Due to natural selection, people who lived in areas of intense sunlight developed dark skin colouration to protect against ultraviolet (UV) light, mainly to protect their body from folate depletion. Evolutionary pigmentation of the skin was caused by ultraviolet radiation of the sun. As hominids gradually lost their fur between 1.2 million to 4 million years ago, to allow for better cooling through sweating, their naked and lightly pigmented skin was exposed to sunlight.