May 20, 2011

Is Jebel Irhoud the Father of mankind?

The redating of the human Y-chromosome phylogeny to about 142 thousand years ago and the relocation of its most ancient lineages from east and south Africa to the Northwest marks a watershed moment in our understanding of human prehistory.

It is a fortuitous coincidence that there actually is a sample of humans from Northwest Africa from around the same time: Jebel Irhoud, about 160 thousand years ago from Morocco:
Jebel Irhoud is a cave site located about 100 km west of Marrakech, Morocco. The site is known for the numerous hominid fossils discovered there. Currently, the site has yielded seven specimens. The best known of these are portions of two adult skulls, Irhoud 1 and 2, a child’s mandible (Irhoud 3), and a child’s humerus (Irhoud 4). Fossils 1-3 were discovered while the cave was being quarried for barytes and thus their exact context and age has been subject to debate. Originally the Irhoud hominids were considered North African Neandertals. It is now clear that they are best grouped with other early anatomically modern humans such as Qafzeh (Israel) and Skhul (Israel).

A 2007 article by Smith et al. is extremely important for this population:
Earliest evidence of modern human life history in North African early Homo sapiens

Tanya M. Smith et al.

Recent developmental studies demonstrate that early fossil hominins possessed shorter growth periods than living humans, implying disparate life histories. Analyses of incremental features in teeth provide an accurate means of assessing the age at death of developing dentitions, facilitating direct comparisons with fossil and modern humans. It is currently unknown when and where the prolonged modern human developmental condition originated. Here, an application of x-ray synchrotron microtomography reveals that an early Homo sapiens juvenile from Morocco dated at 160,000 years before present displays an equivalent degree of tooth development to modern European children at the same age. Crown formation times in the juvenile's macrodont dentition are higher than modern human mean values, whereas root development is accelerated relative to modern humans but is less than living apes and some fossil hominins. The juvenile from Jebel Irhoud is currently the oldest-known member of Homo with a developmental pattern (degree of eruption, developmental stage, and crown formation time) that is more similar to modern H. sapiens than to earlier members of Homo. This study also underscores the continuing importance of North Africa for understanding the origins of human anatomical and behavioral modernity. Corresponding biological and cultural changes may have appeared relatively late in the course of human evolution.
In the recent paper on the Ceprano calvarium, Irhoud 1 clearly belonged in the modern human cluster, and so it was in my re-analysis of that data, as were skulls from the Sudan and Tanzania in Africa, and the Qafzeh/Skhul early skulls from the Levant.

It thus seems to me, that the earliest modern human skulls are found in North/East Africa and West Asia, while the root of the Y-chromosome phylogeny is provisionally in Northwest Africa and seems to be in agreement with the autosomal evidence for a bottleneck in the human population at around 150,000 years ago.

Here is the interesting part: Irhoud had been once seen as a Neandertal. Indeed, it displayed some Neandertal-like leanings in a previous analysis. The consensus now (supported by the results of Mounier et al.) seems to be that it was modern human, but the Neandertal connection does not stop there:

The lithic industries of Jebel Irhoud were Mousterian, the same as Neandertals. Mousterian industries link European Neandertals, with modern humans in North Africa and the Near East. The Mousterian industries represented a genuine progress over the Acheulean tools that archaic humans had been using for hundreds of thousands of years before, and they, in turn, were replaced by the Aurignacian at exactly the time that Cruciani et al. date the main Y-chromosome CT clade that encompasses all Eurasians and most Africans.

The evidence seems to be in astonishing agreement with my hypothesis about the so-called "Neandertal admixture" in modern humans:
  • Early modern humans originated in North Africa, or at least somewhere between North and East Africa. Their traces may very well be hidden under the sands of the once (or thrice) green Sahara
  • They formed a clade with Neandertals, and used the same Mousterian tools, while humans elsewhere continued to use the older Acheulean ones. Both of them could very well have descended from Homo heidelbergensis, although the transition is not yet clear.
  • They expanded briefly into West Asia after Marine Isotope Stage 5, 120,000 years or so ago, and appeared in the Levant (Skhul/Qafzeh). As the Sahara dried up, they must've spread both to West Asia, and deeper into Africa, and, not surprisingly, the next major branching of the Y-chromosome phylogeny dates to about that time; this accounts for the deep (but not deepest) Y-chromosome lineages in modern day San.
  • Eventually (around 40,000 years ago, after the end of wet Marine Isotope Stage 3), they developed the even more advanced Aurignacian technology, and went on to conquer most of the world, driving the Neandertals to extinction. As the Sahara dried up, they expanded into Sub-Saharan Africa once again, and this time they inundated it with their genes.
Hence, the Modern-Neandertal affinity is not the result of any hypothetical admixture event between the two: Sub-Saharan Africans have also preserved some of the genetic legacy of the older Acheulean-using populations of the continent which shifts them somewhat away from other modern humans and Neandertals.

