisting fibres into a cord. Animal (and human) hair can also be twisted into cordage, and twisting animal bindings also seems to increase the strength of hold. The kinds of binders used will obviously depend on what the local environment offers and of course on traditions passed from one generation to the next. As with the design of the haft, the choice of binder needs to match the stresses to be experienced by the tool. The same principle applies to the use of adhesives. Adhesives hold surfaces together and in a haft they bond the bit to the inner surfaces of the haft. The bond can be extremely strong and able to withstand large stresses—like a modern synthetic ‘superglue’—or designed just to hold an object in place, especially one not subject to substantial loads (Ebnesajjad 2009).2 Adhesives have differing resistance to temperature and moisture, and because they are used in small quantities and spread thinly they add relatively little weight to a tool. If aerodynamic properties are important, then adhesives provide a smoother surface than bindings or fasteners. Before the invention of synthetic compounds, adhesives were made from animal and plant products. The proteins and fats in skin, cartilage, and bones have traditionally been processed in the making of glues from animals (e.g. fish and cattle). These adhesives vary in their stability as they dry, with hide glues changing from soft to brittle (Silsby 1999). Being soluble in water is also an advantage of hide glue when it comes to replacing or sharpening the bit, as it can be easily removed from the haft.

There is a fifth type of haft joint, referred to as female (Rots 2010), in which the handle is inserted into a hole in the bit itself. This arrangement is seen in the later prehistoric record with the use of groundstone bits that are drilled, and more common with the casting of metal working edges (bits) to have an integral socket. Modern steel-tipped hammers, hatchets, axes, and picks are usually hafted this way with the join made tight by chocks or splints driven into the hole. 2

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The Folk Chemistry of Adhesives Plant-based adhesives are made from the processing of bark, resins, and sap, typically by prolonged heating which drives off volatile compounds and concentrates the liquid into a more viscous material. A good degree of folk chemistry was involved in this distillation process, as has been shown by the geochemical analysis of historic and prehistoric production methods combined with practical replication experiments. We have a growing database of historical, archaeological, experimental, and laboratory-based information with which to reconstruct the expertise needed to make adhesives from bark and sap (e.g. Beck et al. 1999; Callahan 1999; Sauter et al. 2000, Hjulström et al. 2006; Wadley et al. 2009; Richardson 2011). In northern and central Europe, birch and pine bark has long been used to manufacture tar which was until relatively recently used for waterproofing (e.g. ships, containers, and clothing) and as a lubricant. It also has adhesive properties that make it very useful in hafting. The making of tar requires considerable pyrotechnical knowledge that involves extracting the oil and then transforming it into a sticky substance by the use of heat in an oxygen-controlled environment. The heat combined with a reducing atmosphere concentrates the carbon in the bark until it precipitates as a liquid (Beck et al. 1999). This process known as ‘dry distillation’ is only successful within a narrow temperature range of 340º–370º C: too low and no tar is produced, too high and the tar is destroyed (Koller et al. 2001). The heat can be generated either within an enclosed space, such as a pit, or applied externally to containers, such as pots. In Europe, the technology of dry distillation developed as the demand for tar grew. The early Medieval funnel-shaped pit gave way to clay pots and then double-walled stone ovens for industrialscale production (Beck et al. 1999; Hjulström et al. 2006). Pots and elaborate ovens were not an option for the tar-markers of the Middle Pleistocene. They would have used earth pits, and a recent experiment shows how it might have been done (Pawlik and Thissen 2011: 1702). A length of birch bark was rolled into a cigar-shaped bundle, lit at one end, then placed in a narrow pit in the ground which was then covered. As the bark smouldered it consumed the oxygen in the pit, creating the reducing conditions needed to concentrate the oil. A receptacle of some kind is needed to collect the drops of hot tar,

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otherwise they disappear into the soil. In this case, a flat or slightly concave stone placed at the base of the pit caught the drops which were then ready to use for hafting. This may seem like a simple process, and it is, once learned, but its invention required an existing knowledge of fire-making plus awareness that birch (or pine or spruce) bark could be transformed into something new and useful. That knowledge may have come from collecting resin from trees and noting the link between the dripping sap and a cut in the bark, or from the experience of whittling fresh resinous woods, from observing that bark found within the ashes of a hearth exuded a sticky substance. Regardless of the source of the inspiration, a high level of intellectual development is embedded in the invention of dry distillation. The process involves a multilayered understanding of cause and effect, with the result being the first synthesized material in the history of technology. There is a somewhat simpler route to making tar and that is to collect it in its natural state known as bitumen or natural asphalt. Sources of bitumen, however, are rare and its early users still had to heat the material to extract a useable liquid (Böeda et al. 2008). The reduction of sap into an adhesive only involves boiling with no need for an initial distillation (K. Lee, personal communication). Across Eurasia the sap or pitch of conifers such as pine and spruce provided a widespread source of adhesives. The equivalent material in the semi-arid regions of Africa, western and south Asia, was acacia tree gum, which also needs preparation using fire. Along the Mediterranean, several species of pistachio tree (genus Pistacia) are known as a source of a resin that can be used as an adhesive (Modugno et al. 2006). Other plant materials were undoubtedly used depending on local availability that involved other patterns of preparation. In northern Zambia on the border with Tanzania there are anecdotal reports of a gum made from the chewed leaves of a species of gardenia that is waterproof and dries into a hard glue suitable for hafting stone (Clark 1958: 151). When still warm, plant adhesives remain pliable and they can be applied to hafts and their inserts. Once dry they can also be reheated to loosen the haft to remove the insert. This reversibility is important as it extends the life of the handle and haft, especially as these components can involve a considerable investment of time in their making. Better to replace the working edge as it dulls or breaks rather than the whole tool. Combinatorial technology gives its users the

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advantage of durability and efficiency of raw-material use over time. Returning to the hafting process, as the glue (plant and animal) cools it runs the risk of cracking. Cracks weaken the adhesive bond and increase the likelihood that the join will fail under stress. Experimental archaeologists have learned that the addition of a finely ground material to the still-warm mix will reduce the spread of cracks and help keep it pliable (K. Lee, personal communication). A wide range of additives will do the trick including powdered charcoal, ochre, shell, ash, grass, sand, stone dust, hair, blood, and even dry dung (Kamminga 1982; Callahan 1999). Beeswax also helps to prevent cracking and to retain pliability. The use of these additives marks yet another strand of folk chemistry associated with hafting and which has its roots in the Palaeolithic (Wadley et al. 2009). Birch tar, on the other hand, does not crack as it cools and so no additives are needed (Richardson 2011).

An Essential Bind Depending on the kind of haft/handle arrangement an adhesive might not be needed, but almost always an adhesive needs the added compression of a binding to be effective, with one notable exception. Spinifex grass (Triodia spp.) grows in the arid interior of Australia, and contains a resin that when processed makes a strong glue that can be used as a haft in its own right to join a stone bit to a handle. It can even withstand the impact of adzing (Kamminga 1982). Spinifex aside, tars and pitches act more as fillers in a haft rather than as glues. The filler does what the name suggests; it occupies the space between the haft and the insert and helps hold it in place as the binding compresses the materials into a tight join. Ongoing experiments in the engineering department at the University of Liverpool have shown that acacia glue has a poor resistance to pulling (tensile) and twisting (torsion) loading when used in a cleft haft. The compressive force of the binding is what really holds the bit in place. Filler can also act as a shock absorber that allows for some movement of the bit under stress, which may prevent the haft from breaking. Binders are used in the remaining types of hafts, with adhesives playing a supporting role as well. In the juxtaposed haft (Fig. 5.2a), a binder is essential with adhesive an option depending on the kind of binding material used. The working bit is lashed to a flat platform

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From Hand to Handle

with bindings, though an adhesive can be added as a shock absorber (and applied to the bindings to help hold them in place). Or, in the case of a stone insert, it can be wrapped in leather to prevent it cutting the binding and to give it greater resistance as it sits on the platform (Rots 2010: Fig. 2.2). The juxtaposed haft is designed to withstand strong compressive forces directed into the tool. A backstop can be cut into the haft platform to give added resistance, but is not essential depending on the strength of the bindings. The bit can be hafted at one end of the long axis of a handle, or, in the case of the adze, at a sharp (acute) angle to the handle. This angled join is a potential weak point in the haft. Its construction needs careful planning, and one option supported by practical experimentation is to make an all-inone handle and haft from a fork in a tree branch (Price 1999). The forked branch will be a naturally strong and resilient joint. As an aside, a degree of imagination is needed to see in the branch a solution to this engineering problem. Another solution is to attach an angled haft to the handle using bindings, adhesives, and carpentry skills to fashion an effective joint (Ebnesajjad 2009). Either option involves an added dimension of planning not needed when using inclusion and cleft hafts. A variant of the juxtaposed haft is found in collections of clubs, maces, and mauls from North America. In this arrangement, a heavy stone is attached to the handle by bindings alone, with the bit not necessarily sitting on a supporting platform (Fig. 5.3). The roundheaded clubs of the Plains, for example, are made with the stone ball wrapped entirely in hide, which is then secured to the handle with sinew. Another variant is found in environments where wood is scarce, as in the Arctic, where tools to be used in a high-impact action (adzes, axes, hatchets, and picks) are made from bone and ivory tusks (from narwhals and walruses). The hafting arrangement differs as a result, with the acute angle formed by lashing the working bit to a shaped handle (juxtaposed joint) (Fig. 5.4). In the illustrated piece, a hole is cut into the handle to give the bindings some purchase. The arrangement does not look like it could withstand much impact, but sinew and rawhide bindings are remarkably strong. The composite haft (see Fig. 5.2d) looks simple by comparison, with one piece being slotted into another, but as with all the haft designs there is more here than meets the eye. Composite hafts are often found on hunting tools such as spears, harpoons, and arrows.

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Fig. 5.3 A close-up view of the hafting arrangement used to secure a heavy stone maul to a wooden handle using a juxtaposed haft and rope binding. A groove has been pecked into the stone to form a channel to give the rope greater purchase around the maul head. (Photograph by Joanna Ostapkowicz, courtesy National Museums Liverpool; accession number 9.12.1901.18, Haida, Masset, Northwest Coast, North America.)

Fig. 5.4 A pick with a juxtaposed joint made by binding the working bit of walrus ivory to the top of the wooden handle. The holes in the handle provide the means of securing the three components to make a tight fit. (9.2.97.1, Pribilof Islands, Bering Straits.)

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They all experience sudden compression on impact and this haft type effectively cushions against the loading to minimize breakage and to ensure the tip does its job of piercing the prey. The shock is absorbed by placing other materials, such as wood, bone, and antler in the intermediate position between the shaft and the insert. In the case of hollow-reed arrows, the haft is likely to split on impact and so the addition of a foreshaft reduces this risk by introducing a buffer between the main shaft and insert (Hamm 1991). When hunting marine mammals such as whales, a detachable foreshaft might be an advantage as it helps ensure the tip is not pulled out of the body by the drag of the main shaft of the harpoon. Composite hafts have two joints as a minimum; one to connect the foreshaft to the main shaft and the second where the insert is placed into the foreshaft. These are of course potential points of weakness, and typically they are secured with bindings to tighten the hold and to prevent splitting on contact. The foreshaft might be tapered to fit snugly into the mainshaft (inclusion haft), with a cleft haft at the other end to hold the insert. Or, cleft hafts secured with bindings and possibly adhesives can be used at both ends depending on the task and raw materials used. Another option is to splice the foreshaft to the mainshaft using bindings and maybe glue. The insert end can be a juxtaposed, cleft, or inclusion haft. There is clearly a range of potential mixes of haft types that can be used to suit the function of the tool, the properties of the raw materials, skill of the craftsperson, and, of course, the habits of tradition. It is a moot point whether the composite haft is a more complex piece of engineering than the juxtaposed haft because they fulfil different task-related needs.

A Lesser-Known Trio There are three other haft types that deserve a brief mention as they reflect other design options and traditions that might have been used in the Middle Pleistocene. The simplest is what I call an applied haft, which involves placing a partial cover over a stone tool so that it can be held safely. The covering forms a protective handle and can be made by wrapping an end with animal or plant bindings or using a loose pad to hold the tool. An iconic version of this all-in-one haft/ handle is the Australian Aboriginal knife (see Fig. 5.2e). In this example, spinifex resin covers one end of a large, especially made

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triangular blade (known as ‘leiliras’, which are also used in spears [Kamminga 1982]), and the handle is painted with yellow ochre. (The paint is presumably not an essential component, but does highlight the potential for handles to carry social information about the user.) There are variants of this approach seen in Australia and in island southeast Asia, in which a plant material is applied first and then hardened with resin or clay. The simplicity of the basic applied haft may mean it was a precursor to other more complex methods of hafting, but it is worth noting that there is usually another part of the Aboriginal knife and that is a protective sheath. Again, there is more to the tool than meets the eye. The principal drawback of the applied haft is its permanence; a knife with a dulled or broken edge can be resharpened only so far before the tool is abandoned along with its handle. Permanence is not a problem with the clamp haft (Fig. 5.2f) in which a flexible material (e.g. sapling, reed, split bamboo) is bent to fit around the bit and then bound beneath with plant or animal binders to give a tight fit. An adhesive/filler adds to the tightness of the haft. This haft looks flimsy, but the few examples I have seen (from Australia) were used to make axes and so designed for heavy compressive stress. The large stone axe blade can be easily removed for resharpening by loosening the bindings first in water than warming the resin with fire. A sandwich haft is a more involved arrangement with two separate panels (wood or bone) placed either side of the knife blade and bound. Rivets of bone (or metal) can be used in such a haft, as is seen on knives from the Arctic, but this kind of hafting involves the added steps of drilling holes in the knife blade and preparing the rivets.

THE MIND OF THE MAKER The use of binders, adhesives, and drying agents involves not just the integration of materials with different properties, but also extended planning based on a well-developed understanding of cause and effect. The artisan needs to know how the components work together as a whole, and to be able to adjust them in response to the realities of daily tool use. Differing combinations of handles, hafts, bits, and bindings become possible, and with this realization we have the

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combinatorial principle. The social and technological consequences of its invention will be discussed in the concluding chapter, but at this point it is worth stopping to consider briefly the importance of the idea of the haft, in all its forms, in terms of social learning. As tool complexity increases then learning by imitation becomes a less reliable medium for ensuring the transmission of this knowledge, especially as the components involve materials that are separated in time and space. Teaching by demonstration and correcting mistakes offers a more effective way of learning the details of hafting and, of course, having the facility for language would be particularly useful for explaining the combinatorial principle. The first hafted tools presumably replaced some basic tasks involving hand-held tools, such as cutting, but now on tap was a recursive principle that could be applied to the invention of new tools to meet specific needs. New tools would in turn generate their own sets of knowledge and expertise. Expectations of what technology can do and should do might change as well, as in the case of the evolution of the smartphone into an essential multipurpose tool and current icon of modernity.

Neural and Cognitive Implications The invention of hafting represented more than just an incremental innovation based on existing technologies. It marked a radical departure from the reductive process of stone tool-making in which pieces are removed sequentially to create the final product. Hafting is fundamentally an additive and hierarchical process that pulls together the separate components of the bit, the haft, and the handle into a working whole. It places extra demands on the various kinds of memory needed to plan and execute a long sequence of steps that might be separated over hours if not days and potentially longer. We talked about constructive memory (see Chapter 2) as probably critical in planning and imagining future states, such as a completed hafted tool (Ambrose 2010). Also likely, but still to be demonstrated, is the activation of those same neural networks, as when engaged in making a refined Acheulean hand-axe (Stout et al. 2011). The left hemisphere, as you may recall, is particularly efficient at organizing the perceptual and motor skills needed to complete a particular task. The two visual streams and the language areas of the inferior frontal gyrus (IFG) work in tandem to coordinate sequential information involving tools.

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The right hemisphere takes a coordinating role in planning long, protracted, multi-step tool-making (Stout and Chaminade 2012). If these integrated networks are essential to making a refined hand-axe, then they most certainly are needed to make a humble bread knife, and any other hafted tool. That assertion will have to do until support comes from neuroimaging research, but it is important from evolutionary perspective. It implies that the invention of hafting did not require some particular mutation or re-wiring of the brain. The neural networks were already in place by the late Acheulean to support the cognitive demands of step-wise and extended planning and for imagining the final form.

Actions and Understandings Table 5.1 outlines this increased cognitive load by showing the actions involved for each component—handle, haft, and bit—and the linked understandings of the properties of materials, their sources, and the processes of manufacture before combining them into a single tool. (To appreciate fully the complexity of the additive process, compare Table 5.1 with the actions and understanding needed to make a refined hand-axe or cleaver shown in Table 4.1.) The making of a handle involves three basic steps: acquiring the raw material, transporting it (to where it will be shaped and used), and then its shaping. The associated understandings include the properties of the raw material, its availability, plus the tools and techniques needed to shape the handle. The use of other tools here and in the hafting process (to make bindings and adhesives) adds a layer of memory and planning to the cognitive load. This cognitive layering is the combinatorial principle in action, as each component involves other actions and understandings linked to the goal of making an integrated tool. The abstraction of the finished tool links the separate stages of this process. The making of the joint or haft itself involves a similar set of sequential actions (acquiring, processing, and application), and associated understandings of the materials and their preparation. The latter will vary depending on the use of adhesives (with or without additives) and bindings. Most plant and animal adhesives involve the use of fire in their preparation, which in turn engages a separate set of actions and understandings. Experimental replication of acacia-

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Table 5.1 The actions and understandings needed to make a hafted tool. Each component—handle, haft, and bit—involves a sequence of actions and decisions, as does the final stage of assembling the tool. Compare the number of actions and understandings with those needed to make a thinned hand-axe or cleaver (see Table 4.1). HANDLE Actions Get raw material

Shaping

HAFT (Joint) Raw material

Preparation

Application

BIT Get raw material Shaping HAFTING Combine components Use/Maintenance

Understandings (a) properties of material for task (b) distance to source (c) extraction methods (d) transport back or in situ ! (e) appropriate setting (f) select tools, grips, technique (g) manage dimensions against goal (h) discard or continue ! (i) match type to task (j) if inclusion, go to next action (k) all other hafts require additional materials (and so repeat a–f) ! (l) bindings: sequence varies whether animal or plant source (repeat a–f) (m) glue: sequence varies whether animal or plant source (repeat a–f) (n) additives: if needed then a–f ! (o) shape joint on handle: tools, techniques, grips (p) apply binding only, or glue first if needed (q) test fit, hold, and adjust ! (r) repeat a–f ! (s) repeat e–h (t) discard or continue ! (u) appropriate sequence, may require time delay between drying/curing before use (v) adjust fit, reshape handle/joint (f–h) (w) match skills to tasks (x) resharpen (repeat f–h)/rehaft with new bit (i–v) (y) discard (repeat e).

based glues has highlighted the need for multitasking as attention switches between monitoring the fire and the changing consistency of the glue (Wadley et al. 2009). An inclusion haft comprising just a hole might have a minimum of one action and level of understanding, or three actions and five or more understandings if fillers and binders are needed. If so, then the properties of each material need to be

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understood along with the steps needed to make them, and the tools and the techniques involved. As for the actions and understanding needed for making the working edge, let us assume for simplicity that knapped stone is used, in which case many of the same steps are followed as used in making hand-axes (see Table 4.1). The raw material must first be acquired, then a decision is made whether to work the material there or bring it back to where the other components are waiting to be assembled. The reduction of the stone into a useable shape can be done using the two basic approaches outlined in Chapter 4 (façonnage or débitage). These in turn involve the selection of appropriate hammers, hard or soft, understandings of the combination of force, angle, and grips. Further thinning of the base or notching of its sides might be required before hafting. There are four to five actions here and an equal number of understandings. The actual hafting process brings into play at least four actions and potentially seven understandings. The components are joined in a sequence, with the number of understandings varying depending on the kind of haft and the properties of the binders and adhesives. Sinew, for example, needs to be wet or fresh when applied as binder, and tar will not spread easily unless it is hot. Time will then be needed for these materials to dry before the completed tool can be used, and even then adjustments may be needed. Reheating may be necessary to loosen an adhesive to replace or resharpen an insert. This process of de-hafting is part of the knowledge of tool maintenance, which can include storage to minimize exposure of bindings to moisture. Components may also be recycled, especially the handle, as considerable effort may be invested in the shaping of a spear shaft or adze handle (Villa and Lenoir 2006). Finally, there is the action of use and all the associated understandings that will obviously vary by tool, context, and tradition. In total, the making of a hafted tools involves 9 actions and between 29 and 99 understandings depending on the type of haft used and if there is a need for adhesive, binding, and for re-hafting after use. By comparison, making a symmetrical and finely thinned hand-axe using an organic soft hammer involves 5 actions and 17 to 28 understandings. The only subsidiary technology in this process is the selection of hammers, which involves considering the source material and its properties. Much of the additional cognitive load associated with hafting comes from the expanded range of materials

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involved and the potentially greater separation of activities in time and space. A compelling argument has already been made that the recipes and procedures used to make complex adhesives provide the best evidence we have for the existence of abstract reasoning in the early archaeological record (Wynn 2009). The act of putting together a composite tool also requires the ability to envisage the correct position of components (mental rotation) (Wadley et al. 2009), as well as the ability to hold in the mind chains of multiple thoughts (extended working memory). We could also speculate about the high levels of intentionality (theory of mind) and social learning embedded in hafting, as has been done for the making of hand-axes (Hallos 2005), but the case has now been well made by others for the complexity inherent in the combinatorial principle (e.g. Rugg 2011; Lombard and Haidle 2012).

‘Technounits’ Past and Present Our framework of actions and understandings gives us a general sense of the thought processes involved in making hafted tools. It is underpinned by experimental archaeology and microwear analyses (see below) as applied to individual artefacts and components such as adhesives. This kind of study is time consuming and a highly specialized activity. If, on the other hand, we want a rough guide to the technical complexity of broad categories of tools that might have existed in the Middle Pleistocene—knives, adzes, scrapers, and so on—then we can use the ‘technounit’ as a simple measure. Anthropologist Wendell Oswalt (1976) defined a technounit as a structurally unique component of a tool. A hand-axe, for example, is a complete tool on its own, and though other tools were used in its construction the working tool constitutes one technounit. A hand-held flake used as a knife is also one technounit, but put that same flake in a handle, add adhesive, then bind, and you now have four separate technounits. But, if binding is also used to repair a split in the handle, it does not constitute a new structural element in the functioning of the tool and so the total number of technounits remains unchanged. Similarly, the addition of paint, feathers, and beads to decorate the knife or identify its owner still does not change the working of the tool or the number of technounits. We know of course that these individual components involve multiple layers of actions and understandings, but Oswalt’s technounit

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has a more general value as it gives us a framework for looking across cultures to identify basic design components that might be effectively universal and arguably timeless. If that is the case, then we can establish the minimum number of components needed to make a hafted knife, adze, scraper, and spear in the earliest of hafted tools. As a start, I examined 124 hafted artefacts curated in the ethnographic collections of the National Museums Liverpool and the Pitt Rivers Museum, Oxford. The tools, including arrows and harpoons, represent hunter-gatherer societies of the tropics and higher latitudes from the Old and New World. The artefacts were examined using a hand lens (10x) to identify traces of adhesives that might not be visible to the naked eye, and a series of variables were recorded for each, including type of haft, raw materials used, and the reported function of the tool. Sample sizes are too small to say with certainty what the basic patterns are in terms of technounits, but they do offer some initial guidance on the kinds of hafts preferred for each tool type (Table 5.2a) and minimum number of components needed (Table 5.2b). Table 5.2a A cross-tabulation of haft types with artefact types. Total

Haft type Juxtaposed Inclusion Cleft Composite Sandwich Clamp Applied Tool Scraper Adze Knife Spear Arrow Harpoon Total

2 11 0 2 6 0 21

6 1 6 0 25 2 40

1 1 2 8 1 2 15

0 4 1 1 18 5 29

0 1 5 0 0 0 6

0 3 0 0 0 0 3

1 3 6 0 0 0 10

10 24 20 11 50 9 124

Table 5.2b A cross-tabulation of the number of technounits with artefact type. Total

Technounits

Tool

Total

Scraper Adze Knife Spear Arrow Harpoon

2

3

4

5

6

7

3 0 5 0 0 0 8

5 8 11 7 5 2 38

2 13 3 4 15 4 41

0 3 1 0 13 2 19

0 0 0 0 1 1 2

0 0 0 0 16 0 16

10 24 20 11 50 9 124

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Knives were made using a diversity of haft types (inclusion, cleft, applied, and sandwich), but not juxtaposed or clamp hafts. Adzes, however, tend to be made on juxtaposed hafts, which support compressive forces delivered by sudden impact and transversely to the axis of the handle. They also are more likely to involve multiple hafting arrangements in forming the acute angle between the bit and the handle. Scrapers tend to be made using inclusion hafts, but other types are recorded (juxtaposed, applied, and cleft) with the exception of the sandwich and clamp haft. These latter two seem to be better suited to cutting motions of the knife and axe respectively (the cutting blade of the axe is parallel to the long axis of the handle). Spears tip are generally inserted into cleft hafts, but with one instance of a juxtaposed arrangement. The small number of harpoons examined were made using composite, cleft, and inclusion hafts. The preference for composite hafts reflects the complexity of designs that include detachable points for hunting large marine mammals. Arrows were almost all made using composite hafts and this reflects the common use of hollow reeds or bamboo, which require foreshafts and use of binding to prevent the splitting of the joints. The use of cleft hafts, as you will recall, means that bindings are needed to hold the bit in place securely and this is the case in the ethnographic sample. The inclusion haft is the kind least often associated with the use of bindings. Adhesives (fillers) are used with all haft types, but seem to be less commonly applied to a juxtaposed haft used to hold an adze blade. The bindings are the key to the success of this arrangement. In terms of the minimum number of technounits, the knife and the scraper require the fewest to make, mostly two or three, with the adze and the spear needing at least three. Arrows typically involve the most, with up to seven technounits in the most elaborate arrangements and a range from three to seven. The adze, on balance, involves an average of four technounits and a maximum of five (one knife also scored a five, but it was an unusual specimen that had been repaired). Harpoons range between two and six, and the remaining tool types all averaged three technounits. The use of spinifex deserves another brief mention as it is associated with the only examples of the clamp haft recorded and these were used to make axes. The unusual properties of this glue make it possible to reduce the numbers of technounits needed to make a variety of tools types. But the apparent simplicity

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of spinifex hafts obscures the folk chemistry needed to transform the plant into glue in the first place. To put these statistics in a modern context, take a look again in your kitchen, garage, or garden shed and count the minimum number of technounits this time for a knife, scissor, hammer, potato peeler, shovel, and hatchet (or axe) if you have one. In our house, the all-in-one-piece stainless-steel knife counts as one technounit, the scissor and potato peeler each have three units, and the hammer, hatchet, and shovel each have three units as well. The latter are comparable to the minimum number of components for making an adze. This unscientific sample suggests that the number of units has either remained constant, or been reduced by mass manufacturing as in the case of the knife. What the technounit concept does not show is the stability of the basic movements involved in cutting, scraping, piercing (digging), and chopping. These are based in part on our anatomy—which has remained much the same since the evolution of the modern hand about 1 million years ago—and in part on the laws of physics. It is a safe bet that the inventors of hafting worked within these boundaries and produced tools similar in design to those seen historically and today. As Oswalt (1976: 222) observes in terms of production principles, ‘the differences between aboriginal and industrial processes are quantitative not qualitative’.

