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Milkyway
07-22-2020, 05:07 PM
Finally there's solid evidence supporting a pre-LGM settlement of the Americas.

Evidence of human occupation in Mexico around the Last Glacial Maximum (https://www.nature.com/articles/s41586-020-2509-0)

Abstract

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico—which holds a key geographical position in the Americas—is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7,8,9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave—a high-altitude site in central-northern Mexico—that corroborate previous findings in the Americas10,11,12,13,14,15,16,17of cultural evidence that dates to the Last Glacial Maximum (26,500–19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000–31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.

The timing and effect of the earliest human arrivals in North America (https://www.nature.com/articles/s41586-020-2491-6)

Abstract

The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed ‘Clovis-first’)—suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points1—has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5–19 thousand years ago)2,3 but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7–12.9 thousand years before ad 2000)4. We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.

pmokeefe
07-22-2020, 05:30 PM
NEWS AND VIEWS 22 JULY 2020 (in Nature)
Evidence grows that peopling of the Americas began more than 20,000 years ago (https://www.nature.com/articles/d41586-020-02137-3)
The long-debated timing of the peopling of the Americas comes into focus, thanks to some archaeological findings. What are the implications of a revised timeline for our understanding of these earliest inhabitants?
Ruth Gruhn

pmokeefe
07-22-2020, 07:50 PM
NATURE PODCAST 22 JULY 2020
When did people arrive in the Americas? New evidence stokes debate (https://www.nature.com/articles/d41586-020-02200-z)
New evidence may push back the date on human arrival to the Americas, and an examination of science’s flaws.
Nick Howe &
Shamini Bundell

pmokeefe
07-22-2020, 07:53 PM
NEWS 22 JULY 2020 (Nature)
Controversial cave discoveries suggest humans reached Americas much earlier than thought (https://www.nature.com/articles/d41586-020-02190-y)
Archaeologists say stone artefacts point to occupation more than 30,000 years ago — but not everyone is convinced.
Colin Barras

Piquerobi
07-22-2020, 09:01 PM
There have been false positives for an early entry into the Americas before DNA testing began. I'd be cautious. The best evidence perhaps would be that of human remains' DNA. So far the lineages studied seem to have established a later period of entry, as far as Native Americans are concerned. Perhaps others came to the Americas before the Native Americans. I've also wondered if Denisovans and other "archaic human" types did not manage to get to the Americas too.

RP48
07-22-2020, 10:52 PM
No human or animal remains were found at this site. The tools are formed of a type of limestone. I see simple flakes. It is not a slam dunk but may amount to something.

Megalophias
07-23-2020, 03:43 AM
Dang it, why can't it ever just be directly dated human remains, or barbed bone harpoons, or ivory carvings or something?

Milkyway
07-25-2020, 05:33 PM
If humans arrived in the Americas before 20, 25 or 30 kya, then how come:

-There are no bones older than 12 kya (I think that Anzick-1 is amongst the oldest tested; the others are younger).
-There are no carvings, sculptures, figurines, etc., older than 15 kya.
-Most if not all Y-DNA and mtDNA clades of Native Americans show coalescence ages that are younger than 20 kya.

We have plenty of bones of Neanderthals and other ancient hominids that lived >50 kya in Eurasia and Africa. We even have the bones of 42 kya Mungo Man from Australia. One explanation is that, if these flakes were made by humans, then the population was very small and probably didn't survive for long.

We now have the DNA of a 34 kya Mongolian (https://www.biorxiv.org/content/10.1101/2020.06.03.131995v1.full.pdf) (Salkhit-1) that shows no connection to present-day or ancient Native Americans. So they probably didn't exist yet as a genetically distinctive population.

If there was a population that arrived just before the LGM 20-25 kya, and this population was closely related to the others that came a few millennia later (20-15 kya), then it might not be possible to detect their presence by examining the DNA of living people alone.

There are other things to consider if we assume that humans have been in the Americas for a long (>30 kya) time:

-The Americas show the lowest amount of genetic diversity of any (sub)continent (even lower than Sahul, South Asia and Europe).
-Native American peoples, for the most part, seem to be adapted to cold climates, even the ones that live in the Amazon.
-Blood groups and fingerprints show that Native Americans are closely related to East Asian populations (or at least closer than Europeans and Africans are).

Ruderico
07-25-2020, 08:26 PM
There's a guy on YT, whom I follow, that made a quick video about it. Going through what he says I'd agree with him that the conclusion is very dubious

https://youtu.be/eBoVf2uXU5w

Caius Agrippa
07-25-2020, 08:55 PM
There have been false positives for an early entry into the Americas before DNA testing began. I'd be cautious. The best evidence perhaps would be that of human remains' DNA. So far the lineages studied seem to have established a later period of entry, as far as Native Americans are concerned. Perhaps others came to the Americas before the Native Americans. I've also wondered if Denisovans and other "archaic human" types did not manage to get to the Americas too.

Very little vestiges of pre-Siberian DNA has been found in isolated tribes in the Amazon, pointing to a pre-Siberian population in the Americas.

Milkyway
07-25-2020, 10:12 PM
There's a guy on YT, whom I follow, that made a quick video about it. Going through what he says I'd agree with him that the conclusion is very dubious

https://youtu.be/eBoVf2uXU5w

Link not working... :\

Milkyway
07-25-2020, 10:18 PM
Very little vestiges of pre-Siberian DNA has been found in isolated tribes in the Amazon, pointing to a pre-Siberian population in the Americas.

