Africa has a very smooth coastline, few natural harbors. The interior is on a high plain so rivers usually have waterfalls near the coasts. The rivers rarely meet up, like our Ohio and Mississippi rivers. The livable area is isolated by the Sahara, and the Atlantic and Indian Ocean.

This means isolation and no economic development. It means Neolithic people, sold into slavery by tribal chieftains as income. No wheel, no real numbers system, no alphabet (just grunts mostly).

And they are in our schools.