East Asian Gene flow bridged by northern coastal populations over past 6000 years

Coastal areas of northern East Asia in the ShanDong region, which show complex cultural transitions in the last 10,000 years, have helped to facilitate population interactions between more inland regions of mainland East Asia and islands such as those in the Japanese archipelago. To examine how ShanDong populations changed over time and interacted with island and inland East Asian populations, we sequenced 85 individuals from 11 ancient sites in the ShanDong region dating to ~6000-1500 BP. We found that ancestry related to ShanDong populations likely explains the mainland East Asian ancestry observed in post-Yayoi populations from the Japanese archipelago, particularly recent populations who lived in the Ryukyu Islands after ~2800 BP. In the ShanDong region, we observed gene flow from populations to the north and south of this region by at least ~7700 BP, and two waves of gene flow associated with the inland Yellow River populations into the ShanDong region during the DaWenKou cultural period (6000-4600 BP) and in the early dynastic period (3500-1500 BP). Reconstructing the genetic history of the Neolithic, Bronze, and Iron Age populations of coastal northern East Asia shows gene flow on both a north-south and an east-west (inland-coastal-island) scale.