Born This Way: Is Sexual Orientation Innate?
Kara Ireland
Armstrong State University
Born This Way: Is Sexual Orientation Innate?
The validity of the various sexualities has been a topic of debate for decades. Some believe that it is either a disease, a psychological disorder, an unnatural sin, or that it is a choice made willingly to oppose societal norms. Many self-identified homosexuals readily oppose that mindset with the notion that sexuality is fluid and that it, on the contrary, was not their decision. Amongst presuming heterosexuals, it can be debated to an extent. However, amongst homosexuals, there is only one answer: they were born that way. Is there any scientific evidence to support this claim? Is it an opinion or a fact? This topic is important to psychology because it contributes to the nature versus nurture discussion and the etiology of sexual orientation. In the discussion of nature versus nurture, sexual orientation seems to get tossed back and forth and it begs the question: is homosexuality innate or developed?
Simon LeVay had the impression that it could be explored and explained through the examination of brain structures. The anterior hypothalamus of the human brain has a role in the management and regulation of male-typical sexual behavior. With this knowledge, LeVay performed his own autopsies on the brains of 35 homosexual and heterosexual patients with acquired immunodeficiency syndrome (AIDS). He severed the hypothalamus to conduct his study. Four cell groups were scrutinized in this area called the interstitial nuclei of the anterior hypothalamus, shortened to: INAH. Severing and measuring INAH 1, 2, 3, and 4 offered more insight on whether the nuclei of the hypothalamus was dimorphic with sex differences or sexual orientation. His focus was predominantly on the third interstitial nucleus of the anterior hypothalamus, shortened to: INAH 3, which was found to be dimorphic with sexual orientation. The term dimorphic simply means representing two different forms. In this case, the two forms were heterosexuality and homosexuality. Through LeVay’s discoveries, it was found that the volume of INAH 3 in heterosexual men is twice as large in homosexuals. The difference was highly significant. He used 41 subjects from autopsies in New York and California: 19 men with AIDS, 7 heterosexual men, 8 heterosexual women, and 1 bisexual man. The age range of homosexual men was 26-53 years, 33-59 years for heterosexual men, and 29-59 years for heterosexual women. Homosexual women were not included because they were not as widely affected by AIDS. In 15 cases were the nuclei in both left and right hypothalamus traced, in 12 were only the left nuclei traced, and in 14 were only right traced. His findings were ultimately proved to be preliminary because of the various loose ends after he’d concluded his research. Because of his diseased sampled population, there was the possibility that the size difference was credited to AIDS rather than to the sexuality of his subjects. However, even when compared to heterosexual and homosexual AIDS patients, there was no effect of AIDS on the volumes of the other nuclei. There was also no correlation in the volume of INAH 3 and the survival length since time of diagnosis of AIDS, but that evidence is not strong enough to validate his results. The possibility of unreliable sample of the population was high because not all homosexual men are promiscuous or receive anal pleasure, which is the easiest way to contract the disease. It is difficult to make definitive statements about the correlation between brain structure and sexual behavior, but this has provided evidence that sexual orientation can be studied at the biological level and that INAH 3 does influence sexual behavior.
Another possible biological indication of sexual orientation can be found in the measurements and ratio of finger lengths. The ratio of finger lengths of the second and fourth fingers (2D:4D) differs by sex. There was a speculated relationship between the ratios and various traits relative to prenatal sex hormone levels. Such traits included fertility, sexual attitudes and orientation, status, and cognitive abilities. To test their hypothesis that fluctuating asymmetry was a “widely-employed proxy measure of underlying genetic quality”, they reassessed the relationship between 2D:4D and the variables claimed to be related to 2D:4D (Putz, Gaulin, Sporter, & McBurney, 2006). Focusing exclusively on sex hormones, they also examined the relationship between voice pitch, sociosexuality mating success, and fluctuating asymmetry. Fluctuating asymmetry refers to minute, random deviations from perfect symmetry in bilaterally paired structures, such as fingers in this case. The participating subjects included 230 male undergraduates between the age range of 18-30 from the psychology subject pool at The University of Pittsburgh. In this study, they signed the consent forms and were seated at computers, then given a headphone/microphone set and a short, written passage. Subjects were then instructed to read the passage out loud. Further instruction consisted of being told that they would be competing with another male for a lunch date with a woman in a third room, but both of those counterparts were audio-recorded – unbeknownst to the subject. To test the factors, the subject read the passage aloud, described himself to the female, and described why other men might respect or admire him. He performed these tasks to test for baseline, courtship, and competitive recordings. Following that, each subject was given a questionnaire that served to assess social and physical dominance, sociosexuality, sexual interest in the potential dates, and prior mating success. The results of their study concluded that high positive correlations were found for sex differences, although the predictor for other sex hormone mediation traits are limited. The study was conducted to research the validity of a variance of hypothesis, but in sexual orientation, 2D:4D was significantly correlated to the left hand in women, and in the right hand in men. Most of the measured sex differences in 2D:4D supported the role of sex hormones in the development of finger lengths. This is a biological influence that was linked to sexual orientation.
