Waterfalls - lots of waterfalls, on every river - kept Europeans out of the African interior. Rivers ran fast and far, but sediment kept them shallow. Crocodiles, hippos, piranha, pythons and poisonous snakes, reptiles and other dangerous river creatures scared the poop out of Europeans.

Traditionally trade in Africa was conducted by canoe and raft type vessels, rather than cargo ships and boats. Everyone had to carry their own food, supplies and equipment and row themselves up and down the rivers.

Europeans attempting to send their armies into the interior, lost them to disease, animals, starvation and people. Like the Europeans who settled in North America, Europeans in Africa sat right next to food and starved to death, because they did not know what was edible. They also died from eating the in-edible.

PS another good article, Mr. Engheim. I've missed you.