Paleoclimate Research and Human Evolutionary Studies

Gail M. Ashley¹, Andrew S. Cohen², and Craig S. Feibel^1
1Earth and Planetary Sciences, Rutgers University, Piscataway, NJ
²Geosciences, University of Arizona, Tucson, AZ

Hominin fossil discoveries as old as 6 Ma and advances in DNA research indicate that humans evolved in Africa and then began to migrated to other parts of the world (~1.8 Ma). Evidence of climate change found in deep sea stratigraphic records and more recently in continental basins of tropical Africa provide the context for interpreting the environmental history of hominins associated with physical and adaptive evolution and species diversification. Key forcing factors for evolution might have included the general aridification of Africa and the increasing variability of climate driven by processes on time scales ranging from Milankovich insolation forcing (20 to 100 m.y.) to millennial-scale events. Climatic variability in turn, would have affected food and water resource availability, along with overall habitat character and have direct implications for cultural and biological evolution.

Paleoclimate records consist of multiple indicator records, such as biological remains (pollen, phytoliths, diatoms), geochemical fingerprints (isotopes, leaf wax, major, TEX86), sedimentary facies, and bulk lithological records (paleosols and stromatolites) and are obtained from outcrop and drill core. Outcrop records such as Olduvai Gorge and Koobi Fora may reflect actual hominin habitats, but tend to be discontinuous in both time and space. In contrast, drill core records from continental lake basins, such as Lakes Malawi and Bosumtwi are more likely to be continuous. But, they may also be far from where hominins were living making the link to the environmental forcing evolution and species diversification more tenuous. There are fundamental challenges for interpreting these varied multiple indicators because uncertainties exist, specifically the continuity and duration of records, their temporal and spatial resolution and most importantly, numerical dating resolution.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas