Why did certain races develop epicanthic folds?

Question

yeah but arabs don't hav'em

Answer 1

To protect the eyes from constant blowing winds and sands on the central plains of Asia.

You have better answer?

Arabs never evolved in central Asia.

Answer 2

The current accepted explaination is this is a cold adapted evolution that reduces loss of heat around the eyes.  Some "suspect" this is "gene introgression" from Homo erectus, as is the wider & flatter face accross the cheek bones.  Below the neck the H erectus is almost identical to Homo sapien & the more modern H. erectus found in Asia rivals H. sapien in brain size.

Answer 3

I have to disagree with the cold theory. An epicanthic fold is the norm for all human foetuses in the early stages of development. The oldest human population the Khoisan have them, and this eye shape appears in some of the isolated groups like the Andaman islanders as well as the Mongoloids. It's possibly just an easy mutation for humans to acquire, or it may have been the norm for the very first hominids. The fold does force the eyelashes down somewhat, and makes a kind of dust filter to protect the eye.

Answer 4

Ed probably got it right.  It is an extra layer of fat to protect the eyes from cold.  Apparently, they developed to protect the eyes from the cold of the Tibetan highlands.  Other features such as black hair protect from the intense UV radiation in the high elevations.