There is no "homosexuality", there is no one to forget about the Kinsey scale, heredity is still important

The largest study of the genetic foundations of sexual orientation has been released

Heredity really has a great influence on human sexual behavior, but it cannot be explained by some one genome or simple formula. Moreover, the traditional "scales of sexuality" existing in psychology seemed to be based on the wrong ideas of scientists. These are the main results of the largest study of the genetics of sexuality published in the journal Science by an international group of scientists. "Medusa" tells how this issue was studied earlier, what is the essence of a new study and why there is so much criticism around it.

Human sexual behavior - as, in fact, any other, for example, a risk or musical hearing - can have a biological basis that can influence the decision made by a person. It can be divided into two components: hereditary (genetic) and acquired, and acquired features can be both congenital and formed in childhood.

Around the beginning of the 1990s, with the advent of affordable methods of analysis of the genome, biologists are trying to figure out what can be a genetic component of sexual behavior. The very presence of such studies, of course, does not mean anything that this component is very important or that some biological features completely determine the behavior of a person-this, of course, is not so. However, statistics, research research and genetic analyzes allow you to evaluate the contribution of the biological components and at least try to establish mechanics of how precisely the “biology” can contribute to one or another behavior (albeit not to determine it).

As for the research of sexuality, while the results of scientists in this area were not too impressive: in 2013, the American Association of Psychiatrists had to release a special appeal in which it is noted that today the reasons for the formation of orientation are not known, but it is only known that “everything is complicated” .

Previous studies: Heredity affects orientation. But to make a "test for homosexuality" will not work

However, there is definitely a hereditary component in the formation of orientation, and it is quite significant. This is evidenced by arguments that are considered in genetics a modern “gold standard” - these are the so -called twin studies.

Gemini, as you know, can be one-eating and multi-tier (homo- and heterozygous), the former are the genetic clones of each other, the latter have only half of the identical DNA. If in the appearance of a sign of homozygous twins are reliably more similar to each other than heterozygous, then the only thing that can be explained in the symptom between the first and second is the contribution of heredity. The influence of the family, environment and other factors on this difference is impossible - unless, of course, the study is done correctly.

The largest work of this kind was done in 2010 today and covered almost four thousand pairs of twins from Sweden. It showed that the hereditary component can explain more than a third of the variation of the sign in men and about 20 percent of variation in women - that is, sexual orientation is inherited about as much as left -handedness.

It is important not to confuse “Variation” here with “probability”, with the ability to predict a sign for a particular person by his DNA. The first is considered for the population as a whole and can be very different from the average value in different people. The second, of course, depends on the first, but the environment also affects it, and even more - the prevalence of the phenomenon in the population. Even for such a sign where inheritance is very significant, DNA data can only slightly improve the quality of the forecast if we want to say something about a particular random person. That is why the genetic tests on sexual orientation (or, for example, on left -handedness) are meaningless in practical terms - it is not good or bad from an ethical point of view.

Gemini studies, although they allow you to calculate the contribution of heredity, do not say anything about the mechanisms of how it manifests itself, that is, due to which, in general, genes can affect people's behavior. For this, another type of work has been invented - full -gene analyzes of associations (GWAS).

They are done like this: every person who participates in the study answers the questionnaire with many questions about himself, his life and gives a DNA sample. Genetics compare thousands of such trials and profiles with each other and try to find those genetic differences that are reliably associated with a particular sign. “Differences” in this case are not the simple and understandable mutations that can be unequivocally translated into signs, such as the ability to digest milk (it depends on one replacement in one gene). “Differences” or polymorphisms, SNP are precisely the discrepancies in DNA, which in themselves mean nothing, but can label those areas of the genome that for some reason are important for the manifestation of an external attribute, in this case, sexual orientation.

The problem is that each of us already has a lot of such differences, which means that if you wish, you can find such that they are “connected” with any in advance a given sign - at least with love for the desired series or the genre of music. Therefore, in order to prove that this connection is not accidental, but really reflects a certain internal biological mechanism, it is necessary to collect huge - much more than in twin studies - the number of participants ( cases where scientists, as it were, forget about it, only confirm the rule ).

New work: women and men have different homo- and heterosexuality, and Kinsey was wrong

But in the new work, it was still possible to analyze the data of a large number of people: in previous such studies there were less than there are hundreds of times; The conclusions of scientists were very doubtful. It became possible to carry out a new job in an impressive sample of half a million, primarily thanks to the British Ministry of Health, which in 2006 launched the UK Biobank initiative to collect biological samples in healthy people. It was on them - as well as on an additional sample of the data of the famous company 23andme, a new study was conducted.

