Homosexuality: The Social Impact of a Genetic Basis


For my project, I really wanted to look at how genetics, and the idea that our personality and other traits like sexual orientation are determined by genes affects our perception of them. I thought that this would be especially apparent in such a controversial issue as homosexuality, and recalled some recent studies done about its genetic basis, so chose to look more closely at this social phenomenon through that lens.



Homosexuality today is an incredibly charged topic. It lies at the center of a social battle around the world, and has been sensationalized and raised almost as a standard for inter-generational and sacred vs. secular conflict by the media. Even its definition has changed considerably in just a few short decades; when I looked for a definition in my mother's 1971 Oxford English Dictionary, there was nothing, but look on Urban Dictionary[1] , and no less than eleven definitions come up. Generally, homosexuality is defined as romantic and/or sexual attraction between people of the same gender. This includes gay, lesbian, bisexual and transgender attraction (usually abbreviated LGBT), although as our perception and knowledge of homosexuality and its causes change, our definition is almost certain to change too.


  • What's the percentage of homosexual people in America, or the world? We honestly don't know. There are multiple problems to obtaining an accurate picture of this data, not the least of which are that not everyone who identifies as homosexual has "come out" or decided to be open about their sexuality, most people consider homosexuality multi-dimensional, meaning that it's difficult to classify people in a few small categories, and discriminatory laws and public opinion keeps funding for studies like this difficult to attain
  • The largest civil rights group actively working for gay rights, the Human Rights Campaign[2] , has 750,000 members
  • According to an Australian twin study, homophobia,[3] as well as homosexuality, has a roughly 36% genetic basis in addition to the environmental and situational factors that also exacerbate it


For an example of current legal discrimination against homosexuals, I looked just at laws in my own state of Ohio.[4] Here are some of the ways that state legislature discriminates against homosexuals:
  • homosexual marriages are not recognized, and there is no alternative (like a domestic partnership) that allows any more rights than if they were unmarried
  • same-sex spouses cannot make decisions about their partner's health care if that partner is unable to make or communicate a decision
  • courts in Ohio have used gender identity and sexual orientation to deny child visitation rights to same-sex spouses
  • Ohio has no laws against hate crimes, workplace discrimination, or mandates for school education on same-sex education
  • same-sex couples cannot petition to jointly adopt a child, and cannot adopt a partner's child without ending the parent's rights to the child

My Connection

It's hard not to be moved by just the legislation I listed above from the Human Rights Campaign--and that's only one moderate state in a country that's fairly friendly toward homosexual rights. In other countries, especially ones with strong religious presences like Iran[5] and Uganda[6] , homosexuals are ostracized, tortured, or killed upon outing. My interest in gay rights activism started my freshman year, when I participated for the first time in Speech and Debate, doing an event called Oratorical Interpretation, in which you perform a ten-minute speech previously given by its author. My coach suggested I do Keith Olbermann's Response to Proposition Eight , and I fell in love with it. More importantly than my relationship to this speech, however, was the level of awareness it gave me. I started to actually look around and see instances of discrimination in my own life, even things as simple as a friend yelling "that's so gay!" in the school hallway. This year, I got active in my school's GSA, and will be co-vice president of it next year. I really think that this breach of human rights is something that affects all of us--look how many people we look up to, like Oscar Wilde, Elton John, Harvey Milk, and so many more, people that impact our lives, are gay, and have to, or had to, deal with this reality on a regular basis.

