Quantitative assessment of skin, hair, and iris variation in a diverse sample of individuals and associated genetic variation

Objectives: The main goals of this study are to 1) quantitatively measure skin, hair, and iris pigmentation in a diverse sample of individuals, 2) describe variation within and between these samples, and 3) demonstrate how quantitative measures can facilitate genotype‐phenotype association tests. Materials and Methods: We quantitatively characterize skin, hair, and iris pigmentation using the Melanin (M ) Index (skin) and CIELab values (hair) in 1,450 individuals who self‐identify as African American, East Asian, European, Hispanic, or South Asian. We also quantify iris pigmentation in a subset of these individuals using CIELab values from high‐resolution iris photographs. We compare mean skin M index and hair and iris CIELab values among populations using ANOVA and MANOVA respectively and test for genotype‐phenotype associations in the European sample. Results: All five populations are significantly different for skin (P <2 × 10−16) and hair color (P