 Mass slavery requires economic surpluses and a high population density to be viable.Due to these factors, the practice of slavery would have only proliferated after the invention of agriculture during the Neolithic Revolution, about 11,000 years ago.Slavery was known in civilizations as old as Sumer, as well as in almost every other ancient civilization, including ancient Egypt, ancient China, the Akkadian Empire, Assyria, Babylonia, ancient Iran, ancient Greece, ancient India, the Roman Empire, the Arab Islamic Caliphate and Sultanate, Nubia and the pre-Columbian civilizations of the Americas.