GENETIC ORIGINS OF THE JAPANESE - A PARTIAL SUPPORT FOR THE DUAL STRUCTURE HYPOTHESIS

Based on the morphological characteristics of the skull and teeth, Han ihara ([1991] Japan Review 2:1-33) proposed the ''dual structure model '' for the formation of modern Japanese populations. We examine this m odel by dividing it into two independent hypotheses: 1) the Upper Pale olithic population of Japan that gave rise to the Neolithic Jomon peop le was of southeast Asian origin, and 2) modern Ainu and Ryukyuan (Oki nawa) populations are direct descendants of the Jomon people, while Ho ndo (Main Island)-Japanese are mainly derived from the migrants from t he northeast Asian continent after the Aeneolithic Yayoi period. Our a im is to examine the extent to which the model is supported by genetic evidence from modern populations, particularly from Japan and other A sian areas. Based on genetic distance analyses using data from up to 2 5 ''classic'' genetic markers, we find first that the three Japanese p opulations including Ainu and Ryukyuan clearly belong to a northeast A sian cluster group. This negates the first hypothesis of the model. Th en, we find that Ainu and Ryukyuans share a group contrasting with Hon do-Japanese and Korean, supporting the second hypothesis of the model. Based on these results, we propose a modified version of the dual str ucture model which may explain the genetic, morphological, and archaeo logical evidence concerning the formation of modern Japanese populatio ns. (C) 1997 Wiley-Liss, Inc.