How can natural selection explain the world distribution of human skin color before the age of modern travel?

how can natural selection explain the world distribution of human skin color before the age of modern travel?

How can natural selection explain the world distribution of human skin color before the age of modern travel?
Look at the climates that various ethnic groups originated in and the corresponding skin colours. Those from northern climates tend to be paler - less sunlight equals less pigment, because it isn't as necessary to protect from ultraviolet radiation. In warmer or hot climates, skin colour tends to be darker to stop ultraviolet radiation from penetrating past the skin (the pigments in the skin absorb the light before it can reach and damage DNA).
Reply:People with darker skin absorb less of the sun's energy and have less adverse effects from the sun, such as burns, skin cancer, etc. Thus, people with darker skin were healthier and mated more, spreading dark skin genes to their ancestors. People in cold, less sunny climates need to absorb more energy from the sun, so having light skin would have been an attribute in colder climates. This would cause lighter skinned people to be more successful and have more offspring. Differences in climate can also explain why people have different body types. Someone in Africa would be better off with a tall, thin body because there would be less surface area for the sun to hit and no excess fat to make them overheat. Likewise, someone in Alaska would be better off with greater surface area to absorb the sun's rays and more fat to insulate them from the cold.