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Every woman knows not to walk alone in unlit areas at night and to be wary of strange men. Some even enroll in karate classes and arm themselves with Mace. But, as Slate writer Jesse Bering discovers, women may have actually evolved to protect themselves from rape.  While certain animal species have developed physiological defenses against unwanted sex, some research suggests that ovulation sends a signal to female humans to be extra cautious when they are most vulnerable to being impregnated by a rapist. "To say that rape pregnancies are costly to a woman's genetic success would be an enormous understatement," Bering points out. "Not only do such conceptions completely undermine the female's mate selection--and so the quality of her offsprings' genes--but rapists are unlikely to stick around and help raise children, putting such children at a significant disadvantage. In short, it's a catastrophic mess from the vantage point of the mother's genes."

Bering takes us through the research:

Argument for Natural Occurrence of Rape
[Randy Thornhill and Craig Palmer's A Natural History of Rape] presented evidence of what appear to be biological adaptations in human males (as well as males of many other species) specialized for forcibly coercing females into copulation. They argued that rape is an adaptive behavior in certain contexts; for example, when consensual partners are unavailable. There is some evidence that convicted rapists are physically unattractive, at least as judged by women on the basis of their mug shots. And spousal rape is most likely to occur when the husband finds out (or suspects) his wife has been unfaithful, suggesting that he is attempting to supplant another man's seed. (In fact, the distinctive, mushroom-capped shape of the human penis is designed to perform the specialized function of removing competitors' sperm, which indicates an ancestral history of females having sex with multiple males within a 24-hr period.) Furthermore, UCLA psychologist Neil Malamuth and his colleagues found that one-third of men admit that they would engage in some type of sexual coercion if they could be assured they would suffer no negative consequences, and many report having related masturbatory fantasies.

Why Natural Occurrence Doesn't Mean It's Okay

The unfortunate demonization of this brand of inquiry is rooted in the fallacy of biological determinism (according to which men are programmed by their genes to rape and have no free will to do otherwise) and the naturalistic fallacy (that because rape is natural it must be acceptable). These are resoundingly false assumptions that reveal a profound ignorance of evolutionary biology. ... As University of Michigan psychologist William McKibbin and his colleagues write in a 2008 piece for the Review of General Psychology, "No sensible person would argue that a scientist researching the causes of cancer is thereby justifying or promoting cancer. ... "

How Women Seem to Have Evolved to Meet the Threat
When threatened by sexual assault, ovulating women display an increase in physical strength ...

Ovulating women overestimate strange males' probability of being rapists ...
Ovulating women play it safe by avoiding situations that place them at increased risk of being raped. ... At least two studies have demonstrated that women at the peak of their fertility are less likely than their peers to have engaged in high-risk activities such as walking alone in a park or forest, letting a stranger into the house, or stopping their cars in a remote place over the preceding 24 hours. ...
Women become more racist when they're ovulating ... The women who happened to be ovulating scored especially high when it came to fear of black (as opposed to white) men, a fact that the authors interpret as reflecting an evolved disposition to avoid so-called "out-group males," who "may not have been subject to the same social controls as in-group members and would have constituted a threat in antagonistic situations."

Bering's Conclusion, Looking at the Research

I don't know about you, but I'm riveted, and convinced, by much of the logic in this anti-rape area. And researchers are just getting started. Above is a set of astonishing truths that, had an evolutionary approach to studying complex social behavior not been adopted so rigorously over the past quarter-century and applied to human sexuality, would have gone entirely unnoticed ...

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