Study finds link between the amount of older brothers you have and your sexuality
By 9Honey|
Nature versus nurture ?is a long-standing debate between biologists, psychologists and sociologists, and published theories can often have extreme real-world consequences.
As Sydney ?comes off a monumental month hosting WorldPride จC a celebration filled with historic moments but also, for some, marred by homophobic attacks จC the LGBTQ community has been at the forefront of conversation worldwide.
One such topic is increasing anti-transgender rhetoric in the United States and Australia, calls to ban conversion therapy, and now, a resurgence in the "fraternal birth order effect" dialogue, thanks to 2GB's Ben Fordham.
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It's a disputed theory that's existed since the 1950s, ?which suggests an immune response during pregnancy จC that occurs in reaction to the proteins a male foetus produces จC produces antibodies that remain in the bloodstream, and those antibodies potentially play a part in the sexual development of children produced from future pregnancies.
Evidence has historically relied on small samples, until in January 2022, a study conducted by ?Australian scientists จC Francisco Perales, Christine Ablaza, and Jan Kabatek จC was published in the Journal of Sex Research.
That study was based on data from over nine million people registered in the Netherlands, with the researchers following the "life trajectories" of those born between 1940 and 1990.
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As such, the study concluded there is compelling evidence of a "fraternal birth order effect on homosexuality", which, simply put, means the more older brothers a person has, the more likely they are to enter into a same-sex relationship.
While the data did not record the sexuality of people registered, it did show if people had entered into a same-sex marriage or civil partnership, which was the basis researchers used "as a proxy for homosexuality."
According to the study, ?men with one older brother were 12 per cent more likely to enter into a same-sex relationship than men with an older sister, and 21 per cent more likely to enter into a same-sex relationship than men with a younger sibling.
Men with three older brothers, according to the study, were 80 per cent more likely to enter a same-sex partnership than those with three younger brothers, and 41 per cent more likely to do so than those with multiple older sisters.
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The study also documented the same pattern of results among women, noting they too were more likely to enter a same-sex relationship if they ?had older brothers.
Why researchers believe these findings are vital?
Nature versus nurture's impact on the "cause" of sexuality is something many in the LGBTQ community have questioned the necessity of knowing.
Yet according to the researchers, who wrote an article for The Conversation when the study was published, it's a topic that was important to investigate on a large scale as it has "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 biological factors (such as hormones or genetics) are more likely to support sexual minorities and their civil rights, compared to those who view it as a product of social factors or individual choice," they wrote.
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Kabatek spoke with Fordham on his weekend Ben Fordham Live! podcast and clarified the antibodies are "not so much of a determination" but "an influence" จC and due to the study's large sample size, he doubts the link is a coincidence.
"There is biological and chemical evidence, which is showing that this link is actually manifesting and it's not something else," Kabatek told Fordham.
"But I mean, you know, science is never conclusive. So we should always have a little bit of doubt," he continued. "Human sexuality is a great puzzle and this is just one piece of it."
Correlation, however, does not equal causation จC but Kabatek says not to discount the importance, for some, of knowing the probability.
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"Of course, in an ideal society, the rights and respect people are afforded should not depend on whether their sexual identity is 'innate' or 'a choice'. But unfortunately, these issues still loom large in contemporary debate, further highlighting the importance of our findings," the researchers wrote in The Conversation.
Knowing sexuality has a biological basis, they highlight, completely eliminates the theoretical premise of harmful practices like conversion therapy, which NSW Premier Dominic Perrottet conceded he will ?support a state ban of days after Opposition Leader Chris Minns vowed to as well.
The researchers also argued their findings discredit claims homosexuality can be "taught" จC a school of thought Florida's 'Don't Say Gay' bill used to justify eliminating teachings of diversity from schools in the state จC or that homosexuality can be "passed on" socially, which is a common argument against allowing same-sex couples to adopt children.
"We consider this research essential," the researchers wrote. "Understanding the mechanisms behind sexual orientation can offer insights into what makes people who they are, and helps normalise the full spectrum of human sexual diversity."
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