Question: Can you explain the genetics and evolution of skin color? Is skin color useful for grouping people into ethnic groups?

Stuart Archer answered on 21 Jun 2013:

Hi, really good question! You’re right to say that skin colour is very much a genetic trait, related to the areas of the world where particular groups of humans first settled and evolved. The leading theory is that darker skin tones evolved as a result of humans losing their body hair (compared to chimpanzees) about 2-3 million years ago. The lack of hair meant that our skins were exposed to much higher levels of ultraviolet radiation, which given we are thought to originate in Africa as a species, there would be plenty of sun to worry about! Those humans with darker skin were more likely to survive and pass on the trait to their descendants. As we migrated north into Europe and other colder climates, the selection pressure to keep the dark skin was not as strong, hence the paler skin colour of people in colder, less sunny climates.

It can be useful for determining the ethnic origin of someone, however within a region there are much more subtle variations, such as eye shape, nose shape, face shape and a whole host of other things that can tell you more about someone’s ethnic background.