When astronaut Scott Kelly returned to Earth after a year floating about the International Space Station, he was noticeably different from his identical twin, Mark Kelly. For one, Scott temporarily grew two inches taller, but what really fascinated people were the change in his genes. “There are over 50,000 genes in the human genome, and when floating in zero gravity, the body is trying to manage that situation in new ways,” Chris Mason, one of the principal investigators of the Twins Study and a geneticist at Weill Cornell Medicine, told PBS NewsHour. “Both DNA and RNA were found to express genes in order to compensate for a lifestyle in space.”
Which is really cool, and really important for long periods of space flight. Say, for example, to Mars…
Read about it here!
John Corvino, the chair of the Philosophy Department at Wayne State University, has recently published a book, What’s Wrong With Homosexuality, which systematically knocks down objections to the equality of LGBTQ folks. He’s been discussing major points from the book in a series of clever and widely-circulated videos, and I just recently discovered that, in an episode about the biological basis of sexual orientation, he talks about that review article proposing a possible epigenetic basis for sexual orientation that I discussed here a few months ago.
Full disclosure: I found Corvino’s post, actually, because he linked to my piece about the epigenetics paper, and he did so while paying it what I consider the highest compliment it’s possible to pay a science blogger: “A nice explanation of the paper can be found here.” Which: look at me blushing.
But Corvino comes at the question from a somewhat different angle than a biologist: he says it really doesn’t matter whether there’s an inborn basis to sexual orientation.
In the light of much of what we know about evolution, human homosexuality doesn’t make a lot of sense. Available data suggests that sexual orientation has some inborn, probably genetic, basis. But it’s hard to reconcile that with the fact that gay men and lesbians aren’t, by definition, particularly interested in doing what it takes to pass on any genes that might have contributed to creating their orientation. Natural selection is, all things being equal, pretty good at eliminating genes that make people less likely to make babies.
I’m gay. I’m also an evolutionary biologist. You could say this particular puzzle is tailor-made to attract my interest.
It turns out that there are a number of ways that human populations might accommodate gene variants for same-sex attraction without suspending the rules of natural selection. But it’s also possible that human sexual orientation has a biological basis without being genetic. Natural selection can’t do anything about a trait if variation in that trait isn’t linked to variation at the genetic level. So I was immediately interested by the recent announcement that a team of biologists at NIMBioS, the National Institute for Mathematical and Biological Synthesis, had found that human homosexuality is due not to genetics, but to epigenetics.
However, as soon as I secured a copy of the study itself (available in PDF format here), I was disappointed to find out that the reports of a solution to this particular evolutionary enigma are somewhat exaggerated. The paper doesn’t present any new data that directly links a specific developmental process to human sexual orientation — it’s a review article, gathering existing results in support of a hypothesis that isn’t, at its most basic level, entirely new. But it’s not the job of a review article to present new data; reviews are supposed to gather up what is already known on a topic and identify what new research could do to better answer the questions that remain. And that’s exactly what the new study does.