Slavery's evolution from an accepted worldwide practice to its present status as an international crime, took place over the course of only a century and a half—from about the beginning of the nineteenth century to the middle of the twentieth century. Slavery has existed since ancient times, dating back to at least the times of the Old Testament. The practice was deeply engrained in ancient Rome, Greece, and the cultures of the ancient near east. The Bible contains numerous references to the practice of slavery, and Roman law had elaborate statutes and precedents for the regulation of slaves. Well before the Europeans went to the New World, there was an elaborate slave trade between the Baltic and Mediterranean regions, and slavery was legal almost everywhere in medieval and early modern Europe. Throughout the Islamic world, slavery was a fixture of society. Long before Europeans went to Africa or the New World, Arab traders were...