This week The É«ºÐÖ±²¥S debate on Darwinism moves to its impact on subjects outside biology. Here Kam Patel talks to psychologist David Buss (below). Overleaf Tim Ingold considers the relevance to anthropology

"My brain? It's my second favourite organ," quips Woody Allen in his 1973 film Sleeper, homing in on the central role that sex plays in human psychology, behaviour and, not least, reproduction. But what is it that brings men and women together for casual flings or lifetime commitments? And why do the sexes so frequently misinterpret each others intentions?

David Buss, professor of psychology at the University of Michigan, reckons he can provide answers to these and many other fundamental questions about human mating. For Buss, one of the leading lights in the rapidly growing field of evolutionary psychology, the answers point clearly to our evolutionary roots. Our ancestors, he argues, faced many of the same problems people face today in attracting, keeping and sometimes discarding a mate. His central argument is that the sexual tactics that have been employed by men and women over human evolutionary history surface in our behaviour and desires now.

This conclusion results from a global survey carried out by Buss and 50 collaborators between 1984 and 1989. The research led to a controversial book by Buss, Evolution of Desire: Strategies for Human Mating, which aims to show that what women want differs fundamentally from what men want and that when sexual strategies conflict, misunderstandings rapidly occur. Men seeking casual sex without commitment upset women while women who withhold sex in order to get commitment and resources anger men. The book also explores the role of sexual conflict in areas such as divorce and sexual harassment.

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In an interview with The É«ºÐÖ±²¥S on a recent trip to London, Buss explained that when he initiated the mating study, "practically nothing was known about our fundamental desires; no one knew whether the desires of people in the Zulu tribe were the same or different from people in China. No one knew whether men and women differed in the fundamentals of their desires and no one knew to what extent they differed from culture to culture. Basically there was a huge gap in the knowledge base for this area."

His goal in setting up the study was to get as many different cultures from as many different racial, ethnic and religious groups as possible. Cultural variations of mating systems - polygynous, monogamous - were eagerly sought. He ended up with 37 distinct cultures - large enough to make sensible conclusions - and a total of 10,047 subjects. Ages ranged from 14 to 70.

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Looking back, Buss finds it "amazing" that he was able to get the data needed. He was fortunate, for example, in having an Iranian graduate who was so fascinated by his ideas that she volunteered to go to Iran and smuggle the data out. Data collection by a collaborator in an eastern bloc country - the study was launched before the fall of communism - started promisingly but was soon discovered by the government which quickly shut down the operation. The collaborator charged with collecting data on the Zulu tribe was exposed to some very violent reactions.

The basic findings of the survey can be grouped in three distinct "clusters". The first cluster covers universal desires which show no sex differences. The key finding here is that everyone wants a mate who is intelligent, kind, healthy, dependable and a relationship where there is love or mutual attraction. The second set of results deals with desires that are universally sex differentiated. Men place a greater emphasis on physical attractiveness or good looks. They also universally desire women who are younger than themselves. The size of the preferred age difference, however, varies. In largely polygynous cultures, men preferred women who were dramatically younger than they were by seven or eight years. But in Britain, Norway and Sweden, for example, the ideal age difference was less. In all cultures though, men in general desire younger partners. For women, the key concern in choosing mates revolves around the male having good financial prospects as well as having the qualities that lead to those prospects being fulfilled - such as a man's ambitions, industriousness and social status. Women also universally desired men who were older than they were with older age being linked to greater resources.

The third cluster of findings focuses on cultural variability, with the desire for chastity being the most culturally variable finding. Cultures like the (mainland) Chinese viewed virginity as indispensable in a mate, while people in countries like Ireland and Japan placed intermediate value on virginity. For the Scandinavians, virginity was an irrelevance.

