Final answer:
Darker skin colors occur in areas closer to the equator, where there is a higher intensity of sunlight. Lighter skin pigmentation became advantageous as populations moved away from the equator to regions with less intense sunlight.
Step-by-step explanation:
When considering the distribution of skin color among populations who have lived in an area for many thousands of years, we find that the darkest skin colors occur in areas closer to the equator, where there is a higher intensity of sunlight. This is because darker skin pigmentation provides protection against the damaging effects of the sun's ultraviolet radiation. As populations moved away from the equator to regions with less intense sunlight, such as northern Europe, lighter skin pigmentation became advantageous as it allows for better synthesis of Vitamin D from sunlight.