Subsequent research related to handedness has further reinforced these findings. Share this story: CNN If you're a guy with an older brother, there's an increased chance you're gay. The meta-analysis had a total sample of homosexual males and 12, heterosexual males. The first study was a retrospective study of sex offenders, which included only those subjects whose clinical charts happened to contain birth order data so the results of the study may have been affected by selection bias. There is no effect when the number of older brothers is increased by adopted brothers or stepbrothers.
A previous version of this story referred to higher concentrations of the protein instead of higher concentrations of antibodies to the proteins when describing the findings of the study.
These results confirm that fraternal birth order correlates with sexual orientation in pedophiles, as it does in teleiophiles i. Inresearchers discovered a biological mechanism of gay people who tend to have older brothers. Information on birth weight, maternal gravidity, and other demographic variables was reported on questionnaires completed by the probands' mothers.
Using these criteria for sexual orientation identity, attraction, fantasies, and behavior, Currin et al.