Population genetic analysis of hunter-gatherer groups from the late Holocene of the Salitroso Lake (Santa Cruz, Argentina)

Abstract

During the Late Holocene, human population dynamics in Patagonia was conditioned by environmental factors, since a climate shift towards more arid conditions affected watersheds and their associated environments. In particular, for the Salitroso Lake basin (northwest of Santa Cruz province, Argentina) has been proposed a reduction in residential mobility, with a consequent population nucleation around this permanent water source. In this study, some archaeological concerns about the Salitroso Lake population were addressed through the study of ancient mitochondrial DNA. In order to evaluate the genetic composition of the lake's inhabitants and detect a possible population expansion, skeletal remains of 28 individuals (dated between 2,600 and 300 years AP) were processed. We were able to extract DNA and analyze the Hipervariable Region I of the mitochondrial genome in 16 samples. Four maternal lineages were found: D1g (43,7%), B2 (31,3%), C1 (18,8%) and D4h3a (6,2%). Some individuals presented derived haplotypes, many of them only found in the basin. The presence of the B2 lineage is interesting, since it has been scarcely described in pre-Hispanic groups in Patagonia. In addition, high levels of genetic variability were observed in the analyzed sample, which was also different from other ancient Patagonian populations. Although the most recent archaeological analyses suggest a population growth during the last 500 years of occupation of the basin, no genetic evidence of this process was found.