A number of researchers have sought to find a biological cause for same-sexual attraction. The media have promoted the idea that a “gay gene” has already been discovered (Burr 1996[3]), but in spite of several attempts, none of the much publicized studies (Hamer 1993[4]; LeVay 1991[5]) has been scientifically replicated. (Gadd 1998) A number of authors have carefully reviewed these studies and found that not only do the studies not prove a genetic basis for same-sex attraction; the reports do not even contain such claims. (Byne 1963[6]; Crewdson 1995[7]; Goldberg1992; Horgan 1995[8]; McGuire 1995[9]; Porter 1996; Rice 1999[10])

If same-sex attraction were genetically determined, then one would expect identical twins to be identical in their sexual attractions. There are, however, numerous reports of identical twins who are not identical in their sexual attractions. (Bailey 1991[11]; Eckert 1986; Friedman 1976; Green 1974; Heston 1968; McConaghy 1980; Rainer 1960; Zuger 1976) Case histories frequently reveal environmental factors which account for the development of different sexual attraction patterns in genetically identical children, supporting the theory that same-sex attraction is a product of the interplay of a variety of environmental factors. (Parker 1964[12])

There are, however, ongoing attempts to convince the public that same-sex attraction is genetically based. (Marmor 1975[13]) Such attempts may be politically motivated because people are more likely to respond positively to demands for changes in laws and religious teaching when they believe sexual attraction to be genetically determined and unchangeable. (Ernulf 1989[14]; Piskur 1992[15]) Others have sought to prove a genetic basis for same-sex attraction so that they could appeal to the courts for rights based on the “immutability”. (Green 1988[16])