Istwa Nou

The earliest exchange anyone can date is the movement of sheep and goats out of the Levant and south into the eastern Sahara, to peoples speaking Cushitic and Nilo-Saharan languages, under way shortly before 6000 BCE. It opens a long stretch of history with no clean start and no clean finish, conventionally bracketed at 6000 to 3000 BCE. What changed in this period is that the independently invented farming systems of the world began to meet. Thirteen separate centres had each worked out their own crops and their own domestic animals. Those packages now started to circulate, and every system that took something in became more productive for it. The herders of the eastern Sahara were already keeping African cattle when Levantine sheep and goats arrived, and they added the newcomers to a pastoral economy of their own making. Traffic in the other direction, out of Africa and into Eurasia, would prove at least as consequential.

A long list of crops and one animal of northeastern African origin began moving into Eurasia between 5000 and 3000 BCE, and the flow widened from 3000 BCE onward. The animal was the donkey, and it may have mattered more than everything on the plant list. It made overland carriage of goods and people workable across distances that porters could not sustain, which is the precondition for a caravan route. The trails that later linked Egypt to Mesopotamia, and West Africa to the Mediterranean, all ran on it. Ehret adds a further claim: the donkey may have been the model for putting the horse and the camel to the same use, in which case Africa supplied Eurasia with the idea of the beast of burden along with the first one. In the Americas the comparable transfer came later, when maize, beans and new squashes reached the Eastern Agricultural Complex of the present-day central United States during the first millennium BCE.