Men who have an older brother are more likely to become gay and the cause of the problem is established before birth.
This is the finding of a team of researchers led by Anthony Bogaert, a professor in the department of psychology and public health sciences at Brock University, Canada, and published in the journal PNAS, a publication. Science published weekly by the US National Academy of Sciences.
There are many different factors that need to be taken into account in determining someone’s sexual orientation. But in this case, the researchers noticed the existence of an aspect involving a protein that binds to the Y chromosome (a chromosome that females do not have) in the mother’s uterus.
The researchers suggest that this Y-linked protein may have entered the mother’s bloodstream during pregnancy with her first child. At that time, the mother’s body will immediately detect that protein and the immune system creates antibodies to defend itself. After a while, this antibody had accumulated in a certain amount, and the woman became pregnant with another baby. Most likely at this time, the antibody crosses the placenta into the baby’s brain. And this may be the reason why brain functions are changed, thereby redirecting the development of feelings of attraction in male fetuses.
In the past, there have been studies with similar results, a man has a higher probability of becoming gay and being attracted to other men if he has many brothers. In 2006, a study showed that the odds of a man being gay would increase by about a third if he had an older brother, but then scientists were unable to explain the phenomenon.
Professor Bogaert and his colleagues conducted a 20-year trial involving a small group of 142 women and 12 men between the ages of 18 and 80. The concentration of an antibody to a protein called NLGN4Y in their blood samples showed that NLGN4Y levels were higher in women with multiple gay sons and brothers than in women who had no sons or had a son but a tendency to have a son. common sexual orientation.
Before publishing the results, they did a lot of research to find out what led to that phenomenon. Accordingly, a man has the ability to become gay even if he did not grow up next to his brother and this does not happen if the family has an adopted brother. Therefore, the researchers thought of a biological mechanism related to the mother.
However, the study failed to show why some men become asexual or bisexual.