Biological Causes of Male Homosexuality

Research indicates a connection between birth order and male homosexuality, with evidence suggesting that having older brothers increases the likelihood of a younger brother being gay. Studies conducted over the last few decades have shown consistent findings that this phenomenon may also extend to older sisters, challenging previous assumptions that only older brothers played a role. This suggests that biological factors and uterine environments are influential, but the exact mechanisms remain partially understood, as pure genetic influences alone cannot account for these patterns. Environmental factors, potentially including maternal immune responses to previous pregnancies, are posited as significant contributors to the development of sexual orientation.