Problem 1: Look at the map of Africa before 1500. What about all the different countries or kingdoms which existed? Does the gray area mean that no one lived there?
Problem 2: What about Africa's world trade situation in 1500? By the way, the red lines indicate overland routes for trade, and the blue lines indicate the much easier water routes to get to India and China.
Problem 3: What about the world-wide practice of slavery? Even the Jews participated. Look at Exodus 21, where it says "The Treatment of Slaves."
Problem 4: What about the different types of slavery?
Problem 5: What about the trans-Atlantic Slave Trade as a business?
Problem 6: What do you think about the colonization of Africa by the Europeans in the late 19th century?