Trans-African trade, like the commerce of the Silk Roads and the Sea Roads, was rooted in environmental variation. The North African coastal regions, long part of Roman or later Arab empires, generated cloth, glassware, weapons, books, and other manufactured goods. The great Sahara held deposits of copper and especially salt, while its oases produced sweet and nutritious dates. While the sparse populations of the desert were largely pastoral and nomadic, farther south lived agricultural peoples who grew a variety of crops, produced their own textiles and metal products, and mined a considerable amount of gold. These agricultural regions of sub-Saharan Africa are normally divided into two ecological zones: the savanna grasslands immediately south of the Sahara, which produced grain crops such as millet and sorghum, and the forest areas farther south, where root and tree crops such as yams and kola nuts predominated. These quite varied environments provided the economic incentive for the exchange of goods.

The earliest long-distance trade within this huge region was not across the Sahara at all, but largely among the agricultural peoples themselves in the area later known to Arabs as the Sudan, or “the land of black people.” During the first millennium B.C.E., the peoples of Sudanic West Africa began to exchange metal goods, cotton textiles, gold, and various food products across considerable distances using boats along the Niger River and donkeys overland. On the basis of this trade, a number of independent urban clusters emerged by the early centuries of the Common Era. The most well known was Jenne-jeno, which was located at a crucial point on the Niger River where goods were transshipped from boat to donkey or vice versa. This was the Niger Valley civilization, described in Chapter 6.