Bill Nye went viral with a Tik Tok video showing that humans are descendants of Africa, and he explained how skin color is affected by how ultraviolet light lands in each latitude on each continent.

Bill then explained that the closer you are to the equator, the more your body takes the ultraviolet light, stating:

“Our skin is where we make vitamin D; if you don’t get enough ultraviolet, then you don’t get enough vitamin D. But if you get too much ultraviolet, then you break down your folates. You have to have it in perfect balance. And because the ultraviolet varies, the color of our skin varies. And that’s it, everybody! That’s why we have different color skin!”