Man's Sex Orientation Mysteries

The possible effect that the more older brothers a boy has, the more likely he is to be gay may be more biological than social factors, a Canadian study revealed.

Professor Anthony Bogaert from Brock University in Ontario, Canada, studied 944 heterosexual and homosexual men with either "biological" brothers, in this case those who share the same mother, or "non-biological" brothers, that is, adopted, step or half siblings.

He found the link between the number of older brothers and homosexuality only existed when the siblings shared the same mother.

The amount of time the individual spent being raised with older brothers did not affect their sexual orientation.

I do share the similar sentiment with Andy Forrest, a spokesman for gay rights group Stonewall.

Increasingly, credible evidence appears to indicate that being gay is genetically determined rather than being a so-called lifestyle choice.

Tags: gay lesbian homosexuality heterosexuality boys sex orientation study siblings biological factor social factors brothers