Over the last two decades there have been several studies on the intriguing subject of sexual orientation in human beings. These studies have led to a conclusion that it is, in part, down to our genes that we are attracted to the gender(s) that we are. However, a recent study on male twins suggests this may not be the case after all.

New research conducted by the University of California, consisting of thirty-seven sets of identical male twins, has shown that the sexual orientation of a male can be predicted through minute changes in his DNA after being born, through a field known as epigenetics. For those of us not so clued up in the field of science and biology, this is the study of changes in organisms caused by alternations in gene expression. These changes are known to be influenced by environmental factors.  It has been found that only 20 percent of identical twins are both gay, which contributes further to the idea that there must be causes that are not due to genetics and more towards the newly found possibility that environmental factors could play a part in being gay.

On homosexuality and reasons why people are or are not homosexual, Professor Darren Griffin, Professor of Genetics at the University of Kent, adds: “While there is strong evidence in general for a biological basis for homosexuality my personal impression has always been one of a multiple contributory factors, including life experiences.”

By looking at the DNA of the participants, there were areas that functioned differently in the homosexual twin in comparison to his heterosexual other half. This is where scientists say there is 70% accuracy of predicting whether a male is gay or straight – by looking at differences in the methylation of their genes. However, this high percentage is only relevant to the test population, not the general population in which a much lower proportion of people are homosexual.

The study however has brought up a few issues and concerns from researchers, one being that with this information people may believe it possible to tamper with DNA in order to change sexuality. Tuck Ngun, at the University of California, stresses that the findings could be wrongly used by people who punish people for being gay. This caused him to drop out of the study as he believed that people with unhealthy motives could misuse such information. Another problem is the breaching of an individual’s privacy as being able to identify sexuality through genetic information means medical records may disclose this.

As this research was just published on 8th of October at the annual meeting of the American Society of Human Genetics in Baltimore, it is still early days in terms of coming to definite conclusions and to discover why humans are different in our sexual preferences. Ngun says that researchers hope to conduct another similar study consisting of different groups of twins in a larger group of participants, where they will observe whether the same marks are more common in gay men than in straight men.

Becky Waldron

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