In 1862, Charles Darwin wrote that “we do not even in the least know the final cause of sexuality. The whole subject is hidden in darkness.” Since then, however, many studies have offered insight into this complex issue. Although many think that homosexuals are simply confused about their sexual identity, recent scientific findings have given more support to those who believe gays are genetically predetermined to be homosexuals. Armed with an understanding of these findings, one must concur that homosexuality is not a choice but rather a genetically predetermined trait. The evidence is overwhelming: there is a genetic -- not psychological -- link to homosexual behavior.

            Psychologically, homosexuals are no different than heterosexuals. In 1957 with a grant from the National Institute of Mental Health, Evelyn Hooker embarked on the first study to determine the relationship between homosexuality and psychopathology. She studied two groups, one comprised of thirty homosexuals and the other of thirty heterosexuals, and matched them for age, IQ, and education. None of the members of either group had ever undergone any psychiatric treatment. After having both groups complete three major psychological evaluations -- the Rorschach, Thematic Apperception (TAT), and Make-A-Picture-Story (MAPS) tests -- Hooker had experts in the three testing fields try to identify from the subjects’ results which subjects were homosexual. None of the experts was able to positively identify a subject as being either homosexual or heterosexual (UCD 6; Burr, Atlantic). As Edwin Shneidman, the psychologist asked to examine the results of the MAPS tests, noted, “I wish I could say that I see it all now, that this is the profile of a person with a homosexual orientation, but I can't see it at all” (qtd. in Burr, Atlantic). As a result of Hooker’s study and others that corroborated her findings, the American Psychiatric Association removed homosexuality from its Diagnostic and Statistical Manual of Psychiatric Disorders in 1973; two years later, the American Psychological Association followed suit and declared that homosexuality was not a mental disorder. In fact, in July 1994, the American Psychological Association issued a statement concluding that “homosexuality is neither mental illness nor moral depravity. It is simply the way a minority of our population expresses human love and sexuality.”

            Since homosexuality could not be traced to psychological causes, researchers wondered if there is a biological basis for sexual orientation. In 1994 at the University of Western Ontario, J. A. Y. Hall and D. Kimura studied the fingerprint ridges of self-proclaimed and Kinsey scale-ranked¹ heterosexuals and homosexuals. After the sixteenth week of pregnancy, fingerprints are known to be unchangeable, so if there were any significant fingerprint differences in the two groups, one could argue that sexual orientation may be determined before birth. In fact, Hall and Kimura did find that the difference between the number of ridges on the left hands of homosexual men was greater than that of heterosexuals (1204). Citing that individuals with higher left-hand ridge counts perform differently on sexually dimorphic² cognitive tasks than do those with higher right-hand ridge counts (1203), the researchers concluded that there must be an “early biological contribution to adult sexual orientation” (1205).

            Around the same time, researchers also wondered if there are any structural differences in the brains of homosexuals and heterosexuals. In 1990, in one of the first studies to determine if the brain is dimorphic with respect to sexual orientation,  D. F. Swaab found that in homosexual males, the suprachiasmatic nucleus (SCN) of the hypothalamus, in general, was twice as large as the SCN in heterosexual males (Burr, Separate 26). Although the hypothalamus indirectly governs a person’s sexual drive, the SCN is known not to have any part in regulating it. Perhaps, though, the hypothalamus was the key. Under this premise, Laura S. Allen probed further into the hypothalamus and reported that the anterior commissure (AC) in the hypothalamus was the largest in homosexuals (LeVay 123). Yet the AC does not control sexual drive either. Nevertheless, Swaab’s and Allen’s findings are quite significant, for “the very fact that the anterior commissure [and, in turn, the SCN] is not involved in the regulation of sexual behavior makes it highly unlikely that the size differences result from differences in sexual behavior. Much more probably, the size differences came about during the original sexual differentiation” of each structure (LeVay 123).

        In a separate experiment, Allen found that of the four interstitial nuclei of the anterior hypothalamus, the second and third interstitial nuclei (INAH 2 and INAH 3, respectively) were significantly larger in men than in women (Burr, Separate 26; LeVay 120). Knowing that the hypothalamus controls sexual drive, people began to wonder, if there is hypothalamic dimorphism between men and women, is there any hypothalamic dimorphism between heterosexuals and homosexuals? In 1991, Simon LeVay tried to answer this question by studying the brains of heterosexual and homosexual subjects that had died of AIDS. LeVay, however, first examined the hypothalamus of each subject without knowing the subject’s sexual orientation. Upon comparison between sexual orientation and hypothalamus size, he found that, on average, INAH 3 was two to three times smaller in homosexual men; this suggested “that gay and straight men may differ in the central neuronal mechanisms that regulate sexual behavior. ... It is very likely that there are fewer neurons in INAH 3 of gay men (and women) than in straight men. To put an absurdly facile spin on it, gay men simply don’t have the brain cells to be attracted to women” (120). Critics of LeVay’s study claim the detrimental effects of AIDS explain the difference in brain structure. But as LeVay points out, there was no evidence of AIDS having an effect on the subjects’ hypothalami. Both groups were AIDS-infected; had the disease had an effect on the hypothalamus, the INAH 3 should have been the same size in both groups, yet they were not. Furthermore, only INAH 3 showed any significant size difference; why wouldn’t the disease have deformed the other three interstitial nuclei? There were also no signs of pathological damage, such as inflammation or dying cells, which normally accompany the deterioration of brain cells due to disease. Finally, when the brains of gay men who died of other diseases were examined, LeVay obtained the same results (121). Those advocating the idea that there is a high probability that sexual orientation has a biological component had just gained yet another pillar of proof to support them.

