Once considered an objective scientific theory of difference within human populations, racism has become regarded as an ideology of social domination and exclusion on the basis of biological and genetic variation. The scientific basis of racism has been largely discredited, but the ideas that human populations can be divided into distinct groups based on phenotype, that the culture and behavior of these groups is determined by genetic differences, and that biological difference justifies the dominance of certain races over others remain widely influential.

Racism often figures prominently in the ideologies that justify and promote genocide and other crimes against humanity. Dominant social groups commonly use racial categorizations to differentiate other social groups and justify their exclusion and marginalization. The belief that personality and social behavior are linked to biology and therefore are unalterable makes physical...