Genetic Structure of Native Populations from the Gran Chaco Region, South America

Abstract

The Gran Chaco region is a vast subtropical plain in South America that covers part of the territories of Argentina, Paraguay, and Bolivia, being the refuge of some of the last hunter-gatherer groups remaining in South America. Culturally as well as ecologically, the Gran Chaco is a transitional zone between the tropical plains of the Amazon Basin and the Pampas of Argentina. Along its western border it was wide-open to influences from the Andean cultures, and in the east it abutted on a subtropical region inhabited by Tupí-Guaraní tribes. In this paper we present a synthesis of the principal findings of a long term study on the genetic structure of native populations of the Gran Chaco using an assortment of morphological (anthropometrics and dermatoglyphics) and molecular markers (mitochondrial haplogroups and HVR-I sequences, Y-chromosome markers, and nuclear STRs). In general, the biological evidence demonstrates that the Gran Chaco tribes present high genetic diversity and low differentiation among populations, when compared to other regions of South America. The only exception is the Ayoreo, a population with unique genetic and morphological patterns, being an outlier not only in relation to the rest of the Gran Chaco populations but also to any other native group of South America.