Sexual selection may not favor promiscuity among males after all.

Occasionally I find myself in a debate about human sexuality and I have noticed a couple of common tropes that come up over and over again.

Of course many will know the common ones that come from various groups of theists arguing for abstinence until marriage.  Of course just because fundamentalists give us biologically incorrect statements like “if you have sex with someone you are having sex with everyone they have ever had sex with” it doesn’t mean there aren’t some significantly stupid things said by people making completely non religious arguments.

On of my favorite arguments has to do with a suggestion I hear repeated quite often.  The notion that men have evolved to be more promiscuous than women.  This is usually offered as part of the mansplaning done to excuse men who cheat on their significant others.  They seem to think by arguing that this claim is based on science it can’t be argued with.  Which is oddly enough the exact opposite of what good science is supposed to be about.  Still I see a lot of people make statements along this line, even ones I think probably mean well, like Dan Savage.  I’ve also had arguments with lots of assholes who have used this type of argument to explain to me why they were awesome alpha males who got all the chicks, and if I were just more of a jerk I could get women too.

Let me be clear here before I continue, I am not criticizing people who practice polyamory, because in those cases people are being honest with one another.  However I do criticize people who got involved in a relationship under the pretense that it would be monogamous and then at some point decides that was stupid and then go out and fuck other people but fail to discuss this with their significant other.  This carries with it both emotional and medical risks and it’s not cool.

Now, for my part I have always had my doubts about this particular line of thinking for several reasons.  For one, the people who say this most often are not actually biologists, or often not scientists at all.  For two, the studies that have indicated this have all been done on much more simple life forms, usually fruit flies, because observing selection pressure requires multiple generations and so studying sexual selection in humans difficult.  Further, trying to generalize the selection pressures of a species like the fruit fly to the ones humans face is more than difficult, there are so many variables between the two that it seems absurd.

That was why I was excited when I read this article recently:

Biologists Reveal Potential ‘Fatal Flaw’ in Iconic Sexual Selection Study

So to summarize the story, the 1948 study involving fruit flies was redone with more modern methods and the findings were debunked. See, they had no way to gene type back in 1948 so he had to pick flies with genetic abnormalities that caused obvious taxonomic differences in the animals.  This meant he could only count the offspring that ended up with both traits which would theoretically end up being one fourth of the total.  However these mutations hurt survival and thus prevented proper counting which skewed the numbers in the original study.

Also, yes, I was excited by a study about the sexual behavior of fruit flies….don’t judge me. 

I suggest reading the whole article, but the end result was that the new study could not find any evidence that there was an evolutionary benefit to male fruit flies having multiple partners.  
Of course the creationists over at discovery institute choose to display their ignorance of anything even remotely related to science by crowing about how this study destroyed a “pillar of Darwinism.” You can read the article here:  Bateman’s Sexual Selection: Another Darwinian Pillar Falls.

This study does not disprove sexual selection overall, but only brings in to doubt one aspect of it.  Still it is a good lesson, when someone comes along and starts arguing they have a right to be a jerk because science says so they are most likely mistaken about both the science and the ethics.

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