The model in brief

195 ka: Anatomically modern humans appear in East Africa (Omo skulls)
160 ka: Mousterian-using modern humans in North Afrca (Jebel Irhoud)
142 ka: Y-chromosome Adam
MIS 5 120-110 ka: Demographic expansion of modern humans in Sahara during this wet phase, followed by collapse as Sahara becomes dry; escape to West Asia and Sub-Saharan Africa; possible admixture with Neandertals and Acheulean-using Palaeoafricans respectively.
MIS 3 50-45 ka: Second demographic expansion of modern humans in Sahara, followed by collapse as Sahara becomes dry; development of Aurignacian
after 45 ka: Colonization of Eurasia and Sub-Saharan Africa by modern humans sensu stricto: anatomically and behaviorally modern people with advanced tools. Most human Y-chromosomes (belonging to C, DE, and F) coalesce to this period.
40 ka: Neandertals extinct after contact with modern humans (absorbed/killed?); some survive in periphery
Today: Most living humans descended from post 45-ka expansion people. Sub-Saharan Africans shift away from Eurasians due to a little archaic African admixture. Papuans shifted away from Eurasians due to "Denisovan" admixture. Contribution of other archaic hominins to regional Homo sapiens populations TBD.

13 comments:

  1. How does the Zhirendong specimen at 100,000 in South China fit in here?

    Its date predates your stage "after 45 ka: Colonization of Eurasia and Sub-Saharan Africa by modern humans sensu stricto: anatomically and behaviorally modern people with advanced tools" by more than 50K years, no?

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  2. I mention it for the sake of completeness. It could very well have been part of the same pulse that gaves us Qafzeh/Shkul, or its modern attributes may have been overestimated.

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  3. It's hard to argue that the modern attributes of a modern chin have been overestimated. And where exactly do you mention Zhirendong?

    Also, with this chronology, modern humans vegetated in Africa for 100,000 years (!) sporting modern morphology but no specialized modern behavior, and then exploded to conquer the world within a couple of thousand of years armed with new UP technologies for which there are no North or West African antecedents. It's just science fiction.

    Finally, there are no language isolates or small families in North Africa. We would expect to find them in places where populations go back to Mid-Pleistocene with its small scale demography. What happened with those? Disappeared for convenience sake?

    On a positive note, West Africa does have some interesting language isolates (Laal, etc.) and small families that could indicate the survivals of Late Pleistocene linguistic variation in Africa.

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  4. So in your opinion do you think the presence of derived Neandertal genes in Eurasians are not so much 'Neandertal' as "archaic African"? That is, if the clever ancient genomic analyses by Green et al. (2010) and Reich et al. (2010) were to include more Africans, namely from the North, they would show these 'Neandertal derived' genes that link Eurasians with Neandertals?

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  5. So in your opinion do you think the presence of derived Neandertal genes in Eurasians are not so much 'Neandertal' as "archaic African

    Rather, "lack of archaic African".
    In reality it could be both.

    were to include more Africans, namely from the North

    I have campaigned for someone to repeat the analysis with east Africans that were neglected in the original paper. North Africans are probably trickier because even though Berbers have doubtlessly absorbed some earlier population elements, they may be, to a great extent derived from outside Africa or at least outside NW Africa.

    I did try a small experiment

    http://dienekes.blogspot.com/2011/03/neandertal-genes-in-east-africa.html

    which showed that Maasai from East Africa shared a "Neandertal" region with East Asians but not Caucasoids. This is inconsistent with Neandertal admixture, as there were no Neandertals in East Africa, as well as with the "Neandertal" alleles being the result of Caucasoid back-migration, as that wouldn't brought back the "Neandertal" genes found in East Asians.

