Australian Megafauna

Australian megafauna are a number of large animal species in Australia, often defined as species with body mass estimates of greater than 30 kilograms, or equal to or greater than 30% greater body mass than their closest living relatives. Many of these species became extinct during the Pleistocene (16,100±100 - 50,000 years before present).

The cause of the extinction is an active, contentious and factionalised field of research where politics and ideology often takes precedence over scientific evidence. It is hypothesised that with the arrival of humans (around 48,000-60,000 years ago), hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna. Increased aridity during peak glaciation (about 18,000 years ago) may have also contributed to the extinction of the megafauna. Some proponents claim a change in the climate alone caused extinction of the megafauna, but these arguments have to account for the fact that megafaunal species comfortably survived two million years of climatic oscillations, including a number of arid glacial periods, before their sudden extinction.

New evidence based on accurate optically stimulated luminescence and uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction of megafauna in Australia. The dates derived show that all forms of megafauna on the Australian mainland became extinct in the same rapid timeframe — approximately 46,000 years ago — the period of time in which humans first arrived in Australia. Analysis of oxygen and carbon isotopes from teeth of megafauna indicate the regional climates at the time of extinction were similar to arid regional climates of today, and that the megafauna were well adapted to arid climates. The dates derived have been interpreted as suggesting that the main mechanism for extinction was human burning of a landscape that was then much less fire-adapted; oxygen and carbon isotopes of teeth indicate sudden, drastic, non-climate-related changes in vegetation and in the diet of surviving marsupial species. However, humans appear to have rapidly eliminated the megafauna of Tasmania about 41,000 years ago (following formation of a land bridge to Australia about 43,000 years ago as ice age sea levels declined) without using fire to modify the environment there, implying that at least in this case hunting was the most important factor. It has also been suggested that the vegetational changes that occurred on the mainland were a consequence, rather than a cause, of the elimination of the megafauna. This idea is supported by sediment cores from Lynch’s Crater in Queensland, which indicate that fire increased in the local ecosystem about a century after the disappearance of megafaunal browsers, leading to a subsequent transition to fire-tolerant sclerophyll vegetation

There are similarities between prehistoric Australian megafauna and some mythical creatures from the aboriginal dreamtime (Mackness 2009).