LOOKING FOR HAFTING IN THE ARCHAEOLOGICAL RECORD—A HIERARCHY OF CERTAINTY The subtitle for this section reflects the varying reliability of approaches currently used to identify the signs of hafting in the early record. Uncertainty is the rule, as only under exceptional conditions of preservation will we find a complete hafted tool; Palaeolithic archaeologists mostly find the stone inserts rather than the hafts or handles. Fortunately, the process of hafting and using tools can leave distinctive traces of wear on stone inserts, and more rarely organic traces survive of adhesives and bindings. When these two sources are found together and on part of the insert likely to have been in contact with the haft, then we can be certain that hafting took place. As we know from our review of hafts, adhesives are not always necessary,

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and so their absence on a putative insert needs to be considered in relation to the design of the tool. An adze, for example, with a juxtaposed haft can work perfectly well without adhesive, depending on the strength of the binding. A tool designed for piercing or cutting, such as a spear tip in a cleft haft, is more likely to be held in place with some kind of adhesive. There is an element of judgement in weighing up the balance of evidence for hafting with each artefact examined. Moving down the hierarchy, we come to inferences drawn from the shaping or selection of pieces that meet basic design requirements for a presumed task and haft. The least reliable marker of hafting is size alone. We will look briefly at each category of evidence in order of reliability before moving to the archaeological record itself.

Detecting Microscopic Traces of Use and Hafting In the absence of intact hafted tools surviving from the Middle Pleistocene, we must rely on a range of analytical methods to identify the traces of hafting left on stone inserts. We know from the ethnographic record that organic materials such as shell, bone, and wood can be hafted as working edges, but these are much less likely to be preserved in the archaeological record. Our knowledge of early hafting practices is by default based on stone, with one important exception from the site of Schöningen, Germany, which will be explored later (Fig. 5.5). Hafting can leave traces on stone inserts either in the form of alterations to the stone surface or more rarely in the form of surviving traces of adhesives. Sometimes the traces are visible to the naked eye (e.g. polish and fractures on an edge), but a microscope offers a more reliable means of detecting and characterizing subtle forms of wear. As the stone sits in the haft it may make contact with the bindings, adhesive, and, depending on the type of haft, it may be in direct contact with the hard surfaces of the join with the handle. A stone insert jammed into a socket in a hard bone handle (inclusion haft) is more likely to be damaged than a piece pushed into the same haft containing filler (Keeley 1982). In general, the angle and the force of loadings will cause friction between the haft components, which may leave traces on the stone in the form of tiny fractures along its edges and striations from small particles of sand or fragments of the bit trapped in the haft (Odell

Fig. 5.5 Location map of sites mentioned in the text: (1) Schöningen, Germany; (2) Inden Altdorf, Germany; (3) Köningsaue, Germany; (4) Campitello, Italy; (5) Bouheben, France; (6) Biache Saint Vaast, France; (7) La Cotte de Saint-Brelade, Channel Islands, UK; (8) Starosele, Ukraine; (9) Quneitra, Israel; (10) Qesem Cave, Israel; (11) Tabun and Hayonim, Israel; (12) Misliya Cave, Israel; (13) Umm el Tlel, Syria; (14) Sai Island, Sudan; (15) Gademotta, Lake Ziway, Ethiopia; (16) Kapthurin Formation, Kenya; (17) Kalambo Falls, Zambia; (18) Twin Rivers, Zambia; (19) Cave of Hearths, South Africa; (20) Kathu Pan, South Africa; (21) Chikri, India; (22) Ille Cave, Palawan, Philippines; (23) Flores Island, Indonesia.

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1981; Kamminga 1982). These traces can be detected at low powers of magnification (up to 100x), and in terms of understanding how a tool was used they provide valuable information about the general hardness of the contact material (soft, medium, or hard) and direction of use (Keeley 1980). In terms of hafting, they can help identify the boundaries of the area hafted based on patterns of scarring and abrasion (Lombard 2005; Rots 2010: 31). At higher powers of magnification (>100x) more information can be gleaned about the location areas of friction in the haft that create different degrees of smoothing and polish including ‘bright spots’ resulting from intensive rubbing (Rots 2010: 34). Polishes can also be identified as to the kind of contact material such as bone, skin, wood, and other plant fibres, but not all types of stone will preserve traces of polish. Glassy and very fine-grained flint-like materials are best suited to high-power magnification analysis, whereas coarse-grained rocks such as quartzite offer little scope for study other than by low-power magnification (Taylor 2011). Polish, rounding, fractures, and striations can also be created naturally by the processes that preserve artefacts in the archaeological record. A stone insert left at a riverside camp might be swept into the water at flood stage and become abraded by swirling sand, and its edges fractured by contact with other rocks. Chemical alteration to its surfaces might then follow over time as it becomes buried in sediments that alternate between wet and dry. These are just a few of the environmental agents that add to the analyst’s task of disentangling the various sources of wear. To these we can add the complication of human variables including edge damage caused during manufacture, from our excavation tools (trowels and picks), and even in storage as artefacts bang together in drawers or bags. Some tools also lend themselves to a variety of tasks that will leave a mixture of use traces. The adze is one such tool that can be used for wood-working, stripping bark, scraping hides, and butchering a carcass (Clark 1958). (Closer to home, a car key makes a good paint-tin opener.) Many stone artefacts, in the end, are simply not suitable for analysis, and of those that are they may reflect just a few of the activities in a group’s technological repertoire. The chances of finding hafting traces can be improved by selecting tools for analysis that resemble inserts found in ethnographic collections and from experience gained in making and using hafted tools. Once the initial winnowing process has been completed, then follows the time-consuming stage of

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identifying traces of wear by type, location, and extent of coverage. Each edge and surface must be examined systematically and recorded photographically and described. Only a small proportion of artefacts from an assemblage can be studied in such detail, and there is understandably a bias in selecting retouched pieces over plain flakes as potential inserts. The interpretation of wear traces requires another level of investment in time, without which the process is incomplete and the results are untrustworthy. A reference collection of hafted tools needs to be created in which the tools are put to a variety of uses under controlled conditions, including the removal of the insert from the haft (‘dehafting’). The wear traces on the reference pieces are examined in the same detail as above, but now patterns of wear can be linked directly to the kind of haft, motion of use, and contact materials such as soft and hard woods, wet and dry bone, wet and dry hide, and so on. As a reference collection grows so does the analyst’s capacity for interpreting patterns of use in the archaeological record. The wider the range of hafts used and the greater the variety of contact materials tried, then the more robust are the inferences made from the present to the past. Ideally, the analyst would use the same materials in her experiments as were available prehistorically for the making of bindings, adhesives, handles, and stone inserts. The analyst may also need to learn to make all components of the hafting process or at least engage expert help. There is a final critical step in this long process and that is the independent verification of the analyst’s interpretive skills by ‘blind testing’. The analyst is presented with a collection of objects that may or may not have been used and asked to identify the part of the tool that was hafted, the haft material used (bindings, adhesives), the hafting method, the direction and method of use. It is even possible by blind testing to see how well the analyst can discriminate between hand-held and hafted tools (Rots et al. 2006). The results are then scored to give a measure of reliability at different magnifications and to highlight areas for improvement. Despite the increasing rigour in the design of microwear research methods, there remains an element of art to this science as observations of wear traces vary between researchers (Odell 2004). This issue is being addressed with the application of methods of laser scanning of surfaces that have been used successfully in engineering, but which are new to archaeological research. It is now possible to generate

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three-dimensional images of tool surfaces that show in great detail the textural differences between wear traces (e.g. Evans and Donahue 2008). The differences can be quantified and then compared for statistical significance. For the time being, the now traditional approach of using light-reflected microscopy remains the only reliable source of indirect evidence for the invention of hafting.

Hafting Residues More direct evidence sometimes survives in the form of adhesives (tar, pitch, and resin) adhering to the hafted portion of an insert. Fortunately, the identification of these traces does not always require a full-blown microwear analysis, as the material might be easily visible to the naked eye. With this kind of find, the location of the adhering material is recorded in relation to working edges to establish the likelihood that the artefact was once hafted (e.g. Mazza et al. 2006). The chemical constituents of the adhesive are subsequently identified using a range of analytical techniques.3 Organic ‘microresidues’, as the name implies, do require the use of microscopes to identify their presence before analysing their constituent elements. Their identification on working edges has played an important role in inferring hafting arrangements and potential tool types (Lombard 2005), but traces can also result from repairing tools (Pawlik and Thissen 2011). The preservation of such residues depends on the environmental conditions of the site (caves are good as are sites with these extreme conditions: very dry, very wet, very acidic, or very alkaline), as well as the type of residue. Animal tissues such as skin and muscle are less likely to survive bacterial decay than plant residues (Hardy 2004; Langejans 2010). The past use of adhesives for hafting can, in rare cases, be inferred in their absence. A 54,000-year-old flint artefact (scraper) from the 3 The range of analytical techniques typically used to identify the elements used in adhesives include X-ray diffraction (XRD), X-ray fluorescence (XRF), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and especially gas chromatography-mass spectrometry (GC-MS) for the identification of lipids characteristic of birch tar and pitch (betulin). GC-MS was used in the study of the hafted tools found with the body of ‘Oetzi’ the 5,000-year-old frozen man found in a mountain glacier on the Italian-Austrian border. His copper hatchet blade and stone arrowheads were attached to their respective hafts using birch tar (Sauter et al. 2000).

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Israeli site of Quneitra was found to have an unusual pattern of colouring, with the base of the object being much darker than the retouched working edges (Fig. 5.6a). The pattern was replicated experimentally by exposing three replica hafted flakes to sunlight for months as they lay in trays of sediment from the site (Friedman et al. 1995). The result was a rapid lightening of the exposed surfaces whereas those protected by the hafts retained the original dark colour of the flint. It seems that the archaeological specimen had been exposed to light before being buried, after which the haft decayed. The discolouration pattern on the artefact has been used to reconstruct a knife-like hafting arrangement (Fig. 5.6b).

Tool Form and Visible Damage We now move one step down the hierarchy of certainty to consider inferences drawn from artefacts that are not suited to microwear analysis or which have yet to be examined for such traces. Inferences can be drawn from similarities in the size, shape, thickness, and weight in relation to known hafted inserts. We can add to this level of uncertainty patterns of damage that are similar to those recorded experimentally or ethnographically on tools of known use. The chain of inference also relies in part on the assumption of least effort on the part of the tool-maker. In other words, the artisan only did what was necessary to match the insert to the properties of the haft, which in turn reflects the task at hand as well as the subtle influence of tradition (Wilmsen 1974). Such a functional perspective may seem odd in a commercial world driven by the marketing of new and often unnecessary products, but recall we are dealing with small prehistoric communities where conformity rather than individualism was probably the norm. This kind of reasoning is intuitively appealing. We can expect the form of the insert to be selected and modified to meet the basic physical stresses of the task; a square spear tip will not pierce an elephant’s hide nearly as well as a pointed one. The design of the haft will also impart certain constraints on the dimensions and shape of the working bit. An inclusion haft can only accommodate inserts that are no larger than the socket or hole. A cleft haft is a less limiting arrangement, but too thick an insert might split the handle under a direct compressive force. The thickness of the haft arrangement as a

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Fig. 5.6a A drawing of the two surfaces (upper row) of the stone artefact from Quneitra, Israel, with shading showing the location of the discolouration on the surfaces and one edge (bottom row). (Reprinted from Friedman et al. [1994–5: Fig. 1] with the permission of the Israel Prehistoric Society.)

whole may also interfere with the aerodynamic properties of a thrown spear. With a juxtaposed haft, the insert might fit more securely if it has a flat surface where it sits on the supporting platform, and the edges might be blunted to prevent cutting the binding. The edge angles of a presumed working edge can also help in making an

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Fig. 5.6b A reconstruction of the hafting arrangement of the Quneitra scraper showing the use of a cleft haft, adhesive along the areas of contact between bit and haft, and a sinew binding. (Reprinted from Friedman et al. [1994–5: Fig. 1] with the permission of the Israel Prehistoric Society.)

informed guess about the use of a tool and the likelihood it was hafted. A thin sharp stone edge would not last long when used for chopping or adzing and is better suited for cutting. We can see how haft design affects the choice of stone insert in a contemporary case study. The Gamo people of southwestern Ethiopia make two different kinds of handles for their hide scrapers (Weedman 2006). One handle design is a carved hollow ring of wood with a stone bit inserted into a slot on either side (zucano) (Fig. 5.7). The working edge of the bit is retouched to form the correct angle for scraping and the two sides are also blunted by retouch to fit the slot in the handle. The inserts are held in place by the snugness of the fit and with the help of acacia adhesive. The second design is a cleft wooden haft with the stone flake wrapped in hide or cloth before being inserted in the cleft and bound by twine (tutuma). The wrapping of the insert means the binding is protected from damage, and so the sides of the stone insert do not need to be blunted by retouch. The open design of the cleft also means that shaping of the sides is not

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Fig. 5.7 The double-haft zucano scraper (lower) and the single-cleft haft tutuma scraper (upper) as used by the Gamo of Ethiopia. The stone inserts have to be shaped before being hafted in the zucano inclusion haft, but no tapering of the sides is needed for the scraper inserts in the tutuma cleft haft. (After Weedman 2006.)

necessary, and instead the selection of an appropriate insert is based on the shape of the working edge. Each haft design is passed from father to son along with the process of selecting the correct kind of stone and the making of the mastic or bindings. Both types of tools are equally efficient, though the Gamo do not consider time and effort as important qualities when assessing the value of these scraper designs (Weedman 2006: 210). (Perhaps time is not the scarce resource we perceive it to be.) As the stone inserts are resharpened with use they change in size and shape, and converge in appearance. Both inserts change from their unused appearance and become shorter, thicker, and in the case of the tutuma inserts the sides are also now blunted by retouch, but for scraping rather than fitting the haft (Shott and Weedman 2007). The zucano inserts were larger at the start and have a longer use-life with more episodes of resharpening possible before being discarded. The life history of these inserts offers a cautionary tale about inferring tool use from the extent, angle, and location of retouch. The transformation of the tutuma insert shows how unreliable inferences can be when using standard methods of classifying stone tools based on retouch and shape.

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Points for Piercing Given the importance of hunting in human evolution, it is not surprising that considerable attention has been paid to identifying the attributes of stone spear, dart, and arrow tips. Practical experiments involving the piercing of animal carcasses support what seems intuitively obvious; a stone-tipped projectile is a more effective killing tool than a sharpened wood, bone, or antler point (Frison 2004). The stone tip has the advantage over other materials of its ability to cut through the tough hide of an elephant or bison, so allowing the shaft to move deeply into the body and causing greater blood loss and internal damage. If after contact the point detaches from the shaft or breaks in the body, it can still damage the animal as it moves. These features hasten the death of the prey, which is important when dealing with large game; a wounded elephant or African buffalo is a formidable foe. A stone-tipped spear offers another advantage—a ready-made cutting edge for butchering your kill (Villa and Lenoir 2006). Recent hunters of large game also provide supporting evidence for the preferred use of spears (stone or iron tipped) for killing large game, at least in Africa and North America (Ellis 1997). Sharpened wooden spears are useful for killing small and large game and the tips are less likely to break on contact than stone (Smith 2003; Waguespack et al. 2009). Stone tips, however, still have the advantage when it comes to penetrating a really thick hide. Whichever material is used, the design of the shaft, haft, and tip reflects a compromise between reliability, maintainability, portability, and durability (Bleed 1986; Nelson 1997; Frison 2004). There is some debate about the killing distance of thrown spears, which could have been just 8 metres if based on ethnographic data (Churchill 1993) or 15–30 metres if based on spears and javelins used by Roman soldiers (Villa and Lenoir 2006: 114). This seemingly arcane discussion has real importance for reconstructing hunting strategies. An 8-metre range would put a hunter at considerable risk, especially if the animal was wounded rather than killed. To avoid such a situation a group of hunters could devise a plan that would minimize the risk to themselves by placing the game at a disadvantage. Driving a herd over a cliff, into a gully, or into a swamp would each offer different opportunities for dispatching the animals using short-range and thrusting spears. If, however, spears

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were effective at 15 metres or even 30 metres, then other options become viable and big-game hunting is less hazardous. The bow and arrow and spear-thrower have the advantage over the spear of extending the killing range and being lightweight and more portable, but these technologies post-date the Middle Pleistocene (see Chapter 6). Putting aside the debate over the effective range of hand-held spears, these are low-velocity weapons propelled by muscle alone. Since the evolution of Homo erectus about 1.8 million years ago, humans have had the anatomical capacity to throw spears in an overhand motion with force (Roach et al. 2012), though the extent to which Neanderthals hunted with thrown as opposed to thrusting spears remains a matter of debate (Schmidt et al. 2003; Rhodes and Churchill 2009; Shaw et al. 2012). The effectiveness of a thrown spear depends on the shape of the tip as it first pierces the skin and then penetrates the prey. Most stone spear tips are either triangular or lenticular (usually bifacially flaked pieces) in cross section, and broader at the base than at the tip. Because archaeologists rarely find a complete hafted spear, they have developed a variety of measures that can be applied to individual stone artefacts to distinguish between spear, dart, and arrow tips. The study of ethnographic specimens of known use has shown that width and weight can be good indicators of tool type with spear points generally wider and heavier than darts and arrows (Thomas 1978; Shott 1997; Brooks et al. 2006). The shape of the tip is also a critical feature of the effectiveness of these tools, and there is now a widely applied formula called the tip cross-sectional area (TCSA) (Hughes 1998). The TCSA incorporates the maximum width and thickness, and when applied to specimens of known use (from museum collections and replication experiments) it can discriminate between different types of projectile points (e.g. thrusting spears, thrown spears, darts, and arrowheads) (Shea 2006; Sisk and Shea 2009; but see Clarkson 2011). It also gives a guide to the amount of force needed to deliver a lethal blow: the larger the tip area the more thrust is needed to push the spear deep into the animal. A variant of the measure is the tip cross-sectional perimeter (TCSP) that provides an estimate of the cutting edge that opens a hole in the unfortunate victim (Sisk and Shea 2011). Together, these measures give a good indication of the likely use of a pointed artefact, but some uncertainty will always remain, given the limited number of hafted stone-tipped spears that are available in

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museum collections. Experimental replication studies are particularly valuable in this context as they can be used to test the efficacy of spearpoint designs that might be rare ethnographically, but which may have been common in the past. Replication experiments have also identified patterns of breakage that occur as a result of a spear tip hitting an animal (especially spalls) (Pargeter 2011), and these combined with other measures help strengthen the chain of inference leading to the interpretation that pointed artefacts were hafted (Shea 1988). In addition to width, weight, cross section, and perimeter, there is also the angle of the tip edge, which can distinguish between tools used as projectiles and those used as knives (see Villa and Lenoir 2006). For thrown and thrusting spears, the thinning of the base of the point by retouch improves its fit in the haft, reduces the weight of the tool, and creates a slimmer profile, so reducing drag as the haft enters the body. This is probably more than enough detail of the mechanics of killing by piercing, but it is this kind of detail that is critical to inferring the presence of hafted spears from the points alone. A tapered base might also be accompanied by notching on the side or shoulders of the point to improve the hold of the binding. These technological features are typically the basis for recognizing specific point types that can be used as markers of archaeological cultures (e.g. Folsom in North America, and Still Bay in South Africa) (Fig. 5.8).

Flakes as Points The shaping and thinning of spear points by retouch was not always necessary, especially for those used in thrusting spears. For these weapons, the triangular flakes produced from Levallois cores could be hafted with little or no retouch. The thick bulb of percussion at the base (or side) of the flake could be accommodated within a juxtaposed haft, or a cleft haft if the shaft is thick. Thinning the bulb would improve the fit, but in either haft type a good strong binding material would be essential unless, of course, you had access to spinifex. Usewear studies provide the evidence for making the connection between Levallois flakes with hafting and their use as spear tips in Africa, southwest Asia, and Eurasia (e.g. Tryon et al. 2006; Villa and Lenoir 2006). There is, however, an inherent risk of circular reasoning in such broad extrapolations, especially in the absence of supporting microscopic evidence of use. Triangular flakes can be used for a variety of

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Fig. 5.8 A tapered and basally thinned (fluted) Folsom point designed to fit into a cleft haft. The artefact is 5.8 cm long.

purposes including knives. Recent developments in the analysis of digitally recorded patterns of visible damage to edges and tips have been used to distinguish likely knife blades from spear tips as well as right-handed from left-handed users (Schoville 2010). An impressive range of analytical techniques is now available to identify potential spear tips, and, indirectly, hafting in the early archaeological record. Unfortunately, there has not been a similar level of interest given to other kinds of inserts including adze and axe bits, chisel edges, or drill bits. Perhaps there is a subtle bias among researchers in favour of tools linked to the glamour of big-game hunting, or maybe the design constraints of spears are just simpler to model. Microwear analyses are needed to identify these other activities on stone inserts. Perhaps one day there will be robust measures that can distinguish adze from axe blades that are supported by ethnographic and experimental data. In the interim, the existence of these kinds of hafted tools cannot be assumed from tool morphology alone.

Small and Blunt There is another category of stone artefact that belongs in our hierarchy of certainty by virtue of the way it is shaped and its size. Cast

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your mind back to Qesem Cave (Israel) and the blades found there from 400,000–200,000 years ago. Microwear analyses led to the conclusion that the blades were hand-held rather than hafted, with the majority of blades manufactured so that the surface opposite the cutting edge was comfortable to hold (Lemonier et al. 2006). These ‘naturally backed’ blades retained the smooth exterior surface of the cobble on which they were made. The deliberate blunting or backing of an edge is achieved by removing a series of small flakes at right angles along an edge, or by breaking it against a hard surface. Either way, the edge is flattened to make it safer and easier to hold. The same principle of blunting to improve the grip applies to smaller flakes and blades that have been blunted for inserting in a haft (Fig. 5.9). A blunted edge is less likely to split the haft and sever the bindings as we saw in the case of the zucano scraper made by the

Fig. 5.9 An array of backed flakes and blades from Mumbwa Caves, Zambia (Unit VII, 130,000–105,000 years ago). Scale in centimetres.

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Gamo people of Ethiopia. The blunted edge also increases the surface area in contact with an adhesive, so strengthening the hold on the insert. Backing can be used to prepare flakes and blades as inserts in any type of haft, and for a variety of uses in addition to scraping, including for cutting (knives, sickle blades), drilling, and piercing (as the tips of spears, darts, and arrows). When a backed piece is small then the assumption is often made that it was designed to be hafted rather than hand-held (e.g. Barham 2002). If this is the only evidence for hafting, then the inference falls down the hierarchy of certainty. But if it is supported by a combination of microwear analyses, residue patterns (especially of adhesives on the backing), and replication experiments, then the inference rises to the top of the hierarchy (e.g. Odell 1981; Lombard and Pargeter 2008; Wadley and Mohapi 2008; Lombard and Phillipson 2010; Yaroshevich et al. 2010). The small size of backed inserts also reduces the weight of the complete tool, and when they are damaged beyond repair they can be easily replaced by softening the adhesive and bindings. Carrying a set of spare inserts is quicker than shaping a new haft and handle. And if stone is in short supply or only found in small pieces (pebbles), then very small inserts (microliths) can solve both problems at once. The innovation of backing added greatly to the versatility of hafted tools as lightweight weapon tips, as we will see in the next chapter, but it may have had its origin in the Middle Pleistocene.

