What factors influenced the preservation of the external appearance of some peoples?

The external environment greatly influenced the appearance of some peoples. What are the environmental factors? First of all, it is worth mentioning solar radiation. It is this factor that most of all affects skin pigmentation. The peoples who live near the equator have a characteristic skin tone. He is significantly different from the skin color of other people. Africans, for example, have deep, dark skin color. In Argentina, the shade is not so intense. But the peoples who live in cold climatic zones are distinguished by light skin.