Thinking Big

How the Evolution of Social Life Shaped the Human Mind

Robin Dunbar

• Verlag: Thames and Hudson Ltd
• Jahr: 2014
• ISBN:
  9780500772133
• Thema: Historia
• Thema: Historia antigua

Tested against archaeological evidence, this pathbreaking and provocative book shows we still inhabit social worlds that originated deep in our evolutionary past.
Our virtual contact lists, whether on Facebook or Twitter, are on average about 150 - the so-called 'Dunbar's Number' - some three times the size of those of apes and our early ancestors.
- When and how did the brains of our hominin ancestors become human minds?
- When and why did our capacity for language or art, music and dance evolve?
The fruits of over seven years of research, 'Thinking Big' suggests that it was the need for early humans to live in ever-larger social groups that drove the enlargement of the human brain and the development of the human mind.
The three authors are co-directors of the research project 'Lucy to Language' the Archaeology of the Social Brain'. ' 'Thinking Big' is destined to become a classic' - Brian Fagan, Emeritus Professor of Anthropology, University of California.

The history of human evolution is an iconic story that never ceases to mesmerize and enthral. Buried in our past is one of the triumphs of evolution, the story of how a common-or-garden African ape began to change both its body form and the way it lived its life – and how in doing so, it eventually became the dominant species on earth. It is only within the last century that we have really come to appreciate the grandeur of this story and the moments of uncertainty and near-extinction that threatened it.

From small beginnings

Some 7 million years separate us from the time that the ancestors of humans and chimpanzees were a single species: a small, undistinguished African Miocene ape.¹ We finished that part of our story in the last 5000 years as the only animal to have settled all the terrestrial habitats of the earth, from the tropical forest to the arctic tundra and from high mountain plateaux to small islands in the remotest oceans. During that long history the size of our brains trebled and our technology progressed from simple stone tools to digital marvels. We walked upright, spoke, made art in profusion and crafted worlds of enormous imaginative complexity in the name of religion, politics and society. Truly, we are no longer apes.

For most of these 7 million years we were not alone. Where our remote ancestors lived they often shared the space with other closely related species. This ancient pattern began to change within the last 100,000 years when people like us, modern humans, moved out of Africa and through the Old World. Older species like the Neanderthals of Europe and Western Asia were displaced and became extinct. These same modern people also passed beyond the boundaries of the Old World, peopling for the first time Australia and the Americas. By the time the last Ice Age ended 11,000 years ago, we were the only species in town; Homo sapiens was now alone, in an evolutionary sense.

Soon we also became a global species. The move to farming led in one direction to cities, civilizations and a massive increase in population. And in another direction the domestication of plants provisioned the voyages into the remote Pacific, beginning 5000 years ago, while harnessing the power of animals made it possible to traverse cold and hot deserts. No wonder then that the European voyages of discovery found people everywhere; what is more, these explorers tested time-and-again the historical circumstance of Homo sapiens as a single biological species through successful, if not always consensual, interbreeding.

We still carry this 7-million-year history in our bodies and our brains. The scientific insights that arise by comparing our own anatomy and that of the great apes have been essential for understanding the process of evolution, and a revolution in genetics has opened up new evidence for tracing ancestral lineages using both modern and ancient DNA. Fossil skeletons, skulls and teeth have also received forensic attention for the evolutionary information they contain. At the same time, archaeologists have charted the development of technology and tackled key issues concerning diet and the behaviour that ensured a reliable food supply. The result is a much richer and better-understood record of our earliest history.

We began our scientific careers in the late 1960s when the landscape of human evolution was very different. There were few fossils and science-based techniques of dating (led by radiocarbon) were still in their infancy. Getting to see sites and materials was both difficult and expensive until the jumbo jet transformed international travel in 1970. Computers filled entire basements and had to be programmed with punch cards. There were no touch screens or search engines and as postgraduate students the greatest luxury we had was a photocopier, expensively producing images on shiny paper.

It is easy to be dazzled by the rate of technological change and the speed with which new data about our earliest origins have built up. The beginning always seems small by comparison with the present. But small should not be taken to mean unimportant. We will show in this book that for all their sophistication those material changes are still directed at solving some age-old issues of being human. These concern our social lives, which we believe have been largely ignored in the study of our origins.

Our major proposition in this book is that a link has always existed between our brains, or more precisely the size of our brains, and the size of our basic social units. We see this link as essential to understanding our evolution as a single, global species that can live in cities the size of Rio de Janeiro, drawing daily on vast amounts of information to manage our lives. But inside today’s global citizen is a social being who carries forward a social life that in its basics is very similar to one 5000 or 50,000 years ago. At the core of this social life is the observation that a limit of about 150 exists in terms of the size of your social network. This is known as Dunbar’s number, as one of us, Robin Dunbar, did the research that established the figure. This limit is almost three times greater than the chimpanzee’s, which immediately raises the evolutionary question of how did this increase occur? It also begs another question: if the limit is 150, then how come we can live in such large cities and align ourselves to massively populous nations the size of China or the United States?

Our aim in this book is to trace the evolutionary journey from our small beginnings to the present position. Our principal guides are psychologists and archaeologists, although many other disciplines have been involved. With our social perspective on human evolution, we have set out to learn about the following central issues:

• Is there a limit in our brains, our cognitive ability, that restricts the size of the social groups we can live in?

• If so, how did our cognitive ability evolve to cope with ever greater numbers of people, as societies grew from the small social worlds of hunters to today’s mega-cities?

