Behavior resembling rape in humans can be seen in the animal kingdom, including ducks and geese[citation needed], bottlenose dolphins,[1] and chimpanzees.
In which the male may gain sex from the female either by presenting a gift of food during courtship or without a nuptial offering, in which case he rapes her.
"[4][better source needed] Thornhill and Palmer write that "In short, a man can have many children, with little inconvenience to himself; a woman can have only a few, and with great effort."
"[5] Anthropologist Edward H. Hagen states in his Evolutionary Psychology FAQ from 2002 that he believes there is no clear evidence for the hypothesis that rape is adaptive.
Other research has found that during the fertile phase of the menstrual cycle women perform fewer behaviors that may increase the risk of an assault.
[9] Thornhill and Palmer write that "Rape is viewed as a natural, biological phenomenon that is a product of the human evolutionary heritage".
They further argue that a good knowledge of the causes of rape, including evolutionary ones, are necessary in order to develop effective preventive measures.
[7] Wilson et al. (2003) argue that evolutionary psychologists like Thornhill and Palmer use the naturalistic fallacy inappropriately to forestall legitimate discussion about the ethical implications of their theory.
They further argue that if one combines Thornhill and Palmer's factual premise that rape increases the fitness of a woman's offspring with the ethical premise that it is right to increase fitness of offspring, the resulting deductively valid conclusion is that rape has also positive effects and that its ethical status is ambiguous.
Kimmel argues that younger women are the least likely to be married and the most likely to be out on dates with men, and therefore are the most likely to be raped because of opportunity arising from social exposure and marital status.
[12] Smith et al. (2001) criticized Thornhill and Palmer's hypothesis that a predisposition to rape in certain circumstances is an evolved psychological adaptation.
Their model suggested that generally only men with a future reproductive value of one-tenth or less of a typical 25-year-old man would have a net positive cost/benefit fitness ratio from committing rape.
On the basis of their model and parameter estimates, they suggested that this would make it unlikely that rape generally would have net fitness benefits for most men.
She characterises the view of Thornhill and Palmer as "extreme" (p. 736), as they fail to allow for the influence of any non-sexual motivations in the crime of rape.
Vandermassen also notes two problems with the data cited by Thornhill and Palmer regarding the psychological trauma caused by the violence associated with rape: firstly, the data is inaccurately and confusingly presented in the book, often obscuring the fact that they do not support Thornhill and Palmer's "counterintuitive hypothesis" (p. 744) that more physical violence during rape is associated with less psychological pain.
[15] Hamilton (2008) has criticized Thornhill and Palmer's definition of rape as the coerced vaginal penetration of women of reproductive age.