The other night I watched a very interesting segment on 60 Minutes regarding the origin of homosexuality. While I think they unnecessarily dismissed the nurture hypothesis, they did raise some interesting aspects of current research. If the research is moving in the right direction, it may be the case that both "nature" and "nurture" are insufficient answers.
One of the most interesting avenues of research suggests that, statistically, the more older brothers a male has, the more likely he is to be gay. You can read the article to find out why scientists think that's the case.
(Please note that I post this without firsthand knowledge about the subject. If any of the diverse blog readers out there have knowledge about the nature of this research, feel free to weigh in.)
From a Christian worldview, it doesn't really matter the precise secondary causation of homosexuality (whether that be genes, hormones, absence of fathers, etc). Like other distorted desires, the focus must be on the sin itself and not where it came from.
Though I have not yet read it, I'm told that this book by Stanton Jones and Mark Yarhouse is the best book yet on the use of scientific research on the origins of homosexuality:
Homosexuality: The Use of Scientific Research in the Church's Moral Debate
