A 500,000-year environmental record from Chew Bahir, south Ethiopia: testing hypotheses of climate-driven human evolution, innovation, and dispersal

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.

Beneficiaries of this research will include: (1) a wide public audience with interest in human origins; (2) journalists, authors, museum curators, film producers, and teachers, all of whom will have a direct interest in communicating increased understanding of our species evolutionary history; (3) tourism and heritage business in Ethiopia, and related tourism agencies in the UK; (4) policy makers, especially in management of water and terrestrial resources under the extremes of future climate change.

Research on human origins commands an exceptionally wide range of public attention. Newspapers, magazines, TV and radio frequently report on the latest findings of human fossils, and discuss their significance in understanding our common ancestry. Yet there is still very little scientific understanding of why humans emerged from hominid lineages, and why modern humans spread 'Out of Africa' rather recently. This project, as well as being of direct benefit to a wide range of archaeological, palaeoanthropological and climate change researchers (see 'Academic Beneficiaries') is likely to generate considerable public interest, because it will give a much greater understanding of the environmental forces that have shaped our genetic legacy.

Visual and conceptual models of the impact on early human populations of past environmental crises, and human adaptations to strongly varying environments, arising from this project will attract wide attention of education and media sectors. The Smithsonian Museum' s Human Origins website already includes information about this project (http://humanorigins.si.edu/research/east-african-research/drilling), and will be updated during the coming months and years. We will publicise the project on our institutional websites, and provide material for museum websites in the UK, including the Natural History Museum, London, the Great North Museum at Newcastle, Oxford University Museum, and the National Museum of Wales, Cardiff.

The project results will also be of value to policymakers, relating to prediction of future changes in water resources, (including hydro-power), and agriculture (especially soil fertility and erosion). Scientists and policy makers will have access to publications resulting from the project, and to project data to be archived in the NERC and NOAA databases. The high-resolution climate reconstructions achieved by this project will feed directly into validation of computer-based climate models. Improvement of computer simulations through the validation exercise will provide more reliable future predictions for policy makers. The results will be of direct relevance to international commissions, such as IPCC assessment reports.