The economy of a city requires an agriculture based upon a grain. Only grain growing has the productivity sufficient to allow a significant portion of society to devote their time to things other than food production. Wheat and other similar grains were domesticated in the Fertive Cresent that encompasses the Zagros Mountains of western Iran. Farming based upon wheat and other grain spread from the Fertile Cresent to the rest of the world. Later it was discovered that cultures in Southeast Asia had discovered independently to grow rice. This was about 7000 BCE.

Radiocarbon dating of finds of ancient millet gave dates around 6000 BCE. In May of 2009 researchers found specimens of millet in Hebei Province in northern China which have a dating of 8000 BCE. Millet is a coarse grain requiring a long cooking time, but it could sustain a culture. Millet growing spread to the region of the Black Sea by about 5000 BCE.