I've seen both sides of the nature vs nurture debate, and have a pretty decent perspective on the points they bring across. You'd be surprised how many behaviors and personalities people develop thats environmentally induced, as evident by many dramatically different cultures out there that have yet to be exposed to western ideology. However themes of homosexuality do pop up in alot of different places. Enough to suggest that its one of the few things about a person that IS instinctual. How a person exposes those instincts publicly is where the nurture aspects plays its role.