Any Darwinians want to explain “natural homosexuality”?
When a significant portion of your ability to reproduce is determined by your position and function within a complex social order, really weird social and physical characteristics can be selected for.
A simple example is the peacock - sexual selection favors longer, brighter tails, while predation selects against longer, brighter tails.
This is consistent with seeing homosexual behaviors primarily in highly social animals. It will change between every species and social order... but I recall a primate study where they documented homosexual relationships in males. What would happen is that two males would engage in homosexual activity, including courtship and sex, and become very strong protectors of one another. In some cases, one of the males would challenge the leadership of the group and it was almost always necessary for him to be backed up by his partner. The leadership position then yields him and his #2 the best and choice access to all the females of the tribe. Hence, it's feasible this kind of behavior could have a selective advantage in that social structure.
You can find alot more case studies and references
here.
Given the prevalence of homosexuality in other ape species, its suggestive that it may be more genetic than a lot of people here would like to admit. I took a look at a bunch of twin studies and kept seeing data that looked like:
General Population: 1-3%
Concordance of Siblings: 10%
Concordance of Fraternal Twins: 10-20%
Concordance of Identical Twins: 30-50%
which means you're 20 times more likely to gay if your identical twin is. This translates into homosexuality being something like 45-65% genetic. How or why is an entirely different question which is undoubtedly some very subtle aspect of our ancestral social structure... not unlike the other ape case studies.
Any Darwinians want to explain “natural homosexuality”?
There's no definitive explanation that I know of. But if you look at the role of self-negating behaviors, like sacrificing yourself to save your group(i.e. sheep bellwethers, prairie dogs), in the evolution of social animals, it's perfectly reasonable to assume that homos are beneficial in a social hierarchy, ensuring the propagation of people that are related to them(thereby increasing the spread of homosexual genes).