Is homosexual originating from biology (genetics) or environment and culture? Simple thought questions that take a lot of time and money for research, but the answer is not yet and not convincing. The latest and greatest research in the world claims to have discovered 5 ‘gene regions’ related to homosexuality, but I think this result actually indicates that the trend of homosexuality is not genetic.
1. Homosexuality: quite common
Homosexuality is relatively common in the community. Research in the world shows that for every 100 people in the community, there are about 5 to 10 homosexuals [1]. This rate for women is 2–4%. The rate of difference between the studies was mainly due to the difference in the definition of homosexuality, and whether the participants were ‘truthfully’ declared. In countries with ‘conservative’ cultures in Asia, homosexuality rates seem to be lower than in Western countries. But if doing research objectively and accurately, perhaps homosexual rates between countries may not be much different.
We all have friends who know homosexuals (homosexuals). I also have some homosexual friends, one member of my research lab is homosexual and very talented. In addition to talent in art and cuisine, the homosexual community has quite a lot of successful people in society. For example, former Australian Chief Justice (Michael Kirby) and former Macquarie University President are homosexuals. In Australia politics, there are more than 20 homosexual ministers or ministers. Although sometimes discriminated against, they are generally respected by the community for their talent in the arts, business, and political vision.
The homosexual phenomenon is not new. Historical books from East to West have recorded many cases of kings, people in high positions in society were homosexual. King William II (11th century England) and Earl Philippe First (17th century France) were two famous gay people. Leonardo da Vinci can also be listed as gay too. In Vietnam, perhaps the most famous homosexual is the Left Army Le Van Duyet (living in the 18th century), one of the talented generals of the Nguyen Dynasty, and his merit is built by the people (Mausoleum of Grandparents) Chieu) to thank. The presence of homosexual people most likely dates back to medieval times, before the 17th century.
2. Homosexuality: caused by genes?
The question is why do people tend to be gay? The hypothesis of the influence of genes on homosexual trend was put forward more than 20 years ago. The easiest and most scientific way to know the extent of genetic influence on a biological characteristic is to consider twins.
There are two twins: the MZ group in which two people have 100% of the same gene, and the DZ group with two people ‘share’ 50% of the gene. Therefore, if homosexuality is more in the MZ group than in the DZ group, it is evidence that the influence of genetic factors is present.
In a famous study, the two authors Bailey and Pillard estimated that in the MZ group, when a person is homosexual, the probability of twins also homosexual is 52%; In the DZ group, this probability is 22%. This result is consistent with the influence of genes on homosexuality. They further estimated that genetic factors explain between 31% and 74% of the differences between individuals on homosexual trends [2].
After having ‘proved’ that homosexuality trends are partly determined by genetics, the next question is which gene. This is a simple question, but the answer is not simple. Identifying among the approximately 24,000 genes and about 2 million gene variants (polymorphism) related to homosexuality is work as the ‘needle-stick finding of the seabed’. However, in recent years, many research groups around the world look for genes that they hope can explain why people tend to become homosexual.
One of the gene findings that excited the homosexual research community was published in the early 1990s. Through research on 40 DZ twins, Dean Hamer’s team claimed that they had discovered “gay.” gene ”. Among the 40 twins, they found 33 pairs of ‘shared’ genetic regions called XQ28 [3]. Because the probability that two people of DZ twins (or two brothers) have the same gene is 50%, while in this study this probability is up to 82% (33/40), so this is a Meaningful finding. But this genome has 4 million base pairs, so determining exactly which letters are related to homosexuality remains a scientific challenge. Therefore, many later studies are difficult to duplicate the results of the Hamer group.
Instead of focusing on a single gene, another way to find genes is to look at the entire chromosome, also known as a “genome-wide association study” (GWA) to find out which gene regions may be related to homosexuality. The GWA method requires large sample sizes and high costs and requires international cooperation with many experts from many different disciplines. Last year, an American, Australian and British research team used the GWA method to find genes related to homosexuality and their results were announced at a genetic conference in the United States. This result was officially published in the famous scientific journal Science last week [4].
