[The population history of the Japanese]

This paper introduces a "dual structure model" that explains the population history of the Japanese population including the Okinawa islanders (Ryukyus) and Ainu under a single hypothesis. The model assumes that the first occupants of the Japanese Archipelago came from somewhere in Southeast Asia in the Upper Palaeolithic age and gave rise to the people in the Neolithic Jomon age, or Jomonese; then the second wave of migration from North Asia took place in and after the Aeneolithic Yayoi age; and the populations of both lineages gradually mixed with each other. The "dual structure model" also assumes that the population intermixture is still continuing and the dual structure of the Japanese population is maintained even today. Thus, several regional differences such as those between eastern and western Japan in physical as well as cultural characteristics can be explained by the rates of intermixture that vary from region to region. In general, this model agrees well not only with physical and cultural evidence but also with non-human evidence revealed by man's symbiotic animals such as Japanese dogs and mice. At the same time, the model provides a reasonable way of explanation in regard to affinities and relationships among the Japanese main islanders, Ryukyus and Ainu.