The inactivation of the X chromosome occurs randomly throughout the embryo, resulting in cells that are mosaic with respect to which chromosome is active. To find the epigenomic markers of male homosexuality, Ngun, a postdoctoral researcher at UCLA's Geffen School of Medicine, combed through the genetic material of 47 sets of identical male twins. In interviews to the press, researchers have pointed that the evidence of genetic influences should not be equated with genetic determinism. Diversity, Gender, and Sexuality in Nature and People. But the existence of twin pairs in which one is homosexual and the other is not offers strong evidence that something other than DNA alone influences sexual orientation. Twins With Different Sexual Orientations:
They conjure up the specter of the surgical or chemical "rewiring" of gay people, or of abortions of fetal homosexuals who have been hunted down in the womb.
Homosexual orientation in twins: a report on 61 pairs and three triplet sets.
No conclusive evidence supports any one specific cause of homosexuality; however, most researchers agree that biological and social factors influence the development of sexual orientation. Whether genetic or other physiological determinants form the basis of sexual orientation is a highly politicized issue. This clearly contradicts the hypothesis that homosexual males have a female hypothalamus. Daryl Bema social psychologist at Cornell Universityhas theorized that the influence of biological factors on sexual orientation may be mediated by experiences in childhood. The inactivation of the X chromosome occurs randomly throughout the embryo, resulting in cells that are mosaic with respect to which chromosome is active.