One would have to have been living on Mars not to have encountered the increasingly popular notion that our behaviour has an evolutionary explanation. According to evolutionary psychology we behave as we do because we are designed to optimise the chances of our surviving long enough to reproduce. Men who sleep with a lot of women or traders who aim to maximise their returns on their investments are simply responding to the fundamental biological imperative to make the world safe for their genes.

You may think that you chose your mate because she was kind and witty and shared your view of the world. Forget it: you were attracted to her because she had a waist:hip ratio that approximated to 0.7 - a figure that is associated with good health and fertility. As for your political or religious beliefs, they improve your chances of survival or that of the group to which your belong. You haven't chosen them; they have chosen you.

Not everyone is persuaded by the terrible simplificateurs who preach the gospel of evolutionary psychology. The extent to which our behaviour is determined by our evolution is to be debated at the annual Battle of Ideas at the Royal College of Art this weekend. The initial attractiveness of the notion that it is our genes, and not our thoughts, or our conscious agency, that guide our lives is understandable. Has not Darwin demonstrated that human beings were manufactured by the same processes that gave rise to chimpanzees, sea slugs and centipedes? And are we not living now because we have bodies and behaviours that maximise our individual or collective fitness? What makes us think that human beings engaged in the manifestly biological act of choosing a mate are any different from other creatures?

Well, the facts of everyday life for a start. The enormously complex events that culminate in two individuals deciding to share their lives, consisting to an important degree of a very long sequence of conversations, has no counterpart in the pair-bonding processes even of our nearest primate kin. It is easy to persuade ourselves otherwise by describing animal behaviour in anthropomorphic terms and human behaviour in “animalomorphic” terms. Words such as “mating behaviour” and “courtship” shuttle back and forth between the human world and the animal kingdom.

We can see this linguistic pincer movement on the gap between humans and animals at work everywhere in evolutionary psychology. I take you out for a meal. You, aware that recent events have turned my house into a mound of negative equity, falsely declare yourself full after the main course, in order to spare me the expense of a pudding. A chimpanzee reaches for a banana. In both cases, we see examples of “feeding behaviour”, but the differences glossed over by the use of identical terms are enormous.

Even evolutionary psychologists can occasionally see what is in front of their noses and look for ways to fill the Great Ditch that separates humanity from animalists. The landfill they need to make their approach to human behaviour seem halfway plausible is provided by the concept of the meme, introduced by Richard Dawkins more than 30 years ago, and now ubiquitous. While the gene is a self-replicating unit by which biological characteristics are transmitted, the meme is a self-replicating unit by which cultural characteristics are transmitted. Dawkins gives as examples “tunes, catch phrases, clothes, ways of making pots or building arches”. The influential philosopher Daniel Dennett believes that human consciousness is a huge complex of memes. The key feature of memes for evolutionary psychologists is that they replicate by occupying human minds, which accept them as passively as does a brain invaded by a virus. We do not choose our memes; our memes choose us. This is a desperate attempt to save the appearances - in this case the facts of ordinary human life that are utterly different from those of ordinary animal life - in the face of a theory that has difficulty accommodating them. Just how desperate is manifested in some of Dennett's examples of memes: the SALT weapons agreements, faith, and tolerance for free speech. It is difficult to think of tolerance for free speech as something that infests my passive mind as a unit. On the contrary, it is a principle that is argued over within and between people. I think about it each time I encounter an expressed view that I abhor or that I know will offend someone else. Such tolerance requires active, conscious assent. And many so-called memes - ideas, for example - far from being inescapable and unchosen as genes are, require hard work.

Meme theory, which sidelines human agency and pictures the human mind as something between a junkyard and a lumber room, is the reduction to absurdity of evolutionary psychology. It is what happens when science gives way to scientism; when Darwinism is traduced and Darwinitis results.

Raymond Tallis is author of The Kingdom of Infinite Space: A Fantastical Journey around Your Head (Atlantic Books)

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