Are we born this way?
Publish Date: 25/07/2008
Scientists have recently discovered that the brains of lesbians and gays have structural and functional differences from those of their straight counterparts.
The Wellcome Trust Centre for neuro-imaging at University College London have found that lesbians have a "male-like" proportion and distribution of grey matter in their brain when compared with heterosexual women.
Another study done in Sweden claims that chemical pheromones, which affect our sense of smell, are different for gay men and straight men.It claims that both heterosexual women and gay men responded strongly when smelling male sweat which contained a chemical found in the male hormone testosterone while heterosexual men have little response.
The Swedish study compared the size of the brain's halves in 90 adults and suggests sexual orientation may be set in the womb.Gay men and heterosexual women had halves of a similar size, while the right side was bigger in lesbian women and heterosexual men.
A group of 90 healthy gay and heterosexual adults, men and women, were scanned by the Karolinska Institute scientists to measure the volume of both sides, and hemispheres, of their brain. When these results were collected, it was found that lesbians and heterosexual men shared a particular "asymmetry" in their hemisphere size, while heterosexual women and gay men had no difference between the size of the different halves of their brain.
A further experiment found that in one particular area of the brain, the amygdala, there were other significant differences. In heterosexual men and gay women, there were more nerve "connections" in the right side of the amygdala, compared with the left. The reverse, with more neural connections in the left amygdala, was the case in homosexual men and heterosexual women.
The Karolinska team said that these differences could not be mainly explained by "learned" effects, but needed another mechanism to set them, either before or after birth.