Estimating the heritability of hair curliness in twins of European ancestry.

Recent studies in Asian populations have identified variants in the EDAR and FGFR2 genes that arose following the divergence of Asians and Europeans and are associated with thick straight hair. To date no genetic variants have been identified influencing hair texture in Europeans. In the current study we examined the heritability of hair curliness in three unselected samples of predominantly European ancestry (N(S1) = 2717; N(S2) = 3904; N(S3) = 5079). When rated using a three point scale (Straight/Wavy/Curly) males were approximately 5% more likely to report straight hair than females and there were suggestions in the data that curliness increased slightly with age. Across samples significant additive and dominant genetic influences were detected resulting in a broad sense heritability of 85-95%. Given the magnitude and the specificity of the EDAR effect on hair morphology in Asian populations we are hopeful that future association studies will detect similar genetic influences in European populations.