The distinctive shape of East Asian people's eyes is caused by the presence of a small flap of skin between the nose and the eye called the epicanthic fold. This fold is present among most people of East Asian descent and has been explained as an adaptation to arctic conditions such as high glare and cold winds, according to Dr. Frank Poirier of Ohio State University.Continue Reading
Unfortunately for this explanation, as explained by Dr. Poirer, many modern East Asian populations evolved away from arctic or tropical conditions, making the arctic-conditions explanation a less likely cause for the presence of the trait. The picture is somewhat complicated by the prevalence of the epicanthic fold among individuals and populations whose recent ethnic history is not known to include recent East Asian origins. Epicanthic folds are commonly found among people of European, particularly Irish, descent; President John F. Kennedy, for example, had a variation of the structure himself.
In addition to the various racial groups for whom it is common, many humans have an epicanthic fold early in life, according to MedLine Plus. This feature, which can sometimes be diagnostic of Down Syndrome and fetal alcohol syndrome, usually recedes as the bridge of the nose begins to rise.Learn more about Human Anatomy