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Japan population structure

Dual origin hypothesis

Previous studies showed genetic affinities between the Ainu and Ryukyu peoples,who live in the north and south ends of Japan, respectively, and who are thought to be descendents of the Jomon people. These observations are consistent with the “dual-origin hypothesis”, which states that the ancestral Japanese populations were brought by two major migration events. Archeological studies have suggested that the Jomon period (the Japanese Neolithic age) started about (14000 - 300 BC), when the Yayoi period(300 BC - 250 AD), a rice-farming and metal-using age, started. In the Yayoi period, immigrants from the Asian continent had moved to western Japan via Korea or China and expelled or mixed with the Jomon people. Our observations of the two main clusters and genetic differentiation among geographic regions are not discordant with the dual-origin hypothesis, although most of the Hokkaido individuals in this study are probably different from the indigenous Ainu people. Most of the people living in Okinawa Island are probably derived from the Jomon people, whereas most of the people living in Hondo are probably derived from the Yayoi people or are a mixture of the Yayoi and Jomon peoples.

Individuals in Tohoku showed two interesting features that are difficult to attribute to only local genetic differentiation. First, within the Hondo cluster, the individuals from Tohoku were closest to the individuals from Okinawa with respect to Eigenvector 1 (Supplemental Data). Second, the FST value between Tohoku and Okinawa was smaller than the FST value between Tokai-Hokuriku and Okinawa, even though the geographical distance between Okinawa and Tohoku is greater than that between Okinawa and Tokai-Hokuriku. These observations might reflect ancient population affinities between Tohoku and Okinawa, which have been obscured by the gene flow between their geographic neighbors in Honshu Island.

The presence of two main clusters may also be explained by the long-term isolation of populations in the Ryukyu Islands.However, the finding that the FST value between Okinawa and Tohoku was smaller than that between Okinawa and Tokai-Hokuriku cannot be explained by only local genetic differentiation. The distinct difference between the Hondo and the Ryukyu clusters is probably due to two factors: there were two major migrations to Japan, and populations in the Ryukyu Islands became genetically differentiated by isolation.

from sciencedirect

yayoi culture and its relationship to Wu Kingdom 吳國

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