Another endeavor in unveiling biological influences was conducted in 1993 to explore the relationship between sexual orientation and X chromosomes. It is speculated that there is a specific trait that indicates sexuality that can be passed down maternally, via the X chromosome. Their hypothesis was that if such a gene did exist, then it should appear in genetically related gay men – that those men should share the same genetic marker on their X chromosome. They performed a study using a sample of 40 pairs of families with two homosexual brothers as their primary subjects and their mother or another sibling as a secondary reference. Those sibling pairs were thought to be reliable because it offered a plethora of “theoretical and practical benefits” (Hamer, Hu, Magnuson, Hu, & Pattatucci, 1993). Those patients were nonparametric and independent of gene penetrance and frequency, it allowed them the capability of detecting a single linked locus despite any additional genes or environmental conditions that were required to express the trait, there were no “false negatives” because heterosexual brothers were not studied, and several other indications that made those subjects preferable (Hamer, et al,. 1993). DNA was gathered from all of the available members of these families. Their DNA was then assessed and typed for the span of 22 markers exclusive to the X chromosome. Each sib-pair was scored as either concordant-by-descent (labeled: D) if the mother was found to be heterozygous and both homosexual sons inherited the same allele from her, concordant-by-state (labeled: S) if the mother was unable to participate and both sons shared the same allele, discordant (labeled: -) if the sons had two different alleles, or noninformative (labeled: n) if the mother was considered homozygous for the marker. The linkage analysis consisted of a statistical analysis of the pair-by-pair data and the multipoint mapping analysis of the X chromosome, overall, using a molecular linkage method. The main outcome was the detection of linkage between homosexual orientation and markers in the distal end of the X chromosome called: Xq28. On that trait supposedly lies the homosexual gene or one that contributes to homosexuality. No mutations were found there, thus providing more evidence for eliminating the theory that homosexuality is a disease. In their results, it was discovered that one kind of homosexuality was indeed transmitted through the mother, because they found no similarities in the fathers or sisters of the homosexual brothers. The same trait was found on Xq28 in 33 of the 40 self-identified homosexual brothers with a 1% margin of error. It was concluded that Xq28 contains the gene that contributes to homosexuality. These results offer a more apt notion of biological influences on sexual orientation because there was no disease prevalent in the patients.
Amongst those prenatal influences, there were also many studies regarding sexuality between monozygotic twins to explore the possibility of heredity. One study in particular measured the concordance rate in sexual orientation between several pairs of monozygotic (labeled: MZ) twins in comparison to the rate in dizygotic (labeled: DZ) pairs. Monozygotic twins are known as identical twins while dizygotic twins are known as fraternal twins. They recruited 55 pairs of male and female MZ twins and 16 pairs of DZ twins. Two sets of triplets were included, identified as three pairs each. The key concept with these twins was that they were all reared apart, separated at birth, adopted by different families, and then reunited in their adult lives. Each subject underwent medical and psychiatric evaluations in addition to completing a questionnaire regarding their sexual experiences. Of the 55 pairs that participated, only 5 identified as exclusively homosexual – 2 male pairs and 3 female pairs. One of the female pairs identified as bisexual as well. None of the DZ pairs identified as exclusively homosexual. Their results consisted of an overall confirmation that male pairs confirmed earlier studies of male twin homosexuality rates, while the female pairs did not report as well. The concordance rate of sexual orientation is more significant in MZ pairs than in DZ pairs, which was also found in Heston’s homosexuality study (1968). It provides evidence for genetics being another etiological factor for homosexuality. The possible issues with this study were avoided due to the twins being reared apart, such as environmental factors that could’ve influenced or been reasonably associated with their sexual orientation. All dissimilarities recorded were non-genetic and linked to environment in their case.
There are a sufficient number of discoveries in this field towards the etiology of homosexuality and the differences amongst sexual orientation. Although environmental factors do have a role in the development and expression of homosexuality, it is not strictly the cause. Because X chromosomes appear to contain the gene that has been linked to homosexuality, it poses a strong argument towards its relation to genetics. The absence of mutations in the X chromosomes from tested subjects contradict the theory that homosexuality is a disease or a disorder. From this research, it seems that there are indeed biological factors that cause homosexuality. The brain and genetic differences of those with homosexual and heterosexual orientations support that claim. Preferences hardly contribute to the structure of the brain. Preferring apples over oranges will not result in a difference in your interstitial nucleus of the anterior hypothalamus versus one that prefers oranges over apples. That preference would not amount to a different trait on the distal portion of Xq28, either. Further research can still be done to strengthen the results of previous studies. More studies can be conducted using a wider variance of subjects to improve LeVay’s study, ones without AIDS, to see if the results remain and can therefore be exclusively applied to homosexuality. Perhaps more studies can include homosexual women and the etiology behind their development, because most current ones are male-oriented. Those genetic determinants further endorse the idea that human sexuality is neither learned, nor chosen, nor indicative of a disease, but that it is simply innate.
References
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