Men with older brothers more likely to become gay

A new research is extending an earlier study which claimed that men with older brothers are more likely to be gay by looking into the possible biological basis of homosexuality.

The earlier research conducted by sexologist Anthony Bogaert, a Community Health Sciences chair and professor at Ontario's Brock University published in New Scientist magazine in 2006 led him to conclude that each older brother raises the odds of homosexuality by a third, the Huffington Post reported.

Brock University explains that Bogaert had studied 944 gay and straight men, including some who were raised with non-biological male siblings, to pit prenatal against postnatal factors, and ultimately determined that for each male gestation that occurs, something changes in a woman's body that makes her more likely to give birth to a gay son.

Bogaert has revealed that he is looking to determine the prenatal origin of this phenomenon and has been collecting samples of mothers of gay men and comparing them to mothers of heterosexual men and looking to see if there is evidence of a biological factor that differs between the two groups.

He suggested this mechanism could be a maternal immune response, a hormone change in the womb, a gestational factor during pregnancy or even genes, but there are no results yet.

If successful, his new research could provide a biological backing for homosexuality.