Doiron, K.E., Colcord, D.E., Shilling, A.M., Njau, J.K., Stanistreet, I.G., Stollhofen, H., Schick, K.D., Toth, N.P. and Brassell, S.C., 2026
Fossil and archaeological records confirm that the lacustrine setting of Olduvai Gorge was a sustained habitat for hominins in the early Pleistocene. Sediments deposited in Paleolake Olduvai spanning forty thousand years record evidence of climatic and environmental changes and episodes of ecological stability in the landscapes occupied by hominins. Isotopic signatures diagnostic of plant waxes document consistency in savanna vegetation during a succession of wet/dry climate cycles, whereas those associated with aquatic biota attest to increased lake alkalinity during drier intervals. Hominins would have experienced a stable terrestrial ecosystem with a consistent mix of woodland and grassland, while water resources were affected by pronounced temporal variations in the hydrological cycle regulating the size and chemistry of Paleolake Olduvai.
Researchers report responses to wet and dry climate cycles in eastern Africa in the Pleistocene, in both terrestrial and aquatic environments. Studying this paleoclimate provides insight into the climate, and changes in climate, experienced by early hominins. Simon C. Brassell, Kelsey E. Doiron, and colleagues analyzed carbon isotopes in a sediment core from the Olduvai Gorge in Africa. The sediment core, from the bed of the paleolake Olduvai, covers a period between 1.9 and 1.8 million years ago. Carbon isotope values from plant waxes remained consistent over the study period, suggesting stability in the type of vegetation on the surrounding savanna, despite multiple wet and dry cycles. Isotopes of molecules derived from aquatic macrophytes and from algae in the lake, however, show changes during dry periods consistent with a shift toward utilizing bicarbonate as a carbon source. This suggests that the lake experienced chemical changes during dry periods, becoming increasingly alkaline. The isotopic evidence also shows that the source of organic matter to the lake varied between terrestrial and aquatic organic matter with wet and dry cycles. The results suggest that the terrestrial vegetation may not have experienced shifts between C3 and C4 vegetation, as previously suggested. According to the authors, while variations in climate primarily impacted biological and chemical cycles in the lake, the savanna vegetation around Olduvai may have remained a stable environment for early hominins.
The College of Arts