The Beginning of the Yayoi-era in Japan

It has been generally believed that the Yayoi-era, when some tribes came across the sea from the west and introduced a rice crop in the Japanese Archipelago with irrigating the paddy field, begun in the third century B.C. Recently, however, excavations of ruins suggest that the time of the beginning of the Yayoi-era could go back to more than two hundred years before that of the established theory.