Y-CHROMOSOMAL DNA VARIATION AND THE PEOPLING OF JAPAN

Four loci mapping to the nonrecombining portion of the Y chromosome we re genotyped in Japanese populations from Okinawa, the southernmost is land of Japan; Shizuoka and Aomori on the main island of Honshu; and a small sample of Taiwanese. The Y Alu polymorphic (YAP) element is pre sent in 42% of the Japanese and absent in the Taiwanese, confirming th e irregular distribution of this polymorphism in Asia. Data from the f our loci were used to determine genetic distances among populations, c onstruct Y chromosome haplotypes, and estimate the degree of genetic d iversity in each population and on different Y chromosome haplotypes. Evolutionary analysis of Y haplotypes suggests that polymorphisms at t he YAP (DYS287) and DXYS5Y loci originated a single time, whereas rest riction patterns at the DYS1 locus and microsatellite alleles at the D YS19 locus arose more than once. Genetic distance analysis indicated t hat the Okinawans are differentiated from Japanese living on Honshu. T he data support the hypotheses that modern Japanese populations have r esulted from distinctive genetic contributions involving the ancient J omon people and Yayoi immigrants from Korea or mainland China, with Ok inawans experiencing the least amount of admixture with the Yayoi. It is suggested that YAP(+) chromosomes migrated to Japan with the Jomon people >10,000 years ago and that a large infusion of YAP(-) chromosom es entered Japan with the Yayoi migration starting 2,300 years ago. Di fferent degrees of genetic diversity carried by these two ancient chro mosomal lineages may be explained by the different lifestyles (hunter- gatherer versus agriculturalist). of the migrant groups, the size of t he founding populations, and the antiquities of the founding events.