Why do we behave as we do? Because our brains are programmed for a Stone Age way of life, say the new Darwinians. Jon Turney reports on a controversial theory -publicised in Britain by a series of seminars at the London School of Economics. But is it really going anywhere?

Evolutionary psychology is sociobiology renamed for public-relations reasons. So says the popular science writer Richard Dawkins, who knows a thing or two about communication. Sociobiology, which infuriated intellectuals in the 1970s with its central premise that human nature is all in the genes, certainly needed the PR - and what effective PR it has been!

In the past few years, questions as diverse as why step-children are more at risk of abuse and why women do not run large corporations have been explained in the British press in terms of evolutionary theory.

To say that, and to add that the Darwin seminars at the London School of Economics have been the pre-eminent British vehicle for the PR effort, is not a dismissal of Darwinian hype. Ideas, evidence and arguments are never enough to advance an academic movement: a theatre of persuasion is also necessary.

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Also needed are an impresario with a gleam in her eye and a patron. The patron, John Ashworth, has his reasons (see right). The impresario, Helena Cronin, certainly gleams. The fact that they came together at the LSE, then as now largely bereft of anyone doing any actual research inspired by Darwinian theory, supports the idea that the main aim has been popularisation.

So what have the seminars been trying to popularise? And were they successful? The kernel of the enterprise, I think, has always been evolutionary psychology. This elaborates the once unfashionable notion that if we want to understand the human mind, we must understand how it evolved. Its academic manifesto, as written by Leda Cosmides and John Tooby of the University of California, Santa Barbara, says that "the human brain consists of a large collection ofI specialised computational devices that evolved to solve the adaptive problems regularly encountered by our hunter-gatherer ancestors". The programs of these devices, they say, "constitute a precise definition of human nature".

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Much of the appeal of the Darwin discussions, however, has been their secondary aim: to spread the notion that absolutely everything can also be seen more clearly through the lens of Darwinian theory. Here they picked up on a trend that seems to have strengthened in the past decade. It is not just car-makers advertising their latest model who have rediscovered evolution. The idea is newly fashionable in a host of academic disciplines.

But we must be careful to identify which ideas are being carried into new areas. It is true that the logic first spelled out properly by Charles Darwin and Alfred Russel Wallace for living things is quite general. Take a set of things that can reproduce. Vary them as they do so. Link their chance of breeding to the variations between them. Their characteristics will gradually change over generations. Success breeds success.

This is easy to grasp, and it may seem surprising that it took so long for the general scheme to be applied outside biology. But now it finds a host of other uses: in approaches to the chemical origins of life; in Gerald Edelman's "neural Darwinism", modelling the shifting patterns of neuronal connections in the developing brain; Lee Smolin has even created an evolutionary cosmology that explains the fine-tuning of the basic physical constants in terms of the differing reproductive propensities of whole universes.

Some of this is useful; at worst, it is harmless fun. It is idle to pretend that the Darwinian frame can be laid over absolutely anything, but it is sometimes worth a try.

There is, however, a difference between metaphorical and genuine applications of Darwinian theory. What does it mean to say that technology evolves when the variations are not random, the selection is not natural, and the units of selection are not independent? Describing it as a Darwinian process, as Freeman Dyson does in Imagined Worlds, probably obscures as much as it reveals.

Which brings us back to culture, human minds and human nature. It is here that the largest successes of the new Darwinians are trumpeted. One is that evolutionary psychology can avoid the worst excesses of the human sociobiology of the 1970s. Even philosopher Daniel Dennett, who enjoys a reputation for being more Darwinian than Dawkins, concedes that back then there was "an escalation of greedy claims", especially about inferred links between human cultural universals - aggression, incest and so on - and their genetic underpinning.

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The second claim is, of course, that avoiding these excesses is producing a careful body of work that really will build towards that "precise definition of human nature", and perhaps even produce a new paradigm for studying human minds and actions.

Well, maybe, though it depends what you mean by paradigm. Certainly, it is hard nowadays to think about evolution and deny that humans have a nature rooted in their biological past. The intellectual historian Bruce Mazlish, reflecting on the status of the human sciences in his new book, The Uncertain Sciences, argues that everything we know about human beings has to make sense in the light of evolution. But that does not eliminate the interpretive problems of studying the actions of fellow humans.

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A paradigm means more than this. It is not just a new way to identify workable puzzles and define what counts as a solution. It implies that other people accept that the puzzles have really been solved.

Agreeing that the mind evolved does not mean that we can know how it evolved. The story of the life of proto-human hunter-gatherers a few hundred thousand years ago - the environment of "evolutionary adaptation" - is, inevitably, partly a work of fiction. Reading University researcher Steven Mithen points out in Prehistory of the Mind that studies of contemporary hunter-gatherers show their minds work quite differently from strictly modular prediction of Cosmides and Tooby. So, while it is true that evolution is finding its way into psychology textbooks, it is not going to transform the whole discipline just yet.

Meanwhile, some of the claims made have a whiff of the old sociobiology about them. Take Kingsley Browne's account of why women do not run large corporations. This depends heavily on the tricks of language that gave sociobiology a bad name - words such as "risk-taking" and "status" are taken to mean the same when we speculate about hunter-gatherers' lives half a million years ago as they do for a corporate middle manager today. This is not so much a bid to downplay the environment's influence on human behaviour as to abolish it altogether.

Another reason for caution is that the new Darwinian findings seem to have little practical payoff. One of the evolutionary psychologists' favourite topics is step-parenting. True, Martin Daly and Margo Wilson have shown that step-children are at much higher risk of abuse and neglect than natural children. Quick, tell the social workers! Well, yes. But then tell them also that most abuse is still perpetrated by natural parents and that most step-parents are not abusers, and it becomes much less clear what they are supposed to do with the new information.

Or take Darwinian medicine. It is interesting to learn why fever or coughing fits are adaptive responses to infection, but will this stop us trying to suppress these symptoms?

Like most successful popularisers, the new-Darwinists will provoke a backlash. There are already popular books being written that will try to demolish the grander claims of evolutionary psychology. And it is always easy to charge enthusiasts with overselling their ideas. If the batteries in the megaphone proclaiming Darwinism as a Theory of Everything are starting to run down, maybe it would be smart, just for a while, not to replace them. Time for a quieter conversation in which careful research can sort out useful insights from just-so stories.

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Jon Turney is in the department of science and technology studies, University College London.