The 60,000 year old exit from Africa…that makes no sense at all.

It’s claimed to be about 60,000 years ago from the Horn of Africa..

Let me just say I’m with Stephen Oppenheimer on this one. That ‘60,000 years ago’ exit date is pretty impossible, for several reasons…

  • The age of the haplotype M mutation, occuring in the Pakistan? area is dated to 64,000 years ago at least.
  • There’s a modern human skull in Luijiang China 68,000 years old (at least) and quite likely older.
  • There’s evidence of modern humans under the mount Toba explosion 74,000 years old in the Malay peninsula
  • There’s evidence of modern humans on top of the Toba Ash, suggesting the population didn’t die out in East Asia
  • The age of Y chromosome Adam in Africa is estimated to be 60,000 BP 4,000 years after the date of the M mtDNA mutation in South Asia. There were also people in Far East Asia by then. They must have some men not descended from Y chromsome Adam to keep going, but they are not present now.  If that isn’t proof of selection in Y chromosmes I don’t know what is.

A good look at the Mt DNA of Pakistan and India shows some L haplotypes present in Asia, so it seems a good amount of lead time can be added to the 64,000 years date, as haplotype L ‘s seems to have got there a while before. Also, In an age that great for the estimated date of a MtDNA haplotype, even a minor percentage error can add up to ten thousand years and more.

After reading some of his articles, it seems Oppenheimer is behind the colonisation of Australia at the low tide date of 65,000 years. He then worked out that you’d need at least 10,000 years to reach there from Africa.

Add this 10,000 years to the 74,000 date (Toba date) and this gives you at least 85,000 years BP from the Gate of Tears (Red sea).

So essentially, you are looking at an exit date of at least 85,000 years and probably a lot older.

There’s also the issue of ‘was there really one exit ?’ To my knowledge the Nile has always flowed into the Mediterranean, making a permanent route to the Mahgreb. There does seem to be an early seperation of Mt DNA haplotype N and M, one swinging North into central Asia (from a Nile exit?) and the other following the coastal route into Australia.

This brings me to the issue of modern humans in North Africa, in Jebel Irhoud, dated to 160,000 years years ago. If modern humans were in North africa then, how did they first exit sub Saharan Africa 100,000 years later? Another seeming impossiblity. There still seems to have been a human population there 82,000 years ago, they left bones and beads.

This all leads me to question the validity of ‘one recent exit by the Gate of Tears’ quite deeply. Thismistrust of it is made stronger by a couple of studies that have concluded mt DNA is subject to natural selection, and is not a neutral marker, so it’s entirely possible for less successful lineages to die out (there’s evidence climate affects what lineages thrive).

One DNA study I’ve seen based on other DNA markers dated the split from the East African population at 120,000 BP, and the European split from Asians at about 40,000 BP. This would roughly fit the presence of modern humans in Israel at Skhul, at 125,000 BP. It also matches roughly the date at which Europeans started moving into Neanderthal territory, so I’m inclined to support this, and assume that the MtDNA dates are very wrong, for the older clades at least.

Then there’s the issue of Mungo man, mt DNA from him showed he wasn’t descended from mitochondrial Eve.

It has to be remembered that the world wasn’t empty of people at this time. Asia was full of Homo Erectus, and from Europe into Siberia there were Neanderthals. This wasn’t just a case of expanding into an empty territory, they had two subspecies (or races, the jury is out on that one) to wipe out. This would add to the time it took to get from A to B.

This also raises the point ‘were we ever really genetically isolated from Neanderthals and Homo Erectus?’, as AMH’s seem to have been mooching around in North Africa nearly the whole time before we officially exited Africa. The fact that the Jebel Irhoud remains were initially misidentified as Neanderthal should be a clue to the answer

The out of Africa theory makes no sense at all. Beats me how it remains the accepted paradigm.

6 responses to “The 60,000 year old exit from Africa…that makes no sense at all.

  1. Another mistake many supporters of the single exit from Africa make is that they seem always to assume that both the Y-chromosome and mtDNA original haplogroups must have left together. MtDNA lines tend to be older that Y-chromosome lines in most regions. Let’s assume that this has been so throughout history, and prehistory.

    Mitochondrial lines M and N may have divergerged outside Africa before the mutation defining Y-chromosome line A had even happened. They may even have remained in the Middle East, and been absorbed by Neanderthals, when these temporarily replaced ‘modern’ humans around 70,000 years ago.

    Mention that in public and you will be howled down.

  2. There was an article a while ago explaining just how dubious the idea of Y chromosomes are as a neutral DNA marker. There are lots of genes on a Y chromosome to give an advantage, and one Y DNA type (IJ) is extinct and DE nearly is. There’s also one country in South America (can’t remember which) that had absolutely no trace of native Y chromosomes when they did a DNA study, but plenty of Mt DNA, which shows it’s easy to lose lineages.

    There was an interesting study into X chromosomes that showed one Eurasian (not seen in Africa at all) X chromosome was massively different, with a an age to MCRA of about 1 million years. Tell me THAT’s not evidence of interbreeding.

    The OOA theory is pretty weak, it’s like a balloon,it only takes one interbreeding incident to invalidate it.

    Personally, I’m for the ‘weak Eden’ theory, low levels of introgression from archaics, with a way older exit date than 60k.

  3. “Personally, I’m for the ‘weak Eden’ theory, low levels of introgression from archaics, with a way older exit date than 60k”.

    I’d totally agree with that (presuming you mean another exit date, more recent than the original H. erectus exit!). Besides which there’s probably been more than one exit from Africa, and several into it, since H. erectus times.

    Anthropology blog has several recent blogs and comments regarding extinct indigenous Y-chromosomes in various Carribean islands. I presume you’re familiar with the site. I’m pretty sure someone there mentioned the mainland country involved.

  4. Thank you for the pointer Terry, I couldn’t remember where I’d seen it!

  5. Sorry for the nitpicking, but in articles and comments here and nearly everywhere (!!) I see the term “modern humans” thrown around loosely. Does this mean “Homo sapiens”? Does it mean L2, L3 and beyond?

    And then there’s the term “early modern humans”. Linnaeus help us! Is this “Homo heidelbergensis”? Or is it pre-L2 Homo sapiens?

    Many times I lose the logic of someone’s argument because of this terminology. The press of course is the MOST guilty of this, but anthropologists do it also, annoyingly.

    So, then, if “Multi-regionalism” is correct, did the Out-of-Africa L3-M-N folks mix with:
    a) prior emigrations of Homo sapiens;
    b) Homo erectus, heidelbergensis & neandertalensis; or
    c) both a) and b)?

    • Once you get into modern human mt DNA types, yes they are anatomically modern humans. So from L0.

      A very old skeletion in Australia (Mungo man) has mt DNA not descended from mt Eve. Mt DNA has also shown itself to be subject to natural selection. As for the rest; educated bickering is still in process.

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