Jōmon period
A genetic study by Kanazawa-Kiriyama in 2013 found that the Ainu people (including samples from Hokkaido and Tōhoku) are closer to ancient and modern Northeast Asians (especially Udege people of eastern Siberia) than opposed to the geographically close Kantō Jōmon period samples. According to the authors, these results add to the internal-diversity observed among the Jōmon period population and that a significant percentage of the Jōmon period people had ancestry from a Northeast Asian source population, suggested to be the source of the proto-Ainu language and culture, which is not detected in samples from Kantō.