Boston Globe - "What Makes People Gay?"
We find a comprehensive report in the Sunday Boston Globe Magazine: What Makes People Gay?
The article takes notes of the fact that "the clear focus of sexual-orientation research has shifted to biological causes, and there hasn't been much science produced to support the old theories tying homosexuality to upbringing."
The article takes note of the research in Sweden which was the subject of my Gay Limbic Reaction to Pheromones post as well as my Of Fruit Flies and Men post. In addition, the article discusses other completed studies and most interesting, some that are ongoing at present.
In discussing the possibility of a genetic component of sexual orientation, he mentions the evolutionary paradox, the idea that since gay men have 80% fewer offspring, why would a "gay gene" not inevitably disappear. Other research, though, has shown that the inheritability of homosexual orientation is passed along on the mother's side of the family as it is associated with the female X chromosome just like left handedness, and is therefore not dependent on gay males having children.
When it comes to hereditary, it is important to note that in the case of sexual orientation, as in handedness, these genetic factors provide only a bias in one direction or the other. Other conditions such as the chemical and hormonal environment that exist after fertilization are also determinate.
The article points to work by Eric Vilain and Sven Bocklandt at the University of California, Los Angeles.
Instead of looking for a gay gene, they stress that they are looking for several genes that cause either attraction to men or attraction to women... It's not a question of what genes you have, but rather which ones you use, says Bocklandt. "I have the genes in my body to make a vagina and carry a baby, but I don't use them, because I am a man."
Well! It's nice to see that what I wrote about ten years ago is now the subject of serious scientific research. The main idea is that we all have the same sets of genes which would result in our being attracted to males or attracted to females (or both or neither) so it's a matter of which set(s) are left turned on during the complex interactions which occur after fertilization.
When we consider identical twins, we know the the original zygote splits in two yielding two distinct individuals with an identical genetic makeup. What we don't know is how long after fertilization that sexual orientation is established. If it happens before the zygote splits, then the twins will have the same orientation. If it occurs afterward, then the likelihood that their orientation would be the same is that of fraternal twins. I think the articles discussion of "imprinting" was trying to make this point.
All in all a good review of current research into the factors which determine sexual orientation.