Looking for the archaeological signature in Australian Megafaunal extinctions

Abstract

The decline and disappearance of a range of giant marsupials, reptiles and birds from the Australian landscape during the last Glacial cycle continues to capture the imagination of both researchers and the general public. The events hinted at in the Australian fossil sequences appear to be mirrored on other continents through similar time periods, though the exact cause or sequence of extinctions remains largely unresolved. In recent years debate over megafaunal extinctions in Australia has been dominated by reports that humans were the primary drivers, leading some to assert that it is no longer a question of whether humans drove these extinctions, only how. Following the review of Wroe and Field, new reports have been published that claim support for a human-driven extinction (HDE). On closer scrutiny however, the key sites and samples lack firm contextual data and/or clear provenance. These studies fail to prove a key tenet of the HDE - that all, or even most now-extinct species were present at the time of human colonization of the continent. As compared with the easy assertion 5 years ago that this had been established, there are now more faunal species (c. 69% of total known to have become extinct) that cannot be placed within 50-100 ka of human arrival. There are still only two sites that demonstrate a coexistence of humans with some species of megafauna - Nombe Rockshelter in the PNG highlands and Cuddie Springs in the semi-arid southeast of Australia. If there is so little empirical evidence for coexistence or association of megafauna with humans, then support for an HDE through overhunting and ecosystem disruption is seriously compromised. Furthermore, the popularly cited "extinction window", proposed as c. 51-39 ka when the HDE is argued to occur, is still only a theoretical construct. There is no clear evidence indicating that this period was particularly significant in terms of faunal loss. At present, the great majority of 'Pleistocene' sites remain poorly dated and the understanding of faunal turnover through this epoch is almost non-existent. Small datasets, poorly constructed hypotheses and assertive rhetoric are the prominent features of current discussions on a human role in megafaunal extinctions. Importantly, it is yet to be established whether the extinctions are an archaeological problem. The sparse fossil record known from Australia hampers a clear resolution as to how and when the megafauna disappeared, a situation likely to continue into the near future.