Give us the proof

From New Scientist: http://www.newscientist.co.uk/opinion/opinion_224421.html

Humans haven't evolved since the Pleistocene. This is why, argue evolutionary psychologists, some of us are driven to kill or rape. Popular with eminent researchers, evolutionary psychology dominates today's media with stories of how everything from infanticide to why women fall for rich men is in our genes. So does evolutionary psychology provide deep insights into human nature? Or does it shift the blame for our worst excesses from society to biology? In an exclusive essay based on their new book, sociologist Hilary Rose and neurobiologist Steven Rose, explain why real life is just too complex for such simple-minded determinism

ARE OUR brains like Swiss army knives, full of built-in devices for understanding maths and detecting cheats? Do men commit rape to pass on their genes? And do we enjoy gardening as an evolutionary throwback to our savannah past? These are some of the claims that have filled the pages of fashionable books alleging that there is a new "Darwinian" science out there, called evolutionary psychology (EP). "Evolutionary" has become a term that can be applied to everything from economics, medicine and sociology to ethics and art criticism.

EP's central argument is that present-day human behaviour has its roots in how our ancestors thought, acted and felt in our Pleistocene past. This behaviour, so the thinking goes, has been fixed by natural selection, regardless of whether or not it is relevant or useful to 21st-century people. But how can we tell how our ancestors behaved in the Stone Age? According to EP, by a process of "reverse engineering". That is, you look at people today and guess how we may have got there through evolution.

With this sort of ungrounded speculation, EP swaggers across the sciences, from evolutionary theory itself to neuroscience, anthropology, sociology and philosophy. Its protagonists insist that with 20:20 prehistorical hindsight, and the application of what they call "Darwinian method", they can offer better explanations of phenomena ranging from child abuse to morning sickness than can criminology or physiology. Sound bites of this sort make good headlines, but can they stand up to rigorous scrutiny?

Darwin mistrusted speculation. His own theoretical conclusions were based on extensive, meticulous observation and careful experimentation. EP's evolutionary assertions ignore both. Let's begin with the idea that we know what our ancestors were doing in the Stone Age. You don't have to have a Nobel prize in palaeontology to know that we can't. When there is still a debate over the sex of Lucy, the hominid whose fossilised remains were dug up in Ethiopia, fantasy constructions of Stone Age family relations sound more like episodes from The Flintstones than examples from a new discipline seeking to be taken seriously. Geoffrey Miller's recent book The Mating Mind goes as far as to include a section speculating on how a Stone Age teenager might have related to her mother's live-in lover.

Then there's EP's claim that the roots of human behaviour haven't changed since the Pleistocene, between 10 000 and 1.6 million years ago. You'd have thought that this would be long enough for us to adapt to new circumstances. But EP's supporters say it isn't. This is a strange assertion given that evolutionary biologists have found that, over successive generations, the leg length of English sparrows transported to the US increased by 5 per cent in a century in response to new environmental challenges. And that patient decades of study of the Galapagos finches by Rosemary and Peter Grant have shown how the birds' beak shapes can alter significantly over a couple of generations in response to periods of drought or abundance. Surely there ought to have been plenty of time in the human generations that have elapsed since the Stone Age for humans to adapt in response to changes in social, cultural and technological conditions--to say nothing of climate change.

What's more, in the 150 years since Darwin, evolutionary theory has moved on. Palaeontologists and molecular geneticists (for instance, Mooto Kimura, Stephen Jay Gould, Niles Eldredge and Gabriel Dover) have added such themes as neutral mutation, punctuated equilibrium, exaptation and adoptation, making it clear that there's no simple formula linking changes in an organism's genes to changes in its physiology. Ignoring such important developments is no way to advance science. As Darwin sighed in the last edition of On the Origin of Species, confronting those who claimed that he regarded natural selection as the only means of evolutionary change: "Great is the power of steady misrepresentation."

