Africa is a continent of great size, almost 12 million square miles about three times the size of the United States. Most of it lies in the tropics and, although we often think of Africa in terms of its rain forests, less than ten percent of the continent is covered by tropical forests, and those are mostly in West Africa .Much of the African surface is covered by savannas ,or open grasslands, and by arid plains and deserts. In geological terms, the continent is really formed by a series of high plateaus broken in the east by the Great Rift valley and the mountains that surround it. Large rivers - the Congo, the Nile, the Zambezi, and the Niger - begin in the interior of thecontinentandflowtotheseaovergreatfallsandcataractsthamarkthepassage from the plateau to the coast. These falls have historically made movement from the coast to the interior difficult, but the great river systems have also provided the interior of Africa with routes of communication.
We have already noted the origins of humankind in East Africa where some of the earliest fossil remains of proto hominids have been found. Even before the appearance about 300,000 years ago of Homo sapiens, the ancestors of modern human beings, other hominid species, such as Homo erectus, had moved outward from Africa to Asia and Europe. Africa, therefore, holds a special place in the development of the human species. It was the scene of human origins. Moreover, in cultural terms, Africa participated in the early development of civilization.
Despite the false image of Africa as the "dark" and isolated continent ,it was, in fact, often in contact with other areas of the world. It received from them technology, crops, ideas, and material goods that in turn stimulated social and cultural innovations. Moreover, the contacts were not always in the same direction, and there is now considerable evidence that not only early humans but also certain languages, crops, political, and cultural influences