Just a cock-and-bull tale

What a shame Woody Allen did not have this book to hand when he made Everything You Always Wanted to Know about Sex .... The scene in which he is one of many white-suited sperm waiting like paratroops before the drop could be developed in the light of new research.

A few sperm would be egg-getters, intent on fertilisation. But far more would be blockers, or seek-and-destroy sperm, specialised for dealing with sperm from any competing male which happened to be around.

These are some of the facts of life seen from the point of view of sperm competition. The idea is simple enough. During our evolutionary history enough women have mated with two or more men within the lifetime of an ejaculated sperm - a little over a week - for competition between the ejaculates for fertilisation to shape sexual anatomy and behaviour.

Combine that with a more general sociobiological premise that even complex behaviour is strongly determined by the genes, and you have the basis for an extensive research programme, whose results Robin Baker now wants to present to a wider public.

The result, of course, will annoy those who maintain that virtually every aspect of human sexuality is purely socially constructed. This is the study of sex as if Freud, let alone Foucault, had never written a word. Baker assumes that, in the end, we must take seriously the biological fact that the ultimate function of sex between humans is reproduction.

There is a certain fascination in seeing how far he can take one simple idea through all the variety of sexual behaviour. And the book is also an interesting case study in the tactics of popularisation. It follows a year after a longer academic volume, by Baker and his University of Manchester colleague Mark Bellis, Human Sperm Competition. That book is replete with tables of figures, experimental protocols, and rebuttals of their critics. In this, the popular paperback, Baker refers the interested reader to the scholarly work for "scientific justification for the ideas and claims made in this book".

The new book presents those claims through a series of sexual vignettes, describing in explicit detail what is happening biologically, as well as relating, rather less convincingly, what is going on in the protagonists' minds. In each case, there then follows an explanation of whose sperm are likely to be advantaged by what has just occurred, and how the parties are trying to achieve, or deny fertilisation, now or later.

On this basis, we are offered explanations of infidelity of all kinds (especially on business trips), prostitution, rape (single and multiple), child abuse, male and female homosexuality, oral sex and masturbation. By now, there seems no reason why a further series of chapters should not go on to "explain" paedophilia, say, or foot fetishism, road rage or football hooliganism. The solution to every puzzle is the same: "our bodies simply use our brains to manipulate us into behaving in a way dictated by our programming".

Baker concedes at the outset that the book is a piece of storytelling. As such, it requires a willing suspension of disbelief. That need grows stronger through the book. For some readers, disbelief will set in at the start. Others, who grant some influence of evolution on behaviour, will get through quite a few chapters. Only readers with a deeply impoverished view of their fellow humans will stay with Baker to the end. I am not one of them, but then reviewers should declare their interest: as a vasectomised male, I suppose in Baker's terms I am a conscientious objector.

Jon Turney teaches science communication, University College London.