Our lack of body hair and our variable skin color are some of the traits that set us apart from our closest primate relatives. Wavelengths of light are reflected or absorbed by pigment in the skin called melanin. Melanin is synthesized in structures called melanosomes that are produced by cells called melanocytes.
"Skin color is a classic variable trait in humans, and it's thought to be adaptive," Tishkoff said. "Analysis of the genetic basis of variation in skin color sheds light on how adaptive traits evolve, including those that play a role in disease risk."