New Stratigraphic and Archaeological Investigations on the Origin of the Acheulean at Olduvai Gorge

University Of Wisconsin-Milwaukee, Milwaukee WI

Investigators

Abstract

With National Science Foundation support, Dr. Lindsay McHenry and an international team of colleagues will conduct two field seasons of geological and archaeological research at Olduvai Gorge, Tanzania. The team brings together U.S., U.K., Spanish, and Tanzanian geologists and archaeologists to revisit classic fossil and stone tool sites in Olduvai Middle and Upper Bed II. This interval of time (~1.79 - 1.15 million years) at Olduvai preserves evidence for critical changes in early hominid and animal fossils, stone tools, and climate, including the disappearance of Homo habilis, the emergence of Homo erectus, the end of primitive Oldowan stone tools, and the first appearance of more advanced Acheulean tools. Unlike at many other African archaeological sites, many Olduvai artifacts are found in primary or near-primary context, providing additional information on hominid behavior. Little field research has been conducted on Middle and Upper Bed II since M.D. Leakey's original studies over 40 years ago. Despite the importance of Olduvai Bed II, the age and stratigraphic position of the excavated sites is poorly constrained. Estimates for the age of the top of Bed II range from 1.4 to 1.0 million years. This 400,000-year range makes it impossible to compare the Olduvai record chronologically with other potentially contemporaneous sites in Eastern Africa, and makes it difficult to incorporate the vast amount of archaeological data from Olduvai into regional studies of hominin evolution. To address this, this study will date volcanic ashes from Bed II using innovative 40Ar/39Ar radiometric methods. In addition to providing better dates for regional correlation this project will improve site-to-site correlation within Olduvai. This project will study volcanic ashes within the Olduvai sediments, determining unique compositional "fingerprints" for each ash and using these to identify individual ashes at different sites. By analyzing ashes above and below archaeological sites, this project will construct a new stratigraphic framework for Bed II. Using this high-resolution framework this project will test whether the "Developed Oldowan" archaeological sites clustered around the margins of ancient Olduvai lake coexisted with the more inland Early Acheulean. A renewed investigation of the artifacts using modern assemblage interpretations will help test whether these two assemblages actually represent unique industries, or whether they are adaptive responses to different ecological settings. The intellectual merit of this project is the establishment of a new, geochemically tested stratigraphic framework for Olduvai Bed II that can test and refine the relative ages of its archaeological sites. New dates will provide age control for this notoriously poorly dated interval, and relate the Olduvai record to regional records of climate and technological change. The re-examination of Bed II Developed Oldowan and Acheulean assemblages will combine field and laboratory work to provide a modern reappraisal of the sites where the Oldowan - early Acheulean sequence was originally defined. The broader impact of this study is that it will improve understanding of Olduvai's chronological and archaeological place in the records of human evolution, technological development, and climate change. This project will provide training for U.S., U.K., and Tanzanian students and will help improve the paleoanthropological facilities at the Tanzanian National History Museum.