Sibling order may affect sexuality and identity

The podcast explores the fraternal birth order effect, the observed phenomenon where gay men are more likely to have older brothers. It examines the statistical evidence, noting that each older brother increases the likelihood of male same-sex attraction by approximately 33%, though this is not the only influence on a person's sexuality. Scott Simonina explains the maternal immune hypothesis, a leading theory suggesting the mother's immune system develops antibodies to male-specific proteins during gestation, affecting subsequent male fetuses. Jan Kabatek discusses research that surprisingly found the same effect in women in same-sex marriages, questioning the maternal immune hypothesis. Writer Justin Torres shares his personal experience as a gay man with older brothers, reflecting on both the intriguing and potentially dangerous aspects of such research, particularly regarding prenatal testing.