Just Being Small is Not Enough As mentioned, the lowest level of certainty applies to assumptions of hafting in the archaeological record based on artefact size alone. Those who argue for early hafting in the ‘small tool tradition’ of Middle Pleistocene Europe base their inference on the size of some flakes (about 30–20 millimetres in length) (Burdukiewicz 2003: 71). This inferential chain has just one link, which is the presumed difficulty of holding such a tiny tool. Recall from Chapter 2 that the human hand was already capable of fine manipulation long before this tradition appeared, and we still use small objects like pins and needles without the need for handles. Hafting might have made these flakes easier to use, but would have involved the investment of time and energy in preparing handles and hafts. For now, there is no independent supporting evidence that hafting was practised as early

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as 600,000 years ago in central Europe or in western Asia. This claim is therefore not considered any further.

THE ARCHAEOLOGICAL EVIDENCE—AT LAST With a hierarchy of certainty now established we can turn our attention to the evidence itself. The chronological starting point is the preservation of adhesives used in hafting stone inserts, followed by the combination of residues from hafting with microwear traces of hafting and use.

Tar Residues The site of Campitello Quarry near Florence, Italy, has produced what is for the moment the earliest evidence for hafting in our hierarchy of certainty (Mazza et al. 2006). Three stone flakes were found, two of which bear traces of adhesives (Fig. 5.10). They were found in riverside sediments among the remains of an extinct form of straight-tusked elephant (Elephas [Palaeoloxodon] antiquus) and the teeth of several species of rodent. (There is no evidence from the bones that the tools were used to butcher the elephant.) The animal remains, and in particular the rodents, are the basis for attributing this deposit to a cool period, but not a glacial stage, late in the Middle Pleistocene before MIS6 (older than 187,000 years ago). The age estimate is a minimum assuming that the artefacts and bones do belong together rather being a jumble created by the meandering river. The artefacts look fresh, with no sign of having been moved by the river, and so are probably contemporary with the bones. The most impressive artefact is a thin asymmetrical flake with a black organic deposit adhering to approximately half of its surface (see Fig. 5.10a). The two exposed edges are sharp, which suggests the adhesive was applied deliberately to create at least one long cutting edge, or perhaps a tool with a point where the edges meet, in which the case the tip appears to be broken. The adhesive is uneven in its coverage, being thicker on one side around the bulb of percussion. On the opposite side the adhesive appears to have a groove or channel up the middle. It may reflect the linear scar pattern underneath, and

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Fig. 5.10 The stone flakes from Campitello Quarry, Italy. showing traces of adhesives used in hafting on (a) and (c). (Reprinted from Mazza et al. 2006 with the permission of Elsevier Ltd.)

perhaps this groove was formed by the haft. The second flake (see Fig. 5.10c) was made on a prepared core and is symmetrical with a patch of adhesive surviving on its bulbar surface. Its tip is broken, but further analysis is needed to determine the cause of the break. The molecular composition of the adhesives gives the Campitello artefacts their real wow factor—they contain markers characteristic of birch tar produced from bark or wood (Mazza et al. 2006: 1,315; Modugno et al. 2006). As you will recall from the discussion of plant glues, birch tar is synthesized using fire in a sealed pit or container. The surprise is twofold: first, that this sophisticated folk chemistry had been invented by the late Middle Pleistocene and secondly, by Neanderthals rather than Homo sapiens. The great age is a marvel in its own right, but the geochemical analyses challenge our long-held preconceptions about the limited intellectual capacity of Neanderthals. Campitello is not the only association of tar-making technology with Neanderthals, but it is the earliest. The use of tar is seen again 120,000 years ago at the site of Inden-Altdorf, Germany, and in the context of what was probably a hunter-gatherer camp not far from a river (Pawlik and Thissen 2011). Microwear analysis

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identified use on 136 stone artefacts, and of these 39 were hafted using pine tar. A range of activities were reconstructed for these hafted tools, including knives for cutting hide, scrapers for working a variety of hard and soft organic materials (e.g. plants, and perhaps hide and wood), and one flake used for scraping and engraving mammoth ivory. There were also 15 hafted spear points including pointed flakes, blades, and points shaped by retouching. The microwear results also revealed that three of the points were used for other purposes (cutting and engraving). This should not be surprising given the practical reality that tools can have multiple uses, such as the adze with its strong chopping edge (Clark 1958; Lee 1976). Microwear and residue analyses provide a timely reminder that the old archaeological practice of building tool typologies based on assumed function is inherently flawed. Back at the riverside camp of Neanderthals, three sandstone cobbles were found covered in the tar. These may have been used to collect the liquid birch oil that trickled down to the bottom of the distillation pits. There are other tools from Inden-Altdorf that have traces of tar on their surfaces but which were not hafted. They may have been involved in the process of repairing hafted tools or were just handled by individuals with tar on their hands. Hafting with adhesives is a messy business. Finally, this remarkable site also gives an insight into another important reality about the invention of hafting—it did not sweep away the tradition of hand-held tools. Hafted and non-hafted tools were used for scraping and cutting, but a separate toolkit existed of just hand-held tools. These were used to engrave, drill, grind, and chisel (Pawlik and Thissen 2011: 1,706). There may be a profitable line of experimental research here, one which examines correlations between task, tool, and grip to identify those activities that are still equally effective using the unaided hand (and the technology of the time). A flake with a strong, sharp triangular tip might be a more efficient tool for piercing hides than its hafted equivalent, especially given the considerable effort involved in hafting. At some point a threshold is crossed that gives the hafted drill bit the edge. Once crossed, improvements in the design of inserts (e.g. thinner, sharper, smaller) make hafting increasingly the option of choice and of tradition. Before moving on from the use of tar in the early archaeological record, it is worth mentioning a later example from Germany—also associated with Neanderthals—as evidence of continuity of this complex technology. Two lumps of birch bark tar were found in the 1960s at the site of Köningsaue from two separate layers. The radiocarbon

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dating of the tar pieces gives them a minimum age of at least 44,000 years ago (Grünberg 2002). (Dates in this range are at the limit of reliability of radiocarbon dating.) The larger piece came from a level associated with a brief warm phase or interstadial attributed to Marine Isotope Stage 5a from 85,000–74,000 years ago (Pawlik and Thissen 2011). This piece is of particular interest because it preserves traces of a flaked stone insert, a wooden haft, and a finger print, probably a thumb. The geochemical analysis of the tar also suggests it was manufactured by a similar dry distillation process to that used at Inden-Altdorf (Koller et al. 2001). At roughly the same time in western Asia (about 72,000 years ago), Neanderthals were collecting bitumen from outcrops, and carrying it long distances (40 kilometres) before turning it into an adhesive using heat (Böeda et al. 2008). About two hundred tools from the Syrian site of Umm el Tlel were found to have microscopic traces of bitumen and in locations indicating that they were hafted. The practice looks to have been widespread at this site and to have continued over time as it is found in the youngest levels dated to 40,000 years ago (Boëda et al. 1996).

Hafting, for the Birds? To the north, at the Ukranian site of Starosele, there is strong evidence for the hafting of scrapers, points, and denticulates (sawtooth edged flakes) using plant-based adhesives or bindings (Hardy et al. 2001). The evidence comes in the form of the location and type of organic residues combined with microwear patterns. The earliest level is approximately 80,000–70,000 years old and so roughly comparable in age to the Syrian and later German use of tar, but what warrants attention here is the use of hafted scrapers for processing plant materials as well as hides. Neanderthals are not usually thought to be users of plants, either as food or for making tools, but the adhesives and working edges both show that these humans were well acquainted with the properties of this resource. The site sequence also provides evidence of hafted projectiles—spears of some sort— with plant-based adhesives or binders. One spear has intriguing traces of feathers on its tip and on one edge with the bird identified as being from the order Falconiformes (falcons). Hunting falcons with spears seems an exercise in futility, but clearly the Neanderthals here managed to get hold of the animal, dead or alive, which raises the question

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of what was it used for? There is not much meat on a falcon in relation to the effort involved in catching it, so perhaps the bird was sought for its feathers or hollow lightweight bones. The remains of birds, including birds of prey and carrion feeders (chough and crow), have been reported from Neanderthal sites in France and Italy— earlier and later than Starosele respectively (Hardy and Moncel 2011; Peresani et al. 2011)—which hints at a widespread pattern of feather use. If you are thinking that maybe they were fletching arrows with feathers, then put that thought aside as there is no evidence yet for bow-and-arrow technology in Europe before the arrival of Homo sapiens.

Microwear Traces of Hafting, but no Residues This digression into the use of birds has taken us far off the path of identifying the earliest signs of hafting. So, it is back to the straight and narrow with a slight drop down the hierarchy of certainty. In the absence of residues of adhesives we are left with inferences drawn from the location and type of microwear traces on a putative stone insert. As noted, adhesives are not always needed and so their absence only slightly weakens the reliability of our inferences, especially in the case of inserts used in juxtaposed and inclusion hafts. The next earliest evidence for hafting comes from northeast Africa, and may have involved the use of inclusion hafts. In the middle stretch of the Nile River lies Sai Island (Sudan), which was occupied late in the Middle Pleistocene by makers of Acheulean bifaces and then by producers of hafted and hand-held flake tools (Middle StoneAge/Middle Palaeolithic). The earliest Middle Stone Age level (‘Lower Sangoan’) falls in the age range of 180,000–220,000 years ago (MIS 7) (Rots and Van Peer 2006), which makes this assemblage potentially older than the tar-encrusted flakes from Campitello, Italy. The evidence for hafting comes from a distinctive stone tool type—the coreaxe—found here and in eastern and central Africa where Sangoan assemblages occur. The core-axe, as the name suggests, is a thick object with working edges like those found on much later stone-axe and adze blades. If this is the case then it should be hafted in a way that can absorb the high impact of the task and chances are that its cutting edge will be visibly damaged and so reveal its use. The replication and hafting of core-axes from Sai Island has also revealed

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patterns of damage that occur within the haft (scarring and crushing) where the tool is in contact with the handle and the bindings (Rots 2010). The core-axes from Sai are elongated, symmetrical, and bifacially shaped like a hand-axe, but lack the tapering teardrop shape. Traces of hafting damage were found across the mid-section of the inserts, with one end clear of the haft and the other being the working edge (Rots and Van Peer 2006). The cutting edge is more acute than the opposite end, which suggests that the inserts were designed for the task and for the haft. The haft design can then be reconstructed as a socket cut into the handle (inclusion), a cleft or split haft with binding, or a clamp haft wrapped around the bit and held tight with rawhide binding (Rots et al. 2011) (Fig. 5.11). If Acheulean hand-axes and cleavers were hafted, then these are possible haft arrangements. Experimental archaeologist Steve Watts (2006) has found that the clamp haft is very effective when using replica Acheulean large cutting tools for chopping wood. In theory, microwear

Fig. 5.11 A replicated hafted core-axe from Sai Island, Sudan, showing the use of a split haft and binding. (Image courtesy of Veerle Rots who retains all rights.)

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traces of hafting should survive on well-preserved specimens so long as they are made of suitable fine-grained stone. Archaeologists have long speculated about the use of core-axes, with wood-working and digging in the ground cited as possibilities (Clark 1970: 44, 112). In the case of the Sai Island specimens the edge angles are too blunt to be effective for working wood, and all that can be said with certainty is that they were used on hard materials (Rots and Van Peer 2006). At Sai that could have involved digging into a hard sediment or quarrying stone, such as the yellow and red ochre that was brought to the site to be ground into a powder (Van Peer et al. 2004). Experimental replication studies of core axes from the south-central African site of Kalambo Falls (Zambia) show that they could be used effectively when lashed to a juxtaposed haft, but unfortunately the artefacts themselves do not preserve clear traces of hafting and the site remains poorly dated (Taylor 2011).

Chopping and Spearing—Practical Motivations for the Invention of Hafting The core-axes from Sai Island are currently some of the earliest examples of hafting known, but hand-held tools continued to be made, as was the case at the Neanderthal site of Inden-Altdorf. The combinatorial revolution was selective in its early applications. At Sai the occupants hafted when it was necessary for the job and in this case hand-held adzing was a less efficient, if not more painful, option when the task involved chopping a hard material. There was another type of tool hafted at Sai—the spear. Impact damage was found on a single broken point in the Middle Sangoan level (younger than the Lower Sangoan) (Rots et al. 2011). Adzing and spearing both involve striking an object with force, especially in the case of the thrusting as opposed to the throwing spear. The addition of a handle to an adze blade increases the amount of force that can be applied to a hard surface and it may even improve the precision of the chopping action, but this is speculation in the absence of supporting experimental evidence. It certainly reduces the damaging impact on the hands and wrist, and minimizes cuts and the risk of infection. Adding a stone tip to a spear shaft offers similar benefits in terms of the efficacy of the piercing action and reducing the inherent risks to the hunter. The stone-tipped spear has already

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been mentioned in the context of its impact on human evolution—it helped turn us into super-predators based on a division of labour and a cooperative ethos—to which we can add its more subtle effect of increasing the life expectancy of hunters. The risks and rewards of hunting are strong candidates as catalysts for the invention of hafting, or certainly reasons for its rapid adoption. If there is a whiff of testosterone about this scenario, then let me balance it with the observation that hafting may equally have been invented to solve problems arising from the humdrum tasks of daily life. You could argue that the making of tools to make other tools—which long predates hafting—was the first industrial revolution, but it did not involve making anything wholly new, just making things more efficiently. It did, though, provide the craft knowledge and the needs for less dramatic applications of hafting. There are still too few good reliable examples of hafting in the Middle Pleistocene to put any of this speculation to the test. On that note, it is worth now mentioning a potential candidate for the prize for the earliest evidence of hafting. Research in the central Rift Valley of Ethiopia, near Lake Ziway, during the late 1960s and early 1970s identified a sequence of Middle Stone Age sites buried beneath volcanic ash and hill-slope sediments (Schild and Wenforf 1993). The ash deposits provide the dates for the sequence with the oldest ash fall now dated to about 280,000 years ago (using 39Ar/40Ar dating) (Morgan and Renne 2008). The stone artefacts beneath this ash layer are made of obsidian (volcanic glass), which produces extremely sharp but brittle edges. A small sample was examined using low- and high-power microscopy, but this was in 1973 and before the development of now standard techniques of use-wear and hafting analysis. A small number of points and pointed (convergent) scrapers were examined for striations reflecting direction of use. The conclusion was reached that some were used in a saw-like motion and others for cutting at an angle (Schild and Wendorf 1993). Several of the points also had their bases thinned as might be expected of hafted pieces, and one has what appears to be an impact scar. There is clearly the potential here for an up-to-date analysis of the Lake Ziway material, but for now it must be placed in the category of possible, but unsubstantiated evidence (Table 5.3). More certain evidence comes from the Neanderthal site of Biache St Vaast, northern France (more than 200,000 years ago, MIS 7) (Rots 2012). Traces of hafting damage were initially reported on seven

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Table 5.3 The ‘hierarchy of certainty’ of the earliest evidence for hafting in the archaeological record listed by site or location, age, and inferred tool function. Residue and/or microwear Campitello, Italy: 187,000 (?) Sai Island, Sudan: 220,000–180,000 (adzes) Biache St Vaast, France: >200,000 (spears, knives, adzes, scrapers, and drills) Hayonim and Tabun Caves, Israel: 250–200ka (spears) Artefact form and macroscopic damage Kathu Pan, South Africa c. 500,000 (spears) Lake Ziway, Ethiopia: 285,000 (spears) La Cotte St Brelade, Jersey: 180,000

pointed pieces that include ‘convergent scrapers’ (Beyries 1988). As an aside, this artefact type comes from a still widely used typology of European Middle Palaeolithic stone tools developed in the 1950s by the archaeologist Francois Bordes (1950). Bordes’ classification scheme separates tools into types based on their shape, location, and type of retouch, and assumed function. As a consequence, artefacts with heavily retouched sides that converge to a point are thought to have been scrapers, whereas some may have been used as hafted spear tips, hand-held knives, and piercing tools (Villa et al. 2009; Moncel et al. 2009). Microwear analyses offer a valuable means of distinguishing between these different uses. In the case of Biache St Vaast, we can now say that Neanderthals used a range of hafted tools including spears, knives, scrapers, adzes, and drills. The evidence comes from the analysis of 157 tools by microwear specialist Veerle Rots (2012), who was able to recognize the distinctive damage patterns left by hafts and bindings. She identified spear tips by looking for a combination of marks including impact damage on the tips and edges of hafted points. The form of hafts used could also be inferred from the kinds and location of the wear patterns. As might be expected, spear tips were placed in cleft hafts and then bound tightly. The variety of hafted and hand-held tools identified at Biache St Vaast

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supports earlier interpretations of the site as a specialist hunting camp based on the butchered remains of large game including rhinos and especially bears (Roebrooeks and Tuffreau 1999:123–4). Rots’ analysis lets us paint a vivid picture of a small group of Neanderthal hunters having planned an expedition to intercept game and arriving well equipped with the expertise and tools for the job. In the case of the artefacts from Biache, the pointed tools all show traces of wood-working and were probably hafted scrapers or knives. They lack the characteristic impact damage seen on projectile points, and that leads us to the next step down the hierarchy of certainty. In southwestern Asia (the Levant) there is also evidence of the hafting of stone points that are as old, if not older, than the Sai Island adzes. The Israeli cave sites of Tabun and Hayonim provide us with the most detailed regional chronology for the early Middle Palaeolithic which ranges from 250,000 to 200,000 years ago (MIS 8/7) (Mercier et al. 2007). At this time, knappers were making pointed flakes and blades using a variety of prepared core methods (Hovers 2009: Table 1.1). A microwear and impact damage analysis of points from both caves shows that some artefacts were used as knives, others as spear points, and there is damage consistent with hafting (Shea 1993).

Impact Scars, Size, Shape, and Thinning The earliest claim for hafting comes from this category of evidence. The Fauresmith Smith site of Kathu Pan 1 in South Africa has already been mentioned for its 500,000 year old blades and points. The points, made on blades and flakes, have been examined in detail for macroscopic evidence of their use. An analysis of the location of edge damage visible to the naked eye on 210 points reveals a small percentage (13%) with damage to their tips, sides, and bases that is characteristic of impact (Wilkins et al. 2012: 943). A similar percentage had their bases thinned presumably to aid hafting. The symmetrical shape of the points plus the perimeter of the cutting edge formed by their tips (TCSP) make a persuasive case that these artifacts were hafted as spear tips. Further support comes from the experimental replication of the spears using the same local stone and hafted to

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shafts using acacia resin and tendons for binding. The spears were then fired from a crossbow into the carcasses of antelopes. The points penetrated the animals effectively and the patterns of edge damage resembled those seen on the archaeological specimens. This combined analytical and experimental approach makes a compelling case for spears as the earliest hafted tools, and overlapping in time the later Acheulean. The next oldest evidence comes from the European record and is associated with Neanderthals. Impact damage scars characteristic of spear use have been identified on four points from the site of La Cotte de Saint-Brelade in the Channel Islands (Callow and Cornford 1986: 298, 307–8). The site is correlated with MIS 6 (186,000–127,000 years ago) and is famous as an example of the flexibility of Neanderthal hunting strategies. A range of game was hunted during some periods of occupation and at others the focus was on the very largest animals that lived on the glacial stage grasslands: woolly mammoth and woolly rhinoceros. These megafauna were either driven up the narrow ravine at La Cotte, or over the cliff edge. Both options required cooperation among the hunters, and put the animals in a position where they could be killed with spears. The four pointed artefacts with impact damage scars are interesting for being thick and strong as well as sharp; just the kind of spear point needed to pierce the tough hides of the giant herbivores (Fig. 5.12). The stone points found in layers associated with the bones of smaller animals are also thinner and less robust. It looks like Neanderthals had different hunting tools to match their choice of prey and tactics, but this hypothesis needs testing by microwear analysis combined with experimental replication of the tools and their potential uses. At the late Acheulean site of Bouheben in southwestern France, thought to date to the early part of MIS 6, six spear points have been identified among a large sample of 125 pointed artefacts (Villa and Lenoir 2006). The spear points were recognized by a combination of measures including size, weight, impact scars, TCSA, tip angle, the presence of deliberate thinning at the hafted end (base), and by comparisons with the dimensions of spear points identified in younger African sites (Villa and Lenoir 2006). In the absence of microwear analyses, this kind of multi-stranded morphometric approach provides a reasonably robust set of observations on which to draw inferences about hafting and use.

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Fig. 5.12 A thick retouched spear point from the site of La Cotte de St Brelade, Jersey (United Kingdom), showing probable impact damage at the tip from use, and thinning of the base for hafting. (After Callow and Cornford 1986: Fig. 26.41.)

Just Points We now move down one more level in the hierarchy of certainty with the reliance on artefact form alone. This is especially the case with pointed pieces. As mentioned in the context of Sai Island, artefacts identified as spear points (based on impact damage) are by default assumed to have been hafted. The inferential chain is strengthened enormously with the support of microwear traces, adhesive residues, plus the package of the other indicators such as basal thinning, TCSA, and so on. When none of these is available, then we are left with the shape of the artefact and an understanding of how it was made as indicators of its possible use. Recall that the Levallois methods of making pre-shaped flakes, including pointed forms, were an established part of the technological repertoire of humans in eastern and southern Africa and across much of Eurasia in the latter part of the Middle Pleistocene. If, and it is a BIG IF, we assume that some Levallois flakes were made to be used as spear points—with or without further retouch—then the window opens for extending the time frame of hafting.

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In east Africa, Levallois points and retouched points occur in the Kapthurin Formation of Kenya in deposits older than 284,000 years (Tryon et al. 2006: 216). At the later Middle Pleistocene site of Cave of Hearths, in south Africa, there are four retouched points with thinned bases presumably designed for hafting, and another seven with impact scars on their tips (Sinclair 2009: 131). As suggestive as these sites are of hafting, they need supporting morphometric evidence (weight and tip shape) or ideally the combined power of microwear analyses, residue traces, impact damage, and tip-shape comparisons (Lombard 2006; Villa et al. 2009). The distribution of stone-tipped spears in Africa will certainly be extended as these complementary analyses are applied to more assemblages. In southwest Asia the Acheulo-Yabrudian Complex of the Levant (about 400,000–200,000 years ago) offers the potential for extending the regional and chronological record of hafting. At present, only the blade-based (Amudian) assemblages from Qesem Cave, Israel, have been examined for microwear traces of use, and, as you may recall, the results suggest that the blades were probably hand-held and used for cutting (butchering) and scraping (Lemorini et al. 2006). Further studies of Acheulo-Yabrudian assemblages, including those with more Levallois points, might reveal evidence for hafting. For now, the Middle Stone Age points from Tabun and Hayonim caves are the earliest well-supported examples of hafting in the region. More evidence for hafting from this period is in the pipeline with analyses underway of pointed artefacts from Misliya Cave, Israel. A preliminary report highlights the making of four different kinds of hafted points (based on size, shape, and impact damage) designed to hunt different sizes of prey (Yaroshevic et al. 2011).

Backed Pieces We move now to the next to lowest rung on the ladder of certainty, that of the presence of backing as a presumed indicator of hafting. In the absence of microwear and adhesive traces the blunting of an edge is a weak indicator of hafting. As seen in the case of the Amudian blades at Qesem Cave, the deliberately backed pieces

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improved the grip rather than the fit in a haft (Lemorini et al. 2006). The argument for hafting can be strengthened by making an appeal to size: the smaller the backed piece the more likely it might have been hafted because of the sheer difficulty of grasping the tool and using it effectively. That is essentially the argument made in favour of hafting existing in south-central Africa in the later Middle Pleistocene (Barham 2002). A few backed pieces have been reported from the sites of Twin Rivers Cave and Kalambo Falls, both in Zambia, in association with an early Middle Stone Age assemblage (Lupemban Industry, 266,000–170,000 years ago at Twin Rivers, Barham 2000). Also at Twin Rivers, in the Lupemban deposits, is an asymmetrical stone point with notches near its base that might have been a hafted knife (Fig. 5.13). Small backed pieces have also been reported from Sai Island, Sudan, and attributed to a Lupemban phase, that show evidence of impact damage (Rots et al. 2011). The Sai Island material aside, there is no other reliable evidence for the hafting of small backed pieces until much later in the African record (about 70,000 years ago, Lombard and Phillipson 2010).

Fig. 5.13 An asymmetrical pointed artefact (quartz) from the site of Twin Rivers Cave, Zambia. The piece has notches on either side of its base suggesting it may have been hafted, perhaps as a knife. The piece is 4.3 cm long. (Reprinted from Barham 2001: Fig.10.38 with the permission of the Western Academic & Specialist Press.)

