How have historic levels of melanin in human populations change due to migration?
Historic levels of melanin in human populations have changed due to migration in several ways.
1. Migration to regions with higher UV radiation levels: People who migrated to regions closer to the equator, where UV radiation levels are higher, experienced increased selection pressure for higher levels of melanin in order to protect against the harmful effects of UV radiation. Over time, this led to the evolution of darker skin tones in these populations.
2. Migration to regions with lower UV radiation levels: Conversely, people who migrated to regions farther from the equator, where UV radiation levels are lower, experienced reduced selection pressure for high levels of melanin. This allowed for the evolution of lighter skin tones in these populations, as lighter skin is more efficient at synthesizing Vitamin D in areas with less sunlight.
3. Intermixing of populations: Migration has also led to increased intermixing of different populations, resulting in varying levels of melanin within certain groups. For example, populations that have migrated and intermixed with other groups may exhibit a wider range of skin tones due to genetic diversity.
Overall, migration has played a significant role in shaping the distribution of melanin levels in human populations, leading to the varied skin tones we see today.