Module behaviour

How does the mind work? Colin Tudge explains The Pre-History of the Mind by Steven Mithen, Thames & Hudson, pounds 16.95 The Pre-History of Sex by Tim Taylor, Fourth Estate, pounds 18.99

Two books on how human beings came to be the way we are, by two clever, articulate archaeologists. But while one (Mithen) has gone with the flow of modern evolutionary ideas, brought them together, and generated novel and valuable insights, the other (Taylor) has fought a politically correct but misguided rear-guard action against modernity.

Mithen points out that the explanations of how the mind works have taken two contrasting forms. The influential Swiss psychologist Jean Piaget believed that the mind operates as an all-purpose computer: a general intelligence. Even language is a manifestation of a general ability to process information. But other thinkers argue that the mind is built from a series of discrete "modules" or "domains", and is designed expressly to deal with specific problems. Thus Noam Chomsky suggested that children's ability to pick up language cannot be explained as a general exercise in problem-solving. Human language depends for its versatility and efficiency on its underlying syntax, which is broadly similar from culture to culture although the details differ. Children acquire the ability to apply syntax accurately even though the clues they gain from listening to people around them do not provide nearly enough data from which a general problem-solver could infer the syntactical principles. We must conclude, said Chomsky, that children are born with an innate and discrete ability to handle words in an orderly fashion: a language module.

Others have extended Chomsky's idea and suggested that the human mind is equipped with a range of such modules, each geared to a different task; indeed, Leda Cosmides and John Tooby have recently been comparing the mind to a Swiss army knife - a collection of problem-solving tools, each operating more or less autonomously. Cosmides and Tooby argue that each of these mental tools - modules - has been shaped by natural selection over the past few million years to solve the specific day-to-day survival problems of early humans. Thus our ancestors evolved a face recognition module, a tool-use module, a social exchange module, and so on.

In practice, neither a Piaget-style general computer nor the Chomsky- Cosmides module model seems able to explain everything the mind can do, but Mithen shows how the two can do so together. In an adroit shift of metaphor he compares the structure of the mind to the architecture of a cathedral. The chapels around the periphery, each dedicated to a different purpose, are like the modules; while the central nave approximates to general intelligence.

Now, says Mithen, whereas in the earliest Romanesque churches the chapels and the nave are sequestered behind thick walls with narrow openings, in late Gothic cathedrals the walls are reduced to columns so that people and sounds flow freely between all parts. So it is with minds: in primitive minds the modules are separate, while in the minds of modern healthy adults information flows freely.

It is easy to envisage how this cathedral-like structure has evolved. Mithen suggests that the minds of our very early, shrew-like ancestors were highly specialised, meaning modular: they did a few things well. In the first true primates that evolved from those primitive "shrews" the modules became more integrated, to produce a freer flow of information. Then more modules were added and they in turn became reintegrated, and so on. The emergence of true humans (homeo habilis) around two million years ago coincided with the acquisition of new modules of social behaviour; and modern homo sapiens appeared around 100,000 years ago when these modules were finally reintegrated to produce the computer-like, highly efficient hybrid structure that we still possess. All in all, The PreHistory of the Mind is set to join the canon of essential texts and is also an excellent read.

Tim Taylor has assembled excellent material in The PreHistory of Sex and shows that human sexual behaviour has always been more various than we have been led to believe. At the way-out level, cave paintings from stone-age Italy show a man contriving to have his way with an elk. At a more homely level, man's vision of ideal woman seems to have varied enormously from age to age, from melon-bellied terra-cotta stone-age "Venuses" to modern Twiggies.

How should we explain such variations? Sociologists traditionally did not try: important human behaviour is rooted in culture, they said, and vive la difference. But modern evolutionary psychologists seek unifying features, with origins lying deep in biological history. Thus Devendra Singh of the University of Texas has shown that although stone-age Venuses and modern pin-ups may differ in bulk by 50 per cent or more they all have precisely the same ratio of measurements of waist to hips: 0.7. Singh then shows that women with a 0.7 waist-hip ratio suffer fewest obstetric setbacks, and live longest.

This and comparable ideas from evolutionary psychology are precisely what Taylor needs to bind his observations into a tight thesis of human sexuality, just as Mithen has done for the mind. But what does Taylor do with such insights? He derides them, suggesting that the universal preference for a waist-hip ratio of 0.7 has been prompted by the centrefolds of Playboy.

Singh's work may well be open to criticism but Taylor's reason for rejecting it is silly. Yet it is politically correct (and specifically in the manner of Stephen Jay Gould) to reject all explanations of human behaviour that are biological rather than sociological for (so Gould would have us believe) the biological explanations lead us into "genetic determinism" and the rejection of free will. But they don't or at least, only in knuckle brains. Taylor has been led astray. Gould has a lot to answer for.