Enclaves of genetic diversity resisted Inca impacts on population history

Chiara Barbieri,Jairo Valqui,Paul Heggarty,Aviva Shimelman,Ricardo Fujita,Stefan Ziemendorff,Roland Schröder,José R Sandoval,Lutz Roewer,Mark Stoneking,Russell Gray,Maria Geppert

doi:10.1038/s41598-017-17728-w

Abstract

The Inca Empire is claimed to have driven massive population movements in western South America, and to have spread Quechua, the most widely-spoken language family of the indigenous Americas. A test-case is the Chachapoyas region of northern Peru, reported as a focal point of Inca population displacements. Chachapoyas also spans the environmental, cultural and demographic divides between Amazonia and the Andes, and stands along the lowest-altitude corridor from the rainforest to the Pacific coast. Following a sampling strategy informed by linguistic data, we collected 119 samples, analysed for full mtDNA genomes and Y-chromosome STRs. We report a high indigenous component, which stands apart from the network of intense genetic exchange in the core central zone of Andean civilization, and is also distinct from neighbouring populations. This unique genetic profile challenges the routine assumption of large-scale population relocations by the Incas. Furthermore, speakers of Chachapoyas Quechua are found to share no particular genetic similarity or gene-flow with Quechua speakers elsewhere, suggesting that here the language spread primarily by cultural diffusion, not migration. Our results demonstrate how population genetics, when fully guided by the archaeological, historical and linguistic records, can inform multiple disciplines within anthropology.

Highlights

Genetic studies have begun to contribute significantly to our understanding of the pre-colonial history of the Americas, and are able to fill in some of the gaps in the archaeological and historical records
Quechua did once serve as lingua franca for the Inca Empire, but that can explain only some of its diversity and distribution through the Andes
To introduce a genetic perspective on these scenarios from archaeology, history and linguistics, this study focuses on uniparental markers: i.e. mtDNA and the non-recombinant portion of the Y chromosome

Summary

Introduction

Genetic studies have begun to contribute significantly to our understanding of the pre-colonial history of the Americas, and are able to fill in some of the gaps in the archaeological and historical records. Never seems to have been dominantly established across northern Peru, and is spoken, in diverse local forms, only in sporadic pockets scattered across the region (Fig. 1) One of these pockets is Chachapoyas, where a small proportion of the present-day population, in a handful of small communities, still speaks a moribund variety of Quechua that is difficult to classify within the family’s phylogeny. Another pocket of Quechua, covered in this study, is the town of Lamas in San Martín province, in the Andean foothills at the edge of Amazonia. Historical and linguistic contextualization, see the Supplementary Text

Methods

Results

Conclusion