Some believe that the Chinese eyes developed from their ancestors having originally lived in a very cold climate, which gave rise to a layer of fat being developed in the upper eyelid to protect the eyeball from cold. This feature can also be seen in Eskimo peoples, and it determines the shape of their eyes. It's thought that the Afro nose was the original normal shape, but as people migrated north to cooler climates, (the so-called temperate zones), the Caucasian nose developed, allowing inhaled air to be warmed for longer before being drawn into the lungs. But if the climate was colder still, (Arctic), noses of shorter length were again necessary, in this case to guard against frostbite. Hence the short noses of Eskimos and Chinese, and added evidence that the Chinese could be of far northern ancestry.