Question

Tens of thousands of years ago, the first humans left Africa and started moving north. These people had dark skin. So how, over the course of hundreds of generations, did light skin come to predominate in the north?

Answer 1

The transition from dark to light skin pigmentation in humans as they moved north from Africa is an evolutionary adaptation to varying ultraviolet radiation levels. Lighter skin became advantageous for vitamin D synthesis in areas with less intense sunlight, leading to its predominance in northern regions over time.

Step-by-step explanation:

Adaptation of Human Skin Pigmentation

The transition of skin pigmentation from dark to light as the first humans moved northwards from Africa is an evolutionary adaptation to varying levels of ultraviolet radiation. Early humans who left Africa and settled in Europe had dark skin, which protected against high levels of ultraviolet radiation near the equator. However, as their descendants moved further from the equator, there was less sunlight and thus less ultraviolet radiation. This shift meant that individuals with lighter skin were at an advantage because they were able to synthesize more vitamin D in areas with less intense sunlight. Over thousands of years, lighter skin began to predominate in the north due to natural selection favoring these traits for survival in those environments.

Moreover, skin color varies gradually along a spectrum with no distinct boundaries between groups, reflecting a gradual adaptation as humans migrated over long distances. The historical migration patterns of humans show a correspondence between distance from the equator and variations in skin tone, thus explaining how lighter skin became more prevalent in the northern regions.