Shenk states in Chapter 1 that genes are a “giant control
board inside your body” (19). He
follows this up by arguing that this control board can be changed with switches
turned on and off with different environmental factors throughout development.
Therefore, would this eliminate the argument that sexual orientation is a
birth-given trait and rather is determined by early environment? Shenk
explicitly states that this may be the case: “there is not genetic foundation
that gets laid before the environment enters in” (21). Try to relate to
biological unit of ecology and relations within species.
The correlation between genes and sexual orientation is a hotly debated topic today. One of the defining moments in the debate was in 1993 when Dr. Dean Hamer and his colleagues working for the National Cancer Institute claimed they had discovered, “ a gene for homosexuality seemed to be maternally linked and found on the Xq28 stretch of the X chromosome (http://www.bio.davidson.edu/courses/genomics/2002/pierce/gaygene.htm).” In fact Dr. Hamer was 99.5% sure that there is a gene that predetermines sexual orientation in males. This was dubbed the “gay gene” and is often cited by those who claim that sexual orientation is determined by genes. In 1999, the experiment was duplicated by George Rice and George Ebers who concluded that their results “do not support an X-linked gene underlying male homosexuality.” This experiment was therefore disproven and although many people will cite this particular experiment, it must be noted that Dr. Hamer’s finding’s were not duplicated by other scientists.
ReplyDeleteIn recent years the hunt for a gene that could determine sexual orientation still continues. Scientists are coming to the conclusion that the environment and gene’s are responsible for sexual orientation. This is similar to what Shenk says on page 15, “They [genes] interact with the environment in a dynamic ongoing process that produces and continually refines an individual.” A recent study done by Swedish scientists compared the sexual orientation of twins (fraternal and identical). They noticed greater similarity in sexuality between identical twins which makes the case for genetics as a factor in sexual orientation, since identical twins are more closely related genetically. The biggest statistic they found though was that, “Overall, genetics accounted for around 35 per cent of the differences between men in homosexual behavior and other individual-specific environmental factors accounted for around 64 per cent. In other words, men become gay or straight because of different developmental pathways, not just one pathway. (http://psychcentral.com/news/2008/06/30/genetics-and-environment-shape-sexual-orientation/2522.html).” This argument takes into account both genes and the environment and effectively argues that there are certain genetic factors that have an effect on sexual orientation but for the most part it is the environment that dictates sexual orientation.
In regards to one of our overarching biological themes, what is the evolutionary advantage of being gay? After all we have often discussed, that the goal of animals is to survive and reproduce? As we learned in our reproduction unit most animals reproduce sexually. Also, in chapter 51 we learned about different mating systems such as polygamy and monogamy but in both cases it is sexual relations between males and females, not between animals of the same sex. One of the explanations for the evolutionary advantage is that gay individuals in a population will help those who they are closely related to rather then producing their own offspring (http://www.pbs.org/wgbh/pages/frontline/shows/assault/genetics/evolution.html). This idea is related to altruism and kin selection which we discussed in the Ecology unit (Chapter 51). Although these individuals are not having offspring they are helping young animals who are genetically similar survive and reproduce and therefore are helping pass some of their own genetic material. Another article in The Economist also says that, “There are also data which suggest that having a more feminine personality might indeed give a heterosexual male an advantage (http://www.economist.com/node/12465295).” Thus, there is evidence that being homosexual does have biological and evolutionary advantages that help pass on genes.
Sid Dash
sdash27@gmail.com
This comment has been removed by the author.
ReplyDeleteCurrently, scientists are asking the same question: what contributes to sexual orientation? Following suite with Shenk’s hypothesis, scientists such as Dr. Qazi Rahman are finding that sexual preference is governed by the interaction between environmental factors and genes (http://www.medicalnewstoday.com/releases/113259.php). Environmental factors such as exposure to hormones during a fetus’ internal development are hypothesized to largely contribute to the development of sexual orientation (http://www.medicalnewstoday.com/releases/113259.php). In short, sexual orientation, as a trait, is not solely caused by genetics—as Shenk says, “we do not inherit traits directly from our genes. Instead we develop traits through the dynamic process of gene-environment interaction” (Shenk 21). As Sid addressed, genetic research on this topic is still underway and controversial. However, the question of sexual orientation is more complex than a simple GxE interaction.
ReplyDeleteSexuality, as previously stated, is partially genetically linked. While GxE may influence almost all traits, the influence of genetics is particularly puzzling when two beings expressing a trait such as non-heterosexual orientation (e.g. homosexual or bisexual) may not be able to pass on genes that contribute to the trait because they cannot reproduce together. Still, homosexuality has been evident as a trait for thousands of years in hundreds of species of animals and is prevalent in today’s society: according to a 1993 study, 2-11% of the U.S. population was homosexual (http://alexbacker.pbworks.com/w/page/1721175/The-Evolution-of-Homosexuality). I would argue that that statistic misleadingly underestimates the population of people who are not heterosexual as it left out some demographics, and the only way to gather data on sexuality is by having the data be self-reported, and a topic as personal as sexuality may cause individuals to give illegitimate responses (in 2012, people may be more comfortable expressing their sexualities than in 1993). The significance of the prevalence of different sexual orientations is that there must be or have been a selective advantage for individuals expressing that trait. As expressed in Section 51.4 of the Campbell textbook, animals express ornate, sometimes dangerous, agonistic behavior, “an often ritualized contest that determines which competitor gains access to a resource, such as food or mates” (Campbell 1136). Animals expressing homosexuality would not be perceived as threats for mate-selection, therefore preventing them from dying in a mating ritual.
Moreover, non-reproducing numbers of a population could be vital to keeping that population alive, an idea relating to interdependence in nature. Resources such as food, water, and space are supplied by a population’s environment. By having members of the population that could help the group by exhibiting altruism (e.g. hunting to supply the population with food, defending territory of the population, etc.) that don’t reproduce, that population can receive the benefits of an active member of its society without pushing the population closer to its carrying capacity via reproduction. Sid mentioned personality type and social role associated with gay members of a population, but I would argue that the statements of his sources in this context are misleading: attraction to a member of the same sex is inherently a characteristic of the opposite sex (e.g. attraction to a male is typically a female trait, therefore it is a feminine trait for a male to have), but sexuality as a whole is too complex to associate other specific personality traits with. Overall, I agree that the variation of personalities and traits such as sexual orientation amongst a population, and an increase in diversity, is beneficial to that population. Even if individuals identified as an orientation other than heterosexual will not always reproduce, the trait will help individuals expressing it survive as well as the rest of the population.
-Kyle Mueting
kylemueting@comcast.net