ASK A SCIENTIST
Question: How do we get the skin color we are born with?
Answer: One of the most obvious differences that we notice about people we know or meet for the first time is their skin color. Some people have very dark brown skin while others have skin that is so pale it looks pink. People around the world range between these two levels of skin color. The color of a person's skin comes from a number of chemical pigments in our skin and from the color of blood showing through the skin. The most important pigment is called melanin. This is a brown pigment that protects the skin from damage from the sun's rays. One kind of ray or form of radiation from the sun is called ultraviolet radiation, and this can produce dangerous sunburn and sometime even kinds of cancer. If you have a lot of melanin in your skin (dark brown), you can spend more time outside in bright sunshine without damaging your skin than a pale person can. This gives a real advantage to people who live in the tropics where there is a lot of bright sunshine. They can work outside for most of the day without damaging their skin with ultraviolet radiation. Because of this, most peoples who live in the tropics (India, Africa, New Guinea, Southeast Asia, and other places) have darker skin (more melanin) than those who live further from the equator in Europe, Asia, and the Americas.
In these more temperate and cloudy areas, such as New York State, people need less melanin because they are exposed to less bright sunlight. Another important factor contributing to skin color variation in people is the way that skin can manufacture vitamin D. Vitamin D, which is very important for the growth of bones in children, is produced in the skin when sunlight (ultraviolet radiation) changes chemicals in the skin and manufactures vitamin D. If there is too much melanin in the skin and too little sunlight, then not enough vitamin D can be produced. If there is not enough melanin in the skin and too much sunlight, then the skin is damaged. In this way, a balance is struck between sunlight around the earth and how much melanin people have in their skin.
Now the next question is: do we inherit our skin color and can we change our skin color? The answer is yes to the first part and generally yes to the second part. We inherit the ability to have either some, a moderate amount, or very much melanin from our parents. But we also have the ability to increase our levels of melanin in the skin by gradual exposure to the sun. This produces what we call natural tanning. Tanning is a way to deal with the seasons - cloudy and cool in the winter and sunny and warm in the summer. This allows us to adapt to the changes in sunlight throughout the year to both protect the skin and to allow it to produce vitamin D. Some people, however, go to 'tanning parlors' or spend long hours in the sun which can produce serious skin damage. Slow natural tanning is beneficial, but rapid and intense exposure to ultraviolet radiation can be harmful. Exposure to the sun is particularly dangerous for people with red hair who usually have very little ability to tan.
The final question might be: how did we get to be the way we are? The answer is that with humans living all over the world, darker-skinned individuals were better able to live and thrive in the tropics and lighter-skinned individuals were better able to live and thrive in northern zones. It is really not quite this simple, since people move around and there are many other things than sunlight that influence the way we are. But humans live all over the planet because they have this marvelous ability to adapt to all the environments in which they live.
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