Existing lake cores in close proximity to paleoanthropological sites are typically restricted to the Holocene (e.g., Johnson & Odada 1996) but other cores in the Levant and Africa range from over 100 ka to 1 Ma (Koeberl et al. Similar to the study of marine cores, an extensive arsenal of analytical methods have been applied to the study of lake cores, which serve as long, continuous archives of terrestrial climate change at annual to decadal scale for individual basins or watersheds. C 4 plants) at hominin sites in South Africa, Europe, the Levant, and Asia (e.g., Wang et al. Carbon and oxygen isotopic analysis as well as relative growth band thickness of speleothems have provided proxy data for local temperature, rainfall, aridity, and overlying vegetation ( C 3 vs.
Speleothems found in caves are also a rich archive of local paleoclimate information and, combined with uranium-thorium dating, can provide high-resolution records back to 500,000 years ago. For example, the variation in thickness and grain size in Chinese loess deposits are related to extensive periods of cold, dry, winter Asian monsoon winds stretching back over the last 7 million years (An 2000). There are a variety of other important high-resolution paleoclimate records relevant to hominin evolutionary history, but these are temporally or spatially restricted compared to marine cores. Documenting a much longer timescale, marine sediment cores have been collected across the globe, and composite records have been compiled that extend beyond the Cenozoic, thus covering the entire duration of the Primate fossil record (Zachos et al. Thus, these records are relevant to the later members of the genus Homo, such as H. 2002), while those from Antarctica extend back to ~800,000 years ago (Lambert et al. Continuous ice cores from Greenland record back to over 100,000 years ago (Bender et al. Eolian dust preserved in both marine sediment and ice cores has been correlated with climate and environmental conditions in the dust's source region, specifically as a proxy for aridity. Carbon isotope ratios of shells in marine cores are equally valuable for estimates of water circulation and atmospheric CO 2 concentrations. Air bubbles trapped in ice cores also provide a direct record of the past chemical composition of the atmosphere, particularly CO 2.
For example, the record of oxygen and hydrogen isotope ratios preserved in glacial ice, and oxygen isotope ratios in the shells of marine organisms such as foraminifera and radiolaria, provide a record of past sea levels, ice volume, seawater temperature and global atmospheric temperature (Figures 1 & 2). These long-term and relatively continuous natural archives are often used as references for comparison with local terrestrial-based paleoenvironmental reconstructions.
Proxy records from marine sediment and ice cores provide the basis for much of our understanding of past climate. To reconstruct climate over longer time-scales, scientists indirectly measure these components by analyzing various proxies, or indicators, that are sensitive to climatic or environmental parameters and preserved in the geological record. While it is ultimately local-level environmental processes acting upon individual populations that is one of the driving forces of evolutionary change, such shifts are often framed within the context of much larger regional or global climatic trends.ĭirect measurements of climate components such as temperature and precipitation only exist for the last century or two. Although various hypotheses and models have been proposed, refined, and/or abandoned for at least a century, the concept of environmental determinism and hominin evolution is still a hot topic today. The idea that critical junctures in human evolution and behavioral development may have been shaped by environmental factors has been around since Darwin.