What controls variation in human skin color?

Abstract

There is a large range of human skin color, yet we know very little about the underlying genetic architecture. Is the number of skin color genes close to five, 50, or 500?

Figure 1. Biochemistry and Histology of Different Skin Types

(A) Activation of the melanocortin 1 receptor (MC1R) promotes the synthesis of eumelanin at the expense of pheomelanin, although oxidation of tyrosine by tyrosinase (TYR) is required for synthesis of both pigment types. The membrane-associated transport protein (MATP) and the pink-eyed dilution protein (P) are melanosomal membrane components that contribute to the extent of pigment synthesis within melanosomes. (B) There is a gradient of melanosome size and number in dark, intermediate, and light skin; in addition, melanosomes of dark skin are more widely dispersed. This diagram is based on one published by Sturm et al. (1998) and summarizes data from Szabo et al. (1969), Toda et al. (1972), and Konrad and Wolff (1973) based on individuals whose recent ancestors were from Africa, Asia, or Europe.

Figure 2. Relationship of Skin Color to Latitude

(A) A traditional skin color map based on the data of Biasutti. Reproduced from http://anthro.palomar.edu/vary/ with permission from Dennis O'Neil. (B) Summary of 102 skin reflectance samples for males as a function of latitude, redrawn from Relethford (1997).