A Natural History of Rape: Biological Bases of Sexual Coercion is a scientific history book published in 2000 by biologist Randy Thornhill and anthropologist Craig T. Palmer, which presents the controversial idea that rape evolved as a genetically advantageous behavioral adaptation.
Behavior as evolutionary adaptation
Thornhill and Palmer's argument begins with the statement that all human behaviors are, no matter how indirectly, the result of some evolutionary adaptation (see adaptationism). They note that since the human brain itself, and thus all capacities for any kind of action whatsoever, evolved from natural selection; the only point of dispute is whether rape is only a by-product of some other unrelated adaptation (such as a desire for aggression, domination, etc.) or if rape itself is an adaptation favored because it increases the number of descendants of rapists. The authors are in disagreement over which of these hypotheses will be confirmed by the evidence.
Childbearing ability of victims
Thornhill and Palmer argue that it is possible that the underlying motivations of rapists evolved because they were at one time conducive to reproduction. In the book, they note that the overwhelming majority of rape victims are of childbearing age, suggesting that childbearing ability is involved in a rapist's choice of victims. They also cite evidence that penile-vaginal intercourse is more likely to occur with rape victims who are of reproductive age, which they argue as evidence that men are at least somewhat sexually, and therefore reproductively, motivated.
Psychological adaptations of women
Women, they argue, have psychological adaptations that protect their genes from would-be rapists. "We feel that the woman's perspective on rape can be best understood by considering the negative influences of rape on female reproductive success", they write. For example, the book cites a study claiming that victims of optimal childbearing age suffer more emotional trauma from rape than older women or pre-pubescent girls. They present this as evidence consistent with their theory, as women in the ancestral environment in their post and pre-reproductive years had less to lose, in terms of genetic progeny, by being raped.
Rape as a biological phenomenon
The book calls rape "a natural, biological phenomenon that is a product of the human evolutionary heritage..." akin to "the leopard's spots and the giraffe's elongated neck", which angered many feminists, including Susan Brownmiller, who discussed the book's findings with the authors on NPR.