With National Science Foundation support, Drs. Jelmer Eerkens and Eric Bartelink will examine how prehistoric populations in Central California responded to environmental change and population growth. The research will reconstruct ancient human health, diet, weaning practices, and mobility patterns using stable isotope and paleopathological analyses of human burials from the Sacramento-San Joaquin Delta region. The project is a collaboration between faculty members, and graduate and undergraduate students from two institutions, representing specialties in bioarchaeology, archaeology, archaeometry, stable isotope ecology, and geochemistry. Central California is an area of significant interest because the region experienced exponential population growth during the late Holocene (~3500 years before present until Spanish contact in the 1700s). The central issue focuses on the rate of demographic change, and uses multiple lines of evidence to explore whether population growth was stable or if it fluctuated in concert with environmental changes (e.g., extended periods of drought reported in climatic records). In this respect, the research will examine how ancient human populations responded to climatic change and social stress such as warfare.
Human skeletons provide a unique window into the past because they represent the life history of particular individuals. The study will merge those individual life histories into a broader picture of cultural adaptation to population growth, climatic fluctuations, nutritional stress, warfare, and disease. Based on existing anthropological theory, the researchers expect to find three patterns. First, they expect an increase in nutritional stress and disease indicators over time, reflecting greater consumption of poorer quality diets, especially during periods of environmental stress such as regional drought. Stable isotope analysis of human bone and teeth will provide information regarding the source of dietary protein, carbohydrates, and fats acquired from different ecosystems (terrestrial, freshwater, and marine), which will be compared with skeletal and dental indicators of stress and disease. Second, the researchers expect that periods of increased social and environmental stress will correlate with decreased parental investment in offspring, as measured by earlier weaning of children and poorer childhood diet. This will be evaluated using stable isotope signatures in serial sections of first molar tooth dentin, which forms in infancy and early childhood. Third, the researchers expect decreased residential mobility with increasing population growth, evaluated using strontium and oxygen isotope analysis of early forming teeth vs. later forming bone. To provide temporal control a large number of radiocarbon dates will be obtained.
The broader impact of this research will provide a unique dataset documenting hunter-gatherer transitions in prehistory. The study will shed light on how changes in climate influenced health, diet, weaning, and mobility patterns. In addition, Drs. Eerkens and Bartelink have worked closely with members of the Native American community to ensure that the results of this research are widely disseminated, including to the public and research communities. The research will contribute toward educating and training archaeology and physical anthropology students, and the research will be presented in both scientific and public forums, including national and regional conferences, lecture series, and museum exhibits.
