Abstract
Many native populations in South America have been severely impacted by two relatively recent historical events, the Inca and the Spanish conquest. However decisive these disruptive events may have been, the populations and their gene pools have been shaped markedly also by the history prior to the conquests. This study focuses mainly on the Chachapoya peoples that inhabit the montane forests on the eastern slopes of the northern Peruvian Andes, but also includes three distinct neighboring populations (the Jívaro, the Huancas and the Cajamarca). By assessing mitochondrial, Y-chromosomal and autosomal diversity in the region, we explore questions that have emerged from archaeological and historical studies of the regional culture (s). These studies have shown, among others, that Chachapoyas was a crossroads for Coast-Andes-Amazon interactions since very early times. In this study, we examine the following questions: 1) was there pre-Hispanic genetic population substructure in the Chachapoyas sample? 2) did the Spanish conquest cause a more severe population decline on Chachapoyan males than on females? 3) can we detect different patterns of European gene flow in the Chachapoyas region? and, 4) did the demographic history in the Chachapoyas resemble the one from the Andean area? Despite cultural differences within the Chachapoyas region as shown by archaeological and ethnohistorical research, genetic markers show no significant evidence for past or current population substructure, although an Amazonian gene flow dynamic in the northern part of this territory is suggested. The data also indicates a bottleneck c. 25 generations ago that was more severe among males than females, as well as divergent population histories for populations in the Andean and Amazonian regions. In line with previous studies, we observe high genetic diversity in the Chachapoyas, despite the documented dramatic population declines. The diverse topography and great biodiversity of the northeastern Peruvian montane forests are potential contributing agents in shaping and maintaining the high genetic diversity in the Chachapoyas region.
Highlights
Chachapoya culture developed in a singular and biodiverse zone between the Andean mountain range and the Amazonian rainforests from northeastern Peru, and fluoresced around 900 CE (Common Era)
Previous genetic assessments have demonstrated that the Chachapoyas region today harbors, unlike many other regions inhabited by Native South Americans, high levels of genetic diversity [1, 2], and they have succeeded in placing Chachapoya populations on the genetic map of South America
To the extent of our statistical resolution, we did not detect population substructure in the Chachapoyas sample, which accounts for the notion that genetic subdivision does not necessarily accompany cultural differentiation
Summary
Chachapoya culture developed in a singular and biodiverse zone between the Andean mountain range and the Amazonian rainforests from northeastern Peru, and fluoresced around 900 CE (Common Era). Populations thrived in the area until conquered by the Incas (around 1475 CE) and Spaniards (first half of 16th Century). Since the Chachapoyas region has been an important area even before the Late intermediate Period (1000–1475 CE), it has been a target of various archaeological, ethnohistoric, and genetic studies. Several questions arising from the fields of archaeology and ethnohistory, remain to be explored with genetic data. These focus on the period of Inca and Spanish conquests in the 15th and 16th century and include a long-standing question regarding population substructure within Chachapoyas, as well as the sex-specific demographic impacts of the conquests. At a somewhat broader scale, we consider the issue of Chachapoyan affinities to human groups in the highland Andes and in lowland Amazonia
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