The Color Of Man (1955)

[Music] Modern forms of transportation permit travel to any part of the Earth's surface. But this has not always been true. For most of human history, our movement was confined to small areas, natural barriers. [Applause] [Music] During those thousands of generations, many differences developed. In this film, we are dealing with differences in color. The color of our skin is due to the presence of small particles of a chemical called melanin. Because the amount is different in each of us, our skins appear to have different colors. The ability to produce melanin is hereditary. Compared to other hereditary differences, it involves only a few gene pairs. Because of this, people with different color skins may be more alike genetically than those whose color is the same. The production of melanin is stimulated by the ultraviolet radiation that reaches us from the sun. A short exposure to these rays will bring out hereditary differences previously hidden. The melanin particles protect us by absorbing the ultraviolet rays before they can injure the sensitive under layers of the skin. Those who lack the hereditary ability to produce enough melanin may be painfully burned. As the Earth curves away from the poles, the same amount of sunlight is spread over a smaller and smaller area. This increases the ultraviolet intensity as we get closer to the equator. [Music] Many of our ancestors lived in these areas where the radiation is very intense all year round. Those who couldn't produce enough melanin suffered from sunburn and skin disease. Wild game was the main source of food. The intense sunlight made hunting difficult for those with light skin and eyes. The absence of melanin particles allowed the sunlight to leak through the iris and reflect off the retina inside the eye. [Music] Darkeyed people could see more clearly because the melanin in their eyes stopped most of the glare. [Music] These and other factors gave people with dark skin and eyes a better chance to stay healthy and have more children. After more than 100,000 years, the only people who survived in these areas had very dark skins. [Music] In the rainforests of the north, there was very little ultraviolet for most of the year. The tall trees and thick clouds stopped so much of the sunlight that not even a thin melanin layer was necessary for protection. Vitamin D is produced by the action of ultraviolet rays on certain chemicals in the skin. People who don't get enough of this important vitamin suffer from ricketetts and other diseases. In the equatorial areas, there was so much ultraviolet that enough got through even the darkest skin to produce the vitamin D that is needed. But in the northern rainforest, there was so little ultraviolet that only very light-skinned people could get enough vitamin D to stay healthy. Thousands of generations have passed. The descendants of these forest peoples are still very light-skinned. Even today, in many of those areas with the strongest ultraviolet, we still find the darkest peoples. There are exceptions. Eskimos and American Indians have different color skins than their areas seem to call for, but their arrival in the Western Hemisphere dates back only to the end of the last ice age. This period of 20,000 years is too short to have produced a change. These examples were caused by extreme conditions. Between them, there are infinite degrees of shading. [Music] [Applause] Today, protective clothing has weakened the selective power of the environment. Even in the most extreme climates, we no longer need to adjust to different amounts of ultraviolet through hereditary traits. As science brings us closer together, an understanding of these small differences can allow us to realize more fully our basic similarities. Variations in color demonstrate man's ability to adapt to the forces of nature. An adaptability which has enabled us to emerge victorious in the struggle for survival.