by Andrew S. Cohen, J. Ramón Arrowsmith, Asfawossen Asrat, Anna Kay Behrensmeyer, Christopher J. Campisano, Craig Stratton Feibel, Roy A. Johnson, John Kingston, Henry F. Lamb, Daniel Ochieng Olago, Richard Bernhart (Bernie) Owen, Robin W. Renaut, Frank Schäbitz, Martin H. Trauth

Understanding the temporal and causal relationship between climate and human evolution is an enduring scientific challenge. Past attempts to understand this relationship have focused on outcrops containing hominin fossils and artifacts, or by using ocean and lake core records to help interpret the hominin fossil record. However, outcrop records are discontinuous and weathered, and deep sea cores integrate environmental histories over vast areas and are far from the hominin fossils. We propose a new approach, combining the advantages of obtaining drill core records of lake deposits close in age and location to hominin localities with the easier logistics of targeting shallow depth paleolake deposits on land, accessible by a truck-mounted drill rig. Drill cores from lakes have yielded exceptionally well-resolved records of climate change, and the approach we propose in HSPDP is strongly informed by the experience and results of deep lake drilling for collecting high-resolution paleoclimate records. Similar records can be collected from lake beds now on-land. Through an anthropology-geoscience community collaboration, the HSPDP Steering Committee has identified several high-priority basins in East Africa, where world-class paleoanthropological sites are situated near thick and highly resolved lacustrine deposits. Our goals are to: 1) collect continuous and long paleolake cores from basins spanning critical intervals in human evolutionary history, which are close to hominin fossil and archaeological sites of global significance. 2) assemble high-resolution (decadal to centennial scale) and readily datable paleoclimate/paleoenvironmental records from these cores covering much of the past ~4 Ma of East African environmental history. 3) evaluate models of climatic and tectonic forcing of environmental processes as they affect landscape resources, and 4) test hypotheses linking climate change and variability to physical and cultural evolutionary adaptations. Following extensive site and logistical surveys of potential drilling areas and broad scientific community input, the HSPDP Steering Committee has identified five high-priority drilling targets: 1. Northern Awash River Valley, Northern Ethiopia (Middle Pliocene) 2. Tugen Hills, Central Kenya (Late Pliocene) 3. West side of Lake Turkana, Northern Kenya (Latest Pliocene-Early Pleistocene) 4. Lake Magadi, Southern Kenya (Mid-Late Pleistocene), 5. Chew Bahir, Southern Ethiopia (Mid-Late Pleistocene. HSPDP is planned as an integrated, community effort with overarching scientific goals uniting these drilling sites. An extensive program of palaoeclimate and paleoecological reconstruction from the drill cores will broadly transform our understanding of the context of hominin evolution in Africa and will provide training and educational opporutnities in the host countries for years to come.

• We will address a range of current hypotheses concerning the influence of paleoclimate change and variability on hominin physical and cultural evolution, diversification and extinction (e.g. turnover pulse and variability selection). Many prominent theories concerning environmental constraints on hominin evolution were stimulated by evidence from these study areas To transform our understanding of the paleoclimate/evolution relationship we need to:
• Collect highly resolved precipitation and temperature records at the basinal scale for comparison with the marine sea surface temperature (SST) and terrestrial dust records.
• Collect records that capture variability in precipitation seasonality at the basinal scale.
• Capture the ecosystem response (vegetation, fire, faunal turnover, etc.) to this climate variability Quantitatively model tectonic/climate drivers and landscape response relationships, to insure our paleoclimate inferences drawn from basinal and regional scale data are consistent with climatic boundary conditions, and understand their regional evolutionary implications. Prior coring in Africa shows that lacustrine records are well suited to address these requirements. Collectively, the areas we have selected as drilling sites target lakebeds close to some of the most important fossil hominin and artifact sites in the world. All of the paleolakes we propose to drill contain long, continuous lake deposit records of climate change, and most have demonstrated sensitivity to climatic forcing from the orbital scale down to decadal or even shorter time intervals. Interregional and intertemporal comparative studies combining our sites with other drill core records in the region will generate paleoenvironmental data for interpreting a series of repeated and comparable historical experiments in hominin evolution.

African Rift, Climate Dynamics, East Africa, Ethiopia, Global Environment, Hominin Evolution, HSPDP, ICDP-2010/04, Kenya, MAGADI, Paleoclimate

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