A recent discovery: Megafauna did not go extinct before the arrival of humans. They and humans once coexisted for a long period of time.
Abstract
It has been argued that globally the extinction of many species of megafauna appears to coincide with the dispersal of modern humans, however, with the refinement of age ranges on megafauna specimens it has been revealed that many extinctions are in fact time-transgressive. This appears to be the case in Europe and Asia, and probably also the Americas. The argument over what mechanism was responsible for megafauna extinction in Australia, however, remains heavily contested. This contribution investigates the age of a single articulated megafauna specimen of Zygomaturus trilobus from the Willandra Lakes. The Willandra is unique in that it is the only Australian landscape with evidence for a) continual occupation by Aboriginal people from 50,000 years ago and b) the presence of megafauna. As people have occupied the Willandra since the period of initial colonisation, establishing the age range of this specimen provides a good test to determine if people drove megafauna into extinction soon after their arrival, or whether megafauna and people co-existed for a long period of time. Two independent dating techniques show that the fossil has a maximum age range based on OSL of 33.3–36.7kya and a minimum age range based on U-series at 32.4 ± 0.5kya. This specimen represents the youngest example of extinct megafauna reliably dated in Australia. Regardless of whether one accepts a short (47.5kya) or long (55kya) chronology for Aboriginal occupation of Australia, it would now appear that the second largest marsupial to ever exist was still present for a considerable time after the first arrival of Aboriginal people.
Section snippets
Methods
The specimen: The articulated Zygomaturus trilobus fossil was found in 1980 at the site of Leaghur West 20 (LW 20) (Johnston and Clark, 1998, Clark, 1987) and it was subject to two separate rescue excavation efforts. The first partial excavation was undertaken by palaeontologist Jeanette Hope in 1981, who excavated the maxilla and sent the fossil in a block of sediment to the Australian Museum. The second excavation was carried out by National Park archaeologists Peter Clark and Harvey Johnston …
Results
Luminescence dating: Measured De ranged from 19 ± 1.8 to 71 ± 5 Gy (Fig. 3a). The central age model was used to identify the level of over-dispersion within the single grain dose distribution. This sample has an over-dispersion of 0.25. Over-dispersion is recognized as that spread in the data above that which would be expected based on just the measurement uncertainties of the individual single grain dose values. The most common cause of over-dispersion is partial bleaching, where only a…
Discussion
The timing of the arrival of people in Australia still remains a contentious topic, with recent suggestions that people may have entered Australia as early as 55kya (Clarkson et al., 2015). Others prefer a more conservative estimate of 47.5kya (Allen and O’Connell, 2014). Generally most archaeologists accept an arrival date in the Willandra Lakes at 50kya (Bowler et al., 2003, Hiscock, 2008).
Recent research has argued that there is indeed overlap between people and megafauna in Australia and…
Conclusion
We are far from establishing a reliable picture for the reasons behind the extinction of the Australian megafauna. In particular the explanation incorporating an anthropogenic cause is not as clear cut as some researchers would argue. Indeed the first evidence indicating that people actually hunted megafauna in Australia has only recently been provided (Hamm et al., 2016). The size and density of Aboriginal populations prior to the Last Glacial Maximum has in all likelihood been overestimated.
