What can the data on late survival of Australian megafauna tell us about the cause of their extinction?

[Roberts et al. 2001a. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago. Science 292, 1888–1892] concluded that the extinction of Australia's late Pleistocene megafauna was an abrupt event that took place about 46 ka ago throughout the continent. By placing the extinctions soon after the arrival of people in Australia but before climate changes associated with the Last Glacial Maximum, this study implicated human impact as cause. However, the study was controversial because it excluded evidence, mainly from archaeological sites containing disarticulated megafauna remains, for survival of some megafauna well past 46 ka ago. Here, I ask how our interpretation of the extinctions would be changed if this evidence were accepted. Contrary to climate-change models of extinction, the young megafauna sites are not concentrated in mesic refuges around the coast. These sites do suggest that relatively small-bodied megafauna species were the last to disappear, as predicted by a version of the overkill hypothesis. More work is needed to test the evidence for late survival of megafauna species in Australia, but at present this evidence supports overkill, not climate change, as the cause of the extinctions.