The answer to the question posed by the title, How Many Friends Does One Person Need?, is, according to Robin Dunbar, 150. Or, rather, no more than 150. This figure has become known as ‘Dunbar’s Number’ and is based on extensive studies conducted in a wide range of societies. If nothing else it should provide comfort for those who cast a jealous eye on the absurdly high friend-count some people manage on social networking sites: the chances are, most of these people are not ‘true’ friends.

This is, of course, something most of us will have long suspected, and herein lies the appeal of Dunbar’s new book. Using his extensive knowledge of anthropology and evolutionary psychology Dunbar looks at the everyday habits of homo sapiens and provides neat theories and explanations as to why they should be as they are. His discussion of Dunbar’s Number takes in such diverse subjects as the African savannah, the success of the Gore-Tex brand, Christmas cards and the Domesday Book. Areas of human experience which may have previously seemed like unexplainable peculiarities, or off-limits to rigorous science, are opened up by the author’s wide-ranging study.

Dunbar applies his theories to a myriad of subjects, including gossip, language, kissing, religion and lonely hearts ads, and each is investigated in the light of what we know about our biology and evolutionary history. The first half of the book focuses mainly on some of the oddities of human behaviour, and social or personal aspects of our species; the second half seems to focus more on ‘big questions’ such as our innate attraction to dichotomy in intellectual discussion, morality, and climate change. There is certainly some fascinating content to be found here, including his discussion of jurisprudence which ends with an elegant evolutionary-informed argument in defence of profession juries qualified to understand the complexities of each case. However, it sometimes feels as though Dunbar is hindered by the weight of these subjects, and loses sight of book’s subtitle ‘Dunbar’s Number and other evolutionary quirks’. Some the discussions barely touch on evolution, and in a section on memory he ‘hazards a guess’, with no experimental evidence, that rote learning plays an important role in developing a capacity to memorise, thus abandoning the principles of scientific method altogether.

That said, the sheer breadth of Dunbar’s interest, his sense of humour, and the speed at which revelations occur certainly makes for highly enjoyable reading and this book will certainly leave you with fresh insights into the behaviour of our beguiling species. In its approach it owes more perhaps to popular science such as Does Anything Eat Wasps? than to The Selfish Gene, a fact attested by the author’s acknowledgment that the book grew out of a series of articles he published in the New Scientist and The Scotsman, but this is certainly not a criticism. For those who are seeking an introduction to the exciting work being done in the field of evolutionary psychology I can think of no better place to start.

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