Then how has it not been bred out. Same reason why sickle cell anemia and cystic fibrosis hasn't been bred out probably. Sickle cell doesn't prevent you from breeding, and is actually beneficial in some environments, as it prevents I believe malaria. Cystic fibrosis I don't know enough about to answer though. But gay people in theory don't have kids. So how do the gay genes get passed on? In order for someone to have sickle cell anemia, they would need both genes. It could go the same way in terms of sexuality. Cystic fibrosis patients typically die around 20 although medical advancements have prolonged this... Thing is, it's a very difficult concept to understand. I know for certain it is not a choice, but something causes it to happen. Thing is it could be with DNA (pretty much the same but the subtle differences change the amount of certain proteins from bring produced - could inhibit production of certain hormones or proteins for certain areas if the brain to develop) or sociology (if someone was raised in a troubled childhood, and their only companions were close friends, who knows?) Overall, it is easy to say it is a choice and move on, but if it really isn't then there is nothing that can be done to change it. Sure they can get married, or have kids, but would they really be happy? Being forced to be anything you're really not or don't want isn't really fair.