Early Pleistocene hippopotamid extinctions, monsoonal climates, and river system histories in South and South West Asia: comment on Jablonski (2004) 'The hippo's tale: how the anatomy and physiology of Late Neogene Hexaprotodon shed light on Late Neogene

摘要

Jablonski (2004) has recently argued that because hippos are totally dependent upon permanent water, the record for hippopotamid extinction across southern Asia provides a proxy record for the intensification of the monsoon in the late Neogene. As she points out, the intensification of the Asian monsoon resulted in increased seasonality, and much greater contrasts than previously between wet summers and dry winters, because of which "wide-scale, months-long drought would have been devastating to ancient hippopotamus populations" (p. 122). Their progressive extinction across southern Asia in the Early Pleistocene thus records changes in seasonal patterns of river flow brought about by, in her opinion, the intensification of the monsoon. Before accepting her argument, we need to consider when the monsoon intensified in southern Asia, the extinction dates of hippopotamids (and other animals sharing the same habitats) in the late Neogene of southern Asia, and the histories of those river basins that provide relevant fossil evidence.