That’s not very civil of me, but it is honest. Having said that, behavior is obviously based in biology, and it does stand to reason that some behaviors will have been influenced by natural selection. Admittedly, I’m biased against evolutionary psychology: I think, in general, the claims made are far too strong and the confounding variables inadequately controlled (in my really snarky moments, I think evol psych is a justification for middle-aged faculty to sleep with their younger graduate students). A recent Slate article which asks “Have women evolved to protect themselves from sexual assault?” The article provides four arguments that women have evolved anti-rape defenses that are heightened during ovulation:
1) When threatened by sexual assault, ovulating women display a measurable increase in physical strength.
2) Ovulating women overestimate strange males’ probability of being rapists.
3) Ovulating women play it safe by avoiding situations that place them at increased risk of being raped.
4) Women become more racist when they’re ovulating.
Regarding claim #1, PZ Myers points out that the increase in physical strength has not been substantiated. In spite of that, I’ll accept claims 2 and 4 as accurate (I’ll deal with claim #3 in a bit). What claims #2 and #4 do is conflate choosiness with rapist avoidance. If women are evaluating men on a scale from ‘Eek! Creepy rapist’ to ‘I’ll do him right here on the table’, we would expect more selectivity during ovulation (i.e., a bias towards the ‘Eek!’ end of the scale). Rape avoidance postulates that selectivity exists as a specific separate behavior from choosing males in general. I wouldn’t be surprised if, on average, women are more choosy when ovulating: pregnancy imposes significant costs in terms of vulnerability while pregnant and death during pregnancy (in the absence of modern ob/gyn care, birth has a pretty good chance of killing the woman). But that’s not specifically rape avoidance, but part of a larger, more inclusive behavior of mate choice (of course, this supposes that women actively choose men, as opposed to being passive sperm receptacles). Likewise, regarding claim #4 (racism), there is some literature that suggests women, on average, prefer men whose appearance isn’t too different from what they grew up around. Again, if ovulation makes women more choosy, then what is being called ‘racism’ is actually honing in a familiar image. It’s not racism per se; it’s simply setting the bar higher. Women will be less likely to deviate from the ‘normal’ appearance when the stakes are higher.
Claim #3 is really problematic. The article claims:
German investigators Arndt Bröder and Natalia Hohmann established, ovulating women are not less active in general–they’re still busy shopping, going to church, visiting friends, and so on–but they avoid doing those things that make them sexually vulnerable. (link is to a pdf)
I’m not sure they’ve established much of anything. Risky versus non-risky activities were scored by 23 women on a scale of 1-5 (5 being the most risky), and the average score was used. I would have used the median score instead: a few ‘nervous Nellies’ could easily raise a score. This sounds technical, but it could make a huge difference in scoring. I’ll also note that college students were used to assess risk, and college students are fantastic risk assessors (Got Four Loko?) But what really bothers me is this figure:
The largest change in behavior is among women not on the pill (the pill simulates some of the effects of pregnancy, most notably preventing ovulation): they increase non-risky activities, far more than they decrease risky activities (which is still statistically significant). Ovulating women seem to be more active overall. Maybe ovulation makes women want to do more stuff, and that causes a decrease in risky activity–there are only so many hours in a day. Finally, by the authors’ own admission, this is a relatively weak effect (related to this, keep in mind the scoring caveat noted above). One study that demonstrates a weak effect needs a lot more follow up (didn’t the sciencebloggysphere just have a humongous conniption fit over the Decline Effect?).
As PZ concisely put it:
There are days when I simply cannot bear the entire field of evolutionary psychology: it’s so deeply tainted with bad research and a lack of rigor. And that makes me uncomfortable, because the fundamental premise, that our behaviors are a product of our history, is self-evidently true. It’s just that researchers in this field couple an acceptance of that premise to a deep assumption of adaptive teleology, the very thing that they should be evaluating, and produce some of the most awesomely trivial drivel.
This evidence simply doesn’t meet the standard.
Related posts: Emily Yoffe, Echidne, Jerry Coyne, and Amanda Marcotte (here too) also comment. Also see John Rennie and Amanda Schaffer.
An aside: Why does no one include lesbians in these studies, many of whom have no intention of getting pregnant to have offspring? Seems that would be very elucidating….