This is a research paper regarding homosexuality as a sexual orientation, not as an issue with marriage/gay rights. It's a more objective, factual paper than my editorial on gay marriage. Enjoy.
Nature vs. Nurture: Nature wins Sexual orientation has long been a dark area for researchers, a mystery shrouded by taboo, hidden away by conservative forces. Charles Darwin once stated, “We do not even in the least know the final cause of sexuality. The whole subject is hidden in darkness.” Specifically, the subject of homosexuality has long puzzled scholars, from the philosophers of Ancient Greece, to evolutionists like Darwin, to modern biological theorists such as Alfred Kinsey. In 1975, the American Psychological Association, in response to a study sponsored by the National Institute of Mental Health, announced that homosexuality was not a mental disorder. As a result, psychologists and social theorists alike questioned whether an individual was born with same-sex tendencies, or if they were created through environmental influences. This debate continues today with more specific viewpoints. The argument for biological determinism includes studies on the hypothalamus, neuroendocrine levels, chromosomes, as well as monozygotic twins. Due to the fact that these experiments present evidentiary support, as opposed to claims of social theorists, they hold more ground in favor of the case for biology. Therefore, in the ongoing debate concerning nature versus nurture, homosexuality is best categorized as a product of nature.
The first argument for biological determinism, in regards to homosexuality, concerns the human brain. Specifically, the hypothalamus is the area of the brain that controls sexual drive and function. In the last twenty years, at least three scientific studies have shown that there are size discrepancies between the hypothalamus of homosexuals, and that of heterosexuals. The first of these experiments was carried out by D.F. Swaab in 1990. Using the brains of deceased homosexuals, Swaab discovered that, “a small portion of the hypothalamus, termed the suprachiasmatic nucleus (SCN), was found to be twice the size of its heterosexual counterpart” (Johnson). At around the same time, a scientist named Laura Allen contributed another observation regarding the hypothalamus. In her experiment, she compared a different part of the brain to find “the anterior commissure (AC) of the hypothalamus was also significantly larger in the homosexual subjects than that of the heterosexuals” (Johnson). A year later, Simon LeVay conducted perhaps the most controversial experiment of the three. LeVay examined post-mortem brains of homosexual males, heterosexual males, and heterosexual females, all of whom had died from AIDS. This time, the interior of the hypothalamus was observed, and he concluded that “the third interstitial notch of the anterior hypothalamus (INAH3) was two to three times smaller in homosexual men than in heterosexual men” (Johnson). The most interesting aspect of this experiment was the fact that the smaller INAH3 in homosexual men matched that found in heterosexual women. This implied that homosexual males would have similar sexual tendencies as heterosexual females. Critics pointed out that some parts of the human brain, in terms of size and density, change over time as a result of certain behaviors. However, further research indicated that the anatomy of these cerebral areas is solely determined by prenatal development, and thus cannot be altered by an individual’s actions, “The size and shape of the human brain is determined biologically and is impacted minutely, if at all, by behavior of any kind” (Johnson). In other words, while it is not certain that these areas create homosexual conduct, it is evident that their sizes do not vary as a result of same-sex behavior. Therefore, these three experiments leave little doubt as to the differences in brain size between gay and straight individuals, pointing towards a biological source for homosexuality.
In accordance with the hypothalamus, neuroendocrine studies make up another case in favor of nature over nurture for homosexuality. In this sense, chemicals excreted by males and females are suggested to act as pheromones, which stimulate the hypothalamus. This reaction is said to influence the sexual orientation of an individual. Researchers performed a study in which they used a testosterone derivative, known to attract heterosexual women, as well as an estrogen derivative, known to attract heterosexual men. Specifically, they tested the hypothalamus reactions of homosexual men, heterosexual men, and heterosexual women to these two different compounds. The results were consistent in their conclusion: “The researchers found that the testosterone compound activated the hypothalamus in homosexual men and heterosexual women, but not heterosexual men. Conversely, the estrogen compound activated the hypothalamus only in heterosexual men” (Connors). This experiment revealed that the homosexual men and heterosexual women were similar in their reactions to the testosterone; essentially, they were attracted to males. In 2005, the Monell Chemical Senses Center went further by studying the responses to odors released by homosexual men. Scientists wanted to know if such odors were different in chemical makeup than those produced by straight men and women. Using a similar group of gay men, straight men, and straight women, they found that “gay men preferred odors from other gay men, while odors from gay men were the least preferred by straight men and women” (Connors). The science behind these observations has not been conclusive, but the results cannot be denied. From this, it can be derived that while homosexual males favor testosterone compounds, they actually prefer odors given off by other homosexual males. Homosexual tendencies are influenced on a neuroendocrine level, pointing to the idea that homosexuality stems from biological traits.
