Friday, June 14, 2013

Men Caused The Menopause. Today's Funny Research.

I love these weirdo studies, I do!  Now we are told, based on computer simulations and nothing else, that human females have the menopause because "at some point" in our evolutionary history men decided to mate with younger women.  So there was no point in keeping that energy-intensive fertility machine going for older women and the ones who had the menopause mutation (that part is my guesswork) took over.  Here's how one of the researchers explains all this to us:

"This paper is saying that men have played the major or dominant part in choosing mates," said biologist Rama Singh, who is a professor of population genetics and evolution at McMaster University in Canada. "Somewhere along the line in our evolutionary history, males did not mate randomly but preferred young women because they are more attractive."
I like that very scientific-sounding statement in that last sentence.  It's a bit circular, preferring young women because they are more attractive, which is the same as preferring younger women because one prefers them.*

As the study summary states, there are many theories about why menopause exists.  None of them seem to be based on anything but theoretical speculations, however.

But this one elicits a few interesting questions:  We are told that men are the more selective sex.  That goes straight against the usual evolutionary-psychology argument that women are the more selective sex.  It also goes against the usual evolutionary-psychology argument that men can mate with thousands of women, no trouble.

So why would men not mate with older women, too?

Another problem with the study is that the researchers seem to assume nothing bad happens to sperm quality as men age.  Research suggests that this is not correct.  The number of mutations in the sperm grows with age, the motility of the sperm decreases as well.  Ignoring all that may not matter for the arguments in this piece, but it shows a lack of knowledge of the relevant area.

Finally, chimpanzees appear to prefer older females for mating purposes.  Given that we are so often told to look at our closest relatives for guidance about our biology and behavior, that difference might be worth pondering about.

I'm not excluding this theory among the many menopause theories.  But the fact is that we really have no evidence about the origins of the menopause and I wish researchers expressed the usual careful academic skepticism when talking about the meaning of their own research.  That tends to disappear in these kinds of studies, at least when it comes to statements made to the public.
*There's a deeper kind of circularity in these arguments, because usually the male preference for younger females is explained as a consequence of the greater fertile period those females have ahead of them.  That's a reference to menopause, not just to getting older.