The History and Reality of the "Gay Gene"
Is there a Gay Gene?
Scientists have most likely found a "gay gene," but there is no gene that guarantees sexual orientation. Geneticists like Dean Hamer have found a correlation between a gene sequence and male homosexuality in families, but so far no one has isolated the exact gene in this sequence.[1] Having this gene sequence does not guarantee that you will be gay; many people have the sequence and would be described as completely heterosexual. This gene has been shown only to influence sexual behavior, while environmental and social factors can have just as large of an impact on sexual behavior, and it is likely to not be the only "gay gene".[2] Furthermore, the gene only influences male sexuality, and has no noted effect on females.[3]
The Discovery of the Gay Gene
The search for a cause of homosexuality has existed as long as homosexuality itself, but scientifically sound results are only recently coming in. Scientists have never been certain about what causes homosexuality, and most early theories believed it was simply a choice. Once biologists started to study homosexuality in humans, the common theory was that a lack (or sometimes a surplus) of testosterone was causing this so called lack of typical male behavior.
In a 1993 study, Dr. Dean Hamer led a study to try and find a genetic cause of homosexuality.[5] His team investigated self-reported homosexual men and their relatives, interviewing them to standardize their sexuality to the Kinsey Scale and then comparing their genetic sequences. The Kinsey Scale is a popular method for quantifying sexuality, where a person's sexual attraction, behavior, history, and fantasies are used to place them on a scale from 0 to 7, where 0 is exclusively heterosexual, 3 is bisexual with no preference, and 6 is exclusively homosexual. Their study had intriguing results. They found that homosexuals tended to have more homosexual relatives on their mother's side than heterosexuals, but there was no significant difference on the father's side of the family. In addition, they found a correlation between gay brothers and polymorphic markers on the X chromosome. These were statistically significant findings, leading them to believe that there is some gene, designated "Xq28", somewhere near the tip of the X chromosome, that influences sexual behavior.[5] This study was limited, however, as it only looked at homosexuality in men, it did not factor in bisexuality or asexuality (for simplicity's sake), and, according to Hamer, "the most important limitation of our research was that we didn't isolate a 'gay gene'; we only detected its presence through linkage" [6].
Further studies have solidified Hamer's claims, and expanded them by looking at gay women and their relations. These studies suggest that the Xq28 gene impacts male sexuality, but has no significant impact on female sexuality.[3]
In a 1993 study, Dr. Dean Hamer led a study to try and find a genetic cause of homosexuality.[5] His team investigated self-reported homosexual men and their relatives, interviewing them to standardize their sexuality to the Kinsey Scale and then comparing their genetic sequences. The Kinsey Scale is a popular method for quantifying sexuality, where a person's sexual attraction, behavior, history, and fantasies are used to place them on a scale from 0 to 7, where 0 is exclusively heterosexual, 3 is bisexual with no preference, and 6 is exclusively homosexual. Their study had intriguing results. They found that homosexuals tended to have more homosexual relatives on their mother's side than heterosexuals, but there was no significant difference on the father's side of the family. In addition, they found a correlation between gay brothers and polymorphic markers on the X chromosome. These were statistically significant findings, leading them to believe that there is some gene, designated "Xq28", somewhere near the tip of the X chromosome, that influences sexual behavior.[5] This study was limited, however, as it only looked at homosexuality in men, it did not factor in bisexuality or asexuality (for simplicity's sake), and, according to Hamer, "the most important limitation of our research was that we didn't isolate a 'gay gene'; we only detected its presence through linkage" [6].
Further studies have solidified Hamer's claims, and expanded them by looking at gay women and their relations. These studies suggest that the Xq28 gene impacts male sexuality, but has no significant impact on female sexuality.[3]
Sexuality isn't Simple
Someone with the Xq28 gene could be gay, straight, or anything else. While there is a significant amount of homosexual men who have the Xq28 gene (or, rather, the sequence it is known to exist in), there are many men who are homosexual and lack the gene, or are heterosexual and have the gene. The gay gene alone does not determine sexual behavior. Hamer found that "the main problem is not knowing whether a gay man is missing a particular marker... or if he is gay because of some different gene or nongenetic reason" [6]. In short, the exact causes of homosexuality are unknown.
