thetatiana: (Default)
thetatiana ([personal profile] thetatiana) wrote2012-04-02 04:30 am

Sexual Selection

Every explanation I've read of this in biology books is circular and wrong.

Biologists have not realized that female sexual taste is a trait that's heritable and selectable as much as any other. So it is shaped by natural selection, too. What are the implications of this?

Females will tend to choose males who enhance their offspring's chances of living and breeding successfully.

So far so good? Excellent. So why, then, do pea hens, for instance, tend to choose those males with the garish though gorgeous, but totally unweildy tails? Does this mean their children will be fitter? Not the sons, really. They'll inherit those gargantuan unwieldy tails. But the daughters? You betcha! They get the fitness of a father who is so fit he can even carry around this extra baggage, this conspicuous consumption, this beautiful but ungainly appendage that has a metabolic cost, attracts predators, is too heavy and too long to make perching safe in the lower branches, etc.

So what does this tell us? That among species with male sexual selection traits, it must be more advantageous to secure high fitness for your daughters, even at the cost of lower fitness of your sons.

Don't tell me the sons have high fitness because of sexual selection; that's circular reasoning. Sexual selection has to persist in the face of the fact that female preferences are heritable. If your mom likes the big sexy dumb type of guy, it's more likely you will as well. If she goes for the swift but less flashy, intelligent type, that also has more chance of carrying over to you. And in the end, if she chooses guys who decrease her chances of having successful offspring, she'll get weeded out in the evolutionary lottery.

So this tells us some fascinating things. At least some of the time, for some of the species, daughters are much more important than sons in the fitness equation.

Moms among the Irish Elk, Pea Hens, Big Horn Sheep, Moose, Deer, and, well, actually quite a few mammal species, you should value your daughters more! Maybe even human moms should, too.