The evaluation of skin pigmentation is of great interest to evolutionary biologists seeking to understand the human skin and answer the questions that have existed for years. The human skin is quite unique; it is tough, sensitive, and ranges in various colors from darkest to lightest.
The different skin colors affect the reflectance, that is, the amount of light reflected from the surface of an individual’s skin. The pigmentation found in the skin primarily regulates biochemical effects on the skin that cause diseases such as skin cancer, by controlling the amount of Ultraviolet radiation that penetrates the human skin. The human skin is affected by many substances such as specialized keratin proteins that enable the skin to fight off physical and chemical infections. On the other hand, the sickle cell gene has largely accumulated in populations across the tropical Africa.
These high frequencies of sickle cell gene have accumulated in several countries which include Greece, Mozambique, South turkey, India among others. The sickle cell gene, synonymous to sickle cell disease, is a genetic disease in which the Red blood cells are abnormally shaped in form of a sickle, consequently making them prone to getting trapped in blood vessels.
This effect prevents blood from reaching all the body parts and cause tissue damage. This essay seeks to expound on how both the sickle cell gene and human skin pigmentation are examples of evolution and describe the four forces of evolution at work and their influence on the trait. Moreover, it seeks to highlight the data and evidence used by scientists used to validate these claims.
Research has many people commenting how the skin evolved from hair covered skin to hairless skin. Our closest primate relatives, the chimpanzees, are born with relatively pale skin which contracts with the human skin noted to have a range of colors. The infant’s skin is protected by their hair and therefore remains pale, as their skin on the face darkens and becomes similar to that of the mother after exposure to the sun rays.
The human ability to produce melanin pigment in specialized cells known as melanocytes is a condition common to ancestors of chimpanzees and humans. Researchers infer that members of a species genetically known as hominins possess similar skin anatomy to the modern chimpanzees. Comparative biologists deduce that, the reconstruction of the skin appearance of the fossil is possible though a range of techniques which include functional and comparative genomics.
Both sickle cell gene and skin color pigmentation are phenomena that are quite intriguing if one takes a closer study into them. The two phenomena are a product of mutation that has occurred over a period of time therefore making changes to the genetic constitution of the human body. It is important to understand the genesis of the changes in both skin color pigmentation and sickle cell gene in light of natural selection. Natural selection is a process whereby the organism that adapt best to the environment survive and produce more offspring while the ones that don’t die.
As far as natural selection is concerned, human beings are not exceptional, adaptation to the environment has enabled the human species evolve and survive to where we are today. The sickle cell gene is prevalent in the world today and 20% of the trait has been found across the tropical African belt (Livingstone, 1958).
Scientists have associated the heterozygous sickle cell gene with the immunity of malaria. In other words, the sickle cell gene creates immunity against the parasite causing malaria. The discovery of the relationship between malaria and sickle cell gene has brought answers to many question. Malaria has been around the world for quite some time and is associated for over a million infant death worldwide.
Research has shown that the sickle cell developed as a counter measure to malaria that was raging havoc on the human species. Moreover, the sickle cell trait is associated with higher reproductive capacity since sickly females experiences less falciparum infections of the placenta. Therefore, malaria is associated with maintaining the high frequency of the sickle cell gene (Livingstone, 1958).
Secondly, skill color pigmentation is diverse across the entire continent. Skin color varies from dark, light or even tan. This therefore, begs the question, ‘what might be the likely cause?’ Primates dissipate heat primarily through radiation and evaporation, this therefore made the early primates of the species Homo loose excess and unwanted fur that inhibited the skin from evaporation through sweat. The loss of body fur exposed the body to the harmful effects of ultra violet radiation from the sun. As a result, the members of the Homo species inhabiting Africa developed dark skin as a result of mutation (Jablonski, 2012).
In as much as ultra violet radiation is the causative agent of cancer of the skin, cancer does not have any relationship with an individual’s ability to sire offspring. However, the most evolutionary significant effect of ultra violet radiation is the effect of foliate mechanism. Folate is a vitamin B necessary for DNA repair. Folate is acquired from plants and is calculated basing on several parameters, for instance, body needs and the effects of environmental stressors like ultra violet radiation. UVR causes folate deficiency which cause complications that occur during cell division.
Among the likely effects of the complication during cell division is its effect on the period of sperm formation and also its effect during pregnancy. Therefore, it is true to infer that mutation in form of natural selection occurred to protect the human species from the extinction which may have resulted from the harmful effect of UVR. The difference in skin color pigmentation varies according to the difference in latitude. Higher latitudes experience less radiation from the sun therefore less melanin while the closer the distance to the equator the darker the skin color pigmentation (Jablonski, 2012).
Scientists have conducted enough research on both sickle cell gene and the difference in skin color pigmentation across the world. On the prevalence of sickle cell gene, research has been done on malaria prone area of east and west Africa and data collected on individuals with both heterozygous trait and also those with homozygous trait.
Moreover, scientist have done research on the effect of UVR on the human skin and its relationship to skin color, this has enabled them reach conclusions that are comprehensive. It is true therefore to make a conclusion that natural selection is the causative agents of both the sickle cell gene and the difference in skin color pigmentation across the world.
Work Cited
- Jablonski, Nina G. ‘Human skin pigmentation as an example of adaptive evolution.’ Proceedings of the American Philosophical Society 156.1 (2012): 45-57.
- Livingstone, Frank B. ‘Anthropological implications of sickle cell gene distribution in West Africa.’ American Anthropologist 60.3 (1958): 533-562.
