But the logic of mblase's writeup presumes that there is no benefit in being homosexual, either for the individual or the species. While the biological advantage of heterosexual intercourse is that you can produce children, perhaps the advantage of sex with someone your own gender is that you can't. The 'tribe' needs maiden aunts to care for the children, and population growth can only go so far. Maybe the contribution made by the childless is so great that a population can't live without it.

So, back to the heterosexuals. Who knows what causes it? Certainly on an individual level, for women heterosexual intercourse and resulting childbirth has been the greatest threat to their survival. One for one, there's no advantage in reproduction for women.

It's going to wrench your mind into 23 pieces whichever way you look at it. Perhaps the reason we don't usually debate the reasons for people being heterosexual is simply that they're the majority. And most people are normal, right?