HUMAN SKIN COLOUR: THE DIFFERENCES AMONGST US
By Dr Mirriam Tawane, Curator Palaeontology, DITSONG: National Museum of Natural History
The visible difference in our skin colour has brought about a painful past, filled with discrimination and pure discontent amongst the human race. Scientifically, we have often heard the statements “we have a common ancestor”. The visible proof is that when we look in a mirror, we certainly do not look alike. We do not have the same skin colour. Within what is regarded as a single race, there are different shades of lightness and darkness in skin tone. The question is: what brought about this most noticeable difference amongst humans. As difference that resulted in humans being classified according to race; a difference also used to infer superiority and inferiority, that over time resulted in the most atrocious acts by modern humans.
Children of different races holding hands.
(Source: https://www.goodhousekeeping.com/uk/lifestyle/a33272055/talk-to-children-race-racism/)
A person’s skin colour is a trait that is tied to their biology and genetics. Science has indicated that the difference between the skin colour of humans is the result of the pigmentation agent called melanin. Melanin is a natural skin pigment. It is made by skin cells called melanocytes. The colour of our skin, hair, and eyes mostly depends on the amount of melanin we have. We have the same amount of melanocytes; the difference is the amount of melanin produced. The skin colour darkens as the concentration of melanin increases (Ortonne, 2002; Fajuyigbe and Young, 2016).
In South Africa, populations were classified on the basis of ‘race’ from 1950. The four groups used were ‘native’, ‘coloured’, ‘Asian’ or ‘white’. By 1966 11 million people had been classified under the Population Registration Act of 1950 (Population registration Act, 1950).
It is believed that the loss of body hair resulted in the development of skin pigmentation. In the fossil record, skin pigmentation dates back to 1.5 million years ago, around the time of Homo heidelbergensis. During that time earth experienced a megadrought that drove early hominids into open arid landscapes, moving away from the equatorial landscape. These hominids were probably light skinned at the time. The move to the savanna required better cooling mechanisms. Loss of body hair and the development of more efficient perspiration contributed to the cooling of hominins from the scorching heat of the savannah. Hominins (early humans) with hairless skins were vulnerable to be harmed by ultraviolet light, and this could be a problem for those living in areas with high and intense ultraviolet (UV) radiation. UV radiation is part of the natural energy produced by the sun. Exposure to UV rays enhances the production of vitamin D, essential for calcium absorption and protection of bones and serves several immune functions.
However, being exposed to a high amount of UV rays probably caused xeric stress in the skins of early humans, and depletion of folate in the blood. Xeric stress is the lack of water that produces biomechanical, metabolic, physical and psychological stress. Folate is a vitamin B present in many foods. It plays a vital role in the formation of red and white blood cells in the bone marrow. It is also needed in the production of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). An evolutionary response to this would be to develop a dark skin as a form of protection. A darker skin acts as a mechanism to protect folate depletion caused by increased exposure to sunlight. It helps the body to retain its folate reserves and protects against possible damage to the DNA (Jablonski and Chaplin, 2010).
When our ancestors started migrating away from the equator to high latitudes, they encountered less UV rays. At a higher latitude, especially during winter, they experienced a dropped vitamin D level to a point where their health was compromised. Vitamin D deficiency could lead to rickets, cancers and even cardiovascular diseases. The dark skin now became a disadvantage. To be able to absorb more UV rays, the skin needs to reduce its sunblock abilities. This could only be achieved by the reduction of melanin production. Less melanin means one becomes light skinned; and thus absorb more UV rays. This will balance the Vitamin D content, and reduces chances of several diseases.
The evolution of hairless skin, abundant sweat glands, and a skin rich in melanin, allowed early humans to walk, run, and forage for food for long periods of time under the hot sun without brain damage due to overheating. This gave them an evolutionary advantage over other species.
There is a correlation between the geographic distribution of UV radiation and the distribution of skin pigmentation around the world. Areas that have higher amounts of UV radiation have darker skinned populations, generally located nearest to the equator. Areas that are further away from the equator have a lower concentration of UV radiation and its populations are light-skinned. However, migration across the world has contributed to the not so perfect skin colour distribution that we witness today. There are certain mismatches between skin pigmentation of other people and the geographic distribution of UV radiation in the places they currently inhabit.
Our skin colour difference is not an attribute to be used as a differential matrix amongst us. It should not be used to infer superiority of any group above the other. It should not be used as an advantage to access certain platforms or economic advancement. It should not be used to limit either of us to have equal opportunities to make the most of our lives and explore our talents and passions to the fullest. It is merely an adaptation that makes it possible for us to survive in the environment we are exposed to. Our skin colour is just one of the many evolutionary processes necessary for the survival of mankind.
References
- Fajuyigbe, D; Young, A. R. 2016. The impact of skin colour on human photobiological responses. Pigment Cell & Melanoma Research. 29 (6): 607–618.
- Jablonski, N, G; Chaplin, G. 2010. Human skin pigmentation as an adaptation to UV radiation. Proceedings of the National Academy of Sciences of the United States of America. 107(2): 8962–8968.
- Ortonne, J.P. 2002. Photoprotective properties of skin melanin. British Journal of Dermatology. 146 (61):7–10.
- Population registration Act, Act no. 30 of 1950. South Africa.
- https://www.goodhousekeeping.com/uk/lifestyle/a33272055/talk-to-children-race-racism/. Accessed 27 July 2021.
