Johan Moan: Why Skin Colours Differ - Department of Physics. Uniwersytet w Oslo, 2011. Cytat: Some humans migrated eastward from Africa towards Indonesia, continually remaining in the tropics, and kept their dark skin colour. Others migrated north. This occurred several times, and each time their skin colour became lighter. This happened so that they would be able to get enough Vitamin D. White skin needs only one-sixth as much sun as black skin to make enough Vitamin D. (ang.).
