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Humans in the Americas 130,000 years ago?

  1. Apr 27, 2017 #1

    mfb

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    There has been a lot of discussion about the time when humans first arrived in the Americas, and also which way they took.
    15,000 years ago? 20,000 years ago? 40,000 years ago, and with more immigration waves later?
    Along the coasts? Through the interior? Or even via the open Pacific?

    https://www.nature.com/nature/journal/v544/n7651/full/nature22065.html [Broken], published in Nature, offers a completely new time frame. The authors found evidence for human activities in California 130,000 years ago:
    • Mammoth bones that have been broken shortly after the animal died, probably with stone tools. The bones could be dated: 130.7 ± 9.4 thousand years old.
    • Stones that seem to belong to hammer and anvil combinations, with signs of use.
    No human bones were found, so the evidence relies on the interpretation of the tool marks on the bones and the stones found. If it can be confirmed, it means humans arrived in the Americas way earlier than previously thought.

    Even if humans were there 130,000 years ago, it does not imply they have been there all the time, or in large numbers. There are many remains from the last 15,000 years, but just one discovery that points to a much older human presence. Either they disappeared again, or at least they had a small population, otherwise we would have found many remains by now.
     
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Apr 27, 2017 #2

    jim mcnamara

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    I read the abstract and multiple critical essays.

    The researchers analyzed fragmented mammoth bones, with radial fragmentation, the kind made by being struck by a rock or a tool. Humans routinely do this. So do bulldozers
    .
    The critics point to the fact that a bulldozer unearthed the bones when working on part of a highway project. The critics claim the fractures are from the bulldozer, not early man. The skeletal remains date to 130kya. Nobody disputes that part AFAIK.

    I cannot tell really who is right or wrong. But I do know:
    When you make unusual claims you need unusually good evidence.
     
  4. Apr 27, 2017 #3
    I tend to be skeptical of arguments from absence.
     
  5. Apr 27, 2017 #4
    I would have thought it was easy to distinguish between damage which occurred very recently and damage which occurred thousands of years ago.
    Recent damage would be rougher in texture and more clear, older damage eroded somewhat and less clear.
    Possible there would be signs of some internal material only recently having been exposed to air.
     
  6. Apr 27, 2017 #5

    Fervent Freyja

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    This is too far fetched for me. If we go by a principle of least astonishment, then it is more likely a site that California Sea Otters had been using for a generation or so to make and gather tools from a dead mastodon. They not only heavily populated the Pacific coast and this same area and same time frame, but are already known to use rocks and make tools from bones. We should expect to find sites like this. This would be the most plausible explanation. At least until there is more evidence to fill this enormous time gap. If true, then there should not be a problem gathering evidence to cover that period of 100,000 years. Genetic study of sea otters suggests very long history of tool use
     
  7. Apr 28, 2017 #6

    mfb

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    The study authors claim to cover that. I'm not an expert, so I can just see what the experts say:
    I'm not sure if otters would surprise me less - or more.
     
  8. Apr 28, 2017 #7

    BillTre

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    In heard a report about this on the radio or in a podcast recently.
    The arguments against it were:
    1) There were not cut marks on the bones which would be left from removing the meat from the dead animal. This is kind of normal when butchered (by early humans) animals are found. The proponents argument is that this was bone breaking to remove marrow (maybe the animals were long dead and the meat was already scavenged).
    2) The bones had crush marks from being hit with rocks and there were some unusual(?) round rocks found there. it possible the dead (or maybe alive) animals were there and get caught in a landslide containing the round rocks which caused the damage to the bones.

    #2 seems a feasible explanation to me, but more particulars from the case would be really helpful.
    It might seem an unlikely occurrence, but then it also seems unlikely to some people that humans were in that area back then.
    1) Were all the big bones in the animals crushed but not the little ones?
    2) How unusual were the round rocks found there?
    3) Was there a big hill (or maybe a rapid flowing river) nearby at the time?
     
  9. May 3, 2017 #8

    mheslep

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    What ratio of artifacts would one expect to be discovered that are nearly ten times as old, and therefore to be found deeper, with more dispersal due to weathering and geologic action (including ice ages). Also add in the bias of those doing the digging, most of whom must be thinking Clovis, Clovis, Clovis.
     
  10. May 3, 2017 #9

    mfb

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    If the population would have been similar the whole time, I would expect a relatively smooth distribution that drops slower than exponentially. Certainly not a lot of recent samples, then 100,000 years of nothing and then one very old sample. Possible: sure. Likely? I don't think.
     
  11. May 3, 2017 #10
    Sea Otters are marine mammals, and while rarely seen on shore, are very clumsy there. Their tool use is typically limited to trying to crack open food, and their food is derived from the ocean, so it seems highly unlikely that they would retrieve stones or bones from land to use in the water. The principle of least astonishment would instead lead us to consider other mastodons. These are far more likely as they were terrestrial, endemic to the area and time in question (we have the bones of one there, after all) - and of enormous size - enough mass to break bones. Their close relatives, the elephants, are known to use their trunks to pick up and even throw objects, and are also well known to be very curious about and to manipulate the bones of deceased members of their own species.
     
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