If language is recognized as the element that determines an ethnic group, then the number of ethnic groups is equal to the number of languages. The existence of minority ethnic groups is first of all closely related to political history, and secondly to geographical environment. In most cases where a minority ethnic group has direct and continuous contact with the ruling, centralized government of a another ethnic group, language was the first thing to be lost, followed by ethnic identity. Those ethnic groups not faced with such a situation were able to survive. Those groups, like the Yenchin and the Mongols, that had once dominated the world stage either died out or became minority groups due to continuous contact with the Han people, which made up the majority of China. Geographically isolated groups, such as those in mountainous or island areas, were able to preserve their language and ethnical identity. The majority of the minority groups in southern China are in this category.
The similarities of various cultures are often compared in anthropology, folklore studies, or mythology studies, and the relations between the origins of these cultures is often mentioned. Yet in the case of 'race' the criteria of differentiation are to some extent well established, but in the case of 'ethnic group' it is difficult to objectively establish any convincing criteria. In the era of historical comparative linguistics, which developed at the beginning of the 19th century, a popular interpretation was to extend the similarities between languages to a theory of identical ethnical origin.
In the latter half of the 19th century it was discovered that the Korean language possessed some similarities with the Ural-Altaic languages used by nomadic Turkic and Mongol peoples of Central Eurasia and the Tartar language group, and thus the Ural-Altaic language family theory was introduced. This theory was handed down to Korean intellectuals under the colonial rule of Japan by Japanese scholars. As was the case in central Europe in the 19th century, this theory was expanded to form the basis for a search for the origin of the Korean people in the regions north of the Korean peninsula. Afterward, the Ural-Altaic language family theory became simply the Altaic language family theory, and many scholars spent many years trying to come up with definitive evidence for this theory. Their efforts, however, could not draw the attention of the international academic world, and they are now fading away.
Yet, since the era of the Ural-Altaic language family, the idea of a relationship between the Korean peoples and the northern peoples is firmly established in the minds of most researchers of Korean culture. The similarities, beginning with myths and including such customs as shamanism, can be confirmed. This has scholarly research value, but we must be careful of offering the explanation that "the Korean people groups and the northern people groups are offshoots of the same root."