All social categorizations are inherently nested up to the level of humanity.

Evidence

However, our focus in this chapter is less on how optimal distinctiveness motives and group inclusiveness influence the formation of superordinate categories (when none are already recognized) and more on how they influence identification with salient nested social categories. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 676

Categorization

• XREF: The nested-categorization insight connects to social identity theory and self-categorization theory’s level-of-abstraction continuum.