Vaniver comments on How to deal with someone in a LessWrong meeting being creepy - Less Wrong

16 Post author: Douglas_Reay 09 September 2012 04:41AM

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Comment author: [deleted] 08 September 2012 03:05:29AM -1 points [-]

In other words, maybe it's not that individuals are creepy so much as men "naturally" act more rapey if there are only a few women around.

This is unlikely. The idea that male-on-female rape, in humans, is reflective of forced mating as a reproductive strategy makes some big mistakes because it doesn't factor in how human reproduction actually works.

It's true in a general way that if the cost of your gametes is low, and you can get out of the parental investment, then increasing the number of coital acts is an effective way to buy genetic fitness at reduced cost (part of why mammals tend to be much more promiscuous, in a very broad sense, than birds: birds get their embryo out of Mom and into the world early and let it develop there, which means Daddy has a higher incentive to invest parentally -- though this is only a very broad pattern).

Trigger warning for those who'd rather not hear it described in frank, mechanical terms!

But with humans in specific, rape is not a great reproductive strategy. The odds of insemination are lower, because things like self-lubrication and uterine peristalsis (which make a big difference) aren't typically going to occur. Even post-coital cuddling increases the odds of fertilization. Getting into comparative primatology, humans have conspicuously large penises compared to our relatives who do tend to use force as a basic approach to getting sex (gorillas, who have a harem-style arrangement as their basic stable social model).

Rape has been prevalent throughout human history, but forced copulation doesn't seem to be a leading or even closely-tailing human reproductive strategy. It's probably not an adaptation (though if you insist that pretty much every salient feature of behavior is, or is the proximal outcome of some evolutionary adaptation, you can spin a theoretical picture to justify it easily).

Comment author: Vaniver 09 September 2012 10:17:02PM 7 points [-]

Trigger warning: more mechanical discussion of nonconsensual sex.

The odds of insemination are lower

On a per-act basis, rapes are about twice as likely to result in pregnancy than consensual sex. I suspect that you're right that various fertility-boosting measures don't happen during rape and this effect is due primarily to selection effects (who rapes, who is raped, and when the rape happens), but the net result is still that rapes are a decent reproductive strategy (if the rapist can get away with it).

Rape has been prevalent throughout human history, but forced copulation doesn't seem to be a leading or even closely-tailing human reproductive strategy.

This seems really unlikely in the context of marriages before the Enlightenment, or in the context of wars and raids (where women were a resource like any other).

Comment author: J_Taylor 10 September 2012 02:52:32AM 3 points [-]

On a per-act basis, rapes are about twice as likely to result in pregnancy than consensual sex.

Yes, in America. We also frequently do our best, when having consensual sex, to minimize our odds of having kids. (I was unable to find rates of birth control use during rapes, unfortunately.) In the ancestral environment, this would probably not be a factor.

Comment author: Vaniver 10 September 2012 03:08:54AM 5 points [-]

Yes, in America. We also frequently do our best, when having consensual sex, to minimize our odds of having kids. (I was unable to find rates of birth control use during rapes, unfortunately.) In the ancestral environment, this would probably not be a factor.

I'm pretty sure the 3% number comes mostly from women trying to get pregnant, and it's estimated that the per-act incidence of rape pregnancy would be about 8% instead of about 6% if none of the victims were using birth control.

Comment author: J_Taylor 10 September 2012 04:19:38AM 2 points [-]

Tentatively updated. Will investigate further later. 3.1 number comes from an odd data-set.

http://www.niehs.nih.gov/research/atniehs/labs/epi/studies/eps/question/index.cfm

Comment deleted 10 September 2012 04:03:26AM [-]
Comment author: Vaniver 10 September 2012 04:24:47AM 4 points [-]

It looks to me like your link is a 1995 study, and my link described a 2000 or 2001 study, which I'm having trouble finding. I think it might be this one but I'm not seeing the 3.1% value anywhere. The study I linked has slightly lowered my credence in the 3.1% number, but I can't tell if the numbers it's reporting are per-act numbers or not. (I'm not an expert in this field and have been trusting summaries from science journalists; I'm not sure if I'm interpreting the actual papers correctly or not.) It looks like this study might have said "at their least fertile, there's less than a 5% per-act chance of copulation, which is lower than we thought it was" and that got interpreted as "in general, there's less than a 5% per-act chance of copulation."

I hope Gottschall and company know what they're doing, and expect the 3.1% number comes from another study. It might be profitable to email one of the professors in question and ask for where that number came from, because it's being slippery.

Comment author: J_Taylor 10 September 2012 04:28:17AM *  2 points [-]

Sorry, for deleting my post. I linked to the wrong study (as you pointed out) and wanted no replies until I revised my post.

Also, this is the 2001 study:

http://www.ncbi.nlm.nih.gov/pubmed/11376648

Edit: I would like to criticize Todd Akin for making my truth-seeking less convenient by really messing up the signal-to-noise ratio regarding this matter.

Comment author: [deleted] 10 September 2012 02:19:58AM 2 points [-]

but the net result is still that rapes are a decent reproductive strategy (if the rapist can get away with it).

They touch on the statistics further down -- it's believed to be due to the fact that, in the case of consensual sex, the woman is more likely to have control over when in their fertility cycle the act occurs.

This seems really unlikely in the context of marriages before the Enlightenment, or in the context of wars and raids (where women were a resource like any other).

Different cultures have had very different approaches to marriage throughout history; they still often do. Anyway, I'm talking about the claim that rape is an evolutionary adaptation from the ancestral environment, couched as a reproductive strategy -- Neolithic Eurasia is a bit too recent to be germane to my argument.