Potential distributions of pre-Columbian people in Tropical Andean landscapes.

Much has yet to be learned of the spatial patterning of pre-Columbian people across the Tropical Andes. Using compiled archaeological data and a suite of environmental variables, we generate an ensemble species distribution model (SDM) that incorporates general additive models, random forest models and Maxent models to reconstruct spatial patterns of pre-Columbian people that inhabited the Tropical Andes east of the continental divide, within the modern countries of Bolivia, Peru and Ecuador. Within this region, here referred to as the eastern Andean flank, elevation, mean annual cloud frequency, distance to rivers and precipitation of the driest quarter are the environmental variables most closely related to human occupancy. Our model indicates that 11.04% of our study area (65 368 km2) was likely occupied by pre-Columbian people. Our model shows that 30 of 351 forest inventory plots, which are used to generate ecological understanding of Andean ecosystems, were likely occupied in the pre-Columbian period. In previously occupied sites, successional trajectories may still be shaping forest dynamics, and those forests may still be recovering from the ecological legacy of pre-Columbian impacts. Our ensemble SDM links palaeo- and neo-ecology and can also be used to guide both future archaeological and ecological studies. This article is part of the theme issue 'Tropical forests in the deep human past'.

Genetic assessment reveals no population substructure and divergent regional and sex-specific histories in the Chachapoyas from northeast Peru.

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.

2,100 years of human adaptation to climate change in the High Andes.

Humid montane forests are challenging environments for human habitation. We used high-resolution fossil pollen, charcoal, diatom and sediment chemistry data from the iconic archaeological setting of Laguna de los Condores, Peru to reconstruct changing land uses and climates in a forested Andean valley. Forest clearance and maize cultivation were initiated during periods of drought, with periods of forest recovery occurring during wetter conditions. Between AD 800 and 1000 forest regrowth was evident, but this trend was reversed between AD 1000 and 1200 as drier conditions coincided with renewed land clearance, the establishment of a permanent village and the use of cliffs overlooking the lake as a burial site. By AD 1230 forests had regrown in the valley and maize cultivation was greatly reduced. An elevational transect investigating regional patterns showed a parallel, but earlier, history of reduced maize cultivation and forest regeneration at mid-elevation. However, a lowland site showed continuous maize agriculture until European conquest but very little subsequent change in forest cover. Divergent, climate-sensitive landscape histories do not support categorical assessments that forest regrowth and peak carbon sequestration coincided with European arrival.

Exploring imperial expansion using an isotopic analysis of paleodietary and paleomobility indicators in Chachapoyas, Peru.

OBJECTIVES: Inca imperial strategies of political and territorial expansion varied across conquered regions depending on local ecology and cultural resistance, and Chachapoya peoples in Peru's forested northeastern Andes were renowned for their rebellions against the invaders. The cliff tombs of Los Pinchudos (AD 1470-1535) present opportunities to use stable isotopes to: (1) explore dietary and mobility patterns from a mortuary community interred at a site attributed to the poorly-known Chachapoya culture during the period of Inca domination, and (2) explore the origins of the individuals as either local or foreign (Inca). Using biochemical tracers, we can help resolve the impact of foreign influence and changes in population and social structure during imperial occupation. MATERIALS AND METHODS: While it is difficult to reconstruct individual life histories from incomplete skeletons, stable isotopic analysis of multiple skeletal tissues provides a direct means of characterizing diet and residential mobility. Values of stable carbon (δ13 C), nitrogen (δ15 N), and oxygen isotope (δ18 O) ratios were determined in bone and dentine collagen and bone and enamel carbonate from 28 samples (11 paired tissues) from males, females, and juveniles from Los Pinchudos. RESULTS: Dietary signatures are consistent with a mixed but more C3 -based plant and protein-based diet with moderate proportions of terrestrial animals. Oxygen isotopic values demonstrate limited variation between paired tissues, with a few possible nonlocal individuals buried in one particular tomb at the site. Compared to other Andean areas that underwent imperial domination, these data do not demonstrate expected dietary shifts. DISCUSSION: These are the first isotopic data from a Chachapoya site and our research shows evidence for minimal non-local presence in this commingled burial assemblage. The regional diet reconstructed at Los Pinchudos (2850 masl) focused on resources of higher altitude tuber crops, beans, and grains (C3 ) and terrestrial protein rather than on lower elevation grasses such as maize (C4 ) as in other highland Andean regions under Inca control. During imperial domination, inhabitants of this region appropriated Inca materials goods but continued to construct tombs in the local manner even though a potentially diverse population was occupying them.