I don't know enough of the science. Do identical twins have exactly the same DNA? If so, then just using logic if you had any cases where one twin was homosexual and one was not, then you'd have to argue that none of those cases were genetic in order to preserve the notion that it's genetic. So I guess even identical twins where one is homosexual and one is not still does not prove that homosexuality is not genetic. The funny thing is that if there is a homosexual gene then natural selection seems to have failed. Unless the homosexual gene was passed down because the behavior was so frowned upon in the past, that they still participated in normal procreation to conform to normal standards. So actually, if the gene does exist, we should see homosexuality dying out since it it is now an approved behavior. That is homosexuals are no longer under societal pressure to procreate normally. Therefore, the prevalence of the gene should begin to fade. Hmm. Maybe I should be for gay marriage. The more they marry each other, the sooner they're gone. I guess the flaw in that argument is that many of them use their own genetic material to produce designer babies. So we'll probably see more homosexuals since the DNA is spreading using current reproductive technology.
I don't know that much science, either. I like reading about science and nature, but I'm no scientist.
Do identical twins have exactly the same DNA? If so, then just using logic if you had any cases where one twin was homosexual and one was not, then you'd have to argue that none of those cases were genetic in order to preserve the notion that it's genetic.
I don't think you could argue that. Nobody is saying it's 100% genetic. There are genetic factors that influence behavior, but they interplay with environmental ones.
One of the researcher teams quoted in the article was Peter S. Bearman and Hannah Brückner, to show that there wasn't a significantly greater concordance for identical twins than fraternal ones. But the team found an interesting wrinkle to this: Fraternal twins can be of the opposite sex. Boys who have a twin sister, it turns out, are twice as likely to be sexually attracted to boys, than one would expect. But only if they didn't have any older brothers! This argues that environmental factors are very important in developing sexual preferences.
Anyhow, the article is a bit underdeveloped, and the headline is wrong. Gays aren't "born that way" -- a lesbian says so: not quite. She was speaking for herself. Maybe she's bi; who cares?