Thus far, what are the known biological markers that indicate homosexuality? Are there any that have been repeated and established? For example, studies that refer to brain differences observed with MRI, etc. And with that question in mind, would it theoretically be possible, using these findings, to provide a service to people questioning their own sexuality as a sort of guidance to discovering themselves on a fuller level? Excluding the potential for misuse, I've wondered whether such a thing would prove beneficial to LGBT people if it had existed.
There is a piece of DNA the allow the masclination of the brain to happen and there are chemical on off switch's but they have not found the part YET or what triggers the change.
I read somewhere that, during fMRI scans, being shown pictures of members of one's own sex, the opposite sex or both will light up the area of the brain for sexual attraction, depending on one's sexual orientation. That's just proof that being gay isn't a choice, it's a biological difference, but again, it didn't have any particular guesses as to why in the study I read about.
Known? As in verified and scientifically accepted as fact? Not really, not that I've read. There have been a lot of studies (on gay men, for the most part) that find some correlations between certain factors and homosexuality, but correlation is not causation. And the things they found didn't apply to their whole population. There's been some research as to a genetic basis for homosexuality (again, mostly in men), but funding is hard to come by for those, so there haven't been a whole lot of them in the first place, let alone repeat studies. There are a handful of studies on homosexual women, bisexual people, and transgender people, too, but they run into the same (or more, in the case of studies of women) problems. They'll find something that has a fairly high correlation in one population (like, say, the whole 'index finger shorter than your ring finger' thing) and get completely different results in another population. From what I gather, most of the studies that have been done do point to a biological rather than environmental cause. They're just not sure what that cause is. Personally, I think the attitude should be, "It's okay to be gay because it just is," and not, "It's okay to be gay because you can't help it, poor dears." But, eh.
I think I heard something about the direction your hair grows in (in guys) but I would regard that as pseudoscience until it shows up in a peer reviewed journal.
I believe the current idea is that homosexuality is linked to genetics somehow, but that it isn't entirely genetic. The most convincing theory I've heard is that there is a gene that when expressed in women makes them more fertile but when expressed in men makes them more likely to be gay. (Or maybe that the fertility gene makes the woman also more likely to have gay sons...) Regardless there isn't any conclusive evidence about anything, except that males with more biological older-brothers are more likely to be gay.
