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Human Adaptations

How Do We Evaluate Skin Color Variation?

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         Human skin color variation is measured in various ways depending on the discipline and the researcher. This tends to lead to problems in the comparison of results from different studies.  Sometimes, color is subjectively determined by different observers, and often compressed into categories such as ‘white, intermediate and black’ (Parra et. al, 2004).  Obviously, this subjective measurement can lead to problems due to the nature of the subjectivity and the difficulty in comparing such data to other methods.  Other objective techniques to measure skin color are utilized as well, but include their own set of problems.

            The most common technique to measure constitutive skin pigmentation is broadband spectrophotometry, which makes it possible to gather data on skin reflectance at different wavelengths that can then be plotted for comparison (Rees, 2003).  Portable reflectance spectrophotometers were developed in the 1950’s and allowed people a way to objectively measure skin color without the bias of the observer based on the percentage of light which is reflected back from unexposed skin at a certain wavelength (Relethford, 1997).  The unexposed skin underneath the upper arm is most often the area used in these studies.  Anthropological studies have gathered substantial amounts of skin reflectance data for many populations (Relethford, 1997; Rees, 2003).  However, a problem results from the fact that “differences in instrumentation” and a “failure to account for differences in sun exposure” make many of these studies incomparable (Rees, 2003).  Two manufacturers, Cortex Technology and Photovolt Instruments, produce two different instruments, the DermaSpectrometer and the Photovolt model 575 spectrophotometer, respectively.  These two instruments make it hard to compare data between them, but do provide valuable information for examining human skin color variation and adaptation.

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Courtesy of Cortex Technology

Selected Articles on Skin Color Variation

Important Conclusions About Skin Color and Suggestions for Further Research

Human Skin Color Variation

Interesting Links

 

Works Cited

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