Having more older brothers increases the chance that a person will get married to someone who is the same sex at some point in their lives according to a new study.
These maternal antibodies build up over many pregnancies with male foetuses, which means that men with more older brothers are more likely to be attracted to women of the same sex. However, previous research on the fraternal birth order effect has used small and selective groups of people, which has led some scholars to question the validity of the phenomenon.
In a new study, unique data from Dutch population registers was used.
People’s sexual orientation wasn’t measured in the data, but they did say if they had ever been in a same-sex marriage or had a registered partnership. The data found that men are more likely to be in a same-sex relationship with someone who has an older brother or sister. The birth order and number of siblings also play a role.
As the number of brothers and sisters grows, the differences get bigger. People who have three older brothers are 41% more likely to get married to a same-sex partner than people who have three older sisters.
The sex of younger siblings, on the other hand, doesn’t play a big role at all. If a woman has older brothers, she is also more likely to be in a same-sex relationship with someone else. This gives some support to the idea that maternal antibodies and foetal proteins also work together to affect women’s sexual development.
All of this: What does it mean?
This evidence is in line with views that see sexual orientation in an innate trait and a reflection of a person’s true self, not a result of “lifestyle choices” or “fashion trends,” as some people say. This means that this evidence is in line with these views. The rights and respect people should have should not be based on whether their sexual identity is “innate,” or whether it is “a choice.” In an ideal society, this should not be the case.
