There were three races in ancient Japan: Japanese, Emishi (later Ainu) and Ashihase (possibly Okhotsk). Historical literature supports the theory that the Emishi were considered rebels by the Japanese, and therefore potentially subjects by way of conquest. Consistently, the Japanese divided them into those who had submitted themselves to Yamato rule as allies and subjects, and those who were outside their authority. Those outside imperial authority were seen as "barbarians" beyond the frontier. Michinoku, the name the Yamato Japanese had given for the Tohoku, literally translates as "deepest road" with the connotation of a far away place: the Emishi were seen as inhabitants of this far away land, beyond the frontier. The Ashihase were thought of as a foreign people altogether, and it is not clear who they were; however, in the latest research there are tantalizing clues that the relationship between the Ashihase and the Emishi mirrored the relationship between the Japanese and the Emishi . That is, just as the Japanese were completing their conquest of the Tohoku region, Emishi began to consolidate more of Hokkaido. The Ashihase were most likely an Amur river people who were definitely East Asian hunter-gatherers who moved south from Sakhalin into Hokkaido and were either absorbed or conquered by the Emishi of the Satsumon culture. The Satsumon consolidated their hold about the same time that the Tohoku Emishi began to migrate into Hokkaido (see especially Yamaura 1999:42-45, and the in-depth discussion by Crawford implying that the Tohoku Emishi may have actually created the Satsumon culture. Satsumon is a name of a culture that is ancestral to the Hokkaido Ainu.
According to archeological findings from the fifth to the seventh centuries AD, the northern half of Tohoku (roughly extending from northern Miyagi prefecture to Aomori) and the western part of Hokkaido formed a single cultural area, and many Ainu place names are left in the Tohoku. It is beyond the discussion of this introduction to go into the Jomon, Epi-Jomon and Yayoi cultures as they affected the Tohoku region, but to simplify this discussion, it is now believed that evidence points to the Emishi tie in with the Tohoku Middle Yayoi pottery culture that is heavily influenced by Jomon forms--almost as if these peoples were gradually adopting Yayoi culture from the seventh to the eighth centuries.
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The place where the Emishi fit into this picture follows in the descriptions given about them in the historical period. They are known as mojin or kebito (hairy people) by their Japanese conquerors, and contemporary Chinese court historians of the T'ang. And this is where history begins to corroborate physical anthropology. The Ainu are known for their abundant hair, both on the torso and limbs, and mostly in their heavy beards. It is absolutely certain that people ancestral to the Ainu lived in northern Honshu in this time period. The cultural area of the Emishi coincides with the areas that used to be under Ainu control. The very word Emishi is probably a Japanese derivation of the word "emchiu" or "enjyu" which translates to "man" in the Ainu/Emishi language. The kanji characters for Emishi are identical to Ezo. Before Ainu came into usage in the Meiji period they were known as Ezo.
Even if we accept these arguments plenty of questions remain. What were the differences between the Ainu and the Ashihase? What happened to the Emishi who migrated to Hokkaido, and how did they influence the development of Satsumon culture? What is the relationship between the Hokkaido and Tohoku Emishi, and when did the Ainu emerge? One thing is certain: we shouldn't even think of Ancient Japan as being composed of a single ethnic group like it appears today. Racial or ethnic affiliation did not determine who were or were not Japanese subjects: the connection between culture and blood came after centuries of political unity. For example, ethnic Korean and Chinese immigrants migrated to Japan at this time to help consolidate the bureaucracy and form artisan groups.
Even if we answer the earlier question about Emishi ethnic affiliation as positively Ainu, they were different culturally from both Japanese and Ainu. They cannot be seen as either one or the other. First of all, as you will begin to see in the following web pages, the Emishi had a distinctive culture that differed from that of the Ainu. Like the North American Indians, there were different cultural groups among the Jomon tribes, and the primary difference was that the Emishi were horse riders, and much of their culture and style of warfare were adapted to the use of the horse. Second, the Emishi had a profound influence on the emerging Japanese Yamato state: they basically forced the Yamato to adopt much of their style of warfare, and even the title of Shogun came out of warfare against them. Historically, they certainly rejected affiliation with the Japanese. Further, to complicate matters, many Emishi became subject to the Japanese state and eventually disappeared as a separate ethnic group, becoming intermarried with other ethnic Japanese. It is almost certain that this intermixing took place in different degrees according to the time period and location. The western side of the Tohoku (towards Akita) probably has seen less due to the mountains making the western side less accessible, whereas, the Pacific side has seen to more thorough assimilation because of the broad Sendai plain, but even here not until the modern period when movement has been aided by economics (job concentration in Tokyo, for example) and transportation has the mixing become more complete.
The Emishi seem to have eventually assimilated via Japanese settlement and intermarriage between the two aristocracies. The wider website on the Emishi comes recommended with some caveats--the emphasis on a Caucasian racial origin of the Ainu is obsolete. Still, the way in which an outlying area of Japan was assimilated is described apparently accurately and evocatively.
Much earlier, during the Nara and early Heian period, the Tohoku (northeast Japan as a whole was seen as the frontier in the same sense [as early modern Hokkaido]. That is, the area was described as michi-no-oku or "deep road" meaning an area that lay beyond Japanese culture, ethnicity and norms: an area that lay outside the known world. It was considered to be foreign territory when Taga fort was constructed close to what is now Sendai in 724 as a frontier outpost of Japan in its attempt to take the territory from the Emishi. This region looked to its cultural and trade ties with northeast Asia, to the Matsukatsu, a sinified Tungus power, that controlled the Amur river trade, and to the Okhotsk of Sakahlin and Hokkaido. The fur trade flourished in this region at the time, but its culture contrasted from the Japanese who were more influenced by the Korean and Chinese states to the south.
By the Early Modern period the Ezo in Hokkaido had become sharply contrasted to the Japanese on the main island, but this was not always the case. This of course has lead to the reification or static view of both societies that does not seriously take historical change into account. Truth be told, there were two cultural directions that met, struggled and contested what became Japan, one influenced by a northern cultural tradition that was influenced by native peoples of Siberia, Sakhalin and the Amur river valley. The other, Yamato, was influenced by the centralized states of Korea and China. The winning side eventually became the Japanese state. However, we cannot forget the shadow of the past when a competing people and culture held sway in northeast Japan, one that was as different from what came after as can be imagined.