Social Brain, Distributed Mind (Proceedings of the British Academy) [Hardcover]

Brains do not appear in the fossil record. Of course their housings do, and we can learn much from the study of the size and shape of skulls. We can also learn much about brain evolution by comparing contemporary species whose brain development we believe corresponds to that of some long-extinct species. These techniques, however, tell us only a limited amount concerning the evolution of human cognition. This volume, assembled by Robin Dunbar and his associates, brings an astonishing array of experts from various fields (archeology, anthropology, geography, psychology, paleontology, history, and philosophy) focusing rather single-mindedly on the construction of a plausible ``cognitive anthropology.'' The volume suffers some from being a virtual transcript of the proceedings of a 2008 conference, as some of the papers are tangential and others are woefully poor (I speak especially of the chapter by Hui and Deacon, who appear never to even have looked as the behavioral literature on human cooperation). These lapses are more than made up for by some truly exciting and informative contributions by the towering figures of their respective fields.

All participants accept some version of Dunbar's "social brain" hypothesis, according to which the precipitous increase in the volume of the hominin brain some 600,000 years ago was due to the adaptive value of hominins living in rather large social groups in which social networking and working social memory requirements were very demanding. On the other hand, all accept the assertion that hominin material culture, including art, hafted tools, crafted containers, architecture, and written language appear in the historical record less than 70,000 years ago. What went on in all the intervening years? Indeed, what was the purpose of social complexity if not to promoted advanced fitness-enhancing material technology?

This book puts forth a compelling very long-run chronology of hominid evolution, beginning with the increase in social networking some 3 million years ago, the emergence of stone technology some 2.6 million years ago, the beginning of encephalization 2 million years ago, the harnessing of fire and the acquisition of language about 1.7 million years ago, leading to decreased gut size made possible by cooking food and freeing up resources for increased encephalization.

The authors rarely conflict in providing an answer to the riddle of the long lag between increased brain capacity and "modern" material culture. They argue that "not all cognition takes place in a brain" (p. 19), but rather humans developed "artificial memory systems" in the form of tokens and containers that constituted a "distributed cognition" linking the mental power of many individuals, and leading to a transition from "experiential" cognition as exemplified by apes to the "relational cognition" characteristic of humans. For instance, humans have formed fission-fusion social groupings in which kin relations are maintained across social groupings, both males and females migrate to marry, and complex, powerful, fitness-enhancing familial alliances are sustained (Chapais 2008; Hill et al, Science 2011). By contrast, even though they often live together or nearby, chimpanzee males do not recognize their fathers or their children, and migration for mating leads to a total rupture of social relations in ape societies.

The social brain hypothesis is compelling, has lots of evidence, and the notion of distributed cognition fits well with gene-culture coevolutionary and rational actor decision-theoretic models with which I am familiar. I would like to see more abstract models of how fission-fusion and distributed mind operate and might have evolved. It is all to easy to propose verbal models that in fact cannot be supported by the sort of accounting principles offered by mathematical models that clearly represent the incentives facing agents, their capacities, and the precise way in which social cooperation is structured and maintained.

There is animportant piece of the argument missing from this collection. It is an analysis of why hominid groups benefitted from large size and close interpersonal interactions. It must have been this that provided the ambient environmental conditions that rendered social intimacy so fitness enhancing. I believe that hominids filled a niche in which a high level of cooperation and coordination was required to scavange and hunt megafauna, and the presence of lethal weapons undermined the social dominance hierarchy characteristic of our ape ancestors, creating a proto-democratic political structure in which persuation and subtle coalition-formation were key to survival. The social brain is mainly for operating successfully in such a cooperative/flexible framework. Managing interpersonal relations may be important in this context, but there zero chance that they are the central reason for encephalization in hominids. Why? Because unless there were group-level benefits to encephalization, hominids would have been outcompeted for the same niche by other primate species that forwent the complex interpersonal relations, and sufficed with a smaller brain.