Evolutionary biologist Randy Thornhill and evolutionary anthropologist Craig Palmer are certain to spawn a lot of heat with their research on an issue as touchy as that of rape. Those who subscribe to the feminist theories of rape being only a patriarchal act have lambasted the book to smithereens. Thornhill and Palmer have been rebuked and derided over and over again for their very approach to the subject. What is becoming increasingly apparent from the schism developing among theorists is to read the book for oneself rather than rely on the opinionated analyses of reviewers from rival camps.

The approach of Thornhill and Palmer is not that controversial that it is being made out to be. Just because they do not tag along with existing theories of rape does not mean theirs lacks any credibility. The two scientists in no way justify the act of rape, as they have been said to have done in many articles that have appeared in the press since their book was released. Their treatise has more to do with analysing why men indulge in such bestial acts from an evolutionary point of view. That, perhaps, is their main fault. Thornhill and Palmer, believers of sociobiology or evolutionary psychology, feel all rape preventive measures are doomed to fail if the problem is not understood from a Darwinian perspective. Such contentions are bound to be looked at through coloured glasses.

Since feminist writer Susan Brownmiller published her Against Our Will: Men, Women and Rape in 1975, her contention that rape has nothing to do with lust but the urge to control and dominate seems to have become the only theory to go by. Rape is viewed as an unnatural behaviour that has nothing to do with sex, and one that has no corollary in the animal world. Rapists, Thornhill and Palmer argue, may have a variety of motivations: wanting to impress his friends by losing his virginity, or wanting to avenge himself against a woman who has spurned him.

The two authors challenge the Brownmillerian theory and assert that rape is, in its very essence, a sexual act. Moreover, rape has evolved over millennia of human history, along with courtship, sexual attraction and other behaviours related to the production of offspring. Rape is as a natural, biological phenomenon that is a product of the human evolutionary heritage. This is where critics have been jumping the gun. The terms "natural" and "biological" are not used to justify the act. Biological, they remind the reader, means "of or pertaining to life," so the word applies to every human feature and behaviour. They also cite the examples of epidemics, floods and tornadoes to drive home their point that what is natural is not always desirable.

The subject of sex remains complicated since men and women perceive it differently. That is why men are said to be from Mars, and women from Venus. This is so not only because boys and girls receive different messages during their upbringing. Human males can reproduce successfully with a minimal use of time and energy: once the sexual intercourse is complete, their work is done. The minimum effort for females includes nine months of pregnancy and a painful childbirth. It is this difference that is the key to understanding the origins of certain important adaptations-features that persist because they were favoured by natural selection in the past.

Individual organisms merely serve as the instruments of evolution. Men today find young women attractive because during human evolutionary history the males who preferred prepubescent girls or women too old to conceive were outreproduced by the males who were drawn to females of high reproductive potential. And women today prefer successful men because the females who passed on the most genes, and thereby became our ancestors, were the ones who carefully selected partners who could best support their offspring.

Thornhill and Palmer cite instances from the animal kingdom and say that males are willing to abandon all sense and decorum, even to risk their lives, in the frantic quest for sex. Forced copulation (rape) too occurs, but the females prefer voluntary mating to mating by force. Males too rape only when they cannot obtain a consent. "That preference for consensual sex makes sense in evolutionary terms, because when females are willing, males are much more likely to achieve penetration and sperm transfer."

It is possible that rape evolved not as a reproductive strategy in itself but as a side effect of other adaptations, such as the strong male sex drive and the male desire to mate with a variety of women. The ability of men to maintain sexual arousal and copulate with unwilling women might mean that they have evolved psychological mechanisms that specifically enable them to engage in forced copulation. In other words, it could be a rape adaptation. The capability to copulate with unwilling women may be simply a by-product of men's "greater capacity for impersonal sex".

The evolutionary concept explains why women of childbearing age is overrepresented among rape victims. The same argument is also valid for the fact that rapists do not necessarily injure their preys: they usually limit themselves to the force required to subdue or control their victims. A particular survey quoted by the two showed that only 0.01 per cent of rape victims were murdered. Here too, the murders took place primarily to eliminate the witness to the rape: the victim herself. Once one understands this point, the school of thought that describes rape as nothing more than an act of violence starts fading out on credibility.

Rape circumvents a central feature of women's reproductive strategy: mate choice. This is a primary reason why rape is devastating to its victims, especially young women. The greatest psychological pain is an adaptation that makes people guard against anything that reduces one's chances of reproducing: the death of a relative, the loss of social status, desertion by one's mate and the trauma of being raped. Rape reduces female reproductive success in several ways. The victim may be injured. If she becomes pregnant, she would have lost the chance to choose the best father for her children. Studies have shown that young women suffer greater distress after a rape than do children or women past reproductive age.

The authors feel insisting that rape is not about sex misinforms both men and women about the motivations behind rape. This, they think, is dangerous since it not only hinders prevention efforts but may actually increase the incidence of rape. They say during the evolution of human sexuality, the existence of female choice has favoured men who are quickly aroused by signals of a female's willingness to grant sexual access. Furthermore, women need to realise that, because selection favoured males who had many mates, men tend to read signals of acceptance into a woman's actions even when no such signals are intended.

The point where the book falters is that it has been rather loosely written, or perhaps poorly edited. But this should not be a valid argument for taking away credit for looking at an issue from a different point of view altogether. Bizarre as it may seem at first glance, Thornhill and Palmer's work must be viewed more seriously than it might (not) merit for trying to demolish conceptions of social scientists that have held sway for about a quarter of a century. It is evolutionary since that correctly explains the origin and evolution of species. There is no reason why it should not explains behavioural patterns either.