Doctoral Dissertation Improvement Grant: Carbon and Nitrogen Isotope Signatures Recorded in Animals - Geographic and Paleoenvironmental Proxies in the Southern Levant

Harvard University, Cambridge MA

Investigators

Abstract

The ability to tract animal origins and movement is an important piece of archaeological interpretation. An integrative model will be tested for its ability to predict the climatic and phytogeographic origins of herbivores in the southern Levant based on carbon and nitrogen isotopic values. While a number of studies show that the natural abundance of carbon and nitrogen isotopes in plants is inversely correlated with precipitation, the distribution of these isotopic values through the southern Levant requires a more thorough investigation. Furthermore, other studies demonstrate that carbon and nitrogen isotopic values in herbivores are largely inherited, if offset, from ingested plant material. These observations suggest that the carbon and nitrogen isotopic abundances in plant tissues, later transferred to herbivorous animals, can be used to determine the spatial origins of herbivores and to track climatic changes through time on a local scale. The assumptions will be tested in the current research through intensive sampling of goats and pasture from organic farms and plants from different points along a precipitation gradient and different phytogeographic belts in the southern Levant. The model will then be applied to a case study that aims to determine the contribution of pilgrimage to Jerusalem's economy during the Early Roman Period as reflected by the isotopic composition of animals that were brought to the city. The intellectual merit of this project lies predominantly in the unique integration of climatic data and the stable carbon and nitrogen isotope values of plants and herbivores into a single predictive model. This integration will enable the determination of an animal's geographic origin and track climatic change. While a wealth of studies have demonstrated the relationship between water availability and heavy carbon and nitrogen isotope enrichment in plants, this study will contribute by testing whether these two isotopes co-vary along a precipitation gradient. In addition, many studies have demonstrated an inverse correlation between nitrogen isotopes and precipitation in different animals but it is unclear whether there is a direct correlation between plant and herbivore composition. The proposed project will address this ambiguity by testing the degree of heavy nitrogen isotope enrichment between herbivores and their diets along two precipitation gradients in Israel. Finally, although the proposed model is ecologically based, it will enable the investigation of a wide range of archaeological questions dealing with mobility patterns, geographically related economic processes and climatic change within the limits of the organic preservation of bone collagen from herbivore remains.