Another paper on the peopling of America (Maanasa Raghavan, et al., (2015) Genomic evidence for the Pleistocene and recent population history of Native Americans Science, 23 July 2015 / Page 1 / 10.1126/science.aab3884) proposes that "the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia. Following their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 KYA, one that is now dispersed across North and South America and the other is restricted to North America."
No early peopling here, no ancient archaic Denisovans or pre-East Asians entering America long ago.
The founding populations were isolated in Beringia and then entered America and that is all there is to it!
But... they do recognize that some Native Americans are close to Austro-Melanesians:
"We found that some American populations, including the Aleutian Islanders, Surui, and Athabascans are closer to Australo-Melanesians compared to other Native Americans, such as North American Ojibwa, Cree and Algonquin, and the South American Purepecha, Arhuaco and Wayuu (fig. S10). The Surui are, in fact, one of closest Native American populations to East Asians and Australo-Melanesians, the latter including Papuans, non-Papuan Melanesians, Solomon Islanders, and South East Asian hunter-gatherers such as Aeta (fig. S10).
We acknowledge that this observation is based on the analysis of a small fraction of the whole genome and SNP chip genotype datasets, especially for the Aleutian Islander data that is heavily masked due to recent admixture with Europeans (28), and that the trends in the data are weak.
Nonetheless, if it proves correct, these results suggest there may be a distant Old World signal related to Australo Melanesians and East Asians in some Native Americans. The widely scattered and differential affinity of Native Americans to the Australo-Melanesians, ranging from a strong signal in the Surui to much weaker signal in northern Amerindians such as Ojibwa, points to this gene flow occurring after the initial peopling by Native American ancestors."
So they recognize the strong links between Austro - Melanesians and Amerindians but suggest it happened after the peopling of America... and that the signal may be due to a limited analysis of the genome (the small sample tested by some statistical fluke gives a high relationship between both populations, but maybe a larger sample of the genome may yield a different outcome).
I find this conclusion rather odd: "The widely scattered and differential affinity of Native Americans to the Australo-Melanesians, ranging from a strong signal in the Surui to much weaker signal in northern Amerindians such as Ojibwa, points to this gene flow occurring after the initial peopling by Native American ancestors".
Odd because it can also be interpreted as follows: South American Natives have a higer signal of Austronesian genes because they are what is left of an ancient migration that was overwhelmed by East Asians in North America.
The tide of Siberian people replaced almost all Austronesian genes in North America and also in South America but those living in relative isolation in the Amazon retained some of the original genes...
Both (theirs and mine) theories explain the gradient (high in S. America - low in N. America) in the Austronesian genetic signal... so which is the best explanation?
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