Re: homosexuality is it just......
Well, Numinous, I may argue that since all development begins normally and only when the Y chromosome kicks in does "maleness" developed and that if, for whatever reason, the Y chromosome fails to activate or is not present (the XO genotype) the phenotype is female, that the default (in humans) is female, so we all begin to develop as a female does.
Of course, that's being very broad and your point of the early stages of development are, for the most part, sexless, is well taken.
HR - homosexuality is genetic, because all things are genetic. Why, what causes it and exactly how it beneifits a species to have it, is still unknown and some rather touchy questions to get into. (I'm quite certain the gay community will be happy for proof that they are genetically natural but will quail at the idea of describing it fully for the potential genetic "therapies" that could arise to remove it from unborn children - of course, just one of the many issues our growing genetic species will have to wrestle with.) I theorize that it is a genetic phenotype that arises during times of oppulance for a populace, where there is either no true pressures of species survival due to lack of mating or, in extreme, a behavioural shift due to lack of females (everyone needs some love). A common citation of common and accepted homosexual practices is Rome, the previous height of civilization which has only recently been surpassed, and the species examples are generally in very stable and relatively untroubled populations - often birds and monkeys.
It's amazing to me that, unlike in the real world, people on the internet will wear "everyone thinks I'm a moron" as a badge of honour.