Lafiel on 30 June 2010
The skin color adjustment happened, because when humans headed north they came into zones with less intensive sunlight, but light is needed to produce Vitamin D (very essential - btw the only Vitamin humans produce themselves ). So the skin color slowly changed to adapt to those lighting conditions, because people with lighter skin were more likely to reproduce.
And, there are no human "races". Humans are far too similar to each other to call the local differences a "race".
