Ancient mitochondrial genomes from Coastal Patagonia: Population structure and human dispersal in the Southern Cone
In this study we analyzed 11 newly generated ancient mitochondrial genomes of individuals who lived on the northern coast of Santa Cruz Province (Argentinian Patagonia) between 2400 and 390 years BP. In combination with previously published data, we investigate the population history of these coastal hunter-gatherers through the analysis of regional and temporal patterns of genetic variability and contribute to ongoing debates on human dispersal routes into southern South America. We found low haplogroup and sequence diversity within the sample, as evidenced by the presence of only three mitochondrial subhaplogroups (D1g [55%], C1 [27%], and C1b13 [18%]), suggesting that the population overall was likely impacted by genetic drift possibly resulting from environmental constraints affecting population sizes over this time period. We observed genetic continuity in the northern coast of Santa Cruz throughout the late Holocene. In addition, we found no shared maternal lineages among individuals within two joint burials.  In comparison with other ancient mitogenomes, we found that the haplotypic composition of the studied ensemble differed from that of all other ancient populations from the south of the Southern Cone of the Americas, except those from Tierra del Fuego. Phylogenetic analyses revealed that these ancient individuals' lineages coalesced in the middle Holocene along with those from the regions of Tierra del Fuego, Central Argentina, and Pampas, suggesting that their linkages may be due to common origins and not subsequent gene flow. Finally, our findings are compatible with either an initial settlement along an Atlantic route or the confluence of inland and coastal dispersal routes during the Holocene, highlighting the need for improved geographic representation in future genetic datasets.