Evolution of folded eyelids

Myth about double-eyelids, fat, cold in East Asia
There is a claim that excess fat in eyelids get rid of the crease & inward fold in the eyelids. (This claim needs a scientific proof & reference.) This is called single-eyelids or mono-eyelids. The folded eyelids are called double-eyelids. This fold is connected with eyelid muscles (levator palpebrae superioris) instead of fat. When there is excess fat & skin in the eyelids, this is called Dermatochalasis which is separate from mono-eyelids.
Quoting from UCHealth's article "what can doctors do to treat a droopy eyelid & brow?", "The dynamic movement of the upper eyelid depends on the skin above the eyelid being extremely thin (the thinnest of the body) and loose. With time this skin can stretch and hang over the edge of the upper eyelid. Additionally fat underneath the skin can protrude (especially fat pads in the inner upper eyelid) causing an abnormal puffiness to the upper eyelid. This extra skin and fat of the upper eyelid is termed "dermatochalasis."" The symptom is the eyelids hanging droopy, not turning into mono-eyelids.
There is a claim that excess fat is better at insulating in the cold. (This claim needs a scientific proof & reference.) Hence, body fat makes the body heat difficult to reach the body surface because the body fat is not outside the skin but inside.
There is a claim that double-eyelids don't evolve in the Northern cold. (This claim needs a scientific proof & reference.) Let's quote Livescience on the article "Why Did People Become White" on September 1, 2009. "The consensus among scientists has always been that lower levels of vitamin D at higher latitudes - where the sun is less intense - caused the lightening effect when modern humans, who began darker-skinned, first migrated north." Caucasians have double-eyelids & evolved in the Northern cold.
There is a claim that thicker skin is better in the cold. (This claim needs a scientific proof & reference.) Black people have thicker skin called dermis. Let's quote Livescience on the article "Why Did People Become White" on September 1, 2009. "Frostbite was another causal effect investigated by the researchers. Some reports from American soldiers serving in the Korean War and elsewhere have indicated that dark skin is more prone to frostbite than white because it emits more heat. In colder climates, evolution could have negatively selected for paler skin if frostbite was significant enough to perhaps kill darker-skinned children."
There is a claim that the term Mongoloid refers to only Mongolian, Eskimo Siberian, etc. (Such that "Chinese isn't Mongoloid".) The term refers to the yellow people in general. Also, Uralic, Turkic, Altaic blood is little in Mongolian. That blood (Y-haplogroup N) is genetically different from Eskimo Siberian (Y-haplogroup C). Quoting from "The Earth and Its Inhabitants" by Elisee Reclus, "The national type seems to have been best preserved amongst the Khalkhas, who also claim a certain superiority over the other branches on the ground that amongst them are the families of the Taitsi, descendants of Jenghiz Khan. Yet the Khalkha least resembles the typical Mongol type, as described by most ethnologists. He is rather brown than yellow, with open eyes, not inclined obliquely, like those of the Chinese or Ostiaks."

Main Menu

See Also

Main Menu