 A final area of philosophical concern to which population genetics is relevant is the debate over the status of racial categories. This is a central topic within the philosophy of race, a burgeoning sub-field of philosophy (see the entry on  race  for an overview). One influential line of argument has it that racial categories are social constructions rather than natural kinds. On this view, the division of the human species into distinct “races” (which can be done in multiple ways), should be understood primarily in terms of the social and political role that such racial categories play. This view is sometimes called “anti-realism” about race, since it holds that the usual ways of dividing humans into races (as employed in national censuses, for example) are conventional rather than real. Opponents of anti-realism have sometimes drawn on human population genetics to bolster the rival position that racial divisions are in fact real (Andreasen 2007, Sesardic 2010, Spencer 2015). Empirical studies of how genetic variation in humans is structured, using machine learning techniques, have found genetic clusters that appear to roughly correspond to certain broad racial groupings (such as “African” and “Eurasian”) (Rosenberg et al. 2002, Li et al. 2008). However, the precise bearing of these empirical results on the question of the reality versus conventionality of racial divisions is a matter of ongoing philosophical dispute (Kopec 2014, Winther 2014).