Great apes with small brains were not very mobile

Allan Krill

Including the human, there are now 13 living taxa of great apes. Except for the human, the great apes are not very mobile. We can be certain that each taxon now lives in the isolated area where it evolved. There were once many other taxa of great ape between Indonesia and Central Africa, but they are now extinct.

     (last common ancestor about 6 Ma?)
Western Chimp
Nigeria-Cameroon Chimp
Central Chimp
Bonobo (Pigmy Chimp)
Eastern Chimp
     (last common ancestor about 10 Ma?)
Cross River Gorilla
Western Lowland Gorilla
Eastern Lowland Gorilla
Mountain Gorilla
     (last common ancestor about 15 Ma?)
Borneo Orangutan
Sumatra Orangutan
Tapanuli Orangutan

Genetic studies show that the human is closely related to the chimp, next closely to the gorilla, and next to the orangutan. 

The human, after its evolution, had a remarkably large brain. With that brain, it was able to invent shoes and clothing, and tools for defending itself and carrying water and food. Those inventions enabled it to spread out and populate the entire globe. Because of its current spread, we do not know the area where the human evolved its large brain. Since it was small-brained and not yet mobile, the place was presumably near one of the chimp places.

Fossils show that early humans (Homo erectus, Neanderthals, Denisovans, and Homo sapiens) migrated great distances from where they evolved. Genetic studies of living humans show that the area of their origin was somewhere in Africa.