A paper was published last year about the population genetics and historical genetics of the Blackfoot people. It compared a modest sample of Blackfoot affiliated genomes with other New World and Old World genomes. A small sample size isn't a big problem for a paleo-genetic study, however, because each individual's DNA has so many data points and generations of intermarriage in a fairly closed gene pool makes each individual highly representative of the population as a whole. But while the study does lots of things right, but makes a critical error in its analysis, which seriously detracts from the reliability of the analysis. This error arises from a weak review of the literature and deficient peer-review, which leads to an erroneous analysis.
The big problem with the paper is that it makes flawed assumptions about the peopling of the Americas. It relies on a model in which all Native Americans fit into two groups: Native North Americans (ANC-B) and Central and Southern Americans (ANC-A), and tries to determine where the Blackfoot people fit into that model.
The trouble is that the established paradigm is more complicated. While ANC-A is a valid and pretty much unified group that descend from basically Pacific coast route peoples in a primary founding population wave perhaps 14,000 years ago, Native Americans in North America have a more complex ancestry.
North American Native Americans have the lineages found in ANC-A (which results from a serial founder effect) and probably a least two other clades close in time to the initial founding era that spread into different parts of North America.
Then, around 3500-2400 BCE, the ancestors of the Na-Dene people migrated to Alaska from Northeast Asia and admixed with pre-existing populations (their languages have remote but traceable connections to the Paleo-Siberian Ket people, whose language family is named after the Yenesian River in central Siberia) and are associated with the Saqqaq Paleoeskimo culture who also were the source of the Dorest Paleo-Eskimo populations (see also here and here) About 10% of Na-Dene ancestry is distinct from the initial founding population of the Americas.[2] The Na-Dene, like Inuits, have Y-DNA haplogroups that are specific to them and of more recent origin that the founding Y-DNA haplogroups of the Americas.[3].
And then, a final significant pre-Columbian wave with lasting demographic impact arrived from Northeast Asia, perhaps around 500s and 600s CE, and they are the ancestors of the Inuits (a.k.a. modern Eskimo-Aleut peoples) who have their roots in an Arctic and sub-Arctic population also known as the Thule. The 6th to 7th century CE Berginian Birnirk culture (in turn derived from Siberian populations) is the source of the proto-Inuit Thule people, who were the last substantial and sustained pre-Columbian peoples to migrate to the Americas.
A paper in 2020 refined and confirmed this analysis, and the 2024 paper even adopts its NNA v. SNA classification while failing to recognize the distinct temporal waves involved in the pre-Columbian peopling of the Americas.
See generally:
The critical problem with the paper is that Athabascans are a poor representative of Northern Native American lineages from the founding era ca. 14,000 years ago, because they have significant Na-Dene wave admixture, also shared, for example, with the Navajo, who migrated in turn migrated from what is now central to western Canada to the American Southeast around 1,000 CE (possibly, in part, due to the push factor of the incoming wave of proto-Inuits).
In contrast, the vast majority of North American Native Americans have no Na-Dene or Inuit ancestry and are in population genetic continuity with one or more of the several founding populations of North America. Almost any other choice of a North American Native American comparison population would have been much, much better.
In contrast, the Karitiana are indeed representative (and the standard choice to represent) the ANC-A population.
It is entirely plausible that the Blackfoot are indeed from a wave of North American founding population that is under sampled and that their lineage is not represented in prior published works.
Latin American indigenous peoples (and to a lesser extent and more recently, Canadian First Peoples) have, in general, been more receptive to population genetic work by anthropologists and Native American populations in the United States who have given these researchers the cold shoulder until very recently, due to a historical legacy that has understandably fostered distrust of people associated with the establishment in the U.S. including anthropologists. So, Native Americans in the U.S. are greatly under sampled.
But, because the thrust of the paper heavily relies on comparisons between Blackfoot DNA and Athabascan DNA with misguided assumptions about the Athabascan population histories entering into the calculations and analysis, it is hard to confidently extract reliable conclusions from that analysis. The Athabascan may be mostly ANC-B, but are probably the most divergent sample one could use to represent that population, particularly since no attempt is made to distinguish the ancestry components in that population. This seriously confounds the efforts to pin down the prehistoric time line.
A good quality peer-review should have caught this problem, but peer-review in practice is less effective than it is given credit for being.
Realistically, the only way to really do it right would be to withdraw the 2024 paper and replace it with a new paper that reanalyzes the Blackfoot genetic data by comparing it to a more suitable representative of North American Native American ancestry.
Studies of human genomes have aided historical research in the Americas by providing rich information about demographic events and population histories of Indigenous peoples, including the initial peopling of the continents. The ability to study genomes of Ancestors in the Americas through paleo-genomics has greatly increased the power and resolution at which we can infer past events and processes. However, few genomic studies have been completed with populations in North America, which could be the most informative about the initial peopling process. Those that have been completed in North America have identified Indigenous Ancestors with previously undescribed genomic lineages that evolved in the Late Pleistocene, before the split of two lineages [called the “Northern Native American (NNA)” or “ANC-B” and “Central and Southern American (SNA)” or “ANC-A” lineages] from which all present-day Indigenous populations in the double continent that have been sampled derive much, if not all, their ancestry before European contact. Specifically, the lineage termed “Ancient Beringian” was ascribed to a genome in an Ancestor who lived 11,500 years ago at Xaasaa Na’ (Upward Sun River) and named Xach’itee’aanenh t’eede gaay (USR1) by the local Healy Lake Village Council in Alaska. An Ancestor who lived 9500 years ago at what is now called Trail Creek Caves on the Seward Peninsula, Alaska, also belongs to the Ancient Beringian lineage. In addition, another Ancestor, under the stewardship of Stswecem’c Xgat’tem First Nation, who lived in what is now called British Columbia, belongs to a distinct genomic lineage that predates the NNA-SNA split but postdates the split from Ancient Beringians on the Americas’ genomic timeline. This Ancestor was identified at Big Bar Lake near the Frasier River and lived 5600 years ago. Thus, these previous studies of North American Indigenous Ancestors have successfully helped to identify previously unknown genomic diversity. However, the ancient lineages identified in these studies have not been observed in samples of Indigenous peoples of the Americas living today. Research in Mesoamerica and South America suggests that certain sampled populations (e.g., Mixe) have at least partial ancestry in present-day Indigenous groups from unknown genomic lineages in the Americas, possibly dating as far back as 25,000 years ago. . . .With multiple genomic analyses showing the ancient Blood/Blackfoot clustering together with present-day Blood/Blackfoot but on a separate lineage from other North and South American groups, we created a demographic model using momi2, which used the site frequency spectra of present-day Blood/Blackfoot, Athabascan (as a representative of Northern Native American lineage), Karitiana (as a representative of Southern Native American lineage), and Han, English, Finnish, and French representing lineages from Eurasia. The best-fitting model shows a split time of the present-day Blood/Blackfoot at 18,104 years ago, followed by a split of Athabascan and Karitiana at 13,031 years ago.
The paper and its abstract are as follows:
Mutually beneficial partnerships between genomics researchers and North American Indigenous Nations are rare yet becoming more common. Here, we present one such partnership that provides insight into the peopling of the Americas and furnishes another line of evidence that can be used to further treaty and aboriginal rights. We show that the genomics of sampled individuals from the Blackfoot Confederacy belong to a previously undescribed ancient lineage that diverged from other genomic lineages in the Americas in Late Pleistocene times. Using multiple complementary forms of knowledge, we provide a scenario for Blackfoot population history that fits with oral tradition and provides a plausible model for the evolutionary process of the peopling of the Americas.
No comments:
Post a Comment