The elevated frequency of the Neandertal-derived alleles in the OAS locus (Fig. 1) relative to average levels of Neandertal ancestry in Europeans [6], along with the key role OAS genes play in protective immunity against viral infections, raises the possibility that introgressed Neandertal haplotypes at OAS may have been adaptive in modern humans. This evidence concerns the gene SMOC1 and viral infectious disease.