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. 2012 May;22(5):811-20.
doi: 10.1101/gr.131722.111. Epub 2012 Feb 14.

Rapid Coastal Spread of First Americans: Novel Insights From South America's Southern Cone Mitochondrial Genomes

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Rapid Coastal Spread of First Americans: Novel Insights From South America's Southern Cone Mitochondrial Genomes

Martin Bodner et al. Genome Res. .
Free PMC article

Abstract

It is now widely agreed that the Native American founders originated from a Beringian source population ~15-18 thousand years ago (kya) and rapidly populated all of the New World, probably mainly following the Pacific coastal route. However, details about the migration into the Americas and the routes pursued on the continent still remain unresolved, despite numerous genetic, archaeological, and linguistic investigations. To examine the pioneering peopling phase of the South American continent, we screened literature and mtDNA databases and identified two novel mitochondrial DNA (mtDNA) clades, here named D1g and D1j, within the pan-American haplogroup D1. They both show overall rare occurrences but local high frequencies, and are essentially restricted to populations from the Southern Cone of South America (Chile and Argentina). We selected and completely sequenced 43 D1g and D1j mtDNA genomes applying highest quality standards. Molecular and phylogeographic analyses revealed extensive variation within each of the two clades and possibly distinct dispersal patterns. Their age estimates agree with the dating of the earliest archaeological sites in South America and indicate that the Paleo-Indian spread along the entire longitude of the American double continent might have taken even <2000 yr. This study confirms that major sampling and sequencing efforts are mandatory for uncovering all of the most basal variation in the Native American mtDNA haplogroups and for clarification of Paleo-Indian migrations, by targeting, if possible, both the general mixed population of national states and autochthonous Native American groups, especially in South America.

Figures

Figure 1.
Figure 1.
Phylogenetic tree of southern South American haplogroups D1g and D1j. This tree includes 43 new complete mtDNA sequences belonging to D1g and D1j and illustrates subhaplogroup affiliations. The position of the revised Cambridge Reference Sequence (rCRS) (Andrews et al. 1999) is indicated for reading off sequence motifs. Samples #1–#26 belong to D1g, while samples #27–#43 belong to D1j. The country of origin of the sample donors is indicated by circle color (see legend). All SNPs and indels are shown on the branches except for cytosine insertions at np 309. In the case of transversions, insertions, or heteroplasmic mutations, the base is indicated according to the IUPAC nucleotide code. The prefix @ indicates the reversion of a mutation occurring earlier in the phylogeny. The suffixes “s” and “ns” indicate synonymous and nonsynonymous substitutions, respectively, while “∼t” and “∼r” indicate affected positions in tRNA and rRNA loci, respectively. Recurrent mutations within the phylogeny are underlined. The mutational motifs of the previously described D1 subhaplogroups (D1a–D1f, D1h, D1i) are also shown (van Oven and Kayser 2009) (Build 13). D1 sequences #44 and #45 are also new. Additional information regarding each of the 45 novel mitochondrial genomes is available in Supplemental Tables S1 and S2.
Figure 2.
Figure 2.
Origin of D1g and D1j sample donors. The provinces/states of origin of the sample donors of the fully sequenced mtDNA haplogroup D1g (circles) and D1j (squares) samples included in this study (see Fig. 1) are shown. Details are listed in Supplemental Table S1. The sizes of the circles and squares correspond to the number of samples assigned to a certain province/state, while their colors indicate subhaplogroups (see legend). The yellow arrow points at the location of the Monte Verde site (Chile).
Figure 3.
Figure 3.
Migration models into the South American continent. The three migration models discussed are illustrated along with a timing of events resulting from our calculations: the incubation of population groups arriving from the north in a northern area of South America and a late split into coastal and continental population groups after the full development of all major D1g and D1j subclades (A); a coastal southward migration followed by the colonization of the continental interior by trans-Andean migrations, with limited later exchange along the cordillera (B); and a coastal southward migration and trans-Andean colonization of the continental interior, followed by extensive trans-Andean migrations, especially in the south, with the Mapuches favoring bidirectional gene flow between west and east in the Southern Cone (C). The latter is the most likely model from our results.

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