How did we get our many different skin tones? To answer this question, we must consider some milestones in human history and that will help us unlock how people evolved to have a variety of skin tones. That story takes us to equatorial Africa, the site of origin of modern man with dark skin. How some people got their dark skin goes back even further in our evolutionary history. Although we have no past descriptions of old human skin, and we have no frozen samples from our distant past, we can still uncover that story by comparing ourselves to our most closely related primate.
Chimpanzees live in the cool forest where the tree canopy and their body hair protect their light skins from ultraviolet radiation. When a group of these primates were forced to leave the shrinking forest due to global warming, they took to the open savanna in search of food. Adjusting to life in the savanna led to walking upright for a longer gaze and for better awareness of predators in the savanna. The transition to upright posture occurred about 5 million years ago. Living in the hot savannas of Africa led to a loss of body hair to keep cool. This occurred about 1.2 million years ago.
In other words, to better regulate body temperature in the hot sun, these primates had to lose the blanket of hair that previously protected them from radiation. Specialized skin cells that once emptied their pigment into the hair to give it its color, would now empty their sun protecting pigment directly into the skin to give it the protection that the hair once offered. Life for a naked primate also required the evolution of sweat glands that would allow water to be poured on the skin to cool overheated bodies.
Since humans evolved from light-skinned primates with dark hair, our skins carry a record of that history in its genetic code. In 2017, Dr Lopranski’s team examined 1600 Africans and found that they carry the genes for making both light and dark skin. Over time, various mutations have occurred within these genes affecting their expressions in different populations. The physical evidence for the fact that dark skinned Africans have retained the genes for light skin can be seen in the colors of the palm of their hands and soles of their feet. It can also be seen in the color of their inner cheeks and eyelids. All these areas are not sun exposed and have retained their light complexion as they do not need protection from ultraviolet rays. Similarly, their newborn children are light skinned because in the womb they did not need sun protection.
While people have a wide range of skin tones not all colors of the rainbow are featured as colors of our skin. There are no green people and no purple people. Our skin tone ranges from brown- black to yellow- red. Africa is the continent that best displays the range of human colors possible. It is on the African continent that skin tone varies the most and ancient Africans are the ancestors to all people around the globe. Darkly pigmented people from Asia and Australia carry the same genes active in making Africans dark-skinned. This genetic evidence is consistent with the fact that they are of the African diaspora and retained their dark skin due to their location. Light-skinned people living in cold climates also inherited their light skin from the African light-skinned genes but with some modifications from more recent mutations. No matter the color of our skins, we are still one African family, one human race.
In the Kingdom of Dahomey, light-skinned people were called red people and dark-skinned people were called black people. That description is in fact more correct than racial classifications that mischaracterized the human species as belonging to discrete blocks when indeed our skin color is part of a continuous range of colors that changes gradually across the globe. There are no dividing lines in the world where one kind of skin tone ends, and another begins. If in defiance of nature, one were to arbitrarily place such a line, then people on either side of the line would appear indistinguishable because of how gradual skin tones change with latitude.
Some Africans may have more appropriately categorized skin tones as various shades of brown and black or yellow and red because they reside in a region where people often encountered others with this range of skin tone. In other words, people on the African continent got to see a microcosm of global skin aiding them to distinguish the range of human colors more appropriately.
Nowadays, we know that there are many genes influencing skin color accounting for the wide range of possible human skin tones. Among these many genes, the ones with the biggest impact are those that regulate the production of pigments called melanin. There are two types of melanin: eumelanin, the black brown pigment and pheomelanin, the yellow red pigment. Dark-skinned people produce more eumelanin and less pheomelanin. On the other hand, light-skinned people produce more pheomelanin and less eumelanin.
Just like the other primates secrete melanin into their hair, we humans do the same. The kind of melanin most secreted in hair is eumelanin. Other components of the hair mixed with the eumelanin gives its final color. Blond people also secrete eumelanin into their hair. Those with red hair are the only people who secrete pheomelanin into their hair.
People who do not produce melanin because of impairment of melanin production are called albinos. The impairment may affect their skins, their hair or both. Lacking melanin makes albinos susceptible to premature death by diseases caused by exposure to ultraviolet radiation.
The melanin pigment that colors our bodies is made from skin cells called melanocytes. The concentrations of melanocytes in human skin is constant in different populations around the globe. It is the quantity and the ratio of eumelanin to pheomelanin that varies in different locations giving the color of human skin its wide range.
The pigment making cells are in the bottom layer of our skin. The melanin produced by the melanocytes is carried to the top layer of the skin. For this reason, skin color is limited to the upper portion of the skin where it is needed to protect the rest of the body from ultraviolet radiation. As skin color is limited to the surface of the body, once one passes the skin during surgery, no additional distinction in color is seen within the bodies of people from different regions. The reality is that differences in human color is only skin deep.
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