The Road From Morocco

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It never hurts to look at the map. Back around the glacial maximum, the world was a crappy place, with fewer inhabitable areas. Some of the high genetic differentiation in early Holocene populations may have been caused by climate-induced barriers: glaciers, bigger deserts, glacial lakes, etc.

The Basal Eurasians had low Neanderthal admixture while still leaving sub-Saharan Africa. North Africa might fit this scenario. If they made it to North Africa when conditions were not so bad, they might have been trapped there for a long time when the Sahara was at its max, and would only have entered the Middle East after the Neanderthals had already been displaced. But this means that they probably ran into and admixed with the locals, either not AMH or some fairly divergent branch of AMH.

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29 Responses to The Road From Morocco

  1. Frank says:

    “But this means that they probably ran into and admixed when the locals, either not AMH or some fairly divergent branch of AMH.”

    Not sure I am understanding.

  2. Frank says:

    Unless all if the AMH population in North Africa had already admixed with and/or eliminated other groups from North Africa before some of them moved out in the Out-Of-Africa (Neanderthal admixing) event.

    In that case, the Basal Eurasians could have been all alone for a long time up there.

  3. le homme de pomme says:

    Is there a good review paper on human ancestry (<100 pages, but with a good amount of detail and written for a scientifically literate audience)?

  4. dearieme says:

    That map looks awfully like current Africa: were the coastlines so little different when the sea level was much lower?

  5. JayMan says:

    “It never hurts to look at the map”

    I mean, seriously.

  6. ohwilleke says:

    Great map! What is the source?

  7. Karl Zimmerman says:

    The ice age maps also make it clear why the Altai was inhabited by Ancient North Eurasians of West Eurasian ancestry, rather than East Eurasia – that there was a solid band of uninhabitable desert (either polar or temperate) running from the Himalayas all the way to the Arctic Circle. The Altai region was basically as far east as the “European” steppe-tundra extended in the worst climactic periods.

    Regardless, during the LGM, did the Ethiopian highlands and East Africa dry out so much that the Nile didn’t reach the Mediterranean? If not, I’d have a hard time believing there wouldn’t be at least some genetic exchange between Africa and the Levant through the ice ages – even if the Maghreb missed out entirely.

  8. BB753 says:

    So, did some Basal Eurasians eventually wander South to become the Bantu, admixing with the archaic locals in the process?

  9. Flinders Petrie says:

    Southern Arabia also works. There were definitely Acheulean hominids there, and a subsequent wave of AMHs crossing the Bab al Mandab could have admixed with the descendants of these earlier folks. They were confined to refugia, with the empty quarter forming a massive barrier.

    Climate data also fit this scenario. Increased precipitation at 100 kya in both the Levant and southern Arabia made human expansion into these regions possible. Then, by 75-50 kya, southern Arabia dried up, while the Levant remained humid, which may have pulled people north.

  10. Frank says:

    What makes anyone think that the Basal Eurasians had admixture from any divergent branches of human?

    I don’t think that any mysterious archaic components are detected in modern Europeans (with Basal Eurasian) when compared to East Asians (without).

    • gcochran9 says:

      If they moved from sub-Saharan Africa to somewhere without any Neanderthals, it still had to be habitable, and if it was habitable, some hominid population already lived there. In such encounters, there is often admixture: usually, apparently, judging from evidence of admixture between almost all Eurasians and Neanderthals, ancient AMH and Altai Neanderthals, Asians and Denisovans, Neanderthals and Denisovans, Denisovans and some unknown and very old, divergent group, Pygmies/Bushmen and another very divergent population.

      • Frank says:

        I agree, and maybe they did interact with archaic there, it is just that we can actually see evidence of admixture from a ghost archaic population in Pygmies, but I haven’t seen evidence of that in Europeans.

        Maybe it is true.

        In fact, when the first hints that Basal Eurasian existed in EEF came out, I asked several of the authors if the Basals had any less Neanderthal admixture. They all said that it did not appear to be the case, because there was no change in Neanderthal levels between EEF and modern Europeans.

        Of course now we know that is because the Yamnaya had a similar level of Basal Eurasian from their CHG ancestry, so it was a wash.

        The higher level of Neanderthal in East Asians was then postulated to be additional admixture. This also is probably wrong, as is the decrease in Neanderthal due to simple selection.

        So maybe we will actually find something here.

        • gcochran9 says:

          The decrease in Neanderthal is concentrated in coding regions, I think. It’s hard to imagine a population history that would have that result.

          • Frank says:

            It actually is exactly the same.

            If Basal Eurasian coding regions had less deletious mutations, due to a much larger effective population history over a shorter amount of time, then these regions would be under positive selection in admixed populations.

  11. Karl Zimmerman says:

    Thinking about it more, there have been a lot of papers in the last 5-10 years which have looked at Berber genetics. I believe the most recent conclusion was Berbers are (discounting recent minor admixture from SSA and Europeans) a compound of a Near Eastern neolithic population and some sort of indigenous non-SSA hunter-gatherer population.

    My quantitative skills are weak to say the least, but I’d guess the commenters on Eurogenes could easily see if Basal Eurasian (or at least a Basal Eurasian heavy ancient population) was enriched in Berbers when compared to other West Eurasians. If it is, then it is likely the Moroccan refugium was the home of the Basal Eurasians. If not, it’s more likely South Arabia, or maybe the now flooded Persian Gulf region, was the home for the Basal Eurasian population.

    • Frank says:

      Barbers really look like a population that arrived in North Africa <15,000 years ago.

      We need genomes from much further back than this.”Give Davidksi time enough and he will torture the data enough to make it all go way”

      • Frank says:

        That was a funny accidental addition.

      • Karl Zimmerman says:

        Whether the bulk of the Berber ancestry arrived in the period just before the neolithic or afterward, there should have been an indigenous population in the Maghreb, which presumably admixed into the Berbers on at least a minor level. If Greg’s hypothesis is correct, this group should have been Basal Eurasian (or a population very closely related).

        That said, it is interesting to bring up ancient DNA here. The Atlas mountains are cold and dry enough there should be fairly good preservation, so I wouldn’t be surprised if someone does find some Mesolithic remains from Morocco within the next 5-10 years. Certainly more likely than in much of Africa.

  12. chrisdavies09 says:

    ‘Basal Eurasian’ in Europeans peaks in Sardinians. Sardinians also have very high levels of North African HLA haplotypes.

    For example:-
    https://en.wikipedia.org/wiki/A30-Cw5-B18-DR3-DQ2_(HLA_Haplotype)

  13. sprfls says:

    What makes you favor North Africa over the Gulf? In the new first farmers paper Neolithic Iranians surprisingly have even more Basal than Natufians. So if they expanded east out of North Africa this needs to be explained. (Of course, it’s possible that similar populations existed in both locations, and, to be fair, there isn’t any North African aDNA yet.)

    I’ll skip over some archeological evidence and just point out what I mentioned before: mtDNA R0. It looks like it could be a Basal marker: splitting off from Africans a long time ago, sitting in isolation, and then expanding starting ~20K years ago. R0a is most diversified and has the highest frequencies in southern Arabia. It peaks in the island of Socotra. I’m even thinking Socotra might be to Basal what Sardinia is to the Neolithic Anatolians…

  14. Steve Sailer says:

    Famous unplanned blooper in “Road to Morocco:”

  15. RK says:

    Its quite unlikely that Basal Eurasians were in North Africa. More likely that whatever admixed into Natufians, causing them to be further away from all Eurasians (including Basal Eurasian-containing populations, than Eurasians are to each other) while being no closer to Africans, lived there.

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