Biological Human female sexuality Human male sexuality Demographics Environment Hetero—homosexual continuum Kinsey scale Klein Grid Neuroscientific Queer studies Romantic orientation Sexology Timeline of sexual orientation and medicine. Is There a Role for Epigenetics? European Journal of Epidemiology. Also, the authors of the study acknowledge that a large number of sexual partners may not lead to greater reproductive success, specifically noting there is an "absence of evidence relating the number of sexual partners and actual reproductive success, either in the present or in our evolutionary past". Re-examination of the maternal immune hypothesis".
However, other studies have shown that the sexually dimorphic nucleus of the preoptic area, which include the INAH3, are of similar size in homosexual males who died of AIDS to heterosexual males, and therefore larger than female.
Homosexuals who are twins. A study of 46 probands.
Daryl Bema social psychologist at Cornell Universityhas theorized that the influence of biological factors on sexual orientation may be mediated by experiences in childhood. Hamilton and Mary Jane West-Eberhard. In Dean Hamer and colleagues published findings from a linkage analysis of a sample of 76 gay brothers and their families. Some advocates for the rights of sexual minorities resist linking that cause with the concept that sexuality is biologically determined or fixed at birth. The fathers, a US citizen and an Israeli citizen, are both listed on the birth certificates of the twins and legally are the exclusive parents of the boys, who shared a surrogate.