Is the river Nile THE major flaw in the Out of Africa theory?

Question

The OOA theory requires hundreds of millenia of reproductive isolation between African humans and others like Neanderthals and the Asain Erectus. As far as I've been able to tell, the Nile has always flowed (in a human evolutionary time frame), making a corridor from the AM humans in the horn of Africa and the Neatherthals in the North of Africa and the Levant.

Were they ever really seperated genetically?

Answer 1

The fact that an apparently separate species of hominid, Neanderthal, evolved over the last several hundred thousand years indicates there is at least somewhat of a barrier unless two species evolved sharing the same territory.  As unlikely as two species sharing the same territory forming new species sounds, that is exactly what is suggested by sticking to the pure Out of Africa explanation when you have Homo habilis coexisting with erectus ~1.4 million years ago in Africa.  It might be evidence of greater geographic separation or easier species formation than would seem likely without that evidence.  The habilis coexisting with erectus puts a serious dent into the pure "Out of Africa" explanation because it is easier to explain species formation with greater geographic separation.

It is entirely possible that the African Heidlebergensis or rhodesiensis were replaced by some version that originated in Asia or Europe.  In any case they apparently came to dominate Africa, Asia and Europe several hundred thousand years ago when we apparently shared a common ancestor with Neanderthal.  In my opinion, there would probably have been enough movement back to Africa to transfer any genes that significantly contributed to survival but not enough to prevent isolated races to develop that were either genetically incompatible or isolated in some other way.  Not only do you have the Nile being access, you also have periods where the dessert was not so hostile. Modern humans and Neanderthals didn't become genetically incompatible, if at all, until until recently.

Answer 2

The Nile has been both a barrier & corridor to homo migration.  One could hardly expect casual crossing during early homo migration.  Geographically some degree of isolation obviously happened due to distance alone, but how much is debatable. I suspect each tribe or group had extensive contact with the groups closest to them, but had diminishing contact with others based on distance. We know they traded with distant groups & it is most likely that some DNA was traded along with goods from distant places.

I am hoping for further research toward sequencing both neandertal & erectus genomes. So far we've no answer for the differing genes that are more than 1 million years old, but suddenly appear in the sapien genome in various geographical locations. One has to "at least" suspect some degree of introgression from a more ancient line of Homo.

Answer 3

after many millions of years the Eastern part of Africa including

Egypt,Ethiopia,Somalia,Eritrea,and Kenya will be another

continent because of the Nile and Rift valley