Why do oriental and occidental eyes differ?
The question I think you are trying to ask here, J., is what the function is of the "epicanthic fold," the extra flap of skin that gives orientals a sort of double upper eyelid. Anthropologists aren’t sure, but their best guess is that it’s an adaptation that protects against cold and glare. The theory is that the people who eventually became the Mongoloid race were trapped in Siberia by the glaciers during the last ice age, from 50,000 to 25,000 years ago. During that time, when life was truly survival of the fittest and evolution was rapid, the proto-Mongoloids developed a number of physical traits that helped them cope with the bitter weather. For one thing, their noses became flattened, which minimizes exposure to the elements and thus reduces the risk of frostbite. The nostrils got narrower, enabling inhaled air to be warmed up more efficiently and preventing cold air from reaching the lungs. Their faces gradually became round and flat and lined with fat, which acts as an insulator. The eyelids picked up a layer of fat as well, and I suppose without an epicanthic fold they might be a bit difficult to open and close.
Then again, maybe the whole thing was just an accident. Life is like that sometimes.
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