Do skin and hair pigmentation in prepubertal and early pubertal stages correlate with 2D:4D?

Abstract

In most human populations women are less pigmented than men. However, before puberty, boys tend to have lighter skin than girls. Previous research has shown that skin pigmentation in European women is negatively correlated with digit ratio (2D:4D). Therefore, it has been hypothesized that skin pigmentation in females is partially controlled by prenatal hormones. The aim of this study was to examine the correlation between 2D:4D and pigmentation in girls and boys in the prepubertal or early pubertal stages of ontogenesis. The study group consisted of 598 Polish children (275 boys), aged 6.5-10.5 years. All underwent spectrophotometric measurements of skin and hair melanin index (SMI and HMI) and had the second and the fourth finger on both hands measured directly. SMI (in girls) and HMI (in girls and boys) were positively correlated with age but 2D:4D was not. We regressed SMI and HMI on age and used the residuals as a measure of age-independent pigmentation. In girls, positive correlations were found between resSMI and 2D:4D for the right hand, but there was no correlation with left 2D:4D. In boys, resSMI did not correlate with 2D:4D. The resHMI was not related to 2D:4D in girls or boys. Skin pigmentation in prepubertal or early pubertal girls is related to 2D:4D such that high 2D:4D is associated with higher pigmentation. This relationship may be mediated by the individual rate of sexual maturation.