We may think and talk about civilization as one pattern or level of culture, one stage through which human life flows and ebbs. In that sense we may regard it abstractly and historically, as we regard the most recent ice age or the long and painful record of large-scale chattel slavery... Civilization is a level of culture built upon foundations laid down through long periods of pre-civilized living. These foundations consist of artifacts, implements, customs, habit patterns and institutions produced and developed in numerous scattered localities by groups of food-gatherers, migrating herdsmen, cultivators, hand craftsmen and traders and eventually in urban communities built around centers of wealth and power: the cities which are the nuclei of every civilization...