The Arabs had acquired Africans as slaves for centuries, but they were exploited in a feudal context. African slaves in Arab hands became domestics, soldiers, and agricultural serfs. Whatever surplus they produced was not for reinvestment and multiplication of capital, as in the West Indian or North American slave systems but for consumption by the feudal elite. Indeed, slaves were often maintained more for social prestige than for economic benefit.
p. 225. - How Europe Underdeveloped Africa (1972)