by many, most scholars agree that race has real material effects in the lives of people through institutionalized practices of preference and discrimination. Socioeconomic factors, in combination with early but enduring views of race, have led to considerable suffering within disadvantaged racial groups. Racial discrimination often coincides with racist mindsets, whereby the individuals and ideologies of one group come to perceive the members of an outgroup as both racially defined and morally inferior. As a result, racial groups possessing relatively little power often find themselves excluded or oppressed, while hegemonic individuals and institutions are charged with holding racist attitudes. Racism has led to many instances of tragedy, including slavery and genocide. In some countries, law enforcement uses race to profile suspects. This use of racial categories is frequently criticized for perpetuating an outmoded understanding of human biological variation, and promoting stereotypes. Because in some societies racial groupings correspond closely with patterns of social stratification, for social scientists studying social inequality, race can be a significant variable. As sociological factors, racial categories may in part reflect subjective attributions, self-identities, and social institutions. Scholars continue to debate the degrees to which racial categories are biologically warranted and socially constructed. For example, in 2008, John Hartigan, Jr. argued for a view of race that focused primarily on culture, but which does not ignore the potential relevance of biology or genetics. Accordingly, the racial paradigms employed in different disciplines vary in their emphasis on biological reduction as contrasted with societal construction. In the social sciences, theoretical frameworks such as racial formation theory and critical race theory investigate implications of race as social construction by exploring how the images, ideas and assumptions of race are expressed in everyday life. A large body of scholarship has traced the relationships between the historical, social production of race in legal and criminal language, and their effects on the policing and disproportionate incarceration of certain groups. Historical origins of racial classification Groups of humans have always identified themselves as distinct from neighboring groups, but such differences have not always been understood to be natural, immutable and global. These features are the distinguishing features of how the concept of race is used today. In this way the idea of race as we understand it today came about during the historical process of exploration and conquest which brought Europeans into contact with groups from different continents, and of the ideology of