Conclusion

Over the fourth and third millennia BCE, the world’s social landscape changed in significant ways. In a few key locations, where giant rivers irrigated fertile lands, complex human cultures began to emerge. These areas experienced all the advantages and difficulties of expanding populations: occupational specialization; social hierarchy; rising standards of living; sophisticated systems of art and science; and centralized production and distribution of food, clothing, and other goods. Ceremonial sites and trading crossroads became cities that developed centralized religious and political systems. As scribes, priests, and rulers labored to keep complex societies together, social distinctions within the city (including the roles of men and women) and the differences between country folk and city dwellers sharpened.

Although river-basin cultures shared basic features, each one’s evolution followed a distinctive path. Where there was a single river—the Nile or the Indus—the agrarian hinterlands that fed cities lay along the banks of the waterway. In these areas cities were small; thus, the Egyptian and Harappan worlds enjoyed more political stability and less rivalry. In contrast, cities in the immense floodplain of the Tigris and Euphrates needed large hinterlands to sustain their populations. Because of their growing power and need for resources, Mesopotamian cities vied for preeminence, and their competition often became violent.

In most areas of the world, however, people still lived in simple, egalitarian societies based on hunting, gathering, and basic agriculture—as in the Americas and sub-Saharan Africa. In Anatolia, Europe, and parts of China, regional cultures emerged as agriculture advanced and populations grew—but not with the leaps and bounds and fast-paced momentum of the river-basin cultures. Some of them, as in the Aegean and Europe, forged warrior societies. Beyond these frontiers, farmers and nomads survived as they had for many centuries. Thriving trading networks connected many, but not all, of these regions to one another.

Changes in climate affected everyone and could slow or even reverse development. How—and whether—cultures adapted depended on local circumstances. As the next chapter will show, the human agents of change often came from the fringes of larger settlements and urban areas.