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  6. Dienekes:

    "I did try a small experiment

    http://dienekes.blogspot.com/2011/03/neandertal-genes-in-east-africa.html

    which showed that Maasai from East Africa shared a "Neandertal" region with East Asians but not Caucasoids. This is inconsistent with Neandertal admixture, as there were no Neandertals in East Africa, as well as with the "Neandertal" alleles being the result of Caucasoid back-migration, as that wouldn't brought back the "Neandertal" genes found in East"

    ---

    There maybe a connection between neanders and arians, indo-arians and afro-asiatics - indicating a later migrational movement into E Africa - along the shores of of the Arabian Pennisula. The genetic fabric of the islands of Socotra, where the shells producing purple-dye exist, may indicate a seafaring-culture that originated around the indo-aryans east of the Persian Bay...

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  7. @ Dienekes:

    "MIS 3 50-45 ka: Second demographic expansion of modern humans in Sahara, followed by collapse as Sahara becomes dry; development of Aurignacian after 45 ka: Colonization of Eurasia and Sub-Saharan Africa by modern humans sensu stricto: anatomically and behaviorally modern people with advanced tools. Most human Y-chromosomes (belonging to C, DE, and F) coalesce to this period."

    This time-line rests entierly on the old interpretations of ice-time, which states that we had a long 'glacial period' in Europe, called Wurm/Weichsel, dated to (ca.) 115.000-12.500 yrs BP. The last third of that period is supposed to have been the coldest, initiated by the MIS 4-stadial, starting ca. 50.000 years ago. By 40.000+ years BP the climate grew milder, initiating the inter-glacial warm MIS 3.

    Corresponding to this archaologists have dug out a number of sites from Paleolithic settlements in the northern tiers of Eurasia. Moreover, these settlements are dominated by tools and technology that corresponds to the Mesolithic technologies. Consequently anthropologers of various sorts have concluded that these are the oldest traces of modern humans in Eurasia. Building on theese findings the theories about the origin and migrations of the AMH was adapted to correspond to these dates. For some reason the archaeologists adapted - somewhat uncrtically - to the same model, as they started to differ between "Middle-Weichslian" and "Upper-Weichslian" technology. Today these theoretic terms seems to be bougth uncrtically, as "facts", by geneticians as well as the rest of us.

    A closer look at the tools of NW Europe shows that the named "MIS-transition" is both supported and contradicted. One clearly contradiction is found in the Rhen valley and the Rhen river - where very old populations have been traced. During the milder periods MIS 5 and MIS 3 the settlements are found up in the valley, during the colder MIS 4 and MIS 2, the populations are found in the lower Rheinland, where the river met the ocean.

    Most of the eastern Eurasian populations disappeared during the LGM-periods (23 and 19 kYB). During the Older and Younger Dryas the western groups are also strongly reduced. The estuaries of Lower Rheinland, Holland or France - close to the benefits of the Mexican Gulf stream - may be one of the few places that any Paleolithic Eurasians would survive.

    http://quaternary-science.publiss.net/articles/809?locale=en

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  8. In 1997 a highly arctic population was found in Mamontaya Kurya, at the arctic coast of NW Russia, that was more than 40.000 years old. Bones of mammoth were processed and left here, no less than 34.000 BP. The tools found reminds of both Midddle and Upper paleolithic.

    As the discovery hit the news (Nature 2001) a number of other findings from NW Eurasia revealed that there where a number of settlements that could be dated between 40 and 20 kYr BP. The last Solutreans seem to disapear during the Younger Dryas.

    During the Alleröd-populations they were present in Rhenland and the Danish islands before they disapears for less than 400 years - before they reappear in the Rhone river estuary. Where they found their final refugee we do not know - but genetic bottle-necks tells us they were a very limited group - as the Eurasian icetime came to its end.

    The first people to re-populate the Baltic Sea and the northern tears came to the area of North Cape already 12.400 years ago (Sarnes 2). Their technology is strikingly close to the tools used in Mamontaya Kurja and Byzova, 27.000 years before. The arctically well-adapted people managed to populate the pre-Boreal landscapes of northern Europe and Asia - with an re-start around 12.500 years ago.

