Satsumon culture
The Satsumon culture is a partially agricultural, archeological culture of northern Honshu and southern Hokkaido that has been identified as Emishi, as a Japanese-Emishi mixed culture, as the incipient modern Ainu, or with all three synonymously. Scholars frequently equate Satsumon people with the Emishi, a culture that emerged in northern Honshu as early as the 5th century CE, and in being ancestral to the Ainu people. This proposition is based on similarities between Ainu and Emishi skeletal remains as well as a number of place names across Honshu that resemble Ainu words. It is possible that the emergence of Satsumon culture in Hokkaido was triggered by immigration of Emishi people from Honshu. However, there are many differences between Emishi and Satsumon. For instance, horse riding and rice agriculture, neither of which were present in ancient Hokkaido, were both central to Emishi lifestyle. It may have arisen as a merger of the Yayoi–Kofun and the Jōmon cultures. The Satsumon culture appears to have spread from northeastern Honshu into southern Hokkaido. The Satsumon culture is regarded to be ancestral to the later Ainu culture, under some influence of the Okhotsk culture.
Subsistence
Iron tools seem to have prevailed around the end of Epi-Jomon, so that stone tools disappeared in the Satsumon period. Among subsistence activities, hunting, gathering and fishing continued to be the most important. Locations of large settlements at estuaries indicate the importance of salmon. Although cultivation of buckwheat and barley is presumed for the Epi-Jomon, reliable evidence shows that the Satsumon additionally cultivated rice, wheat, sorghum, various types of millet, green gram, perilla, melon, adzuki bean and hemp. Many of these plants were likely imported from mainland Asia. Opinions divide among those who, taking Satsumon culture as the periphery of the Kofun culture of the mainland, argue that such crops supplied a large portion of the diet, and those who think it provided only a small part and the culture was basically a continuation of the Epi-Jomon.A study of pottery residue on Rebun Island sheds light on how the Satsumon culture adapted to a new environment. Unlike their mainland counterparts who combined farming with hunting and gathering, the Satsumon people on Rebun Island appear to have relied more heavily on exploiting marine resources like fish and shellfish. This shift in subsistence strategy suggests that the island's ecosystem was not ideal for their established practices of mixed farming and hunting. The focus on marine resources may also explain why the Satsumon presence on Rebun seems to have been relatively short-lived.