Kevin N. Laland and Gillian R. Brown

SENSE AND NONSENSE

Evolutionary perspectives on human behaviour

In recent decades we have been treated to vigorous and sometimes bad-tempered polemics between those who think that Darwinism is essential to a proper understanding of human nature and others who regard the whole attempt to use evolutionary ideas in this way as profoundly mistaken and misleading. Some of the argument has been confined to in-fighting among academics but there have also been a good many popular books advocating Darwinian interpretations of human behaviour; these have often been criticised as being simplistic and one-sided, scientism rather than science. Relatively few attempts to look at the question objectively, without taking sides, have been made. Sense and Nonsense is intended to provide a balanced assessment of this kind; fortunately it succeeds admirably and, as an added bonus, it is readable while avoiding superficiality.

Claims that evolutionary thought can illuminate human nature are not new; indeed, they go back to Darwin himself. His ideas influenced psychology in the early twentieth century; many of Freud's concepts derived from Darwin or people influenced by Darwin. In the 1960s popular ethology books such as Konrad Lorenz's On Aggression and Desmond Morris's The Naked Ape had a great success and, according to Laland and Brown, introduced "dubious and sensationalistic evolutionary arguments to the general public". Books of this kind made many people wary of applying evolutionary ideas in a human context.

Even more bitter argument ensued after the publication in 1975 of Edward O. Wilson's Sociobiology: the New Synthesis, followed a year later by Richard Dawkins's The Selfish Gene, which Laland and Brown think may have been the most popular scientific book of the twentieth century. The human sociobiology movement inaugurated by Wilson attracted a huge amount of controversy, being fiercely opposed by many sociologists. Most anthropologists and psychologists continue to ignore sociobiology today, but Laland and Brown make it clear that Wilson's ideas were immensely fertile and gave rise to four other ways of applying Darwinian thinking which they discuss.

The first of these to appear was human behavioural ecology, which is mainly carried out by biological anthropologists and is concerned with ways in which changes in human behaviour may influence reproductive success. Next came evolutionary psychology, generally carried out by academic psychologists interested in the evolved psychological mechanisms that underlie universal mental and behavioural human characteristics. Richard Dawkins, in The Selfish Gene, had put forward the notion of the meme, and this led to the development of a large movement, part-popular, part-academic, known as memetics. At about the time that memetics was developing there also emerged gene –culture coevolution, which is practised by population geneticists and anthropologists some of whom had been critical of sociobiology; Laland and Brown describe it memorably as "like a hybrid cross between memetics and evolutionary psychology, with a little mathematical rigour thrown into the pot".

As Laland and Brown remark, the terminology of these new fields is confusing and so are the concepts; it is almost impossible to find one's way throughout these dense thickets without a guide. Even to keep mental track of the different schools is very difficult, and to evaluate their respective soundness is even more so, but Laland and Brown are excellent guides to the complexities. For each of the five schools they treat they provide a short introduction to explain how it arose and which researchers played an important part in its development. Then they describe the key ideas and methods, touch on some interesting research projects that have been carried out, and conclude with a critical analysis of the arguments and tools that are used. They are able to be fair and balanced because they find all the approaches to be broadly complementary to one another, so that each has something to contribute.

Inevitably, the different approaches are sometimes seen as providing competing views of human behaviour. However, when these alternatives are examined more closely it becomes clear that there is little that is genuinely incompatible about their explanations or methodologies. While there are some theoretical differences, these will eventually be settled by empirical research.

But although they are sympathetic to all the contenders, they are by no means uncritical and don't hesitate to point out instances where claims have been made that seem implausible or are unsubstantiated by research. Particularly at the popular level, there have been numerous examples of ad hoc evolutionary "explanations" for various kinds of human behaviour that don't stand up to serious criticism—so-called Just-So stories. For example, evolutionary explanations for concealed ovulation in women are often advanced, but Laland and Brown suggest that concealed ovulation is in fact the norm and that it is "advertised ovulation" in chimpanzees that requires explanation. The evolution of the menopause, likewise, has been attracted a good deal of attention, and once again Laland and Brown provide a good summary of the issues involved. The point here is that we need to distinguish between the reasons for the existence of a trait such as the menopause and the possible evolutionary advantages of its existence. The two may be different and unconnected. (This is the adaptationist–adaptive question.) Here, as in many other places, the book performs the vitally important function of making readers think and question their previous assumptions.

Sexual behaviour, understandably, has been a principal focus of interest for popularisers of evolutionary psychology. A notable example, discussed in some detail here, is the claim that women find men with symmetrical features attractive and that the explanation for this is that symmetrical features are an indicator of "good genes". For this to work, a number of things would have to be in place. There would have to be evidence for genetic variation underlying female preference and the symmetry of male faces; male facial symmetry and female preferences for it would have to be shown to be heritable; male facial symmetry and female preferences would have to be shown to correlate with fitness; and there would have to be evidence that male facial symmetry is or has been selected sexually (as opposed to naturally). Laland and Brown find that such evidence is largely lacking. They conclude, not that we should give up trying to find evolutionary explanations for human behaviour, but that we should do it better. "There is room for more evolution within evolutionary psychology."

This is an excellent book that should be read by anyone who is seriously interested in the relevance of evolution for human nature.