10 million in the trans-Atlantic trade. And perhaps 5 million to the east across the Indian Ocean. By the 19th Century, virtually no area of the continent was free from slaving. Some societies disintegrated. Most were at the least severely destabilized.
Some scholars propose that disease was even more destructive.
European began ethnographic studies. Christian missionaries began spreading through Africa. They were most succesful where there was no competition from Muslims, where social structures were breaking down, and where they could organize and discipline the Africans. The African sense of hospitality enabled scientists, missionaries and traders to move relatively freely into the interior. Prices declined, and African middlemen were squeezed out.