I thought this fit the topic nicely.
http://www.thetech.org/genetics/ask.php?id=155
[quote]One reason why conversion might be so difficult is that the brains of gays may be different from their straight counterparts. For example, a couple of studies have been done that show that the brains of gay people are different than those of straight people. And that gay people respond to pheromones differently than straight people.
This isn’t surprising, sexual attraction resides in the brain. But where do these changes come from? Are they destined by genes, is it something in the environment or a combination of the two?
The best evidence points to the environment and genes both playing a role.[/quote]
He then talks a bit about twin studies, very interesting stuff.
[quote] A number of studies have looked at homosexuality in twins, all with similar results. For example, in one study, if one identical twin was gay, the other was also gay 50% of the time. If they were fraternal twins, they were both gay 22% of the time. And if one was adopted, the chances fell to 11%.
…
This strongly suggests that there is a genetic component - there is something in their genes that makes them more likely to be gay. Genetics, though, isn’t everything.
If it were, then identical twins would both be gay 100% of the time. And this clearly isn’t the case.
And if it were all environment, then identical twins would both be gay as often as fraternal twins. Again, this isn’t the situation.
So the interplay of environment and genes probably results in homosexuality. By environment, I don’t just mean how someone is raised (although that is sometimes part of it). I mean the effect the environment can have on how the brain is hardwired very early on.[/quote]
Now I know someone’s going to say that twins are identical, so it must be a choice, but identical twins may come from the same egg/sperm combo, however from womb development on, their environments can be different. Apparently, even in the womb, one can receive more nutrients than the other.
It’s interesting. Height is also something that is both genetic and environmental. I work with a girl who is an identical twin and she’s actually a few inches shorter than her twin sister. They grew up in the same house, same schools, etc. Could have been anything in the environment that she was exposed to and her sister was not, virus, bacteria, radiation, worse nutrition, etc…
Identical twins genes not identical:
Why Identical twins are different:
My grandmother and her identical twin look a lot different now at 83 than they did as teens. One married, had kids and quit smoking early in life (30s) while the other never married, smoked into her late 60’s, early 70s, and now has emphysema. She’s also the one I mentioned earlier who we’re pretty sure is a homosexual.