Study after study has shown differences in the actual brain activity of gay v. hetero people. This of course was trumpeted by gay activists as evidence that it was genetic rather than a choice or environmental.
There is some theory that the hormonal conditions in the womb can be part of what causes a proclivity towards this. It is what is theorized to be the reason that the third son of a couple has a far higher chance of being gay than the first son of the same couple. To understand this phenomena, scientists have begun to study brain activity that forms during gestation or just after, using brain scans. They did this to rule out the factor of learning.
Here is one of those studies:
http://www.newscientist.com/article...tructured-like-those-of-the-opposite-sex.html
(If you scroll down on the original screen after clicking the link you can choose skip and it will take you to the story without having to register.)
This, of course, leads some scientists to study the hormonal factors. Especially when they found that genetics is almost not a factor at all in female homosexuality. (That part is in the full publication of that study and seems not to be present in that article.)
If you use that theory and extend it here, it is possible that one twin got more than his fair share of testosterone in the womb.
This, of course, leads many homosexuals to deny the studies' implications as it may cause many people to seek hormonal therapy in the womb to "ensure" that their child will not have this particular hurdle to overcome.
Well. That's one explanation for it, at the least.
A second explanation is that genetics create a proclivity towards not a guarantee of homosexuality, this is particularly evident in males where it is shown that genetics may play a role but is not the sole significant factor.
