upepo
Elder Lister
Because biology or nature is good at correcting errors when they happen. If you are gay, it makes sure you don't marry and sire offspring, makes sure your cave mates avoid you and keep their children away from you, and, finally, it gradually nudges you toward self-destruction so that it doesn't have to waste resources on a member who is not contributing to the propagation of the species. That way, the faulty genes are extinguished before they have any effects on the community.