How do the historic levels of melanin in human population change due to migration?
The historic levels of melanin in human populations have changed over time due to migration. When early human populations migrated out of Africa to regions with less intense sunlight, there was a selective pressure for lighter skin to allow for better absorption of vitamin D. This led to a decrease in melanin levels in populations outside of Africa.
Conversely, populations that remained in regions with high levels of sunlight, such as in Africa, continued to have high levels of melanin to protect against UV radiation. Over time, these populations developed darker skin pigmentation as a result of natural selection.
As humans continued to migrate and mix with different populations, there has been a continual mixing and reshuffling of genetic traits, including those related to melanin levels. This has led to a wide range of skin tones and levels of melanin present in modern human populations.