Gay men may be born and not made, a Canadian study published in the U.S. journal Proceedings of the National Academy of Sciences Tuesday has concluded, adding that having several elder brothers increases the likelihood of a man being gay.
Although the link has long been established, the study of 944 men in Canada indicates that the link appears to have nothing to do with whether a man is brought up with his elder brothers, and is therefore psychologically influenced by them.
Instead, the increased chance of being homosexual seems to be the result of whether or not the mother has already given birth to boys - in other words, a biological link from the womb rather than psychological links from childhood.
"It's likely to be a prenatal effect," said Anthony F. Bogaert of Brock University in St. Catharines. "This and other studies suggest that there is probably a biological basis for homosexuality."
But it remains a mystery why for every elder brother a boy has, his chances of growing up gay increase by about a third.
Bogaert looked at gay men who had not been raised with their elder brothers, but still found that there was a link between homosexuality and the number of elder male siblings they had.
One explanation, Bogaert suggests, could be a maternal immune response to succeeding male fetuses. Mothers may produce antibodies against a male foetus's Y chromosome while in the womb, and these antibodies have an accumulative effect on subsequent pregnancies, which could affect the sexual orientation of boys.
Marc Breedlove, of Michigan State University, a colleague of Bogaert, wrote a commentary in the journal: "[Sigmund] Freud thought a distant, emotionally cold father might prevent a boy from identifying with dad and steer him to homosexuality. How much stranger it will be if, instead of the father's psychological rejection, it is the mother's immunological rejection that inadvertently but actively makes her son gay?"
The research was funded by the Social Sciences and Humanities Research Council of Canada. Enditem
Well, I happened to come across this article this morning , being the youngest of 3 brothers (and two sisters) I still have not noticed the "urge" but there you go..