To understand the results of that research, I need to describe some key details about how the researchers have done. They used the data of the UKBiobank Project and the genetic company “23andMe”. The total sample size is 477,000 people! They define homosexuality by asking subjects to participate in the study. For example, they asked if the research subjects were “having sex” with homosexuals, and then they asked more about the sexual fantasies of the research subjects they thought were trending. homosexual direction. In other words, the way the team defines and determines who homosexuality is not highly scientific, because there is no biological test.
Analyzing results on more than 1 million gene variants, the team found five gene regions (a genetic term called “loci”) in the genome that are related to homosexual trends (in the way they identify as described). on). Strictly speaking, it is not really a ‘gene region’ but 5 variants (SNP). Out of these 5 gene regions, there are 2 regions for both men and women, 2 areas for men only, and 1 region for women only (4). Interestingly, two of the five gene regions were once known to be involved in olfactory and olfactory hormones. These two factors, sex hormones, and olfactory make people feel attracted to each other.
The results of this study were published in the journal Science, but the world of genetics researchers is not … impressive. The reason is that the way the team defines homosexuality is unscientific and somewhat inadequate because without hormone testing, it is difficult to say what the research subjects ‘declared’ is justified. is not. When looking closely at the results of the research, there are few data that are difficult to interpret. Such as SNP number rs34730029 (detected in men), present in 94% of the population — an abnormally high frequency.
But these 5 gene regions explain less than 1% of the differences in homosexual trend! In other words, the discovered genes cannot help the researchers predict whether homosexual or homosexual. In other words, there is no homosexual gene. If this result is correct, then the significance is that the trend of homosexuality has not existed since still in the womb or newly born.
3. Homosexuality: caused by the environment?
If homosexuality trends are not biologically related, the next question is why do people become homosexuals? The answer is environmental and cultural. Kinsey Center for Psychological Research once observed that many couples live together and have children, but later one of them becomes homosexual [5]. Some even observed that the flight attendant specialization is an industry that attracts many homosexual men [6] (but this trend does not mean working in the aviation environment is the cause of homosexuals). Of course, it is not excluded that some people choose to become homosexual.
Since the 1960s, there have been many theories explaining why people become homosexuals. These hypotheses emphasize social and environmental factors during the developing stage, parental influence, and parent involvement. Notably in these studies was observed by psychologist Irving Bieber, when he discovered through statistical analysis that in men, the ‘normal’ adults but later grew up to become homosexual, It was earlier associated with the mother than the father [7]. The results of this study were repeated by other research groups. For example, a study in the mid-1960s found that nearly 70% of homosexual men were close and attached to their mother, and about a third were unfriendly to their father [7].
In summary, the latest scientific research shows that there is no homosexual gene, and this indicates that homosexual tendencies were not born right from birth. Many past studies indicate that homosexuality is mainly due to social and environmental factors, especially the attachment of men to mothers.
Documents:
[1] LeVay S. The Sexual Brain. Cambridge, MA: MIT, 1993. Trang108.
[2] Bailey JM, Pillard RC. A genetic study of male sexual orientation. Arch. Gen. Psychiat 1991;48, 1089–96.
[3] Hamer DH, Hu S, Magnuson VL, et al. A linkage between DNA markers on the X chromosome and male sexual orientation. Science 1993; 261, 321–7.
[4] Ganna A, et al. Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior. Science 2019;365: eaat7693
[5] Wardell PB. Dr. Kinsey and the Institute for Sex Research. New York: Harper & Row 1972, Page 76
[6] Brown J. 35,000 feet away — Why flying the (very) friendly skies is still sexy for many gay men. Slate 29/10/2018
[7] Bieber I, et al. Homosexuality: A Psychoanalytical Study. New York: Vintage Books, 1962, Page 172.
