Well, David, this may shock you but I'm in an argumentative mood. Evolution is about passing one's genes on to future generations. If you are engaging in homosexual sex you are separate and apart from evolution as your genetic material cannot possibly be passed on, unless you are also in a hetro-sexual relationship. There is mounting evidence that sexual preference is a genetic predisposition. Nonetheless, homosexuality cannot possibly have any evolutionary advantages as there can be no advantage to a evolutionary strategy for genes are not passed on to future generations of humankind.