Throughout pre-Roman history, North Africa and the Middle East had its fair share of civilizations--not just the popular Egyptians, but also the Carthaginians, the Sumerians, the Assyrians, the Babylonians and the Hittites. The reason that there were so many civilizations in so small area sizes is simple--they built their cities in deserts! Even on the Mediterranean coast, the environments in Israel, Syria, Lebanon, Jordan and Iraq are so extreme that farming and irrigation would require an extra degree of ingenuity.
Things are no better off in the Sahara, either. Highs average around 104 degrees Fahrenheit, it is sandy mixed with rocky and the Nile, as far as I know, is the only river that can cut through the desert rock and sand and to the Mediterranean.
In this alternate Africa, things are a little different. For starters, North Africa is 100% rock, which means none of the sand dunes that made Arabia or the Sahara so notorious.
North Africa has its own series of Great Lakes. (Though this map does not take rivers into account, and Lake Chad, in this scenario, is not of an accurate shape or area size.)
A more accurate Lake Chad. (Again, the map does not take rivers into account.)
In this alternate Earth, Arabia is a mere extension of northeastern Africa, erasing both the Red Sea and the Gulf of Aden off the map. Also, the mountains are arranged differently. The Atlas Mountains still stand by the Sahara’s northwestern coast, but they are taller — the tallest peak being 21,810 feet above the level of the sea, 1500 feet taller than Denali. Outlining the coasts of Angola, Namibia, South Africa, Mozambique, Tanzania, Kenya, Somalia, Yemen and Oman is a range of volcanic mountains called the Aden Bahçesi. Its highest peak stands 24,341 feet above sea level, 1500 feet higher than Aconcagua back home. All of Africa’s rivers originate from those two mountain ranges.
Now let's take the possible effects of civilization into account. Would these changes create larger civilizations, perhaps even full-blown empires (at least before the Macedonians and Romans marched along)?