Not that the title “Darwin’s Rape Whistle” gave me much cause for hope, but I knew that Jesse Bering’s new article on Slate would end in a mess when its first paragraph seemed to be headed toward an epic example of mansplaining.
Women, gather round, read carefully, because this gay man—who once, long ago, feigned sexual interest in your bodies—is about to shine a spotlight on some hidden truths about your natural design. It’s by no means a perfect system, but evolution has endowed you with some extraordinary, almost preternatural abilities to prevent your own sexual assault. And these abilities are especially pronounced when you’re ovulating.
This news will surely be a consolation to the women caught up in the roughly 90,000 recorded rapes in the U.S. alone in 2009, notwithstanding those “preternatural” evolved safeguards.
Bering then cites a quartet of papers from the evolutionary psychology literature in support of the conjecture that when women are at the peak of their fertility each month, around ovulation, they exhibit traits that might help them better resist or avoid being raped. Those traits are (1) greater strength in the face of sexual threats, (2) a greater tendency to see strange men as sexually threatening, (3) greater avoidance of situations that might put them at sexual risk, and (4) greater fearfulness of men of other races (which is seen as a proxy for fearfulness of men from unknown groups).
Evolutionary biologists PZ Myers and Jerry Coyne ripped into Bering’s article on their blogs, faulting both the tone of the story and the quality of its argument. They point out, among other problems, that the genetic basis of those traits has never been established (and so cannot be clearly shown to be evolutionarily adaptive) and that the studied groups of women were relatively small and unrepresentative of the population as a whole. They also claimed the article as representative of deficiencies in evolutionary psychology in general. Robert Kurzan at The Evolutionary Psychology Blog rebuts Myers and Coyne in defense of the field on some of those points, but I have my own concerns.
Though I admire most of Bering’s writings, this one fails to impress. In particular, what I don’t see justified in the piece is the strength of his confidence in the evidence for these anti-rape adaptations. “I don’t know about you,” he gushes, “but I’m riveted and convinced, by much of the logic in this anti-rape area,” then goes on to call them “astonishing truths.”
But these are just four papers, scattered across the past decade. If other, better papers support the anti-rape conjectures Bering makes, he doesn’t say what they are. Because of the complexity of the subject, I understand that the individual papers won’t be able to make airtight cases for the anti-rape adaptations. The flip side of that allowance, though, is that confidence about any conclusions should await a lot of robust confirmation—and these papers don’t provide it. Believing strongly in what they can tell you is like seeing four dots of paint on a canvas and being sure it will become a pointillist masterpiece by Georges Seurat.
Consider the handgrip strength paper, for example (“Effects of a sexual assault scenario on handgrip strength across the menstrual cycle,” by Sandra M. Petralia, Gordon G. Gallup Jr., Evolution and Human Behavior (Jan. 2002), 23(1):3-10). As Myers complains, “the handgrip study even admits up front that there are conflicting results, with other papers finding no differences in performance across the menstrual cycle.” Why, then, is Bering’s great confidence in this paper’s conclusion merited? I don’t know. Also, how much of an increase in strength did Petralia and Gallup measure? Neither Bering nor the paper’s abstract say, and I haven’t yet seen the full paper. Assuming that the increase is considerable, however, is it sufficient to make an ovulating woman as strong as the average man? (If someone with access to the whole paper can shed light on these answers, please do.) Moreover, Petralia and Gallup’s paper uses handgrip strength as a proxy for general combative strength, sufficient to help a woman repel a would-be rapist. I would consider that link to be at least questionable, and well short of the “extraordinary, almost preternatural abilities to prevent your own sexual assault” that Bering promises.
Bering describes conception from rape as “a catastrophic mess from the vantage point of the mother’s genes” because it undermines her own mating choices and because a rapist father may not hang around to help care for any offspring. (Bering is, of course, not in any way denying the many other types of harm that rape does, both physically and emotionally; he’s making an argument with respect to genetics and evolution.) And from our modern perspective, those disadvantages are very clear-cut. But if we look back into human evolution, our uncertainty about how our ancestors lived should surely infect those same conclusions. If our ancestors lived in small tribes of a few dozen individuals, how much would the threat of rape have coincided with the presence of strangers and how much with all-too-familiar members of the group? No one knows. How much genetic variation would females have had to choose among in making their mate choices, and how much of a violation of those choices would rape from a tribe member represent? No one knows. If humans lived in largely communal groups, how much would rapist fathers be able to escape helping to provide for their offspring? No one knows.
Unfortunately, if Bering wrote his article hoping to infect perceptive readers with his enthusiasm for evolutionary psychology, it seems more likely to highlight the big difficulties that the field faces. In the long run, I fully believe that evolutionary psychology will have significant insights to offer, but for now, I fear that science’s limited knowledge of both human evolution and psychology caps the value of what it has to say.
Update: See my followup post, which continues this discussion.