Evidence for an early Plio-Pleistocene rainforest expansion in East Africa

Abstract

The Plio-Pleistocene palaeoenvironmental history of the Turkana Basin and neighbouring areas in north Kenya and southern Ethiopia has been a matter of considerable interest due to the important palaeoanthropological, palaeoarchaeological and palaeontological discoveries that have been made in this region1–3. The consensus is that although environmental oscillations have certainly occurred over the past 4 Myr, Plio-Pleistocene environments were generally comparable to the modern environment of the area4. However, the recent recovery of two taxa presently characteristic of the central African rainforest—the anacardiacean tree Antrocaryon and the prosobranch gastropod Potadoma—from a restricted chronostratigraphic horizon dating at ∼3.3–3.4 Myr, at widely separated sites in the Turkana region, suggests that the general pattern of environmental stability was punctuated at this time by a brief but significant rainforest extension in East Africa. This brief humid interval apparently coincides with certain important molluscan immigrations, and can be broadly correlated with the first major episode of climatic deterioration in the Northern Hemisphere.