Genetic analysis of half a million people ‘s data has concluded that there is no single gene responsible for homosexuality.
A recent largest study of the relationship between a person ‘s sexual orientation and its genome has identified five areas that are associated with unconventional sexual orientation. Yet none of the signs allow you to come close to predicting a propensity for any behavior.
The findings, published August 29, 2019, in the journal Science, based on research into the genomes of 500,000 people, overshadow early smaller scientific work in the field, and make it possible to unequivocally confirm the suspicions of many scientists: although sexual preferences carry a genetic component, no gene has a meaningful effect on sexual behavior.
“There ‘s no ‘gene for homosexuality’” argues Andrea Gunn, a geneticist scientist at the Broad Institute of MIT and Harvard in Cambridge, Massachusettes and one of the study ‘s authors.
As a result of the analysis, Gunn and her colleagues assessed that only 25% of sexual behavior could be explained by genetics. This is more influenced by factors of social environment and culture — which roughly coincides with the view of the authors of other small studies.
Despite the fact that the results of the research are not in doubt in the scientific community, there are fears that they may not be applicable to the entire population of people on earth. The lion ‘s share of genomes was collected from representatives of Europe and the United States over the age of 40. In addition, following the rules of the Convention on Human Rights in the Field of Genetic Research, members of the LGBT community, who are transgender and intersex people, were excluded from the sample.
Scientists have long suggested that some genes may partially affect sexual orientation. Studies from the 1990s showed that single-male twins were more likely to adhere to the same unconventional sexual orientation than double-female (twins) or adopted brothers/sisters. Some work has suggested that a certain part of the X chromosome is associated with the sexual orientation of biological men. However, subsequent studies have refuted this.
But all of these studies came from very small populations and were focused mainly on men. This severely limited scholar in their search for a variety of options related to sexual orientation.
In the latest work, Gunn and his colleagues found a way to use the genome of hundreds of thousands of people. The researchers divided the participants into two groups. The first group included respondents who indicated that they had experience of same-sex sexual relations, the second that they did not.
The objects of scientific analysis were the facts of the presence of single nucleotide polymorphism (SNP) in the DNA of respondents. In the first phase, scientists analyzed more than 1 million SNP ‘s and identified groups of people who had more common mutations among themselves while having the same sexual preferences. It turned out that genetics explains 8% to 25% of the variability of sexual behavior. In the second phase, Gunn and his colleagues attempted to determine which varieties of SNP affect same-sex sexual behavior and found the 5 most common signs. However, these 5 signs together explained only 1% of the variability of sexual behavior.
Gunn said this suggests that there are many genes associated with same-sex orientation that has not yet been found. It will take a much larger sample size to detect them.
At the same time, Gunn warns that the SNP found cannot be used to predict the sexual preferences of an individual because no significant effect of at least one gene on orientation has been found.
Although researchers have found some SNP found in members of one type of sexual behavior, they do not fully understand what these genes are responsible for. One gene, Gunn said, is related to the smell affecting sex appeal. The other is associated with male baldness, a trait that depends on sex hormone levels. Apparently, these hormones themselves affect homosexuality.