Istwa Nou

What holds the age of agricultural exchange together is what the exchanges did to social, political and ritual life. Each transfer added a crop or an animal to a farming system, raised its output, widened its diet and reduced the damage a single failed harvest could do. The consequences ran through the population. Better fed communities grew, growing communities settled closer together, and dense settlement forced people to work out larger villages, more elaborate kinship, more formal authority and more specialised trades. Over the following three millennia that arrangement produced cities, states and empires in several regions at once. Africa was one of the main theatres. The Middle Nile culture area, the rise of Qustul and the unification of Egypt belong to the same process that produced Mesopotamia, the Indus valley and the states of the Yellow River, and they were built on the same foundation of exchanged crops and exchanged herds.

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.