I wonder from where do we have so much evidence about what happened before "hundred institutions" existed. Cultural institutions predate writing and probably predate oral history, in fact many animals have some kind of social institutions. So if there was an "ideal man", uncorrupted by "institutions" (Dawkins would, I suppose, dislike that idea very much), certainly we have very little evidence about how that man could behave. But I think such man never existed - social institutions are part of what humans are, and always have been. That could be different - as many other aspects of humanity are varied and diverse - but they always exist.
I'm not in the mood for googling, so forgive my lack of sources, but by institutions I mean the catholic church, islam and others. We have plenty of documentation showing homosexuality to be common in ancient Rome and Egypt, and it is said that a word describing homosexual acts didn't even exist until the 19th century.