If the Xq28 gene doesn't guarantee homosexuality, what does it do? Studies have suggested that straight men have larger INAH-3 regions in their brain than women and homosexual men. This region is thought to be responsible for male sexual behavior and feelings. In a simple world, Xq28 would code for a protein that stunts the growth of INAH-3. However, sexuality is not a simple topic. The Kinsey Scale is a testament to this. It cannot be boiled down to "are you homosexual or not?" The gay gene itself has not been isolated, and so it cannot be tested and we cannot learn exactly what it does. Furthermore, there could always be more gay genes, undiscovered and interacting in unique ways.[2]
When the gay gene is discovered, a common question is "how did it not die out through natural selection?" While we may never know, the potential answers provide interesting ideas on the potential role of Xq28 in heterosexuals. Xq28 does not guarantee homosexuality, so it could be selected for if heterosexuals gained a fertility boost by having the gene. While we know to little about the gene to say how this works, it is interesting to think that the gay gene could either cause homosexuality or increase heterosexuality [8]. In addition, the existence of Xq28 cannot be dismissed by claims of natural selection, as homosexuality is historically taboo, and gay men have been kept "in the closet," so to speak, which would explain why they have still been reproducing and passing on their genes. Furthermore, the Xq28 gene seems to be inherited from the mother's side of the family.
If the Xq28 gene doesn't guarantee homosexuality, what does it do? Studies have suggested that straight men have larger INAH-3 regions in their brain than women and homosexual men. This region is thought to be responsible for male sexual behavior and feelings. In a simple world, Xq28 would code for a protein that stunts the growth of INAH-3. However, sexuality is not a simple topic. The Kinsey Scale is a testament to this. It cannot be boiled down to "are you homosexual or not?" The gay gene itself has not been isolated, and so it cannot be tested and we cannot learn exactly what it does. Furthermore, there could always be more gay genes, undiscovered and interacting in unique ways.[2]
When the gay gene is discovered, a common question is "how did it not die out through natural selection?" While we may never know, the potential answers provide interesting ideas on the potential role of Xq28 in heterosexuals. Xq28 does not guarantee homosexuality, so it could be selected for if heterosexuals gained a fertility boost by having the gene. While we know to little about the gene to say how this works, it is interesting to think that the gay gene could either cause homosexuality or increase heterosexuality [8]. In addition, the existence of Xq28 cannot be dismissed by claims of natural selection, as homosexuality is historically taboo, and gay men have been kept "in the closet," so to speak, which would explain why they have still been reproducing and passing on their genes. Furthermore, the Xq28 gene seems to be inherited from the mother's side of the family.
How does the Gay Gene affect HIV/AIDS?
The idea of a gay gene has been around for decades, but research into the matter has been scarce. Most experiments have been done to try and determine if it exists, and so actual research into what exactly the gene does has not yet been done. This prevents us from knowing if the gay gene makes homosexual men more prone towards contracting AIDS. However, experts in the field, such as Dean Hamer, see no reason to suspect one.[9] Any correlation between homosexuality and AIDS can be explained by historical context and lifestyle, leaving no reason to think that homosexuals are predestined to get HIV/AIDS.
Professor Chris Beyrer of the Johns Hopkins Center for Public Health & Human Rights investigated the link between gay men and HIV/AIDS in 2012. He analyzed sexual behaviors associated with gay men, and found that they can explain the higher rates of the disease in gay men. A person in the receiving role during anal sex is nearly twice as likely to contract HIV as someone in the receiving role during vaginal sex. In addition, gay men are able to switch who is in the receiving and inserting roles, which can expose both parts to this increased chance of contraction.[10] In addition, there is social stigma associated with being gay, and this makes it harder for homosexual men to seek treatment and health care that could help prevent them from spreading the disease. These factors can statistically account for gay men being more prone towards contracting HIV, leaving no reason to think that the gay gene, or any other biological factor, is making it easier for gay men to contract HIV.
