system
Given the following post, respond as if you're commenting on Reddit:
human
Why is there a history gap between Africa's civilizations?

In high school when we were covering ancient civilizations, once Egypt fell to the Greeks/Romans (can't figure which put the final nail in the coffin), we didn't see anything in Africa until either the Muslims took control of the northern part or until the slave trade with the colonies and later state in the southern US came into full swing.

I find it odd that I have never heard of any major civilizations, empires, or nations taking hold in Africa between the fall of Egypt (332 BC when the Greeks took over and 30 BC when the Romans did) and the slave trade (circa 1500's-ish). I'm ignoring when people from other parts of the world came to Africa and set up shop i.e. South Africa with its apartheid, Islam in northern Africa and eventually launching into southern Spain, various European nations carving up Africa during the age of imperialism, etc. I'm looking for civilizations setup by people from Africa itself, not by other groups.

From what I've read about evolutionary science, humans evolved in Africa, specifically the Ethiopia area, so it would stand to some logic that that area would be where the oldest nations and empires would exists but for the most part, Africa is one of the least developed places in the world.

I am by no means a historian, sociologist, archaeologist, or anthropologist, so I'm sure I've made a few mistakes in the examples above. What I paid attention to most during history class was WW2, figuring out which of my friends I would see that day, and how much longer till lunch.
gpt
Actually, the answer is that there isn't a gap.  Or rather, there's a "History' gap but not a 'history' gap.

In other words, once we separate History (the discipline) from history (the past as it happened), we can see that it's errors in interpretation and inadequate sourcing and methodology that makes it appear as if there is a gap where none exists.  There existed a continuous string of states, 'civilizations' (if you want), widespread and large-scale societies, between the era of Pharaonic Egypt and the modern period, but we fail to perceive it adequately in History.  Why? Several reasons.

1) The History discipline grew up hand-in-hand with colonialism, and hence many historians had a reason to deny or denigrate African historical trends and sophistication in the service of their paymasters and/or just out of discursive error in justifying colonial rule

2) Historical narratives, born in Europe, tended to recognize European styles of state and society better than alternate pathways and modes of organization.  In this kind of neo-evolutionary theory, for example, V. Gordon Childe could demand that a zone only be recognized as a 'city' if it had monumental architecture.  Only in the 1970s did archaeologists (like the McIntosh's) show that many African zones were densely populated urban sites that had a decentralized political structure, but were nevertheless 'cities'.

3) The History discipline preferenced writing, and writing was not generally a major feature of large-scale societies in Africa south of the Sudan and away from the coasts until much later than in Eurasia.  HOWEVER, this does not excuse our ignorance of literate states and societies in Ethiopia, along the East African coast, etc dating back many many thousands of years.

Although it apparently hasn't reached the general public, scholars have generally reconstructed some pretty good, well-supported analyses/narratives of sub-Saharan African history throughout this period by converging archaeological sources, historical linguistics, and to some degree oral tradition.  You should check out the work of Chris Ehret and Jan Vansina to start.  They are usually opponents of each other on the details, but they are both major contributors to this task. There are many others, from Kate de Luna to Kairn Klieman. Their work is worth reading.