Then something else happened that really got me thinking about the genetic aspect of homosexuality. Just this year, two of my best friends came out as lesbian and bisexual, respectively. In a long, late-night discussion with one of them, the issue of heritability came up. She couldn't figure out where it had come from, with her. She had no relatives that she knew of who were gay, and she was the oldest child of her family, so she had no idea about her siblings. I had heard of some studies about how much of homosexuality was caused by environmental factors and how much was genetic, so the question was in the back of my mind all throughout this course. Not so much the idea of whether or not homosexuality was caused by genetic or environmental factors, but the idea that the first place her mind jumped to was wondering what was physically different. It's a completely logical conclusion: sexual attraction is physical, so the causes should be physical, right? And in another conversation, she mentioned that she "wish[es] people would understand that it is physical. Then maybe relatives would stop looking disapprovingly at me and telling me that I'll 'get over it when I grow up.'" It was really this idea that stuck with me, and made me wonder how genetics changes society's opinion of traits like homosexuality.

History of LGBT Research

Research into the causes and expression of homosexuality has been constantly adapting with humanity since the rise of our species. Over time, research methods have changed with technology and hypotheses have changed. With them, societal attitudes have changed, and will continue to change as research continues.

Before scientific investigation

Ancient history is rather quiet on the subject of homosexuality: we know that some civilizations like the Hebrews (as reflected in the Old Testament of the Judeo-Christian Bible) were very anti-gay, whereas others, like Sumeria (as reflected in the platonic homosexual relationship in The Epic of Gilgamesh) were more accepting. Some places, like the city-states of ancient Greece (especially Sparta), have been the subject of much scholarly debate about the origins of homosexual practices, positing the theory that these were popular and accepted simply because they were a fashion among the upper classes.[7] However, as Judeo-Christian tradition began to dominate cultural identity throughout Europe and the Middle East, homophobia came with it. Homosexuality took on the mantle of a "sin" or even in some cases a demonic possession.[8]

Throughout these histories, especially in religious works and in the beliefs of American Indians, is the idea of the gender of one's soul. For most of history, the primary theory of the existence of homosexuality is that some people are born with the soul of a different gender than they express physically. This has been used to explain various personality characteristics, relationships, and sexual orientation.[9] [10]

Pseudoscience and Nazism

Homophobia and discrimination against LGBT people reached one of its great heights during the genocide of the Nazi regime. The Nazi theory of homosexuality was that it was something like a disease, that could be spread through seduction and homosexual sexual contact. Hitler's government considered homosexuals a threat to the masculinity of the Aryan population they were trying to create, and so made homosexuality punishable by law. This allowed them to imprison many, kill many more in concentration camps, institutionalize them in mental hospitals, and physically and chemically castrate more.[11]

Many of the experiments done on homosexuals were done to propagate the widely-held theory that homosexual men were not as physically strong or resilient as straight men. Experiments working with things like body temperature were done to prove this, like one homosexual man who was cooled in an ice vat until unconscious, then subject to heat lamps so hot they would burn skin. This process was repeated multiple times until he died. Extensive experimentation with twins also went on in this time, trying to find the causes of various diseases, as well as possibly sexuality.[12]

This shows that the Nazis were beginning to believe that homosexuality had physical causes, not just psychological or metaphysical ones. This idea persisted, even though the Nazi's ideas and practices were reviled.

American Psychiatric Association

One of the major turning points leading to the way we see homosexuality today was the American Psychiatric Association naming homosexuality as a mental disease in the 1800s. This suddenly changed societal perceptions of homosexuality for better and for worse: for better, it was no longer seen as a sin or some other metaphysical problem, but for worse, being classified as having a mental illness prevented the LGBT community from getting jobs, getting health coverage, and being accepted as normal, functioning members of society.

After a long battle waged from within the APA itself, including secret societies, hijacking symposiums, and other dramatic moves, the APA finally changed its official definition of "sexual deviance" to make homosexuality no longer a mental illness. However, this left the definition open again, inviting further research that is still very fluid today.[13]

For a really great account of this struggle, an episode of NPR's This American Life is available online here. To listen, click "stream episode."
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Methods of Ongoing Research

Research conducted currently on the definition and causes of homosexuality are especially interesting considering the societal shift when the APA redefined their idea of homosexuality.

