LIVE SCIENCE: Humans come in a rainbow of hues, from dark chocolate browns to nearly translucent whites. This full kaleidoscope of skin colors was a relatively recent evolutionary development, according to biologists, occurring alongside the migration of modern humans out of Africa between 100,000 and 50,000 years ago. The consensus among scientists has always been that lower levels of vitamin D at higher latitudes — where the sun is less intense — caused the lightening effect when modern humans, who began darker-skinned, first migrated north. But other factors might be at work, a new study suggests. From the varying effects of frostbite to the sexual preferences of early men, a host of theories have been reviewed. MORE