In humans, the geographical apportionment of the coding diversity of the 
pigmentary locus melanocortin-1 receptor (MC1R) is, unusually, higher in 
Eurasians than in Africans. This atypical observation has been interpreted as 
the result of purifying selection due to functional constraint on MC1R in high 
UV-B radiation environments. By analyzing 3,142 human MC1R alleles from 
different regions of Spain in the context of additional haplotypic information 
from the 1000 Genomes (1000G) Project data, we show that purifying selection is 
also strong in southern Europe, but not so in northern Europe. Furthermore, we 
show that purifying and positive selection act simultaneously on MC1R. Thus, at 
least in Spain, regions at opposite ends of the incident UV-B radiation 
distribution show significantly different frequencies for the melanoma-risk 
allele V60L (a mutation also associated to red hair and fair skin and even 
blonde hair), with higher frequency of V60L at those regions of lower incident 
UV-B radiation. Besides, using the 1000G south European data, we show that the 
V60L haplogroup is also characterized by an extended haplotype homozygosity 
(EHH) pattern indicative of positive selection. We, thus, provide evidence for 
an adaptive value of human skin depigmentation in Europe and illustrate how an 
adaptive process can simultaneously help to maintain a disease-risk allele. In 
addition, our data support the hypothesis proposed by Jablonski and Chaplin 
(Human skin pigmentation as an adaptation to UVB radiation. Proc Natl Acad Sci U 
S A. 2010;107:8962-8968), which posits that habitation of middle latitudes 
involved the evolution of partially depigmented phenotypes that are still 
capable of suitable tanning.