Sub-Saharan Africa remained isolated from the main currents of world trade far longer than most of the rest of the Afro-Eurasian landmass. Even though Asian sailors reached much of the eastern coast by about 200 B.C., North Africans regularly crossed the Sahara by about 800 A.D., and European sailors reached the western coasts in the fifteenth century, much of the interior remained comparatively isolated until the eighteenth and nineteenth centuries – cut off by the aridity of the Sahara and its own patterns of disease environment. Tsetse flies and the trypanosomes they carried made pack animals useless through much of the African tropics, thus impeding long-distance trade. Other diseases, especially falciparum malaria and yellow fever, were so fatal to humans from other disease environments that Africa remained the continent least known to outsiders until the second half of the nineteenth century.

Textbooks and other summary treatments of African economic history sometimes illustrate the “penetration” of Africa with maps showing arrows leading from the coasts into the interior – from Egypt up the Nile valley, from the east coast into the highland lake region, from the Maghrib across the Sahara to the western Sudan, from the Atlantic coast into the Congo basin. Such maps are accurate enough to show the flow of foreign goods. Arrows in the opposite direction could also show how African goods and people moved along trade routes to the outside world. But intercontinental trade was only part of the whole. In Africa, as elsewhere in the world, local exchange was more important than long-distance trade.