Pigmentation is the most readily visible signifier of race, and as such it's often used by laymen to detect bi-racial ancestry. Yet it's also the least reliable from this standpoint, as it changes in response to climatic and environmental conditions, both seasonal and long-term, and can vary greatly within genetically differentiated populations (i.e. races).

"Skin color is one of the most conspicuous ways in which humans vary and has been widely used to define human races. Here we present new evidence indicating that variations in skin color are adaptive, and are related to the regulation of ultraviolet (UV) radiation penetration.... Skin coloration in humans is adaptive and labile. Skin pigmentation levels have changed more than once in human evolution. Because of this, skin coloration is of no value in determining phylogenetic relationships among modern human groups."

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"Skin color should always be taken on some unexposed part of the body. Among Middle Easterners this is simple, because they cover as much of the body as is consistent with their work. The exposed skin color may be a dark brown, while the skin of the underarm is ten shades lighter. (The sun shines brightly in the Middle East.) While fair-skinned people are to be seen, they live chiefly in shaded bazaars and government offices, whence they rarely emerge into the dazzling light of day."
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Below is the 36-tone chromatic scale devised by Austrian anthropologist Felix von Luschan to assess the unexposed skin of human populations. It's often referenced by Coon, who loosely correlates it with his own broader adjectives for skin tones: In general, pinkish-white corresponds to #3-9 on the scale; brunet-white to #9-16; light brown to #15-18; medium brown to #21-25; and dark brown to #26-29. The last two are observed only outside of Europe, so even the darkest Europeans fall within the lighter end of the spectrum.

(Von Luschan, 1927)

"A forceful presentation of the second point—that racial differences are merely cosmetic—was given recently in an editorial in the New England Journal of Medicine: 'Such research mistakenly assumes an inherent biological difference between black-skinned and white-skinned people. It falls into error by attributing a complex physiological or clinical phenomenon to arbitrary aspects of external appearance. It is implausible that the few genes that account for such outward characteristics could be meaningfully linked to multigenic diseases such as diabetes mellitus or to the intricacies of the therapeutic effect of a drug.' The logical flaw in this argument is the assumption that the blacks and whites in the referenced study differ only in skin pigment. Racial categorizations have never been based on skin pigment, but on indigenous continent of origin. For example, none of the population genetic studies cited above, including the study of Wilson et al., used skin pigment of the study subjects, or genetic loci related to skin pigment, as predictive variables. Yet the various racial groups were easily distinguishable on the basis of even a modest number of random genetic markers; furthermore, categorization is extremely resistant to variation according to the type of markers used (for example, RFLPs, microsatellites or SNPs).

"Genetic differentiation among the races has also led to some variation in pigmentation across races, but considerable variation within races remains, and there is substantial overlap for this feature. For example, it would be difficult to distinguish most Caucasians and Asians on the basis of skin pigment alone, yet they are easily distinguished by genetic markers. The author of the above statement is in error to assume that the only genetic differences between races, which may differ on average in pigmentation, are for the genes that determine pigmentation."
(Risch et al. 2002)

Examples of metrically identical racial types adapted to different climates:








Striking contrasts of people deeply tanned and then with natural coloration:

Carla Collado   Carla Collado
(Spanish Model)

Alessandro Nesta   Alessandro Nesta
(Italian Footballer)

Evelina Papantoniou   Evelina Papantoniou
(Greek Model)

Ray Romano   Ray Romano
(Italian American Actor)

Related Topics
Skin Reflectance: Chart of pigmentation levels for selected world populations (after Jablonski).

Tanned vs. Natural: A few more skin color contrasts.