The Fascinating Science of Gay

“I wish I knew, I wish I knew

What makes me me, what makes you you”

--- Cat Stevens, I Wish I Wish

The question of whether being gay is a choice has been batted around a lot lately but there’ are quite a lot of studies showing a biological bases for sexual orientation. What sex you tend to fall for doesn’t appear to be any more of a choice than what individual you fall for….and jinkies, if we could chose that we’d save an awful lot on divorce lawyers (but then again, we’d have no songs like “I’ve got tears in my ears from lying on my back in my bed while I cry over you,” which almost makes lousy love affairs worth the Sturm und Drang).

At any rate, here area few reasons to think Lady Gaga just might be on to something.

Size matters

In 1991 Harvard neuroscientist Simon LaVey wrote a paper explaining an intriguing finding concerning the hypothalamus, a tiny structure in the limbic system, in lower middle of the brain (if you compare a side view of the brain to a map of the U.S. the hypothalamus is around the Texas panhandle). It’s an area with lots of important functions, like regulating homeostasis - body temperature, our endocrine and pituitary systems, circadian rhythms, plus sexual function and emotion, juicy and important stuff. LaVey found that in the anterior hypothalamus, which regulates male sexual behavior, one of the cell groups, INAH 3, was twice as big in heterosexual men as in heterosexual women - and more than twice as large in heterosexual men as in homosexual men.

LaVey’s study was criticized for the use of cadaver tissue from AIDS patients because some people thought if the disease effected the brain that might be the cause of the variation - but six of the “presumed” straight male subjects also died of AIDS. In a 2011 Salon interview with Schuyler Velasco, upon the publication of LaVey’s book Gay, Straight and the Reason Why, LaVey describes a study of the brains of “completely healthy” gay male sheep who showed the same wee hypothalamus as the gay male human subjects did. 

Chances Are

Also in 1991 - evidently a big year for this kind of thing - the New York Times reported a study by Dr. J. Michael Bailey of Northwestern University of twin, fraternal and genetically unrelated (adopted) brothers found that in 52% of cases if one brother was gay the other would be, too, as opposed to only 22% of fraternal twins who have the same genetic similarities as non-twin siblings. There was only an 11% chance in adopted brothers. 

Gene Genies

The “gay gene” meme was introduced to the public in 1993 when Dr. Dean Hamer, - who we’ll phone chat with later in this story - then of the National Cancer Institute concluded in a study  that since there appeared to be “more gay male relatives on the mother’s side of the family than would be expected by chance alone,” as the Chicago Tribune’s John Crewdson put it in 1995, and that homosexuality must be passed on by the mother and so studied the X chromosome, which determines gender and is passed down only by mom. The team studied 40 families with at least two gay brothers and found, “a correlation between homosexual orientation and the inheritance of polymorphic markers on the X chromosome in approximately 64 percent of the sib-pairs tested,” reads the study abstract. The markers appeared on a region of the  Xq28 chromosome and while it was not a single “gay gene” the notion took off in the popular imagination. Hamer himself would say, Frontline reports, that  “Rarely before have so many reacted so loudly to so little.”

The study came under scrutiny - Michael Abrams’ excellent story  in Discover magazine details the controversy and many aspects of research into the genetics of homosexuality - but the research has continued and in 2005 a team includingHamer and Dr.. Brian Mustanski and Sven Bocklandt of the University of Illinois took it a step further. They looked at the entire chromosome whereas previous research had focused on the X chromosome passed down by the mother - the 2005 study looked at all the chromosomes.

Dr. Mustanski must be a really good teacher because listen to how he explained the difference in the methods of study: 

“Mustanski compares the study's approach to a search for doctors in a town of 40,000 people, a number that roughly corresponds to the number of human genes.

Rather than guessing that doctors live in a particular type of house and going to only the houses that meet that criteria, researchers in this scenario would knock on every door to ask the residents if a doctor lives on their street. Using a similar approach, researchers were able to locate a few potential genetic neighborhoods that likely contribute to male sexual orientation.”

The genes they were analyzing were from “456 men from 146 families with two or more gay brothers.”  The results showed common genetic patterns on 60% of the men on three chromosomes - 7, 8 & 10 - whereas in a random sample only 50% would be expected. So it’s slightly more than random. 

Getting sniffy, Part One

Body odors are important in romance and not just because the commercials for products meant to hide them tell you they are. It’s  because the scent of our individual chemistries is thought to give us a lot of subtle information about who is good genetic match for us. 

It’s not genetics but there are some studies that show differences in the biological arena of body odors between gay and straight men and women.  In 2005 s Charles Wysocki and Yolanda Martins of the non-profit Monell Chemical Senses Center did a study on how people of different sexual orientations - lesbians and gay men and straight men and women - perceive body odors and how their odors were perceived by other groups. Gay men proved to pretty much stand alone in this study: they preferred body odors from other gay men to all the other groups, though they also liked the odors of straight women (maybe they were just being polite). In turn, all the other groups preferred the body odors of gay men the least. 

