Population History of Japan as Viewed from Cranial Nonmetric Variation

Incidence data of cranial nonmetric traits were analysed in eight population samples from Japan, ranging in age from 4, 000 B.P. to the present time. The trait frequencies were extremely homogeneous in the Japanese samples during the last 600 years from early medieval to modern times when no significant gene flow from overseas was evident in Japan. It was inferred that the incidence pattern of cranial nonmetric traits faithfully reflected the Japanese genetic constitution of historic times.SMITH's Mean Measures of Divergence (MMDs) based on the incidence data of 20 nonmetric traits between the protohistoric and historic Japanese samples were statistically insignificant, whereas those between the Neolithic Jomon and the foregoing Japanese samples far exceeded the significance level of 0.01. The MMDs as well as the cluster analysis and principal coordinate analysis of MMDs suggested that (1) there existed population discontinuity between the Jomon and the protohistoric Kofun people; (2) the Aeneolithic Yayoi period was a phase when a number of different populations - natives and immigrants from the Continent - were struggling for their dispersals; (3) genetic constitution of the immigrants had predominated over that of the natives by the end of the Yayoi period and as a result the direct ancestral population of the modern Japanese was stablished during the protohistoric Kofun period. As for the Jomon and Ainu, their close affinity was demonstrated.