Eurocentric modern African history begins alongside the discovery of the New World. Europeans and the Church needed labor in abundance. Indians were susceptible to European diseases, and not suited to the hard labor that was demanded of the New World cash crops. Relying on the long stable Arab Slave Trade, Spain imported the first Africans to Hispaniola 1501.
At this point in history, Africans were a tiny minority of the world’s slave population. Most slaves were non-moslem Arabs; this included many captured Europeans of Barbary raids, traded across Northern Africa.
As labor demand ratcheted upward, more slaves were needed. Europeans pressed and plied African rulers or undermined local power structures to acquire their labor pool, and many slaves were created out of political enemies. Between ten and twenty million survived the Atlantic passage. In the New World, they faced disease and death.
The total number is inexact, and just as many slaves perished in the process of passage or capture. Tens of millions of people were removed from northern Africa, a depopulation of human capital unprecedented in scale. The Portuguese middle-men of the Atlantic Slave Trade would turn Africans into the overwhelming majority of the world’s slaves by 1800.