If too much exposure to the sun causes cancer, how are there still any fair-skinned people on earth? For the vast majority of human history, we didn’t have sunblock. Shouldn’t we gingers be extinct by now?

Question

If too much exposure to the sun causes cancer, how are there still any fair-skinned people on earth? For the vast majority of human history, we didn’t have sunblock. Shouldn’t we gingers be extinct by now?

In: Biology

Answer 1

Take a look at this map

http://www.thewhirlingwind.com/wp-content/uploads/2013/07/Map_of_Indigenous_Skin_Colors.png

This is a map of the world colored based on the average skin tone of the people native to that area. As you can see, how dark your skin is is more or less just a function of how far away you are from the equator. Fair skinned people, for the majority of human history, lived in areas that didn’t get much sunlight. The lighter skin was actually an advantage because it’s better at absorbing vitamin D, which would have been in shorter supply. Fair skinned people didn’t venture out of those areas in large numbers until relatively recently. So there wasn’t a lot of time for natural selection to take over and weed people out. And since we spend more of our time in doors and have access to things like sunblock, the evolutionary pressure isn’t as strong as it would have been tens of thousands of years ago.