I mean they never invented anything at all!
I don't count picking up a rock or stick to bong each other as an invention. Even today's apes do that, and they aren't showing any signs that they will ever ‘evolve’ into anything smarter.
Regarding the apparent lack of inventions and technology in Africa... well, even as a little kid I had the notion that living in a widely varying climate made people innovative. Those who survived innovated ways to stay warm through icy winters and hydrated through hot, dry summers. They survived long enough to reproduce, and their kids improved on the innovative parents’ innovations and they survived long enough to reproduce. After thousands of years of this cycle, the Europeans brought many good things to life. And having the Christian message of love to fill their spiritual needs, meant Europeans got less bogged down in bizarre superstitions that kept Africans and American Indians literally in the dark about real world problems and solutions. Really, there is no reason for humans to waste their energy worshiping mountains and animals.