Step-by-step explanation:
The range of skin colors in humans evolved at different times, in different populations, as humans spread throughout the world.
In fact, studies of the human genome suggest that there are a number of genes that affect human skin color in specific populations. In particular, research shows that different populations have different allele frequencies of these genes, and it is the combination of these allele variations that causes the complex and continuous variation in skin coloration that we can observe today in humans. modern.
Now, regarding the evolution of skin color, it is known that all modern humans share a common ancestor who lived about 200,000 years ago in Africa. Comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and that this common ancestor had dark skin. The evolution of light skin has followed different genetic paths in European and East Asian populations and this is due to mutations in genes responsible for the production of different types of melanin. These mutations are believed to have originated after humans left Africa, but before the divergence of European and Asian lineages about 30,000 years ago.
Now, It is believed that due to these mutations there was a strong positive selection (a selective sweep) in the first hominids. And in this respect researchers believe that human populations over the last 50,000 years have changed from dark to light-skinned and vice versa as they migrated to different UV zones and that such major changes in pigmentation may have occurred in as little as 100 generations through selective sweeps.
We can conclude that the correct answer is:
Answer:
The evolutionary process from dark skin to light skin (pink) is believed to have been as follows:
1. The human body needs certain levels of vitamin D for the correct absorption of calcium and phosphorus and the proper formation of bones, for which a little ultraviolet radiation must affect the skin, forming pre-vitamin D3.
2. In Africa (the original continent of our species), the amount of ultraviolet solar radiation must be neutralized with a pigmentation with a high content of melanin to avoid the negative health effects of such radiation. Most of the ultraviolet radiation is absorbed by melanin and a small fraction is used for the synthesis of vitamin D.
3. When a highly pigmented human group tries to colonize an area of the globe where the incidence of ultraviolet radiation is much lower, the little amount of ultraviolet radiation that reaches those latitudes is blocked by melanin, and vitamin D could not be generated. Therefore, there would be little or poor absorption of calcium and phosphorus and people would suffer from rickets. The emaciated women would have poorly developed pelvises and they and their young would die more easily in the birthing process. Therefore, natural selection would end up eliminating dark-skinned humans in places with little ultraviolet radiation, favoring light-skinned mutants.