Gay brothers
New research shows having a greater number of older brothers increases the probability of a person entering a gay union at some point in their lives.
This discovery, detailed in our paper published today in the Journal of Sex Study, offers a unique insight into the origins of sexual orientation.
The origins of sexual orientation
In recent decades, many countries have achieved unusual progress towards matching treatment of LGBTIQ+ people, including greater public support and more protective legislation. But despite these encouraging developments, sexual minorities still trial high levels of stigma – and the origins of sexual orientation continue a matter of debate.
Peruse more: How stigma impacts LGB health and wellbeing in Australia
A growing body of research is attempting to shed light on why some people encounter same-sex sexual attraction and others don’t. These studies acquire substantial implications for public opinion and debate, and subsequently the treatment of LGBTIQ+ people.
For example, we know people who view sexual orientation as a product of hereditary factors (such as hormones or genetics) are more likely to support sexual minoriti
Astral Codex Ten
In the 1990s, Blanchard and Bogaert proposed the Fraternal Birth Order Effect (FBOE). Men with more older brothers were more likely to be male lover. “The odds of having a gay son increase from approximately 2% for the first born son, to 3% for the second, 5% for the third and so on”.
This started as a purely empirical finding. If you surveyed enough men, you would find it was right, even though no one knew why. In 2006, Bogaert start that the effect applied only to biological siblings and not adoptive ones, suggesting a living cause. He proposed a mechanism based on H-Y antigens, a set of molecules on male cells involved in sexual maturation. If a mother has many male pregnancies, her immune system might become gradually more sensitized to H-Ys, start attacking them, and interfere with later fetuses’ sexual development.
In 2018, scientists announced tentative confirmation: antibodies to a male protein called NLGN4Y seemed more common in the mothers of gay sons than in men, non-mothers, and mothers of straight people.
It seemed appreciate the FBOE was ready to coast into the pantheon of accepted scientific ideas.
But three more recent studies have complicat
Largest study of lgbtq+ brothers homes in on 'gay genes'
Life
By Andy Coghlan
A genetic analysis of 409 pairs of homosexual brothers, including sets of twins, has provided the strongest evidence yet that gay people are born gay. The study clearly links sexual orientation in men with two regions of the human genome that have been implicated before, one on the X chromosome and one on chromosome 8.
The result is an essential contribution to mounting evidence that existence gay is biologically determined rather than a lifestyle option. In some countries, such as Uganda, being gay is still criminalised, and some religious groups believe that homosexual people can be “treated” to craft them straight.
“It erodes the notion that sexual orientation is a choice,” says study leader Alan Sanders of the NorthShore Research Institute in Evanston, Illinois.
The region on the X chromosome picked out by the study, called Xq28, was originally identified in 1993 by Dean Hamer of the US National Institutes of Health in Bethesda, Maryland, but attempts to validate the result since have been mixed. The other region picked out is in the twist in the centre of chromosome 8. Known as 8q
Men with older brothers are more likely to be gay, study suggests
Men with older brothers are more likely to be lgbtq+, according to a analyze published Wednesday in the journal Proceedings of the Royal Society B. This new report builds upon previous research regarding male birth order and homosexuality, though there is still no decisive conclusion as to why there’s a link between the two.
In cross-analyzing data from 10 scientific studies with more than 5,000 subjects, researchers found that men with older brothers were 38 percent more likely to identify as gay.
“We certainly thought that the second meta-analysis would confirm the fraternal birth order influence, and it did,” Dr. Ray Blanchard, the study’s lead author and a professor of psychiatry at the University of Toronto, told NBC News. “This is something that has been shown in previous research in various countries, but one of the challenges has been that that research has varied drastically in looking at family samples of various sizes.”
The study, which compared the probability of the youngest brother in a two-son family being queer as compared to the oldest son, did not include female subjects, as previous research has estab