In the earliest parts of the slow evolutionary process of human beings, the first people on Earth, often called the proto-men, originated in Africa and had black or dark-colored skin. After millions of years of further evolution, the proto-men eventually became true-men, which are considered as the Homo sapiens, the final evolution of humans. These true-men had become animal hunters, and a number of groups started to migrate towards Asia, Europe, and later America in pursuit of other animals to hunt. In these distant lands, the climate was different from Africa, and the unforeseen changes in climates started bringing about the differences in the color of the skin of these people. This phenomenon started about 35,000 years ago, and interestingly, it is still going on until today. Although they are descendants of the same ancestors from proto-men, the appearance of these migrated humans has changed so much that the similarities are no longer visible. The accompanying map below shows the distribution of skin color among human beings, and these colors are fully suited and adapted to the climatic conditions of the areas where they live.
The ultraviolet rays of the Sun are a decisive factor in determining the skin color of humans. These high-frequency rays are incisive enough to burn and penetrate white skin, and they can sometimes produce skin cancer. Therefore, the natural process of evolution has provided ample protection to people living in hot and sunny areas in the form of a chemical substance named melanin, which is often black in color. This substance stops excessive Sun rays from penetrating the skin in order to protect healthy cells. The hotter the Sun rays are, the higher the proportion of melanin given to a person. When the melanin content in the skin is more than usual, it makes the skin turn darker.
Those people who have lived in Africa have the blackest skin, and due to heredity, their offspring will have dark skin as well. On the other hand, the people in Scandinavian countries like Norway, Sweden, and Denmark have low to zero amount melanin in their skin. The melanin from these light-skinned people is absent even from their hair, which makes its strands look white, golden, or blonde.
There is another reason behind these people’s lack of melanin content in their bodies, and this may have to do with evolution and adaptability of humans. The cells of our body usually require some sunlight to provide Vitamin D. In the far areas of the Northern Hemisphere, the Sun rays are so weak that the light would often shine from an acute angle. If melanin blocks this weak sunlight, how can the human body produce Vitamin D? The answer is that light-skinned humans have evolved to produce less and less melanin until their bodies can absorb sunlight better. However, this means that people with a specific skin color should continue living where they have always lived, and they should not travel to areas with different temperatures and climates.
One of the dilemmas that arose from people traveling to other countries happened during the Second World War when dark-skinned soldiers who fought on the Norwegian front were afflicted with a disease named rickets. This illness is caused by the lack of Vitamin D in their bodies, which may have been brought by their skin that produces too much melanin. As a result, they could not get sufficient sun rays due to the protective cover provided by melanin. The same problem also occurred in the Korean War, when some more African-American soldiers were afflicted with rickets.
On the other hand, there is another reason behind the blue-colored eyes of the Scandinavians. The hours of sunlight are few there, and sometimes there is only dim light throughout the day. The statement means that a night is longer than a day in the areas occupied by Scandinavians. Due to this peculiar phenomenon, the position or color of Sun rays is nearly red on the visible spectrum of light. If there is no melanin in the pupil and iris, then the eyes are able to absorb only that dim light, thus also allowing them to see slightly better at night. This is the reason why their eyeballs have ultimately become semi-transparent like glass.
When the Scandinavians settled in hot sunny areas since one or two generations ago, they have begun to use goggles regularly to protect their eyeballs from the glare of the sunlight while also sunbathing to increase melanin that can protect them more against the harsh rays of the Sun. However, because of the slow process of evolution, those light-skinned people who lived in areas with hotter climates have bodies that are not yet adapted to increase the production of melanin in their bodies, and it may take thousands of years before they can fully evolve to have dark skin.