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Thread: Did Our Species Evolve in Subdivided Populations across Africa, & Why Does It Matter?

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    4 out of 4 members found this post helpful.

    Did Our Species Evolve in Subdivided Populations across Africa, & Why Does It Matter?

    Highlights


    The view that Homo sapiens evolved from a single region/population within Africa has been given primacy in studies of human evolution.

    However, developments across multiple fields show that relevant data are no longer consistent with this view.

    We argue instead that Homo sapiens evolved within a set of interlinked groups living across Africa, whose connectivity changed through time.

    Genetic models therefore need to incorporate a more complex view of ancient migration and divergence in Africa.

    We summarize this new framework emphasizing population structure, outline how this changes our understanding of human evolution, and identify new research directions.

    We challenge the view that our species, Homo sapiens, evolved within a single population and/or region of Africa. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. Similarly, the African archaeological record demonstrates the polycentric origin and persistence of regionally distinct Pleistocene material culture in a variety of paleoecological settings. Genetic studies also indicate that present-day population structure within Africa extends to deep times, paralleling a paleoenvironmental record of shifting and fractured habitable zones. We argue that these fields support an emerging view of a highly structured African prehistory that should be considered in human evolutionary inferences, prompting new interpretations, questions, and interdisciplinary research directions.

    https://www.cell.com/trends/ecology-...showall%3Dtrue




    Our fractured African roots

    While it is widely accepted that our species originated in Africa, less attention has been paid to how we evolved within the continent. Many had assumed that early human ancestors originated as a single, relatively large ancestral population, and exchanged genes and technologies like stone tools in a more or less random fashion.

    In a paper published in Trends in Ecology and Evolution this week, this view is challenged, not only by the usual study of bones (anthropology), stones (archaeology) and genes (population genomics), but also by new and more detailed reconstructions of Africa’s climates and habitats over the last 300,000 years.

    One species, many origins

    “Stone tools and other artifacts – usually referred to as material culture – have remarkably clustered distributions in space and through time,” said Dr. Eleanor Scerri, researcher at the Max Planck Institute for the Science of Human History and the University of Oxford, and lead author of the study. “While there is a continental-wide trend towards more sophisticated material culture, this ‘modernization’ clearly doesn’t originate in one region or occur at one time period.”

    Human fossils tell a similar story. “When we look at the morphology of human bones over the last 300,000 years, we see a complex mix of archaic and modern features in different places and at different times,” said Prof. Chris Stringer, researcher at the London Natural History Museum and co-author on the study. “As with the material culture, we do see a continental-wide trend towards the modern human form, but different modern features appear in different places at different times, and some archaic features are present until remarkably recently.”

    The genes concur. “It is difficult to reconcile the genetic patterns we see in living Africans, and in the DNA extracted from the bones of Africans who lived over the last 10,000 years, with there being one ancestral human population,” said Prof. Mark Thomas, geneticist at University College London and co-author on the study. “We see indications of reduced connectivity very deep in the past, some very old genetic lineages, and levels of overall diversity that a single population would struggle to maintain.”

    An ecological, biological and cultural patchwork

    To understand why human populations were so subdivided, and how these divisions changed through time, the researchers looked at the past climates and environments of Africa, which give a picture of shifting and often isolated habitable zones. Many of the most inhospitable regions in Africa today, such as the Sahara, were once wet and green, with interwoven networks of lakes and rivers, and abundant wildlife. Similarly, some tropical regions that are humid and green today were once arid. These shifting environments drove subdivisions within animal communities and numerous sub-Saharan species exhibit similar phylogenetic patterns in their distribution

    The shifting nature of these habitable zones means that human populations would have gone through many cycles of isolation – leading to local adaptation and the development of unique material culture and biological makeup – followed by genetic and cultural mixing.

    “Convergent evidence from these different fields stresses the importance of considering population structure in our models of human evolution,” says co-author Dr. Lounes Chikhi of the CNRS in Toulouse and Instituto Gulbenkian de Ciência in Lisbon.“This complex history of population subdivision should thus lead us to question current models of ancient population size changes, and perhaps re-interpret some of the old bottlenecks as changes in connectivity,” he added.