As well as helping to provide powerful insights into human relationships from an evolutionary perspective, Buss regards the findings as further evidence that the theories that have dominated the social sciences over the past 50 years are wrong. He explains that these have revolved around the notion that we are born with "domain-general, content-free minds with general intelligence and general ability to calculate needs and relationships". These theories carry with them the implication that we are born with a brain that lacks the specific neural architecture to enable, for example, mating strategies to be executed. Buss says: "It is becoming more and more apparent that the domain-general, content-free model of the mind is wildly inaccurate and that what we have is in fact just the opposite. "

He cites research into the process of learning as lending powerful support for the "scientific revolution" that is taking place in our understanding of why we are what we are: "There are some things, like food aversion, that you can learn through a single trial. There are other things that you can test thousands and thousands of times yet still you cannot get the organism to learn. So what that tells you is that we come into the world prepared to learn some things easily and rapidly but that there are other things where this is not possible. There is also the specificity of response associated with phobias and fears - there are plenty of people who are scared of spiders, snakes and heights but they do not develop fear of cars or electrical outlets."

Evidence of "specificity" is also piling up from fields such as artificial intelligence and cognitive neuroscience: "In brain science, researchers are revising their models of the brain and in a way it is really satisfying because what they are ending up with are models that correspond exactly to what is being predicted by evolutionary psychologists."

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Buss also points to the powerful conceptual framework that has been erected to support the empirical work of evolutionary psychologists by colleagues including Leda Cosmides and her husband John Tooby at the University of California at Santa Barbara. The central argument here is that in order to solve an adaptive problem you need specific mechanisms to do it. Buss cites Don Symons, a fellow evolutionary psychologist, who has said that there are no general solutions because there is no such thing as a general problem.

Buss often likes to use the carpenter's tool box as a metaphor for explaining this argument. Saws, a variety of planes, a marking gauge, a mallet - these are just some of the tools a well stocked carpenter box would boast. One cannot expect a carpenter to have just one tool to do all the tasks that are performed by all his tools separately. Similarly, he argues, in order for us to be able to solve different adaptive problems, we need different solutions. Conceptually therefore one should expect a variety of specific neurological mechanisms.

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When he first started publishing his results on mating strategies from an evolutionary perspective, they were met with outright hostility from quarters of the psychology and social science communities: "The findings contradicted the dominant thinking in the field to such a flagrant degree and were erroneously perceived to be incompatible with the dominant political ideology among academics. Some urged that I suppress my findings. I refused to do so. I am a strong believer in facing the truth, regardless of whether it is popular or not."

Buss says that his work is particularly upsetting to older scientists trained in an older paradigm. The sex study also inflamed a lot of people outside academia. He says: "Women get upset at the findings that men are so prone to casual sex, for example, because they don't want men to be that way. But I say don't kill the messenger. We need to confront reality so that we can deal with it."

Creationists, who are antagonistic to evolutionary theory in general, have been heavily critical of his work. And it also riles "those who believe in the infinite plasticity of humans and have been brainwashed in outmoded ways of thinking such as all human behaviour is 'cultural' or 'the product of socialisation'. In fact, there is something in my work to upset practically everybody!" he says laughing.

As for future research, Buss is planning to dedicate the next few years to topics including conflict between the sexes - which he regards as one of the most important social problems of our time. He also wants to take a close look at the "fascinating, complex and understudied" field of status, prestige and reputation.

Born in Indianapolis, Indiana, 42 years ago, Buss's youth did not obviously mark him out for the heights of academia in later years. He dropped out of high school at 17, totally alienated, he says, from his school, family and academia. At the age of 18 though he met a women en route to Amsterdam who totally changed his life. During the three years they were together, he resumed school and went on to the University of Texas at St Austin where he became enchanted with evolutionary theory. "I went from being a terrible student to the top of my class and became a psychologist."

He gained his doctorate at the University of California, ending up inventing a new technique for personality assessment which was well enough received to land him a job at Harvard as an assistant professor. There he met other leading evolutionary psychologists including Cosmides, Tooby and Martin Daly. His own private life revolves around his two children from a previous marriage and his partner Cindy. "She is my soul mate. Marriage is too pallid a concept to describe the depth of our relationship," he says laughing.

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One of his primary academic objectives is the laying down of firm foundations in the discipline upon which future researchers can build. He says: "In social science, work tends to be faddish - here today, gone tomorrow. I try to do work that is important enough to stand the test of time and which will still be read and cited a 100 years from now. Of the work I've done so far, I think the study of mating desires in 37 cultures may end up qualifying."