Saturday, December 18, 2010

Sex and Evolutionary Psychology

For many years I didn't like this idea--i.e. that men and women were/are different. 

My sense of fairness and a bunch of feminist scholarship forced me to conclude that sexual behavior was purely learned.  I am not trying to take away from learned oppressive behavior with this post, so don't get me wrong.

What I'm saying, though, is that my previous assumptions were a bit naive.  Let's consider simple demand and supply around sexual reproduction, the primary driver of life.

Let's say that when men ejaculate, on average, there are 3 million sperm in their ejaculate. Let's say that men are "viable" from age 15 to age 55.  Let's also say that men can easily ejaculate once a day.  Wow, wait, I'm totally underestimating the amount of sperm out there.  Wiki says it can be up to 300 million sperm per.  Let's say an average of 100 million, to be safe.  And one orgasm/ejaculation per day, every day, for 40 years.  That's 365*40 = 14,600, and then 14,600 * 100,000,000 =

1,460,000,000,000 sperm.

Now, that's a LOT OF SPERM.  About a trillion and a half sperm for one male for one life.

Now, let's say the average female produces eggs from age 15 to 55 (a huge stretch), once a month.  That's 40*12 = 480.  

480 eggs.

Okay, so who's competing for whom here?  Women have a tremendous incentive to pick wisely.  They want men who can provide for their off spring, who will stay close (i.e. loyal), who will be dedicated, in short.  

Men, on the other hand, can go spraying all over town and then some, and never have to be that selective unless there's some disadvantage.  Is there?  Yes.  Eventually, they won't be that attractive to women--i.e. they won't be able to convince women that they can be dedicated, and therefore, have available mates.

That's not saying that all women think of all of their sex partners as life long partners, not wholly.  But it is a widely different calculus than men make most of the time.


Anonymous said...

The story is a bit more complicated than this. It's true that, like you say, women have an incentive to pick wisely, and that they want men who can provide for their offspring. But another (and sometimes conflicting) preference is towards the quality of her offspring's genome. If a woman is coupled with a loyal, providing male, her fitness can still benefit from seeking new partners with (expected) genome quality higher than that of her partner, regardless of whether those new partners are loyal and dedicated or not.

In other words, evolution equips men with an incentive to cheat, and women with an incentive to cuckold.

Think about it. Because female reproductive capacities are the limiting factor, women choose their sexual partners, whereas men compete to be chosen. Therefore, if women did not have an incentive to cuckold their partners, male promiscuity would convey such a strong evolutionary disadvantage that it would be a much less common behavior than it actually is.

hmm said...

Yeah, that's a great point. I'll have to think about it more and post again on this topic soon.