Studies of the Neanderthal and Denisovan genomes demonstrate archaic hominin 
introgression in Eurasians. Here, we present evidence of Neanderthal 
introgression within the chromosome 3p21.31 region, occurring with a high 
frequency in East Asians (ranging from 49.4% to 66.5%) and at a low frequency in 
Europeans. We also detected a signal of strong positive selection in this region 
only in East Asians. Our data indicate that likely candidate targets of 
selection include rs12488302-T and its associated alleles--among which four are 
nonsynonymous, including rs35455589-G in HYAL2, a gene related to the cellular 
response to ultraviolet-B irradiation. Furthermore, suggestive evidence supports 
latitude-dependent selection, implicating a role of ultraviolet-B. 
Interestingly, the distribution of rs35455589-G suggests that this allele was 
lost during the exodus of ancestors of modern Eurasians from Africa and 
reintroduced to Eurasians from Neanderthals.