THE DEVELOPMENT OF A HIGH RESOLUTION RAINFALL RECORD

Dr. Christopher Lepre of the Department of Earth and Planetary Sciences, Rutgers University (USA) will bring his geological and anthropological expertise to East Africa in order to study the impact of past climate on the evolution of the human lineage. The ancient monsoon and its effect on African ecosystems is thought to be responsible for a number of significant turning points in the evolution of early humans. Nevertheless, there is a lack of high-resolution and long-term information about the amount of rain that fell over East Africa during the interval between 4.0 and 1.0 million years ago. This has obscured understanding of how climate changes may have influenced early human anatomy, the development of stone tools, and dietary habits. To address this problem, the prehistoric rainfall of northwest Kenya will be reconstructed by using geological fieldwork and laboratory analyses of ancient soils. These ancient soils directly encase important fossils and archaeological sites that document the oldest stone tools in the world that are currently known, in addition to the evolutionary history of such species as Homo erectus and Homo habilis. Further objectives of the project are to train Kenyan professionals in laboratory research methods and develop a mobile teaching project through the Rutgers Geology Museum that provides schools in the United States and Kenya with hands-on opportunities for learning about fossils, archaeology, and geology.The research project will provide the scientific community with an advanced understanding of Earth's ancient climate and methods of reconstruction, highlight the importance of Kenya for interpreting the human past, and strengthen the collaborations between the National Museums of Kenya and the United States.The research of Dr. Lepre concentrates on the longstanding questions: Why was there such a diversity of human evolutionary events during the timeframe of 4.0-1.0 million years ago, and how did the environment contribute to these events? He will address these questions by analyzing the iron-bearing minerals preserved in ancient soils. Such minerals, like hematite and goethite, are formed under certain temperature conditions and specific quantities of yearly rainfall. Through assessing the ratio of hematite to goethite in ancient soils, past environmental changes due to climate can be reconstructed and compared with events of human evolution. Dr. Lepre's laboratory at Rutgers University is equipped with a spectrophotometer that can detect hematite and goethite in soil samples through measuring the diffuse reflectance of light. As these minerals contain iron, additional measurements of the magnetic properties of the samples will help elucidate the environmental conditions under which the ancient soils formed. Geologic fieldwork will be conducted at the Lake Turkana Basin, a geographically remote but world-renowned fossil and archaeological locality in northwest Kenya. This multidisciplinary research applies new methods towards the analysis of ancient soils of the Lake Turkana Basin in an attempt to answer old questions about the environment of human evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.