Our record of aridity over the last 4.4 Ma in the Turkana Basin was just published in PNAS (click here for paper). This record uses δ18O values of fossil teeth to reconstruct aridity at and near fossil hominin sites.
The punchline: there is no uni-directional trend in aridity at hominin sites for the past 4.4 million years; instead conditions in the Turkana Basin oscillated from being very dry (as dry as it is today) to wetter (similar to Nakuru today).
Although this result is consistent with many other datasets, it’s in contrast to long-held views of environmental change in the region.
This paper is the product of many many years of work. Scott did a tremendous job with this study; it has significant updates to the modern δ18O enamel – aridity relationships (replacing our 2006 paper), new δ18O data from the fossil record, and integration of the results with existing datasets on climate and environmental change in the region. It is chock-full of new data and analysis. It serves as the new reference for the δ18O-enamel based aridity index for both the modern calibration and fossil applications. Kudos to Scott!
Next step, build on this aridity record for hominin sites in eastern Africa using ∆17O records from teeth, soil carbonate, lake carbonate and anything else that will help us build records of water availability in past landscapes and ecosystems. Stay tuned.