Where are the great monuments and buildings? Where are the great works of art and literature? Where is there even evidence of a written language?
The cities of Timbuktu, Djenne, and Gao have preserved historical sites that date back into the 12th century. They were major trade cities and Timbuktu was noted as a city of scholars (Sankore was one of the major centers of learning), at one point having almost a quarter of it’s population as students of some kind. Hundreds of thousands of pages of scholarly works still exist.
During European colonialism, much of the history of these locations and former empires was either suppressed to keep the colonies under the heel of the French and Belgians who controlled the area or were dismissed as fanciful tales by European based scholars.
But archeology and historical examination show that the Ghana/Mali/Songhai empire thread held a large part of western Africa from around the 4th century until the late 16th century and the major cities of Timbuktu and Gao were important centers of trade and power from the 10th century into the 16th century.
Great monuments and buildings.
http://www.cnn.com/2013/06/27/travel/rock-churches-lalibela-ethiopia/index.html
Evidence of written language
https://www.britannica.com/art/Ethiopian-literature