The speed of human migration is quite rapid, and East Africa merely accelerates this process, provided there is a sufficient population for East Africa to allocate, which is something Henry Barkley could hardly imagine. Thus, Henry Barkley proposed the north-south river hypothesis.
Without knowing the population size of the East Africa Kingdom, he referred to the migration speed of the Cape Town colony and concluded that the population of the East Africa Kingdom wouldn't be too large. After all, the East Africa Kingdom had been established for just under two years. Even counting the colonial period, it's only been a few years. In such a short time, having a population of several hundred thousand in East Africa would be considered quite good.