    “The evolution of human populations in Africa was multi-regional. Our ancestry was multi-ethnic. And the evolution of our material culture was, well, multi-cultural,” said Dr Scerri. “We need to look at all regions of Africa to understand human evolution.”

    http://www.shh.mpg.de/1007846/human-evolution

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    1 out of 1 members found this post helpful.
    If that is really true (as it looks increasingly plausible according to the latest scientific evidences), then I still wonder and think that surely a huge process of genetic mixing and homogeneization of intra-African population structures, with absorption of the more archaic lineages by one or a few dominant ones (akin to what happened in Eurasia later), must've happened pretty early, well before the colonization of Eurasia & Oceania. Otherwise I think we should expect non-Africans to be much more distant from even the more anciently diverged populations of Africa, like Mbuti and Khoisan. I think a multiregional origin - though not in the sense the proponents of that theory originally imagined, which was multicontinental and not just within several Afrian regions - is likely, but with so many events of almost wholesale population replacement in the distant past of humankind I think it's still likely that the bulk of the present-day humankind derives from just a few related populations that had perhaps absorbed only minor proportions of ancestry from more archaic Sapiens populations, thus causing the ghost population phenomena that have been found in the genetic analyses of African individuals, and the relatively high degree of genetic homogeneity of the humankind.

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    Quote Originally Posted by Ygorcs View Post
    If that is really true (as it looks increasingly plausible according to the latest scientific evidences), then I still wonder and think that surely a huge process of genetic mixing and homogeneization of intra-African population structures, with absorption of the more archaic lineages by one or a few dominant ones (akin to what happened in Eurasia later), must've happened pretty early, well before the colonization of Eurasia & Oceania. Otherwise I think we should expect non-Africans to be much more distant from even the more anciently diverged populations of Africa, like Mbuti and Khoisan. I think a multiregional origin - though not in the sense the proponents of that theory originally imagined, which was multicontinental and not just within several Afrian regions - is likely, but with so many events of almost wholesale population replacement in the distant past of humankind I think it's still likely that the bulk of the present-day humankind derives from just a few related populations that had perhaps absorbed only minor proportions of ancestry from more archaic Sapiens populations, thus causing the ghost population phenomena that have been found in the genetic analyses of African individuals, and the relatively high degree of genetic homogeneity of the humankind.
    I'm interested to see if David Reich will expand upon this topic in the next edition of his book.

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    1 out of 1 members found this post helpful.
    Quote Originally Posted by Jovialis View Post
    I'm interested to see if David Reich will expand upon this topic in the next edition of his book.
    in his latest book he hints at modern humans being a mixture of 2 species
    but afaik no further DNA studies about this topic have been published

    it would be great if we could have DNA from the Irhoud or Skhul/Qafzeh hominids

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    Razib Khan has made an article on this topic:

    https://www.gnxp.com/WordPress/2018/...i-regionalism/

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    1 out of 1 members found this post helpful.

    African multiregionalism

    Not Adam and Eve... but Adams and Eves.

    https://www.cell.com/trends/ecology-...347(18)30117-4

    "The view that Homo sapiens evolved from a single region/population within Africa has been given primacy in studies of human evolution.
    However, developments across multiple fields show that relevant data are no longer consistent with this view.
    We argue instead that Homo sapiens evolved within a set of interlinked groups living across Africa, whose connectivity changed through time.
    Genetic models therefore need to incorporate a more complex view of ancient migration and divergence in Africa.
    We summarize this new framework emphasizing population structure, outline how this changes our understanding of human evolution, and identify new research directions.
    We challenge the view that our species, Homo sapiens, evolved within a single population and/or region of Africa. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. Similarly, the African archaeological record demonstrates the polycentric origin and persistence of regionally distinct Pleistocene material culture in a variety of paleoecological settings. Genetic studies also indicate that present-day population structure within Africa extends to deep times, paralleling a paleoenvironmental record of shifting and fractured habitable zones. We argue that these fields support an emerging view of a highly structured African prehistory that should be considered in human evolutionary inferences, prompting new interpretations, questions, and interdisciplinary research directions."
    It is therefore worth while to search out the bounds between opinion and knowledge; and examine by what measures, in things whereof we have no certain knowledge, we ought to regulate our assent and moderate our persuasion. (John Locke)

