 Further complicating intersectional methods, the very categories of identity that are taken to intersect may themselves be thought of as historically contingent and variable. To take the example of “race,” despite a complex history of biological essentialism in the presentation of racial typologies, the notion of a genetic basis to racial difference has been largely discredited; the criteria different societies (at different times) use to organize and hierarchize “racial formations” are political and contingent (Omi and Winant 1994 [1986]). While some human physical traits are in a trivial sense genetically determined, the grouping of different persons into races does not pick out any patterned biological difference. What it does pick out is a set of social meanings with political ramifications (Alcoff 1997, 2006). The most notorious example of an attempt to rationalize racial difference as biological is the U.S. “one-drop rule,” under which an individual was characterized as Black if they had “one drop” or more of “Black blood.” Adrian Piper points out that not only does this belief persist into contemporary readings of racial identity, it also implies that given the prolonged history of racial mixing in the US—both coerced and voluntary—very significant numbers of nominally “white” people in the U.S.  today should be re-classified as “Black” (Piper 1996). In those countries that have had official racial classifications, individuals’ struggles to be re-classified (almost always as a member of a more privileged racial group) are often invoked to highlight the contingency of race, especially at the borders of its categories. And a number of histories of racial groups that have apparently changed their racial identification—Jews, Italians, or the Irish, for example—also illustrate genealogical theses (Ignatiev 1995). The claim that race is “socially constructed,” however, does not in itself mark out a specific identity politics. Indeed, the very contingency of race and its lack of correlation with categories that have more meaning in everyday life (such as ethnicity or culture) may circumscribe its political usefulness: just as feminists have found the limits of appeals to “women’s identity,” so Asian-Americans may find with ethnicities and cultures as diverse as Chinese, Indian, or Vietnamese that their racial designation itself provides little common ground. That a US citizen of both Norwegian and Ashkenazi Jewish heritage will check that they are “white” on a census form says relatively little (although in a post-Trump U.S., it arguably says more [Jardina 2019]) about their experience of their identity, or indeed of their very different relationship to anti-Semitism. Tropes of separatism and the search for forms of authentic self-expression are related to race via ethno-cultural understandings of identity: for example, the U.S.  Afrocentric movement appeals to the cultural significance of African heritage for Black Americans (Asante 2000).