Aravinda,

I am no early man or hominid expert, just an archaeologist. Two branches of a Homo erectus exodus out of Africa could both have the genetic mutation that resulted in Homo sapiens springing up in two different location, it is probably highly unlikely, but possible. Three or more locations to have the same genetic mutation would be near impossible. Recent DNA testing indicates that Homo Sapiens left Africa, but some of them returned many thousands of years later.

On purely speculation, what could be a more likely scenario is that an early predecessor to Homo sapiens left Africa, developed into Homo habilis or another species, then returned to Africa where they then continued to changed until Homo sapiens developed. Hominidae appear to have developed in what would become southern Europe, southern Asia/India, and eastern Africa. There were Hominids in India knapping Acheulean artifacts during the late middle Pleistocene. Could a species develop in the Ganges River Valley or Yellow River Valley and then return to Africa to further develop while that lineage died out?

The question also is how complete is our fossil record? At this point not very complete at all. Do we find more early fossils in eastern Africa because of better preservation than some other locations, like India or China? I am sure someone has looked into that. Still, we possibly have fossil evidence for only a tenth of the Hominid line, maybe more, maybe less. While paleoanthropologists have sequenced the fossils that we have, it is now looking like there were many hominid species running around Africa at the same time. Who knows how many more branches and dead ends of the family tree there are as yet undiscovered. And why Africa? More biodiversity? More competing species? More competition period?

Here are some articles.

https://www.newscientist.com/article/dn18093-chinese-challenge-to-out-of-africa-theory/

http://www.dailymail.co.uk/sciencetech/article-1341973/Did-humans-come-Middle-East-Africa-Scientists-forced-write-evolution-modern-man.html

http://www.en.uni-muenchen.de/news/newsarchiv/2012/2012_cysow.html

http://phys.org/news/2012-02-africa-language.html

https://www.edge.org/conversation/rethinking-out-of-africa

Regards,

Joachim

The article is getting a bit dated.  We now know that humans interbred with Neanderthals and Denisovans.  Technically this violated the original tenets of the Out of Africa model.  The model has since been revised somewhat to account for this interbreeding while maintaining that modern human origins are in Africa.  I think we may find additional interbreeding events with the hominins outside of Africa.  

With the genetic and archaeological evidence we have now, it is clear that there was a main exodus from Africa about 60,000 years ago, with low levels of interbreeding with Neanderthals in the Middle East and Europe and with Denisovans in Asia. What is not certain is whether there was also an earlier dispersal from Africa during the interglacial around 100,000 years ago. At that time anatomically "near-modern" Africans made it into the Levant, but were displaced by Neanderthals when the climate got colder again. It is possible that during that interglacial there were groups of near-modern Africans migrating into Asia, and there is evidence for their genetic traces in a Neanderthal from the Altai Mountains (but not European Neanderthals). Perhaps there were pockets of modern humans in Asia since that time that persisted relatively unadmixed and were later absorbed into the new wave that left Africa 60,000 years ago. We just don't have the fossils.  

Aravinda,

What concerns dental morphology, there are excellent works on the evolution of human dentition, particularly on European and African taxa (pre-sapiens and sapiens). Specifically addressing the Out of Africa problem, you should really see some work by Joel Irish (also member of Researchgate) and colleagues. 

I suggest you check the following:

http://www.sciencedirect.com/science/article/pii/S0047248403000903

http://www.sciencedirect.com/science/article/pii/S0047248497901913

His PhD work is also an excellent source of information although he addressed specifically modern humans:

Irish JD. 1993. Biological affinities of Late Pleistocene through Modern African aboriginal populations: the dental evidence. Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy.

Best, 

Claudia

Gerhard,

You mentioned "there is evidence for their genetic traces [near-modern Africans'] in a Neanderthal from the Altai Mountains (but not European Neanderthals)" in your answer above. Very interesting! Do you have references for this? I'd love to read.

Thanks,

Claudia 

PMFJI,

http://www.nature.com/nature/journal/v530/n7591/full/nature16544.html

http://www.nature.com/nature/journal/v505/n7481/full/nature12886.html

https://www.theguardian.com/science/2016/feb/17/oldest-known-case-of-neanderthal-human-sex-revealed-by-dna-test

Regards,

Joachim

https://www.nature.com/articles/s41586-019-1376-z

https://www.nature.com/articles/s41586-020-2509-0

Regards

Kalangi