Rethinking “Out of Africa”

Out of Africa

Neanderthals separated from humans, Homo Sapiens, about 400,000 years ago, but then, in Eurasia, the two species, who were believed to be unable to interbreed, came back together again, and did.  We know this because every population in the world, except for Africa, carries both Neanderthal and/or Denisovan DNA, including aboriginal people from Australia.  This information, newly discovered in the past year or so, raises a lot of thorny questions.

Neaderthals have been grouped as a separate species from Homo Sapiens, modern man, and members of two different species, by definition, are not supposed to be able to interbreed and have fertile offspring.  So are Neanderthals and Homo Sapiens really the same species?

Neanderthals, as a separate species became physically extinct about 30,000 years ago, at least we can no longer find fossil records of them.  But did they really, or did they simply assimilate and genetically, and physically, become the new us?

And if that wasn’t enough, there are the Denisovans and they too interbred with Homo Sapiens.  In fact, Denisovan and Neanderthal bones have been discovered together, and Denisovans are believed to be an offshoot of Neanderthals.  And what about the Hobbits of Flores Island?  Where and how do they fit in?

And there are probably more surprises that await us, because there are more fossilized bones that we have not been able to obtain DNA from that don’t match any of the groups mentioned above.  In the future, discoveries of fossilized bones will likely be made that from which we will be able to recover DNA, as the recovery techniques improve.

But what does all of this mean?  How does it affect what we knew, or thought we knew, about the “Out of Africa” theory that says all contemporary man evolved in African, left Africa and subsequently killed off or replaced all of the other species, such as Neanderthals?  If that’s not true, what is true?  Did we evolve out of African several separate times, getting reacquainted some several 10s (or hundreds) of thousands of years later on another continent?

All of this unexpected mixture causes lots of questions, and today, we don’t have many answers.  But maybe the biggest question is that of what, exactly, is a modern human?

CHRISTOPHER STRINGER is one of the world’s foremost paleoanthropologists. He is a founder and most powerful advocate of the leading theory concerning our evolution: Recent African Origin or “Out of Africa”.  He has worked at The Natural History Museum, London since 1973, is a Fellow of the Royal Society, and currently leads the large and successful Ancient Human Occupation of Britain project (AHOB).  His most recent book is The Origin of Our Species (titled Lone Survivors in the US).

Here’s what Christopher has to say:

“At the moment, I’m looking again at the whole question of a recent African origin for modern humans—the leading idea over the last 20 years. This argues that we had a recent African origin, that we came out of Africa, and that we replaced all of the other human forms that were outside of Africa. But we’re having to re-evaluate that now because genetic data suggest that the modern humans who came out of Africa about 60,000 years ago probably interbred with Neanderthals, first of all, and then some of them later on interbred with another group of people called the Denisovans, over in south eastern Asia.”

To read more of Christopher’s thoughts, click here.  They are very interesting and enlightening indeed, from a man who has been in this field since the beginning, a mere 40 years ago.

11 thoughts on “Rethinking “Out of Africa”

  1. The Neanderthals and the Denisovans also came from our common ancestor 400,000 years ago in Africa. I know you know this, Roberta, but for anyone else who is wondering, none of this changes that we are still all part of the same human race.

    • Denisovans are most closely genetically linked to Australian Aborigines. There is no evidence of them being of African origin.

  2. Great article, Roberta. I had just read another article from Chris Stringer which Brian Swann and I were discussing. I find his view fascinating. Another interesting person Brian suggested I read is Dr. Nick Lane and his view on the importance of the mitochondria to the origin of life, providing the necessary energy to the cell for it to develop. Keep these great articles coming

  3. I think everyone should get a copy of The Gene Code, if you have not already bought a copy.

    To understand how evolution came about from the very primitive archaea right through to us, and how the basic skeletal building blocks of all mammals are the same is quite something to capture. We almost never get the subject of mitochondrial bioenergetics and its critical role in evolution discussed. It is what mtDNA is all about – but the DNA is not sufficient in itself. That just helps code for some, but not all, of the 50 or so proteins which span the mitochondrial membrane to provide the electron transport chain. It is the redox centres of the complexes involved which are important and DNA does not directly touch those. And how many folk who post in these forums have ever heard of Dr. Peter Mitchell and his chemi-osmotic hypothesis relating to mitochondria and energy production, even though he got the Nobel Prize for his work.

    As The Gene Code explains beautifully, at heart we are basically four worms and bioenergetics is critical to complex life. And Prof. Steve Jones has a great line on Evolution by Creeps versus Evolution by Jerks.

    http://www.bbc.co.uk/programmes/p00gfy1d

    Brian

  4. And Adam called his wife’s name Eve; because she was the mother of all living. Genesis 3:20
    Therefore is the name of it called Babel; because the LORD did there confound the language of all the earth: and from thence did the LORD scatter them abroad upon the face of all the earth. Genesis 11:9

  5. As scientists have to keep relearning – they don’t know as much as they would have us think they do. A bit of humility would do “Homo scientus” a world of good.

  6. Very interesting. Ive long believed that there were Neandertal and Homo Sapien crosses.
    The more we learn, the more questions we have.

  7. Roberta

    Your blogs just keep getting better and better. This is really, really interesting. It takes me back to my original interests before I got caught up in the “Sputnik, Race To Space”. But it has all been a good ride and now with your help I can spend time looking within rather than out.

    Tom McKee

  8. Neanderthals and Denisovans are simply 2 groups of humans that intermingled with other groups, not two separate species. For a scientist to spend time on the basis of a theory that has been debunked time and time again is truly incomprehensible to me. Is it because they are caught up in their own “new discovery” competitive ego that they have succumbed to making things up? Why make things up when the evidence is already there ?

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