The Evolution of Human Skin Colour | BBC Earth Science

This map shows how UV varies across the globe. >> Throughout Africa, there are these very high levels, but the levels taper off dramatically as we begin to get into Western Europe or Eastern Asia. >> And in places with less UV, high levels of melanin

created a problem. There are some wavelengths of UV that are actually essential to our health that promote the production of vitamin D in our skin. We need vitamin D for a strong immune system and

healthy bones. But with less exposure to the sun, our ancestors couldn't make enough of it. To survive in these new lands, our color had to change.

Nina has produced a map that shows how human skin color adapted. You see very darkly pigmented people that are concentrated in the areas of high UV and then much more lightly or depigmented people as you get closer to the poles

under conditions of very low UV. >> So each population works out a balancing act. So they they're protected enough that their DNA is okay, but they still have enough UV to make vitamin D. >> Precisely.

>> This interaction between our skin and the sun is so finely balanced that even in a single individual, it can adapt and change. To show us, Nenina is looking for the people with the biggest difference in color between parts of the body

that get a lot of sun exposure and parts that get very little. >> So, let's look here. Now, we don't see a lot of difference here between your upper inner arm and your forehead.

They're pretty closely similar. And with the two very lightly pigmented people, there's very, very little difference. And similarly, at the very other end of the line, with our most darkly pigmented person, there's very little difference.

>> But in the middle of the line, things are different. So if we look at some of these individuals, the difference is really quite great. The unexposed skin versus the exposed skin, we can really see a visible difference.

And all of these people have sort of moderately to darkly pigmented skin, and they have tremendous abilities to tan. >> Tanning is the solution to living at latitudes where sunlight changes dramatically throughout the year. In these regions, people produce melanin to protect them in

summer and then lose it in winter. All of this suggests a problem because today we jet all over the world. We live in countries which we weren't born in. Does that cause problems?

>> Now we have to modify our lifestyle. We have to think about whether we protect our our skin from ultraviolet radiation or whether we take vitamin D supplements. It's only recently we've been able to take measures like

this to help control our relationship with the sun. For most of our history, this vital role was played by our own skin.