At the broadest level human cultures evolved in quite similar fashion around the world. All, of course, were part of that grand process of human migration that initially peopled the planet. Beginning in Africa, that vast movement of humankind subsequently encompassed Eurasia, Australia, the Americas, and Pacific Oceania. Almost everywhere, gathering and hunting long remained the sole basis for sustaining life and society. Then, on the three supercontinents—Eurasia, Africa, and the Americas—the momentous turn of the Agricultural Revolution took place independently and in several distinct areas of each landmass (see Chapter 1). That revolutionary transformation of human life subsequently generated, in particularly rich agricultural environments of all three regions, those more complex societies that we know as civilizations, featuring cities, states, monumental architecture, and great social inequality (see Chapter 2). In these ways, the historical trajectory of the human journey has a certain unity and similarity across quite distinct continental regions. This commonality provides the foundation for a genuinely global history of humankind. At the beginning of the Common Era, that trajectory had generated a total world population of about 250 million people, substantially less than the current population of the United States alone. By contemporary standards, it was still a sparsely populated planet.

The world’s human population was then distributed very unevenly across the three giant continents, as the Snapshot on page 264 indicates. If these estimates are even reasonably accurate, then during the second-wave era Eurasia was home to more than 80 percent of the world’s people, Africa about 11 percent, and the Americas between 5 and 7 percent. That unevenness in population distribution is part of the reason why world historians focus more attention on Eurasia than on Africa or the Americas. Here lies one of the major differences among the continents.

There were others as well. The absence of most animals capable of domestication meant that no pastoral societies developed in the Americas, and apart from llamas and alpacas in the Andes, no draft animals were available to pull plows or carts or to carry heavy loads for long distances. Africa too lacked wild sheep, goats, chickens, horses, and camels, but its proximity to Eurasia meant that these animals, once domesticated, became widely available to African peoples. Metallurgy in the Americas was likewise far less developed than in Eurasia and Africa, where iron tools and weapons played such an important role in economic and military life. In the Americas, writing was limited to the Mesoamerican region and was most highly developed among the Maya, whereas in Africa it was confined to the northern and northeastern parts of the continent. In Eurasia, by contrast, writing emerged elaborately in many regions. Furthermore, civilizations in Africa and the Americas were fewer in number and generally smaller than those of Eurasia, and larger numbers of their people lived in communities that did not feature cities and states.

A final continental comparison distinguishes the history of Africa from that of the Americas. Geography placed Africa adjacent to Eurasia, while it separated the Americas from both Africa and Eurasia. This has meant that parts of Africa frequently interacted with Eurasian civilizations. In fact, Mediterranean North Africa was long part of a larger zone of Afro-Eurasian interaction. Ancient Egyptian civilization was certainly in contact with Crete, Syria, and Mesopotamia and provided inspiration for the Greeks. The entire North African coastal region was incorporated into the Roman Empire and used to produce wheat and olives on large estates with slave labor. Christianity spread widely across North Africa, giving rise to some of the early Church’s most famous martyrs and theologians. The Christian faith found an even more permanent foothold in the lands now known as Ethiopia.

Arabia was another point of contact with Eurasia for African peoples. The arrival of the domesticated camel, probably from Arabia, generated a nomadic pastoral way of life among some of the Berber peoples of the western Sahara during the first three centuries C.E. A little later, camels also made possible trans-Saharan commerce, which linked interior West Africa to the world of Mediterranean civilization. Over many centuries, the East African coast was a port of call for Egyptian, Roman, and Arab merchants, and that region subsequently became an integral part of Indian Ocean trading networks. The transoceanic voyages of Austronesian-speaking sailors from Southeast Asia brought various food crops of that region, bananas for example, to Madagascar and from there to the East African mainland. The Americas, by contrast, developed almost wholly apart from this Afro-Eurasian network until that separation was breeched by the voyages of Columbus in 1492.

To illustrate the historical developments of the second-wave era beyond Eurasia/North Africa, this chapter examines first the civilizations that emerged in sub-Saharan Africa and the Americas. Then our historical spotlight turns to several regions on both continents that remained outside the zone of civilization, reminding us that the histories of many peoples took shape without the cities, states, and empires that were so prominent within that zone.