I think I saw a post on the earlier part about it not being genetic- I havent yet read through the entire thread yet (at work too long XD) but pardon if someone has already pointed this out:
I do believe it is a genetic thing over all. I remember seeing a science article and special on TV about genetics and the new system for "baby charactaristics" that you can choose.
Hell of expensive, you can choose your babies eye color, hair color etc by altering their genes. You can choose their chances of what sexuality they will be with it as well.
Its been a while since Ive seen this article but I do believe thats what was said.
Either way, choices can be made influenced by genetic inheritance-- can it not?