I remember reading a book that was called Mass DReams of the future. It detailed hypnotizing people and bringing them forward in time to see what their dream archetypes were for the future....to 2100 and 2300. (this was done in the 80's)
Most people found themselves 'floating' ie: the population had decreased a lot, and there weren't that many people on the earth.
of the 5% population that was there, there were 2 main scenarios; people living in domes where the earth outside was inhospitable. and ecotopias where the land was lusch and groeen etc. (there were smaller subgroups of a mad max city scenario and a space station living environment.)

the point of this is; a small percentage identified in these futureist dream scenarios as a 'third gender', neither male nor female specifically, but perhaps both? it was say 5% of the population in 2100 and had gone up to 12%in 2300.

i feel like these transgendered people now, could be paving the way for a different kind of human to evolve in our species.