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Hafting in Asia The astute reader will have noticed a glaring omission in our geographical coverage of the archaeological record—Asia. There is a simple reason for this: there is no microwear, residue, impact damage, or reliable morphometric data as yet from a single Middle Pleistocene site (Kashyap 2005; Costa 2012). The absence of evidence is partly methodological—such analyses are not yet routinely undertaken— and a reflection of the rarity of well-dated sites (Chauhan 2009: Dennell 2009). Despite these limitations there seems to be a genuine regional pattern that distinguishes the Asian record from that further west. The old Movius line comes to mind, but in this case it applies to prepared-core technology instead of hand-axes (Lycett 2007b). Recall that prepared cores were used to make cleaver blanks in the Acheulean of India (e.g. at Chikri), and the case was made that this integrative technology was one precursor to making pre-formed inserts for hafting. Levallois points (and bifacial points), however, are not common, and there is some uncertainty about their spatial distribution. They might be restricted to the northern (Himalayan) and western margins of south Asia (Costa 2012), or occur more widely with examples of bifacial points reported from the southeast of India (Gunjana Valley, James and Petraglia 2009: 261). The age of Levallois flake technologies is also poorly known (Chauhan 2009), and for the time being they appear to be relatively late by comparison with their African and Eurasian counterparts (mostly younger than 130,000 years ago) (Lycett 2007a; Mishra et al. 2010). Some tip cross-section measurements (TCSA) have been extracted from the published literature and reveal what appears to be a south Asian pattern. Pointed flakes from India are thicker and wider than those from southwest Asia, though a few lie within the range of known spear points (Costa 2012). Among the pointed pieces are also small hand-axes and cleavers that continue to be made in the Indian Middle Palaeolithic, long after they disappeared from the African and Eurasian records (Chauhan 2009). There seems to be considerable technological continuity between the Acheulean and Middle Palaeolithic in south Asia with prepared cores, blades, and small bifaces linking the two.4 4 The bout coupé or small flat-based biface found in northwestern Europe from 60,000 years ago (Mousterian of Acheulean Tradition) is not considered by many

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If we accept that stone-tipped spears were hunting tools in Eurasia and Africa, then their rarity in India and elsewhere in Asia suggests different patterns of behaviour reflecting local conditions and traditions. In some areas, large game hunting might not have been necessary as smaller less dangerous resources were available (Chauhan 2009: 135), in which case wooden spears or spears tipped with bone might have been more than adequate, and these are much less likely to survive in the archaeological record (Allchin 1963). It is only after about 35,000 years ago that hafting appears as an established part of the technological repertoire in the form of small backed blades (James and Petraglia 2005). The suddenness of this development may reflect the arrival of Homo sapiens from Africa along a southern coastal route across Arabia. Alternatively, there could have been internal development from an existing base of blade-making, but regardless of the process, the evidence suggests a relatively late adoption of hafting, at least on a wide scale. In east Asia there is no sustained tradition of Levallois technologies (Lycett 2007b), and as we might expect there is no evidence for the making of hafted inserts from pre-shaped flakes (Norton et al. 2009). The earliest evidence—at the moment—for hafting comes from northern China. Microwear analysis shows the presence of distinctive traces of hafting and use on retouched tools dating to just 11,000 years ago (Zhang et al. 2010). The stone inserts are interpreted as wood-working adze blades and projectile points or possibly knives. The lateness of hafting reflects in part a relatively recent and limited application of microwear research, but also a fundamental difference in the archaeological record compared with that of Africa and Eurasia. If modern humans (Homo sapiens) did enter south China as early as 100,000 years ago as has been claimed controversially (Liu et al. 2010, but see Dennell 2010), then they did not bring with them recognizable traditions of core preparation or the making of points. Much the same pattern holds true for southeast Asia where there is no Middle Palaeolithic tradition of making flakes or blades from prepared cores, even following the arrival of modern humans after 60,000 years ago. The inhabitants continued to make flakes, from large and small cores, using similar strategies to those first seen more researchers as an example of continuity of the Acheulean tradition, but instead a later independent development that probably served different purposes from the much larger hand-axe (see Villa 2009).

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than 800,000 years ago on Flores, Indonesia (Moore and Brumm 2007). On Flores, those strategies were used by H. floresiensis and by H. sapiens, who arrived just 10,000 years ago (Moore et al. 2009). The story is the same in island southeast Asia where H. sapiens settled as early as 40,000 years ago on East Timor, yet made stone tools similar to those found in the very early prehistory of Flores (O’Connor 2007). As a generalization, the southeast Asian record challenges our assumptions about the value of stone-tool technology as a direct marker of behavioural abilities and the movement of peoples and ideas.

Our Biases Revealed There is an altogether more subtle record here that demands a nuanced approach to disentangling patterns of change, especially when it comes to detecting hafting and its spread. On the Philippine island of Palawan, as elsewhere in the region, there is a long-lived tradition of making flakes with no patterned shapes or specialized forms (Pawlik 2010). A shift does take place towards making smaller flakes about 14,000 years ago, and that seems to be the marker of a fundamental change in how tools are perceived as well as made. The microwear analysis of a sample of these irregularly shaped flakes from the site of Ille Cave yielded some unexpected surprises—unexpected given our Western (African and Eurasian) preconceptions of what hafted inserts should look like. Among the relatively simple unretouched flakes there are some that show wear traces from use on hard materials (e.g. bone, wood, bamboo, and shell) and softer materials such as hides. Some also show the tell-tale signs of having been hafted (haft polish and residues of plant-based adhesives). There is compelling evidence, too, of the making of a stone-tipped projectile in the form of a triangular flake with impact damage to its tip, and polish and adhesives adhering to its base. It almost goes without saying that the projectile point was hafted. In terms of the archaeological record of the region, these findings add fuel to the debate about the rarity of recognizable stone-tool types across east and southeast Asia. As you may recall, some archaeologists have suggested that bamboo or wood filled the functions of stone tools, especially in areas where stone resources were lacking or of poor quality. This may have been the case in the earlier record, but

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the Ille Cave material (and that from other local assemblages with microwear traces of use, see Pawlik 2010) points to the likelihood that the much later shift to small flakes reflects the adoption of hafting. In which case, bamboo and wood became the supporting material for making shafts and hafts. The lesson learned here is that seemingly unpromising assemblages of flakes can reveal much about use and hafting, but unless we look for the evidence we will not find it, and microwear analysis is clearly a promising way forward. The now traditional focus of research on retouched tools (and unretouched Levallois pointed flakes) is understandable given the vast numbers of flakes often found in archaeological sites. It is a sobering thought, however, that we are likely to be underestimating the range of stone artefacts used, the kinds of activities involved, and the antiquity of hafting. Perhaps the European ‘small tool tradition’ will indeed provide early evidence of hafting once someone examines the material systematically and with microwear analysis.

THE OLDEST HANDLES, JUST MAYBE We have now looked at the evidence for hafting from stone tools, but there is one more source of evidence of great potential importance. The open-cast coal mine of Schöningen in northern Germany garnered widespread coverage in 1997 with the announcement of the discovery of the oldest known wooden spears in the world (Thieme 1997).5 In total, six exceptionally well-preserved spears 5 There is another wooden spear known from the European Middle Palaeolithic, and also from Germany. The Lehringen spear, which is dated to the Last Interglacial about 120,000 years ago, was made on yew, which is a durable and flexible wood when fresh. There is little doubt that this was a hunting tool, given it was found among the ribs of an extinct form of elephant with straight tusks (Elephas [Palaeoloxodon] antiquus). Its shape and weighting suggests it was probably used as a thrusting spear (Smith 2003). The sharpened tip and part of the shaft of what was probably a thrusting spear was found in 1911 at Clacton-on-Sea, England (Oakley et al. 1977). The Clacton spear came from peaty deposits associated with a mild interglacial, possibly MIS 11 (about 430,000 to 400,000 years ago), in which case it would predate the Schöningen spears. This makes it the oldest spear known, but it is still not a hafted tool. The age of the Schöningen sites is determined in part by correlating the environmental record of changing habitats with other long regional records, and then making broader links with the global record of marine isotope stages. At Schöningen there are also ages based on two dating techniques, thermoluminesence (TL) on burnt

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made of spruce, and one of pine, have been recovered from an organic mud deposited towards the end of an interglacial (site 13 II-4) (Thieme 2003). The age of the deposits is still being determined, but probably correlates with the end of MIS 9 (about 295,000 years ago) and the transition to MIS 8 (Urban et al. 2011). The climate was fluctuating between brief cool and then temperate phases as it moved towards colder glacial conditions. The spear-makers lived in a landscape of forests (pine and birch) with open grasslands and lakes. Herds of horse grazed on the grasslands and the remains of nineteen individuals of a now extinct species (Equus mosbachensis) were found with the spears. The bones show the tell-tale signs that they were butchered by humans using stone tools. The horses were probably hunted and killed with the spears, but it is hard to say whether the accumulation represents several separate episodes of hunting or a single mass kill. There are more signs of human activity on the lake margin including hearths, stone artifacts, and other kinds of shaped wooden tools.6 The spears have grabbed the headlines and deservedly so because they are more than just sharpened sticks. They show a clear understanding of the properties of the wood and a preference for spruce, but one was made of pine. The hardest part of the tree—its base—was shaped into a symmetrical tip and the spears were designed with the maximum weight and thickness located about a third of the way from the tip, giving a javelin-like profile (Thieme 2003: 11). There is still some debate about whether the spears were thrown or thrust and over what distances (e.g. Villa and Lenoir 2006: 115; Shea 2009: 824), but this matters little in terms of the planning involved in their making. The making of the spears involved cutting down individual trees and stripping them of branches and bark before shaping. An adze-like tool would have been useful, but there is no evidence from the stone artefacts of this kind of hafted tool. Instead, the chopping, stripping, and shaping of the woods was probably done using hand-held flake tools. flint and uranium-series analyses of peat deposits (Urban et al. 2011). Both have their limitations, but they do provide an independent check on the age ranges of the lakeside deposits. 6 The ‘hearths’ are currently being examined for the geochemical signatures of burning to ensure that they are indeed the product of human activity rather than burnt stumps or discoloured patches of sediment that do occur in waterlogged environments (N. Conard, personal communication). The discovery of a deliberately shaped stick with one charred end adds support to the argument that humans used fire, and this stick was found only 6 metres from two of the hearths (Thieme 2003).

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The most promising evidence for the use of hafting comes from the earlier site of Schöningen 12 dated to approximately 320,000 years ago (Urban 2011: 430). The inhabitants of this lakeside site lived during a warm interglacial in a landscape of deciduous forest with an abundance of large game. Associated with a range of small flint flake tools are the remains of straight-tusked elephant, rhinoceros, two species of bear, two types of deer, wild cattle (aurochs), and boar, with some showing cut marks from butchery (Thieme 2003). There is no evidence of fire here, but there are four wooden tools that have been described by the excavator as cleft hafts designed for holding small flake inserts. If these are indeed handles then they would be the oldest evidence so far for this invention. Three of the artefacts have clefts at one end and the fourth has clefts cut into both ends. The clefts are certainly of a depth and shape suited to holding some of the thinner flakes found at the site. They are standardized in that the base of the clefts are cut on a diagonal with the result that one end is lower than the other (Fig. 5.14 a, c). The diagonal could in practice give support as backstop to the insert if it was used in a downward-cutting motion with the force directed into the edge. There is standardization too in the choice of wood, which was silver fir (Abies alba), and in the use of branches from ‘rotten’ trees (Thieme 2003: 10). The branches were removed and the cleft cut into the hardest part, which is the base of the branch or knot. As handles and hafts these tools would only have been effective with the use of bindings to hold the inserts in place, with adhesive as an optional extra. The friction of the bindings on the wood should in theory have left some wear traces and the movement of the insert in the cleft should also have left its mark on the wood. These are the key pieces of evidence needed to move the Schöningen 12 ‘handles’ high up the hierarchy of certainty. Unfortunately, no microwear analyses have yet been done on either the exterior or interior of the clefts, and without this information these intriguing objects remain in the category of possible rather than probable tools. Regardless of whether they are handles, they remind us of the possibility that a range of organic components simply do not survive from the earlier record. There have been claims for the existence of deliberately shaped bone, antler, and ivory inserts (usually projectile points) in the European Acheulean and early Middle Palaeolithic, but none has withstood close scrutiny (Villa and D’Errico 2001).7 7 Neanderthals probably did make bone tools, but the evidence comes from late in their evolutionary history after 50,000 years ago (D’Errico et al. 2011). There is a

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Fig. 5.14 Three views of a possible ‘handle’ (side a, b, c) made of the trunk of a fir (Abies alba) from the site of Schöningen 12, length about 19 cm. The Vshaped cleft may have held a stone insert, and the cleft is cut at a diagonal with one end lower than the other. (Photographs # Lower Saxony State Service for Cultural Heritage [NLD], photos by Christia S. Fuchs.)

BIG QUESTIONS AND SMALL ANSWERS This chapter began with the statement that the necessary foundations for the invention of hafting were in place 500,000 years ago or so, but, as our hierarchy of certainty reveals, the earliest microwear evidence vigorous debate about the reliability of the association of Neanderthals with these and other technologies (e.g. bone and ivory tools, ornaments, and art) thought to be introduced with the settlement of Europe by Homo sapiens about 45,000 years ago (e.g. Benazzi et al. 2011).

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lies in the 280,000–180,000-year-old range. Why then such a long gap between potential and certainty and the earliest morphometric evidence from 500,000 years ago? The answer lies partly in the evidence and partly in the history of research. Given the importance of organic components involved in hafting, we may never be able to pinpoint a time and place of origin. The putative handles from Schöningen remind us how rare are the circumstances for the preservation of wood, and, in this instance, if it were not for strip mining the site would not be known to science. Such chance discoveries will continue to play a role in altering our perceptions of the history of technology. For some researchers the search for the origin of hafting is simply bad science, as the question can never really be answered given the vagaries of preservation (Shea 2011). The less pessimistic view taken here is that we need to review the existing evidence and develop research questions and analytical methods that not only reveal new sources of information, but also current conceptual and practical limitations. Schöningen also reminds us that the application of microwear analyses is in its infancy in terms of the search for hafting traces (see Rots 2010). Those asymmetrical clefts are crying out for examination, but there are very few researchers in this field and fewer still routinely searching for hafting traces. The seemingly unpromising flakes from the Philippine site of Ille Cave reveal a large blind spot in our assumptions about likely inserts for hafting. Our current focus on standardized pieces, either by retouch or from specialized cores, may mean we are overlooking an older tradition of selecting opportunistic pieces that suited the needs at hand. Only later were inserts designed to meet the ‘needs’ of the haft. That is speculation, of course, and a generalized one at that, but it can be tested by expanding the range of artefacts examined for hafting traces beyond the usual suspects. The list of suspects should also include hand-axes and cleavers of the later Acheulean. As far as I am aware, no one has yet examined these large cutting tools for hafting traces or residues. The one reported discovery of adhesives on bifaces from Tabun Cave, Israel (Gorski 2002), has not been published and the objects examined look like Middle Palaeolithic Levallois flakes rather than hand-axes (see Chapter 4, note 8). This one case aside, there remains a widespread assumption that hand-axes (and cleavers) were simply too big and thick to be hafted. The reconstructed haft and handle for the Sai Island adzes—which are bifaces—offers one possible arrangement that could cope with the large cutting tools of the Acheulean. Perhaps some of the more symmetrical and thin hand-axes were designed for

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inclusion and split hafts. Size and weight are not insurmountable barriers to hafting, as shown in the unlikely looking arrangement from Australia of a clamp haft, resin, and binder used to hold a ground stone axe blade (see Fig. 5.2f). Archaeologists familiar with the large groundstone axe blades of the European Neolithic (about 6,000 years ago) have no problem in accepting them as hafted tools, and similarly large axe blades are made today in Indonesia (Stout 2002) and inserted into wooden handles using an inclusion haft. The neglect of later Acheulean bifaces as potentially hafted tools may also reflect another bias in the search for hafted tools. As we have seen, there has been considerable effort invested in developing analytical tools for identifying projectile points as hunting weapons. That focus on spears may be diverting our attention from less exciting tools, like adzes, axes, knives, and scrapers, which all have roles to play in everyday activities including the making of other tools. If the Schöningen cleft pieces do turn out to be handles, then they were made for purposes other than for use as hunting tools. The invention of hafting may then have taken place in the realm of activities not directly linked to hunting. The ethnographic record gives us a clue to who were the potential inventors of hafting. Among contemporary societies reliant on big-game hunting, women are active in making and repairing tools, preparing meat, and scraping hides as well as building shelters, foraging for plant foods, and carrying goods between camps (Waguespack 2005). Given the wide range of activities they perform, women have a broad realm of expertise (craft knowledge) which is a foundation for innovation. Perhaps this division of labour emerged with big-game hunting in the later Middle Pleistocene along with the many other related social, psychological, and biological developments outlined in previous chapters, such as food sharing, an extended childhood, cooperative breeding, and so on. Layers of speculation do not take us far in addressing the question of origins, but they do highlight biases in our current approaches and limitations in the data. I expect that the time gap will close between the early potential for hafting and the solid evidence. That may come as a result of microwear research on some of the earliest examples of Levallois flakes and points from western Europe, southwest Asia, and eastern and southern Africa. Or it may come from broadening the range of tool types analysed to include hand-axes, scrapers, adzes,

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and, of course, the Schöningen wooden artefacts and associated small stone artefacts. We cannot locate with certainty a Eurasian or African centre of origin from which the idea of hafting then spread. No one site or region stands out as being far ahead of the rest in terms of the age of the evidence. The possibility of at least two independent centres of invention seems, for the moment, the more likely scenario given the separate trajectories towards prepared-core technology seen in Eurasia, Africa, and south Asia (see Chapter 4). This assumes of course that the standardization of flaking was linked to the designs of shafts and handles, and this widely held assumption still needs to be tested on a site-by-site basis. The south Asian record can contribute little to this debate for now, in the absence of well-dated sequences from the Middle Pleistocene. This large regional hole in the database extends eastwards where the absence of a recognizable tradition of pointmaking challenges our models of technological change. Given these many limitations, can we say anything meaningful about the possible link between the Middle Pleistocene Transition in terms of shifting glacial-interglacial cycles and the invention(s) of hafting? The answer, in brief, is no, not really. The core areas discussed in Chapter 4 as places of continuous occupation remain prime locations for the maintenance and further development of hafting as a tradition. They would also be the source areas from which the knowledge of hafting spread as previously abandoned landscapes were repopulated. Any attempt now to identify a particular isotope stage, either cold or warm, with the invention of hafting is not much more than an educated guess. In southern Europe we could point to the regular use of Levallois technology by the start of MIS 8 (about 280,000 years ago) (Moncel et al. 2011) as a potential marker, but microwear research undermines the automatic equation of this technology with hafting (Moncel et al. 2009). The remaining European evidence, excluding Schöningen, falls within the range of MIS 7 and 6 (about 240,000 to 130,000 years ago). This time frame also applies to the most reliable evidence for hafting from southwest Asia (Tabun and Hayonim caves) and northeast Africa (Sai Island). There are older points in eastern Africa (Gademotta, Kapthurin Formation) and especially in southern Africa (Kathu Pan) that rank lower on the hierarchy of certainty. We are left with the earliest evidence occurring well after the Middle Pleistocene Transition began (900,000 years ago), and in the case of Kathu Pan before 400,000 years ago (MIS

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11/MIS 10 transition) when the 100,000-year-long glacial cycle was firmly established with its maxima of cold and interglacial warmth. The search for a climate-based driver of invention is ultimately only going to lead to a partial explanation of why hafting was invented at a particular place and time. We know from our extended discussion of social learning theory that rates of innovation are highly dependent on population size, density, and the frequency of interaction between individuals and groups (e.g. Henrich 2004). Climate change plays a dual role of fragmenting populations and disrupting social networks as well as bringing people together by reducing obstacles to communication. Sophisticated quantitative modelling is needed to integrate ecological variables with climatic and demographic processes that operated on the Middle Pleistocene timescales. Initial steps in this direction are well underway (Banks et al. 2008). What can we say with certainty about the invention of hafting given the existing evidence? First, it happened in the later part of the Middle Pleistocene and probably after 500,000 years ago (see Table 5.3). Second, the technology is associated with Neanderthals in Europe and the Levant, and with late H. heidelbergensis/H. helmei/ or early H. sapiens in Africa. Third, the earliest evidence for the synthesis of plant-based adhesives (birch tar) occurs with Neanderthals (more than 187,000 years ago). Fourth, the controlled use of fire was integral to the development of vegetal adhesives. Fifth, the early use of hafting was applied to high-impact activities (spears and adzes). Sixth, the invention of hafting did not replace the use of hand-held tools. And seventh, even the simplest of hafted tools involved more technounits than hand-axes, and more actions and understandings. Less certain, but highly probable, is the assertion that inventors of hafting used the same neural networks needed to plan and make late Acheulean bifaces. Neuroimaging research (see Chapter 2) has revealed the structures and connections engaged when we think about and construct complex tools. The ability to plan many steps ahead was essential given the three basic components of hafted tools: the handle, the haft, and the insert. We can extend the speculation to include the activation of networks linked to creativity and imagination that draw deeply on the various forms of memory. The human mind with its capacity for abstract reasoning and ability to juggle multiple thoughts at once was needed to make an adze, knife, or hafted spear. The incorporation of complex adhesives synthesized

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from plants (e.g. birch bark tar) adds support to the hypothesis that the invention of hafting does herald the ‘modern’ mind in the archaeological record (Wynn 2009), in which case Neanderthals thought like us. From the perspective of combinatorial evolution, the invention of hafting was part of a continuum of innovation in which existing craft knowledge of stone, wood, bone, and other materials was used in a radically new way. The result was an emergent technology that became the platform for further innovation as we will see in the next chapter.

6 After the Revolution We are so accustomed to the rapid pace of technological change that it is hard to imagine an invention as fundamental as hafting not being an overnight success. But hafting did not replace handheld tools—we still use them today—and it took tens of thousands of years for the combinatorial principle to be applied beyond the initial range of cutting, scraping, and piercing tools. The first major development based on the combinatorial principle— the invention of the machine with moveable parts—took place after 100,000 years ago, probably in Africa. The new machines, the bow and arrow and the spear-thrower with dart, were complex multicomponent tools which harnessed stored energy and extended the power of the human arm. They improved the reliability of hunting and enabled communities to expand their diets with the result that human populations grew in size. These new weapons also gave a competitive advantage to their users, and may have been decisive in enabling the spread of Homo sapiens from Africa into Eurasia after 50,000 years ago. Another machine that may have been invented in the aftermath of the hafting revolution is the trap. Traps and snares harness stored mechanical energy and gravity. Their effectiveness ultimately depends on an understanding of animal behaviour as well as folk physics. The challenge for archaeologists is to find evidence for the use of each of these kinds of machines given they were largely made from perishable materials. In considering why the development and adoption of combinatorial technology was so slow, we first need to return briefly to the question of where hafting was invented, since this is interconnected with the other factors—population size, density, and rates of contact,

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social obstacles and shifting habitats linked to climate change—which affected the speed and extent of its spread.

CENTRES OF INVENTION REVISITED In the last two chapters we learnt that integrative technologies bring together two or more different areas of expertise in the making of a tool. The refined hand-axe found in some late Acheulean contexts may have involved not just a series of sequential and planned stages of manufacture, but also the use of other materials as soft hammers such as bone and wood. Prepared-core technology was also sequential in its planning and execution, but did not necessarily involve the use of materials with different properties. The case was made for the independent development in more than one place of preparedcore technologies from shared Acheulean foundations. The making of that useful tool, fire, certainly involved an understanding of the properties of organic materials combined with the folk physics of turning energy into heat. We have seen all these as precursors to hafting and they all existed in parts of Africa, Europe, western Asia, and south Asia—but one or more was missing in east and southeast Asia. In our hierarchy of certainty, there is little difference between the ages of the earliest reliable evidence for hafting in Europe, western Asia, and eastern Africa. The tar-covered flakes from Campitello, Italy, are about as old as the adze blades from Sai Island, Sudan, and the stone spear points from Hayonim and Tabun, Israel. They can all be attributed to the period from around 220,000 to 180,000 years ago (MIS 7). There are substantially earlier possibilities in the form of the Schöningen wooden ‘handles’ from Germany (MIS 9) and spear points from Kathu Pan, south Africa (around MIS 13/12). The handles remain in the doubtful category until proven otherwise, and for the moment the Kathu spears are the prime candidates for the oldest hafted tools known. The south Asian record drops from contention as a possible centre of invention, at least for the time being pending the application of microwear and residue analyses to artefacts from well-dated deposits. East and southeast Asia both appear to be on the receiving end of the spread of hafting from regions to the west (Fig. 6.1).

Fig. 6.1 The location of sites mentioned in the text: (1) Schöningen, Germany; (2) Campitello, Italy; (3) Bolomor Cave, Spain; (4) Dolni Vestonice, Czech Republic; (5) Mezhirich, Ukraine; (6) Hayonim and Tabun, Israeil; (7) Aduma, Ethiopia; (8) Sai Island, Sudan; (9) 6¼Gi, Botswana; (10) Sibudu Cave, South Africa; (11) Kathu Pan, South Africa; (12) Blombos Cave, South Africa; (13) Niah Caves, Borneo.

