More To Explore

The Evolution of Human Skin Coloration. Nina G. Jablonski and George Chaplin in Journal of Human Evolution, Vol. 39, No. 1, pages 57-106; July 1, 2000.

Why Skin Comes in Colors. Blake Edgar in California Wild, Vol. 53, No. 1, pages 6-7; Winter 2000. The article is also available at www.calacademy.org/calwild/winter2000/html/horizons.html The Biology of Skin Color: Black and White. Gina Kirchweger in Discover, Vol. 22, No. 2, pages 32-33; February 2001. The article is also available at www.discover.com/feb__01/featbiology.html

ronmental conditions by almost exclusively cultural means— wearing heavy protective clothing and devising portable shade in the form of tents. (Without such clothing, one would have expected their skin to have begun to darken.) Generally speaking, the more recently a group has migrated into an area, the more extensive its cultural, as opposed to biological, adaptations to the area will be.

Perils of Recent Migrations

DESPITE GREAT IMPROVEMENTS in overall human health in the past century, some diseases have appeared or reemerged in populations that had previously been little affected by them. One of these is skin cancer, especially basal and squamous cell carcinomas, among light-skinned peoples. Another is rickets, brought about by severe vitamin D deficiency, in dark-skinned peoples. Why are we seeing these conditions?

As people move from an area with one pattern of UV radiation to another region, biological and cultural adaptations have not been able to keep pace. The light-skinned people of northern European origin who bask in the sun of Florida or northern Australia increasingly pay the price in the form of premature aging of the skin and skin cancers, not to mention the unknown cost in human life of folate depletion. Conversely, a number of dark-skinned people of southern Asian and African origin now living in the northern U.K., northern Europe or the northeastern U.S. suffer from a lack of UV radiation and vita

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