The question of whether homosexuality has biological causes has starred in quite a few heated debates in science. That question should not be more than an attempt to explain science to a trait of human behavior, as when trying to figure out why some people are born with an unmistakable musical vocation.

Epigenetic marks

However, look for causes of homosexuality has often been done under the stigma suffered by gay people in many cultures and eras, and so it is inevitable that all scientific research that addresses the sensitive issue of the causes arouses suspicion in and inspires a malicious interpretation in who insult it.

The research discussed in this article should not therefore be seen more as an attempt to explain another feature of the human condition, as it can be that such innate musical vocation.


A working group at the National Institute for Mathematical and Biological Synthesis (NIMBioS) based at the University of Tennessee in Knoxville, United States, thinks he has found a clue that could lead to unraveling the mystery of homosexuality. The track has found epigenetics.


Epigenetics is the study of changes in gene expression without changes occur in the DNA sequences. Sergey Gavrilets, of the aforementioned institute team, took advantage of experiments with mathematical models and ran with the result that the transmission of each sex specific epigenetic marks may have parallels with homosexuality.

According to the findings of the study, specific epigenetic marks each sex, which are “erased” and therefore not normally transmitted between generations, can promote homosexuality as outside the deletion and transmitted from father to daughter or mother son.

Studies suggest that the results are born homosexual, implying that there is a genetic basis for sexual preferences of each individual. However, nothing has been found qualified as a major gene for homosexuality, although many studies have looked for a genetic connection.

Epigenetic marks can be the operating mechanism has been looking for. Epigenetic marks constitute an additional layer of information coupled with our genes that regulate expression of these. While genes contain the instructions, direct how epigenetic marks are carried out those instructions. Usually epigenetic marks are produced anew in each generation, but recent evidence shows that sometimes are transmitted from one generation to the next.

Epigenetic marks gender-specific and produced at an early stage of fetal development protect each sex of the remarkable natural variation in testosterone that occurs during the later development of the fetus.

Different epigenetic marks prevent different specificities of either sex are masculinized if they are female, or if males are feminized. The researchers found that when specific epigenetic marks are transmitted to another generation of sex homosexuality may appear in the offspring of opposite sex.

Gavrilets’s team found that when these epigenetic marks are transmitted from father to daughter or mother to child, can arise for investment purposes, as the feminization of certain traits in offspring, including for example, sexual preference, and similarly one partial masculinization of daughters.

This study can solve the evolutionary puzzle of homosexuality, by that sometimes finding that epigenetic marks are transmitted “sexually antagonistic” from one generation to the next, generating homosexuality in the offspring of opposite sex to the parent transmitter.

Mathematical models show that the gene coding for these epigenetic marks can be easily spread in the population, as they always increase the ability of the parent while very rare cases in which besides escape deletion reduced health of the offspring.

The transmission of sexually antagonistic epigenetic marks between generations is the most plausible evolutionary mechanism of the phenomenon of human homosexuality, according Gavrilets. The investigation also involved teachers William Rice, University of California, Santa Barbara, and Urban Friberg, University of Uppsala in Sweden.

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