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Parallel Invention—a Surprisingly Common Process We have the evidence before us now of hundreds of thousands of years of technological development stretching from the later Acheulean to the Middle Palaeolithic—and what do we see by way of the process of invention and its spread? Before answering this question, we need to return to the intellectual school of the Sociology of Invention (see Chapter 1). W. F. Ogburn and his cohorts argued invention was a cumulative process that built on existing traditions, especially in small societies. In time ‘the stream of material culture grows bigger’ (Ogburn 1922: 73) as our knowledge base expands. They struggled, however, to explain the apparent suddenness of the Industrial Revolution without resorting to the influence of gifted and strong-willed inventors. These kinds of individuals are, of course, invisible to us in the Palaeolithic record. W. B. Arthur (2009) in his revival of the cumulative model set aside the individual inventor as the driver of change and returned instead to the stream of knowledge as an essentially faceless process of continuous change. Over time certain enabling innovations emerged that, once retained by social learning across generations, formed the building blocks of invention and a subsequent cascade of related innovations. The process of cumulative change might also lead to parallel and independent routes to invention based on similar social foundations. We are familiar with Darwin and Wallace converging on the concept of natural selection in the mid-nineteenth century. Great minds might think alike, but there is more to the process of convergence than just coincidence. William Ogburn and Dorothy Thomas published a paper in 1922 in which they examined 148 cases of independent invention in the fields of mathematics, astronomy, chemistry, physics, medicine, biology, engineering, and psychology. They found a surprisingly high occurrence of two or more people, often in different continents, having the same ideas at about the same time. There is nothing mystical about a good idea being ‘in the air’. The conditions favouring independent invention include a certain level of intelligence which exists in all human populations, but more importantly ‘cultural preparation’ plus cultural need (Ogburn and Thomas 1922: 82). Preparation refers to the existing knowledge of materials and how they work. It also includes an understanding of the appropriate social contexts of tool use. At any place and time this body of knowledge

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limits what inventions are feasible—the smartphone would have been unimaginable and impossible to make with the technological knowhow of the eighteenth century. Need, as the other part of the equation, is also a socially shared understanding and with a desired solution. Need on its own will not produce an invention, but it can bring together the cognitive ability with the technical and social knowhow to solve a problem. The probability of independent invention also increases as population densities grow. In the modern city, good ideas can move easily from mind to mind (Johnson 2010), and as cities grow the rate of innovation increases exponentially as knowledge spreads (Bettencourt and West 2010). The urban network of interacting minds also offers many more opportunities for storing information. Information storage—whether in the form of memory, writing, or the Web—is the basis of the ratchet effect of rapid cultural change. We have at our disposal more conceptual and practical tools for solving problems and meeting new needs. Hunter-gatherer communities lie at the other end of the spectrum of the pace and spread of innovation. We know that low population densities and limited social networks can undermine the ratchet effect, as was the case of Tasmania. Ogburn and Thomas (1922: 84) were certain nonetheless that independent invention occurred regularly in prehistory, though at a much slower pace given the limited development of contacts. They were less certain that archaeologists could distinguish between convergence and diffusion as the source of cultural similarities in the absence of written records. Fixed points in time were needed to identify the source and direction of movement of ideas. The invention of scientific dating techniques, like the radiocarbon method, has addressed that concern to some extent, though the dating resolution for the Middle Pleistocene remains poor. For now, we can say that the late Acheulean populations in parts of Africa, Eurasia, and south Asia shared a set of integrative (enabling) technologies that were the building blocks for the independent invention of hafting. They provided three essential kinds of cultural preparation needed for imagining and sharing this new technology: (1) familiarity with tools made in a protracted sequence of steps to achieve a distant goal; (2) knowledge of the properties of organic and inorganic materials; and (3) the social contexts that supported the learning of complex technologies. All three components of cultural preparation are embedded in craft knowledge. It is based on social

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learning and combines experience with tradition in the process of inventing practical solutions to perceived needs. If we assume that the large-brained humans of the Middle Pleistocene were similar to us in their cognitive abilities to imagine, plan, and make complex tools, then we have almost all the elements in place for independent invention. The final component is the identification of similarity of needs, and here we inevitably struggle. We cannot know in detail what social influences guided the decisions made by individuals in the Middle Pleistocene, and so we are left with the generalization that the (multiple) inventors of hafting all experienced worries about food, shelter, security, reproduction, and the welfare of their families. Comparable technological solutions arose from these common physical, social, and emotional needs. This might seem like woolly speculation but there is one more element of this package to consider—and that is time. The Middle Pleistocene offers tens if not hundreds of thousands of years for similar solutions to be found to similar problems among separate communities with roughly similar technologies. The work of Ogburn and Thomas points to the inevitability of parallel invention so long as the cultural foundations are in place.

Diffusion and Interaction We will never be able to pinpoint the time or place where hafting was invented because the archaeological record cannot provide these kinds of answers, but it can reveal the general patterns of technological change. As argued in Chapters 4 and 5 a limited number of likely centres of parallel invention can be seen in the time frame of around 280,000–187,000 years ago (MIS 8 and 7). New discoveries and the application of microwear and residues studies to older assemblages will probably extend the time range further into the Middle Pleistocene, as in the case of Kathu Pan, but for now the highest quality data point to this time frame and the likelihood of multiple independent centres in Africa, Europe, and southwest Asia (Fig. 6.2). Should future research prove this assessment to be wrong with only one early centre of invention (e.g. Lahr and Foley 2001), we still have to consider how the idea spread so widely. Social scientists have long been interested in how ideas and behaviours diffuse from one group to another. There are multiple academic traditions of diffusion research that

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Fig. 6.2 The location of potential independent centres where hafting was invented from a foundation of late Acheulean integrative technologies. Central Africa and India are possible additional centres, but their status is uncertain given the lack of good dating controls.

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have emerged within the social sciences since the nineteenth century (Rogers 1962). The approaches used by sociologists, economists, and anthropologists differ in the scale of the societies examined and in the analytical methods used, but for our purposes they can be simplified into two basic models about how innovations spread. The first is by the movement of people (demic diffusion) and the second by interaction between neighbouring communities (cultural diffusion). They are not mutually exclusive. Demic diffusion involves the spread of ideas within a community before part of that community splits off and moves elsewhere. There may be cultural barriers to the spread of a group such as language, traditions of marriage, and conflict. Physical barriers are also easy to imagine such as deserts, large bodies of water, mountains, and dense jungles, but as we know, the location and extent of these alter considerably during glacial-interglacial cycles and on the shorter timescales of millennial events. In the context of the Middle Pleistocene, biological differences between human species may also have had an impact on the kinds of interaction between an incoming and resident community. Cultural diffusion takes place between neighbouring groups through the exchange of goods, trade, and intermarriage. The nearer two groups are, the more likely they will interact and develop a working form of communication such as a pidgin language. Both processes of diffusion operated historically and probably did so on an evolutionary timescale (Collard et al. 2006). From the perspective of the invention and spread of hafting, we can expect the process to have been slow by modern standards given the low density of populations and more limited interaction. But we can also expect that core areas of continuous occupation during glacial cycles had higher population densities than their more marginal fringes (Hawkes 2011), and so were the likely source areas of invention and then diffusion by interaction and population movement. We identified likely core areas as the Mediterranean rim of Eurasia and north Africa, as well as parts of sub-Saharan Africa and south Asia. Testing these expectations of centres of invention and diffusion will be difficult given current limitations of dating methods and inherent problems of site preservation and mixing of deposits. There are, however, encouraging developments in the analysis of stone-tool technologies that can help reconstruct the process of interaction between incomers and resident communities (Tostevin 2007). The adoption of a new

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complex technology will be more successful if there is sustained interaction, and in the case of the hafting process we know that there are many understandings and actions that need to be learned. Shifting our focus from local to global processes of diffusion, there has been another area of promising development in recent years. Archaeologists are now applying the principles and methods of evolutionary biology to modelling how social traditions spread and how to recognize their movement across long distances. If we accept that the process of learning from others is analogous to the inheritance of genes across generations, then we have a potentially powerful tool for studying the development and diffusion of social traditions (Lycett 2010). The modelling works on the principle that behaviours, like genes, are passed from one generation to the next, though not just from parents to offspring. Behaviours vary within and between populations and they change as a result of the inevitable errors in learning that take place over the generations as well as from the acceptance of innovations. Population size, density, and rates of interaction play a critical role in the fidelity of the transmission of complex behaviours over time and space (Shennan 2001). These learning processes are analogous to genetic changes by mutation, random drift, and the loss of variability that occurs when populations decline (‘bottlenecking’) or split into small dispersed groups (‘founder effect’) (Manica et al. 2007). The quantitative methods used to construct evolutionary trees of ancestral populations and their descendants (‘phylogenetics’) are now being applied to the diffusion of stone-tool technologies. The spread of early Acheulean hand-axe technology has been modelled using this ‘phylogeographic’ approach with results that match well with what we know from the archaeological record (Lycett 2009). Recall that the oldest bifaces are found in Africa about 1.8 million years ago, with the next oldest finds in western Asia 1.4 millions years ago, and then a bit later in south Asia and western Europe. With phylogenetic principles as a guide we can expect that technological variability in hand-axe making will decline as a function of distance from the source population. A dispersing population size will decrease in size as it spreads, and as a result there will be fewer experts and learners to maintain the original diversity of technical knowledge. We can see this principle at work in the decline of modern human genetic diversity with distance from Africa, which was the ancestral source of Homo sapiens about 200,000 years ago

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(Ramachandran et al. 2005). Lycett’s comparison of variability in hand-axe attributes showed that African artefacts are more diverse, controlling for raw material differences, than those found outside the continent. The strong separation of African from non-African handaxes also supports the argument for diffusion of this technology by population movement rather than through cultural interaction alone. There is the potential in this approach to address the issue of the origin and spread of hafting. Most studies using stone tools have relied on comparing single artefact types, such as hand-axes or Clovis projectile points in North America (O’Brien et al. 2001). We do not as yet have a reliable proxy for the presence of hafting or for testing models of diffusion. The appearance of Levallois technologies is usually assumed by archaeologists to mark the invention or arrival of hafting, but we know from microwear research that flakes and blades from prepared cores were also used as hand-held tools. The presumption of hafting needs to be put to the test in each instance of a claimed first appearance. More daunting is the prospect that we are overlooking evidence of early hafting because of our preconceptions about the shape and size of likely inserts. As the microwear evidence from the Philippines has shown, irregularly shaped and unretouched flakes were hafted (Pawlik 2010). These artefacts might be classified as waste by most archaeologists. At the other end of the shape, size, and time spectrum, there is an inherent assumption that Acheulean bifaces were not hafted. Perhaps the label ‘hand-axe’ is to blame as it puts us into a particular mindset of a hand-held tool. We will struggle to model the diffusion of hafting for some time given our preconceptions and limited number of microwear studies of tools from well-dated contexts.

THE FIRST MACHINES There is one category of tool that lends itself well to the study of the diffusion of the combinatorial principle and that is the projectile point. We spent some time in the last chapter looking at indirect measures of tip size, shape, and edge damage that reflect the hafting of stone points as projectile tips. The tip-cross sectional area (TCSA) is one widely used measure, and it has a critical role to play along with microwear and residue analysis in the identification of the most

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significant innovation to follow the invention of hafting itself—the machine with moveable parts. You will rightly be shaking your head and wondering how we go from spears to machines, but there is an intermediate step in the form of the bow and arrow, the spearthrower, and the sprung trap. To recap, hafted tools offered significant improvements in efficiency and safety of use when compared with their hand-held counterparts, but they still relied entirely on human muscle power to work. The adze was an extension of the human arm and gave greater leverage and so force to the chopping motion. A handle on a knife blade gives the user a power grip and distances the hand from the cutting action. The coupling of brain with brawn took a new direction with the recognition of the power of stored mechanical energy (Cotterell and Kamminga 1990). That is a conceptual leap in the innovation of forms of propelled projectile points and in the making of sprung traps. The spear-thrower and bow and arrow thus mark a transition to the mechanized technology on which we rely so heavily today. The bow and arrow is a complex machine, as is the spear-thrower, as both have components that are designed specifically to work together as companion technologies (Oswalt 1976). The individual components do not function well as stand-alone tools. That is true of course for hafted tools in general, but an individual adze or knife blade can still be used in the hand without a handle (Hayden 1979). An arrow on its own, however, is a pretty useless weapon. Sprung traps also use stored energy and are made of parts that individually have little practical value. These early machines will now be examined in terms of their working properties and the archaeological evidence for their innovation.

The Basics of the Bow and Arrow We are all familiar with the bow and arrow even if only in passing through films or as a sport. This machine was invented by huntergatherers more than once and in more than one place. It had a wide distribution historically in the Americas, Europe, Asia, and Africa, but not in Australia where the spear-thrower was the only propelled weapon system. Spear-throwers were used in the Americas and in some areas, such as Mexico and in the Arctic, the two systems coexisted, but more often than not the bow and arrow was the weapon of choice for reasons outlined below. There is no

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ethnographic record of the use of the spear-thrower in Africa and Asia (New Guinea and Australia aside). For those wanting to know in detail the folk physics needed to make and use the bow and arrow there is no shortage of specialist knowledge gleaned from ethnographic, historical, and experimental research (e.g. Hamm 1991; Bergman 1993; Churchill 1993; Knecht 1997).1 What is clear from this body of knowledge is that making a lasting and effective weapon demands considerable understanding of the stresses and strains that affect the constituent parts and how they work together. The bow is effectively a two-armed spring put under tension by the bow string (Bergman 1993: 96). As the string is drawn the back of the bow bends under tension and the inside curve or belly is compressed. On release, the string transfers its stored energy and that of the two surfaces of the bow to the arrow. There are different types of bows suited for different hunting requirements and available raw materials (e.g. self bows, sinewbacked bows, and composite bows), but the simplest and probably the oldest form is the self bow made from a single piece of material, usually wood, chosen for its ability to flex under tension without breaking. There are complex folk physics involved in the shape of the belly and grip, the taper of limbs, and in the design of the nock for the attachment of the string. The making of the bowstring, arrow, and quiver represent other sets of understandings and the experienced bowyer will have command of the different kinds of tools and actions needed to produce these various components of the machine. The combinatorial principle comes clearly into play as this new complex tool generates its own web of supporting technologies. The number of separate components or technounits involved in making a sinew-back bow and arrow combination ranges from five to nine including the bow, sinew backing (optional), string (sinew or plant fibre), the arrow (main shaft, foreshaft), adhesive (optional), binding, point (optional stone or bone insert) and fletching (optional). If we add a quiver then the number increases by at least two. The combined package takes us well beyond the complexity of earlier hafted tools, but builds on the

1 There is an enormous amount of interest in archery among hunters, but also among devotees of the replication and use of all the components of traditional (primitive) hand-made bows and arrows (e.g. Hamm 1989). The Society of ArcherAntiquaries and the journals Primitive Technology and Experimental Archaeology are all good sources of historical and practical information.

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existing knowledge of the properties of handles, hafts, and stone and bone inserts (Lombard and Haidle 2012). If arrow shafts are made from hollow materials such as reeds or bamboo, then almost invariably a foreshaft is used to buffer the impact on the mainshaft to prevent it from splitting. This kind of composite hafting also applies to the making of dart shafts for use with spear-throwers. The effort and time invested in making this machine is well rewarded when compared with the more limited capabilities of a stone-tipped thrown spear. An archer can kill a wider range of animals, large and small, with greater accuracy and from a greater distance (Churchill 1993). A large self bow such as the English longbow can cast an arrow up to 200 metres (Bergman 1993) compared with the potential maximum killing range of 30 metres for a hand-thrown spear (Villa and Lenoir 2006). A quiver full of arrows offers many more chances to make a kill and arrows can be delivered rapidly from a range of positions. There is an added element of stealth as the archer can release an arrow without needing to stand upright, unlike in the case of the spear and the spear-thrower (Yu 2006). The bow and arrow is also particularly suited for hunting in forested habitats where visibility is restricted and game is often spotted by chance rather than stalked. An archer can respond quickly to a fleeting opportunity, and small arboreal game such as birds and monkeys become more accessible and reliable sources of food. The blowgun here deserves passing mention as a tool that is often associated in the imagination with forest hunters, but which was used historically in a range of habitats in the Old and New World (Blackmore 1971). This machine uses compressed air generated in a hollow tube (e.g. bamboo) to eject a tightly fitting projectile at speed and with accuracy. The projectile can be a poison-tipped dart or a hard pellet that kills by impact (Ventura 2003). The blowgun’s broad geographical distribution and similarity in design might reflect long-distance contacts from a single source area (Jett 1991). There is of course the possibility that similar needs and similar resources led to its independent invention in several places. It will be hard, if not impossible, to identify reliable archaeological signatures of blowgun use in the Stone Age. Returning to the bow and arrow, there is great flexibility in the design of the components to suit the needs of the hunt and availability of resources. In an extreme case of specialization the Agta peoples of the tropical forests of the Philippines make more than fifty different

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types of arrows (Fox 1952). The arrow shafts and tips are designed for the characteristics of the prey and their habitat. Long shafts are used to give greater accuracy in hunting birds and fish. Short shafts with stout detachable points are used in hunting deer and wild pigs in the dense forest. The arrowhead separates from the shaft on penetration and a cord keeps the shaft attached, which then acts as a drag anchor slowing down or stopping the prey as it catches on undergrowth. The Agta also use their bows and arrows for purposes other than hunting, including in ceremonies, games, dances, and for fighting. These weapons are truly multi-functional machines. In the semi-desert of the northern Kalahari the hunting of larger game puts a premium on mobility. Hunters need to be able to travel long distances in pursuit of game and a lightweight kit is carried comprising a small self bow and a quiver of short arrows tipped with poison. The use of poison compensates for the limited penetrating power of the bow. The arrow tip just needs to puncture the skin to deliver a lethal injection. Until metal became widely available, Kalahari hunters used bone tips and small stone inserts (microliths) hafted to the tip to form a lightweight cutting edge. Microlithic inserts can be arranged in differing configurations to suit the type of prey being hunted (see below). Microliths also economize on the use of stone, which might be a consideration in some landscapes (Elston and Brantingham 2002), and as arrowheads they can be made and repaired quickly (Yaroshevich et al. 2010). More generally, arrows do not need to be tipped with stone or bone points to be effective. A wooden arrow shaft can be tapered to a sharp point (‘self-pointed’) and if delivered from a large self bow it can be a very effective killing tool. If you want to avoid damaging the fur or feathers of small game, then a blunt-ended arrow will stun or kill and leave the body intact. As discussed in the last chapter, stone arrowheads can generally be distinguished from dart-points and spear points on the basis of size, weight, and morphology. As a rule, arrowheads tend to be smaller and lighter with corresponding lighter hafts and shafts (Brooks et al. 2006: 246).

The Neglected Spear-Thrower The spear-thrower by comparison is a less well-known and studied weapon system. The fact that archery is an Olympic sport but the use

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of the spear-thrower is not says much about the general neglect of this once widespread technology.2 Our understanding of the folk physics involved in using spear-throwers comes from ethnographic observations and experimental as well as recreational use. Also known as the atlatl (from the Nahuatl language of the Aztecs of central Mexico), the spear-thrower and dart use the principle of leverage to extend the throwing power of the human arm. The especially adapted dart (spear) has a cup-shaped base that fits into a hook on the end of the throwing board. (An arrow has a nock or slot cut to fit the bowstring.) The other end is held in the hand with the dart lightly gripped between the fingers (Fig. 6.3). The throwing board acts as a temporary handle which when swung overhand propels the dart into flight. Slow-motion photography of the throwing motion shows how the dart flexes through the arc and straightens as it is released with a sharp flick of the wrist (Cundy 1989, and see http://www.atlatl.com/ how-atlatls-work). The pronounced flex of the dart shaft may add some stored energy, but the contribution does not seem to be significant in increasing velocity (Cundy 1989; Baugh 1998). Also uncertain is whether the flex of the spear-thrower itself imparts any added stored energy into the shaft (Baugh 2003; Whittaker and Kamp 2006). Specialists also debate the advantages, if any, of attaching a stone weight (‘bannerstone’) to the underside of the spear-thrower (see Whittaker 2006 for a review). What is certain is that a dart shaft made of brittle wood runs the risk of breaking from the force of the throw and ruining the hunt (e.g. Gould 1969: 10). Misaligned components (foreshaft, mainshaft, and projectile point) will also cause the dart to break on impact or fail to penetrate the skin of the prey (Frison 2004: 58). There is no one standard length of throwing board, dart shaft, and projectile tip size. Each of these components varies according to the user, the size of the intended prey, and tradition. Observations of contemporary users of atlatls in sporting competitions show that it takes about two years of practice to become a competent user able to hit a standardized bullseye target at 20 metres. There is little difference in scores between adult men and women as body strength is not critical for accuracy (Whittaker and Kamp 2006). 2 The World Atlatl Association was founded in 1988 and has its own publication, The Atlatl, and it runs international sporting competitions annually where participants test their accuracy.

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Fig. 6.3 The atlatl (or spear-thrower) with dart about to be launched with an overhand throwing motion and a bent-knee posture. (Image courtesy of John Whittaker who retains all rights.)

In terms of the number of differing components, the basic atlatl incorporates six to eight technounits including the thrower, the dart (main shaft, foreshaft, fletching [optional]), stone weight (optional), adhesive, binding plus the point (Raymond 1986). The hook can be carved into the throwing board, or if a more resilient material is needed, such as antler, it can be hafted on using sinew and perhaps an adhesive, which increases the number of technounits. In central Australia the throwing board has other uses that support a highly mobile lifestyle. A stone adze blade is affixed to the handle end with a spinifex resin to make it into a woodworking tool. The spearthrower is also used in making fire to generate friction using the fire-saw method (see Chapter 4). The hunter on the move has a portable toolkit in hand with which to shape the spear shaft and to make a fire for straightening the shaft with heat. Even well-seasoned shafts can warp and twist with exposure to the elements and will need straightening. The broad and concave shape of the thrower makes it a useful tray, shovel, and musical instrument as well (Gould 1969: 79).

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Compared with the bow and arrow, the spear-thrower is more cumbersome and more difficult to master (Cattelain 1997). A hunter carries far fewer darts than does an archer with a full quiver, and so has fewer opportunities to wound or kill. Stealth is compromised by the need to deliver the dart from a standing and exposed position. An experienced user of the spear-thrower can cast a dart approximately 100 metres, but it is generally accurate at distances of less than 40 metres (Gould 1969: 79; Churchill 1993). Ethnographic observation suggests it is a weapon primarily for hunting small and medium-sized game, given the difficulty of placing shots with accuracy between the ribs of large game (Churchill 1993). The bow and arrow outperforms the spear-thrower on this account, as the archer can deliver a more accurate shot by sighting along the arrow (Frison 2004: 31 and 209). As might be expected, accuracy increases with proximity to the prey, and the ethnographic record shows that most hunting takes place at distances of less than 30 metres regardless of the weapon system (Hutchings and Bruchert 1997). To get that close to game with consistency requires a good understanding of animal behaviour, which in turn comes with observation, experience, and tuition. Social learning lies behind the making and use of these complex tools.

THE ARCHAEOLOGICAL RECORD OF THE FIRST PROJECTILE MACHINES Almost all the components of both these weapon systems are made of organic materials and so are much less likely to survive than the stone inserts used to tip darts and arrows. The few organic fragments we do have point to a late invention of spear-throwers about 21,000 years ago in Europe (Cattlelain 1989), and the even later appearance of the bow and arrow just 11,000 years ago and also in Europe (Bergman 1993) (Fig. 6.4). This evidence supports long-held assumptions that the simpler technology of the spear-thrower was invented before the more demanding bow and arrow (Knecht 1997). As we have seen, the two technologies are based on different propulsion systems and there seems to be little logic in deriving the bow directly from the spearthrower. It is possible that they are equally old. The patchy organic

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Fig. 6.4 Replicas of the English longbow (held) and the 8,000year-old Hölmgaard bow (on the fence and beyond).

record cannot help us resolve this issue. In the case of Australia we have abundant ethnographic data on spear-thrower use (e.g. Hutchings and Bruchert 1997), but almost no surviving archaeological examples. The best historical evidence for changes in spear technology comes from painted images in rock shelters that show details of darts and throwing boards (Morwood 2002). We cannot say with certainty whether the spear-thrower was invented independently in North America or whether it was brought with the first settlers who arrived from northeast Asia more than 15,000 years ago (Waters et al. 2011). The absence of spear-thrower technology in eastern Siberia (Cattelain 1997) suggests multiple independent inventions in the Old and New Worlds, but of course absence of evidence does not mean evidence of absence. The same logic applies to efforts to chart the origin and spread of the bow and arrow using just organic remains. The antiquity of both weapon systems is likely to be older than previously thought and the only way to test this assumption is to turn to the much more abundant record of stone projectile points. They hold the clues

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needed to examine when, where, and how these inventions took place and then spread. The answers to these basic questions are needed if we are to understand the dynamics of social change in the aftermath of the hafting revolution. Rapid progress is being made in this growing sub-field of projectile-point research, and it is being applied in Africa, southwest Asia, and Europe. We are already familiar with the analytical methods used to identify hafting traces on stone tools through microwear and residue analysis, and with the range of morphometric measures used to distinguish hand-held spear points from dart and arrow tips (see Chapter 5). To recap, measurements were made on museum and archaeological specimens of hafted arrowheads and dart points to define the size ranges and means of each tip, which could then be applied to stone artefacts of unknown function (Thomas 1978; Shott 1997; Shea 2006). Experimental replication research has also been incorporated into the analytical mix to generate independent data on the performance of points of differing shapes, sizes, weights, and raw materials (Lombard and Pargeter 2008; Sisk and Shea 2009). A recent re-analysis of African (Middle Stone Age) points using tip cross-section area (TCSA) and tip cross-section perimeter (TCSP) revealed some overlap in dimensions with dart tips, but not arrowheads (Sisk and Shea 2011). These results do not mean that spearthrowers were necessarily in use, but they complement an earlier comparative study of African points that found indirect evidence for the use of spear-throwers (Brooks et al. 2006). The small size and light weight of some points, particularly those from the sites of Aduma, Ethiopia, and 6¼Gi, Botswana, fall within the range of ethnographic dart points. Both sites are older than 70,000 years ago, and if spear-throwers were in use at this time (MIS 4) then they were eventually abandoned as there are no historical traces of their use on the continent.