In the press materials, on the site , which the authors of the new work created, accompanied by a scientific article, and, of course, in most media headlines, the main result of the study was a refutation of the existence of “Gene Gay”, which allegedly determines the orientation of a person alone. This concept, which arose back in 1993 in connection with the opening of special markers on the X-chromosome, is actually not relevant for a long time-the initial discovery was soon refuted quite soon, and despite some attempts of revival , no one discovered them in most other studies. However, the absence of a single genetic “switch” for such a difficult sign is generally not surprising.

But what is really interesting and unexpected in a new study is the discovery of the objective genetic complexity of human sexuality - not psychological or social, but quite mundane, genetic. Firstly, it turned out that in men and women a genetic predisposition to the choice of a partner is different. In total, five genome (SNP) is discovered reliably related to the orientation of the genome site. However, two of them were found only in women, two - only in men, and only one turned out to be important for both sexes. This suggests that people of different sexes leading to the formation of orientation can differ significantly in their device.

However, these are not "five genes"

It should be reservated that even these five genetic markers taken together do not even pull on a five -part “Gene Gene” - their total contribution to heredity is less than one percent, everything else is “dark matter” from many less significant genetic characteristics, which even with half -million sample of genomes cannot be reliably detected.

Secondly, the authors unexpectedly found that “heterosexuality” and “its degree” are different things. Sounds confusing? This is true. The fact is that in the study there were actually two parts, where the orientation was determined and studied in different ways. In the first, all the participants in the study were divided into only two groups: heterosexuals and “non -metroosexuals” - the latter was attributed to everyone who indicated in the questionnaire that at least once in his life he had sex with a person of his gender. Such binary division was chosen primarily for statistical reasons - it is easier to find subtle genetic differences between large groups. In the second part of the study, Nezheterosexuals were divided into several groups in accordance with what share in their life is occupied by partners of their gender. And only then they studied what genetic features correlate with this share.

It turned out that belonging to the group of “Nezheterosexuals” and the share of partners of their gender are two different things that depend on different genetic characteristics. And that means they are determined by different mechanisms. “This suggests that at the genetic level there is no single scale of attractiveness from the opposite sex to their own,” the authors of the study conclude. But the traditional lines of sexuality like the Kinsey or Klein scale imply the existence of such one-dimensionality and, apparently, should be revised.

The last, most risky part of the study for interpretation, is devoted to the analysis of the genetic correlation between orientation and other behavioral characteristics. The work states that the presence of homosexual contacts to some extent is genetically associated with a greater tendency to risk, with an increased frequency of depression and bipolar disorder, with the use of tobacco and marijuana.

However, in this part of the work it is already completely incomprehensible what lies behind the word “connected”: not only the mechanisms of the influence of heredity on behavior are not known for all these correlating signs, but it is also not clear where, in fact, the chicken is, and where the egg is. For example, is it not a detection of a tendency to risk by a simple consequence of the fact that it is more risky people who are not afraid to honestly answer the profiles of the same -sex sex - the action that was a criminal offense during their youth? At the average age of participants at 40-69 years, such an explanation seems quite believable.

The authors enlisted the support of LGBT organization, but this did not remove all the questions

The study on such a politically charged topic, of course, could not but cause criticism. I must say that the authors were clearly preparing for this and did everything possible to remove the maximum number of claims, but still achieve publication.

The language of the article and even the design of its illustrations, according to scientists, was agreed with members of several LGBT organization. It contains several disclaimers about terms and possible erroneous conclusions, and in addition to the article itself, a press release and commentary, scientists have created a special site where they tried to answer the main questions, primarily about the restrictions on the work and why it had to be done at all.

However, this last question, it seems, was not on the teeth of even trained authors. On the site, it is responsible for by listing what can be obtained as a result of such a study: the discovery of genetic markers, the discovery of new biological ways involved in the formation of orientation, the assessment of the contribution of heredity, and so on. In other words, we are talking about ordinary scientific curiosity.

However, not everyone agrees that in this case this may be enough. “As a quiru and genetics, it is difficult for me to understand the motivation to study the hereditary basis of non-heterosexual behavior,” Joseph Witti writes about the work of colleagues at the Brod Institute. “I did not see convincing arguments in favor of the fact that the potential positive results of such a study outweigh its potential harm.” Another colleague, Stephen Relley, believes that work should not be published at all, because readers may not understand why the genetics of this particular feature should be explored, and not a thousand serious diseases.

There is reason to believe that the article was really not dared to publish for a long time - this can be guessed at least by the number of consultations, approvals and discussions that preceded the publications. And it seems that the fact that the first author of the work, Benjamin Neil himself played an important role in a positive decision, just like some critics are an open gay. At least this fact is necessarily specified in the discussion around the article published in the New York Times.

Alexander Ershov