It just occured to me that I know a bit about the trade networks down the Red Sea and towards India, but to what extent did such networks exist across the Sahara? The Carthaginians sailed down the coast as far as (maybe) the Congo, but was there trade along that coast? Across the desert?
I've written about this a bunch of times, and I can't find my last posts.
Broadly speaking, the part of the Sahara south of the Roman section was controlled by the Garamantes, often called a "desert tribe" but in fact a supremely sophisticated kingdom possessing a highly advanced desert agriculture and an urban core. The Garamantes seem to have been consumate traders, and at their sites are often plenty of wine amphorae. We can tell that the Garamantes raided at least as far south as Lake Chad, but farther south than that is a bit unclear. There were complex, urban civilizations along the Niger river at the time, and it is certainly likely they came into contact with them, but beyond that the information just isn't there.
I have written about this a few times, here is a recent writeup.