Yeah, it’s completely ridiculous. Lake Victoria completely dried up though, 12K years ago, and the Sahara dried out to the point that Lake Tritonis was nearly but not quite gone when Herodotus visited Africa.
Herodotus also pointed out the Pygmies were living in the area around Lake Chad.
A question that I have asked many times is, Why Remnant Peoples in South Africa, the Adman Islands, and others are pushed out by others from NE to South.