A Question for Evolutionary Psychology

Men all over the world tend to find younger women sexually more attractive than older women or children. Evolutionary psychologists tell us that the reason for this is simply that it does not make any sense in terms of inclusive fitness to have sex with non-fertile females. They also tell us that what men perceive as beauty signals a woman's fitness, which increases the fitness of the offspring a man has with that woman. A third thing they tell us is that the fitness-maximizing strategy for a man is to have sex with multiple women every day - which accounts for men's greater taste for casual sex compared to women. So far, so good.

But the same reasoning leads us to the following hypothesis: Unattached men should always prefer sex with any willing reproductive-aged woman to no sex at all - at least if there's no one around to "protect her sexual integrity". (Getting your head kicked in decreases your inclusive fitness.)

Empirically, this is clearly not the case. Why not?

P.S.: Lots of fitness signaled here (SFW).


J Thomas said...

You ask why is it that unattached young men do not have sex with every available fertile woman.

As we all know, some do and some don't. And the women talk about the ones that do. High-status women all say he asked them to have sex with him and they refused, whether they actually had sex with him or not. Some low-status women will brag about having sex with him.

So by having sex with low-status women in his community, he reduces his chance of forming a long-term pairing with a high-status woman in his community.

Does it fit your experience that men who do that appear not to have a long-term pairing with a high-status woman as a priority? It fits my observations.

Men and women sometimes behave differently when they think they can do it secretly. Women are more likely to accept an invitation to travel somewhere far away where nobody knows them, than a more local assignation. Not just for the chance to see someplace exotic or the sense that more money is being spent on them. It's also less conspicuous.

John Althouse Cohen said...

You have a valid point: evolutionary psychologists tend to come up with just-so explanations for facts about the world that fit their theory. They less often focus on facts that don't fit their theory so well.

However, I'm not convinced that the fact that single men don't spend all their time having casual sex contradicts what we'd expect if ev-psych theories were true. Pregnancy and STDs are always good reasons for anyone to avoid casual sex. (I hope it doesn't need to be pointed out that pregnancy affects men even though they themselves don't get pregnant.) Men might be concerned that their reputation will suffer if they're seen dating (or hooking up with) an unattractive woman. Also, there are opportunity cost to anything: even assuming that men's ultimate goal is to have a lot of sex, a young man might recognize that staying inside on a Saturday night studying for the exam coming up on Monday will make him more likely to earn more money in the future, and thus able to attract more women.

Ev psych says that most men have an instinctive drive to have sex with lots of women. It doesn't say there are no other factors that have anything to do with whether a man actually attempts to have sex on any given day.

LemmusLemmus said...

John: You complicate matters by adding the time dimension. Sure, it might be advantageous to stay in so as to make more money later, etc. If I remember correctly, the idea behind the post (that I didn't spell out) was that even if there are no costs in terms of getting your head kicked in, reputation, time/opportunity costs, etc., most men would still prefer not to have sex with many (most?) fertile-aged women. If this is true, it is somewhat puzzling. (It would be interesting, though not particularly feasible, to do a study in which factors such as reputation are manipulated between conditions.) One could also come up with a complicated theory of why certain general aesthetic preferences are advantageous. The danger in this line of reasoning is that one tends to end up with the standby explanation that "this just goes to show that the human mind is very flexible, which itself has always had its upsides during evolution". While this may be true, one may be left to wonder why one neds the evopsych paradigm at all.

I like your reference to the factors pregnancy and STDs, however (assuming the latter have been around for a while). This leads to a model in which "some women are worth the expected cost", while others are not, which would lead us to expect the observed pattern (attractive women yes, unattractive women no). This pattern would be predicted to be more pronounced if (i) there is a negative correlation between STD presence and looks and (ii) there is a positive correlation between looks and likelihood of conceiving given sex and (iii) there is a positive correlation between the fitness of offspring and looks. To me as a nonexpert, all of those sound pretty reasonable.

So, yeah, that sounds like a pretty good answer.