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Science: Genetics cannot explain sexual behavior

Data from half a million people refute the dogma of behavioral genetics

In the last few decades the idea seems to have gained acceptance that sexual orientation is innate, whether it is heterosexual, bisexual, homosexual or whatever sexuality is involved. In case of doubt, you just have to discover your correct identity. But how do we actually know that?

With my psychology students, who are admittedly not representative of the general population, informal surveys over the years have repeatedly shown this picture: The personality as a whole is essentially not innate, but rather acquired. But when I asked specifically about sexual orientation, the answer was reversed, then the genetic influence was considered to be about two to three times as strong as the environmental influence.

The myth of the "gay gene"

The American Science, which published a relevant study on the subject in today's issue, has played a rather inglorious role on this subject in the past. In 1993 she published the study by Dean Hamer and colleagues at the US National Institutes of Heath, who genetically examined 40 pairs of homosexual brothers. The researchers were careful not to call their preliminary findings a “gay gene”.

But even the comment co-published by the Science editorial team already spoke in the title of "evidence of a homosexuality gene." The fact that it was a gene on the X chromosome naturally fueled the stereotype that gay men are somehow more feminine. It is easy to imagine how the media picked up on the find.

The media life of the "gay boy"

This has been systematically researched by media researcher Kate O’Riordan from the UK University of Sussex. In her publication on “The Life of Gays” she traces how the hypothetical find became a social reality. Hardly anyone was interested in the fact that the genetic result could not be replicated in the following years. The idea was and is firmly anchored in people's minds.

Oddly enough, even the gay movement itself willingly picked up on the idea. There were activist T-shirts with the inscription Xq28, as the place in question was called on the X chromosome. The name also appeared in song lyrics. The idea that the gene determines sexual orientation had the potential for liberation, even if it was scientifically incorrect. Because what is biologically determined cannot be changed by those affected. Or?

O’Riordan himself suspects that the human genome project and the hype about genetics made the thought that this or that was innate, genetically determined. So why not sexual orientation as well? The researcher shows, however, that homosexuality has repeatedly been related to illnesses as a result. So the discoverers of Xq28 were actually cancer researchers.

In addition, the question of sexual orientation has been shifted from the socio-political to the biomedical area. Sociologists call this “decontextualization” and “depoliticization”. Facts are presented as given and unchangeable. We don't need to talk about that anymore. That `s how it is.

Half a million test subjects

Now we are 26 years further. The study published today is not based on the data of 40 pairs of brothers, as in 1993, but on - you have to let that melt on your tongue - believe it or not, 492,678 people. These come mainly from the British UK biobank and from the American company 23andMe, which offers all kinds of genetic tests at face value.

With today's approach, not only a chromosome or a gene is examined, but the entire genome is scanned according to statistical relationships. This is called the “genome-wide association study” (GWAS). However, the medical home of research has not changed: In the long list of authors we are dealing with psychiatrists, epidemiologists and other representatives from the health sciences.

You need ever larger groups of test subjects

Since behavioral genetics failed to deliver on its full-bodied promises of the past few decades, the lament of group size was sung for many years. Human character traits and behaviors, as well as disorders and diseases, are so complex that tens or even hundreds of thousands of test persons are needed to examine the interactions of many different genes.

On the one hand this is wishful thinking, on the other hand it is an oath of revelation: if the genetic effects were of great importance, they would also have to be found in smaller groups. That's just math. And the social sciences usually get by with a few hundred test subjects and thus find statistically robust results; provided, of course, that the rest of the scientific methodology is correct. We have known for a long time that this is unfortunately not always the case and that researchers from all disciplines sometimes simply publish in order to survive.

With the GWAS method, genetics can in any case be scaled on an industrial scale and consequently more and more “risk genes” are found. There are more than a thousand for schizophrenia alone. So far, nobody knows what the patient will bring. At least the finds fill the scientific journals. And the show must go on. We already know in advance that the results obtained in this way cannot be of great importance for reasons of principle.

New study in Science

What Andrea Ganna from the Center for Genetic Medicine at Massachusetts General Hospital in Boston and colleagues in Today's Science report is, to put it mildly, extremely humble. The whole effort with the half a million test persons has now led to the fact that five locations spread across the genome have been found that could have something to do with sexual orientation.

Let's call the stars of today's performance by name: rs11114975-12q21.31 and rs10261857-7q31.2 for both women and men. In men, rs28371400-15q21.3 and rs34730029-11q12.1 were also found. And for women rs13135637-4p14. All right, right? Incidentally, data from trans or intersex people were excluded from the analysis. The researchers do not reveal why. Perhaps the results were then no longer statistically significant?

I am sorry to have to bore my readers once again with the subject of “effect sizes”. In order to understand what the study is saying, we cannot avoid it. But first we have to know how sexual orientation was measured here - in technical terms: operationalized.

