Study clears humans over megafauna extinction
A study of small animals has added weight to the theory that climate change rather than humans wiped out giant Australian marsupials, or megafauna, about 40,000 years ago.
Queensland University of Technology PhD researcher Gilbert Price, working with the Queensland Museum, has undertaken a systematic analysis of a 10-metre site in the fossil-rich Darling Downs region of south-east Queensland.
He says the researchers looked for small fauna, such as land snails, frogs, lizards and bandicoots.
"Because the Darling Downs hasn't been properly excavated in the past these small fauna are previously unknown to have even occurred," Mr Price said.
"These are the sort of guys that can give us great information about what the habitats and climates were like during the times of the megafauna."
Mr Price says the dig has revealed dramatic changes in habitat - and consequently fauna - during the latter part of the Pleistocene epoch, which stretched from 1.8 million to 10,000 years ago.
"It tends to be the case that over the entire period of the deposition, the faunas and the habitats were changing so it reflected the contraction and possibly local extinction of different sorts of habitats, mainly the woodland and vine-thicketed habitat," he said.
"That's associated with different species going at least locally extinct over that same period."
He says that in the oldest sections of the dig, which date back about 45,000 years, species that depended on woodland and vine thickets dominated.
In the mid-section, there was a mix of species that were either "habitat generalists" or preferred open areas, which Mr Price says suggests the environment was evolving toward grasslands.
"By the latest Pleistocene, species dependent on wetter conditions disappear from the fossil record, while animals such as long-nosed bandicoots that aren't habitat-specific remain," he said.
Mr Price says the research rules out humans as the culprit for the local extinction of the megafauna.
"We've done a little bit of radiocarbon dating on the deposits itself and we know that the age of the deposits pre-dates the first humans on the Darling Downs by about 30- to 35,000 years," he said.
"We know that there's no human or cultural artefacts in the deposits as well and we know that all the cut marks on the bone themselves are related to... some of the other species that lived on the Darling Downs, such as marsupial lions."
That leaves one main culprit.
"That culprit is climate," Mr Price said. "It does appear that climate change was the major factor in driving the megafauna extinct."
The findings may offer clues to changes in the current environment.
"The climate at the time is very similar to what we are seeing today - we're basically both in an inter-glacial period," Mr Price said.
"It's a time... of climate instability."
He says it may be possible to use the fossil records to predict what might happen in the future.
"We might be able to predict the future climate changes on the basis of the fossil records... it could be great as some aspect of conservation right there," he said.
Queensland Museum's assistant curator in geoscience, Scott Hucknell, says understanding the past offers clues to current and future risks to the environment.
"These amazing fossil deposits are providing us with the key to understanding Australia's past, something integral when developing long-term strategies for a sustainable future," Mr Hucknell said.
Mr Price's research is published in the latest edition of the journal, Memoirs of the Queensland Museum.
Some of the items dug up during the project are part of the Dragons and Diprotodons exhibit currently on display at the Queensland Museum.