Before European contact, Native Americans did not use the concept of race.
Membership in a tribe/Nation was based on social relationships (e.g., kinship, marriage, adoption) and cultural similarities and traditions (Jaimes, 1995; O’Nell, 1996). If you lived with the tribe, you were a member.
The idea of race, and particularly the importance of a “pure” race, was part of European values introduced through invasion and colonization (Jaimes, 1995).
European racial theories led to U.S. Federal Indian policies which in turn influenced (if not dictated) tribal definitions of belonging within the constraints of the policies.
Jaimes, M. A. (1995). Some kind of Indian: On race, eugenics, and mixed-bloods. In N. Zack (Ed.), American mixed race: The culture of microdiversity (pp. 133–153). Lanham, MD: Rowman & Littlefield.
O'Nell, T. D. (1996). Disciplined hearts: History, identity, and depression in an American Indian community. Berkeley, CA: University of California Press.