The increasing chance of being gay based on amount of sons a mother has
The idea that prenatal mechanisms may influence sexual orientation has been around for a couple of decades. In , Bogaert along with colleague Ray Blanchard correlated sexual orientation in men with the number of older brothers, but it wasn't clear if that influence was occurring because the boys shared the same household or because they had shared the same womb. In the new study, Bogaert pitted prenatal against postnatal by examining four samples of homosexual and heterosexual men, for a total of participants. The data for three of the samples had been collected previously, and included detailed information about the men's sexual orientation, as well as their family life.
We may know why younger brothers are more likely to be gay
We may know why younger brothers are more likely to be gay | New Scientist
Having older brothers increases the chance of a man being gay because of biological changes that happen when a woman becomes pregnant with a boy, according to a new study. Canadian and American researchers sought to understand a previously established link that homosexual men tend to have a greater number of older brothers than heterosexual men. In the study, published Monday in the journal PNAS, researchers found that mothers who have boys had higher instances of an antibody against a protein essential in the developing male brain. The presence of the antibody — anti-NLGN4Y — is believed to play a role in determining sexual orientation while the fetus is developing. The study consisted of subjects that included men, women with no sons, mothers of heterosexual son, mothers of gay sons with no older brothers and mothers of gay sons with older brothers. The researchers said that while results are promising, the findings need to be replicated in larger studies and only accounts for a small and specific portion of gay men. Click here for reprint permission.
How much do the chances of having a gay son increase per child?
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A new study from the journal PNAS sheds new light on the "fraternal birth order effect" — a previously observed trend that gay men, on average, have a greater number of older brothers than straight men. The research looked into an "immunlogoical explanation" to explain this trend. It found that some mothers, while pregnant, created antibodies in their bloodstream in response to a protein linked to the Y chromosome of an unborn son.