When historians refer to Africa in premodern times, they are speaking generally of a geographic concept, a continental landmass, and not a cultural identity. Certainly few, if any, people living on the continent at that time thought of themselves as Africans. Like Eurasia or the Americas, Africa hosted numerous separate societies, cultures, and civilizations with vast differences among them as well as some interaction between them.

Many of these differences grew out of the continent’s environmental variations. Small regions of Mediterranean climate in the northern and southern extremes, large deserts (the Sahara and the Kalahari), even larger regions of savanna grasslands, tropical rain forest in the continent’s center, highlands and mountains in eastern Africa — all of these features, combined with the continent’s enormous size, ensured endless variation among Africa’s many peoples. Africa did, however, have one distinctive environmental feature: bisected by the equator, it was the most tropical of the world’s three supercontinents. While some regions, such as highland Ethiopia, sustained very productive agriculture, elsewhere a variety of factors generated lower crop yields and diminished soil fertility. These included heavy but sometimes-erratic rainfall frequently followed by long dry seasons and the leaching of nutrients from often very ancient soils. Climatic conditions also spawned numerous disease-carrying insects and parasites, which have long created serious health problems in many parts of the continent. It was within these environmental constraints that African peoples made their histories. In several distinct regions of the continent — the upper Nile Valley, northern Ethiopia/Eritrea, and the Niger River valley — small civilizations flourished during the second-wave era, while others followed later. A further African civilization falling partly within this time period grew up along the East African coast in conjunction with Indian Ocean commerce. Known as Swahili civilization, it is treated in greater detail in Chapter 7.