Africans lack archaic introgression above 1% frequency. Europeans carry minimal Neanderthal and Denisovan DNA among non-Africans. South Asians exceed Europeans, East Asians, and Maritime Southeast Asians in Neanderthal ancestry. Papuans possess up to 5% Denisovan ancestry from two distinct sources. Ayta Magbukon in Philippines have highest known Denisovan ancestry. Maritime Southeast Asians retain most unique Denisovan variation. Most archaic variants removed by negative selection. Archaic alleles enriched in immunity, skin pigmentation, and lipid metabolism genes. Neanderthal variants drive immune response differences between Europeans and Africans. Denisovan EPAS1 allele selected in Tibetans for high-altitude adaptation. Denisovan TBX15 haplotype at high frequency in Indigenous Americans aids cold adaptation. Indigenous Americans originally carried East Asia-level archaic ancestry. European and African admixture diluted archaic ancestry in modern Indigenous Americans. Underrepresented populations hold greatest potential for novel adaptive archaic variants. Papuans share few Denisovan variants with Eurasians.