The West African kingdoms. One consequence of the Portuguese expeditions was contact with West Africa. The sub‐Saharan kingdoms—Ghana, Mali, Benin, Songhai, and Kongo—were well‐organized societies with a long history, but they were almost unknown to Europeans. Until the Muslim invasions of the eleventh century, the Ghana empire had extensive commercial ties with North Africa, Egypt, and the Middle East. Mali, an Islamic state whose capital Timbuktu was a major economic and cultural center, controlled the gold trade. The arrival of the Portuguese brought about a dramatic shift in the flow of African gold. Rather than going overland by caravan to North Africa and then into the coffers of the commercially powerful Italian city‐states, the precious metal was shipped by sea directly to Lisbon and western Europe.
The Portuguese were interested in slaves as well as gold. Arab merchants had bought slaves in West Africa as early as the eighth century, and they continued to act as middlemen when the Europeans arrived. Portugal used African slaves as early as 1497 in the sugarcane fields on the islands it took over off the African coast. Millions of blacks were shipped from West African ports to work plantations in North and South America over the next three hundred years. Slavery in the New World, justified on economic and racial grounds, was quite different from that in Africa. Although slavery was an accepted social institution throughout the continent, the slaves were typically prisoners of war, debtors, or criminals, and their condition was neither permanent nor hereditary.