Human Variation and Adaptation to Different Environmental Conditions
Many questions have been asked about human variation and why populations differ from one another. Some of the more obvious differences like skin color and body types gives rise to questions like, "Why does this happen?" and "How does this happen?". There are many other differences in human variation that may not be as noticeable. One of the biggest causes for human variation could be climate fluctuations.
Many paleoanthropologists, those who study evolution, believe there are a variety of ways the environment has encouraged variation in humans. Could climate be the reason for variation in human noses? In Germany, researchers examined different nasal cavities in 100 human skulls in 5 different climates. "They found that the nasal cavities of cold, dry climate populations are relatively high and show a larger and more abrupt change in diameter in the upper part of the cavity than those of hot, humid climate populations."
(Raymond). This information does support the idea that human variation in noses could be caused by the adaptation to the climate that they lived in. The hairs within the nasal cavity also plays and important role because some environments may be dustier than others. These hairs help keep dirt and pathogens from entering and infecting the lungs. Heat and moisture are also important are also important for respiratory health in colder climates. "Cold, dry climate populations also show a relatively longer nasal cavity, giving this population more space in which to bring incoming air in line with body temperature." (Raymond).
Another human variation that has scientist wondering if climate was an effect is the epicanthic fold. This distinct fold in the eye has a high concentration in certain geographical areas. It is sometimes refers to as the "Mongolian eye fold" because it is largely found near the continent of Asia. The epicanthic fold fuels many controversies because of its existence. "In addition, epicanthic folds in individuals of groups without a high normal incidence of its presence is often phenotypic of genetic or congenital disorders. In some recent debates, the alleged absence of the fold in some depictions and descriptions of humans from Chinese and Indian history has led some Afrocentric historians to claim an African origin of at least some aspects of Indian and Shang dynasty Chinese culture." (JENNETT). These assumptions can lead scientists to believe that due to human migration it created diversification in eye shapes. Genetic mutations, such as Down's syndrome, also shows the presence of the epicanthic fold. Because of this genetic mutation it is hard to tell if the lack of or presence of the epicanthic eye fold is due to any kind of climate adaptation. The development of the epicanthic fold is still a mystery.
By looking at two small differences in human variation it can be seen the climate and sexual selection have an impact. Genetic drift helps spread the variations within humans. Evolution is inevitable. With certain genetic mutations being constant, human variation will continue to happen. The more variation a species has the greater the chance for survival. It is known that certain mutations can help humans survive some environmental tragedies, such as diseases like malaria. Even simple variations like body size can help humans survive certain environmental conditions. Due to today's technologies it is sometimes forgotten why human bodies are different.