Thursday, December 13, 2012
Epigenetics may provide a biological explanation of sexual orientation
There’s more attention to the complicated biological concept of (Wiki reference) epigenetics as related to homosexuality.
The studies mainly concern the epigenetic relationships between mothers and sons, and fathers and daughters.
Since the mother has a second X chromosome, some of the information on the second chromosome seems to control how genes on the other chromosome may be turned on or off. This information is called “epimarks”. A epimark might be viewed like a chemical catalyst, or an extra ingredient in a recipe needed to make some process work. Epigenetics could explain how certain traits that would seem to defeat reproduction (in the normal sense of evolution) persist at a constant rate in most populations (maybe 3-5%). There are also some indications that female relatives of homosexual men have more children than average, so the markers still might increase reproduction in a family as a whole. It is relatively common in biological communities that not all individuals reproduce equally well.
The story was covered on CNN by Anderson Cooper’s AC360 Wednesday, and there is a detailed story in the New York Daily News by Christine Roberts, here.
The epigenetics might act by suppressing or inhibiting a natural “instinct” to reproduce, and allowing the intellect , cognition, or “brain belief” to take over sexual interest. The personality could find other processes, like upward affiliation or idealization, more rewarding than just the idea of a future lineage. In any case, in men at least, the process has absolutely no effect on physical appearance or strength or normal competitive and cognitive capacity. It seems to be like a “plug and play”. A video with Lesley Stahl gives more perspective than the other:
The video above makes some interesting, and complicated observations about identical and fraternal twins. It also says that the exposure of the hypothalamus to testosterone, before birth, might be related to sexual orientation and take place as a result of epigenetics. It’s also true that the likelihood of male homosexuality increases with older brothers (of right-handed “pitchers”). A first born son has a 2% chance (I was the 2%, but I do bat right-handed). The mother’s body seems to remember carrying previous sons. It may be important, in order to have long-term reproductive advantage, to have at least one heterosexual son (first born) to have a lineage, but not to have more. As “unfair” as it sounds, a family could be better off if not every subsequent child reproduces. Nature is not fair to individuals; human culture needs the political will to be so.
A West Palm Beach FL television station WPTV picked up on the story, but then went off on another tangent about protecting the “religious rights” or people and counselors in the “ex-gay therapy” debate (as in California), piece by Gabe Lyons, here.
The epigenetics can raise another debate about ethics: the idea of expecting “differentiated sacrifice” among citizens in a democracy, as in the posting about the LDS teachings on Dec. 6. But this loops back into the observations already noted about birth order.
There’s an interesting question for sports, going back to Chandler Burr’s book “A Separate Creation” in the 1990s. Is there a connection between handedness and sexual orientation. Any connection and being able to switch-hit (or not to). It’s an interesting question for sports, because professional baseball, statistically, needs more left-handers and switch-hitters than pure right-handers.
National Geographic had a segment on epigentics and sexual orientation concordance among identical twins back in 2009, here. The video makes the interesting point that a fetus starts out female, and the hypothalnus presumes eventual attraction to males. It requires reception of testosterones specifically by catalysts in the hupothalmus to develop attraction to women. This may not happen all the time even when the rest of the body is masculine, even in identical twins, especially with latter-born sons.