Bow-and-Arrow Hunting in the Howiesons Poort The bow and arrow probably replaced the spear-thrower in Africa and there is indirect evidence for this transition in the archaeological record after 40,000 years ago. The small bifacial points found at Middle Stone Age sites such as Aduma gradually disappear from the archaeological record between about 40,000 and 20,000 years

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ago (Barham and Mitchell 2008). Microliths take their place as hafted inserts for all sorts of tools including projectile tips. The African ‘Later Stone Age’ marks this technological transition and it is widely assumed by archaeologists that the bow and arrow came into widespread use at this time (Ambrose 1998). There is actually very little certainty behind this broad assumption in the form of microwear and residue traces. Instead, we rely on recent ethnographic parallels of arrows tipped with microliths and the few traces of hafting and impact damage that do support the inferential link. There are also cases of microliths found embedded in human skeletons from Later Stone Age sites along the Nile dated to 19,000 and 12,000 years ago. Considerable force was needed for these small pieces of stone to penetrate bone, which suggests the use of the bow and arrow (Wendorf et al. 1986). These nameless victims of conflict remind us that projectile technologies were not just tools for getting food. They offered a real competitive advantage to those who used them expertly. We will return to this point later when considering the broader impact of the invention of these weapon systems. The evidence for the early use of the spear-thrower in Africa is based largely on morphometric analyses of stone points. In our hierarchy of certainty this category of evidence comes one notch below that generated by wear and residue traces on individual artefacts. Ideally, the two should be combined where possible and this integrated approach is being applied in southern Africa to microliths from Middle Stone Age sites. The results have been startling and controversial. The claim has been made that the bow and arrow was in use in the region 64,000 years ago, well before the start of the Later Stone Age (Lombard and Phillipson 2010). The candidates for the honour of oldest arrowheads are microliths from sites attributed to the Howiesons Poort industry of southern Africa. The Howiesons Poort is remarkable for the sudden appearance of microliths 64,000 years ago that were made on small blades, and for their equally rapid disappearance 59,000 years ago. This brief interlude of technological change follows another in which flakes were carefully retouched into bifacial leaf-shaped points. The points are markers of the Still Bay industry, which is another short-lived tradition that lasted from around 74,000 to 71,000 years ago. Evidence for hafting has been found on these points (microwear, patination, resharpening, and breakage patterns), and patterns of impact damage indicate that they were used primarily as spear tips, though they could have

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functioned as knives (Lombard 2007; Villa et al. 2009). The Still Bay industry as represented at the site of Blombos Cave, on the Cape coast, is associated with other innovations including the making of shell beads, pointed bone tools, and the engraving of ochre. The site was also a workshop where points were made for use elsewhere (Villa et al. 2009). The making of these points involved three phases and the high proportion of production failures at Blombos shows the level of skill needed to produce the finished article, which is thin and symmetrical. Still Bay points come and go in an archaeological blink of the eye, as do the Howiesons Poort microliths. This pattern of rapid turnover with its apparent loss of knowledge seems odd, assuming that technological change is, on average, a cumulative process. We have talked before about the ratchet effect of cultural evolution with innovation, social learning and language being the basis for leaps in complexity. Yet here we have leaps that then disappear from the collective pool of knowledge. Perhaps these early innovators were not fully ‘modern’ in their thinking (Klein 2001) or alternatively they were modern in the sense of being extremely adaptable in the face of changing environmental and social circumstances (Deacon and Wurz 2001; Jacob and Roberts 2009). These sharply differing perspectives reflect an ongoing debate about what constitutes behavioural modernity and its archaeological expression (see Shea 2011 for a summary). If we take the long view, Still Bay and Howiesons Poort industries reflect the great flexibility in tool design that hafting allows. The Big Idea of making tools from multiple components is not abandoned—it is amplified and applied in new ways that meet immediate needs, desires, and changing traditions. The argument has been made that these two industries are local cultural responses to shifts in resources and population pressures ultimately driven by climate change (Jacob and Roberts 2009). These industries fall within MIS 4 (around 72,000–60,000 years ago), which is characterized by cool moist conditions around the coastal margins of southern Africa (Chase 2010). This region might have been a refuge for populations at a time when the interior was drier and less hospitable. Higher population densities along the coast may have stimulated innovations including the use of symbols to signal group identity and territoriality. Climate change also might be linked to the end of the Howiesons Poort as a return to wetter conditions at the onset of MIS 3 (about 60,000 years ago) led to groups resettling the interior (Mitchell 2008). As a result, the social

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networks needed to maintain a complex technology like the bow and arrow were disrupted and the knowledge was lost (Lombard and Parsons 2011). There is precedence for this hypothesis of cultural simplification in the case of Tasmania, and given the high quality of archaeological and climatic data available from the region it may well be possible to put this speculation to the test in the near future. The evidence for bow-and-arrow technology existing in the Howiesons Poort comes largely from the site of Sibudu Cave, South Africa. The microliths were analysed for their size and shape, evidence of impact damage, and for residues of hafting and use. Depending on how the microliths were hafted, the tip cross-section area (TCSA) measure shows they fall within the size range of ethnographic arrowheads on width alone, but if they are mounted transversely so that the cutting edge is perpendicular to the shaft (Fig. 6.5b) or back to back (Fig. 6.5c), then only few are small enough to be arrows and the rest are darts or spears (Lombard and Pargeter 2008; Wadley and Mohapi 2008). The importance of the transverse

Fig. 6.5 Replicated arrangements of Howiesons Poort microliths: (a) longitudinal; (b) transverse; (c) diagonal; and (d) back-to-back. (Courtesy of Marlize Lombard who retains all rights.)

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arrangement is that it has been shown experimentally to be very effective at penetrating deeply into a carcass without the tip breaking (Yaroshevich et al. 2010). Other arrangements are equally effective including a microlith mounted diagonally to the shaft (Fig. 6.5c), vertically (longitudinally) (Fig. 6.5a), or as a barb on the shaft of a self-pointed arrow. The location of hafting residues (plant adhesives) shows that all these configurations were used (Lombard and Pargeter 2008). When combined with preservation of animal residues on the cutting edges (e.g. hair, fat, blood, and collagen), these data provide persuasive evidence that many of these tools were used as hunting weapons. The smaller microliths were probably used as arrow-points, but, as others have noted, they could have been used as tips and barbs on spear-thrower darts (Villa et al. 2010). A bone point from Sibudu has been interpreted as a possible arrow tip used to hunt small prey and adds some support to the argument in favour of the bow-and-arrow argument (Backwell et al. 2008). The habitat around Sibudu included areas of closed forest, and as we know, the bow and arrow is more effective than spear-throwers in this kind of environment. There is a case to be made too for the use of traps to catch small game in such a setting, as will be discussed shortly. On balance, the hunters of the Howiesons Poort era probably used stone-tipped spears—a now ancient technology—along with one or both systems of mechanical propulsion. If the spear-thrower alone existed, then the southern Africa data adds support to a widespread African tradition with regional variants in the making of dart tips. If the bow and arrow existed too, then not only did it long pre-date the Later Stone Age proliferation of microlithic industries, but also the likely use of microlith-tipped arrows in the European Upper Palaeolithic.3 The apparent loss of the bow-and-arrow tradition after the Howiesons Poort remains an enigma, especially given that this technology offers great accuracy and portability. The answer to this riddle may lie in the technological patterns that emerge after 60,000 years ago, and these remain to be examined in detail (Villa et al. 2010).

3 The Gravettian industry of the Upper Palaeolithic contains backed microliths (‘microgravette points’) that are thought to be hafted as arrow tips (Hays and Surmely 2005).

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A Competitive Advantage on a Grand Scale At least one new kind of projectile system was invented in Africa more than 70,000 years ago which incorporated stone points as hafted tips. That is the conclusion to be reached from the evidence above, which leads us to consider briefly its evolutionary implications. Either machine would have given a competitive advantage to those communities who had it over those who did not. The ‘haves’ enhanced their effectiveness as hunters by broadening the range of animals that could be killed and by reducing the risk of injury as more distance could be put between the hunter and hunted. As a result the individual hunter increased the likelihood of providing food for his offspring and of living long enough to transmit his knowledge to his children and perhaps their children. If we scale up the individual advantages to group level, then the collective sharing of game increases food security for all with potential long-term consequences. As infant and adult mortality drops, then population size grows. A larger population brings increased opportunities for social learning from peers, elders, and unrelated individuals. Rates of innovation can increase that in turn may improve food security, which then feeds back into the cycle of learning, innovation, and growth. The cycle can be expanded to include other elements of the biological and social foundations of innovation discussed earlier. Improvements in food-getting technologies can alter the social and population dynamics in favour of the ‘haves’ over the ‘have nots’. This is the basic model proposed by archaeologists John Shea and Matthew Sisk (2010) to explain the spread of Homo sapiens from Africa into Eurasia after 50,000 years ago and for the extinction of Neanderthals. They measured stone points from African and southwest Asian sites using TCSA as the indicator of trends in technological change. The results support the following sequence of developments. The ‘haves’ developed mechanically projected weapons in Africa between 100,000 and 50,000 years ago with stone and bone points. Populations grew on the continent, spread into the Levantine corridor and then into Europe, where they encountered the ‘have not’ Neanderthals who still relied on the hand-thrown spears for hunting and protection (e.g. Villa et al. 2009). The result was ultimately one-sided. As well as being out-gunned in any direct encounters, Neanderthals lost out in the long-term competition for resources. The new weapon systems were simply more effective and less risky than the now old-fashioned

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spear when it came to hunting big game. They also gave H. sapiens more reliable access to small game in a wide range of settings including woodlands, grasslands, and along coasts. In time, these betterequipped hunters filled the landscape at the expense of the indigenous human population. There is support for this argument in the archaeological record of southwestern France, which was once a core area for Neanderthals during harsh glacial phases. Once modern human groups settled in the region their population grew quickly in size and density (Mellars and French 2011). They were also more successful as hunters, bringing substantially more meat to campsites than their competitors. There is a whiff of ‘how the west was won’ in this story of ultimate technological superiority, but there are the related questions of why Neanderthals lacked these weapons in the first place and why they did not manage to learn how to make them from their new neighbours. Sisk and Shea (2010) think the answer lies in their biological adaptation to the colder conditions of glacial Eurasia and not in their lack of cognitive abilities. Neanderthals had evolved a higher metabolic rate than ourselves, required more calories per day to survive, moved often and in small groups with limited social networks, and in general their population densities were low (Verpoorte 2006). As we well know, these are not conducive conditions for inventing and retaining complex technologies—the synthesis of tar being a notable exception. Tools needed to be made quickly and easily repaired to meet the demands of a transient lifestyle. Neanderthal groups could not devote the time to thinking about or learning new complex weapons systems. The small size of local communities also limited the pool of expertise and the ability to produce and retain innovations. Only late in the Neanderthal record do we see new forms of spear points being made including backed pieces, and these innovations might have been an attempt to improve a technology that worked in the face of a dwindling resource base. Neanderthals focused on the hunting of large game rather than broadening the range of foods eaten (Sisk and Shea 2010: 115). It was a strategic mistake in hindsight, but perhaps they were ultimately doomed in this unbalanced competition for resources (Banks et al. 2008). This is an appealing story in that it puts technological innovation in the starring role as the driving force in the extinction of one species and the success of another, which just happens to be ours. But from a scientific perspective, it has the advantage of being testable given the

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quality of the European and Levantine records. Outside Eurasia, we have little evidence for the spread of these technologies into south Asia until 36,000 years ago. Microliths are found in India and Sri Lanka, which could signal the arrival of H. sapiens (along with beads, burials, and bone tool-making) (James and Petraglia 2005; Perera et al. 2011). The use of microliths as dart or arrow tips, however, still remains to be demonstrated. Further east, the equation of complex weapons technology with the dispersal of modern humans breaks down. The earliest substantial shift in stone-tool technology across Sahul at this time takes the form of hafted hatchets or adzes with the edges ground to make a smooth cutting surface presumably for wood-working (Habgood and Franklin 2008; Geneste et al. 2012). Microliths and stone points make a much later appearance. Bone tools appear as early as 45,000 years ago in southeast Asia (Niah Caves, Borneo), but hafted bone points are also much later (Rabett and Piper 2012) (Fig. 6.6). Perhaps there was a gradual loss of technical knowledge or cultural drift as dispersing populations declined in size with distance from an

Fig. 6.6 (a) A sting-ray spine from Niah Caves, Borneo, showing the tapered end shaped to fit into a joint attached to a shaft or handle (5 cm scale); (b) close up view of the ridged surface of the hafted end with fragments of the surviving adhesive bearing traces of the binding materials (at right angles). (Photos by Ryan Rabett and reproduced with his permission; original analysis by Huw Barton, Phil Piper, and Ryan Rabett.)

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African homeland (Mellars 2006). This would be the founder effect discussed earlier, but others see a very different record of complex behaviours that mark the arrival of modern humans, though not with mechanical weapon systems (e.g. Habgood and Franklin 2008). They applied their behavioural flexibility in different ways in response to local conditions that changed markedly with shifts in climate, vegetation, and sea level. In the context of southeast Asia generally, there is also the presence of local communities to be considered with their own long-lived traditions of tool-making. The processes of diffusion by interaction and by the movement of people both presumably took place across this vast region with locally varying results.

THE ABSENTEE HUNTER One more kind of food-getting machine—the trap—was invented in the aftermath of hafting. Archaeologists often overlook the use of this class of tool by prehistoric peoples because the direct evidence simply does not exist, except in rare cases of exceptional preservation. Before the use of metal, traps were made of organic materials, typically wood and string. Neither is likely to survive and if they do their use as traps may not be obvious as the technology is deceptively simple in terms of its components. The planning and setting of traps is the complex part of this technology, and those ephemeral behaviours leave the merest trace. The evidence is necessarily circumstantial as it is drawn from animal bones, in particular from the diversity, size, age, and likely behaviour of the once living creatures (Lupo and Schmitt 2005). Ethnographic observations give the necessary analogical link between particular trapping strategies and patterns seen in the archaeological record. It almost goes without saying that the archaeologist also needs to be aware of how the archaeological deposits formed and what other predators might have been involved in contributing bones to the assemblage. Arguments in favour of hafting also require good evidence of the structure of past habitats combined with an understanding of the social and feeding behaviours of likely prey. The resulting inferential chain is long with many potential weak links, but it is worth risking this level of uncertainty because these tools engage similar complex cognitive processes to those used in hafting (Wadley 2010).

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There are three basic types of trap found widely in the ethnographic record, and a brief description of each gives a sense of the thought processes (understandings) needed in their planning and setting. The snare, deadfall, and pitfall trap are designed to work automatically without human intervention, and in this sense they are more machine-like than either the spear-thrower or bow and arrow.4 Traps are usually set away from camps and along animal trails, and at the entrances to dens or burrows. They are particularly useful for catching small elusive prey that is otherwise inaccessible with other hunting technologies (Stiner et al. 1999), but large game can also be trapped without the risks and effort of a hunt. Regular checking and resetting has the potential to generate a reliable supply of animal protein. Even hunters of large game, such as the Hadza of Tanzania, will set traps for small animals to ensure there is meat in the pot between successful hunts (Gurven and Hill 2009). Small game is usually eaten by the trapper’s family rather than being shared communally, which is an incentive for all family members to take part. The trapper might be a child or an adult of any age, because strength and speed are not limiting factors, especially with small prey. There is little risk in collecting a rabbit from a snare compared with facing a wounded buffalo. Setting and checking a trap can be the work of an individual or a small team, depending on the complexity of the design and size of the prey caught. Removing a bear from a deadfall trap runs the risk that it might still be alive, in which case it needs to be dispatched with a spear or club, not a job for children. Teamwork might also be needed to butcher and carry a large carcass back to camp. The choice of trap is not necessarily limited by the size of prey, but there may be practical considerations in terms of the effort involved. A pitfall trap designed to catch a hippo requires substantially more digging than one intended for a small antelope. Group mobility may also be a factor in deciding to use traps. Highly mobile huntergatherers following migratory herds might not have the time, the need, or local knowledge to make the setting of snares worthwhile (Wadley 2010: 182). The descriptions that follow are based on

4 The trapping of small birds and rodents using sticky substances is widespread ethnographically and sometimes these substances are used as bait in sprung snares (e.g. Fox 1952).

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ethnographic observations from the woodlands of North America. For an overview of trap use in Africa see Wadley (2010: 180–1).

Snares, Deadfalls, and Pitfall Traps A snare is a loop of cordage (vegetal or sinew) placed across an animal’s path that tightens around its foot, neck, or body (Fig. 6.7a). The snare can be static or sprung, with the latter using the stored mechanical energy of a bent pole held in tension by a trigger. The noose in a static snare is attached firmly to a tree or log and tightens as the animal struggles to get free. With the sprung snare, the animal’s (a)

(b)

Fig. 6.7 (a) A sprung snare trap, and (b) a deadfall trap. (After Stocking 1915 and Harding 1954.)

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initial struggling releases the trigger and the pole straightens, lifting the animal off the ground. It might be killed by strangulation. There are variants of each, but as traps they are effective for catching animals of all sizes from rabbits to bears, as observed among North American groups (Cooper 1938). Fish can also be trapped using a similar principle, with basketry traps designed to let fish in but prevent their escape. These can be operated remotely by placing them in tidal areas or at the confluence of a river and lagoon. The deadfall trap uses gravity to do the work of immobilizing or killing an animal with a heavy falling object such as a log or stone (Fig. 6.7b). One end of the weight is propped up and released by the animal touching a trigger stick as it passes beneath the weight or pulls on a baited trigger. As with snares, deadfalls can be used to catch some of the smallest and largest game (Irwin 1984). The pitfall trap also works using gravity, but in this case it is the animal’s weight that is the active element. A pit is excavated to a depth that prevents escape, in which case the animal is usually alive when the trap is checked. Alternatively, sharpened stakes might be set in the base to impale the prey. The pit can be placed across a trail and concealed with a thin covering or left open with bait to lure in the prey. Obviously, the larger the intended prey the bigger and deeper the pit needs to be. Each trap design involves an understanding of cause and effect tailored to the size and habits of the intended prey, available materials, and the structure of the habitat. In the case of sprung snares and deadfalls there is additional knowledge invested in the making of sensitive trigger mechanisms, which requires skill. An experienced trapper will know the seasonal movements of animals and where best to place a trap, or how to artificially direct the movement of prey towards the trap by constraining the path. The number of technounits involved in traps can be as few as one (a simple pit), but it is the sequential planning that links traps with the cognitive aspects of hafting. With snares there is the added similarity that two or more different materials are used to make a functioning whole (the cordage and the attachment or sprung pole and possibly the triggers). We can speculate that the same shared neural networks in both hemispheres are engaged in making traps as are probably used in hafting. The planning, making, and setting of a trap also involves the elements of constructive memory needed to envisage a future event and execute

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the steps to achieve the goal. The start and finish may be separated by hours if not days.

Archaeological Traces The oldest undoubted traps are those used by Mesolithic communities of northern Europe to catch salmon and other large fish 9,000 years ago and later. Direct evidence of traps is lacking before this time. Impressions of twisted cordage have been found in 26,000-yearold clay deposits in central Europe (Dolni Věstonice, Czech Republic) (Soffer et al. 2000), and in theory these could have been used for making snares or woven into fish traps. Possible trap components made of bone (triggers) have been found in the Ukraine (Mezhirich) dated to 18,000 years ago (Hoffecker 2005). The use of traps is also inferred from the occasional abundance of rabbit and fox bones in Upper Palaeolithic sites. Neanderthals may also have used traps to catch small game. Rabbits were being eaten as early as 350,000 years ago (Bolomor Cave, Spain), but their method of capture is uncertain (Blasco and Fernández Peris 2012). The most detailed and persuasive argument for the early use of traps comes from the analysis of the animal remains from Sibudu Cave, South Africa. Sibudu is the focus of claims for the use of microliths as tips for spears, darts, and arrows 64,000 years ago, and to the list of firsts we might consider adding traps. The excavator, Lyn Wadley (2010), knits together an argument in favour of traps based on four lines of evidence: (1) the wide range of small animals found in the Howiesons Poort including monkeys, rats, rabbits, and hyraxes; (2) the prevalence of elusive forest species (particularly the small blue duiker antelope); (3) the broad age range of the animals (juveniles and adults), which is typical of trapped rather than hunted prey; (4) the prevalence and range of small carnivores, which are otherwise difficult to catch (e.g. mongooses); and (5) the presence of the dangerous bush-pig, which might be best trapped rather than hunted. There is large game in the deposit too, such as zebra and buffalo, and these more open landscape dwellers were probably hunted using the bow and arrow, spears, and spear-throwers. The bow and arrow has its uses in closed forests, as the ethnographic record of the Agta reminds us, but Wadley suggests that traps were a better use of time for catching blue duiker than pursuit with a bow and arrow.

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The legally minded reader may find all this circumstantial evidence unconvincing, but there is the added supporting twist that late in the Howiesons Poort, as the climate became drier and forest species declined in abundance, there is a shift in strategy towards hunting large adult game. The microliths cease to be made, marking a shift in weapons back to spears and perhaps darts. The Howiesons Poort and earlier Still Bay levels are still being excavated at Sibudu, and as the sample of animal bones increases the trapping argument might be refined further. For now, this case study is the clearest articulation of the indirect evidence for trapping, and for it existing far earlier than the surviving remnants of traps. Last but not least, it is worth recalling the four wooden artefacts from Schöningen 12 with their V-shaped notches, and in particular the one specimen that was notched at both ends (Thieme 2003). Could these have been parts of triggers rather than the handles of hafted tools? The animal remains from the site included small game such as a beaver-like rodent and water voles. An argument based on circumstantial evidence could be made for the early use of trapping at this lakeside site, and it would need to start with evidence that these animals found their way into the assemblage as food rather than as accidents of preservation.

THE LASTING IMPACT OF THE FIRST MACHINES The spear-thrower, bow and arrow, and traps all have their roots in the combinatorial principle and ultimately in the invention of hafting. Although the time and place of their respective origins remain the subject of informed conjecture, there is no doubt that these new technologies improved the reliability of hunting. They extended our cultural niche as tool-assisted hunters and enabled us to spread into previously uninhabitable environments or to make a more comfortable living in existing habitats. Recall the poignant case of a group of Polar Inuit in the mid-nineteenth century who were close to starvation following the loss of the expertise needed to make bows and arrows and spear-throwers. They could no longer hunt and fish effectively in a harsh environment (Boyd et al. 2011). The modern equivalent is the colonization of space—life on the International Space Station would be impossible without the extended network of

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Improved hunting technologies

Increased potential for social learning

Population growth

Fig. 6.8 A simplified model showing the linked impact of the invention of mechanical propulsion devices on population growth, social learning, and rates of innovation.

expertise that designed, built, and maintains this artificial habitat. By contrast, the loss of bow-and-arrow technology at the end of the Howiesons Poort about 60,000 years ago probably did not mean extinction for local communities. The southern African habitats of MIS 3 offered a seasonal range of plant and animal foods that was accessible using other simpler technologies better suited to changed demographic conditions. To repeat a point made many times already, population size, density, and degree of social interaction affect rates of learning and innovation (Fig. 6.8). At the local level, the history of technology will be anything but a smooth progression. We can expect leaps, dips, or stasis depending on the shifting mix of social, demographic, and ecological factors. Taking a broad view, the aftermath of hafting is probably reflected in what appears to be a steady growth in human population after 60,000 years ago. The invention of improved means of extracting energy and nutrients from the environment led to a boost in our numbers (Shennan 2001: 14) (Fig. 6.9). There is no need to speculate about a sudden change in cognitive capacities that made us smarter or better at communicating complex ideas (e.g. Klein 2001). The foundations were already in place for an expansion of our cultural niche as a tool-dependent species. More recently, within just the past 10,000 years we have broadened that niche radically through biotechnology.

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105 104 Isotope stage ka

190

6

5 130

4 70

3 60

2 27

1 12

Fig. 6.9 An estimate of human population growth over the past 160,000 years showing fluctuations linked to interglacial and glacial stages as well as more continuous growth after 60,000 years ago (start of MIS 3). (After Shennan 2001 and Ambrose 1998.)

The invention of plant and animal domestication—a subject beyond the scope of this book—led to an increase in population size five times faster than before (Gignoux et al. 2011). We now live with its many consequences, including an utter reliance on combinatorial technologies.

7 A Revolution without Heroes This book has been about the genesis of an idea around 500,000 years ago that has helped shape the modern world. Everything we make today employs the combinatorial principle. A wooden spoon or saucer might seem like exceptions, but even these simple objects involve other tools in their making and, more likely than not, those tools are made of multiple parts that required other tools to make them in an extended chain of interdependent technologies. The combinatorial idea is simple in the abstract but complex in the reality of its application. The smartphone is the conceptual descendant of the hafted knife, adze, and stone-tipped spear. They differ in the complexity of their components and uses, but they share the essence of the combinatorial principle. They also share the cognitive, anatomical, and social foundations that coalesced in the Middle Pleistocene and which still underpin our use of the combinatorial principle. My aim from the outset was to identify the prerequisites for the invention of the combinatorial principle, and then look for its earliest application in the form of the first hafted tools. A secondary aim was to consider why this invention happened when and where it did. ‘Why’ was the most interesting question to pursue and the hardest to answer with any certainty. The ideas of complexity theorist W.B. Arthur have given the structure to much of this volume and he made an observation (2009: 125) that clarifies the challenge faced here: ‘the fact that all inventions are supported by a pyramid of causality means that an invention tends to show up when the pieces necessary for it, and the need for it, fall into place’. We can identify the necessary pieces including the biological and social foundations as well as the archaeological precursors to hafting, but how can we really ever know what particular needs—real or perceived—lay behind this invention? Those who argue that inventions can only really be

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understood in the context of cultural choices made at a particular place and time do not require ‘needs’ as part of the explanation. The answer for them is to be found within a culture or group and not in impersonal forces such as a universal drive to maximize efficiency. The distance of time and vagaries of preservation make this historical approach impossible to apply. I have opted instead for an evolutionary perspective in which those technological innovations which enhance the chances of survival of individuals and groups stand a greater chance of being transmitted across generations. There is the risk of circular reasoning here, but, as we have seen, some presumably advantageous technologies were abandoned in the past, such as the early bow and arrow in southern Africa or fish hooks and nets in Tasmania. Population size, density, and how often individuals interact clearly affect whether an innovation takes root or withers. Just because a technology is ‘better’ at solving a problem does not guarantee its success, especially if it requires unsustainable levels of expertise. The combinatorial principle has thrived because of its flexibility. It is not one tool; it is a way of thinking about technology that began with hafting and has since spread to all forms of manufacture. The inventors of hafting (and the combinatorial principle) lived directly from the land in small communities in which everyone contributed to the survival of not just their family but to the group as a whole. Hafted tools made the daily tasks of getting and preparing food more efficient, more predictable, and less risky compared with the existing traditions of hand-held tools. They opened new landscapes for colonization or simply made it easier to live in familiar surroundings. In times of rapidly changing resource availability, the combinatorial principle may have been crucial to the survival of a group by expanding its range of potential responses. The invention of hafting could have enhanced mobility or broadened the choice of available foods, as well as tipped the balance in armed conflict. These decisions were made at the group level and are invisible to us, but they left their collective signatures in the archaeological record in the form of tools made, foods eaten, and habitats settled or abandoned. There are genetic echoes, too, of patterns of movement and interaction. Direct evidence for conflict appears only late in the record, but there are more subtle and earlier signs of competition for resources between Neanderthals and immigrant moderns in western Europe. The invention of the mechanized propulsion of points, either

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as darts or arrows, improved radically the effectiveness of humans as hunters. The invention of traps increased further the resilience of communities to short-term shortages, especially given the uncertainties of big game hunting.

