Disease Patterns Before AD 1000

The prevalence and distribution of diseases in sub-Saharan Africa have been determined by the natural environment, indigenous living patterns, and the interrelationships between African peoples and newcomers from other continents. The spread of agriculture since about 3000 B.C.; the extensive commercial contacts with the Moslem world from about A.D. 1000, and with Europe since the fifteenth century; and the establishment of colonial rule in the late nineteenth century - all have had important consequences for health conditions in Africa.

There is little evidence about the disease environment confronting Africans until fairly recent times. Literacy dates back to only about A.D. 1000, and then only in Ethiopia and some areas of the savanna zone just south of the Sahara desert. Written accounts of conditions on parts of the western and eastern coasts begin with the Portuguese voyages of the fifteenth and sixteenth centuries, but literary information on most of the vast interior is not available until well into the nineteenth century. Serious medical data collection really began with the colonial period, but even today knowledge of disease incidence and prevalence is far from adequate.

Africa south of the Sahara is a vast area with many different ecological zones. Besides the Sahara itself, there are extensive desert regions in the Horn of northeastern Africa, and the Kalahari in Namibia and Botswana in the southwestern part of the continent. Tropical rain forest prevails along most of the west coast, in the Zambezi valley of Mozambique, and in large areas of western equatorial Africa, including much of Gabon, Congo-Brazzaville, and northern Zaire. Forest, however, covers only about 10 percent of the land area. Rolling grassland, often called savanna or sudan, predominates between the desert-edge lands and the forest, both north and south of the equator. The desert and the equatorial forest have always been relatively sparsely populated; most Africans have always lived in coastal West Africa or the savanna areas north and south of the equatorial forest.

Paleontological studies indicate that hominids almost certainly evolved in Africa, and our species, Homo sapiens, probably was widely distributed over the continent by at least 40,000 years ago. Scattered bands of stone-age hunter-gatherers spread lightly over the entire continent. Signs of permanent settlement by fishermen around lakes and rivers are evident in eastern Africa and places that are now in the Sahara from about 7000 B.C. Knowledge of stock-raising diffused from southwest Asia from about 5500 B.C., and agriculture followed the same course shortly afterward. The Sahara region did not begin to become a desert until about 2500 B.C., so these developments first reached peoples in and just south of the present Sahara. Here the new ways of life allowed the gradual development of settled village life, population growth, the rise of political and economic specialization, and, in general, the more complex societies associated with the Neolithic "Revolution." Iron technology diffused from the North African coast to what is now the West African savanna by about 300 B.C., giving peoples in the belt south of the desert, the ancestors of most modern black Africans, an additional advantage over more isolated populations further south.

As of the first or second century B.C., demographic growth among these iron-age, agricultural groups was encouraging them to expand southward against weaker, less numerous hunting and gathering peoples. Peoples ancestral to the modern pygmies probably dominated much of the forest. Further south were the ancestors of the Khoisans, who once inhabited most of the southern third of Africa, but are now restricted to parts of the Kalahari and bordering regions. In the west the farming peoples soon reached a barrier, the Gulf of Guinea, but members of one linguistic group in the borderlands of modern Nigeria and Cameroun had a continent before them. For roughly 2,000 years these technologically superior peoples have been gradually colonizing half a continent, driving away, killing, or absorbing most of the indigenous groups. The descendants of these people, speakers of languages of the Bantu family, now dominate most of the continent from the equatorial forest almost to the southern tip.

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