Evolution and Skin Color

By: Alisha Gomes


Image Credit: Flickr @ mekkora

Race, for decades, has been the root of many problems in American society. There is no doubt that for many racism plays a major role in their lives. However, what’s so incredible about science is that an understanding of an idea, like the differences in skin-colors, has the ability to unite people. Understanding why people have different skin colors will also help people understand the fact that no one is above others. The reason for different skin colors is not because some people are inferior or some are superior but rather because of evolution.

The central idea of evolution is that all life on Earth started from a single node: a common ancestor. All organisms on Earth evolved from this node and are thus related genetically. Scientists can thereby determine which species are most closely related by studying the shared characteristics of the specified species. There are many causes of differences between individuals of a certain species. The variation of an individual of a sexually reproducing species is caused by independent assortment and crossing over/recombination (meiosis). Moreover, there is variation because of the differences in the environments of individuals: one may live in a hot environment, while the other in a cold.


An adaptation is a variation that increases an individual's biological fitness in a specific environment. In other words, it is the result of the interaction of a population with its environment. Humans like other species have the ability to adapt biologically and physically to their environment. Adaptations, therefore, may be biological.

There are five main sources of variation in populations: mutations, natural selection, sexual selection, genetic drift, gene flow, and mutations.

  • Natural selection requires variation among a population. Nature will select the phenotype that is most fit. The individuals having this phenotype will survive, reproduce, and pass its gene to its offspring. Organisms with that gene will then pass on this advantageous characteristic to the next generation. Over generational time, the frequency of the allele responsible for this trait will increase in the population

  • Gene flow is the transfer of genetic variation from one population to another

  • Genetic drift is the change in frequency of a certain allele due to random chance events.

Melanin is a brown-black pigment in the skin, hair, and eye that is found in most biological organisms. Many believe that more melanin in the skin (the darker the skin is), the more protected the skin will be against the sun. It is well known that the sun emits harmful UV radiation that burns us and can damage our DNA, thus it may contribute to skin cancer. More melanin, therefore, is necessary to protect against the sun’s harmful rays. People with darker skin are closer to the equator, where the sun hits the strongest. The sun is also essential for our development and immune system because it allows us to produce folate or Vitamin D. Vitamin D levels in the body play an important role in the evolution of skin color in the human species. Not enough folic acid during early pregnancy can cause birth defects. Birth defects such as spina bifida can occur if not enough folic acid is received by the baby during pregnancy.


In short, the difference of skin color is only due to peoples’ geographic adaptations, meaning everyone, no matter what skin color, age, sex, etc, is the same.


Citations:

https://www.helyx.science/

https://humanorigins.si.edu/evidence/genetics/human-skin-color-variation/modern-human-diversity-skin-color

http://www.evo-ed.org/Pages/Skin/index.html

https://royalsocietypublishing.org/doi/10.1098/rstb.2016.0349

https://impact.psu.edu/story/the-evolution-of-skin-color

https://evolution.berkeley.edu/evolibrary/news/140305_skincolor


Image Credit:

No changes were made to the following image: https://www.flickr.com/photos/jobb_a_vartnal/4390312469/in/photolist-7FXuWz-NvG4te-YQ11Kr-22zGxy3-6r8z7G-S6kQ6q-WHxtFB-M6Nn7F-53Qis8-2ighKgE-5EEPPT-BjedFU-YynnQy-boigGv-at3oYV-2igegmd-TniLFQ-6DpYEF-HJwAa-k9RC8D-4782ae-XUmtJh-srvXZ5-5JaeQ6-7it2KY-5HVtAa-HnM2mR-3d22V2-9nxxoN-3nA2TM-TKYt87-994h9S-qN5Uco-3i9852-fNudby-HQqMvs-Pcz7Jt-a7AuQT-f6ksMu-5VqbQC-e4SPQ8-5JdP7X-79bVdn-7XKydF-79bV22-gyfYwH-79bV7K-djDoBn-79fMtf-79fLUb, License: https://creativecommons.org/licenses/by/2.0/legalcode


What Did You Learn?

Questions:

1. What is evolution?


Evolution revolves around the idea that all organisms on Earth have evolved from a single ancestor and that all living things are thus genetically similar to each other.


2. What does evolution have to do with skin color?


Humans have evolved to have different skin color as a result of their geographic adaptations. People with darker skin are closer to the equator, where the sun hits the strongest and thus they need more protection against it. More melanin in the skin (the darker the skin is) means it will be more protected against the sun.


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