How did they lose the Asian snow flap on the eyelid so quickly if they are truly Oriental?
I have noticed that the eyelid shape for American Indians can vary depending on the geographic area of the tribe.
The epicanthic fold.
Not all Asians have it. Some have it and it is very pronounced--they appear to have slits for eyes. Others (Japanese, many of them) have round eyes like we do. Asians vary.
Theory I read is that the epicanthic fold came about because the Himalayas run horizontally, not vertically like the Rockies. People got trapped on the north side of the Himalayas during the last Ice Age, and the fold exists to prevent the eyelid from freezing shut.
Interesting, either way. Good post, fun discussion.