Quierd Science

People have long pondered the sources of gender identity and sexuality.  We often wonder at what creates something different, a minority, and at the ways in which gender is expressed through behavior: men act manly, women act womanly, and so long as nobody departs from these norms, everyone remains comfortable.  It is the variations from the standard that intrigue us and prompt a quest for the sources of such divergences.

Homosexuality is one such variation. Only about 4% of the American population identifies as LGBTQ (Lesbian, Gay, Bisexual, Transgender, Queer), but LGBTQ issues now have become prominent socially, politically, and even scientifically.1  In recent years, a changing social and political climate has stimulated a more honest scientific examination of the sources of gender identity and orientation.

Rainbow ChromosomeResearch into sexuality still often reflects political, social, or religious biases: some conservative members of society continue to argue that sexual identity is driven almost solely by choice and mental state, while others seek to prove the biological basis of a person’s sexuality in the hope that such proof will lead to increased social acceptance – if orientation is inevitable, it may be less stigmatized.  In the 1940s and 1950s, homosexuality was considered to be a pathology rather than an orientation.  In order to “study” (or “cure”) them, gay men were lobotomized, electrically shocked, treated with aversion therapy, or castrated, while lesbians were forced to have hysterectomies and estrogen injections.  Homosexuality was classified as a mental disorder by the American Psychiatric Association until 1973, and many continue to stigmatize it as such today.2  The majority of research focuses on gay men because “in men, arousal is orientation.  It’s as simple as that,” says Professor Michael Bailey, a psychology researcher at Northwestern University.  As a result, much more evidence exists as an explanation behind variances in sexual behavior in men.3

Nonetheless, there is an abundance of legitimate research into sexuality unbiased by political or social inputs.  Two of the most prominent areas of study deal with genetics and neurophysiology.  Dr. Dean Hamer, a geneticist, suggests that sexuality is based on maternal inheritance, specifically in a region of the X-chromosome.  In 1939, he published research describing specific DNA markers on the “Xq28” region of the X-chromosome found in and shared by only homosexual men in his study.  Hamer argues for a linkage between these genetic markers and male sexual orientation.  Some scientists call this discovery the “gay gene” and, although that title may be stretching Hamer’s findings too far, his research does provide important genetic support for inherited homosexuality in men.4

Could “societal nudging” make a gay man straight?  The scientific basis of Hamer’s findings on sexuality’s genetic origins explains why modern scientific findings prevail against those more biased “researchers” who believe that sexuality can be changed.  The research of scientists William Reiner and Alfred Kinsey, who have studied the opposing influences of nature and nurture on sexuality, reinforce Hamer’s conclusions that sexuality is inherent in one’s biology.  Reiner’s studies — on a group of boys born with genital deformities who were then surgically turned into girls — show that sexual orientation is determined at birth, not through societal influences or expectations. Although the boys in his studies were “made” female and raised as women, all of them maintained an attraction to women.  Despite the manipulation of their physical sexual characteristics, they retained their innate sexual orientations.3  Sex researcher Alfred Kinsey reported similar phenomena among gay men who went through “therapy” to be converted to heterosexuality.  Dr. Kinsey found that no homosexual man was able to be pushed into a different sexual orientation (though some men were able to willfully suppress their homosexual desires).2

Biological factors other than inherited traits further support the view that sexuality is inherent in one’s biology, as more than one study has observed remarkable differences in brain structures between homosexual and heterosexual individuals.  Dr. Simon LeVay, a neuroscientist, conducted what may be the most notable of these studies.  In 1991, LeVay was studying the brain tissue of deceased gay and straight men when he discovered clear differences between them in the interstitial nuclei of their hypothalamus.  Furthermore, he found that, regardless of their own gender, people attracted to men had similar neurological differences compared to those attracted to women.2,3  LeVay’s findings not only present remarkable biological insight into human attraction, but opened up the entire field of anatomical study of sexual orientation.

Many studies followed on the heels of LeVay’s research.  Scientists have identified numerous physical and neurological attributes that might either contribute to or reflect sexual orientation, such as penis size, inner ear function, reactions to certain drugs and pheromones, blinking frequency, hair shape, and limb and finger length.  More recently, Dr. Qazi Rahman, a cognitive biologist, observed subtle differences in brain structure, size, and symmetry between homosexual and heterosexual people.  Rahman observed that regardless of gender, the right and left hemispheres of those who are attracted to men, i.e. homosexual men and heterosexual women, are significantly more symmetric than the hemispheres of people who are attracted to women, such as heterosexual men and homosexual women.  Furthermore, homosexual men have more nerve connections in their left hemispheres, while heterosexual men have more in their right hemispheres. Dr. Rahman believes that these brain differences do not come purely from childhood brain development, but rather are the result of early fetal development. Essentially, “if you are gay, you are born gay”.5

Sexual orientation is therefore as controllable as the rising and setting of the sun.  There are no objective, rigorous, replicable scientific studies that actually conclude that “choice” is a deciding or even contributing factor in determining sexual orientation.  Those who deviate from gender norms may suffer social stigma, but science is proving that that sexual orientation is not an imbalance of brain chemicals or the product of a traumatic experience.  It is something far more interesting — reflection of the endless diversity of human life as biology plays out in behavior.


  1. James, Susan D. 2011. “Gay Americans Make Up 4 Percent of Population.” ABC News. April 8.
  2. Burr, Chandler. 1997. “Homosexuality and Biology.” The Atlantic.
  3. Swidley, Neil. 2005. “What Makes People Gay?Boston Globe. August 14.
  4. Abrams, Michael. 2007. “The Real Story on Gay Genes: Homing in on the Science of Homosexuality—and Sexuality Itself.” Discover. June 5.
  5. BBC News. 2008. “Scans See ‘gay Brain Differences’“. June 16.
  6. Image credit (Creative Commons): Edwards, Aaron. 2006. “Gay Gene.” Flickr. March 17.

Riva Letchinger is a second-year student at the University of Chicago majoring in Biological Sciences.  Follow The Triple Helix Online on Twitter and join us on Facebook.