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Thread: Very early human presence in Alaska?

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    Very early human presence in Alaska?


    "Genetic evidence unambiguously shows that the first peoples of the Americas were descended from a group of people who were themselves descended from East Asians and ancient North Eurasians before becoming isolated from gene flow for a period of time beginning around 23,000-20,000 years ago.Noting that this period coincided with a period of global cooling and desertification called the Last Glacial Maximum (LGM), many geneticists have inferred that this isolation took place in Beringia. At the time, that was a landmass extending from eastern Siberia through Alaska. This inference has been strengthened by paleoecological data showing that “refugia” in Beringia were warmer and more hospitable to life than most of southern Siberia. Limited contact between groups in different refugia could possibly explain the genetic structure seen in the genomes of their descendants.
    Archaeological evidence for this model is limited. "

    "The "swift peopling" model does not satisfy most geneticists (and some archaeologists) who note that geographically and ecologically Beringia is a far more plausible region for population isolation than Asia. They continue to argue that there must have been an early human presence in central or eastern Beringia—we just haven’t found it yet."

    "A new study ("Evidence of Ice Age humans in eastern Beringia suggests early migration to North America") just published in the journal Quaternary Science Reviews may help to bring the genetic and archaeological records more in synch. Richard Vachula and colleagues analyzed sediment cores taken from Lake E5 in the Brooks Range on the North Slope of Alaska. Because this lake wasn’t glaciated during the LGM, its sediments are a record of environmental conditions during that time."

    "The authors found two results significant to understanding the peopling of the Americas. First, they found an increase in charcoal particles in sediments dating to between 32,000-19,000 relative to previous and later time periods. These charcoal particles would have been deposited by fires burning within a few kilometers of the lake. While the authors can’t distinguish between fires set naturally by lightning and those set deliberately, the historically low amounts of lightning in this region and the resistance of steppe vegetation to burning suggest artificial fires."

    "Vachula and colleagues identified fecal stanol profiles consistent with the periodic presence of humans in the vicinity of the lake from about 31,000-22,000 years ago. After 18,000 years ago, which happens to coincide with greater archaeological visibility of human occupation throughout Alaska, the biomarkers indicate a consistent presence of humans in the region.Coupled with the evidence for increased burning, this is very strong circumstantial evidence for an early human presence in eastern Beringia from 32,000 years ago throughout the LGM. If the Beringian Isolation model is correct, I suspect that we will be finding much more evidence like this in the near future."

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    In the recently released American aDNA & modern data paper the authors suggested they had found evidences for an early split between Paleo-Beringians and Paleo-Amerindians, but also, more intriguingly even, that they had find autosomal evidences for a 3rd lineage related to both in the Mixe people of Mexico, however one which would have split from the two even earlier, roughly 30-22 kya. Maybe that finding is somehow related to this paper's results about at least occasional human settlement earlier than previously thought? Alternatively, maybe an earlier Beringian population before the ~24kya Beringian-Amerindian main lineage that separated from other Paleo-Siberians could account for the mysterious presence of Australasian-like admixture in Aleutians and some Amazonians (not found in any American aDNA yet), heavily diluted and dispersed by the latter peopling of the Beringians during the height of the LGM, who became much more numerous and densely distributed in Beringia, thus "spilling over" to America (as the scientists claim that from 18 kya the signs of human settlement become consistent, not just periodic).

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