This proposal seeks funding towards costs of geophysical survey and scientific drilling of Pleistocene lacustrine sediments in East Africa, and their subsequent analyses. The aim of the project is to provide a long, continuous and highly-resolved palaeoenvironmental record that will facilitate tests of hypotheses linking human physical and cultural evolution to environmental variation, by reconstructing climatic and landscape change across critical intervals of the last half-million years of human evolutionary history.
The planned research is focused on Chew Bahir, a 5 km-deep sediment-filled rift basin in south Ethiopia, close to the important hominin fossil sites at Konso, Omo-Kibish, and east Turkana. Drilling will take place in November-December 2013, to a depth of 400 m, estimated to cover the last 500,000 years. Luminescence, radiocarbon, tephrochronology, palaeomagnetic, and 40Ar/39Ar dating methods will be used to determine the age range and time resolution of the cores. A multi-proxy approach, using sediment geochemistry, biomarker, isotope, pollen and diatoms, will be applied to reconstruct past changes in moisture balance, temperature and catchment vegetation. Statistical techniques will be used to define the most significant climate shifts and periods of maximum variability, and then used to model the natural selection of human populations, measured from regional densities of archaeological sites. Particular focus will be on the time period 135-125 ka in order to test the hypothesis that human range expansion out of Africa took place after a period of strong climatic variability.
The Chew Bahir project is part of the larger Hominin Sites and Paleolakes Drilling Project (HSPDP), supported by the International Continental Drilling Project (ICDP), by NSF (USA), and by DFG (Germany). The HSPDP involves deep drilling of lacustrine sediments at five globally-significant early hominin sites in Kenya and Ethiopia, including Chew Bahir. The combined core data from all five sites will allow comparison of 4 million years of environmental change with the record of human and mammalian evolution, extinction, cultural innovation, and geographic dispersal. The data will be used to evaluate models of climatic and tectonic forcing of environmental processes and landscape resources, and will facilitate testing of hypotheses linking climate variability to human origins, evolution, population change, extinction, and dispersal from Africa into Eurasia.
We have obtained a large amount of stratigraphic data for a variety of paleoclimate indicators through nearly 300 m of core record. We now know, from OSL and Ar-Ar dating that the record spans the last 500,000 years, thus covering the time range of Homo sapiens origin and dispersal. Work continues to interpret the data in terms of past climate chnages and their potential influence on human origins.