            Researchers first suspected that homosexuality might also be gene-related when they studied the occurrence of gayness in siblings. Franz J. Kallman’s and W. W. Schlegel’s experiments in the 1950s and 1960s showed that identical twins had a 100 percent concordance rate for homosexual orientation, where concordance is defined as the level of similarity existing for different characteristics (Wertz 1). Although the results seemed overwhelmingly high, they laid the base for further studies. In 1991, J. Michael Bailey and Richard C. Pillard conducted a similar experiment comparing identical twins, fraternal twins, and nongenetically related adopted brothers. By placing advertisements in gay newspapers, they were able to be relatively certain that the twin responding to the ad was homosexual; by sending the other twin a questionnaire, they were able to determine the other twin’s sexual orientation. If homosexuality is genetically linked, the probability of both identical twins being gay should be higher than that of fraternal twins, which should be still higher than that of nongenetically-related brothers. Indeed, Bailey and Pillard found that both siblings were gay in fifty-two percent of identical twins, in twenty-two percent of fraternal twins, and in only five percent of nonrelated brothers (Burr, Separate 35; Hamer 28; LeVay 112; Wertz 1). In 1994, Frederick Whitham of Arizona State University conducted a similar study and determined that if one twin was gay, there was a sixty-six percent chance that his/her twin would also be gay (Matthews). Granted, if homosexuality was solely gene dependent, Bailey and Pillard would have found 100 percent gayness in identical twins. Though their results did not reveal such a relationship, the numbers were significant enough that they could conclude that homosexuality is gene related.

            Yet perhaps the most compelling evidence that sexual orientation has a biological basis came in 1993. Dean Hamer, examining the family trees of gay men, noticed a pattern of inheritance through the maternal side; as a result, he hypothesized that homosexuality may be an X-linked trait since men inherit their X chromosome from their mother. To test this theory, Hamer collected a group of forty gay brothers and drew blood samples to examine their DNA. For thirty-three of the forty brothers, he discovered a remarkable concordance for five markers on a section of the X chromosome called Xq28, where concordance is defined to be the similarity between the markers. Statistical analysis showed that the probability of this concordance happening by sheer chance was less than one in 100,000 (138). Hamer also found that no other region of the X chromosome is linked to sexual orientation, for none of the sixteen markers outside Xq28 showed any statistically significant concordance (139). Upon repeating the study again, he obtained the same results. Thus, it makes sense that Hamer found gay men to have more maternal relatives who were gay than paternal relatives because homosexuality is X-linked. Admittedly, Hamer has not isolated a “gay gene,” but rather a region of over five million base pairs in which such a gene may exist. Critics wonder why “the researchers did not do the obvious control experiment of checking for the presence of these markers among heterosexual brothers of the gay men they studied” (qtd. in Hamer, 141). Yet the answer is obvious: Hamer was not trying to prove that Xq28 alone determines a person’s sexual orientation, but rather that there is a genetic basis for homosexuality. Combined with the results of other genetic studies, Hamer’s findings only strengthen the argument that homosexuality has genetic links.

            Fewer experiments have investigated homosexuality in women, but preliminary studies have been promising. In 1990, researchers at McMaster University in Ontario, Canada examined the occurrence of left-handedness in heterosexual and homosexual women. Brain organization in left-handed people is known to be slightly different than in right-handed people. For example, left-handed people tend to have their language area centered in the right hemisphere of their brain; it is generally accepted that the area for language is in the left hemisphere. Even though only thirty-five percent of the general population is totally left-handed, the scientists found that sixty-nine percent of homosexual women were totally left-handed (Underwood 51). As a result, they suggested that homosexuals have a different brain organization than heterosexuals. Referring to studies in which women with higher than normal levels of masculinizing hormones such as testosterone were more likely to be left-handed and gay, they hypothesized that atypical sex hormone levels during pregnancy may have affected lesbians’ early fetal development.

            In 1992, Bailey and Pillard followed-up their experiment on homosexual men by studying identical twin, fraternal twin, and nongenetically related adopted sisters. As expected, their results mirrored those found in their gay brother study. Whereas only six percent of adopted sisters were both lesbian, sixteen percent of fraternal twin sisters and forty-eight percent of identical twin sisters were both lesbian (Burr, Separate 35). Clearly, the basis for a similar argument for predetermined homosexuality in women has been laid.

            Although genetics may not be the sole reason individuals are homosexuals, recent research has shown that sexual orientation certainly has biological links. Homosexuality has nothing to do with disturbed mentalities. Homosexuality has to do with brain anatomy and genetics. Homosexuals might even be gay before they are born. But even more simply, as Angelican Archbishop Benjamin Tutu of South Africa wrote, “if this sexual orientation were indeed a matter of personal choice, the homosexual persons must be the craziest coots around to choose a way of life that exposes them to so much hostility, discrimination, loss, and suffering.” Homosexuality is not a choice. It’s a way of life.

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“What Do Professional Organizations and Researchers Say?” n. pag. Online. Internet. 1 November 1997.
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