Paleoanthropologists are certain Homo sapiens originate from Africa. However where in Africa is still contested. Could you give the reasons why it is thought that Homo sapiens evolved in Eastern Africa, Northern Africa and Southern Africa?
The reason is that the oldest and most primitive proto-human signs of life have been found in Africa. The seminal research was done by Louis Leakey, an anthropologist. It is possible that older forms of life may exist undiscovered in other places, but so far the evidence for that is scant.
Part of the challenge is that many geographic areas feature acidic soils which will eventually dissolve bones, which are composed of calcium carbonate, so it requires a neutral or slightly basic soil to preserve bones over millions of years.