Two great divides have marked the last seven millennia in Africa: the transition to food production and the modern revolution in the means of communication. The impact of these innovations was by no means felt simultaneously throughout the continent. A few people living in the most inhospitable areas have yet to participate in the first, but the vast majority of Africans were already pastoralists or agriculturalists long before the end of the first millennium AD. The impact of the second, nineteenth-century revolution was more immediate, though certain aspects of communications were already being influenced by much earlier developments. In successive millennia, trade-links within Africa had been profoundly affected by the Phoenician, Arab and Portuguese explorations of, respectively, the North African, Indian Ocean and Atlantic coasts of Africa. North of the equatorial forests, the camel and the horse had increased man's mobility, and Islam had brought literacy to a restricted few. But until the transformation which began, not with colonial rule, but with the steamers, railways, telegraph, vernacular bibles and newspapers of the nineteenth century, communications throughout most of sub-Saharan Africa had remained largely dependent on oral messages and human porterage. Until the nineteenth century, the pace of change was not dependent on an alien technology. The main lines of communication lay not with the outside world, but within the continent itself.

Compared with these watersheds, the year 1600 marked no noticeable break in continuity; yet in some important respects the seventeenth and eighteenth centuries in Africa do constitute a period of transition, distinct from both the sixteenth and the nineteenth centuries.