Skin pigmentation, or the color of our skin, is the result of the melanin in our skin cells as well as genetics. Although the genetics are responsible for similar skin colors across a local population, the evolutionary causes are not completely understood.
A wide range of genetic and environmental factors are believed to be behind the various colors of human skin, and there are many things, both natural and man made, that can alter the color of an individual’s skin. Natural factors such as aging, genetic abnormalities (such as albinism), and exposure to the elements (water, air, light, etc.). Man made factors include routine tanning and exposure to chemicals and other substances.
It is theorized that at one point the human species shared a very similar skin color across its entire population. This would be at a theorized time when civilization was concentrated around the equator. Differences in skin tones began to occur with human migration further and further north and south toward the poles. As people moved north, and there was less and less sun, dark skin became unnecessary as a natural protector from UV rays, and lighter skin humans evolved.
Melanin and Skin Pigmentation
Melanin is in control of how much pigment the body produces. Darker skinned races generally have more melanin than races with lighter skin, which results in the higher and lower pigment levels, respectively. Melanin is in turn produced by cells called melanocytes, which operate under genetic demands to produce red and dark brown melanin via the process of melanogenesis.
The genetic control over these two types of melanin is believed to be responsible for the extremely wide range of human skin colors that we see today. Because melanin is responsible for controlling the amount of ultraviolet radiation the skin absorbs, healthy levels of melanin are necessary to avoid complications that can lead to skin cancer.
Exposure to the sun produces Vitamin D, a much needed vitamin for overall health, as well as more melanin, so one must be careful to balance their exposure between what is needed to be healthy and an overdose that results in sunburns and other complications.
Although exposure to ultraviolet radiation can directly darken the skin, there is a school of thought that believes northern migration was not the only reason that humans began to develop lighter skin. Because melanin and pigment are responsible for the amount of sunlight absorbed into the body, and because our bodies convert sunlight into Vitamin D, a widely accepted theory proposes that lighter skin only came around when our diets no longer provided enough Vitamin D and more sunlight needed to be absorbed to balance the difference.
This theory asserts that with the onset and widespread use of agriculture, certain meats and plants that were rich in Vitamin D were removed from the common diet. With the decrease in Vitamin D through the diet, lighter skin evolved to allow more Vitamin D to be absorbed via sunlight.
The gene associated with light skin has only been found in samples dating back roughly six to ten thousand years, which is around when agriculture was beginning to dominate migratory hunting.
Age and Skin Pigmentation
As more melanocytes cease to function, less and less melanin will be produced, which is guaranteed to cause a change in skin color. Pigmentation on the face is particularly susceptible to change as we age, due to the high amount of exposure the face gets every day compared to the rest of the body compounding the lack of melanin.
The overall change in actual skin tone will most likely be gradual, therefore it is important to keep in the mind a growing susceptibility to the sun. Skin cancer and its potential complications becomes a much greater concern as one gets older. As at any age it is important to take care of your skin and be sure you do not allow yourself to be overexposed.
Albinism and Skin Pigmentation
Albinism, a congenital condition, is the case where an organism is born with either a total lack, or near total lack, of pigment in the skin. It has been traced to the absence of the copper containing enzyme tyrosinase that is needed by the body to produce melanin.
In the case of total lack of pigment the organism is known as an albino, an only partial lack results in an albinoid. Albinism has been seen to affect all vertebrates, not just humans, and is often accompanied by vision problems such as astigmatism.
Those affect by albinism are highly susceptible to sun burn and skin cancer. There is currently no method known that can reverse albinism, due to its genetic component. As far as vision disorders are concerned, glasses and in some cases surgeries are common, and effective, at correcting even severe cases of poor eyesight.
While skin pigmentation can be affected by a wide range of factors that are both out of and under our control, the purpose of pigmentation is solely to regulate the amount of ultraviolet radiation the body absorbs. However, the range of conditions present that have an effect on the color of one’s skin are as responsible for the color as one’s genetics, as anyone who spends too much time in or out of the sun will make obvious.
The important thing to remember is that no matter how much or how little pigment is in your skin, overexposure to the sun is never good, and keeping your skin healthy is a big part of making sure that there are no complications later in life.