Maybe you're referring to the Australasian connection (https://www.newscientist.com/article/2184840-indigenous-peoples-in-the-amazon-and-australia-share-some-ancestry/) that was detected in a paper? I think that there could be several explanations for this, including population structure in the Native American founding population (that supposedly lived in Siberia or Beringia).

Caius Agrippa
07-25-2020, 11:58 PM
Maybe you're referring to the Australasian connection (https://www.newscientist.com/article/2184840-indigenous-peoples-in-the-amazon-and-australia-share-some-ancestry/) that was detected in a paper? I think that there could be several explanations for this, including population structure in the Native American founding population (that supposedly lived in Siberia or Beringia).

That's possible, but the fact it appeared only in some particular Amerindian tribes can lead to the hypothesis of a very little portion of an older Australasian substrate surviving only around the Amazon region.

Piquerobi
07-26-2020, 12:38 AM
Very little vestiges of pre-Siberian DNA has been found in isolated tribes in the Amazon, pointing to a pre-Siberian population in the Americas.

It is an autosomal signal which can be interpreted in different ways, and it likely depends on the method of inferring autosomal components too:


We found that the patterns of genomic variation of present-day Amazonians could be explained by as little as 2% admixture from an Australasian-related population, that would thus have penetrated deep inside the Americas without mixing with the main ancestral lineage of present-day Native Americans. Alternatively, the patterns could be explained by a larger proportion of ancestry (2-85%) from a population that existed in a substructured Northeast Asia, and was similar to the main lineage that gave rise to other Native Americans while retaining more Australasian affinity.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5161672/

As for mtDNA and yDNA lineages, there has been no proof of a pre-Native American population in the Americans so far. Luzia turned out to cluster perfectly with Native Americans, f.e. But I think keeping an "open minded" attitude is the safest.

We tend to view the Americas as separated from the Old World by the Atlantic Ocean, and yet but for a few kilometers it is connected to it via Northeast Asia.

How close is Alaska to Russia?


The narrowest distance between mainland Russia and mainland Alaska is approximately 55 miles. However, in the body of water between Alaska and Russia, known as the Bering Strait, there lies two small islands known as Big Diomede and Little Diomede. Interestingly enough, Big Diomede is owned by Russia while Little Diomede is owned by the US. The stretch of water between these two islands is only about 2.5 miles wide and actually freezes over during the winter so you could technically walk from the US to Russia on this seasonal sea ice.
https://www.alaskacenters.gov/faqs-people-often-ask/how-close-alaska-russia#:~:text=The%20narrowest%20distance%20betwee n%20mainland,Big%20Diomede%20and%20Little%20Diomed e

Japanese maps usually show this connection:

38710

Ruderico
07-26-2020, 09:31 AM
Link not working... :\

Sorry, hopefully this one will

https://www.youtube.com/watch?v=n55FfI7AzT4

Milkyway
07-26-2020, 05:37 PM
So it seems that the Chiquihuite people kept producing the same tools in the same site for almost 20,000 years... which is somewhat surprising (or unlikely?). Quoting the article (https://www.nature.com/articles/s41586-020-2509-0):


The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia.

Interestingly, a recent study on Argentines (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0233808) found genetic traces of a fourth indigenous group that doesn't exist anymore and diverged early (>12 kya) from the main three other indigenous South American groups identified to date. Still, there's no mention of Australasians.

Milkyway
07-26-2020, 06:01 PM
As for mtDNA and yDNA lineages, there has been no proof of a pre-Native American population in the Americans so far. Luzia turned out to cluster perfectly with Native Americans, f.e. But I think keeping an "open minded" attitude is the safest.

If there was an Australasian-like population that arrived in the Americas 30-40 kya, then we'd likely find some mtDNA or Y-DNA lineages that are deeply diverged from the others and/or show a connection to the Australasian ones. Apparently, that's not the case (or I'm not aware of any study supporting this).

In Europe, Y-DNA haplogroup C1a2 (https://en.wikipedia.org/wiki/Haplogroup_C-V20) or C-V20 arrived 35 kya and is still found at very low frequencies in European males. On the contrary, some mtDNA haplogroups like M became extinct in the Mesolithic.

It could also have happened as with Neanderthals/Denisovans, that left a small imprint in our genomes but no mtDNA/Y-DNA lineages. It is possible that the reason has to do with the ancestral population to all non-Africans being very small and losing genetic diversity after a bottleneck.

Ruderico
07-26-2020, 06:08 PM
So it seems that the Chiquihuite people kept producing the same tools in the same site for almost 20,000 years... which is somewhat surprising (or unlikely?).

Yeah I'd say the odds of that are close to 0, the tools were probably from the younger layer. I've never heard of any people keeping their material culture and location for 20000 years.

Milkyway
07-26-2020, 07:11 PM
Yeah I'd say the odds of that are close to 0, the tools were probably from the younger layer. I've never heard of any people keeping their material culture and location for 20000 years.

We have the Mousterian industry produced by Neanderthals and possibly ancient H. sapiens that lasted >100,000 years, but I agree that it's unlikely that this unknown (this is also intriguing!) industry that has only been found in one site so far remained almost unchanged for so long.