Jack Horner

assess their own thought processes in an internal dialogue similar to reasoned debate among group members; and to represent features of the world, not just as your perspective or my perspective, but as objectively true, as facts. Evolutionary psychology is a crowded market. There’s no shortage of books telling a story about how chimp-like ancestors turned into modern humans. A Natural History of Human Thinking is part of a sub-genre that sees the problems and solutions as fundamentally social. It was the demands of dealing with other agents, rather than technological problems, that were the primary drivers of human evolution, and these demands were met, not by expanding and adjusting general-purpose cognitive mechanisms, but by evolving distinctively social ways of thinking. Within this sub-genre, Tomasello’s book has two major selling points. First, following Sterelny’s The Evolved Apprentice (2012), it makes a serious attempt to bridge the gap — to explain the kind of cooperation that must already have been in place to enable the evolution of language and culture. This is the crucial ‘joint intentionality’ stage of Tomasello’s model. Second, it is more cognitive than other, similar stories — it tries hard not only to reconstruct the behaviour of our forebears, but to explain what was going on inside their heads. Both of these ambitions are fulfilled only in part. The problem with Tomasello’s bridge is that he attempts to support it with studies of young children, who are not a good model of culture-less, language-less early humans. The language of oneto three-year-olds may be limited, but their behaviour and ways of thinking have already been shaped by thoroughly modern humans — their parents and other caregivers. Acknowledging this kind of evidential problem, Tomasello suggests that it is the logic of his stage model that really counts. No matter when or exactly how they did it, our ancestors must have gone through something like joint intentionality to get from a chimp-like state to our current way of life. Well, yes and no. Yes if we accept this book’s characterisation of the start and end points. No if we doubt, along with many primate researchers, that chimpanzees are quite as smart as Tomasello suggests, or, in the company of some linguists, that modern humans are really so keen to inform rather than manipulate in their use of language. But even if we embrace the sequence of three stages — which is certainly plausible and clearly drawn — if it’s only the logic that counts, the sequence might unfold ontogenetically, wholly in the course of human development. Perhaps we are born competitors with individual intentionality and become pair-wise collaborators with joint intentionality through the enculturation and language learning which give us, in maturity, collective intentionality. A natural objection to this idea is that there must be some inborn differences between us and our chimp-like ancestors — genetically inherited cognitive adaptations — that make possible enculturation and language learning. That is surely right, but Tomasello’s analysis is pitched so high — so preoccupied with intentionality — that some good candidates may be overlooked. Drawing on the work of philosophers and historical figures in developmental psychology, such as Vygotsky and Piaget, but ignoring contemporary cognitive science and neuroscience, this book is resolutely focused on the most complex kinds of thinking. It overlooks the myriad ‘subpersonal’ processes that go on inside our heads — the perceptual, attentional, motivational and motoric mechanisms that beaver away below the intentional surface. It could be genetically-based changes to these mechanisms — such as the inborn human tendency to look at faces, and to enjoy contingent interaction — that lay the foundations for enculturation. But these reservations should not detract from Tomasello’s achievement. Especially when discussing communication, the breadth of his scholarship and clarity of his analysis are truly impressive. There’s a tendency in evolutionary psychology and beyond to see language as the Rubicon — the thing that changed everything — but very few authors are able to lay out in detail the full range of challenges and opportunities that language presents. So, in this respect and many others, this is an important book. It offers a subtle and authoritative contemporary statement of the view that human thinking — which yields both beautiful ideas and nasty Skimmingtons — is naturally and fundamentally social.