Study finds epigenetics, not genetics, underlies homosexuality

[S]ex-specific epi-marks, which normally do not pass between generations and are thus “erased,” can lead to homosexuality when they escape erasure and are transmitted from father to daughter or mother to son. […]

The study solves the evolutionary riddle of homosexuality, finding that “sexually antagonistic” epi-marks, which normally protect parents from natural variation in sex hormone levels during fetal development, sometimes carryover across generations and cause homosexuality in opposite-sex offspring.