How Spanish and Portuguese colonialism shaped our conception of whiteness A landmark treatment of a pivotal historical question, Reckoning with Race in New Worlds reveals how the empires of Spain and Portugal debated and came to determine who was white and who was not during their colonial era. How did free people with partial Native American, Asian, or African lineage either become or cease to be blancos or brancos --white people? Ruth Hill explains how, in unexpected ways, science and religion joined forces in the early modern era to shape the concepts of purity, mixture, and degeneration that would decide these questions. Fixing the thresholds of whiteness--degrees of blood, generations spent in a foreign environment--instigated centuries-long controversies with enormous consequences. By putting into dialogue archival sources as well as extensive engagement with secondary literature, paintings, and maps, Reckoning with Race in New Worlds crafts a history of human diversity in the colonial era, with profound implications for our understandings of the natural and social sciences and of our racial present.