Around 400–300 BC, the Yayoi people began to enter the Japanese islands, intermingling with the Jōmon. The Yayoi brought wet-rice farming and advanced bronze and iron technology to Japan. Although the islands were already abundant with resources for hunting and dry-rice farming, Yayoi farmers created more productive wet-rice paddy field systems. This allowed the communities to support larger populations and spread over time, in turn becoming the basis for more advanced institutions and heralding the new civilization of the succeeding Kofun period.
The estimated population in the late Jōmon period was about one hundred thousand, compared to about three million by the Nara period. Taking the growth rates of hunting and agricultural societies into account, it is calculated that about one and half million immigrants moved to Japan in the period
