As we have seen, early human beings formed small groups that developed a simple culture that enabled them to survive. As human societies grew and developed greater complexity, a new form of human existence-called civilization-came into being. A civilization is a complex culture in which large numbers of human beings share a number of common elements. These include:
(1) an urban focus: cities became the centers of political, economic, social, cultural, and religious development;
(2) a distinct religious structure: the gods were deemed crucial to the community's success, and professional priestly classes regulated relations with the gods;
(3) new political and military structures: an organized government bureaucracy arose to meet the administrative demands of the growing population, and armies were organized to gain land and power and for defense;
(4) a new social structure based on economic power: while kings and an upper class of priests, political leaders, and warriors dominated, there also existed a large group of free men (farmers, artisans, craftspeople) and at the very bottom, socially, a class of slaves;
(5) the development of writing: kings, priests, merchants, and artisans used writing to keep records; and
(6) new forms of significant artistic and intellectual activity: for example monumental architectural structures, usually religious, occupied a prominent place in urban environments.