Professor Chris Beyrer of the Johns Hopkins Center for Public Health & Human Rights investigated the link between gay men and HIV/AIDS in 2012. He analyzed sexual behaviors associated with gay men, and found that they can explain the higher rates of the disease in gay men. A person in the receiving role during anal sex is nearly twice as likely to contract HIV as someone in the receiving role during vaginal sex. In addition, gay men are able to switch who is in the receiving and inserting roles, which can expose both parts to this increased chance of contraction.[10] In addition, there is social stigma associated with being gay, and this makes it harder for homosexual men to seek treatment and health care that could help prevent them from spreading the disease. These factors can statistically account for gay men being more prone towards contracting HIV, leaving no reason to think that the gay gene, or any other biological factor, is making it easier for gay men to contract HIV.
References
[1] Dean Hamer and Peter Copeland, The Science of Desire: The Search for the Gay Gene and the Biology of Behavior (New York: Simon & Schuster, 1994): 223.
[2] Zoe Mintz, "Does a 'Gay Gene' Exist? New Study Says 'Xq28' May Influence Male Sexual Orientation," International Business Times, February 14, 2014. Available from: http://www.ibtimes.com/does-gay-gene-exist-new-study-says-xq28-may-influence-male-sexual-orientation-1555564 (accessed November 16, 2014).
[3] Hu Stella, "Linkage between sexual orientation and chromosome Xq28 in males but not females," in Nature Genetics 11 (1995): 248-256.
[4] Dean Hamer. Source: Born Gay Pro-Con. 2009, Digital Image. Available from: http://borngay.procon.org/view.resource.php?resourceID=004623 (accessed November 19, 2014).
[5] Dean Hamer, S Hu, VL Magnuson, N Hu, and AM Pattatucci, "A Linkage between DNA markers on the X chromosome and male sexual orientation," in Science 261 (1993): 321-327.
[6] Hamer 147.
[7] Alfred Kinsey, W. Pomeroy, C. Martin, and P. Gebhard, Sexual Behavior in the Human Female (Philadelphia: Saunders, 1953).
[8] Hamer 183.
[9] Hamer.
[10] Chris Beyrer, S.D. Baral, F. van Griensven, S.M. Goodreau, S. Chariyalertsak, A.L. Wirtz, R. Brookmeyer, "Global epidemiology of HIV infection in men who have sex with men", The Lancet 380 (2012): 367-377.
[1] Dean Hamer and Peter Copeland, The Science of Desire: The Search for the Gay Gene and the Biology of Behavior (New York: Simon & Schuster, 1994): 223.
[2] Zoe Mintz, "Does a 'Gay Gene' Exist? New Study Says 'Xq28' May Influence Male Sexual Orientation," International Business Times, February 14, 2014. Available from: http://www.ibtimes.com/does-gay-gene-exist-new-study-says-xq28-may-influence-male-sexual-orientation-1555564 (accessed November 16, 2014).
[3] Hu Stella, "Linkage between sexual orientation and chromosome Xq28 in males but not females," in Nature Genetics 11 (1995): 248-256.
[4] Dean Hamer. Source: Born Gay Pro-Con. 2009, Digital Image. Available from: http://borngay.procon.org/view.resource.php?resourceID=004623 (accessed November 19, 2014).
[5] Dean Hamer, S Hu, VL Magnuson, N Hu, and AM Pattatucci, "A Linkage between DNA markers on the X chromosome and male sexual orientation," in Science 261 (1993): 321-327.
[6] Hamer 147.
[7] Alfred Kinsey, W. Pomeroy, C. Martin, and P. Gebhard, Sexual Behavior in the Human Female (Philadelphia: Saunders, 1953).
[8] Hamer 183.
[9] Hamer.
[10] Chris Beyrer, S.D. Baral, F. van Griensven, S.M. Goodreau, S. Chariyalertsak, A.L. Wirtz, R. Brookmeyer, "Global epidemiology of HIV infection in men who have sex with men", The Lancet 380 (2012): 367-377.