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Human Adaptations

Human Skin Color Variation

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        Human beings are very diverse in their phenotypes and skin pigmentation is arguably the most defining factor of our appearance. Race is often used in the US to describe such diversity in skin color by employing very general terms such as “black” and “white,” even though white skin and black skin are not really characteristic of such groups. In fact, “skin pigmentation is a proxy for ‘race’, on the basis of which racism has been manifested” (Kittles et al, 2004).  In truth, skin color is an adaptation to climatic circumstances such as ultraviolet rays allowing the skin to reflect more or less light depending on the environment (Chaplin, 2004). The most important thing about human skin color variation is that the diversity is caused by people living in different environments in both hemispheres which exert different selective pressures through exposure to the sun and ultraviolet rays as well as other climatic conditions (Relethford, 1997).  The complete genetic structure of skin color is still not fully understood and certainly does not correspond to racial classifications.  However, understanding skin color adaptations and variations can help us to understand the way our ancestors have mixed in the past, as well as allow us to better comprehend the effects on one’s health, such as the risk of skin cancer.

Human skin color variation is misconstrued by social constructions such as race.   Race itself lacks meaning as a system of biological classification (Kittles et al, 2004). However, skin color can affect whether or not and to what degree a person is discriminated against, and the quality of services such as medical care (Kittles et al, 2004).  It is common to equate differences in skin color with “deeper biological differences among populations” (Kittles et al, 2004), but this is an incorrect assumption. On the other hand, skin color can be very useful for studying issues like ancestry and gene flow as long as we understand its biological implications properly.

What is seen as variation in skin color relates to differences in the amount and type of melanin that is in a person’s skin (Rees, 2004).  Skin pigmentation is both “genetically complex and at a physiological level complicated (Rees, 2003). However, only one gene is known to be the source of the great degree of diversity in skin and hair color, the melanocortin 1 receptor (Rees, 2004).  This degree of diversity means that people are also variable in their susceptibility to the harmful nature of ultraviolet radiation. Sunshine has both positive and negative effects on humans which means it is important to understand skin pigmentation and sun-sensitivity in the context of a person’s health and environment.  Studying skin color is important not only for health and medical reasons, but also for studies in genetics, ancestry, physical anthropology and social scientists (Rees, 2003).  To be sure, understanding the basis for differences in skin color is of major importance in many fields and disciplines as well as for the way in which people perceive and treat one another.

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How Do We Evaluate Skin Color Variation?

Selected Articles on Skin Color Variation

Important Conclusions and Suggestions for Further Research

Interesting Links

Works Cited

 

Chaplin, George. 2004. Geographic Distribution of Environmental Factors Influencing Human Skin Coloration. Am J Phys Anthropol 125: 292-302

 

Kittles RA, Parra EJ, and Shriver MD. 2004. Implications of correlations between skin color and genetic ancestry for biomedical research. Nature Genetics 36: 54-60

 

Rees, Jonathan L. 2004. The Genetics of Sun Sensitivity in Humans. Am J Hum Genet 75: 739-751

 

Rees, Jonathan L. 2003. Genetics of Hair and Skin Color. Annu Rev Genet. 37:67-90

 

Relethford, John. 1997. Hemispheric Difference in Human Skin Color. Am J Phys Anthropol 104: 449-457