It probably goes back to the Neolithic Revolution, although the first cities (Çatalhöyük for instance) appear to have been classless. Expropriation comes in many different flavors (different modes of production), but it's always present whenever class society is present. "The first slavery was the slavery of women." It probably begins with the invention of writing, which was itself invented to keep track of all the stuff belonging to the Sumerian ruling class.