Since I had read so much science-fiction as a kid, I felt pretty cocky when I added the H.G. Wells novella The Time Machine to my summer reading list. The very first sentence sent me to a dictionary to look up an unfamiliar word...
Anyway, the Time Traveller travels 800,000 years into the future and meets the eloi. These descendants of modern-day humans are all 4 feet tall and androgynous. The loss of sexual dimorphism in humans transformed this SF tale into a horror story for me ;-)
Update (8/2) - In the recent movie adaptation, the eloi Weena is decidedly non-androgynous. This reinforces my view that movie adaptations of books should be considered on their own merits.