According to an article in the star this morning, a paper prepared for the National Academy of Sciences concludes that having an older brother increases the odds of a younger brother being gay, due to the influence on a woman's womb of a male child. Following a sample of 905 children, the paper concludes that each male birth increases the odds of a subequent male birth being gay by 33%. (Biologists believe that how women come to be lesbian is a different process.)
(This has an intriguing evolutionary component, I think. In prehistory did families in which there were fewer male branches and descendents contending for limited resources have a survival advantage? In essense, is the womb producing a measure of population control, preventing family battles for limited resources?)
So how about a very unscientific poll here on bilerico: To gay men reading this site, in comments below, which can be anonymous, please note: Do you have an older brother? How many? (If you know a gay man and can answer these questions about him, please do so!) By the way, at what age did you know yourself to be gay? and in retrospect, whether you knew it or not, were there early signs?
I I have an older brother (who is not gay) . My significant other, Tom, has two older brothers (who are not gay). I didn't know I was gay (or what being gay even was) until college. In retrospect, however, my youth had plenty of signs had I understood them.