Just relaying that last bit makes me feel bad, since so many of the gay men I know mostly smell like exotic flowers that grow only in the cologne department at Macy’s. But one imagines a lab setting might disallow for some things.

Sniffy, Part Two

Going back up to the hypothalamus, also in 2005  New Scientit’s Jennifer Viegas reported that researchers at Sweden’s Karolinska institute found differences in the way straight women and men and gay men responded to chemicals derived from sex hormones. 

When presented with scents like cedar and lavender oils the parts of the brain linked to regular old olfactory response lit up in PET and MRI scans in all subjects. When, however, a chemical derived from testosterone found in male sweat - AND - and a derivative of estrogen found in female urine - EST was introduced to the sniffers other areas perked up. “AND excited the brain areas associated with sexual behaviour for female and gay male participants, as did the EST for straight men,” Viegas writes. Again the blabbermouth hypothalamus gave the game away in straight women and gay men: “The AND activated the anterior hypothalamus and medial preoptic area of gay men and women,” Viegas writes.  

So when is Yankee Candle going to come up with “Morning Tesosterone”? Cuz I think I’d like that. 

Getting sniffy, final installment

Building on that research another study in 2006 concluded that lesbians responded differently than straight women when exposed to those chemical derivatives of “suspected” sexual chemicals in male sweat - AND  and EST - writes John Roach of  National Geographic. Gay men responded similarly to straight men when processing the odors. To add to the intrigue, Roach writes :”Savic- added that the similarity between homosexual men and heterosexual women seems stronger than the similarity between lesbians and heterosexual men, highlighting the notion that male homosexuality is quite different than female homosexuality.”

So, even if one figures out where sexual orientation may reside biologically there will still likely be differences there’s still how these differences express themselves; it’s still wonderfully complicated.

Savic-Berglund “cautioned that neither study proves people are born gay. The response could be biological or learned,” and also that the research group was hesitant to call the compounds “pheromones,” which have a sci-pop-cultural cache as being the chemical scent of sexual attraction. Charles Wysocki, who we met earlier, was dismissive of the idea of AND and EST “pheromones,” and said the results been obtained actual body odor rather than derivatives would have been “phenomenal,” but found the research nonetheless intriguing.

X Marks the Spot

A UCLA study from 2006 lead by Sven Bocklandt  also found that moms’ genetic contributions may also have some influence over her son’s sexuality through “X chromosome inactivation,” reports Ker Than of LiveScience. Everyone has 23 pairs of chromosomes which contain our genetic code. Women have two X sex chromosomes while men have one X and one Y.  Genetic expression is controlled by  methylation, a process which works  by turning some genes off.  Half a woman’s cells will have one activated X and the other half will have another. One X being left on can result in an overabundance of protein and, Than writes, “Down syndrome, for example, results from the presence of an extra copy of chromosome 21.”

The turning off of half of those X’s is normally random but the UCLA study looking at mothers who had two or more gay sons found that a quarter of them had inactivated the same X chromosome in every cell the researchers looked at. Mothers of one gay son showed “In contrast, only 4 percent of mothers with no gay sons and 13 percent of those with just one gay son showed this type of extreme skewing,” Than writes.


In December 2012, Science Daily reports, researchers have found yet another clue in epigenetics, changes in gene function, though not necessarily in gene sequence. It’s not about the gene itself but how the gene expresses itself. The X chromosome inactivation we just talked about is an example of an epigenetic system.

Then there are epi-marks, (which are not made with EpiPens); they are temporary switches that control a gene’s expression. The gene holds the instructions - the epimark decides how the instructions are carried out “when, where and how much a gene is expressed during development,” SD writes. Sex-specific epi-marks protect the fetus during early development from bigger hormonal shifts that happen in later development, i.e., if the testosterone tide rises down the line they keep a girl from becoming masculinzed and boys from being feminized. They effect different areas, like genitals, sexual partner preference and gender identiy. Epi-marks aren’t typically transmitted generationally - they are just erased. But, according to a study from the Working Group on Intragenomic Conflict at National Institute for Mathematical and Biological Synthesis (NIMBioS) (seriously - their business cards are a foot long), on the occasions when they are transmitted from father to daughter or mother to son “they may cause reversed effects, such as the feminization of some traits in sons, such as sexual preference, and similarly a partial masculinization of daughters.”

Elizabeth Norton from Science Now explains the hormonal influence that may effect the epi-marks “homosexuality may be a carry-over from one's parents' own prenatal resistance to the hormones of the opposite sex.” For example if the parent had epi-marks that signaled the genes to resist higher testosterone levels those epi-marks could “alter gene activation in areas of the child's brain involved in sexual attraction and preference.”  

