tional evidence that will require more sophisticated tools. Significant progress into the question of whether past climate changes influenced human evolution will require a coordinated, focused, and cross-disciplinary research program designed specifically to address this problem.

Although we have a broad understanding of African and Eurasian climate history, this climate record generally lacks the temporal resolution and details of rainfall and temperature that potentially impacted how the hominins lived, and in particular does not adequately reflect differences in past climates between regions. Improved climate records for specific regions will be required before it is possible to evaluate how critical resources for hominins, especially water and vegetation, would have been distributed on the landscape during key intervals of hominin history.

The existing records of earth system history and hominin fossil history also contain substantial temporal gaps. A general understanding of the timing of major events in human evolution exists, but our ability to interpret what has driven these events remains limited by a paucity of fossil material, particularly over the most interesting periods of rapid evolutionary change. Major breakthroughs will almost certainly have to await discoveries of additional hominin fossils and associated archaeological materials. New hominin fossil discoveries should enable the more precise understanding of the ages of various events in the hominin evolutionary record that will be needed for robust correlation of climatic and evolutionary events. Similarly, a broad understanding of earth system history, and particularly past climate history, has been gleaned from other fossils found associated with hominin fossil discoveries and from analyses of lake and ocean sediment cores. This material provides a wealth of base information that can be used with the present generation of global climate models to understand paleoclimate characteristics and the factors that controlled past climates, particularly at continental and regional scales, but these are still limited for understanding the local climates that are so important for evaluating causative factors involved with hominin evolution.

This report proposes focused research initiatives that are designed, over a 10-20 year period, to dramatically improve our understanding of this research problem. These initiatives are presented in two major research themes.

Theme I: Determining the Impacts of Climate Change and Climate Variability on Human Evolution and Dispersal

Hypotheses linking climate change and hominin evolution are based on indications that large-scale shifts in climate or climate variability altered the landscape ecology which, in turn, presented specific adaptive or speciation pressures that led to genetic selection and innovation. However, efforts to test such hypotheses are fundamentally data-limited, constrained by gaps or poorly studied intervals in the fossil and archaeological record, coupled with the highly variable



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