WHY THEN? If we accept that the invention of hafting was ultimately driven by the need to improve food security, we must ask why it happened in the Middle Pleistocene and not before. Earlier human ancestors also had to find food and water in order to survive, so what changed? The answer probably lies in the co-evolution of the brain, body, and society in response to increasingly unstable environments. The onset of the Middle Pleistocene around 900,000 years ago marks a shift to longer and harsher glacial cycles. The impact varied regionally depending on latitude, size of land mass, topography, and proximity to oceans. It varied temporally too according to the combined effects of the earth’s astronomical cycles on the amount of heat received from the sun during the seasons. After 430,000 years ago, the contrast in temperatures between glacial cold and interglacial warmth became even more extreme. The bumpy shift from one extreme to the other disrupted the distribution of habitats and the food resources on which humans depended. The spread of deserts and ice sheets blocked routes of movement between regions during glacials, and similarly the interglacial expansion of equatorial forests and rise of sea levels created different kinds of barriers. Overlying this general pattern of gradual change on the scale of thousands of years were the repeated and rapid short-term fluctuations (sub-millennial events) felt on the scale of a human generation or less. The ethnographic record of hunter-gatherers gives us a glimpse of the likely responses of Middle Pleistocene communities to this changing kaleidoscope of pressures on resources. The range of options include changes in mobility, a broadening or specialization of the diet, technological innovation, expanding support networks, and appeals to supernatural intervention. There is also the unintended option of the local extinction of communities. Natural selection in the form of variability selection favoured those groups with the behavioural and biological capacity to adapt to a broad range of

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habitats in the short and long term (Potts 2001). The expansion in human brain size seen in the Middle Pleistocene is a likely reflection of this process of selection, as is the evolution of an extended childhood with its opportunity for learning more complex ways of making things (Csibra and Gergely 2011). We can also infer that the rudiments of cooperative behaviours were in place to support the gestation, birth, and nurturing of dependent offspring. Food sharing as an organizing principle of recent hunter-gatherer societies also probably existed, as did some basic division of labour between males and females. The invention of hafting slots neatly into this biosocial mix as it would improve food security, increase adaptive fitness, and reinforce the sharing of meat as a social bonding mechanism. Brain-imaging research has also given us much clearer evidence that complex technology and language co-evolved, and with them our facility for hierarchically organized behaviours (Stout and Chaminade 2012). The concepts of the technological and social brain are really complementary visions of the intertwined behaviours that underwent natural selection during the Middle Pleistocene.

LOOKING FORWARD The hard evidence is lacking for this descriptive model of the links between climate variability, brain size, sharing, and the invention of the combinatorial principle. We are necessarily in the realm of drawing correlations between what might be circumstantial evidence. That is an inherent problem with the archaeological record, and especially when looking for the origin of a largely organic technology. The development of microwear and residue analyses has opened a window onto the time depth of hafting, but there is still much to be done to improve the reliability of these techniques. The indirect morphometric measures that distinguish hand-held spear tips from mechanically propelled points have also expanded our knowledge of the when and where of hafting as well as the invention of the first machines. Ideally, microwear and morphometric approaches should be combined where feasible to give the most reliable evidence possible for hafting and its uses. There are many assemblages of stone artefacts waiting to be studied, and I have no doubt that the archaeological evidence presented here will soon be eclipsed by older examples of

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hafting from parts of Africa, Europe, and the Near East. South Asia may enter the picture as a separate area of independent invention, but this is less likely to be the case for the rest of Asia where some of the critical precursors to hafting were absent. New finds and analyses will force us to rethink the details of the model, but I suspect the foundations will remain firm. The integrative technologies of the Acheulean (fire, bifaces, prepared cores) prefigured hafting in that they brought together the knowledge of differing materials in their making or they required a long sequence of actions to achieve a goal. In the late Acheulean, in some areas, there is also a focus on producing straight, sharp, and portable cutting edges in the form of prepared flakes and blades. This experimentation with more standardized edges may be an example of ‘structural deepening’ in Arthur’s (2009: 135) sense of trying to solve a long-standing problem by doing more of the same in applying more variants of existing technologies. Perhaps the large cutting tools and small flake tools of the Acheulean had reached the limit of their capacities to meet the needs of communities living in more variable and unpredictable habitats. The invention of hafting allowed for greater flexibility in tool design based on the combinatorial principle. Hafted knives and scrapers may have usurped some of the uses of hand-axes/cleavers and flake tools, but stone spear points were something altogether new. Some functions of the heavy-duty handaxe and cleaver may have been replaced by the hafted adze as a multipurpose cutting and chopping tool. I suspect too that some cleavers and hand-axes were hafted, but this assumption remains to be tested experimentally and microscopically. The search for a single centre of origin of the combinatorial principle is a quest built on sand. As well as the issue of preservation and the reliability of indirect markers of hafting, there is an enormous problem with the lack of dated sites from large regions of Africa and Asia. Until these gaps are filled the jigsaw is missing too many pieces to make a coherent picture. What evidence we do have places hafting early as 500,000 years ago in southern Africa, and after 280,000 years ago in east Africa, southwest Asia, and in Europe. The geographical balance in dates will change as we look more closely for traces of hafting in the various late Acheulean traditions of tool-making. From these foundations hafting was probably invented independently in two or more places in response to similar needs and roughly at the same time. We can speculate about the impact of climate change and which marine isotope

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stage might have been the driver of invention, but that kind of speculation has to be grounded in the specifics of time and place. We will need to know what resources were available, how they fluctuated seasonally and over the longer term, how tools were made and used, and what was the approximate population size, density, and distribution. We will need this information for the period preceding the purported time of invention and afterwards as a test of the predicted benefits of the new technology. There are few places where this kind of detail is available now, and it will take much effort and grant funding to gradually fill in the pieces of the puzzle. The first step on this long road is to recognize that the combinatorial principle was not just one among many inventions in human history. It transformed not just how humans extracted energy from the environment, but how we organized our social lives. We are now more dependent on this revolutionary idea than at any time in our past. Very few of us live in a world where we have the craft knowledge and resources needed to make all we use. Instead, we rely on the highly specialized expertise of others to feed us, to keep us healthy, entertained, and connected to vast networks of shared information that are the new platforms of innovation. The next time you use a knife with a handle, spare a thought for those unknown inventors of hafting who unwittingly changed how we interact with the world and each other.

APPENDICES

Appendix 1: A Brief Guide to the Structures and Networks of the Brain The starting point is the neuron, which is active in transmitting information in the brain and through the central nervous system, and is recognizable as the grey matter seen in the dissected brain. For fans of Agatha Christie, neurons are the ‘little grey cells’ on which detective Hercule Poirot so relies to solve the most puzzling of cases. Poirot is correct—to a degree—neurons are essential components in the higher cognitive functions of planning and reasoning. But there is more to the structure of the brain than neurons, and they are not even the most numerous of cells in the brain. That statistic belongs to glial cells, which outnumber neurons by a factor of ten (Williams and Herrup 2001). Glia form a protective cover (a sheath of myelin made of cholesterol) that speeds the transmission of electrical pulses through the neuron and provides the essential connective tissues of the brain. They are identifiable on dissection as the brain’s white matter (living brain tissue is pink, not grey or white; those colours come from the application of formalin as a fixative in preparation for dissection [Hendelman 2006: 3]). There are an estimated 100 billion neurons in the average adult brain, and we are born with a surplus to our immediate childhood needs (Williams and Herrup 2001). That surplus declines as we settle into daily routines, but a sustained change to our habits can result in the formation of new connections to other neurons. Imaging studies have shown that learning a new task, such as juggling, expands neural networks in a matter of weeks (Draganski et al. 2004). Intensive training can generate structural changes in the density of neuron clusters as well, and expand connecting pathways. Musicians, mathematicians, and London taxi drivers each have their own expanded neural structures stimulated by the demands of their particular professions (Maguire et al. 2000; Aydin et al. 2007; Draganski and May 2008). It seems the brain has an unexpected degree of adaptability in its ability to change in response to new stimuli; even an old dog can learn new tricks. In this context, the invention of hafting technology presumably generated new neural connections among its users and the potential for innovations based on the combinatorial principle. Neurons receive information from other neurons by chemical messengers (neurotransmitters) that cross the short gaps (synapses) separating specialized receptors on the extremities of each neuron (dendrites).

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Neurotransmitters activate an electrical firing pattern in the neuron that pulses from the body of the cell along a connective fibre (axon), given greater conductivity by its fatty myelin sheath, to terminals on the axon where neurotransmitters are released. This electro-chemical process links the typical neuron to hundreds, if not thousands, of other neurons (Shipp 2007). Our diet is an important source of neurotransmitters, with some foods being notable sources of particular molecules (e.g. potassium) essential for proper functioning of the brain, and insufficient supplies can affect how our ability to think, feel, and remember. Functionally specific clusters of neurons (nuclei) are found throughout the brain, from its surface down to its base. Some nuclei are specialized receivers and relayers of sensory information from the eyes, ears, nose, mouth, and body. Most nuclei form parts of larger networks that integrate these inputs to generate either automatic or deliberate thoughtful responses to physical, social, and emotional stimuli. Starting from the base of the brain and moving upwards, neuclei are organized into functional systems that have long been described as forming a sequence of increasing complexity from the lower to higher cognitive functions. The lower functions of the brain stem are more ‘primitive’ in that they support basic life-sustaining functions such as regulating heartbeat, respiration, and maintaining consciousness. The higher cognitive functions give us greater behavioural flexibility in responding to novel challenges, and include our ability to plan far ahead into the future, make complex tools, use language, and to behave in socially appropriate ways. The simplified organizational sequence of a lower to higher brain reflects the long evolution of the mammalian brain with primates, and especially humans, evolving proportionally larger areas engaged in abstract thought compared with other mammals (Neill 2007). All vertebrates have these functional systems, including a forebrain that links and reacts to incoming sensory and motor information. In humans, the forebrain has expanded greatly as part of the two cerebral hemispheres that effectively envelope almost all other brain structures. An expanded frontal cortex enables us to generate complex internal or mental models of how to behave in the physical and social worlds we inhabit, and those models include the making and using of tools (Frey 2008). The neurons of the cerebral hemispheres occur at the surface, or cerebral cortex. This surface is also known as the neocortex or ‘new’ in reference to its relatively recent evolutionary expansion. In mammals, the neocortex forms a thin coating only 2–3 mm thick and composed of up to six layers of neurons. In humans the number of layers varies depending on the area of the brain, but on average there are seven layers (Joseph 2000). The cortical layers receive and transmit information from other cortical areas and from sub-cortical areas (Neill 2007). That interconnectivity enables rapid processing of multiple sensory

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and motor inputs from the body, and underpins our higher-order thought processes. Our neocortex is deeply folded into ridges and furrows, more so than in any other primate (Shipp 2007). The folding results in an expanded surface area of the brain which allows for a greater volume of neurons, connective tissues, and blood vessels to be squeezed into the limited space of the skull (Bruner 2004). More grey and white matter means more processing capacity, including more functionally specialized areas, and ultimately greater intelligence (Sherwood et al. 2008). The modern human neocortex holds approximately 150 specialized areas (fields), and increasing the number of fields is another means of increasing cognitive capacity over evolutionary time (Neill 2007).

From the Bottom up Returning to the base of the brain, the cerebellum or little brain is the first structure of particular relevance to mapping the neuroanatomy of hafting (see Fig. 2.1b). The cerebellum has two hemispheres that resemble a matched pair of large walnuts or very small cauliflowers—choose your preferred food analogy. It is situated behind the brain stem where it receives movementrelated information from the body and relays it to the cerebral cortex. Its two cerebellar hemispheres are formed of heavily ridged cortex, and as a little brain it has its own structural and evolutionary sequence of lower (older) to more complex (newer) functions. Together, they help coordinate bodily movements involved in posture, locomotion, and use of our limbs, including the comparison of intended with actual movements (Lewis 2006). The latter plays a role in developing skilled tool use and responding to immediate challenges to expectations (Leiner et al. 1993). Imaging research, however, has revealed a potentially more significant role for the cerebellum. It is involved in forming and then storing internal models about how new tools work (Imamizu et al. 2003). Each new tool with the associated learned skills is stored as a separate model in the cortex of the cerebellum (neocerebellum), the equivalent of the higher function areas of the neocortex. If this is indeed the case, and so far very few individuals have been studied, then the cerebellum will have been integral in not just the invention of hafting, but also linked intimately to the gradual expansion of the range of tools made over time. We might expect a commensurate growth in the neocerebellum as part of a feedback loop linking combinatorial evolution with the evolution of the brain. The cerebellum may also be involved, in connection with the neocortex, in the formation of mental models not just about the working of physical objects but also the representation of objects using symbols, including gestures and words (Imamizu et al. 2003; Barton 2012). Carving or painting symbols of group membership onto the handle of a knife might be just the sort of combination of abstract meaning with a physical object enabled by the interconnectivity of the cerebellum with the higher functions of the brain.

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The flow of information to and from the cerebellum to the cerebral hemispheres passes first through an intermediate relay centre, the thalamus. The thalamus is situated above the cerebellum and lies between the brain stem and the cerebral hemispheres. It distributes movement-related inputs to specialized motor areas of the neocortex, but also coordinates the distribution of sensory inputs (sight, sound, touch, and taste, but not hearing) to the neocortex. Above and to either side of the thalamus lies a cluster of greymatter bodies involved in the transmission of motor input to and from the cerebral cortex. The basal ganglia (less commonly known as the basal nuclei) receive input from specialized motor areas and from multipurpose networks in the neocortex known as association areas. The latter integrate and process inputs from a variety of sources and generate the complex behaviours of the higher cognitive functions (Pandya and Seltzer 1982). Before moving to the anatomical structures of the neocortex, it is worth recalling the role of glial cells in the structure of the brain. They form the complex networks of connective tissues that not only comprise the bulk of the cerebral hemispheres, but which form the vital pathways (or tracts) for the transmission of information. That transmission takes place within and across the hemispheres, to and from the brain stem, cerebellum, thalamus, and the basal ganglia, and from the brain to the body via the spinal cord. A relatively new imaging technique, diffusion tensor imaging (DTI), reveals these tracts of white matter and how they connect the many areas of the brain (e.g. Ramayya et al. 2010). The neural topography of the cerebral cortex has its own terminology (see Hendelman 2006 for details). The surface folds of the cortex form recognizable patterns that are found in all humans and so provide standard landmarks for locating specific areas and the components of neural networks. Raised folds, or gyri (singular gyrus), are separated by furrows, or sulci (singular sulcus), along which arteries and veins move blood to and from the brain. A single deep fissure separates the cerebral hemispheres into two halves that remain joined by a thick tract of white matter (corpus callasum) (see Fig. 2.1b). Two other shallower fissures provide landmarks for dividing the cortex into four lobes. The central fissure separates the frontal lobe from the parietal, and the parieto-occipital fissure distinguishes the parietal from the occipital lobe. A third fissure, the lateral (or Sylvian fissure), forms another landmark for locating areas of the temporal lobe involved with language, hearing, taste, as well as planning tool use (see Fig. 2.1a). Since the early twentieth century and long before the development of brain-imaging techniques, neurologists had devised a system for identifying the location of areas of neurons that shared structural properties. Under the microscope, stained cross sections of the cortex revealed patterns in the layer-like arrangement of neurons that became the basis for grouping them into clusters or areas (Brodmann 1909 [2006]). Brodmann’s system of

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numbered areas was applied across species, including humans and monkeys, but although the same Brodmann number does not necessarily mean the equivalent functional area between species, the system provides a standard anatomical reference map. The numbering has been revised and elaborated subsequently, and physiological and imaging methods have demonstrated some consistent correspondences between numbered Brodmann areas (BA) and functionally specialized areas of the brain (Johnson 2007) (see Fig 2.1a). These correspondences will be noted where they are relevant to our neural map of hafting and language. The central fissure, on both hemispheres, provides the landmark for locating specialized areas involved in coordinating the sense of touch and the voluntary control of muscles. These sit like two headbands to the back and front of the central fissure. Behind the central fissure, in the parietal lobe, the fold known as the postcentral gyrus (BA 3, 1, and 2—this convention of numbering was established by Brodmann, with area 3 above the others) receives sensory information through the thalamus from the fingers, lips, skin, limbs, and joints (see Fig. 2.1a). The thumb has more neuronal connections here than any other part of the body, which reflects its key role in forming basic grips in concert with the fingers, especially in skilled precision work, such as holding a pen or paintbrush. The central importance of the postcentral gyrus in receiving input from the body and senses is recognized by its label as the primary somatosensory cortex (Hendelman 2006). The region specialized for executing the control of muscles, or primary motor cortex, lies to the front of the central fissure, on the precentral gyrus (BA 4). Each of the other senses (vision, hearing, and taste) has its own dedicated primary cortex that receives input via the thalamus. The basal ganglia and cerebellum send information via a part of the thalamus to the primary motor cortex and the premotor cortex (BA 6, which also includes the supplementary motor area) where planning of movement takes place, including those based on memory and involving use of both hands (Nachev et al. 2008). To the front of the premotor cortex lies the prefrontal association complex (BA 46) which contributes to planning, but also formulating abstractions such as models of cause and effect needed for making hafted tools (Wolpert 2003). This complex is actively engaged in selecting what are considered to be appropriate voluntary movements in terms of conscious mental models with their self-generated rules based on experience (Lewis 2006). As an aside, sensory and motor input from the right side of the body is controlled by the related cortex on the left hemisphere, and vice versa. We who are left-handed are literally in our right minds, well, at least when it comes to the basic senses and control of movement. The left-hemisphere control of right-handedness is a potential marker for the evolution of the organizational structure of the human mind, including the left-hemisphere dominance of language (Steele and Uomini 2009).

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The association areas involved in language may be largely left-hemisphere based, but other higher cognitive functions are distributed in both hemispheres. As a reminder, association areas integrate sensory and motor areas with memory systems to enable coordinated, considered responses to the physical and social world (Pandya and Seltzer 1982). Decision-making also involves the integration of our mental (psychological) and physiological reactions to emotion through connections of the neocortex with the midbrain association area of the limbic system. Association areas involved in processing visual, spatial, and motor inputs all interact in the formation of a model of our body as it moves and acts in the physical world. This model or body schema is continually updated to coordinate movements of the limbs, and adjust posture in response to actions (Maravita and Iriki 2004). Simple tools, such as a stick, are easily integrated into the body schema (Bonifazi et al. 2007). More complex tools, ones that transform the movement of the hands into a qualitatively different action, such as cutting with a hafted knife, demand additional access to information stored as memory about the object’s structure, function, and methods of use (Frey 2007: 368). Two other left-hemisphere association areas deserve our attention given their general importance in our functioning as humans. These are the wellknown Broca’s language and speech-production area of the prefrontal cortex (BA 44, 45) and Wernike’s language comprehension area on the temporal lobe (BA 22) (see Fig. 2.1a). As Figure 2.2 shows, there is an economy of connections in their locations. The area associated with the transformation of sounds into thoughts (Broca’s) is also engaged in the construction of abstract thought and production of voluntary movements. Similarly, the comprehension of speech (Wernike’s area) is adjacent to the primary auditory cortex located along the lateral fissure (BA 41, 42). These locations make functional sense in terms of minimizing the length of connections between neurons that perform similar roles (Shipp 2007). Proximity speeds processing time as well as saving space. Processing efficiency is also enhanced by the involvement of association areas in more than one task, an observation supported by imaging research. Broca’s area, for example, plays a supporting role in the understanding of tool function and planning of tool use (Lewis 2006). In the developing child, by the age of three, the upper part of Broca’s area becomes specialized for coordinating muscle movement involved in using tools—in particular the hands—and the lower part has a separate role coordinating the muscles involved in producing speech (Greenfield 1991; Green et al. 2002). It is not surprising that this multifunctional area of the brain is also thought to play a prominent role in the human version of the mirror neuron system (Rizzolatti and Craighero 2004; Spunt et al. 2010).

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Networks for Planning and Using Tools Following the general discussion in the main text on the location of areas of the brain involved in planning tool use, we can look in more detail at particular areas and their connections. Planning tool use activates four regions of the left hemisphere (Johnson 2007: 371). They include areas of the inferior parietal lobe (IPL) (BA 39 and 40) involved respectively in naming or classifying tools and in preparing and enacting tool use (Frey 2007: 371–2); areas of the frontal lobe (middle frontal gyrus, BA 46, and premotor cortex, BA 6 (dorsal, PMd, and ventral, PMv), both involved in planning and preparing movements in response to abstract models of tool use (Johnson-Frey et al. 2005; Goldenberg and Spatt 2009). A fourth area, in the prefrontal cortex (BA 9, dorsolateral prefrontal cortex, DLPFC) (see Fig. 2.1a), is engaged in planning and preparing hand movements and accessing working memory (Frey 2007: 372). Planning, unlike active tool use, also activates areas of the left prefrontal cortex (BA 46) and temporal sulcus (BA 21) thought to be involved in accessing working memory related to motion (Johnson-Frey et al. 2005; Ulma-Runge et al. 2011). It is here that constructive memory might also be found. Data derived from lesion studies and functional neuroimaging point to a strong left-hemisphere bias in the perception and planning of tool use, and involvement of both hemispheres in the active use of tools (Lewis 2006). In the left hemisphere, the parietal and prefrontal cortices work together in selecting appropriate movements in response to the perceived demands of a task. The parietal cortex integrates information about the identity of the tool (ventral stream data) and its spatial location (dorsal stream) with sensory input on the status of the hands and limbs in preparation for action. The prefrontal cortex assesses the physical demands of the task at hand and this information is used by the parietal cortex to select the appropriate grasp (Frey 2008). The selection is activated by the premotor cortex (BA 6) and executed by the primary motor cortex (BA 4). The dynamic interaction between these and other areas of the left hemisphere will vary depending on the task and how it is presented. A visual cue will activate different pathways to a spoken cue. The superior parietal lobule (SPL) (BA 5 and 7) is engaged when viewing a tool (Buccino et al. 2001); the inferior parietal lobule (IPL) (BA 39 and 40) comes into play when planning how to manipulate an object when viewed or heard (Lewis 2006: 223). The premotor cortex (BA 6), and in particular the left-hemisphere dorsolateral premotor cortex (DLPMC) (BA 6 and 8), is more active than its right-hemisphere counterpart when imagining grasping a tool, and has a role in accessing working memory (Lewis 2006: 225). In a rare functional imaging investigation (using PET) of naturalistic tool-making involving the knapping of stone flakes from a core, it was found that as the demands on spatial coordination increased with the complexity of the tool

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design (from simple flake removal to making a three-dimensional symmetrical hand-axe), there was increased activation of the same areas of the premotor cortex and inferior parietal lobe (BA 39 and 40) areas in both hemispheres (Stout and Chaminade 2007). In fact, the right-hemisphere homologue for Broca’s language-production area was also activated reflecting the increasing need for sequential and hierarchical action involved in making a hand-axe (Stout et al. 2008).

Appendix 2: Climate Cycles in More Detail The tilt of the earth’s axis as it orbits the sun gives us our changing seasons. On a much longer timescale, the amount of sunlight received by the earth (insolation) at any particular season and latitude varies according to the interaction of three astronomical cycles, each of which changes rhythmically and at a different time scale (see Fig. 4.3). Today, the axis of the earth’s rotation is tilted 23.5º from the vertical and this tilt is fixed as the earth orbits the sun. The poles take their turn in pointing either towards or away from the sun and so the seasons progress in opposite directions between the northern and southern hemispheres. We are familiar with the extremes of daylight at each solstice (21 June, 21 December), with the longest day on the summer solstice and the shortest day at the winter solstice. The intervening equinoxes, when the length of the day and the night are equal (20 March, 22 September), mark the start of spring and autumn depending on the hemisphere in which you live. The tilt of the axis (or obliquity) varies by about 1.5º either side of the 23.5º average and shifts over a 41,000-year cycle from one extreme of tilt to another (21.8º–24.4º) (Maslin and Christensen 2007). The importance of this cycle lies in its impact on the amount of sunlight received at the poles. A more vertical angle reduces the amount of summer sunlight received, and the greater the tilt the greater too is the difference in temperatures between the seasons. The earth’s orbit around the sun varies in its shape from elliptical to more circular, which affects the amount of sunlight received on earth in each season (Fig. A2.1). A circular orbit would even out the seasonal variation in solar radiation received. The orbit is currently in an elliptical phase of a long cycle of ‘eccentricity’ that lasts on average about 100,000 years. The ellipse means that every year on 3 January the earth is at its nearest point to the sun, a distance of 146 million kilometres and known as perihelion. Perihelion today brings the earth about 10 million kilometres closer to the sun than at its point of maximum distance (156 million kilometres), or aphelion, that occurs on 4 July every year (Imbrie and Imbrie 1979; Maslin

Fig. A2.1 The orbital drivers of glacial-interglacial periodicity are shown along with their periodicities: eccentricity (100,000 years), obliquity (41,000 years), and precession (22,000 years. (Reproduced from Grove 2012 with the permission of Elsevier Ltd and with permission of M. Grove.)

