Geographic distribution of environmental factors influencing human skin coloration

Abstract

Skin coloration in indigenous peoples is strongly related to levels of ultraviolet radiation (UVR). In this study, the relationships of skin reflectance to seasonal UVR levels and other environmental variables were investigated, with the aim of determining which variables contributed most significantly to skin reflectance. The UVR data recorded by satellite were combined with environmental variables and data on human skin reflectance in a geographic information system (GIS). These were then analyzed visually and statistically through exploratory data analysis, correlation analysis, principal components analysis, least-squares regression analysis, and nonlinear techniques. The main finding of this study was that the evolution of skin reflectance could be almost fully modeled as a linear effect of UVR in the autumn alone. This linear model needs only minor modification, by the introduction of terms for the maximum amount of UVR, and for summer precipitation and winter precipitation, to account for almost all the variation in skin reflectance. A further significant finding was that the effect of summer UVR seems to reach a threshold beyond which further adaptation is difficult.

Assessing the photoprotective effects of red ochre on human skin by in vitro laboratory experiments

“…In addition to the incidence of lighter skin types amongst autochthonous groups along the southern and eastern coastline of South Africa and Mozambique 54 , the preservation of the SLC24A5, TYRP1 and KITLG alleles amongst sub-Saharan populations 20 suggests that these are ancestral southern African mutations. The skin colour of southern African MSA H. sapiens is therefore likely to have resembled the olive-brown 'Capoid' skin type IV (Von Luschan 16 to 21) typical of some indigenous southern African groups.…”

Evolutionary perspective in skin color, vitamin D and its receptor

“…4 Thus, skin colour of humans correlates with geographical latitude and UV radiation levels. 4,[9][10][11] The latitudinal correlation reflects a compromise solution to the conflicting physiological need for vitamin D, as an essential component for the maintenance of calcium homeostasis and skeletal metabolism, and the detrimental effect of UV on folic acid generation. 12 Evolution has used skin pigmentation as a tool for that balance.…”

Human skin pigmentation, migration and disease susceptibility

“…Skin pigmentation in humans is correlated most strongly with ultraviolet radiation (UVR), among all environmental factors measured [1,2]. As the most important factor regulating the penetration of UVR into the skin, pigmentation has wide-ranging effects on health [1,2].…”