How are you defining civilization?
That may seem like an off question- but its one of the first ones I make students answer whenever I teach 'History to 1500.' Our definitions of concepts like civilization determine how we talk about people and who we might even talk about.

Aside from choosing a definition for 'civilization,' which can be tricky as many dictionaries differ slightly in their definitions- right off the bat overlapping territorially with Aksum (or Axum) was the Kush who existed at least in some form since 1000 BCE until their conquest by Aksum. They were major adversaries/trading partners with Egypt. Also in that general area- on the East African Coast, likely near modern day Somalia, was Punt who the Egyptians seem to have been trading with as early as 2000 BCE. Certainly by the reign of Hatshepsut around 1500 BCE trading along the East African coast was a comparably brisk affair and by the turn of BCE to CE, the beginnings of an Indian Ocean trading network begin to take shape as evidenced through genetic mixing of crops and animals- which becomes clearly evident by 700 CE.

These are both simple examples found in most modern World History textbooks. If an African specialist happens across this question, then I bow to their expertise.