Biology Forums - Study Force

Why different skin colors may have evolved?

It is pretty obvious that people whose ancestors come from Northern Europe or Japan tend to have lighter skin than people whose ancestors are from sub-Saharan Africa or Australia. The reason for these differences may have to do with the amount of sunlight in each place.

Sunlight can be pretty dangerous stuff because of its ultraviolet (UV) light. UV light can do things like destroy folic acid or cause changes (mutations) in the DNA of some skin cells. Sometimes, these mutations can lead to skin cancer.

So darker skin is helpful when there is a lot of sunlight. But sunlight isn't all bad. Sunlight can help our bodies make vitamin D.

Everyone needs vitamin D and you have probably seen it in things like your milk. When we don't have enough vitamin D, it can cause problems with your bones. Vitamin D deficiency can cause things like rickets or osteoporosis. It has even been linked to some types of cancer.

When our skin gets UV rays from the sun, our bodies use the UV light to make vitamin D. But melanin in our skin acts like a filter, making it harder for people with more melanin (darker skin) to make vitamin D. This means that the more melanin you have, the more sunshine you need to make enough vitamin D.

Imagine you lived somewhere cold and dark. Your skin wouldn't see much sunshine. How would your body get enough sunshine to make all of the vitamin D you needed? Well, if your skin had less melanin (which would make it lighter colored), then you would need less time in sunshine to make enough vitamin D!

So it's possible that lighter skin evolved so that people in darker places were able to get all of the vitamin D they needed to stay healthy (and have kids). So the skin color you have might be a result of how much sun your ancestors got!*

Now we know that skin color is just a matter of how much melanin you have. The versions of the skin color genes tell your body how much melanin to make. All of this means that the difference between dark and light skin is only a few changes in DNA!