A genomic view of the peopling of the Americas
Pontus Skoglund and David Reich

Very interesting article. Thanks Gisele.


“...Under the hypothesis that Native American ancestry
stems from a single founder population that separated
earlier from Eurasian populations, differences in allele
frequencies between Native American groups should
have developed independently from Eurasian allele frequencies.
This simple null hypothesis makes it possible
to explicitly test hypotheses about the number of American
founder populations...”


“...Reich et al. [23""] applied this idea to the first comprehensive
genome-wide data from Native American populations (52 populations,
but none from the continental United States), and concluded that at
least three ancestral populations were required to explain
the similarities between Native Americans and East Asians...”

“...Central and South America fit a
model of a single founder population...”


“...Athabaskan-speaking Chipewyan revealed that
they could not solely have their ancestry from the same
founding population as other Northern-, Meso- and South
American populations...”

And a heavy concentration of mtDNA hg X2...Western Eurasian.


“...genome from the remains of a child
(‘Anzick-1’) buried with Clovis artifacts in
western Montana and directly dated to
12,600 before present (BP) [25""]. This child
was consistent with deriving all of his ancestry
from the same founding population as Central
and South Americans...”

Clovis is a technology not a culture.


“...This suggests that the present-day structuring of the
main ancestry in Native Americans into northern and
southern lineages [23""] dates back to more than
12,600 years ago [25""]. This event divided the ancestry
of present-day Native Americans into two main streams,
one of which includes the ancestors of present-day
Northern Native Americans analyzed (‘NNA’: including
Cree, Ojibwa, and Algonquin), and the other of which
includes the Anzick individual and present-day Central
American groups and South American groups (‘SA’:
including Mixe, Quechua, and Yaghan)...”


“...Diverse population lineages that genetic evidence suggest were present in
Northeast Asia and contributed to the ancestry of present-day Native Americans. These comprise people with ancestry related to present-day Andamanese and Australo-Melanesians (red), people related to present-day East Asians such as Han Chinese (pink), and people related to the 24,000 year old Mal’ta child buried near Lake Baikal (dark blue)...”
Southeast Asia, East Asia and Western Eurasia...today, the Andamanese related
ancestry can be detected as an excess affinity to present-day Amazonians...”


“...More recent genome sequencing [28] of the 9000 year old
Kennewick individual did not provide resolution about this issue.
While the genome analysis convincingly showed that the Kennewick
individual had the great majority of its ancestry from the same deep
source as other present-day Native Americans, his affinity to the SA
and NNA lineages remains ambiguous...”

mtDNA X2a


“...However, the analysis of the genome of a 24,000 year-old individual
from the Mal’ta site near Lake Baikal in Central Siberia
revealed that this model is untenable. The Mal’ta individual
shared genetic affinities to both European (West
Eurasian) and Native American populations [35""]...”


“...However, the data was consistent with a
model in which Native Americans are admixed between
lineages related to Mal’ta on the one hand (between ¼
and ½ of Native American ancestry) and East Asians on
the other hand (Figure 1). Thus, Native Americans and
East Asians do not in fact descend from a common
ancestral population that separated earlier from a lineage
leading to Mal’ta and to West Eurasians [35""]...”


“...The major admixture related to the Mal’ta lineage in the ancestry of
all Native Americans is inconsistent with the assumption
of a simple population split between Native Americans
and East Asians that has been the basis for the most
attempts to date to infer the population split times, and
which have suggested dates of around 23,000 years ago
[33,34"]. The substantial contribution of the Mal’ta lineage
to Native Americans may have the effect of upwardly
biasing estimates of the time of divergence of Native
Americans and East Asians...”


“...Recently, we carried out a stringent test of the null
hypothesis of a single founding population of Central
and South Americans using genome-wide data from diverse
Native Americans [36""]. We detected a statistically
clear signal linking Native Americans in the Amazonian
region of Brazil to present-day Australo-Melanesians and
Andaman Islanders (‘Australasians’). Specifically, we
found that Australasians share significantly more genetic
variants with some Amazonian populations — including
ones speaking Tupi languages — than they do with other
Native Americans. We called this putative ancient Native
American lineage ‘Population Y’ after Ypykue´ra, which
means ‘ancestor’ in the Tupi language family...”


“...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...”




Charlie Hatchett