[Sykes]

If homosexuality is purely genetic, it is still possible for it to have survived humann history since in the beginning, sexuality was open, so there was no way to tell who was purely gay or not. In the middle ages, when sexuality was closeted, you had people who were gay but forced into heterosexuality and "bred" their homosexuality into future generations. The way things are now, if everyone can be truly open on who they are, and if you're correct on homosexuality being 100% genetics, then yes, the number of homosexuals on Earth would go down.