We must identify the different levels of enslavement in the historical narrative of Africa. Some where client-supplier, others were consequences of the overspill from internal polities clashing. Although the internal African trade became the trade which procured captives for Europeans and also
Arabs, it is a distinctive trade with unique features, and moreover distinctive consequences.
Economically the growth that should have been experienced in Africa, from African human resources, was experienced in the West - as opposed to in Africa. The primary African groups involved in procurement for European interest became particularly adept and brutal at the practice of enslavement and through the centuries developed a militaristic culture. Prime groups engaged in this were Oyo, Benin, Igala, Kaabu, Fante Confederacy, Asanteman, Dahomey, the Aro Confederacy and theImbangala professional war bands. (
"Atlantic Warfare", Thornton) One key difference between Africans as agents for Europeans, and the domestic internal slavery was the level of brutality associated with procurement. The gradual abolition of slavery in European colonial empires during the 19th century industrialization era led to the decline of these African empires.
http://www.africanholocaust.net/html_ah/holocaustspecial.htm
Since 1482, the Portuguese who were interested in obtaining Asante gold, had opened a trading port at El Mina. As a result, their first slave trade in West Africa was with the Akan people. The Portuguese bought the slaves from the kingdom of Benin, near the Niger Delta in Nigeria. Slave labour made it easy for the Akan people to shift from small scale agriculture to large scale agriculture (Giblin 1992). The shift transformed the Asante kingdom and it developed a wealthy agricultural and mining economy.
The Akan people needed slaves to work their gold mines and farms. Passing traders and a growing population in the Asante towns demanded increasing supplies of food. The slave trade with the Portuguese continued until the early 1700s. The Akan people supplied the Portuguese with slaves to work on sugar plantations in Brazil. A small number of slaves were kept in the Asante kingdom. However, by this period, the Atlantic slave trade dominated trade with West Africa. Kingdoms like the Asante and Dahomey used their power to raid societies like the Bambara, Mende, and Fulanis for slaves.
The kingdom of Benin is the only known kingdom in West Africa to abolish slave trading in Benin. The slave trade ban was succesful and forced the Portuguese to search for slaves elsewhere in West Africa. However, Dutch traders took over the role. From the 1600s the Dutch dominated the West african and Atlantic Slave trade.
http://www.sahistory.org.za/topic/songhai-african-empire-15-16th-century
so you ignore the politics in history like some kingdoms selling slaves and others not? The lie in history is that we only descendants of slaves, and savages before that. Africans spread out into N. America around like 1400 (white historians are conceding this now), and its likely they were elsewhere around the world before that. But 300 million people were bought, shipped, and resold in Europe, the America's and the Middle East.
edit: i guess i have to mention, not cac sites