Based on identical twin studies, being gay seems to be about 50% genetic. Gay genes get passed on from generation to generation. But the persistence of these genes poses something of a problem for obvious reasons. One would expect these genes to be selected against, since (it would seem) they make reproduction less likely.
What follows is my rendition of one evolutionary theory that attempts to explain how gay genes could have a selective advantage in a population. This rendition is a bit humorous, of course, but it may not be too far off from the gist of the theory.
There are a bunch of genes that make it more likely that your brain will develop in a more feminine direction. If you have any one of these genes, or just some of them, you will not be likely to be gay. If you have enough of them, you are considerably more likely to be gay, though the chances still aren’t 100 percent. Let’s step through the possible cases.
Case 1: You have no gay genes at all. Your brain has developed in a completely masculine direction. You are a completely hairy gorilla, and you pee in the sink. Women say ‘Ew, yuck,’ and avoid you at all costs.
Case 2: You have just a few gay genes. Your brain has developed in a slightly more feminine direction. You are slightly less hairy, and you usually remove the dishes before you pee in the sink. Women still say ‘Ew, yuck,’ but they also say, ‘Well, given that I am stuck on a desert island with you and you are the only male available, I guess I will hold my nose and have a kid with you.’
Case 3: You have more gay genes. Your brain has developed in still yet more of a feminine direction, with the result that you are reliable, and stick around to support your children. You pay attention to your partner. You never pee in the sink. Women go up to you and say, “Please, I want to have your baby.”
The gay genes get passed down through the generations because of this selective advantage.
Case 4: You have still more gay genes, and your brain has developed in even more of a feminine direction. You go up to guys and say, “Please, I want to have your baby.”