Greg Laden pointed me to this paper the other day. He's got a write up of it on his blog from an anthropological point of view, and Wired and the Mary Sue both covered the story (though amusingly the Mary Sue reported that only 1 in 10 women COULD orgasm, when in fact it's the other way round or I imagine there'd be a lot less to talk about), but of course, it's orgasms. FEMALE orgasms, and this means that I have to give it my own special Scicurious treatment (the one from the...orgasmic...point of view??). Especially since I feel that the abstract and findings of this paper glossed over what I think is definitely the most important finding: sure, the female orgasm isn't an evolutionary byproduct, but it looks like there may be a genetic component.
Zietsch and Santtila. 'Genetic analysis of orgasmic function in twins and siblings does not support the by-product theory of female orgasm' Animal Behavior, 2011.
Also, their main point. Well. Yes, these findings do not SUPPORT the by-product theory of female orgasm...but they don't actually refute it either. Oops.
(You know what I'm talkin' about...)
People LOVE to debate female orgasm. We love to debate what it is (what really "counts" as orgasm, clitoral? Vaginal? Is there no difference?), we love to fight over how often it happens (Do you ejaculate or not?), and most importantly we wonder WHY. WHY female orgasm? Why does it happen? What purpose does it serve? For the 10% of women who have never had one, what are they missing? And why has it become some sort of sociological obsession for men in their 20s to make their partners achieve it more than 5 times per session?
In fact, people are so amazingly into the female orgasm that scientist have put forward over 20 theories as to why it occurs. Most of these fall into three categories: pair bonding (orgasms feel good, so it must make us like our mates more), mate selection (the best dudes evolutionarily speaking must bring the best skills to the sack, apparently. I'd love see that tested), and enhanced fertility (where orgasm produces "insuck" and makes it easier for the sperm to find the egg). All of these have their supporters, their detractors, their problems, etc. And then there's the FOURTH category: where female orgasm don't matter. Honey badger don't care.
That's right, there is a hypothesis that female orgasm serves no evolutionary purpose whatsoever. Instead, it's merely a by-product of male orgasm, where female bodies can orgasm...only because male bodies can.
Of course, this hypothesis is not very popular, but is it TRUE? The authors of this study wanted to test this, and figured that, if female orgasm really WERE a by-product of male orgasm, then genetically speaking, it would vary along with male orgasm. This means that people who are related will have similar...orgasmic abilities.
This is where you start asking many sets of twins some very personal questions. The authors gave a bunch of questionnaires to sets of Finnish siblings, fraternal twins, and non-fraternal twins. They asked the women how often they reached orgasm during sex, and how difficult it was, and asked the men how fast they ejaculated and whether they felt they came too early. From these they determined a score of "orgasmic function", and they thne looked for correlations among groups.
They found that the fraternal twins and the siblings had tiny, but significant correlations in orgasm function, but the fraternal twins were not different from normal siblings (as you might expect, given that they are related to the same degree). However, the male and female identical twin pairs had much higher rates of correlation.
From this the authors determined that female orgasm is not an evolutionary by-product.
Now, does this study PROVE that female orgasm is not an evolutionary by-product? Nope, not exactly. It proves that female orgasm does not co-vary or correlate with male orgasm in genetically close relatives. So, you know, your orgasms aren't correlated with your brother's. That probably made a whole bunch of you relax a little. But it doesn't completely prove that female orgasm is not an evolutionary by-product, either. In order to REALLY prove that, we would have to prove that female orgasm has NO FUNCTION. And this study did nothing to address that question at all. So, no disproof.
BUT. It did show something interesting, though it was something so glossed over by the authors that none of the mainstream coverage picked it up (though Greg certainly did). The biggest and best correlations here are those between the female identical twins and the male identical twins. This is not overwhelmingly surprising for the males, but I don't think it's been shown in females before. And it suggests that there's a genetic (and thus possibly a PHYSICAL) basis for the female orgasm. We do have some physical indicators for female orgasm (eletrodes will go all crazy when you orgasm and the electrodes are up in your business), but the correlation of genetics to the 'orgasm function' is a nice little finding.
But I gotta say these self-report studies, man, they get me DOWN. There are just too many issues at hand here.
1) Define orgasm. What kind? What do you MEAN?
2) Define sexual stimulation and whether it was self- or not. What if some of these women suffer from particularly bad partners?
3) SOCIOLOGICAL FACTORS. When women talk about having a tough time having an orgasm, or talk about having loads of them, it's not like we're talking about them like we'd talking about having our knee itch. Sex is very taboo in a lot of societies, certainly it's extremely thrilling, and so the sociological pressures going on just can't be underestimated.
4) You're telling me that 39% of men ejaculated 10 minutes after penetrative intercourse has begun?! Someone's lying, and I think it's those dudes. Most other studies with more rigorous testing say the average is 5 minutes or less.
And you know, this is all so...self-reported. I think if you're really going to look at physical, genetic, what have you, bases for female orgasm, you gotta get IN there. You have to make sure those electrode readings are going nutso. You need a controlled setting without the influences of individual variation in partners. What you need here are related and non-related female volunteers, a large selection of vibrators, and some MEGs. And that still wouldn't really PROVE whether it's evolutionarily beneficial or not. But it would show more accurate readings. To me that's a good enough place to start.
Zietsch, B., & Santtila, P. (2011). Genetic analysis of orgasmic function in twins and siblings does not support the by-product theory of female orgasm Animal Behaviour DOI: 10.1016/j.anbehav.2011.08.002