Did Hunting or Climate Change Cause a Late Holocene Bottleneck in California Tule Elk? An Integrated Test using Ancient DNA and Stable Isotopes

University Of Utah, Salt Lake City UT

Investigators

Abstract

Recent research has suggested that prehistoric hunters may have caused declines in the populations of prey species such antelope, deer, and elk over the last 3000 in many areas of western North America. This work has shown that the implications of these declines are far-reaching and range from changes in human behavior and biology involving increasing violence and declining human health, to modern wildlife management. Standard archaeological indicators of prey population declines - such as declining abundances of the bones of large game - are, however, imperfect and cannot distinguish between broad-scale prey population declines versus local movements of prey away from human settlements. In addition, it is hard to evaluate the effect of climate change on prey declines, because of the difficulty in aligning time series of archaeological bone abundance data with those from various records of climate change. One needs a more robust methodology - one that informs more directly about specific causes including climate change. This research develop and test such a methodology using both ancient DNA (aDNA) and stable isotopes derived from the bones of elk (Cervus elaphus), the largest and most economically attractive terrestrial animal on the California landscape. The project builds on a previous pilot study with tule elk and uses patterns of genetic variation derived from ancient mitochondrial DNA (mtDNA), and stable isotopes, to test the hypothesis that prehistoric hunters caused a population decline in this animal. Trends in genetic variation are used to reconstruct the tule elk population history since population declines leave a signature in genetic variation. The stable isotopes of carbon, oxygen, and nitrogen recovered from faunal bone register aspects of an animal's forage and can be used to reconstruct terrestrial climate change. The work will analyze ancient mtDNA and stable isotopes from the bones of 113 tule elk individuals from two archaeological sites in central California where elk remains are abundant. All specimens that produce aDNA sequences and stable isotope values will be radiocarbon dated to provide chronological control. The analysis not only represents a novel integration of aDNA and stable isotope methodologies to reconstruct and evaluate the prehistoric population trends of a key subsistence resource to the aboriginal people of the region, but can be a model for exploring the role of human and climatic influences on animals in other archaeological settings. The project has implications for the methodology of reconstructing trends in the populations sizes of ancient animals, key issues in the human prehistory and historical ecology of California, as well as current issues in tule elk conservation and management. The project will also continue the career development of a post-doctoral student who has conducted the aDNA work in the pilot study and support and train a graduate student research assistant in stable isotope analysis. Finally, the project will provide a key stimulus to a new Molecular Zooarchaeology research program devoted to understanding the population histories of other animal species in North America. The proposed project and developing research program integrates the research expertise of four faculty members of the Department of Anthropology, University of Utah, and will enhance both undergraduate teaching and graduate level training and research opportunities.