Fecal stanol ratios indicate shifts in camelid pastoralism in the highlands of Peru across a 4,000-year lacustrine sequence

Abstract

Subsistence adaptations respond to environmental instability as well as sociopolitical demands. On the Andean altiplano, camelid husbandry is a key adaptation utilized for thousands of years to mitigate environmental risks to agricultural productivity, to facilitate transport and to generate wealth for political purposes. Here, we reconstruct the history of camelid utilization on the altiplano with fecal stanol biomarkers from Lake Orurillo in southern Peru. Biomarker samples span a 4000-year interval and document changes at centennial timescales. The abundances of individual fecal stanols appear to be less diagnostic of changes in human occupation in the Orurillo region where human population levels apparently remained far lower than those of domesticated camelids. However, ratios of human (coprostanol) to ruminant (24-ethylcoprosanol) fecal stanol concentrations demonstrate that these proxies are reliable indicators of variations in camelid herd sizes. Our data show that camelid utilization intensified after ca. 1050 CE during a severe and protracted drought that was coincident with widespread population movement away from fertile farmlands to higher elevations favorable for grazing. Camelid herds remained in high abundance around Orurillo during improved climate conditions and through the Inca era until after ca. 1500 CE when our data point to a significant disruption after European conquest. The intensification of camelid husbandry among Andean cultures is therefore linked to major environmental and sociopolitical shifts.