Scientists may have discovered why boys with older brothers are more likely to be gay

Scientists may have discovered why boys with older brothers are more likely to be gay

Scientists may have discovered why the more older brothers a boy has, the likelier he is to be gay as an adult.

Known as the “fraternal birth order effect”, numerous studies have found a correlation between the birth order of boys and male sexual orientation.

Now researchers say increasing levels of antibodies in a mother’s immune system could play a role.

Antibodies are proteins produced by the immune system to fight harmful bacteria and viruses. But pregnant women sometimes produce antibodies against fetal molecules, such as when their foetus has a different blood group.

Anthony Bogaert, a professor in social psychology at Brock University, Canada, believes that some women who are pregnant with boys produce antibodies that neutralise a protein made by the Y chromosome; the DNA molecule that determines sex in humans.

Bogaert and his team speculated that these maternal antibodies might play a role in determining the sexual orientation in their sons.

The team took blood from 142 women and the samples were screened for antibodies to a brain protein only found in males, since only boys have the particular protein-producing Y chromosome.

The protein, known as NLGN4Y, plays a role in how neurons communicate with each other and is made at the surface of brain cells, so easier for antibodies to locate.

The researchers found that the mothers of gay sons with older brothers had the highest levels of this antibody, followed by the mothers of gay sons with no older brothers. Mothers with straight sons had even less, and mothers with no sons had the least.

The team speculates these neuron-attacking antibodies build up in women’s bodies every time they are pregnant with a son. The higher the concentration, the likelier the boy is to be gay, the researchers suggest.

“It could affect brain structures that moderate attraction,” Bogaert told the New Scientist. “The mother’s immune response may alter the typical function of these brain structures.”

He added: “I wouldn’t say we’ve solved the fraternal birth order effect puzzle, but we are getting close to finding a mechanism.”

However, at 142 women, the research involved only a small sample size, so no strong conclusions can yet be drawn over the reasons for the fraternal birth effect.

The phenomenon is also only estimated to impact 15 per cent of gay men.

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5 Comments

  1. trystham
    December 17, 06:35 Reply

    Lol. So you’re saying heterosexuality in males is some sorta disease women have to develop antibodies against??? That’s rich.

  2. Delle
    December 17, 13:01 Reply

    Scientists, I can see, are gradually losing it. Boredom has obviously crept into their laboratories and now they are carrying out nonsense experiments.

    Well we are still yet to discover if there’s a gene responsible for homophobia. That should keep you guys busy and productive ???

  3. dale
    December 17, 13:50 Reply

    lol.coming from a polygamous home with 4 elder bros and two kid bros,nah I will disagree with this.doesn’t hold water.God made me like this.end of discussion!

  4. Manach
    December 17, 23:30 Reply

    All I keep seeing in the article is ‘speculate’,’speculate’.Nothing definitive.

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