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    There's another thread on this topic:

    https://www.eupedia.com/forum/thread...Does-It-Matter

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    Quote Originally Posted by Jovialis View Post
    There's another thread on this topic:

    https://www.eupedia.com/forum/thread...Does-It-Matter
    Ooops... I wasn't aware of that. Thanks for the link.

    Just delete the current thread. No need for two of them.

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    Quote Originally Posted by hrvclv View Post
    Ooops... I wasn't aware of that. Thanks for the link.

    Just delete the current thread. No need for two of them.
    Don't worry, I'll just merge them.

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    While on this topic, I thought what Razib Khan suggested was interesting, in relation to the recent revelation of the Dzudzuana cave samples:

    The big picture needs to be integrated I think with the new “modern humans emerged through a multi-regional process” within Africa. If you think of modern humans as emerging across an African range which shifted in the Near East based on oscillating climatic conditions, the ancestors of the “non-African” lineages can be thought of as one of the main deeply rooted lineages, probably in the northeast of the continent. During the Pleistocene, the Sahara was even more brutal than today during many periods, so it is not implausible that some of these marginal populations on the edge of Africa were subject to long periods of very small effective population sizes. Most of them presumably went extinct. But one population was probably far enough north and east that it had a little more margin to play with. This population was probably connected along the Mediterranean littoral at some point with the Deep component in North Africa, which had higher effective population sizes because the mountainous terrain of the Atlas region was always going to remain more clement through dry phases.

    https://www.gnxp.com/WordPress/2018/09/23/tracing-the-paths-of-noahs-sons/

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    2 out of 2 members found this post helpful.
    Quote Originally Posted by Jovialis View Post
    While on this topic, I thought what Razib Khan suggested was interesting, in relation to the recent revelation of the Dzudzuana cave samples:
    check the Irhoud skulls and the Aterian culture
    you'll find that the Atlas Mountains and the Central Sahara were dominated by it till 30 ka, the onset of LGM
    and there is no indication whatsoever that this population had any interaction with the modern humans from which we all descend
    Iberomaurisian spread ca 24 ka, after those Aterians went extinct and the whole Sahara was deserted, even in the Atlas Mountains, there is no overlap between Aterian and Iberomaurisian

    the same goes for the Skhull-Qafzeh in the Levant, who were morpholigical similar to Irhoud and Aterians
    they went extinct ca 90 ka, and after them the Levant seems to have been unhabitated till the Neanderthals came in 65-60 ka

    I'm sorry, but it seems to me that Razib Khan, in his latest posts did not do the proper homework

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    Quote Originally Posted by bicicleur View Post
    check the Irhoud skulls and the Aterian culture
    you'll find that the Atlas Mountains and the Central Sahara were dominated by it till 30 ka, the onset of LGM
    and there is no indication whatsoever that this population had any interaction with the modern humans from which we all descend
    Iberomaurisian spread ca 24 ka, after those Aterians went extinct and the whole Sahara was deserted, even in the Atlas Mountains, there is no overlap between Aterian and Iberomaurisian

    the same goes for the Skhull-Qafzeh in the Levant, who were morpholigical similar to Irhoud and Aterians
    they went extinct ca 90 ka, and after them the Levant seems to have been unhabitated till the Neanderthals came in 65-60 ka

    I'm sorry, but it seems to me that Razib Khan, in his latest posts did not do the proper homework
    Not to mention that Eurasian macrogroup CT is dated to only 86000 BC. If Qafzeh & Skhul were the ancestors of Eurasian that would almost require a backmigration of macrogroup BT into Africa from the Levant.

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