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and Christensen 2007). The elliptical orbit results in the northern hemisphere having a spring and summer that is longer by a week than autumn and winter combined. The situation is reversed in the southern hemisphere, making autumn and winter longer with less sunlight received overall. A more circular orbit would reduce the contrast in sunlight and warmth between the hemispheres. Two other variables add interest to this geography lesson and give it particular relevance to our story. First, the earth’s rotation around its tilted axis is not smooth: it wobbles because of the gravitational pull of the moon and the sun. The wobble is imperceptible as it completes one transition every 27,000 years. This gyration affects the distance between the earth and sun at any particular season (Maslin and Christensen 2007: 450). To this cycle we add the longer-term variations in the shape (eccentricity) of the earth’s orbit and the result is a rhythmic change of the position of the solstices and equinoxes every 21,700 years. This ‘precession of the equinoxes’ has its greatest effect on the amount of sunlight received in the tropics. Today, for those of us in the northern hemisphere the winter solstice happens when the earth it at its nearest point to the sun. That arrangement also existed around 22,000 years ago, but 11,000 years ago the earth was 10 million kilometres (3 million miles) further from the sun at the time of the northern winter solstice (see Fig. 4.3). As a result, the northern hemisphere autumn and winter would have been longer, colder, and darker than in the southern hemisphere, but the summer would have been warmer and so contributing to a decrease in the polar ice volume. It is no coincidence that global deglaciation was underway 11,000 years ago. At 65ºN the effect of reduced solar input in the summer months is generally thought to trigger the build-up of ice in the northern hemisphere. That process is amplified by an increased reflection of sunlight off the ice and back into space (increased albedo), which in turn leads to further cooling and ice build-up. Also amplifying the process is a reduction in greenhouse gases that trap reflected light (heat), such as carbon dioxide, methane, and water vapour. The polar-ice cores show a close correlation between low levels of these gases (found in air bubbles in the ice) and the expansion of ice sheets (Ruddiman and Raymo 2003). As the ice sheets expand they also cool the northern seas and shut down the oceanic currents that today bring warm equatorial waters northwards, such as the Gulf Stream, which give northwestern Europe its relatively mild winters. There are other feedback mechanisms in operation that amplify the rapid end of glacial cycles, but what is clear from the above is the complex interaction of orbital and local variables that together drive the duration and severity of glacial-interglacial cycles.

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The Middle Pleistocene Record The global evidence for the Middle Pleistocene Transition comes from three primary sources: deep-sea sediments, the polar ice sheets, and thick terrestrial dust deposits. The marine record takes primacy both historically and due to the variety of information preserved. Systematic coring of deep-sea sediments since the 1950s has provided remarkably detailed records of shifting patterns of climate change for both hemispheres. The sediments preserve indicators of changing temperatures, ice volumes, wind speeds, and patterns of ocean circulation. Changes in global ice volume reflect changes in temperature and the key evidence comes from associated changes in the geochemistry of ocean waters as ice sheets wax and wane. Oxygen in seawater has a heavy isotope (18O) and a light isotope (16O), and as polar ice sheets grow they incorporate more of the lighter isotope and leave behind seawater enriched in the heavier oxygen. During warm stages, such as our current interglacial, seawater has a more balanced mix of isotopes. This elegant proxy of warm and cold stages is incorporated into the carbonate skeletons of microscopic sea animals (foraminifera) that on death accumulate as fossils in marine sediments. The combined result of several key deepsea cores is the Marine Isotope Stage (MIS) record of the 103 stages of the Pleistocene. Following convention, the cold stages are even numbered and warm stages are odd numbered. Our interglacial stage is MIS 1, and the obvious starting point for the sequence. The duration of each stage is estimated with some precision using key markers of periodic shifts in the earth’s magnetic polarity recorded in the sediments that provide an independent framework for calculating rates of deposition. These are then ‘tuned’ to mathematical models of the duration of climate cycles based on well-known parameters of the earth’s orbit. There are two other long and independent records of climate. The polar ice sheets (on Greenland and the Antarctic) also record fluctuations in oxygen isotope ratios, but as air trapped in the snowflakes that make up the ice. The ice-core records do not stretch as far back in time as the marine records—about 1 million years—but fortunately they span the Middle Pleistocene and provide supporting evidence of changes in temperature, rainfall, and other atmospheric gases associated with the transitions between stages. On terra firma, the nearest parallel to the deep-sea records is found in thick deposits of glacially derived dust (loess) blown long distances, that is, interspersed with evidence of soils formed under warmer conditions (paleosols). These loess sequences extend across northern Eurasia from China to Europe. Those from north China and central Asia are the thickest and provide highresolution climate data that span the full Pleistocene (see Dennell 2009). Much like the deep-sea record, the loess glacial and interglacial stages are dated by palaeomagnetism, estimated sedimentation rates, and orbital

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tuning. When compared, the marine and loess records correlate closely especially after 900,000 years ago (Liu et al. 1999; Head and Gibbard 2005: see Fig. 1). The impact of the uplift of the Tibetan plateau on the region’s climate also leaves its signature in the dust profiles (Sun and Liu 2000). As well as providing long terrestrial records of climate stages, loess deposits preserve evidence for changes in temperature, rainfall, and vegetation that are of vital importance to reconstructing shifting selection pressures.

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Index Acheulean, the 146, 152, 153–4, 156, 158, 159, 231, 281 blades in 161, 163, 164 large cutting tools of 141–4 tradition 141–2, 144–5 see also Bouheben; hand-axes Acheulo-Yabrudian Complex 161, 164, 229 adhesives 186, 190, 192, 200, 201–2, 206 chemistry of 187–9 see also tar Aduma (Ethiopia) 261 adzes/adzing 180, 182, 199, 200, 204, 223 Agta, the (Philippines) 92–3, 146, 255–6, 273 Aka, the (Congo basin) 89–90, 104, 127 alloparenting/alloparents 91, 101, 105 Ambrose, Stanley 49 anatomically modern humans (AMH) 116, 121, 122 Anthropocene, the 137 n. anthropology 17 aphelion 290 applied hafts 184, 192–3, 199, 200 apprenticeships 80 apraxia 44 arrows 190, 192, 199, 200 see also bows and arrows Arthur, W. B. 3, 15, 20, 30, 36 n. 3, 246, 277, 281 on invention/technology 25–6, 29, 31 ash 167 n. Asia 268–9 hafting in 231–4, 281 see also China; India; Indonesia; Middle Pleistocene Transition Atapuerca see Gran Dolina; Sima del Elefante; Sima de los Huesos atlatls see spear-throwers Australopithecus afarensis 55, 102, 104

Australopithecus sediba 55 axons 284 backing see blunting/backing Bandura, Albert 77 basal ganglia 43, 48, 286, 287 Biache St Vaast (France) 224–6 bifaces 152, 158 n., 164, 231, 238–9, 251, 252 see also bout coupe; cleavers; hand-axes binders/bindings 185–6, 189–90, 191, 192, 200 bipedalism 55 Blackwood, Beatrice 17–18, 61 blades 160, 164–5 evidence of use 161–3 Blombos Cave (South Africa) 263 blowguns 255 blunting/backing 215–16, 229–30 see also knives body schema 34, 47, 54, 57, 62, 288 Bogin, Barry 98, 99 Bolomor Cave (Spain) 273 Bordes, Francois 225 Botswana 81 Bouheben (France) 227 bout coupé 153 n., 231 n. bows and arrows 12, 212, 221, 243, 253, 273 in archaeological record 259–65 nature/workings of 253–6 Boxgrove (England) 70, 71, 146, 147 brain in infants/children 86–7 shape 67–8 size and adaptability 65–7 size and child dependency 99–100 structures/functions/networks 36–7, 42–6, 283–90 see also complex tools; creative engineering; handedness; memory; Neanderthals; neuroimaging techniques; power grip; precision grips

352

Index

breastfeeding 87 Broca’s area 45, 46, 47, 67, 72, 288, 290 Brodmann, K. 286–7 Brodmann areas (BA) 43, 44, 49, 286–7 California (‘Little Ice Age’) 124 Campitello Quarry (Italy) 217–18, 244 Caspari, Rachel 103 Cave of Hearths (South Africa) 229 cerebellum 43, 48, 72, 285–6, 287 cerebral cortex 36 n. 2, 43, 44, 63, 284, 286 see also neocortex Chikri (India) 158, 231 children four stage development pattern of 87–8 learning and 77, 78, 79–80, 81–2, 83, 85–6, 88–9 see also brain; extended childhood; mother-child relationship; teeth chimpanzees 35, 40, 49, 57, 60–1, 65, 98, 99 learning in 78–9, 80 China 119, 122, 131, 134, 144, 145, 159, 232, 293 chopping/dicing 180 Clacton-on-Sea (England) 234 n. clamp hafts 184, 193, 199, 200, 222 Clark, William 28 cleavers 143, 144, 146, 149–50, 153, 163–5, 238 prepared cores and 154–5, 157, 158, 159 cleft hafts 184, 189, 190, 192, 199, 202, 207, 213, 222 nature of 185 use of 200, 209–10, 214, 225, 236–7 climate change 11, 31–2, 241, 263 see also glacials/interglacials; Little Ice Age; Middle Pleistocene; Middle Pleistocene Transition climate cycles 290–4 combinatorial evolution 3–4, 15, 285 process 30–1 technological change and 25–7 combinatorial principle 50, 85, 174, 194, 195, 243, 252, 254, 274, 283 invention of 113, 153, 277–8, 280, 281–2

complex tools 34–5 brain evolution and 62–5 language and use of 41, 45, 46–7 composite hafts 184, 190, 192, 199, 200 composite technology 3, 5–6, 8 computerized axial tomography (CAT/CT) 36–7 cooperative behaviour 92–3, 105 cooperative breeding 90–2, 99, 100 copying error 127 core-axes 221–3 core preparation 154–5 origin/history of 156–60 see also prepared-core technology craft knowledge 29, 51, 141, 142, 146, 152, 164–5, 247 creative engineering 51–4 creativity 50–1, 52, 53 Csibra, Gergely 82 cutting 180, 181–2 Dansgaard-Oeschger interstadials 131 Darwin, Charles 11, 15, 25, 55, 165, 246 Darwin, Erasmus 22 de-hafting 197, 205 dendrites 283 Denisova Cave (Russia) 121 Denisovans 115, 116, 119, 121–2, 134 Dennell, Robin 145 diffusion 248, 251–2, 269 cultural/demic 250 diffusion tensor imaging (DTI) 37, 286 Dikika (Ethiopia) 104–5 dimorphism 108 Dolni Věstonice (Czech Republic) 273 dry distillation 187–8, 220 eccentricity 291, 292 electroencephalography (EEG) 36, 41 emulation 78–9 encephalization quotient (EQ) 65 endocasts 63, 64, 65, 67 experimental archaeology 19 extended childhood 98–9, 100, 101, 104, 105 extended mind concept 50 Fauresmith industry 164–5, 226 female hafts 186 n. feminization of human society 106–7, 108 fillers 189

Index fingers 106–7, 108–9 see also opposable thumb fire 120, 165, 241 in Middle Pleistocene 166–8 making 169–73, 258 thinking about 173–4 fissures (brain) 43, 55, 63, 286, 287 flakes 60, 61, 232, 233–4, 252 as points 213–14, 262 Levallois 156, 160, 213, 228, 231, 234, 238 see also tools Flores (Indonesia) 120, 134, 144, 173, 233 Foley, Rob 105 food 132 shortages 123–5 food sharing 93–4, 95 big-game hunting and 104–6 founder effect 251, 269 Frey, Scott 34 frontal lobe 67, 286, 289 functional magnetic resonance imaging (fMRI) 36 n. 2, 36 n. 3, 37, 38, 39, 41 functional transcranial Doppler ultrasound (fTCD) 42 Gademotta (Ethiopia) 240 Gamble, Clive 105 Gamo, the (Ethiopia) 209–10 gathering 92, 93–4, 95 geographical barriers 137 Gergely, György 82 Gesher Benot Ya’aqov (Israel) 157, 166–8 6¼Gi (Botswana) 261 Gibson Desert 172 glacials/interglacials 129–31, 132–6, 137, 168, 240–1, 279, 292–3 glial cells 283, 286 Goren-Inbar, Prof. Naama 150 n. Gorski, Dr Ariel 150 n. Gran Dolina (Spain) 98, 116, 118 grandparents 101, 103 Gravettian industry 265 n. Greenland 126 gyri 286, 287 see also inferior frontal gyrus Hadza, the (Tanzania) 270 haft 1

353

design 179–81 types 183, 184–5 see also individual entries hafting 7–8, 34 archaeological evidence for 201–2, 217–34 detecting/inferences for 202, 204–17 neural and cognitive implications of 194–5 origin of 237–40 revolution 1–3 social foundations of 109–11 see also individual entries hammers 146 hand, the 54–5 evolution of 55–6 evolves with technology 61–2 see also fingers; handedness; power grip; precision grips; precision toolmaking hand-axes 8–9, 60, 153–6, 157, 159, 163–4, 238, 251–2 Acheulean 141–2, 147, 149 n. and the mind 150–2 making/distribution of 143, 144–7, 151–2 uses of 147–50 handedness archaeological evidence of 70–2 language, genes and 68–9 harpoons 190, 192, 199, 200 Hayonim Cave (Israel) 226, 229, 240, 244 hearth boards 169–70, 171–2, 173 hearths 166–7, 168, 235 Heinrich stadials 131 Hepworth, Barbara 54 hippocampus 48 Holloway, Ralph 67 Holocene, the 137 n. Homo antecessor 102, 115 see also Homo erectus Homo cepranensis 118 Homo erectus 102, 115, 120, 121, 122, 138, 143, 212 Homo antecessor and 100–1, 118 Homo sapiens and 119 movement of 134, 137 tools and 144 Homo floresiensis 115, 120, 121, 122, 233 Homo habilis 120

354

Index

Homo heidelbergensis 9, 65, 138, 156, 168, 241 as Neanderthals/Homo sapiens ancestor 63, 68, 115, 116, 118 blades and 160, 161 Denisovans and 119, 121–2, 134 language and 72–3 right-handedness of 70–1 Homo helmei 160, 241 Homo neanderthalensis 115, 118 Homo rhodesiensis 119, 138, 161 Homo sapiens 65, 100, 102, 160, 241 -Neanderthals interbreeding 115, 121 spread of 115, 120, 232–3, 243, 266–8 see also Homo erectus; Homo heidelbergensis Homo sapiens neandertalensis 115 hormones 106–7 Howiesons Poort industry 262–5, 273–4, 275 hunting 92–4, 138–9, 168, 211–12, 214, 224, 227, 239 see also bows and arrows; food sharing; traps Ille Cave (Philippines) 233–4, 238 imitation 69 learning and 77, 78–9 over- 79–80 inclusion hafts 190, 192, 196, 199, 202, 221, 222 nature of 184–5, 207 use of 200, 210 Inden-Altdorf (Germany) 218–19, 220, 223 India 119, 145, 158, 164, 231–2, 268 Indonesia 18, 120, 134 see also Flores industrial revolutions 8, 9 inferior frontal gyrus (IFG) 45, 46–7, 63, 67, 151, 194 inferior parietal lobe (IPL) 289–90 innovation 8, 21, 22, 25, 27–9, 78, 141 /learning and group size 95–7 see also diffusion integrative technologies 8–9, 113, 120, 141, 247 see also core preparation; fire; hand-axes Inuit, the 93 Polar 126, 274

invention 15, 25, 26, 29–30, 51, 141 parallel 246–8 sociology of 20–2, 246 see also Arthur, W. B.; social constructionists invention of hafting 15, 16, 30, 31, 35, 73, 128, 141, 175, 177, 240–2, 277–8 centres of 244, 246–52, 281 in Middle Pleistocene 279–80 practical motivations for 223–6 juxtaposed hafts 184, 192, 199, 213, 223 nature of 189–90, 208 use of 191, 200, 202 Kalahari, the 17, 79, 94, 95, 107, 137 northern 81–2, 256 Kalambo Falls (Zambia) 150, 223, 230 Kapthurin Formation (Kenya) 158, 161, 164–5, 229, 240 Kathu Pan (South Africa) 142, 240, 244, 248 Kathu Pan 1 (South Africa) 164, 226 Kilombe (Kenya) 145 knives 157, 180, 199, 200 Australian Aboriginal 192–3 naturally backed 162–3, 215 knowledge 125–6 knowledge transmission horizontal/oblique 88–90, 95 vertical 85–6, 89, 170 Kombewa technique 158 n. Köningsaue (Germany) 219 Koobi Fora (Kenya) 168 La Cotte de Saint-Brelade (Channel Islands) 227, 228 Lake Ziway (Ethiopia) 224 language 49, 287–8 ‘gene’ 72–3 see also complex tools; handedness ‘Later Stone Age’ 262, 265 learning 75–6, 85, 109–11 human 78, 82, 83 hunter-gatherer 80–2, 89 strategies and environmental change 126–7 see also children; imitation; innovation; knowledge; knowledge transmission; natural pedagogy; social learning; theory of mind Lee, Sang-Hee 103

Index Levallois method/technology 156–7, 158, 159–60, 161, 164–5, 228, 232, 240, 252 see also flakes; points Levantine corridor 137, 142, 157, 158 n., 266 Lewis, James 38 Lewis, Meriwether 28 Little Ice Age 124, 137 n. loess 293–4 Lupemban industry 230 Lycett, S. J. 252 macaques 40 machines 243, 252–3 competitive advantage of 266–9 impact of 274–6 see also bows and arrows; spearthrowers; traps male-female division of labour 92–4, 95 male-male competition 107, 108, 109 Manning, John 108 Marine Isotope Stage (MIS) 129, 293 Martin, Robert 99, 100 Mason, Otis T. 21 meat 93, 104–6, 168 memory 47–8 constructive 49, 151, 174, 194, 272, 289 working 48–9, 198, 289 see also extended mind concept Mezhirich (Ukraine) 273 microcomputed tomography (microCT) 98 microliths 256, 262–3, 264–5, 268, 273–4 Middle Palaeolithic 226, 231, 232 Middle Pleistocene 24, 65, 66, 67, 100, 103, 153 climate change 113–14 human diversity 114–23 see also fire; invention of hafting Middle Pleistocene Transition 11, 19, 127–8, 240 climate change and 128–31, 132, 293–4 in Africa 134–6, 137–8 in Asia 134, 135, 137 in Europe 132–4 see also Olorgesailie

355

Misliya Cave (Israel) 229 mother-child relationship 90–1 Movius, Hallam 144 Movius line 144–5, 159, 231 Mumbwa Caves (Zambia) 215 natural pedagogy 80–3, 84, 85, 89 natural selection 15, 23, 25, 138 see also variability selection Neanderthals 108, 115–16, 118, 119, 134, 153 n., 242, 273 archaeological sites and 224–6, 227 birds and 220–1 brain/genome of 68, 100, 121 extinction of 266–7 right-handedness of 70, 72 tar/adhesives and 218–20, 241 tools and 156, 160, 212, 236 n. see also Homo heidelbergensis neocortex 63, 67, 68, 284–6, 288 neuroimaging techniques 36–7 studying tool use and 38–41, 42 neurons 36, 37, 55, 57, 62, 283–5, 286 mirror 40, 69, 80, 84, 288 neurotransmitters 84, 283–4 New Guinea 18, 61, 81 n. Newton, Isaac 22 Niah Caves (Borneo) 268 nuclei 284 obliquity 290, 291 obsidian 182, 224 ‘Oetzi’ (frozen man) 206 n. Ogburn, William Fielding 20–2, 25, 246–8 Olorgesailie (Kenya) 138–9, 141 opportunity niches 27–8 opposable thumb 57, 58 Oswalt, Wendell 198, 201 Palawan (Philippines) 233 parietal cortex 44, 52, 57, 289 perihelion 290 phylogeny 115, 118, 119 ‘phylogeographic’ approach 251–2 piercing/drilling 180, 183–4, 211–13 pinch grip 60–1, 148 Pleistocene 129–31, 165 Early 130, 146 Late 103 see also Middle Pleistocene; Middle Pleistocene Transition

356

Index

points 262–3 Levallois 229, 231 projectile 212, 226, 232, 233, 236, 239, 252–3, 260–1 see also flakes; spear points/tips Polak, W. 30 positron emission tomography (PET) 36 n. 2, 36 n. 3, 37, 41, 289 postcentral gyrus 287 Potts, Rick 138–40 power grip 56–8, 59, 65, 148 precision grips 58–9, 61, 65, 69, 149 see also pinch grip precision tool-making 59–61 prefrontal cortex 44, 49, 62, 67, 68, 69, 288, 289 premotor cortex 49, 54, 56, 58, 67, 287, 289–90 prepared-core technology 175, 231, 232, 240, 244 primary motor cortex 54, 56, 287, 289 psychology 22, 24 Qesem Cave (Israel) 161–3, 168, 215, 229, 230 Quneitra (Israel) 207, 208, 209 ratchet effect 7, 79, 145, 247, 263 recursiveness 25 ‘Red Deer Cave’ people 122 Rift Valley 135, 137 Ethiopian 224 Jordanian 142, 146, 158 n. see also Olorgesailie Rightmire, Philip 118 Rots, Veerle 225–6 Sahara, the 137, 163 Sahul 134, 268 Sai Island (Sudan) 221–3, 226, 230, 238, 240, 244 sandwich hafts 184, 193, 199, 200 Schick, Kathy 42 Schöningen (Germany) 234–5, 238, 239, 240, 244 Schöningen 12 (Germany) 236, 237, 274 scrapers 154, 157, 159, 180, 199, 200, 209–10, 220, 225 scraping 180, 182–3 Sharp, Lauriston 28 Shea, John 266–7 Shennan, Stephen 95, 96

Siberia 121 Sibudu Cave (South Africa) 264–5, 273–4 Sierra de Atapuerca (Gran Dolina) see Gran Dolina Sima del Elefante (Spain) 116 Sima de los Huesos (Spain) 70, 72 n., 108, 116, 121 single photo-emission computerized tomography (SPECT) 36 n. 3, 37 Sisk, Matthew 266–7 small tool tradition 153, 216, 234 Smith, Holly 99 social constructionists 22–4, 26 social evolution 101, 103–4 social learning 170–1, 194 theory 76–7 spear points/tips 212, 213–14, 219, 225, 226, 227–9, 231–2, 267 spears 12, 184, 190, 199, 200, 211–14, 223–4, 226–7 wooden 234–5 spear-throwers 243, 253–4, 255, 256–8 in archaeological record 259–61, 262, 265 spindles 169, 170, 171–2, 173 spinifex 189, 192, 200–1, 213, 258 split hafts see cleft hafts Spunt, R. P. 54 Sri Lanka 268 Starosele (Ukraine) 220–1 Still Bay industry 229, 262–3, 274 Stout, Dietrich 42, 47 Stringer, Chris 118, 119, 121 Sundaland 134, 135, 137 superior parietal lobule 289 synapses 283 Tabun Cave (Israel) 149 n., 226, 229, 238, 240, 244 tar 187–8 birch/pine 187–8, 189, 206 n., 218, 219, 241 residues 217–20 Tasmania 96, 247, 264 TD6 child (Atapuerca, Spain) 98–9, 100 teaching 80, 82, 83, 84 technological change 15, 21, 23, 31 see also combinatorial evolution technology 17–18, 27–8 see also Arthur, W. B.; composite

Index technology; hand, the; integrative technologies; prepared-core technology technounits 198–201, 241, 254, 258, 272 teeth 70, 71, 72, 87, 103–4 in children 97–9 thalamus 43, 48, 286, 287 theory of mind 5, 80, 88, 92, 106 learning and 83–4 Thomas, Dorothy 246–8 tip cross-sectional area (TCSA) 212, 227, 231, 252, 261, 264, 266 tip cross-sectional perimeter (TCSP) 212, 226, 261 Tonga, the (Zambia) 170–1 tools 289–90 actions and understandings in making hafted 195–8 flake 144, 150 n., 152, 154, 159 hand-held 33, 61, 153, 165, 194, 219, 223, 241, 243 heavy-duty/light-duty 152–4, 167 physics of hafted 179–81 see also cleavers; complex tools; hand-axes; Neanderthals; neuroimaging techniques; precision tool-making;

357

scrapers; small tool tradition; spears Toth, Nick 42 transcranial magnetic stimulation (TMS) 36 n. 2 traps 243, 253, 265, 269–72 in archaeological record 273–4 Twin Rivers Cave (Zambia) 230 two streams model (brain) 44–5 Umm el Tlel (Syria) 220 variability selection 138–40, 174, 279 Victoria West technique 157–8 Wadley, Lyn 273 Wallace, Alfred Russel 11, 246 Watts, Steve 222 weaver birds 6 Wernike’s area 288 Wonderwerk Cave (South Africa) 149, 167 n. Wynn, Thomas 150 Zambia 169–71, 188 see also Kalambo Falls; Mumbwa Caves