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There has been much discussion on the etiology of homosexuality. The debate seems to be divided, with those who believe in innate causation in one corner and those who believe in influences of environmental factors in another. Although some still perceive homosexuality as controllable (environmental or an individual choice), virtually all the scientific findings over the last two decades on the etiology of homosexuality are biological in character giving more support to those who believe gays are biologically 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, discovered through empirical and practical scientific research, is overwhelming: male homosexual orientation is caused by genetic inheritance, prenatal hormonal development and brain structural and organizational differences.
For the purpose of accurate understanding of the arguments presented in this paper, it is essential to define some terminology. Homosexuality is a sexual orientation of "emotional and sexual attraction to members of one's own sex" (The Columbia Encyclopedia 2008). According to the American Psychological Association, sexual orientation is "an enduring emotional, romantic, sexual or affectional attraction that a person feels towards another person." It is important to note that sexual orientation and sexual behaviour differ. Sexual behaviour refers to the manner in which humans experience or express their sexuality, orientation. The behaviour does not necessarily correspond with one's sexual orientation. As an example, some heterosexual males practice homosexual behaviour in prisons. Accurate understanding of the differences in definitions of sexual orientation and sexual behaviour has important implications for possible causation theories of homosexuality. Homosexual orientation cannot be a conscious choice as some might think. Attractions and desires are like feelings; they come from deep within a person and are not a conscious or controllable choice on one's part. To engage in homosexual behaviour could be a personal choice; however, sexual behaviour of a person does not necessarily represent his sexual orientation.
Engle et al. state that the most important recent scientific research points to biological factors as the causation of homosexuality in males (69). Through various experiments, they concluded that there is an emerging trend of more and more people shifting away from environmental theories toward the biological ones (69-70). Specifically, they tested psychiatrists and sociologists that traditionally believed in environmental theories.
Perhaps the most compelling evidence that sexual orientation in men has biological bases 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 (Abrams 58). Inspecting the X chromosomes of 76 pairs of gay brothers, Hamer discovered a shared genetic marker on DNA, Xq28 (Abrams 58). By locating the stretch of chromosome where one of the genes involved resides, the finding proves that male homosexuality is at least partially genetic. Hamer claims that his inability to find the specific 'gay gene' is due to the high cost of scanning every set of chromosomes in the participants under high degree of resolution. As well, Bocklandt, Hamer's partner, points out that most likely there is no single 'gay gene', but rather a handful of genes that work in ways that are not yet explained (Abrams 60). 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.
Another study that indicates male homosexuality to be genetically predetermined was conducted by a psychologist Michael Bailey (Abrams 59). Bailey compared identical twins, fraternal twins, and non-genetically related adopted brothers. He hypothesized that 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 non-genetically related brothers. Indeed, Bailey found that both siblings were gay in fifty percent of identical twins, in twenty percent of fraternal twins, and in only five percent of nonrelated brothers (Abrams 59). Granted, if homosexuality was solely gene dependent, Bailey would have found 100 percent gayness in identical twins. Though their results did not reveal such a relationship, the numbers are significant enough that he could conclude that homosexuality is gene related.
The results of Michael Bailey's experiment stirred a lot of debate between the two camps. Those who consider homosexuality to be caused by environmental factors attempted to use this experiment as evidence for their belief. They noted that since twins have the same genes, both brothers should have the same sexual orientation. However, even if homosexuality was caused by environmental factors, such as culture and family up-bringing, it would still not explain the disparity between sexual orientations in twins. Most likely both twins would be brought up in the same cultural and family environment, so once again their sexual orientation should be the same. Thus, environmental theories do not account for the disparities either.
In later experiments, Bocklandt finally found the explanation for the disparity and once more, it was genetically based. He showed that while identical twins share the same DNA, the activity of their genes is not necessarily the same due to a chemical called methylation (Abrams 61). Methylation "turns off certain sections of genetic code" (Abrams 61). Therefore, even though we inherit two copies of every gene, whether the gene is methylated often determines which of the two genes will be turned on. The chemical is influenced by diet and environment and thus can change from one generation to the next (Abrams 61). This mutability accounts for disparities in Bailey's twin studies and proves that male homosexuality is genetically based.
As Abrams notes, the environment in the womb also influences male homosexuality (6). Ray Blanchard found that men with older brothers were more likely to be gay than those without (Abrams 64). He believes that with "each male child the mother develops immunity to certain male-specific proteins related to the Y chromosome" (Abrams 65). Her body develops antigens that can alter certain structures of the male brain that pre-determines his sexual orientation (Abrams 67).
Schwartz states that "prenatal hormonal environment determines homosexuality" (22). During prenatal life, fetus`s testis secrete hormones that permanently alter the brain. Thus, any abnormality in the womb can cause non-balanced secretion of the hormones that influence sexual orientation. Abrams, as well, claims that level of testosterone in males can affect certain regions of the brain and in turn alter brain structure (68).
Whatever the cause of homosexuality, be it genetic or hormonal, the result is a change somewhere in the brain. Joel Alexander asserts that 100% of the structural/functional brain studies to date have indicated some finding regarding biological correlates of sexual orientation (249). Mainly, he points to differences in the brains of homosexuals and heterosexuals. Simon LeVay, a neurobiologist, found that an area in anterior hypothalamus known as INAH-3 is smaller in homosexual men than in heterosexual men, about the size it is in women (Abrams 64). INAH-3 regulates involuntary sexual physiology (Gilbert 2000) and any structural distinctions of this region can influence a person's sexual orientation.
The etiology of homosexuality has important implications on the people's tolerance towards gay culture (Haider-Markel and Joslyn; Murphy). If the cause of homosexuality is perceived as controllable, low levels of tolerance toward homosexuals are to be expected. If the cause is perceived as uncontrollable, people tend to show more support for gay policies. However, there is nothing fundamentally immoral about homosexuality, so even if it was chosen by the individual, this should not make it any less acceptable or moral. Finding a biological reason for a trait does not make immoral behavior acceptable: even if it was a biological impulse to kill indiscriminately we would not be any more tolerant towards serial killers. Thus, homosexuality can only be immoral and unacceptable if it is not compatible with key human values and social goods, not simply because it is biological. For greater equality, we should advance the argument that homosexuality is neither immoral nor undesirable; it is part of the normal distribution of human behaviour.
Recent scientific researches support biological explanation as the dominant causation of homosexuality in males. Majority of the sexual dimorphism in structures of the brain is the result of hormonal and genetical influences that effect sexual orientation in males. Biological explanations of sexual orientation indicate that homosexuality is no more nor less natural than heterosexualiy (Murphy 1) and thus encourage greater tolerance towards gay rights and policies.