The Science of the Lambs

Fascinating, right? So you know there had to be a pea under the mattress.

While ISO all these cool stories and studies I found a 2008 Slate story by William Saletan Sexual Reorientation: The Gay Culture War is About to Turn Chemical that introduced me to the idea that “the closer we are to understanding these biological factors the closer we are to being able to change them.” Among many other things, Saletan writes about sheep researchers who attempted to “alter hormonal inputs in pregnant ewes,” and thus effect the sexual orientation of the lambs (it didn’t work and a very interesting follow-up piece explained the whole endeavor much more thoroughly). Saletan also noted two people  - both Reverends - who supported the idea of controlling sexual orientation should the possibility ever arise. 

“Dare to be naive,” Buckminster Fuller said and I guess I’m more daring than I thought because this kind of thinking never even occurred to me. Could this research, which I had seen as so positive, have some surprise negatives?

“It’s not really about the research it’s about the values of our society,” said Silvia M. Dutchevici, MA, LCSW, President and Founder of the Critical Therapy Center in a phone interview. “It’s such a good example of how research itself is interesting and we should be able to look at it and say “Oh, that’s amazing!” but it becomes tied with political issues, with heteronormativity,” because research doesn’t exist in a vacuum but is processed through the lens of our values. Such research could be used in a negative way because our society accepts homosexuality but not 100%, Dutchevici says, but it could also make people put limits on themselves. If we know we have a “gay” or “straight” brain, she wonders if  “we (will) express the sexuality we think we should express rather than how we want to express it.” 

Dr. Kathleen Farrell, a therapist in Tampa who works with transgender people said her concern isn’t that being transgender would show up in the brain…but that it wouldn’t. What if, in some hypothetical future, you identify as transgender but a brain scan says you’re not? Would that cause a transgender patient to be refused surgery or hormonal therapy? 

And she’s that how we identify doesn’t always show up biologically -  Dutchevici also noted that what might show up in our brain “doesn’t necessarily translate to sexual practices. A  2003 study by Northwestern’s J. Michael Bailey, (from that earlier twins study) about how people responded to pornography the gay men responded to men, the straight men to women. The women, gay and straight, responded to everything. This shows that a) women’s sexuality is evidently pretty fluid, b) how you identify and what you respond to might be different and c) Northwestern sounds like a fun place to work. 

“It’s a mixed bag,” Dr. Farrell says. She sees upside to biological evidence for sexual orientation in that it could make it easier for people to explain their sexuality to their families or friends. But when we talk about the misuse of research she wonders “Will there never be any more gay and lesbian people because parents chose not to have them?” 

In a phone interview I asked Dr. Dean Hamer, whose discovery of the “gay gene” caused such a stir in the early 90’s, if it was alarmist to worry about such things. 

“Well, it’s a little more nuanced than that,” he said, though he agreed that it’s right to be alarmed by the idea of tampering with nature and  says he insisted on adding a paragraph to his 1993 paper addressing the issue (which you can read here).  Hamer told his editors at Science, who worried that he was editorializing “You can’t separate the science from the reality we live in and it’s very important to put that.” Doctors and scientists, he says, should be alert about the misuse of such research. 

“Having said all that the reality is that it’s not really a deep or serious concern for several reasons. The first is that what we know about sexual orientation is it’s certainly genetically influenced but there’s no single master key so from a practical point of view there’s no way to do it,” no one main switch to change or predict sexual orientation - it’s far more complex than that. And even if it could be altered it would be hard to predict what would happen. Hamer compares the idea to what happened with “the Prozac gene”  a single gene (the serotonin transporter-linked polymorphic region 5-HTTLPR)  that controls the molecule that’s effected by Prozac and other antidepressants. 

“We said “Oh, people might think we should change it so people would be happier,” but, Hamer says, it turns out that altering that lowers people’s libidos (a famous side effect of antidepressants). 

And that wouldn’t make people very happy at all. 

Early on, Hamer says, there was a fear in the LGBT community that research into the biology of sexual orientation would “medicalize” sexuality, “that it was going to make it into a disease that would be treated,” but now, 20 years later one of the results of that research is that attitudes towards homosexuality have relaxed. Research has shown that more people believe sexual orientation is not a choice. Hamer thinks that shift is among a “vastmiddle ground of people who have been influenced by what what we’ve learned and what they’ve been hearing, amongst many other factors.”

I never thought I’d get a laugh out of all this but Dr. Hamer offers yet another scenario I never thought of: he is against tinkering of any sort but if it were possible, he asks, who’s to say that the ones to use it wouldn’t be gay and lesbian couples, who are on the forefront of reproductive technology (they don’t usually have kids the old-school way) and might want gay kids?

There’s nothing quite like a good “Gotcha!!” is there?

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