Improved Dating of Archaeological Materials with Coordinated Stable Isotope Studies

Berkeley Geochronology Center, Berkeley CA

Investigators

Abstract

Determining the ages of archaeological sites is essential for assessing the timing and rates of human behavioral and biological evolution, and for synchronizing archaeological, fossil, and paleoenvironmental records across sites. Current techniques for dating archaeological sites do not fully meet these needs, especially at sites older than 50 thousand years. This project will develop 1) a new approach for determining ages and apply it to several important Middle Stone Age archaeological sites, and 2) a technique that uses archaeological materials to provide paleoenvironmental reconstructions for these sites during human occupation. The project will enhance the infrastructure for archaeological research across existing laboratories, allowing more informative study of museum collections that may contain unique or irreplaceable artifacts. The investigators will promote teaching, training and learning by engaging undergraduate science majors, technicians conducting the research, and a female PhD candidate who is a first-generation college attendee, in novel analytical protocols and approaches to data interpretation. The project will also support international collaborations, research, and science outreach, at sites that include a UNESCO-World Heritage Center. The archaeological record of the Middle Stone Age (300 thousand to 30 thousand years ago) is critical for understanding the biological and behavioral origins of our species, Homo sapiens. It encompasses the earliest known fossils of anatomically modern humans, provides abundant evidence for accelerated behavioral innovation relative to prior intervals, and coincides with the expansion of modern humans out of Africa. In this project, stable isotope and uranium-thorium dating of ostrich eggshells will be applied at sites in eastern and southern Africa that record the Middle Stone Age. The project will develop and apply uranium-thorium dating of ostrich eggshells, a common material in Old World archaeological sequences, and will employ stable isotopes of carbon, nitrogen, and oxygen in ostrich eggshell to provide improved local records of past mean annual precipitation, vegetation, and aridity. In sum, these dual methods will enhance archaeologists' ability to extract chronological and paleoenvironmental information from many Old World archaeological sequences and will advance understanding of the timing, tempo, and driving factors of Middle Stone Age behavioral and cultural innovations.