Twin Studies

Twin studies are studies of twins to pinpoint the causes and different presentations of various disorders. There are a few different types of twin studies, all which study slightly different things:
  • Classical twin study: the same test is administered to identical twins presenting a trait and fraternal twins presenting the same trait. If the responses to the test are different between the sets of twins, then researchers can determine how much of the trait is determined by genetic factors and how much is environmental.
  • Co-twin method: with a pair of identical twins where one shows a trait and the other doesn't, researchers can use both of the identical twins to determine what environmental factor causes the trait.
  • Molecular analysis: with fraternal twins, scientists can use molecular analysis of sections of DNA that differs between the twins to find the specific genes that cause disorders
  • Virtual twin method: researchers can look at 'virtual twins,' which are children of the same age but of no biological relationship raised in the same home and environment.[14]
Twins studies have recently been used in some of the most high-profile studies of sexuality all over the world.

Other methods

Some other studies have also recently been done on the physiology of homosexual men and women to look at apparent differences between them.
  • Fingertip ridges: a study of the number of fingertip ridges on the hands of homo- and heterosexual men show that 30% of homosexual men have significantly more ridges on their left hands than on their right hands, whereas only 14% of heterosexual men display the same ratio. This shows that homosexuality might be environmental, caused by differences in the mother's uterus during gestation, because fingerprints are determined in the uterus.[15]
  • Finger length: finger length is another trait determined by environmental factors that differs between homo- and heterosexual men and women. Studies from samples taken at street fairs in California show that lesbian women have shorter index fingers as compared to ring fingers, which indicates that they were exposed to higher levels of androgens--male hormones-- while in the mother's uterus. However, this study also showed that homosexual males displayed the same ratio, indicating that they were also exposed to more androgens than usual during fetal development. This indicates that rather than being closer to feminine, as cultural stereotypes suggest, gay men are rather "hypermasculinized."[16] This could have significant implications for large families with many older brothers, as androgen collects in the womb with each successive male birth.[17]
  • Eye blinking: studies of the propensity to blink upon being startled showed that homosexual men have a response closer to that of heterosexual women, and homosexual women have a response closer to that of heterosexual men. This is very important because this is not a learned trait, and is in a part of the brain that does not respond much to environmental stimuli, so this suggests that there is a neurological difference between homosexual people and heterosexual people.
  • Pheromone response: after baseline testing to show that male and female brains process scent the same way, researchers exposed a sample of different sexualities (homosexual men and women and heterosexual men and women) to pheromones derived from testosterone and estrogen. This showed that homosexual men and heterosexual women responded to testosterone, and homosexual women and heterosexual men responded to estrogen. This shows more evidence that homosexuality is a "hardwired" instinct that cannot be learned.

Current Findings

Genetic vs. Environmental factors

Although we still don't entirely know what causes homosexuality, several scientists appear to have found patches of genes that contribute. One of these, Dean Hamer, did an extensive study of gay brothers and found that homosexuality seemed to be inherited through the mother, which led them to pinpoint a swath of DNA on the X chromosome of gay men that might have something to do with it. Although other studies refuted this claim, Dr. Hamer rejected those studies because they did not focus on the entire X chromosome, but rather on discreet patches. The idea that this gene is carried on the X chromosome through the maternal line is especially important from an evolutionary standpoint, because it allows the gene to survive through multiple generations without dying out, as homosexuals are far less likely to have biological children.

Recent findings have also led scientists to believe that environmental factors like societal expectations have less to do with sexuality than previously believed. For example, a team of scientists studied a group of males who had been born with genital defects, surgically given female genitalia (because that was easier than fixing what genitalia they were born with), and then brought up unaware of the conditions of their birth. Later in life, all of these individuals were attracted to women, showing that even though they were raised in a mostly heterosexual society, and perhaps slightly pressured to be attracted to men, these environmental factors could not overcome preexisting factors that were already in place before the surgical shift. One of the most conclusive pieces of evidence for the genetic basis of homosexuality was a very famous twin study which showed that if one identical twin was gay, the other twin had a 50% chance of being gay also, which indicates a very strong genetic bent for this trait.

