Is Sexual Orientation In Our Genes?

Genetic analysis of 409 pairs of gay brothers, including sets of twins, has provided the strongest evidence that gay men are born that way. The study clearly links male sexual orientation to two regions of the human genome - one on the X chromosome and one on chromosome 8.

"This discovery shatters the notion that sexual orientation is a choice," said study leader Alan Sanders of the NorthShore Research Institute in Evanston, Illinois. The region on the X chromosome, called Xq28, was originally identified in 1993 by Dean Hamer of the US National Institutes of Health. Another important region of interest is at the center of chromosome 8. It is known as 8q12 and was first identified in 2005.

Over the past five years, Sanders has collected blood and saliva samples from 409 pairs of gay brothers, including non-identical twins, from 384 families. The team examined the locations of the genetic markers.

The only trait that can be clearly seen in 818 men is their homosexuality. All other traits, such as hair color, height, and intelligence, varied to varying degrees. It was possible to identify five frequently occurring changes from the Xq28 and 8q12 regions on the X chromosome and chromosome 8, respectively. Sanders says he compared these rates between gay and heterosexual men to see if there are clear differences.

“This study is driving yet another nail into the coffin of the theory of homosexuality as a lifestyle of choice,” says Simon LeVay, a neuroscientist and author, who stated back in 1991 that a specific brain region within the hypothalamus is smaller in people with homosexual tendencies.