I was also asked how homosexuality is helpful to the survival of our species. Honestly, I have no clue. I do know that homosexuality and bisexuality are evident in other species besides ours but as for the purpose... that's an excellent question. For me though, I'm of the "who cares?" variety. It is an excellent idea to be well versed in possible theories in case a question like this comes up in conversations. Not to mention proving that sexuality is a genetic trait might be helpful but could also lend to credence to those who believe homosexuality is a disease. I just wish that society would just stop hating everyone and start loving everyone like all these religions preach about. It's like that scene in Half Baked, "fuck you, fuck you, fuck you, you're cool, fuck you" Sin is such an ugly word that make people act like barbarians that there are a number of deaths resulting from religious fervor. You must die because you are different. How terrible a person you must be if you can justify taking someone's life and hating someone due to their sexual orientation. It wasn't too long ago that we felt the same way about people of different races, and now there's a similar feeling towards those with a different sexual orientation as us. Since it's not entirely evident certain prejudice application can't take place like segregated bathrooms and transportation systems, but not being able to marry or being fired just because the person you love is the same gender as you is segregation too.
The point is that sexuality is not a disease, is not a complete choice and that people need to get off their high horse and start acting like decent people. Maybe when we learn to be loving and supportive of others will our eyes open to all the good things that this world has to offer.