Eyes are the most beautiful part of the human body and it differs from person to person. Not just in terms of color but also in terms of shape and size.
Have you ever wondered the reason behind the difference of eyes in terms of shape and size? Here's why.
That distinctive Asiatic eye look is caused by a variety of things, including strong, forward projecting zygomatic arches, relatively large epicanthic folds, smoothness caused by fat around the eye socket, and a flatter nose bridge. Not everyone has all of these traits, or has them to the same degree, but these traits all tend to reinforce each other visually, leading to a distinctive effect.
Have you ever wondered the reason behind the difference of eyes in terms of shape and size? Here's why.
That distinctive Asiatic eye look is caused by a variety of things, including strong, forward projecting zygomatic arches, relatively large epicanthic folds, smoothness caused by fat around the eye socket, and a flatter nose bridge. Not everyone has all of these traits, or has them to the same degree, but these traits all tend to reinforce each other visually, leading to a distinctive effect.
In theory, these effects are presumably caused by a combination of continentality and sexual selection for neoteny. The exact way this happened is still the subject of some controversy, but the correlation is well established.
The story goes that ancestors of the Asiatic peoples (that is, the people who live in modern day East Asia) migrated, in prehistoric times, from somewhere around Central Asia or Siberia to their current locations. That area is the place on Earth which is the farthest inland, and as a result experiences large seasonal swings in temperature. They would have adapted to deal with dry, cold winters, hot, bright summers, and dust. They would have had to deal with dust in the summer and glare from sunlight reflecting off snow in the winter, under conditions where survival was fairly difficult.
If environmental effects were all that mattered, moving south-east like this would have resulted in these Asiatic people losing their distinctive features as an adaptation to their now more temperate environment. But that wouldn't be instantaneous and environment is not the only factor in play. When these prehistoric Asiatic people reached more temperate and coastal areas, which were capable of supporting a larger population, they underwent a population explosion, which allowed sexual selection to take over. The Yellow River Civilization, for instance, which is the ancestor to the modern nation of China, had a relatively high population for many thousands of years.
Sexual selection is a mating preference. That is, cuter people (as judged subjectively by the pool of potential mates) are more desired as reproductive partners and therefore are more likely to pass on their genes. Social selection in connection with infanticide in times of famine might also have played a role.
So we can say that features which originally arose as adaptations to an extreme, dusty climate were probably exapted through sexual selection.
