In this innovative reinterpretation of the economic history of Africa and Europe, Warren C. Whatley argues that freedom from Western-style slavery is the origin of modern Western economic growth. Such freedom was achieved around the 13th century in Western European Christendom by making enslavement among European Christians a sin but still a recognized property right and form of wealth. After 1500, the triangular trade in the North Atlantic integrates the slave and free sectors of expanding European Empires, spreading freedom and development in Europe and slavery and underdevelopment in Africa. Whatley documents when the slave and/or free sectors drove the expansion of Empire, and how exposure to slave trades in Africa spread institutions and norms better suited to capturing and trading people – slavery, polygyny, ethnic stratification and inherited aristocracies – some of the mechanisms through which the past is still felt in Africa today.