How might a scientist explain Max Mosley? In his 1919 essay A Child Is Being Beaten, Sigmund Freud described S&M as a universal human fantasy, but why should a man wish to beat and be beaten?

The first thing to understand about sexual intercourse is that it is not - His Holiness The Pope's pronouncements notwithstanding - primarily about reproduction. It is about co-operation. Consider homosexuality. As Bruce Bagemihl described in his book Biological Exuberance, more than 450 species engage in homosexuality, and for many of those species homosexuality is the predominant form of sexual expression. More than 90 per cent of sexual encounters for male giraffes are homosexual, for example, and male walruses are almost as gay. Bonobo chimpanzees, moreover, will be relentless lesbians, while hedgehogs are into girl-on-girl cunnulingulus. These animals derive mutual pleasure from their same- sex alliances, which they translate into friendship. Consequently they co-operate in hunting or childcare or other challenges. Thus we see that reproduction is only one use Nature makes of the alliances that flow out of the mutual pleasure of sex.

Nature's most important alliance, however, is the pecking order. Many animals are social and Nature has had, therefore, to identify a method of government. Nature could have settled on democracy, say, or laissez faire, but instead animals are generally ruled by autocracy. As was noted a century ago, hens peck each other - but not randomly. Some hens peck, others are pecked. And that hierarchy is found in all social animals.

The hierarchy emerges in youth: each generation, as it leaves the protection of the parents, fights for status. Soon certain individuals routinely win, and others lose, and the losers accept the winners as their bosses. A pecking order has thus been established. But to maintain the pecking order, the losers need to accept their subordinacy: they need to embrace a psychology of masochism, actively lusting after the lash of Max's whip. Meanwhile, the winners, charged with maintaining order, need to adopt a sadistic personality, they need to enjoy punishing malefactors and free riders. Freud was not the first to notice this: 2,000 years ago Publilius Syrus wrote that “tears gratify a savage nature, they do not melt it”, while Ovid maintained that “pleasure is sweetest when 'tis paid for by another's pain”. More recently, in a paper published in Nature, Anna Dreber and her colleagues from Harvard University confirmed by the classic psychologist's experiment of the “prisoners dilemma” that the evolution of pleasure in punishment can best be explained by the evolution of the hierarchy.

So if sex is a means by which we cement our relationships, and if our relationships are innately hierarchical, then it is not surprising that punishment is hardwired into intercourse. Max's predelictions, though extreme, are not hard to understand.

Terence Kealey is the author of Sex, Science and Profits

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