Aden Bahçesi, Great Lakes Earth

Question

(Set in an Africa on Alternate Earth 111, known conversationally as Great Lakes Earth)

Outlining the boundaries of Tanzania, Uganda, Burundi, Rwanda, Ehtiopia and Eritrea are a range of mountains called the Aden Bahçesi. Its highest peak stands 21,837 feet above sea level, 1500 feet higher than Denali. East of the mountains isn’t major lakes or rich savanna, but a highland plateau, more like Yellowstone.

(If you're curious as to why Turkey, Iran and Israel are marked in black, that simply means that they don't physically exist on Great Lakes Earth but are instead a portion of the Tethys Sea.)

Considering that, in this scenario, there is a plateau situated inside the equatorial zones, will its presence alter the way the tropical climate in central Africa works? Will East Africa still be the cradle for human evolution, or do we have to look elsewhere?

Answer 1

Weather in central Africa mostly comes in from the West, across the Atlantic ocean, so your highland/mountain region won't block those weather patterns, though any remaining moisture in those weather patterns will likely precipitate out as they move over the mountains. The western side of the mountains, where Zaire and Zimbabwe are found, will be wetter than they are while the Eastern plateaus, where Kenya and Tanzania are, will likely be much drier desert climates.

Map of African weather patterns on Earth.

It's likely that early hominids wouldn't be found in East Africa, for the simple reason that there is a giant range of mountains making travel to that area much more difficult. Hominid ancestors would have to migrate either around the Northern or the Southern sides of the mountains to live in East Africa. However, doing so would lead to encounters with different environments and different animals than those that coexisted with early hominids on Earth.

Given the nature of the changes to the environmental pressures that would then shape early hominids and their ancestors, it's impossible to say exactly where or how they would evolve into humans, but, assuming that the evolutionary pathway followed a similar trajectory as to what it did on Earth, it's very unlikely that humanity would arise in Eastern Africa.