The Allen Almanac

Joel Hernandez has pointed me towards an interesting article on livescience.com. It says:

When times are tough, women tend naturally to abort a higher percentage of male fetuses. Researchers call it culling, but they don’t know why it occurs.

This much is known: During times of social or economic stress, a woman’s liver tends produces more of a hormone called cortisol that proves so damaging to male fetuses they actually kick out in response to it.

Female fetuses, more vital on the whole, seem relatively unaffected by the cortisol.
…
Those born during bad economic times and other periods of high stress—male or female—actually had longer life spans, “suggesting the weaker among them were removed” in the fetal stage, Catalano explained in a telephone interview.

And since more of the males would naturally have been week, slamming them with the hormone would be a biologically beneficial way of quickly preparing the mother for another pregnancy instead of possibly wasting time on a birth that would not produce an ideally healthy child.

I’d never heard about this before.