• Given that our ancestors had much smaller brains than ours, what do we mean when we talk of a social life in the remote past?

• Will it ever be possible to say when hominin brains became human minds?

The list above could of course be much longer, but these core questions indicate our interest, first and foremost, in the social rather than in a history of technology or the architectural details of fossil skulls. They also point to our concerns with cognitive matters, the business of understanding how and why we think and act the way we do. Our approach is underpinned by evolutionary theory and our goal is to apply the insights from an experimental subject such as psychology to a historical discipline such as archaeology. This is rarely attempted and never easy. But first some background.

The germ of an idea takes shape

In 2002, the British Academy, the UK’s national body for the humanities and social sciences, launched a competition for a research project to celebrate the centenary of its foundation. It proposed to give the largest single grant it had ever made to a flagship project in the humanities and the social sciences. Although our individual perspectives and interests had been quite different, the three of us had spent most of our professional lives immersed in the story of human evolution. One of us was a Palaeolithic archaeologist with a primary interest in Africa, one a social archaeologist with a special interest in late Palaeolithic societies in Europe, the third an evolutionary psychologist with a principal interest in human and primate behaviour.

It seemed to us, contemplating the opportunities that such a project might offer, that we were perfectly placed to rise to the challenge that the British Academy had thrown down. We had the single biggest question one could ever ask (how did we come to be human?) and we could bring novel expertise to bear on the question. Where past studies of human evolution had been obliged to concentrate on the limited physical evidence that was available (the stones and the bones), we were fortuitously in a position to exploit recent findings about social behaviour and brain evolution in a way that might illuminate the significance and meaning of the stones and the bones. Moreover, archaeology was in the humanities half of the Academy and psychology in the social sciences half, so we could bridge the divide over which the Academy presided, offering an iconic example of how to do interdisciplinary research. We quickly became galvanized with enthusiasm, put our heads together and sent in a bid.

The possibilities that such an endeavour offered seemed positively limitless. The academic world was just beginning to grapple with the integration of psychology and archaeology. The previous decade had witnessed the creation of cognitive archaeology under the driving force of the British archaeologist Colin Renfrew and the American archaeologist Thomas Wynn. The main focus of this approach had been understanding the cognitive demands of toolmaking and the production of works of art. But we felt that recent developments in our understanding of the behaviour of our nearest living cousins, the monkeys and apes, and in the processes underpinning important areas such as brain evolution, would enable us to go one step beyond to say something about the social life of hominins (see Table 1.1), and to do so much further back in time than most cognitive archaeologists had previously dared to go. In particular, the theory that had become known as the social brain hypothesis – the idea that the brain had evolved to allow animals like monkeys and apes to handle an unusually complex social world – offered novel insights and rich seams to exploit in the exploration of hominin social evolution.

Anthropoids		All primates (monkeys and great apes and their fossil ancestors), hominins and humans
Hominids		All great apes (gorillas, orang utans, chimpanzees, bonobos, gibbons), hominins and humans
Hominins		All our fossil ancestors (Ardipithecus, Australopithecus, Homo)
Humans		Only modern humans, Homo sapiens
Anatomically modern humans		Homo sapiens but without substantial evidence for our cultural accoutrements (art, burials, ornament, musical instruments)

Table 1.1: Common terms in human evolution.

Our bid was grandly entitled Lucy to Language: The Archaeology of the Social Brain. Lucy was the iconic early australopithecine fossil that had been unearthed by the palaeoanthropologist Don Johanson and his team in the deserts of northeastern Ethiopia in 1974 (it was named after the Beatles’ song Lucy in the Sky with Diamonds, which had been playing on a tape recorder when the fossil was unearthed). Lucy and her family had lived around 3.5 million years ago, and marked the earliest well-documented hominins. Since the australopithecines still shared many similarities with our common ape ancestors – at least in terms of brain capacity – it seemed like the obvious place to start our story. Language marked the appearance of modern humans, our own kind, and seemed like a natural end point. And so the project acquired its name.

After submitting our proposal, we could only sit back and wait. It is not easy to get funding for research in the sciences or the humanities these days in any country, so we were under no illusions about the outcome. The funding rates of the UK research councils are notoriously low, with only about 10 per cent of proposals actually receiving grants – despite the fact that almost all of those submitted involve exciting, novel and innovative science. We fully expected to be presiding over yet another failed bid. So it was with some surprise and excitement that we heard that our project had been shortlisted for the final interview stage. We were in with a chance!

In the end, of course, this particular story had a happy ending, or we wouldn’t now be writing this book. Ours was the project that was selected by the British Academy as its Centenary Research Project. It turned out that the competition had been much tougher than we had imagined. There had been more than 80 other proposals submitted. Many other potentially exciting projects had faced disappointment, with all the attendant wailing and gnashing of teeth as is inevitable under such circumstances. But, with money for a seven-year project assured, all we had to do was put together a team of exciting young researchers and venture purposefully into the unknown. Thinking Big is the story of our project.

The social brain and its evolution

The centrepiece of our project was the social brain hypothesis. This had taken its first hesitant steps in the 1970s when it was pointed out that monkeys and apes had much bigger brains relative to body size than any other animals. Pondering this, a number of primatologists more or less independently suggested that this was probably because monkeys and apes live in unusually complex societies. Later, during the 1980s, the primatologists Andy Whiten and Dick Byrne, of the University of St Andrews, suggested that what made primate societies so complex was the behaviour of the animals themselves. A monkey group wasn’t like a beehive, which has enormous structural complexity arising from the fact that different individuals are programmed to perform different tasks...