Scientists say older brothers make men more likely to be gay

Scientists say older brothers make men more likely to be gay

Did your big brother make you gay?

Men who have older male siblings are more likely to be gay, researchers at Brock University in Ontario have found, and it has nothing to do with being treated like the baby in the family.

Instead, researchers believe the immune response a woman mounts against having a male baby in her womb increases with each son, raising the odds of “feminizing” the fetus’s developing brain.  In one study, Canadian scientists collected information from nearly 1,000 men, including some who had been adopted or raised with stepbrothers and stepsisters.

Having brothers increased a man’s odds of being gay – but only if they were blood brothers. Stepbrothers did not have an effect, the study found. However, biological brothers who were brought up separately did. This suggests that the link can be explained by nature rather than nurture, according to New Scientist. Each older brother raised the odds that a man was homosexual by a third.

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