Geoffrey Miller


How sexual choice shaped the evolution of human nature

Book review by Anthony Campbell. Copyright © Anthony Campbell (2000).

This is a book about a biological mystery. Evolutionarily speaking, the human brain has increased in size at an astonishing rate in a short time, but there is no agreement among biologists about why this has occurred. The anthropoid apes have also acquired large brains, but the differences between us and them are as instructive as the similarities. Above all, our brains permit us to speak, something which no other creature on this planet does.

Hitherto, most attempts to account for the differences between human beings and other apes have focused on the survival value of having a large brain. Possessing a large brain offers the potential to carry out sophisticated behaviour and problem-solving. It also allows more complicated social interaction. One popular theory in recent years has it that we developed a large brain in order to allow us to guess what other members of our group were thinking. However, there's something odd here. If intelligence is so wonderful, why did it take so long to appear? Even today, most mammals manage with relatively small brains. There is no general trend in evolution towards the development of hyper-intelligence. Apart from the apes, only elephants and mammoths, whales and dolphins seem to have gone down the road of acquiring large brains.

Another question concerns the apparent absence of correlation between the enlargement of the brain during human evolution and cultural change. Brain size in our ancestors tripled between two and a half million years ago and a hundred thousand years ago, yet for most of this time our ancestors went on making the same kinds of stone tools. Not until long after the brain had finished enlarging did dramatic cultural change occur. If a large brain provided such valuable survival benefits, why did it take so long for these to be apparent, and what ensured the continued existence of large brains during this latent period?

A third problem is that it is difficult to provide a survival value for most of the things that human minds are good at, such as humour, art, music, self-consciousness, religion, and morality. But if they don't have survival value, why did they develop and why were they maintained?

Miller finds his answer to these questions in sexual selection. This theory was advanced by Darwin as a complement to his theory of natural selection, but for nearly a century it was largely neglected. Miller devotes a chapter to the reasons for this neglect. Here he makes out a strong case for his claim that many of the problems that plague the human sciences today are due to over-emphasis on the role of survival of the fittest; we need, he says, a new way of thinking about these matters.

Sexual selection is important because it is capable of producing features that seem to go into runaway by a process of positive feedback. If females prefer a particular male characteristic, this may increase in size and showiness even to the point where it imperils the survival of its possessors. Examples are the tail of the peacock and, perhaps, the antlers of the extinct Irish elk. Something similar could explain the development of the human brain, and also human mental attributes such as humour, benevolence, and so on. However, it can't be the whole explanation, because men and women have very similar brains. This may be partly attributable to the fact that women require large brains in order to appreciate these attributes in their mates.

Another aspect of sexual selection, which receives a lot of attention in Miller's theory, is that the possession of showy items like brains is an indication of fitness. Females would therefore be expected to favour males who gave evidence of intelligence because this was also evidence that they were fit in other ways. It was no doubt important in the Pleistocene that a man could provide material benefits such as food and shelter, but it was probably much more important that intelligent men could father intelligent, energetic children who were more likely to survive and reproduce, whether or not their father stayed around.

Miller provides a lot of evidence to support his view, not all of it directly related to the mind. Thus, he cites penises, breasts, buttocks, head hair, beards, and full lips as body traits that have been produced by sexual selection through mate choice. He regards art as essentially similar to these, though he is careful to insist that the Darwinian explanation is only part of the reason art exists.

He has a particularly interesting discussion of the evolution of altruism. Much of the theorizing about this in recent years has centred on the benefits of altruistic behaviour for one's kin, but a lot of human generosity does not provide benefit for those to whom the giver is related genetically. While acknowledging the importance of kinship in altruism, Miller favours the view that sexual selection explains generosity to unrelated and indeed unknown people, as in giving to charity. He points out that many people who give to charities are relatively unconcerned with what happens to the funds they donate. This, he suggests, accords with the view that giving to charity serves partly as a fitness indicator. It would also explain why men tend to leave more generous tips than women.

As one might expect, Miller devotes a lot of space to language. He thinks that utilitarian explanations of how language originated are inadequate, because language serves many purposes that are not encompassed by the needs of sheer survival. In outline, he suggests that those individuals who were able to use language most fluently were favoured as mates. This seems plausible, although I was less persuaded by his claim that a large vocabulary, containing many synonyms, is merely ornamental. The poet Robert Graves used to maintain that there was only one pair of synonyms in English (gorse/furze), and I think there is more to be said for the purely functional value of a large vocabulary than Miller allows.

This is a fascinating and important book, well written and full of valuable insights and stimulating ideas. And the question that it addresses is surely an important one. There seems to be a widespread idea among certain philosophers and others, especially those with a mystical bent, that intelligence is a necessary outcome of evolution. Some go so far as to suppose that there is actually a hidden purpose in evolution: the purpose being, naturally, to produce intelligent organisms like ourselves. Leaving aside the question whether it makes any sense to talk about evolutionary purpose, there seems to be little convincing evidence that the development of intelligent life is inevitable. The dinosaurs existed for many millions of years without showing any notable tendency to evolve intelligence. If we destroy ourselves in the next few decades, there is no guarantee that intelligent life will evolve again, any more than if peacocks became extinct another bird with a similar tail would evolve to replace it. Miller's answer to the question of why intelligence arose in our case is an important contribution to the debate, one that is likely to attract a lot of attention from everyone with an interest in the subject.

%T The Mating Game
%S How sexual choice shaped the evolution of human nature
%A Miller, Geoffrey
%I William Heinemann
%C London
%D 2000
%G ISBN 0-434-00741-2
%P 538 pp
Titles | Authors | Subjects