The single Out-of-Africa theory is dying

A new paper shows that it is likely that modern humans had left Africa by at least 177,000 years ago. The single Out-of-Africa theory is dying if not completely dead. Certainly some of the earlier excursions out of Africa may not have survived. I am still sticking to my narrative of the peopling of the world being mainly due to (at least) two waves of expansion from AfricArabia; one before the Toba eruption (74,000 years ago) and one after.

Hershkovitz et al, The Earliest Modern Humans outside Africa, Science  26 Jan 2018: Vol. 359, Issue 6374, pp. 456-459, DOI: 10.1126/science.aap8369

Abstract: Recent paleoanthropological studies have suggested that modern humans migrated from Africa as early as the beginning of the Late Pleistocene, 120,000 years ago. Hershkovitz et al.now suggest that early modern humans were already present outside of Africa more than 55,000 years earlier (see the Perspective by Stringer and Galway-Witham). During excavations of sediments at Mount Carmel, Israel, they found a fossil of a mouth part, a left hemimaxilla, with almost complete dentition.

The sediments contain a series of well-defined hearths and a rich stone-based industry, as well as abundant animal remains. Analysis of the human remains, and dating of the site and the fossil itself, indicate a likely age of at least 177,000 years for the fossil—making it the oldest member of the Homo sapiens clade found outside Africa.

Dinekes summarises this succinctly on his blog.

The sensational discovery of modern humans in the Levant 177-194 thousand years ago should cause a rethink of the currently held Out-of-Africa orthodoxy.

By Out-of-Africa, I mean here the origin of anatomically modern humans, as opposed to the earlier origin of the genus Homo or the later origin of behaviorally fully modern humans.

Two main pieces of evidence supported the conventional OOA theory:

1. The observation that modern Eurasians possess a subset of the genetic variation of modern Africans.
2. The greater antiquity of AMH humans in the African rather than the Eurasian palaeoanthropological record.

Both these observations are in crisis.

1a. The oldest African fossil AMH is in North Africa (Morocco, Jebel Irhoud); modern genetic variation does not single out this region as a potential source of modern humans. In short, modern genetic variation has nothing to say about where AMH originated.
1b. Eurasians can no longer be seen as a subset of Africans, given that they possess genetic variation from Denisovans, a layer of ancestry earlier than all extant AMH. While it is still true that most Eurasian genetic material is a subset of that of modern Africans, it is also true that the deepest known lineage of humans is the Denisovan-Sima de los huesos, with no evidence for any deeper African lineage. Within humans as a whole, Africans possess a subset of Eurasian genetic variation.
2a. African priority received a boost by 0.1My by the redating of Jebel Irhoud last year. And, non-African AMH received a boost of 0.05My by the Hershkovitz et al. paper yesterday. A very short time ago, Ethiopia boasted the oldest AMH by 0.07My and now it’s tied with the Levant and beaten by Morocco. It’s a bit silly to argue for temporal priority based on the spotty and ever-shifting palaeoanthropological record.
2b. It is virtually untenable to consider the ~120,000 year old Shkul/Qafzeh hominins as a failed Out-of-Africa, since it now seems that they may have been descendants from the Mislya Cave population of >50,000 or even >100,000 years earlier.


 

Out of Africarabia


 

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About ktwop

Scientist, technologist, salesman, manager, executive and now a consultant and author.
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4 Responses to The single Out-of-Africa theory is dying

  1. James Cross says:

    I’m starting to be persuaded by this but this is where I am having a problem.

    “By Out-of-Africa, I mean here the origin of anatomically modern humans, as opposed to the earlier origin of the genus Homo or the later origin of behaviorally fully modern humans.”

    I can see there is plenty of growing evidence for anatomically modern humans out of Africa much earlier than previously believed. But then what about the behaviorally fully modern humans. How did all of the anatomically modern humans eventually become behaviorally modern?

    Some possibilities:

    1- Anatomically modern really means that these humans were not quite the same as modern humans even though from gross anatomical features they may look the same. In other words there is a genetic differences and possibly cognitive capability differences that is not apparent in the skeletons. So the real modern humans left Africa later and mostly displaced the earlier humans, although there may have been some genetic mixing between them.
    2- Anatomically modern humans evolved everywhere in parallel and independently to be become behaviorally modern.
    3- There was really a high amount of genetic mixing between humans in and out of Africa so that a parallel evolution occurred.
    4- The difference between earlier anatomically modern humans and behaviorally modern humans is mostly cultural and independent of genetics.

    Any thoughts?

    • ktwop says:

      I am inclined to think that there were a number of AMH movements out of Africa/Arabia (AMH1, AMH2 …..). They certainly mixed genes with Neanderthals and Denisovans whose ancestors had left Africa long before. I suspect there was also mixing and back-mixing between the different AMH “races” themselves. I find it difficult to believe that all the differences between peoples today (“races” or ethnic groups) is the result ofjust 10,000 years of evolution (less than 500 generations). Even if the genetic differences are small they must have taken place over -say – 2 or 3 thousand generations. Certainly the differences we see today must be due to some level of “parallel” development (including genetic)largely isolated from each other.
      So perhaps a combination of your options 1. and 4.

      • James Cross says:

        I’m inclined to agree with you. Oddly number 4 didn’t really occur to me before I put together this list. We don’t really know if even the early departures from Africa had fully modern behavioral capacities but just lacked the culture for fully modern behavior. In that case the differences for current ethnic groups may originate from branches going back later than most believe and modern behavioral humans arose primarily through cultural diffusion with only minor genetic mixing.

  2. ptolemy2 says:

    I would defend the ancestral primacy of the 60kya breakout since, while it was indeed one of many “exodi” from Africa, the genetic evidence is strong that most (not all) human descent outside Africa is from that event.

    Modern human remains predating the 60kya breakout are old news – ones in India, China and around Israel and the Levant have been in the literature for a decade. They are periodically re-reported as new findings, as now.

    Indeed starting with the appearance of H sapiens about 200,000 years ago, there were periodic break-outs from Africa. The claims about the 60 kya breakout are not that this was the only breakout. This is a common misunderstanding or oversight. No – the claim – backed up by genetic evidence, is that it was this 60 kya breakout, the first to happen after humans became behaviourally modern about 70 kya, was the one to which nearly all humans outside Africa today trace their descent. This is shown for instance by the mitochondrial haplotype L3 labellling of this migrating group. Some groups exiting Africa left desendants. Others did not – or left only a small trace of their genes.

    Just to be clear – the fact there were numerous “exodi” from Africa both before and after the 60 kya event, does not alter or contradict the clear evidence from genetics, from both maternal mitochondrial and male Y-chromosome analysis, that most humans today are indeed descended from that single 60 kya breakout. As Richard Dawkins showed mathematically in “The Ancestor’s Tale”, prior to 20,000 years ago, everyone alive was ancestor either to everyone living today, or to no-one.

    It has been known for years that H sapiens exited Africa as long ago as 200, 000 years, with the well known discoveries in India, China and the Levant (endlessly re-reported as new findings). We are told that this discovery at Misliya cave in Israel dated to 177,000-194,000 years ago, changes everything in human origin research. It changes nothing and is not even new. Reconstruction of human history is not about choosing between palaeontology or genetics. It’s both together.

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