XVI PRIMITIVE NOMADIC PEOPLES It was not only in Mesopotamia and the Nile Valley that men were settling down to agriculture and the formation of city states in the centuries between 6000 and 8000 B.C. Wherever there were possibilities of irrigation and a steady all-the-year-round food supply men were exchanging the uncertainties and hardships of hunting and wandering for the routines of settlement. On the upper Tigris a people called the Assyrians were founding cities; in the valleys of Asia Minor and on the Mediterranean shores and islands, there were small communities growing up to civilization. Possibly parallel developments of