Bayesian inferences suggest that Amazon Yunga Natives diverged from Andeans less than 5000 ybp: implications for South American prehistory

Abstract

BackgroundArchaeology reports millenary cultural contacts between Peruvian Coast-Andes and the Amazon Yunga, a rainforest transitional region between Andes and Lower Amazonia. To clarify the relationships between cultural and biological evolution of these populations, in particular between Amazon Yungas and Andeans, we used DNA-sequence data, a model-based Bayesian approach and several statistical validations to infer a set of demographic parameters.ResultsWe found that the genetic diversity of the Shimaa (an Amazon Yunga population) is a subset of that of Quechuas from Central-Andes. Using the Isolation-with-Migration population genetics model, we inferred that the Shimaa ancestors were a small subgroup that split less than 5300 years ago (after the development of complex societies) from an ancestral Andean population. After the split, the most plausible scenario compatible with our results is that the ancestors of Shimaas moved toward the Peruvian Amazon Yunga and incorporated the culture and language of some of their neighbors, but not a substantial amount of their genes. We validated our results using Approximate Bayesian Computations, posterior predictive tests and the analysis of pseudo-observed datasets.ConclusionsWe presented a case study in which model-based Bayesian approaches, combined with necessary statistical validations, shed light into the prehistoric demographic relationship between Andeans and a population from the Amazon Yunga. Our results offer a testable model for the peopling of this large transitional environmental region between the Andes and the Lower Amazonia. However, studies on larger samples and involving more populations of these regions are necessary to confirm if the predominant Andean biological origin of the Shimaas is the rule, and not the exception.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0174-3) contains supplementary material, which is available to authorized users.

MtDNA and Y‐chromosomal diversity in the Chachapoya, a population from the northeast Peruvian Andes‐Amazon divide

“…We are aware of the difficulties in assessing whether this distinct pattern reflects very early genetic signatures or the action of different evolutionary forces through time. Overall, even though our study shows some general patterns in the populations from transitional zones, the distinctiveness of the Chachapoya suggests that extrapolations to similar regions (e.g., Scliar et al, 2014) must be considered with care. The genetic profile of the Chachapoya indicates that populations that developed in "intermediate ecological regions" have a complex genetic composition which has been influenced by their position with regard to other civilizations in the northeast Andes.…”

“…In this study, we have explored the demographic history of a region between two major ecosystems, the Andes and the Amazonian rainforest, by assessing the Y-chromosomal and mitochondrial DNA (mtDNA) diversity in the presentday Chachapoya in the northeastern Peruvian cloud forest. To date, very few of these "transitional area" populations have been studied (Barbieri et al, 2014;Corella et al, 2007Corella et al, , 2008Scliar et al, 2014), with these tending to show a complex genetic makeup (Tarazona-Santos et al, 2001). This is the first large scale study of the extant Chachapoya.…”

“…To date, very few of these "transitional area" populations have been studied (Barbieri et al, 2014;Corella et al, 2007Corella et al, , 2008Scliar et al, 2014), with these tending to show a complex genetic makeup (Tarazona-Santos et al, 2001). To date, very few of these "transitional area" populations have been studied (Barbieri et al, 2014;Corella et al, 2007Corella et al, , 2008Scliar et al, 2014), with these tending to show a complex genetic makeup (Tarazona-Santos et al, 2001).…”

Pharmacogenomic Assessment of Mexican and Peruvian populations

“…A study of 25 regions of Peru found different levels of European ancestry depending on location [19]. As with the Mexican population this admixture provides a distinct population [20–22] that does not allow for assumptions from existing data for any one ethnic group.…”

“…For warfarin low dose prediction, 45% of Mexicans carried the CYP2C9 / VKORC1 genotype combination compared with only 28% of Peruvians [6]. For this combination the Peruvians were most similar to the African populations (22–23%) despite the low incidence of African admixture [20–22], and the Mexicans were closer to the Caucasian population (55%) [6]. …”