QUOTE : connection between skin color and sunlight. The results were as clear as the sky on a cloudless day—there was a near-constant correlation between skin color and sunlight exposure in populations that had remained in the same area for 500 years or more. They even produced an equation to express the relationship between a given population’s skin color and its annual exposure to ultraviolet rays. (If you’re feeling adventurous, the equation is W = 70-AUV/10. W represents relative whiteness and AUV represents annual ultraviolet exposure. The 70 is based on research that indicates that the whitest possible skin—the result of a population that received zero exposure to UV—would reflect about 70 percent of the light directed at it.)