fossil density from different time periods and regions; the inconsistent collection of all components of available fossil assemblages (e.g., invertebrates, vascular plants and algae, as well as vertebrates), which have potential to offer critical tests of the climate evolution relationship; as well as by stratigraphic and geochronologic limitations. Concerted international efforts to substantially enhance the fossil hominin, archaeological, and other faunal records of evolution are necessary to establish with statistical reliability the precise first and last appearances of species, adaptations, and behaviors within particular geographic regions and strata. Precise determinations of the timing of evolutionary events are essential for more rigorous analyses of the climate-evouliton relationship.

At present there are few continuous quantitative paleoenvironmental records situated close to hominin fossil localities. By bringing the evidence of climate change and evolutionary events into close proximity, particularly by collecting high-resolution environmental records at or near the hominin fossil sites, it will be possible to test the extent to which those evolutionary events reflect responses to regional or local climate. In addition to the high-precision records of climate change that are required from long stratigraphic sequences located close to hominin sites, lake and ocean drilling records will be needed to integrate local climate records from hominin sedimentary basins with regional and global records.

Understanding past climates depends on a range of data that can be used to quantitatively reconstruct the range of climatic variables—temperature, precipitation, seasonality, vegetation and land cover, paleoaltitude, etc. It is important that new tools for quantitative reconstruction of past environmental conditions continue to be developed and applied to new and existing stratigraphic records. A key requirement for each of these elements will be formalized research funding to encourage scientific exchange and strategic analysis of climate evolution hypotheses by earth scientists, paleoanthropologists, and faunal researchers.

Theme II: Integrating Climate Modeling, Environmental Records, and Biotic Responses

This research theme describes research strategies to define the physical and biotic mechanisms whereby past environmental changes may have produced evolutionary (and behavioral) responses in fossil hominins. The approach will require developments in climate model and paleoecologic data integration. The aim of this effort is to use the new data collected under Theme I to constrain climate model simulations to explore the physical mechanisms and regionality of past climate changes. Existing environmental records are too sparse to draw firm conclusions about particular geographic patterns of climate in Africa and Eurasia and their variability, or about climate conditions along pathways to southern Eurasia, or temporal and spatial variability of Eurasian climates. In parallel with the efforts to collect additional environmental records proposed in Theme I, there is also a need for a program to integrate regionally resolved climate models with

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