Evolution of Human Skin Pigmentation.

Evolution of Human Skin Pigmentation.

Skin pigmentation is referred to as the skin’s color. According to Jablonski, Nina  & George, Humans are said to have been dark-skinned before they evolved and settled to new areas hence adoption to different skin pigmentations according to the environment’s condition (2017). Melanin acts as a sunscreen that protects one from harmful sun rays. Individuals who moved to cold climatic conditions adopted lighter skin. Areas away from the equator have low ultraviolet levels, and therefore, natural selection has favored their skin as the rays penetrate and produce the necessary minerals. However, the dark counterparts used their pigmentation to stop foliate deficiency. Ultraviolet rays are known to cause cancer, although this had minimal effects on the skin’s evolution since evolution was accompanied by changes that increased reproduction. This review will be highlighting how natural selection led to the distribution of various skin pigmentations in the world. Also, there will be a highlight of how different skin complexions have adopted to their selected favorable environmental conditions.

Why Humans have skin pigmentation

Man’s skin pigmentation is caused by their genes, such as the genetic composition of one’s parents and also the skin’s exposure to the sun. Skin pigmentation evolved through natural selection to regulate ultraviolet rays on the skin. The human skin has the dark pigmentation with melanin, and the white pigmentation has low melanin levels; therefore, it is white. Different skin complexions are caused by the different levels of melanin produced by the melanocytes. The level of hemoglobin that circulates the dermis and the connective tissue underneath the dermis determines light color pigmentation.

Environmental pressures responsible for natural skin pigmentation; factors that reduce reproductive rates in Equatorial and high latitude areas.

Ultraviolet radiation varies according to various geographical locations. Areas that have high Ultraviolet rays are located next to the equator, and this comprises mainly of the dark-skinned population. However, areas that are away from the equator and receive low Ultraviolet ration tend to have light-skinned individuals. Over the years, skin pigmentation has changed as individuals migrated to various geographical locations. Environmental pressures not only affect the skin color but also affect the levels of reproduction in high latitude areas as well as the tropical regions. Research states that female adults have lighter complexions compared to their male counterparts. The female skin evolved and became lighter so that their bodies would absorb more calcium, which is vital for lactation and pregnancy.

Tropical areas, pigmentation protected individuals from harmful sun rays and therefore safeguard the foliate. However, according to Barros et al., exposure to the sun helps in vitamin D production, which is essential to a baby’s health (2017). Pigmented individuals are more likely to be reproductive hence passing their traits to their generations. High latitude areas where they are less exposed to sunlight, their bodies can absorb enough vitamin D, which is vital in bone strength (Rossberg & Willi 2016). This way, they can reach adulthood and reproduce hence passing their traits to other generations. If high latitude areas receive too much sunlight, then their reproductive levels will reduce.

Similarly, environmental factors affect reproduction in equatorial regions, although it is curbed by the presence of melanin among most individuals. Women that lack vitamin D in their childhood have higher chances of having pelvic deformations. This prevents natural child delivery in women of both high latitudes and equatorial regions.

How dark pigmentation is an adaptation to the selective pressure found near the equator.

Equatorial regions are known to experience high levels of sunlight throughout the year. Natural selection has allowed darker individuals to live in tropical areas, especially unforested parts, which have high sunlight concentration. Their dark pigmentation is due to high melanin production, which protects them from the harmful sunlight rays. It helps prevent ailments such as sunburns, which affects the DNA and subsequently results in skin cancer. Tropical regions have an advantage as degenerative disorders mostly occur in areas with low sunlight intensity. Children who grow up in tropical climates have lesser chances of developing multiple sclerosis regardless of their origin. These children enjoy this protection even if they move to high latitude areas. Skin conditions such as sunburns are common among light-skinned individuals living in hot areas. Their skin does not have a defense mechanism to protect itself from harmful sunlight rays, and that explains the skin’s irritation. Dark pigmentation is the perfect adaptation for people living in hot regions. With enough melanin production, they can secret enough vitamin D for their bodies and also protect themselves from harmful ultraviolet sun rays that harm the skin by causing infections such as sunburns and skin cancer (Rossberg & Willi 2016).

How light pigmentation is an adaptation to the selective pressure found at higher latitudes

Skin decencies like Melanoma which is a skin cancer that causes the death of close to eight thousand individuals in the United States every year. European Americans who have light skin complexion are more likely to get skin deficiencies over the African Americans living in the same region but have darker complexions. The light skin of individuals living in high latitude areas make it possible for them to absorb the limited vitamin D the sun provides. If these individuals have high melanin levels, then their bodies will not absorb the solar nutrients from the sun. In such environments, dark complexion causes rickets among children, and the production of insufficient vitamin D caused osteoporosis among adults. High latitude areas have high ultraviolet radiation during summer, and these revels drastically decrease during winter. Natural selection has allowed their skin to tan to adapt to the weather changes, and this is possible due to the increase in the granule numbers that are stimulated by the ultraviolet radiation( Yamaguch et al. 2007). However, not all light skin individuals can tan as the exposure to the sun peels off their skin due to sunburns. In these areas, individuals with high melanin levels are at risk of contracting diseases such as Anemia. Also, during winter, when there is no sunlight, there are high numbers of patients lacking vitamin D, especially from dark skin individuals living in these areas.

Conclusion

As reviewed, different skin complexions have different responses to different environmental conditions. High individuals are more favored by high latitudes, while dark individuals are favored by tropical conditions. Natural selection is what led to different species moving and adapting to a specific environmental situation. Both ecological conditions have specific adaptative requirements that relate to individuals with particular complexions (Deng & Shuhua 2018). However, despite being two different environmental conditions, it is essential for individuals with both ski complexions to absorb enough sunlight rays as it produces Vitamin D and also calcium, which not only strengthens one’s bones but also boosts one’s immune system.

Work Cited

Yamaguchi, Yuji, Michaela Brenner, and Vincent J. Hearing. “The regulation of skin pigmentation.” Journal of Biological Chemistry 282.38 (2007): 27557-27561.

Barros, Renan Sales, and Marcelo Walter. “Synthesis of human skin pigmentation disorders.” Computer Graphics Forum. Vol. 36. No. 1. 2017.

Rossberg, Willi, et al. “Human pigmentation, cutaneous vitamin D synthesis, and evolution: Variants of genes (SNPs) involved in skin pigmentation are associated with 25 (OH) D serum concentration.” Anticancer Research 36.3 (2016): 1429-1437.

Jablonski, Nina G., and George Chaplin. “The colors of humanity: the evolution of pigmentation in the human lineage.” Philosophical Transactions of the Royal Society B: Biological Sciences 372.1724 (2017): 20160349.

Deng, Lian, and Shuhua Xu. “Adaptation of human skin color in various populations.” Hereditas 155.1 (2018): 1.

Rossberg, Willi, et al. “Human pigmentation, cutaneous vitamin D synthesis, and evolution: Variants of genes (SNPs) involved in skin pigmentation are associated with 25 (OH) D serum concentration.” Anticancer Research 36.3 (2016): 1429-1437.