[dropcap]A[/dropcap]nybody who identifies as gay can tell you that it’s not something they would have chosen. Especially considering the current political climate and the frequency of hate crimes and homophobia, it’s not an easy life. This would seem to be common sense, but many people still believe that being gay is a choice, or worse, a mental illness. So, why are some people gay? Researchers now believe that biological factors may have something to do with it.
One of the most common arguments against homosexuality is, “There is no gay gene!” This is true. Identical twins share the same genetics, but they may have different sexual orientations. However, reducing biology to just genetics is oversimplification. Scientists now believe that sexuality may be influenced by other factors: epigenetics and hormones.
Epigenetics is the branch of science that studies traits that cannot be explained by changes in DNA sequences. In most cases, these changes come from chromosomes, which don’t affect the gene sequence, but can turn traits on and off. The best known example is methylation, in which a methyl group is attached to the DNA sequence. In 2012, Dr. William Rice proposed that marks like this on genes, known as “epi-marks,” may impact sexuality.
In most cases, epi-marks are erased when reproductive cells are produced. However, recent research has shown that some marks can be passed on to the next generation. Dr. Rice hypothesized that when marks are passed from father to daughter, or mother to son, the result might be same-sex attraction. He also believed that these marks would enhance a fetus’ sensitivity to testosterone while in the womb.
Dr. Rice’s research inspired Dr. Tuck Ngun to study methylation patterns in twins. Thirty-seven of the pairs had differing sexualities, and ten pairs were both gay. After several rounds of careful analysis, he identified methyl groups attached to five DNA regions. These groups appear to be very closely linked to variations in sexual orientation. They then tested whether these marks could be used to predict sexuality, and were able to reach 70% accuracy.
Why twins end up with different methylation patterns still isn’t clear. If Rice is correct, it’s possible that marks were erased in one twin, but not the other. However, it’s still not known how or why this happens. This experiment also must be repeated to give it more credibility. There’s also debate on whether it should be continued. Some worry that if a concrete cause for sexuality variation is found, people will attempt to find a “cure” for homosexuality.
There are issues with this theory that still need to be fixed, but it will be interesting to see what scientists are able to discover about human sexuality in the future.