Same sex sex

The lowest common denominator for all data was whether a person had ever had sexual intercourse with another person of the same sex. So at least one time. There is nothing wrong with that and the researchers are communicating this very clearly.

In terms of sexual orientation, one can distinguish at least the following three levels: (1) with whom someone, to put it casually, goes to bed; (2) what gender someone is (primarily) attracted to; and (3) whether someone expresses their sexual preference as part of their identity and, if so, how.

Homosexuality as identity

At (3), for example, I am thinking of the annual Amsterdam Gay Pride. I went to such a parade once and saw countless muscular men (but also women) in bathing trunks celebrating their bodies and community on the colorfully decorated boats that were in no way inferior to the Cologne Carnival.

Personally, that's not my taste. But I think it's good that it exists. After all the oppression, lesbian, gay, bisexual and however oriented people want to show with pride that they are there too, that there are many and that they take their place in society.

The important point for our topic is now: Not everyone who is attracted to people of the same sex and / or goes to bed with them has to see this as an essential part of their identity. So psychologically and culturally they are different things. For example, I could find men sexually attractive, but still see the identity that some gays live out in public as “not my cup of tea”.

Useful sexual intercourse

But it is also conceivable that someone who does not find people of a certain gender sexually attractive still has sexual intercourse with such people. As we have known from clinical psychology for decades, sexuality, as well as work, eating, consumption of luxury foods or drugs, games, sport and much more can be a coping strategy for how we get through life (book tip: “Going other ways: Understanding patterns of life and change ”by Jacob, van Genderen and Seebauer). Or someone simply has no people of the opposite sex in the area, but still wants sexual contact, let's think of the army, prisons or monastery communities.

Consequently, the authors of the new study do not speak of homo- or bisexuality. It will be interesting to see if the media reporting on it will stick to it. The publication only mentions “heterosexual” versus “non-heterosexual”.

The latter, however, seems a bit artificial when it comes to people who may have only had one single same-sex contact in their life. Can you never call yourself a vegetarian again just because you once had meat on your plate? Somehow, however, the researchers have to name the phenomenon they are investigating.

To the effect sizes

With this prior knowledge, we can now deal with the data in more detail. Now it is the case that for the aforementioned gene locus rs347…, which was only statistically significantly related to sexual behavior in men, non-heterosexual behavior occurred 0.4 percent more frequently if a certain genetic trait was present.

Or let's put it another way: Those who have the genotype TT (i.e. twice the base thymine) stated in 3.6 percent of the cases that they had had at least one non-heterosexual contact. With the genotype GT (guanine / thymine) it was 4.0 percent.

With my intuition as a researcher, I now assume that the authors here tend to emphasize their better finds, so the differences for the other four locations are probably smaller. Such small effects become statistically significant when the group examined is large enough. This is math.

No individual prediction

The scientists report that when all characteristics are combined, they can explain eight to 25 percent of the differences in sexual behavior. But firstly, this is an estimate, secondly, a large range, thirdly, even in the best case, not the world and fourthly, unfortunately even many medical professionals do not know or understand this, no measure of the strength of the genetic determination, since this estimate itself depends on the specific environment in which the data was collected.

Seriously, the researchers then also admit that their results will never allow them to draw conclusions about the sexual behavior of an individual based on the genome. But the explanation of the mechanism with which the gene locations are connected is rather bumpy. In return, the authors highlight the two findings that were only statistically significant for men.

Explanation of the genetic findings

Specifically, rs283 ... has been associated with typical male hair loss in previous studies and is located in the vicinity of the TCF12 gene, which plays a role in gender development. So this section of the gene may influence something in the sex hormones. The other candidate, rs347… may have something to do with smelling. Hard explanations sound different.

Other data from the study that contradict the genetic influence on sexual behavior are more interesting: the subjects tended to be older, in the large British database 40 to 70 years old, while the average age of the participants of 23andMe was 51.3 years.

If you now look at the cohorts of birth, you can see that less than 0.5 percent (women) or around 2 percent (men) of those born around 1940 were considered non-heterosexual in the above-mentioned sense. In the case of those born around 1970, however, it was already over 6 or 7 percent.

Social impact much greater

In concrete terms: where a certain genotype increases the probability of non-heterosexual behavior by a factor of 1.1, namely from the aforementioned 3.6 to 4.0 percent, the year of birth increases the behavior by a factor of 3.5 ( Men) to 12 (women). In this study, when someone was born determines the sexual behavior measured many times more than the genetic differences found.

Since we can almost certainly rule out that the genes have changed so dramatically in just thirty years, this underscores the role of environmental effects. In addition, genetic influences have an impact in the course of life, the stronger the older you get. So if the 70-year-olds indicate their behavior less often than the 40-year-olds, then that speaks against a genetic determination.

