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, India, the Roman Empire, the Arab Islamic Caliphate and Sultanate, Nubia and the pre-Columbian civilizations of the Americas.The Dutch imported slaves from Asia into their colony in South Africa.

When British rule was first imposed on the Sokoto Caliphate and the surrounding areas in northern Nigeria at the turn of the 20th century, approximately 2 million to 2.5 million people there were slaves.The Dutch, French, Spanish, Portuguese, British, Arabs and a number of West African kingdoms played a prominent role in the Atlantic slave trade, especially after 1600. Forsythe wrote: "The fact remained that at the beginning of the nineteenth century an estimated three-quarters of all people alive were trapped in bondage against their will either in some form of slavery or serfdom." However, slavery is rare among hunter-gatherer populations.Mass slavery requires economic surpluses and a high population density to be viable.The population of the Sokoto caliphate formed by Hausas in northern Nigeria and Cameroon was half-slave in the 19th century.It is estimated that up to 90% of the population of Arab-Swahili Zanzibar was enslaved.