Some Aspects of the Genetic Composition of the Japanese

This paper deals with the main characteristics of the Japanese as viewed from the distribution of genetic markers. Firstly, it is shown by the genetic distance and cluster analyses that three ethnic groups of Japan, namely, the Wajin, the Ainu and the Ryukyuan, are clearly distinguished to each other. Among them, particularly the Wajin has the genes supposedly introduced from the continental north-east Asia through Korea in high frequencies. Secondly, it is demonstrated that the Ainu belongs to the Mongoloid race, rather than to the Caucasoid. Their phenotypic features are explained as generalized Proto-Mongoloid characters. Thirdly, the genetic link between the Ainu and the Ryukyuan is suggested genetically, and they both are considered to be descendants of Proto-Japanese populations. Fourthly, several cases of gene frequency cline are observed, suggesting that relatively large number of immigrants came through Korean peninsula to north-eastern Kyushu and then spread eastwardly and southwardly since the Yayoi period. In this paper I shall review the following four topics which I have been concerned in the studies of past 25 years: (1) Genetic nature of the major Japanese population, the Wajin; (2) Genetic affinities of the Ainu; (3) The Ainu and the Ryukyuan; (4) Gene frequency cline in Japan. I will start with a dendrogram (Fig. 1) based on the gene frequencies of 8 polymorphic blood proteins. The dendrogram shows clearly that there are three genetically distinguishable populations in Japan [1]. Incidentally, they correspond to three ethnic groups of Japanese Islands, namely, the Ainu of Hokkaido, the Ryukyuan (or Okinawan) of south-western Islands, and the majority of the Japanese inhabiting all of the Japanese Islands and called Wajin or Yamato, or Hondo-Jin. There is no concensus about how we may call ourselves. Because of the large standerd error, further clustering of Wajin into several local groups is probably meaningless so far as this dendrogram is concerned.