Kelsey Doolittle

Professor Schwarz

February 20, 2013

Underlying Homosexual Biology

Encouraged by Environmental Factors

The connections between biology and homosexuality include an overwhelming amount of confounding variables. These confounding variables are social and environmental factors. While these factors impact each individual differently, they do not drive whether or not an adult will lead a homosexual lifestyle. Biology is the underlying factor that ultimately determines whether or not an adult engages in homosexual behavior.

There are a few theories which link hormone exposure in childhood and later homosexual behavior. There is evidence supporting a correlation between abnormal prenatal testosterone exposure in both females and males, which correlates with their homosexual lifestyle as an adult. The data supports the possibility that testosterone outside the “critical threshold” of testosterone can lead to homosexual behavior in both sexes. For males, if they fall short of this critical threshold of testosterone, will likely exhibit homosexual behavior. Likewise, females who surpass the critical threshold are likely to exhibit homosexual behavior. This relates an experiment on female rats injected with testosterone before pre-natal day 10. These rats would think they were male and would try to have sex with females. This data demonstrates how hormone levels during brain development can impact later behavior.

Other hormone hypotheses include the maternal immunization hypothesis. This theory speculates about the trend for gay males with older brothers. For each older brother a male has, he is 33 percent more likely to be gay. This is thought to be because of the antibodies that a mother’s body makes against her son’s proteins. After a baby boy is born, proteins from the son enter the mother’s body. The mother’s body then creates antibodies against these proteins. These antibodies enter the placenta of later born sons. Because the later-born son has antibodies against his proteins, his body will not produce them. These proteins are thought to help sexual differentiation, and without these proteins, gender and sexuality could be divergent.

The last hormonal theory states that maternal stress in the womb can lead to homosexuality in a newborn. “If a mother is stressed during the early stages of pregnancy, she will release an adrenaline related hormone called androstendione, [which] is structurally similar to testosterone, the male hormone…because the stress hormone seems to mimic testosterone, there is a delay or blockage of the effectiveness of testosterone, even if it is plentiful. This causes a disturbance in the “defeminization” of the hypothalamus.” (Eden) While this example is a testimony to male homosexual behavior, there is a group of evidence that links this theory to both homosexual behavior in males and females.

Alongside the hormonal levels causing homosexual activity, there is an extraordinary indication that genes play a part. “Several studies also have shown that homosexuality tends to run in families. The probability that the brother of a gay man is gay is about four times higher than normal. Similarly, the odds that the sister of a lesbian is also a lesbian is significantly higher than normal. However, male homosexuality and lesbianism tend to run in different families: sisters with gay brothers are not more likely than normal to be lesbian. A 1993 study that traced the pedigree of pairs of gay brothers found that homosexuality tends to run on the maternal side of the family tree: the brothers had a higher than average number of maternal nephews and uncles who are gay.” (Goldstein) These findings can be explained by the theory of Epi-genetics.

Epi-genetics is the theory that environmental factors determine whether or not a gene is expressed. “Specifically, the researchers discovered sex-specific epi-marks which, unlike most genetic switches, get passed down from father to daughter or mother to son” (Dvorsky) While this is confirmation of a genetic predisposition for homosexuality, it is still ultimately the environment (which includes hormone exposure) which determines the outcome of homosexual behavior expression.

Despite this evidence, there are social factors that should be considered.

One vital factor to consider is societal opinions. Unfortunately, in certain cultures and or social environments, homosexuals do not have the freedom to act on their desires, leaving them unfulfilled. In Uganda, as in other countries as well, it is illegal to practice homosexual relations. “In Uganda, gay people often fear living openly.” (Segona) There are numerous examples of social environments where homosexuality is condemned; and in such, it is possible homosexual individuals will never engage in homosexual behavior. By scientific standards, a person is not homosexual if they do not act on homosexual desires. However, if this social factor were to be removed, the biology would still remain.

Homosexuality is not a choice. Homosexuals often experience early attraction to the same sex, even as early as age 6. (Marcus) While there are recognized environmental factors, these factors encourage gene expression. If these factors do not encourage gene expression, an individual would not be considered homosexual. On these grounds, one can safely say that this early recognition of divergent desires is due to differing hormone levels and gene variants, and the resulting expression of homosexual behavior is due to these underlying biological factors.





Bibliography

Dvorsky, George. “Scientists claim that homosexuality is not genetic – but it arises in the womb.” Genetics, i09. 11 December 2012. I09. 18 February 2013. http://io9.com/5967426/scientists-confirm-that-homosexuality-is-not-genetic–but-it-arises-in-the-womb



Eden, Dan. “Homosexuality is not a choice.” Viewzone. 2011. 18 February 2013. http://www.viewzone.com/homosexual.html

Goldstein, Dora B. “Biological Basis of Sexual Orientation.” Stanford News Service. 10 March 1995. Stanford University. 18 February 2013. http://news.stanford.edu/pr/95/950310Arc5328.html

Marcus, Eric. Is it a choice? Harper: San Francisco, 1993. Print.

Segona, Medard. “Uganda Anti-Homosexuality Bill: MPs drop death penalty.” BBC News Africa. 23 November 2012. BBC. 18 February 2013. http://www.bbc.co.uk/news/world-africa-20463887