Scientists believe that homosexuality is caused by a combination of environmental and genetic factors
The preference for relationships between people of the same sex is determined by both environmental and various genetic factors, a large-scale study has confirmed.
This means that there is no such thing as a & # 39; gay gene & # 39; that you determine sexual preferences – just like many other human traits.
Instead, thousands of genetic regions are involved, which together account for around 8-25 percent of the variation in sexual preferences between people.
Researchers confirmed this after studying genetic and survey data from more than 470,000 volunteers from the UK Biobank and 23andMe.com.
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The preference for same-sex relationships is determined by both environmental and diverse genetic factors, a large-scale study has confirmed (stock image)
WHAT SCIENTISTS THINK OF SAME-SEX ATTRACTION?
Scientists have long searched the extent to which genetic and non-genetic (or environmental) factors influence a person's preference for same-sex relationships.
Previous studies had hinted that genetic factors were complex, but their relatively small scale made it difficult to draw reliable conclusions.
In the new study, researchers used data from more than 470,000 people, more than 100 times more than previous works.
They confirmed that homosexuality stems from both environmental and genetic factors.
Instead of being one gay gene, the team found thousands of places – or loci – in the genome that seem to play a role in sexuality.
Only five of them had a & # 39; significant & # 39; impact – and together all factors accounted for only 8-25% of the variation in sexual attraction between different people.
The factors that play are so complex that it is impossible to predict from a person's DNA whether they are attracted to members of the same sex or not.
Geneticist Andrea Ganna of the Massachusetts General Hospital and colleagues interviewed more than 470,000 individuals whose genetic data are recorded in the UK Biobank or at the personal genomics company 23andMe Inc.
Study participants were asked questions such as & # 39; Have you ever had sex with someone of the same sex? & # 39; and & # 39; To whom do you feel sexually attracted? & # 39;
The authors conducted so-called Genome Wide Association Studies to try to identify genetic patterns that were consistent with a variety of behavioral, personality, and physical traits.
& # 39; We have established that the underlying genetic architecture is very complex & # 39 ;, the researchers wrote in their paper.
& # 39; There is certainly no single genetic determinant – in the media also the & # 39; called gay gene & # 39;. & # 39;
This finding invalidates the suggestion of a previous study in 1993, which reported that a genetic marker was found that is more common in gay men and that is passed on from mother to child in the X chromosome.
Instead, the researchers discovered that thousands of genetic loci – areas of the genetic code – were scattered throughout the genome.
Each turned out to have small individual effects that together contribute to differences in people's predisposition to same-sex sexual behavior.
Only five of the thousands of loci identified by the team were & # 39; significant & # 39; to be associated with same-sex behavior.
In total, all tested genetic variants accounted for only 8-25 percent of the variation in same-sex sexual behavior between different people.
Some of the genetic variants are linked to the biological pathways for sex hormones and smells, which, according to the researchers, could provide indications of some mechanisms that influence the behavior of the same sex.
"All measured common variants together explain only part of the genetic heredity at population level, and do not allow meaningful prediction of the sexual preference of an individual," the researchers said in their paper.
& # 39; In my opinion, one of the most interesting findings (…) is that from a genetic point of view there is no continuum whatsoever of sexual behavior from the opposite sex to the same gender, & # 39; said Dr. Ganna.
This finding was repeated by paper co-author and geneticist Benjamin Neale, also from the Massachusetts General Hospital.
& # 39; We found that the Kinsey scale, which places individuals in a continuum from essentially exclusively opposite sex partners to only same sex partners, is really too simple a simplification of the diversity of human sexual behavior, & # 39; he said.
This means that there is no such thing as a & # 39; gay gene & # 39; that determines your sexual preferences – just like many other human traits (stock image)
The team also found that the genetic influence on same-sex behavior differs slightly between men and women, with sex overlap lower for sexual preferences than for other behavioral traits.
& # 39; This is not the first study to investigate the genetics of the same gender behavior, but the previous study was small and had no power &, said dr.
& # 39; The results of that study were usually not reputable. & # 39;
& # 39; So we decided to form a large international consortium – and we collected data for more than 500,000 people. & # 39;
& # 39; To give you an idea of the scale of the data, this is about 100 times larger than previous studies on this subject. & # 39;
The findings, Dr. concluded Ganna, & # 39; underline the importance of resisting simplistic conclusions because the behavioral phenotypes are complex, our genetic insights are rudimentary and there is a long history of misusing genetic outcomes for social purposes. & # 39;
Researchers studied genetic and survey data from more than 470,000 volunteers from the UK Biobank and 23andMe.com. Pictured, an artist & # 39; s impression of human DNA
Sociologist Melinda Mills of the University of Oxford wrote in an accompanying perspective article and emphasized the limitations of the study's findings.
The researchers found specific genetic loci associated with same-sex behavior, & they commented, but their effects were still miniscule.
& # 39; When they combine the effects of these loci into one comprehensive score, the effects are so small (less than 1%) that this genetic score could not be reliably used to predict sexual behavior of an individual of the same gender. & # 39;
& # 39; Use of these results for prediction, intervention or an alleged & # 39; remedy & # 39; is completely and unconditionally impossible, & # 39; she added.
& # 39; I think the results of this article indicate that the genetic basis for human sexuality is extremely complex, diverse, and nuanced, "said Nina McCarthy, a geneticist from the University of Western Australia who is also not researching was involved.
& # 39; I believe that well-conducted genetic studies on human sexuality such as these can help inform and perhaps have a positive impact on our understanding of human sexual diversity, & # 39; she added.
Dr. McCarthy noted, however, that the methodology had limitations compared to the.
& # 39; The sample did not include transgender people, intersex people, and other important people and groups within the queer community, a limitation that the authors say they hope will be addressed in the future.
The full findings of the study were published in the journal Science.
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