Sorry for the necro.
Just read an interesting article (only one month old) in The Telegraph. Just for the Bart's of the forum who insinuate homosexuality as a "choice". Also the research is pretty damn fascinating:
$1:
Last year Canadian scientists found that the more older male siblings a man has, the greater change he will be gay.
They believe that the immune response produced by a pregnant mother increases with each son, increasing the odds of producing more feminine traits in the developing brain of the foetus.
Each older brother raised the odds that a man was homosexual by one third.
More:
http://www.telegraph.co.uk/science/scie ... finds.htmlThey're still studying to see how much more correlated our genetics are (which it seems to be leading to suggest they're only a *contributing* factor). But for gay men the male ordering theory makes a ton of sense. Think about it. How often is the first born male gay? It happens, but I bet most gay people you know have a (or multiple) older brother(s). The pregnant woman's body reacts to a male fetus as somewhat of a "parasite" and "attacks" with different hormones that "feminize" the fetus thus increasing the likelihood of homosexuality. Each additional male pregnancy results in the woman's body launching the hormones quicker and with more intensity.
Also, its not in this article, but I remember reading that the *age* of the mother is a factor too. The older the woman is when she gets pregnant, the more likely the male fetus will be feminized in the womb.
I know it makes sense for me being gay as my mom was 38 when she had me and I have one older brother.
This leads to a few conclusions:
1) Its not a coincidence that many gay men come from religiously devout families. Religiously conservative families, on average, have more kids. Therefore, they're more likely to have multiple sons and the chance of the youngest or a younger son of being gay.
2) It is possible the % of gay men could increase in the coming decades as the Western world and feminism has resulted in woman giving birth much later in life in their late 30s and sometimes early 40s.
I just find the continued research fascinating. It also just makes so much sense from personal experiences. All but two of the gay guys I know have older brothers...the feminization of sexual attraction in the womb is probably the largest contributing factor.