However, most interestingly, a new theory has arisen for why these genetic factors do not control with 100% accuracy an individual's sexual orientation: the methylation of genes. This is the system that turns genes from one parent off, although there is evidence rising now that they do not turn completely off, but still play roles in how the body functions. Methylation is passed from parent to offspring, but it is mostly controlled by environmental factors, which elegantly combines the environmental and genetic basis for homosexuality.

This is still being studied using tests that look for genetic markers near where there might be a gene for homosexuality. Researchers using this method compare data from related gay and straight men (brothers), and look for differences.

Potential caveats

No matter how exciting these findings may be, there are, as always in scientific research, some caveats.
  • In all probability, there is no one gene that controls sexual orientation. Rather, it is probably a collection of genes (between 5 and 15[18] ) controlling things like hormone production, personality, etc., that all combine to make up one's sexual orientation. This renders the media's portrayal of "the gay gene" as inaccurate and potentially even harmful to public understanding of sexuality.[19]
  • Even if there is a set of genes that lead to homosexuality, environmental factors, especially during development, also have something to do with sexuality

Implications of Recent Research

Evolutionary benefits

One of the first steps toward gaining widespread acceptance of homosexuality is to establish a reason for its evolution, to eliminate the idea that homosexuals are "mutants" in the harmful sense of the word--aberrations that have a negative impact on society, rather than a positive one.

Some scientists are beginning to form theories of how homosexuality could be helpful to a society, especially the small hunter-gatherer societies from which humans evolved. First of all, homosexuality decreases competition among men for females, and can even out the competition for mates in a group that has an excess of males. This eliminates much of the most serious competition between males, fostering harmonious group dynamics that allow a small group to work easily together.[20]

Also, having a homosexual relative in a small family group situation like this would also be an advantage to any children (like the grandmother hypothesis--that we began nurturing our aging relatives because they could take care of our kids). Homosexual relatives without children of their own were available to tutor, support, and take care of children of their straight relatives. This way, they could also pass down learned character traits, even though they were not passing down genetic ones.[21]

Also, a new theory has come forward that the genetic traits that make men gay are likely to make women "superfertile," thus having more children, which would be a benefit for small family groups, and would tie in with the idea that homosexuals are evolutionarily useful because they are caregivers. This suggests that the two traits coexist, and perhaps evolved together: women with more children needed caretakers with no children of their own, or homosexual men needed siblings to have more children to offset the fact that they had none.[22]

Current Discrimination

Perhaps the most harmful misconception about homosexuality is that it is a choice--this dates back to religious intolerance of homosexuality when it was still seen as a "demonic possession." This makes research that proves homosexuality is a physical characteristic that cannot be avoided so much more crucial. If people understand that homosexuality is just like any other genetic trait, and has a reason for existence, then maybe they will be more tolerant.

This philosophy can also be extended to more genetic traits that are currently being discovered, hence the need for more genetic non-discrimination acts and laws that need to be put into effect to prevent workplace and healthcare discrimination on the basis of genetic traits, homosexuality included.

Where to next?

Ending social stigma

There still remains much work to be done to end the social stigma surrounding the homosexual community. First, findings like these need to be publicized, and accepted into the collective social mindframe. In this case, science might not help us as a global society to see things more clearly for a long time, but in the meantime, what evidence we do have must be used to the fullest of its potential to help alleviate this discrimination. This also means that the focus of our viewpoints on sexuality and sexual orientation must change from looking at the lifestyles LGBT people lead to what homosexuality really means, and what causes it. This is why the genetic basis for homosexuality is so important: it elevates homosexuality from the realm of a deviant personal choice to a genetic trait that no one can "help," just like any of the harmless traits we all possess that make us different, but at the same time, make us human.