Riding roughshod

This insistence on simple-minded evolutionary guesswork enables evolutionary psychologists to ride roughshod over many areas of science. The intricate processes of brain development explored by neurophysiologists and developmental biologists get short shrift from evolutionary psychologists. Steven Pinker, for example, sees neurobiology as irrelevant to his invocation of a universal human "cognitive architecture" based on innate modules apparently generated in the Pleistocene. This description of the mind as an information processing device may suit computer buffs. But for those of us whose minds and brains deal not so much with information as with meaning, and less with emotion than with cognition, Pinker's picture is profoundly unsatisfactory. Unsurprisingly, Pinker's speculative theorising enrages neurobiologists.

But what is perhaps most damaging about EP is its systematic devaluing of serious research in disciplines outside the natural sciences. For example, Canadian psychologists Margo Wilson and Martin Daly theorise, on the basis of their belief that parental love is genetic, that there is an evolutionary propensity for men to abuse or murder their stepchildren. While it is true that the rates of such crimes are higher in families with a nonbiological father, these are still a minority of stepfathers. It is a poor theory which can't explain why most stepfathers do not commit such crimes (New Scientist, 13 May, p 9).

Social research instead points to second families being under tremendous pressure both emotionally--not least because the biological father is still in the frame--and financially. Such proximal explanations, as the philosophers of science would name such contextual accounts, are better grounded than untestable evolutionary speculations.

Perhaps the worst example of such ill- informed assertions comes from Randy Thornhill and Craig T. Palmer in their recent book, A Natural History of Rape. They claim that rape is an evolutionary strategy adopted by otherwise sexually unsuccessful men to pass on their genes. Thus their definition of rape is restricted to the forced penile penetration of fertile women. So victims of forced anal or oral sex or same-sex rape, as well as raped pre-pubescent girls or post-menopausal women, have, according to the authors, not been raped at all. To support their cause they turn to Thornhill's observations of male scorpion flies, which under well-defined circumstances will all proceed to forced sex.

But even though there is plenty of evidence pointing to the social contexts when the incidence of rape increases, there are no well-defined circumstances when all men will rape. Men are just a shade more complicated than scorpion flies, not least because of the evolution of the human brain, to say nothing of the values which bind societies together. Yet Thornhill's claims were talked about and written about in the serious media as serious science. This EP theory of rape is not only poor science. It is also socially irresponsible, as its pernicious influence could set back the struggle being waged in the courts against this violent sexual crime.

Faced with trying to explain why their theories don't actually fit the data, the proponents of EP fall back on a free-floating and unbiologically based "free will". "Only we have the power to rebel against the tyranny of our selfish replicators," proclaims Richard Dawkins. "If my genes don't like what I do they can go jump in the lake," insists Steven Pinker. What gives us such power to tell our genes what they can or cannot do? Darwin, rejecting the notion of free will, knew far better. The exploration of human agency and subjectivity by the social sciences has rather more going for it than this reaching for a sky-hook to escape a problem of EP's own making.

Human behaviour is complex and demands complex explanations. Yet EP is trapped within an almost religious longing for simple-minded explanations. Given a choice between a complex explanation, for instance of why women who are generally poorer should prefer richer men as fathers for their children, and some Just So Story about life in the Stone Age, they prefer the latter. They simply disregard evidence to the contrary, which shows, for instance, that as women become more financially secure they no longer opt for older rich men.

The contributors to our forthcoming book, Alas, Poor Darwin, are drawn from many disciplines, ranging from philosophy, sociology and cultural criticism to animal behaviour, neuroscience and molecular biology. They argue that such grandiose speculations, based on weak or non-existent evidence, both steadily misrepresent Darwin and ignore or dismiss findings and theorising from contemporary research.

But attacking a poor argument is no substitute for replacing it with a better. In consequence, Alas, Poor Darwin accepts the interdisciplinary challenge of EP, but recognises the complexity of the world we live in, and the necessary autonomy of the many disciplines trying to understand and explain it. Lastly, the very interdisciplinarity of the book serves to demonstrate that despite the sterility of the "science wars" between social and natural scientists, it is entirely possible for people from radically different disciplines to enjoy listening to and learning from one another.

Alas, Poor Darwin: Arguments against Evolutionary Psychology, is published by Jonathan Cape on 6 July. Contributors include Patrick Bateson, Gabriel Dover, Stephen Jay Gould, Mary Midgley and Dorothy Nelkin

Hilary Rose is visiting research professor of sociology at City University, London. Steven Rose is professor of biology at the Open University