Men with older brothers 'more likely' to be gay
Tuesday, 27 Jun 2006 11:22
Men with older brothers 'more likely' to be gay
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Men with older brothers are more likely to be gay, new research suggests.
Professor Anthony Bogaert of Brock University, Canada, studied 944 homosexual and heterosexual men with both biological and non-biological brothers.
According to the study, only biological older brothers predicted men's sexual orientation, leading Dr Bogaert to suggest that prenatal origins and the order of birth are determining factors in men's sexuality.
Other studies have examined whether rearing or social factors determine men's sexual orientation, but Dr Bogaert's research found that if they did then the number of biological brothers with whom they were reared would not affect sexuality.
"Yet, these brothers do predict men's sexual orientation just as the number of biological older brothers with whom they were reared," he argued.
As a result of his findings, Dr Bogaert has suggested that homosexuality in males may be due to an immune response during successive male pregnancies.
"If this immune theory were correct, then the link between the mother's immune reaction and the child's future sexual orientation would probably be some effect of maternal anti-male antibodies on the sexual differentiation of the brain," he said.
Although there is no conclusive evidence as yet to support the maternal immune response theory, Dr Bogaert said that other research exists in the theory's favour.