    The well-adapted Paleolithics who survived ice-time in the north were not many. But they were obviously very well adapted and developed, as they were able to spread, establish and reproduce - incredibly fast - as soon as ice-age Europe turned into the Boreal climate of today.

    The rapid spread of AMH througout northern Eurasia could never have been achived by Homo sapiens without the physiological adaptions that goes with pale skin and a 7-fold increase in the production of vitamin D - as soon as it is exposed to sunshine. Without this and other physiological adaptions it is impossible to survive the sunless days of the arctic winter.

    The people that populated N-Europe was highly specialized also in the organization of their life, to establish a technology and an industry that could feed them - as well as an economy that made social and cultural relations work - over great distances, througout the vast arctic oceans, seas and stepp-lands.

    Compared to any African of 35-40.000 years ago the difference is 'vast'. One just wonders how anyone can motivate how an indigenous populations from a Sub-Saharan climate - in trandscending into AMH - could take off and move straigth through the high-arctic landscape of the Eurasian tundra - to hunt seals and seabirds at the Barents Sea...?!

    The Mesolithic tools of Northern Scandianvia is divided east and west - in "Ahrensburgian" ('Fosna') and "Swidrian" ('Komsa'). Since Fenno-Scandia doesn't show any later migrations we can still find this East-West divide in the German vs. the Uralian cultures, one east and the other west of the Baltic and the Botnic Oceans - congruent to the differences upheld during the Neolithic and the metal ages. Consequently there should be enough genetic material to determine the genetic fabric nessecary to survive an arctic refugia for 30.000 years - fit and ready to populate the entire arctic circle at 12.500 BP...

    http://repositriodeficheiros.yolasite.com/resources/Texto%2031.pdf

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  9. triple posting is forbidden, any further triple posts will be deleted.

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  10. Duely noted. Please excuse my inconvinience.

    Now what about the "arctic problem" with the "OoA-theory"?

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  11. This is not even science fiction. It is pure fiction. There is no such thing as "adam and eve" even genetically speaking. There are too many inconvenient anomalies for that religious dogma to become the mainstream thinking, no matter how much you religious fanatics continue to promote it. The chinese example is perfect illustration of stupidity of that "adam/eve" delusion. And that of Africa being a cradle of humanity. One little thing no one seems to be considering is that by all accounts and rules the genetics have themselves accepted for the genomes, (mutatins to occure every 7k-10k years) there should NOT be any genes present before the haplotype I. If the mutations are so dramatic that say H turns to I at some point, then why the A is still present in Bantus and Pygmis? 200 000 years are sufficiently long for these two groups to mutate just as their brethren elsewhere, who seems from the genome chart, have been busy turning from blacks into whites, then Asians, then blacks again and so on. Yet Bantus and Pygmis never did. Yeah... THAT's Science!

    Making hypothesis is one thing. A good one. Making theories and then working of them as if they were the ultimate truth is religious nonsense, not a science. "god" doesn't exit, "adam and eve" don't exist. The genetic diversity points at a number of independently developed human species (yes, species. we are part of animal sphere). Who then mixed together just as every other animal species of similar family do in the nature.

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  12. This is not even science fiction. It is pure fiction. There is no such thing as "adam and eve" even genetically speaking. There are too many inconvenient anomalies for that religious dogma to become the mainstream thinking, no matter how much you religious fanatics continue to promote it. The chinese example is perfect illustration of stupidity of that "adam/eve" delusion. And that of Africa being a cradle of humanity. One little thing no one seems to be considering is that by all accounts and rules the genetics have themselves accepted for the genomes, (mutatins to occure every 7k-10k years) there should NOT be any genes present before the haplotype I. If the mutations are so dramatic that say H turns to I at some point, then why the A is still present in Bantus and Pygmis? 200 000 years are sufficiently long for these two groups to mutate just as their brethren elsewhere, who seems from the genome chart, have been busy turning from blacks into whites, then Asians, then blacks again and so on. Yet Bantus and Pygmis never did. Yeah... THAT's Science!

    Making hypothesis is one thing. A good one. Making theories and then working of them as if they were the ultimate truth is religious nonsense, not a science. "god" doesn't exit, "adam and eve" don't exist. The genetic diversity points at a number of independently developed human species (yes, species. we are part of animal sphere). Who then mixed together just as every other animal species of similar family do in the nature.

    ReplyDelete

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