Microhistological analysis of ancient wild herbivore droppings from the Potrerillos valley, central western Argentina: Palaeodiets, vegetation and human activity

Abstract

The deposition of faeces, pellets or non-ingested remains resulting from the feeding activities of humans and animals has led to the considerable accumulation of remains, including bones, seeds, vegetative remains of plants and other tissues at archaeological and palaeontological sites worldwide. Using a microhistological technique, we examined the ancient droppings (palaeofaeces) of wild herbivores found at the Los Conitos archaeological site in the Valle de Potrerillos in the Andes of Argentina. Our method enabled us to identify the plant taxa eaten by herbivorous mammals that lived in the region during the late Holocene. The site yielded plant macro-remains of wild and domesticated plant taxa, including seeds, endocarps, leaves and stems which are associated with human occupation of the valley since at least ca. 2,300 bp. We found only wildplants in the palaeofaeces, and their frequency varied throughout the 2,000 years of the sequence. One of the key discoveries of this study was the detection of micro-remains of the trees Neltuma flexuosa (algarrobo) and Schinus sp., especially in archaeological contexts from before 1,000 bp. The lack of micro-remains from domesticated plants in the wild herbivore droppings allows various environmental possibilities to be considered. The scarcity of annual herbs grazed by wild herbivorescould indicate the continuous rather than only seasonal presence of this fauna in the area. This is relevant to the main prey, which the pre-Hispanic human communities hunted, Lama guanicoe, the guanaco. This investigation helps to reconstruct the landscape of the past from an archaeobotanical perspective, discussing interactions between plants, animals and humansand considering the recent deterioration of these plant communities, mainly from human activities. The main vegetation was scrub with shrubs from ten families together with some cacti and grasses.