Homosexuality: were you born this way? Is the question finally answered?

Has NatGeo already answered the unanswerable question while no one was paying attention?

The video below is part of a National Geographic documentary aired on December 21st, 2008. The episode explains how both identical twins could have the gene for a certain disorder, yet only one twin would actually have the disorder. Homosexuality has been ruled out of the disorders spectrum of course. But in the same vein, this part of the episode tackles the possibility of biological factors intervening in the result of one identical twin being gay and the other being straight.

The main idea revolves around Epigenetics, a new branch of genetics that studies how one’s DNA sequence is not the only factor in one’s phenotypic (actual) outcomes. NatGeo is speculating on how one’s sexual orientation is determined during embryonic development.

It is a known fact that identical twins have the same DNA sequence. The idea of Epigenetics revolves around the effects of particular proteins on gene expression. Will this new area of genetics answer the dilemma of the century: is homosexuality a work of biology or is it a plain choice?

Well, we still don’t know if there is a “gay gene”. But studies suggest the following:

Identical twins begin to develop differences starting 5 weeks in utero. The study run by the NatGeo took an example of twins, one straight and the other gay. Even though they were raised together (in the same household, with same parents, and in the same environment), the sample twins turned out to have different interests (one in dance and academia and the other in sports), knowing that they have identical physical traits.

In the general population, chances of being gay are less than 5%. But if one has a gay twin, the chances raise considerably: 25% if you share half the genes and 50% if you share all of them. This could indicate that there is a genetic component to sexual orientation but not exclusively, because, if so, all identical twins would be both gay.

Scientific reminder: at first we are all female by default. Then, after gonads mature and drop (in utero), testosterone is released in the fetal blood stream, the masculinization of the body initiates as well as the masculinization of the brain, which may determine sexual attraction. Some scientists believe that the more the hypothalamus is exposed to testosterone, the more the individual is inclined to women in the future. Therefore, homosexuality could be explained by insufficient testosterone release or it’s just that the brain doesn’t absorb enough of the hormone.

But that’s not all. Where are Epigenetics in all that? Well, first you have to know about Epigenoms: they are series of chemicals acting like switches capable of activating or deactivating individual genes. One of the switches works by a process called “DNA methylation” which consists of enzymes attaching a methyl group to a gene and therefore activating or deactivating it, depending on the conditions. But the gene remains intact, it’s just that it’s either expressed or not.

This concept explains many twists that can take place in character expression and why genetics are so random and unpredictable even within the same family.

And this might also elucidate why one’s brain absorbs more testosterone than another! Does this answer the gay/straight question?

So we can conclude that our traits are neither a product of genes nor of environment, but the two factors are linked by Epigenetics!

What do you think? Comments are for that!


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