Secondly, one of the most important things to be done is to make it socially acceptable to study and talk about homosexuality. In our society, too often anything mentioning sex is shot down as "obscene" by conservative and evangelical interests approving government funding through government-controlled organizations like the National Institute of Health. This stifles many opportunities for research on anything pertaining to human sexuality, let alone to homosexuality, which is still considered "an abomination" by much of evangelical America.[23]

Opportunities for further research

Much research has yet to be done on exactly what environmental triggers cause homosexuality, how much of it is genetic, what genetic factors cause it, and other ways that homosexuality and its causes affect health, both physical, and mental. Researchers looking for the set of "gay genes" expected to have an answer by 2008, but that has obviously come and passed and there is no conclusive answer yet. Research in the future depends on getting funding, which is still difficult with the current economic and political climate.

What you can do

If you're interested in getting involved, I've included a few links to sites that do really great work and have links to volunteer and awareness opportunities in your area:

The Gay Rights page on Change.org is a really good newssite for current and historical issues on LGBT rights covering a really broad range of topics from international discrimination to gay pride rallies here.

The Human Rights Campaign is the largest pro-LGBT organization in the US, and has helpful links to things like volunteer opportunities and state laws.

GLSEN, the Gay, Lesbian, Straight Education Network, is the foremost organization working toward safe schools for LGBT students. This is usually the organization that runs local GSAs, which you can get involved in at your school, if your school has one, or at other local community organizations.
  1. ^ http://www.urbandictionary.com/define.php?term=homosexuality
  2. ^ http://www.hrc.org/about_us/who_we_are.asp
  3. ^ The fear of homosexual people

  4. ^ http://www.hrc.org/laws_and_elections/state.asp?state=Ohio&btnG.x=11&btnG.y=8
  5. ^ http://gayrights.change.org/blog/view/will_the_united_kingdom_let_iran_torture_and_kill_kiana_firouzType
  6. ^ http://gayrights.change.org/blog/view/missionaries_of_hate_details_harms_of_ugandan_bill
  7. ^ http://www.fordham.edu/halsall/pwh/index-anc.html
  8. ^ http://gayrights.change.org/blog/view/homosexuality_is_not_a_disease_and_other_lessons_from_the_american_psychiatric_ass
  9. ^ http://www.fordham.edu/halsall/pwh/index-med.html
  10. ^ http://www.fordham.edu/halsall/pwh/index-am.html
  11. ^ http://www.ushmm.org/museum/exhibit/online/hsx/
  12. ^ http://www.remember.org/educate/medexp.html
  13. ^ http://gayrights.change.org/blog/view/homosexuality_is_not_a_disease_and_other_lessons_from_the_american_psychiatric_association
  14. ^ http://discovermagazine.com/2004/aug/study-the-clones-first/?searchterm=twin%20studies
  15. ^ http://www.religioustolerance.org/hom_caus4.htm

  16. ^ http://archives.cnn.com/2000/HEALTH/03/29/gay.fingers/

  17. ^ http://discovermagazine.com/2006/sep/gaybrothers/?searchterm=sex%20studies

  18. ^ http://discovermagazine.com/2007/jun/born-gay/article_view?searchterm=twin%20studies&b_start:int=1

  19. ^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1716443/pdf/ajhg00421-0084.pdf
  20. ^ http://www.ncbi.nlm.nih.gov/pubmed/15376406?ordinalpos=1&itool=PPMCLayout.PPMCAppController.PPMCArticlePage.PPMCPubmedRA&linkpos=5
  21. ^ http://gayrights.change.org/blog/view/gay_folks_are_the_key_to_evolutionary_survival
  22. ^ http://discovermagazine.com/2007/jun/born-gay/article_view?searchterm=twin%20studies&b_start:int=1
  23. ^ http://discovermagazine.com/1992/jun/whydoweknowsolit64/?searchterm=sex%20studies