Another premise in favor of the argument for biological homosexuality involves chromosomes. More specifically, researchers believe they have uncovered a “gay gene”, a specific location on a chromosome that determines homosexuality in an individual. The search for this gene began with the initiation of the Human Genome Project in 1990, and by 1993, the first scientific report was published by Dean Hamer. Hamer and his colleagues, working for the National Institute of Health, carried out an experiment using forty pairs of homosexual brothers. They used brothers who had homosexual relatives on their mother’s side only, as the initial purpose of the experiment was to test if homosexuality was a sex-linked trait. They took blood samples from each pair of brothers, and then matched them with their respective family members. “Five markers at the tip of one arm of the X chromosome (the Xq28 region) were found to be matched in thirty-three of the pairs of brothers”, and thus, the Xq28 region was labeled as the location of the “gay gene” (Rogers). To be sure, there are hundreds of genes in this tiny portion of the X chromosome that could account for a number of varying behaviors, and not solely homosexuality. However, it seems clear that there is a consistent correlation between gay behavior and the Xq28 sequence, supported by a repeat experiment in 1995. Another important part of the conclusion points to the fact that homosexuality is passed on through the mother. Since Xq28 is found on the X chromosome in males, it has to be inherited from the mother, “because a male inherits his Y chromosome from his father and his X chromosome from his mother, any characteristic carried on the X chromosome will be passed on from mother to son, not father to son” (Rogers). So not only does a “gay gene” exist, but it is sex-linked through the mother. Therefore, there are at least two connections that can be drawn between homosexuality and chromosomes, further substantiating the argument in favor of nature over nurture.
A similar genetic conclusion for biological determinism in homosexuals can be made based on behaviors of monozygotic, or identical, twins. Before Hamer’s “gay gene” experiment was carried out, two psychologists named Michael Bailey and Richard Pillard conducted a 1991 study regarding the sexual orientation of the siblings of 110 gay men. They wished to find parallel behaviors between identical and fraternal twins, non-twin brothers, and adopted brothers. The results suggest significant correlations: “These researchers found a concordance rate of 52 percent for identical (monozygotic, or MZ) twins, 22 percent for fraternal (dizygotic, or DZ) twins, 9 percent for non-twin brothers, and 11 percent for adopted brothers” (Williams). This means that of the 110 gay men tested, over half of them carried the same homosexual tendencies as their identical brothers. At the same time, fraternal twins also shared a notable amount of similarities. Amidst criticism that lesbians were not being addressed, a similar study was carried out in 1993 for gay women. The results were analogous: “Bailey and his colleagues reported a concordance rate of 48 percent for MZ twins, 16 percent for DZ twins, 14 percent for non-twin sisters, and 6 percent for adoptive sisters” (Williams). Since these identical twins carry nearly the exact same DNA, it seems logical that the high homosexual rate was due to genetics. In fact, the more similar the siblings were in genetic makeup, the more similar they were in sexual preferences. Despite this evidence, critics maintain that there are many twin pairs where one sibling is gay and the other is straight, completely nullifying the conclusion of the study. These twins are examples of exceptions, as indicated by the numbers of the experiment. Although the results were not absolutely in favor of homosexual links between twins, there is substantial evidence to make such a case. The fact that about half of all identical twins share gay traits between each pair points towards a biological basis for homosexuality, found specifically in genes.
Brain size, pheromones, chromosomes, and twins are all examples of genetic characteristics that support the argument for the nature of homosexuality. This physical differentiation between straights and gays is indisputable evidence that biology plays a significant factor in the sexual orientation of an individual. However, this is not to say that biology is the sole aspect. Environment can also play an important role in a person’s sexual behavior. For example, it is the environment which often determines when a person “comes out”, and makes their sexual orientation known to others. As a taboo in many countries, homosexual tendencies are frequently difficult to embrace, and many go their entire lives deceiving others and themselves by living a heterosexual life. Kathleen Boatwright, for example, lived a strict Christian life until she could no longer deny her feelings, “I recalled the feeling of walking through the Waldenbooks bookstore, looking at The Joy of Lesbian Sex and longing for that kind of intimacy. It all came upon me at that moment, and I felt a real willingness to release myself” (Marcus). People in her position tend to admit that they always had certain homosexual tendencies, but they were blinded from it by conservative pressures. Therefore, it is reasonable to say that homosexuality is nature-based, but the acceptance and growth of gay behavior depends heavily on nurture. Either way, biology is an incontrovertible part of homosexuality in every culture, in every country, and in every person.