Openness to experience

Associations with earlier studies reported by the researchers should also contribute more to understanding the gene segments found than the aforementioned speculations about hair loss or smelling. There are statistical connections to general risk behavior, smoking (only significant in women), cannabis use, loneliness (let's think back to what I wrote about coping strategies), openness to new experiences (again only significant in women) and before especially the number of sex partners.

Instead of the genes directly determining sexual behavior or even sexual orientation, they seem to be related to curiosity and sexual desire, regardless of the gender of the partner. Or to put it another way: Anyone who goes to bed with more people and tries more, who is more open or feels lonely, is more likely to try someone of their own gender.

Modest contribution from genetics

Against this background, it is quite modest what the best of modern behavioral genetics in 2019 can explain to us about human sexual behavior - even with such a trivial characteristic as whether someone has had same-sex intercourse at least once in a lifetime. The much more complex psychosocial phenomena such as sexual orientation or sexual identity have not yet been considered.

Everyone can judge for themselves whether such insignificant findings justify the billions that this branch of research devours year after year. This does not even think of the nonsense with “depressed” fish, “anorexic” mice or “schizophrenic” rats, which thousands upon thousands work on in molecular biological psychiatry (ADHD and the search for the Holy Grail).

Risk of stigma

And what is it all about that psychiatrists - again or still - deal with healthy sexual behavior? The authors of the study try to avoid stigmatizing or discriminatory descriptions. But there is still a “taste” when psychiatrists and other medical professionals publish such studies, as media researcher O’Riordan also pointed out.

The sociology professor Melinda Mills from Oxford University, who published an accompanying comment in Science:

There is a tendency to reduce sexuality to a genetic determinism or to resent someone for this reduction. It could improve civil rights or reduce the stigma of ascribing same-sex orientation to genes. In contrast, there are fears that this provides a tool for intervention or "cure". Same-sex orientation was formerly regarded as pathological or forbidden and is still criminalized in over 70 countries, in some even the death penalty is threatened.

Mills, 2019, p. 870; German transl. S. Schleim

Conservative tolerance

That the genetic approach reduces stigmatization has been preached by biological psychiatrists for many years, but has now been empirically refuted. That the other even genetically is different, the social distance seems to increase, even if the person is then less to blame for his or her condition.

Findings from homosexuality research that show that conservative people are more tolerant of homosexuals when the phenomenon is described as biological are also interesting in this sense. This seems to have something to do with the fact that this group perceives homosexuality as less “contagious” when it is genetic.So whether it really helps tolerance to spread the fairy tale of the "gay streak" when it also implies that homosexuality is somehow abnormal, I think it is questionable.

Bye, bye, behavioral genetics!

From a scientific point of view, I find that the study by Andrea Ganna and colleagues refutes the behavioral genetic approach once and for all: behavior cannot be explained genetically, but certain genes only minimally increase the likelihood of it. With a fraction of the investment, social science studies could provide much more and much better explanations of sexual behavior; and I write this as someone who would not even carry out such studies myself.

How many people try out same-sex contacts is much more related to the openness of society than to any genes. One could imagine that such “experiments” are actively suppressed, that a society is neutral towards them or that they are even actively promoted. In the latter case, some people would find that this is not their thing, others would find it a nice change of pace and still others would find it to be their great preference (human sexuality - what do we really know?).

Long road to an open society

Preliminary findings suggest that same-sex contacts - at least among women - are now considered “chic” at some US colleges. The media and film industries are likely to do their part. The way Madonna kissed Britney Spears and Christina Aguilera with French kisses in front of the camera at the 2003 MTV Video Music Awards is unforgettable.

Nevertheless, there are still young people today who would rather claim to be transsexual than admit to themselves and others a same-sex preference. This is why hormone blockers are not prescribed to everyone who thinks they are in the wrong body during puberty. But more about that another time.

Our society still seems to have a long way to go when it comes to the free development of sexuality. Nowadays, contrary trends can even be observed more and more in terms of bans on nudity or the criminalization of sexual contact. Only one thing is certain: behavioral genetics will not set people free; it finally belongs in the moth box of the history of science.

Note: This post also appears on Telepolis - magazine for network culture. Cover graphic: Alexas_Fotos on Pixabay.

The discussions here are free and are generally not moderated. Treat each other respectfully, orientate yourself on the topic of the blog posts and avoid repetitions or monologues. When exchanging ideas, things can sometimes get hot, but not be offensive, and above all never go below the belt. Stephan Schleim is a studied philosopher, psychologist and doctorate in cognitive science. Since 2009 he has been at the University of Groningen in the Netherlands, currently as Associate Professor of Theory and History of Psychology. The author also writes for numerous other media.