ITT Newgrounds knows nothing about sociology, economics, geography, food production...
Okay, here's the skinny:
Africa (with an exception I'll mention later) has been historically economically crippled because of its geography.
If you look at the rich countries of the world, they almost universally are latitudinally similar to either a.) the Fertile Crescent (Persia and Mesopotamia) or b.) China.
The reason for this is because these cultures have access to a few specific founder crops (and animals!) by which the agrarian component of a society can be established.
Staple crops like wheat and rice are not as adapted to the sun, water, and soil conditions of places like Africa. These things can be grown in larger quantities and stored, allowing fewer people to work in agriculture and still produce enough food to support their community, freeing others to pursue other professions.
Also, while Africa has an abundance of animals, really none of the large herbivorous mammals were suitable for domestication. Even things one would think would be similar to Eurasian animals, such as the warthog, the zebra, and the water buffalo, are so behaviorally different (i.e. flightier, more aggressive, less capable of socializing with humans) that they are much more difficult to saddle or hitch to a plow.
TL;DR - the geography has meant that the people of Africa have to dedicate more resources to bare subsistence, leaving less with which to build a large, stratified society capable of producing greater material wealth.