Epigenetics and homosexuality: debriefing

Alexey Aleksenko, "Snob" 

As you know, one of the most pressing problems on that eighth of the land from where we have our roots is the problem of sexual orientation. Among our compatriots, the phenomenon of homosexual attraction raises many questions: are homosexual marriages permissible? Will all gays burn in hell? Can gays vote in the elections to the State Duma of the Russian Federation or host programs on Channel One? Is it possible to ordain an archimandrite as a bishop if he is gay? And other similar problems.

One of the issues of particular concern to the public is: is sexual orientation innate or does it develop under the influence of life circumstances? For some reason, many (and not only in our eighth grade, I must admit) this question seems especially important from a philosophical point of view. The logic here seems to be the following: if gays are born gay right away, then there is no demand from them, and if, for example, all this is laid down by primary school age, then you need to properly whip a little tomboy or pick up the right pictures for him to view before going to bed – and everything will be removed by hand, the problem will be solved. And then, of course, the issue of gay propaganda must be urgently addressed, etc., etc.

The author of the note, along with the elite of modern science, does not really understand this logic. What difference does it make how the influence of circumstances shapes a person's fate? Whether it is through genes, through pathogenic bacteria, through bad company or books read in childhood – "free will" (if it exists, and whatever is meant by it) can, apparently, resist this within certain limits. And beyond certain limits – he can't, and he doesn't want to. Free will is generally a great working concept when applied to one's own actions, but it works very badly when describing the actions of people around you. That is, if there is a question, it is clearly not of primary importance.

But, again, together with the elite of modern science, we are forced to pay attention to the problem of innate orientation, since this problem is so bothering humanity as a whole and on average. And so, we give it.

The fact that the "homosexuality gene" was discovered was first heard by the masses back in 1993 – then Dean Hamer's research group suspected a certain region of the X chromosome that it was involved in the predestination of a person's sexual orientation. Then this conclusion was angrily refuted a couple of times by other scientists. Generally speaking, there were two problems. Firstly, no one could indicate which of the genes of the specified region of the chromosome does this subversive work, what is its function and, accordingly, what is the mechanism of the process, at least hypothetical. Secondly, everyone was spoiling the research of identical twins. As we know, their genes are exactly the same, however, when one of the twins was gay, the probability of the second having the same sexual orientation was only from 20% to 50%. Such data seemed convincing to supporters of both polar points of view. That is, there is definitely something in the genes, and this breaks the whole logical structure of those who want to solve problems with spanking. But those who want to write off everything on genes are irritated by the remaining unexplained 50-80%, that is, frankly, most cases.

And now a new sensation has shaken public opinion: there is, after all, there is this gene!

"No, nothing like that!" the opponents immediately replied (Ed Yong, The Atlantic: No, Scientists Have Not Found the 'Gay Gene').

What was it about? In the laboratory of Eric Vilen, at the University of California in Los Angeles, there is a postdoc named Tak Eun Un (so, apparently, you need to write his name in Russian letters if he is an ethnic Korean, and in English he is spelled Ngun). This is how he examined the DNA of 47 pairs of identical twins, 10 of whom were unanimously gay, and in the remaining 37 pairs the sexual tastes of the brothers did not match. Our young man did not investigate the gene sequence itself, but the pattern of DNA methylation. 

Methylation is such additional labels on your genes that seem to determine which gene is destined to be active and which is not. In principle, it was known that these marks on genes are erased during the development of the embryo and then applied again, so this is not "heredity" in its purest form. Nevertheless, this is one of those mechanisms that operate, as they say, "at the genetic level." Scientists call this "epigenetics", and we have already written about it once. An additional complication is that epigenetic marks, as it turned out, are not always erased: some can be transmitted from parents to children.

So, our young scientist collected data on 140,000 points in the DNA of our twins, where there may or may not be a methyl group. Among them there were 5 (!!!), where the methylation pattern obviously correlated with the orientation of the twins. In other words, sexual orientation is indeed recorded in genes – though not in the DNA sequence inherited, but in chemical modifications that occur during individual development and are usually erased in the next generation. This was reported by scientists at the annual conference of the American Society of Human Genetics.

Of course, from the point of view of statistics, such a result is pure nonsense. If there are a lot of features to study in a very small sample, then there will definitely be groups of features that correlate with each other, simply because of crowding. Critics of the work did not fail to draw attention to this circumstance. To justify the scientists, we can say that they were not so straightforward at all. First, they split their sample of twins (already scarce) into two groups. Correlations were calculated in one group, and in the second group they were used to "predict" sexual orientation. It turned out to predict with an unprecedented high accuracy of 70%. From the point of view of statistical science, a simple focus with two groups partly solves the problem of a small sample and a large number of comparison parameters.

Secondly, the researchers tried to understand what exactly the genes whose methylation is so important for determining whether you are gay or straight do. One of the genes turned out to be somehow connected with the passage of nerve impulses, the other is involved in the immune system (unfortunately, quite little is known about the functions of human genes, and for most of them "involved in this and that" is the maximum that can be said about them).

It would be very nice, of course, to supplement this work with a couple more strokes. Firstly, when researchers say "we have divided the sample into two subgroups", it is ridiculous to believe them. If I understand correctly how things are usually done in laboratories, of course, at first they looked for correlations in the whole pile at once and only then, at the stage of preparation for publication, they brought statistical gloss. Now, if they could test the predictive power of their hypothesis on a completely different sample, preferably blindly – here personally I will be ready to believe them unconditionally.

Secondly, the function of genes. Well, what does immunity and nerves have to do with it, please tell me? Offer at least some hypothesis. In fact, there is already a hypothesis, and it was expressed three years ago by William Rice from Santa Barbara. Rice suggested that some of the epigenetic markings on DNA may determine the susceptibility of genes to the action of the hormone testosterone. In boys and girls, this sensitivity is, of course, different. In this case, if methyl tags are indeed sometimes inherited, and if a male fetus accidentally forgets to erase the tags inherited from his mother (namely, from his mother he receives an X chromosome, which is exactly involved in this story), he will inherit a female type of reaction to the hormone, which may, according to the authors of the hypothesis, "feminize" his brain, with the corresponding lifestyle consequences.

Well, if our enterprising scientists managed to somehow connect their five loci, where the presence of a methyl group correlates with sexuality, with sensitivity to sex hormones, their construction would immediately acquire indestructible credibility. Rice's hypothesis has been waiting three years for just such confirmation (or falsification, if none of the five loci reacts to testosterone in any way). Apparently, this is the direction in which their research will develop, so we should not fuss until we receive a final answer.

And when the answer is received (yes, of course, it always happens that way), it would be good to understand in advance by that time what everyday conclusions follow from it. Because, of course, there was not a single scientific discovery in history that was not tried to put at the service of obscurantism. But if the discovery of "homosexuality genes" – or "homosexuality tags in the genes" – is confirmed and this will encourage someone to refuse to solve social problems with the help of flogging and legislative harassment, then scientists have tried not in vain.

The story of the epigenetics of homosexuality can be read in Science (Michael Balter, Homosexuality may be caused by chemical modifications to DNA) – there, it seems, the most balanced and unbiased point of view is presented.

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14.10.2015