Africans and the Slave Trade

Henry Louis Gates, in the oped Ending the Slavery Blame-Game, discusses an issue that advocates for black reparations overlook, namely, Africans' involvement in the slave trade:

While we are all familiar with the role played by the United States and the European colonial powers like Britain, France, Holland, Portugal and Spain, there is very little discussion of the role Africans themselves played. And that role, it turns out, was a considerable one, especially for the slave-trading kingdoms of western and central Africa. These included the Akan of the kingdom of Asante in what is now Ghana, the Fon of Dahomey (now Benin), the Mbundu of Ndongo in modern Angola and the Kongo of today’s Congo, among several others.