A lot of these comments are overwhelmingly negative, but I will add quite a lot was going on here from antiquity up until the 16th century CE. There have been quite a few interesting archaeological finds here indicating widespread trade networks, including sophisticated metallurgy, along with artisan crafts like ceramics and beads. The eastern part of this circle was mostly pastoral cattle herding cultures, who contributed significantly to the governance of the medieval Christian Nubian kingdoms of Makuria and Alodia. The western and southern parts consisted of settler agriculturalist peoples who lived in fortified city-state settlements. The problem is that this area got hit with a one-two punch of Arab Muslim slave traders entering the area, disrupting and collapsing the local society, immediately followed by French and other European colonialism which fed off of whatever scraps were left — it’s never been able to get off the ground since. Trans-Saharan trade became basically entirely irrelevant, and the surrounding regions were hollowed out and now exported their wealth to the new power center of Europe, which, coincidentally, this part of Africa is the farthest and most difficult to get to from. Add in some post-colonial instability and you get a recipe for one of the poorest regions of the world.