The very definition of sexual orientation emphasizes on attraction. According to Hill and Dawood (2012), because attraction captures the essence of sexual orientation (i.e., having a particular direction), and is perhaps less likely than behaviour or identity to be influenced by cultural and societal norms, many early researchers focus on the biological basis of sexual orientation. This idea is strongly linked to essentialism- believing that some phenomena are innate, central to one’s identity, universal, and most importantly, biologically determined. I will specifically focus on how genetic approach, hormones and brain neuroanatomical research, and evolutionary psychology explain homosexuality. A series studies on genetic field have shown the influence of genes. Pillard et al (1981) found that a huge number of homosexual men and women have gay or lesbian siblings comparing to heterosexual subjects, and the rate is especially prevalent in monozygotic twins than any other types of siblings. Similarly, Bailey and Pillard (1991) provided further evidence. They used the classical behavioural genetics methods: they recruited homosexual male monozygotic (MZ) twins, male dizygotic (DZ) twins and adopted brothers. They then recorded rates of homosexual relatives among these subjects and found that relatives with homosexual orientations are significantly higher in MZ twins (52% concordance rate) than DZ twins (22% concordance rate) and adopted brothers (only 11% concordance rate). All these results suggest that the concordance of homosexual orientation is highly correlated with the relatedness of siblings, indicating genetic effect. Another notable evidence is from a study done by Dean Hamer. He investigated 40 families of homosexual men. The DNA linkage analysis revealed that markers on Xq28 on the X chromosome were correlated with homosexual orientation (Hamer et al, 1993). According to this finding, he proposed the concept of “gay gene”. Although some continuing researches on this proposal didn’t successfully replicate it, we cannot ignore the underlying possible genetic explanations. Thus, it is feasible to conclude that the development of homosexuality has at least partial genetic component. The application of evolutionary theory on different sexual orientations provides further insight.
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People question why homosexuality persists even if it does not offer reproductive values, which is a critical feature in natural selection. Evolutionary theorists explain this by the idea of “inclusive fitness”: the reproductive success of oneself and one’s close relatives (DeLamater&Hyde, 1998). Homosexual men and women contribute to their siblings’ and other close relatives’ successful reproduction by providing necessary support and resources as a way of passing some of their genes down, including same-sex sexual orientation. Consequently, the “gay gene” is maintained and passed down from kin selection. Evolutionary biology strongly suggests that some people have predisposed gay genes from past generations. Many researches in hormones demonstrate effects in resulting homosexuality. Brannon (2011) summarizes from past researches that prenatal testosterone exposure can have great impact, that is, “too much or too little exposure to androgens produces brain variations that underlie the …show more content…
LeVay (1991) believed that origin of homosexuality rooted deeply in brain structure. He studied the neuroanatomical differences of the anterior hypothalamus among heterosexual men, women and homosexual men. Volume of INAH3 is larger in heterosexual men than in heterosexual women and gay men. Furthermore, it is also similar between homosexual men and heterosexual women. Although his hypothesis is criticized by many later researchers on inconclusive samples, it sheds more lights on biological implications of
People question why homosexuality persists even if it does not offer reproductive values, which is a critical feature in natural selection. Evolutionary theorists explain this by the idea of “inclusive fitness”: the reproductive success of oneself and one’s close relatives (DeLamater&Hyde, 1998). Homosexual men and women contribute to their siblings’ and other close relatives’ successful reproduction by providing necessary support and resources as a way of passing some of their genes down, including same-sex sexual orientation. Consequently, the “gay gene” is maintained and passed down from kin selection. Evolutionary biology strongly suggests that some people have predisposed gay genes from past generations. Many researches in hormones demonstrate effects in resulting homosexuality. Brannon (2011) summarizes from past researches that prenatal testosterone exposure can have great impact, that is, “too much or too little exposure to androgens produces brain variations that underlie the …show more content…
LeVay (1991) believed that origin of homosexuality rooted deeply in brain structure. He studied the neuroanatomical differences of the anterior hypothalamus among heterosexual men, women and homosexual men. Volume of INAH3 is larger in heterosexual men than in heterosexual women and gay men. Furthermore, it is also similar between homosexual men and heterosexual women. Although his hypothesis is criticized by many later researchers on inconclusive samples, it sheds more lights on biological implications of