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I found https://www.science.org/doi/10.1126/sciadv.aat5473

Some recent academic and popular literature implies that the problem of the colonization of the Americas has been largely resolved in favor of one specific model: a Pacific coastal migration

These data are largely consistent with either an inland (ice-free corridor) or Pacific coastal routes (or both), but neither can be rejected at present. Systematic archeological and paleoecological investigations, informed by geomorphology, are required to test each hypothesis.

This article, however, is from 2018. Has there been advancement of this since?

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    Good question, and I really appreciate a good excuse to go looking at this again. IMHO the answer is going to be (and I would have predicted this back in 2018 as well) that the coastal path is far more likely for the first peopling. I just need to figure out how well-accepted that view is now. However, if you follow the way the archeology and genetic studies have been moving pushing back the dates the last couple of decades, a bit of extrapolation would have told you even then which way the wind was blowing.
    – T.E.D.
    Commented May 18 at 23:39
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    Note that this issue is very important to me personally. My family has some Native American heritage, so I have a finger or two in native social media circles. A lot of Native revisionists have been using the ongoing pushing back of dates compared to the old land-bridge ice-free corridor model to "prove" that all the science is somehow utter BS, and thus any old wild theory they want (eg: Natives are somehow a separate species originating in the Americas) must be true instead. This is why I find picking a model that isn't scientifically brittle to be very important.
    – T.E.D.
    Commented May 18 at 23:44

1 Answer 1

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The growing consensus does seem to be that the initial peopling of the Americas took a (west) coastal route. That doesn't preclude later waves taking other routes of course, and there do seem to have been multiple waves, if not a continuous flow.

For the benefit of other readers, there have been two basic models of the initial peopling of the Americas. The first, which likely every adult here had buried in their grade school textbooks they didn't read as a child, was that during the last glacial maximum (LGM, or "ice age") sea levels dropped enough that there was a land-bridge through Beringia between Western North America and Siberia, and for a time an "ice free corridor" between major North American glaciers allowed large mammals, and the humans who lived off them, to travel down into the Americas proper.

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One of the problems with this theory is that it's an exceedingly brittle theory. The corridor in question could only have existed for a brief time during the LGM where the sea levels were low enough to expose the land bridge, but the glaciers small enough that they hadn't grown together yet. Originally the estimates for when that was seemed to mesh fairly well with the estimates for all the Clovis sites south of the Glacier. Since those were the oldest confirmed sites, the theory stood up, but the timing is tight.

The other problem is it inherently implies people needed that ice-free corridor to get past those ice sheets. That's not really true. We know human beings have had boats for 50,000 years. Native peoples using traditional paleolithic technology regularly boat across Beringia today making use of the island chains between the continents. The marine environment there is quite productive, if you know what you're doing. I believe the intervening Cascadia area was found to be one of the most densely populated (iow: productive) areas for hunter-gatherer societies on earth.

So this theory arguably fails Occam's Razor, being both complex in its timing and geography, and unnecessary. It has also been a theory in retreat in the last few decades.

The other major theory is of course that humans used their boats to make the crossing and then work their way down that productive Cascadia area, until they reached an area south of the area of Glaciation where that wasn't necessary. At that point further spread in all (non-glaciated) directions was possible, and happened.

The nice thing about this theory is that it's much more flexible, in that we know humans had boats 50KYA, and were in Siberia 34KYA, both considerably before the LGM (26-20KYA). Sadly, a lot of the evidence for it would have gotten swallowed up by the sea level rise when the glaciers retreated.

A good way to look at theories is to ask what they predict. The interior ("Clovis first") theory predicts we won't find any legit human archeological sites prior to our short land-bridge ice-corridor window. In a way that narrow window makes it a very powerful theory. The coastal migration theory1 instead predicts that we should eventually start finding good evidence of pre-corridor human habitation, possibly leading even as far back as 30KYA, since there really was no barrier.

So what's been happening in recent years is that we've started to narrow down when that bridge-corridor could have existed better, and when our existing sites existed better, and it's increasingly looking like some of the sites pre-date our corridor window.

Numerical dating of Clovis sites has allowed comparison of Clovis dates with dates of other archaeological sites throughout the Americas, and of the opening of the ice-free corridor. Both lead to significant challenges to the Clovis First theory. The Monte Verde site of Southern Chile has been dated at 14,800 BP. The Paisley Cave site in eastern Oregon yielded a 14,500 BP, on a coprolite with human DNA and radiocarbon dates of 13,200 and 12,900 BP on horizons containing western stemmed points. Artifact horizons with non-Clovis lithic assemblages and pre-Clovis ages occur in eastern North America, although the maximum ages tend to be poorly constrained.

Recent studies have suggested that the ice-free corridor opened later (around 13,800 ± 500 years ago) than the earliest widely accepted archaeological sites in the Americas, suggesting that it could have not have been used as the migration route for the earliest peoples to migrate south.

In addition to that, there's been a constant barrage of possible new pre-Clovis sites(1,2,3). All of these currently have disputed dates or only indirect connection to human activity, just as the Clovis-first theory would predict, so nothing's certain yet, but there's an awful lot of smoke.


I'd be remiss here if I didn't mention that the historical prominence of the Clovis-First theory, combined with the deluge of possible pre-Clovis findings, has been a great boon to Native conspiracy theorists. They usually like to refer to the "Bering Strait Theory" as if there's a theory by that name, it's the only scientific theory available, and publish articles about how the latest finding refutes that theory, so everything scientists have been saying must be wrong. The usual alternative peopling theories are either that Native have been here far longer than Clovis (quite possible, if by "far longer" you mean perhaps up to 10ky longer), all the way to Autochthonism (which would imply Native Americans are a completely different species!).


1 - There's a published paper abstract surveying many of the details of the theory here. The main paper is paywalled, sadly.

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    I felt compelled to link to that BS article to back up my statement that such articles are being written. The link does not imply an endorsement, and I hope any search engine crawler hitting this site understands.
    – T.E.D.
    Commented May 19 at 3:00
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    – T.E.D.
    Commented May 21 at 14:54
  • When a SE post gets more than 20 comments (or two commenters back and forth a lot), the system auto-flags it, and provides a nice big button to mods for moving all those comments to chat, which can better handle that. This is how the system is meant to work. Please respect the move to chat and do not continue to post comments on the same issues that are being discussed there here again. Remember that comments are meant to be temporary (aka: "barn cats").
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