PALEO-CRITICAL ZONE ECOLOGY, ARCHIVES OF HOMININ HABITATS AND RESOURCES (Invited Presentation)

The concept of a Paleo Critical Zone (pCZ) capturing and archiving the total environment from the top of the canopy to the depth of rock weathering provides a power tool for improved understanding of the ancient habitats and resources used by hominins. pCZ is the thin skin of the Earth upon which life began, now thrives and it is the surface that hominins lived on, evolved and travelled short and long distances. In areas of aggradation, or landscape stability (i.e. non-erosion), CZs become pCZs and archive important records of all aspects of the paleo-environment. The key elements of hominin survival are air quality, water and food availability and safety, but finding fossil evidence of these presents challenges. Paleocritical zone studies, to date, have been on systems with large temporal and spatial scales and thus have yielded big picture analyses. To have relevance, to an individual hominin, paleoecological reconstructions need higher resolution, i.e., short time scales and small spatial scales. These “barefeet on the ground” factors relevant to individuals are recorded in the minerals, geochemistry, stable isotopes, and plant biomarker (leaf waxes) in sediments. Oxygen isotopes point to water sources and soil temperature. δD hydrogen isotopes provide a glimpse into the paleohydrology (water potability, water table depth, soil moisture, etc). Compound specific carbon-isotopic data for organic matter can identify presence of wetlands and edible aquatic plants (ferns, papyrus, nutsedge, algae, water lettuce, palms), indicate areas of dense woodland (with shade and safety), open bush land, or grassland. There are challenges awaiting pCZ ecological research, for example, to develop a proxie for records of protein-rich brain food (DHA fatty acids), that are known to be critical for primate brain development. The cross disciplinary research that has been so successful for Critical Zone studies is key to unlocking the records of hominin habitats in the pCZ.