An interesting theory my sister presented.

I think social environment has definitely something to do with it. In ancient greece there were a lot more gay men, appearantly. Back then women were for reproduction, you had your fun with men.

But it isn't really society alone that teaches people to like the other gender, it is also natural instinct of survival of the species.

Scientists have also seen in researches the youngest person in a family is more likely to be gay. In prehistorian times the older kids reproduced themselves, and the younger kids needed to help out their brother or sister with the babies upbringing, they analysed.

That makes me wonder, would people who are infertile be more likely to tend toward the same sex?