The exception is homosexual men’s brains, which show remarkable similarities to the brains of heterosexual women, suggesting that sexual orientation depends on the effect hormones have on the developing brain.īut these two factors only go so far in explaining how homosexuality develops. During pre-natal development, for example, the sex organs in a foetus can recognise testosterone, which will switch on genes to make it male.Īside from a few superficial differences (among them penis and ring-finger length – both longer in homosexuals), gay and straight men’s bodies appear the same. Hormones are chemical messengers, released by certain cells to affect the growth and development of other cells in the body. Many scientists believe that exposure to hormones during pregnancy heavily influences sexuality. A subsequent study in 1999 failed to replicate Hamer’s results and other researchers are sceptical that Xq28 is linked to homosexuality at all. “Many people who are gay don’t have any history of homosexuality in their families.” He points out that some heterosexual men in his 1993 study also had the so-called gay gene. “Our studies showed that it significantly increased the odds of being gay, but it was not determinative,” says Hamer. Inheriting the gay version of Xq28 won’t necessarily make you homosexual. In this case, Hamer compared the X chromosomes from 40 pairs of gay brothers, and Xq28 stood out. So, if you study many pairs of gay brothers and find a DNA region that’s the same in more than 50 per cent of cases, it’s likely to be linked to homosexuality. When comparing bits of DNA from two brothers, the sequences will, on average, be the same 50 per cent of the time. Linkage mapping works because close relatives like brothers share not only a particular trait, such as homosexuality, but also the genes underlying the trait. To track down the DNA region linked to the gay trait, Hamer used a technique called ‘linkage mapping’, an approach that lets geneticists find a gene even when they don’t know what it does or where it’s located. This is because males inherit their X chromosome from their mother. “For geneticists that’s fascinating because it suggests it could be due to X chromosome linkage – those types of traits tend to run on the female side for males,” says Hamer. Now chief of the gene structure and regulation section at the US National Cancer Institute, his study revealed a curious pattern: gay men tended to have more gay uncles and gay male cousins on their mother’s side of the family than on their father’s. It was scrutinising family trees to see how homosexuality is inherited that led Hamer to the discovery of Xq28. The fact that identical twins have the same DNA and fraternal twins share 50 per cent suggests that male homosexuality is hereditary. For instance, identical twin brothers (siblings derived from the same fertilised egg) are more likely to both be gay than fraternal twins (twins that develop from separate eggs). While there hasn’t been much research on lesbians, there has been on gay men. “They continue to be vehemently opposed to any notion that homosexuality is something natural,” says Hamer.ĭespite their objections, there’s a lot of evidence that homosexuality has a biological basis. Conservative attitudes remain unchanged, however.
![does taking a gay test prove you are gay does taking a gay test prove you are gay](https://media-cldnry.s-nbcnews.com/image/upload/t_nbcnews-fp-1200-630,f_auto,q_auto:best/newscms/2018_08/2336846/180221-erik-adam-2-ew-613p.jpg)
“On the other hand, gay people hated it too because, at that time, there were fears that the discovery would be misused to abort gay babies and wipe gay people off the face of the Earth.”Īlthough these fears remain, in recent years the search for ‘gay genes’ has become more accepted by the gay community, in no small part because a biological explanation would undermine arguments that being gay is a social or lifestyle choice.
![does taking a gay test prove you are gay does taking a gay test prove you are gay](https://i.ytimg.com/vi/AnjmUrVktIY/hqdefault.jpg)
“Conservative, right-wing people hated it because they felt that it was saying that being gay is like being black, that it was in-born, that it would somehow ‘excuse’ gay people or give them more rights,” says Hamer. The discovery caused Hamer to be attacked from all sides. The region also goes by another name: GAY-1, a genetic marker linked to male homosexuality.
![does taking a gay test prove you are gay does taking a gay test prove you are gay](https://cdn.cnn.com/cnnnext/dam/assets/220307160832-kate-mckinnon-snl-full-169.jpg)
The search for ‘gay genes’ goes back to 1993, when a US team led by Dr Dean Hamer described a region of DNA located on the X chromosome called Xq28.