West Africa — the part of the continent that bulges into the Atlantic — can be visualized as a broad horizontal swath divided into three climatic zones. The Sahel is the mostly flat, semiarid zone immediately south of the Sahara. Below it lies the savanna, a grassland region dotted with trees and shrubs. South of the savanna, in a band 200 to 300 miles wide along the West African coast, lies a tropical rain forest. A series of four major watersheds — the Senegal, Gambia, Volta, and Niger — dominate West Africa (Map 1.3).

Sudanic civilization took root at the eastern end of West Africa beginning around 9000 B.C. and traveled westward. Sudanic peoples domesticated cattle (8500–7500 B.C.) and cultivated sorghum and millet (7500–7000 B.C.). Over several thousand years, these peoples developed a distinctive style of pottery, began to cultivate and weave cotton (6500–3500 B.C.), and invented techniques for working copper and iron (2500–1000 B.C.). Sudanic civilization had its own tradition of monotheism distinct from that of Christians, Muslims, and Jews. Most Sudanic peoples in West Africa lived in stratified states ruled by kings and princes who were regarded as divine.

From these cultural origins, three great empires arose in succession in the northern savanna. The first, the Ghana Empire, appeared sometime around A.D. 800. Ghana capitalized on the recently domesticated camel to pioneer trade routes across the Sahara to North Africa, where Ghana traders carried the wealth of West Africa. The Ghana Empire gave way to the Mali Empire in the thirteenth century, which was eclipsed in turn by the Songhai Empire in the fifteenth century. All three empires were composed of smaller vassal kingdoms, not unlike the Aztec and Inca empires, and relied on military might to control their valuable trade routes.

Gold, abundant in West Africa, was the cornerstone of power and an indispensable medium of international trade. By 1450, West African traders had carried so much of it across the Sahara that it constituted one-half to two-thirds of all the gold in circulation in Europe, North Africa, and Asia. Mansa Musa, the tenth emperor of Mali, was a devout Muslim famed for his construction projects and his support of mosques and schools. In 1326, he embarked on a pilgrimage to Mecca with a vast retinue that crossed the Sahara and passed through Egypt. They spent so much gold along the way that the region’s money supply was devalued for more than a decade after their visit.

To the south of these empires, the lower savanna and tropical rain forest of West Africa were home to a complex mosaic of kingdoms that traded among themselves and with the empires to the north. In such a densely populated, resource-rich region, they also fought frequently in a competition for local power. A few of these coastal kingdoms were quite large in size, but most were small enough that they have been termed ministates by historians. Comparable to the city-states of Italy, they were often about the size of a modern-day county in the United States. The tropical ecosystem prevented them from raising livestock, since the tsetse fly (which carries a parasite deadly to livestock) was endemic to the region, as was malaria. In place of the grain crops of the savanna, these peoples pioneered the cultivation of yams; they also gathered resources from the rivers and seacoast.