The genetic history of the Southern Andes from present-day Mapuche ancestry.

The southernmost regions of South America harbor some of the earliest evidence of human presence in the Americas. However, connections with the rest of the continent and the contextualization of present-day indigenous ancestries remain poorly resolved. In this study, we analyze the genetic ancestry of one of the largest indigenous groups in South America: the Mapuche. We generate genome-wide data from 64 participants from three Mapuche populations in Southern Chile: Pehuenche, Lafkenche, and Huilliche. Broadly, we describe three main ancestry blocks with a common origin, which characterize the Southern Cone, the Central Andes, and Amazonia. Within the Southern Cone, ancestors of the Mapuche lineages differentiated from those of the Far South during the Middle Holocene and did not experience further migration waves from the north. We find that the deep genetic split between the Central and Southern Andes is followed by instances of gene flow, which may have accompanied the southward spread of cultural traits from the Central Andes, including crops and loanwords from Quechua into Mapudungun (the language of the Mapuche). Finally, we report close genetic relatedness between the three populations analyzed, with the Huilliche characterized additionally by intense recent exchanges with the Far South. Our findings add new perspectives on the genetic (pre)history of South America, from the first settlement through to the present-day indigenous presence. Follow-up fieldwork took these results back to the indigenous communities to contextualize the genetic narrative alongside indigenous knowledge and perspectives. VIDEO ABSTRACT.

The multifaceted genomic history of Ashaninka from Amazonian Peru.

Despite its crucial location, the western side of Amazonia between the Andes and the source(s) of the Amazon River is still understudied from a genomic and archaeogenomic point of view, albeit possibly harboring essential information to clarify the complex genetic history of local Indigenous groups and their interactions with nearby regions,1,2,3,4,5,6,7,8 including central America and the Caribbean.9,10,11,12 Focusing on this key region, we analyzed the genome-wide profiles of 51 Ashaninka individuals from Amazonian Peru, observing an unexpected extent of genomic variation. We identified at least two Ashaninka subgroups with distinctive genomic makeups, which were differentially shaped by the degree and timing of external admixtures, especially with the Indigenous groups from the Andes and the Pacific coast. On a continental scale, Ashaninka ancestors probably derived from a south-north migration of Indigenous groups moving into the Amazonian rainforest from a southeastern area with contributions from the Southern Cone and the Atlantic coast. These ancestral populations diversified in the variegated geographic regions of interior South America, on the eastern side of the Andes, differentially interacting with surrounding coastal groups. In this complex scenario, we also revealed strict connections between the ancestors of present-day Ashaninka, who belong to the Arawakan language family,13 and those Indigenous groups that moved further north into the Caribbean, contributing to the early Ceramic (Saladoid) tradition in the islands.14,15.

Weaving Mitochondrial DNA and Y-Chromosome Variation in the Panamanian Genetic Canvas.

The Isthmus of Panama was a crossroads between North and South America during the continent's first peopling (and subsequent movements) also playing a pivotal role during European colonization and the African slave trade. Previous analyses of uniparental systems revealed significant sex biases in the genetic history of Panamanians, as testified by the high proportions of Indigenous and sub-Saharan mitochondrial DNAs (mtDNAs) and by the prevalence of Western European/northern African Y chromosomes. Those studies were conducted on the general population without considering any self-reported ethnic affiliations. Here, we compared the mtDNA and Y-chromosome lineages of a new sample collection from 431 individuals (301 males and 130 females) belonging to either the general population, mixed groups, or one of five Indigenous groups currently living in Panama. We found different proportions of paternal and maternal lineages in the Indigenous groups testifying to pre-contact demographic events and genetic inputs (some dated to Pleistocene times) that created genetic structure. Then, while the local mitochondrial gene pool was marginally involved in post-contact admixtures, the Indigenous Y chromosomes were differentially replaced, mostly by lineages of western Eurasian origin. Finally, our new estimates of the sub-Saharan contribution, on a more accurately defined general population, reduce an apparent divergence between genetic and historical data.

Archaeogenomic distinctiveness of the Isthmo-Colombian area.

The recently enriched genomic history of Indigenous groups in the Americas is still meager concerning continental Central America. Here, we report ten pre-Hispanic (plus two early colonial) genomes and 84 genome-wide profiles from seven groups presently living in Panama. Our analyses reveal that pre-Hispanic demographic events contributed to the extensive genetic structure currently seen in the area, which is also characterized by a distinctive Isthmo-Colombian Indigenous component. This component drives these populations on a specific variability axis and derives from the local admixture of different ancestries of northern North American origin(s). Two of these ancestries were differentially associated to Pleistocene Indigenous groups that also moved into South America, leaving heterogenous genetic footprints. An additional Pleistocene ancestry was brought by a still unsampled population of the Isthmus (UPopI) that remained restricted to the Isthmian area, expanded locally during the early Holocene, and left genomic traces up to the present day.