A new light on extinction

By on 5 August, 2020

 

 

Scott Hocknull, senior curator of Geosciences at Queensland Museum and research team leader. Image: Queensland Museum.

The results of a long-running research project into fossilised megafauna that roamed tropical Queensland have revealed secrets of their extinction.

Extinction. Almost elegant in its finality, the phrase takes on a new cast in a time when human populations are being ravaged by coronavirus, in the country with the highest mammalian extinction rate in the world.

New research led by the Queensland Museum has discovered the cause of a most significant local disappearance, one whose cause has been debated fiercely – the megafauna of tropical Northern Australia.

The fossilised bones of gargantuan kangaroos, goannas, wombats and crocodiles were painstakingly excavated from South Walker Creek Mine, around 100 kilometres west of Mackay. These artefacts were studied for almost a decade, the research team also comprising scientists from Griffith University, Southern Cross University, University of Adelaide, University of Queensland, Australian National University and the University of Wollongong.

The results of their work were published Nature Communications on May 18 and represent the first reliable dossier of the fate of these monsters of the Australian tropics, 40,000 to 60,000 years ago.

Extinct giant freshwater crocodile tooth exposed at South Walker Creek. Image copyright Rochelle Lawrence, 2016.

The first bones were found during cultural heritage surveys by the Barnda Barnda people on their traditional lands – the largest land animals on the continent since the dinosaurs. Six-metre goannas and a cast of other mega-reptiles, a 275kg kangaroo and a three-tonne predatory marsupial Diprotodon stand among the 13 former residents discovered at the site.

These colossal beasts co-existed with the First Australians for between 15,000 and 20,000 years. A dominant theory as to their disappearance holds humans responsible for their extinction through over-hunting – but evidence newly uncovered by this mammoth project suggests that this is not the case.

‘The extinctions of these tropical megafauna occurred sometime after our youngest fossil site formed, around 40,000 years ago. The timeframe of their disappearance coincided with sustained regional changes in available water and vegetation, as well as increased fire frequency. This combination of factors may have proven fatal to the giant land and aquatic species,’ lead author Scott Hocknull, senior curator of Geosciences at Queensland Museum, writes in The Conversation.

Hocknull writes that the huge that people and these many megafauna shared country begs the question – how did people survive among these beasts in an era of such drastic environmental change?

Other evidence from the site indicate the extent of this momentous upheaval. A dire climactic change around 280,000 years ago wiped out a diverse set of rainforest fauna, setting off a sustained, but irreversible set of change processes that ultimately wiped out Walker Creek’s megafauna 40,000 years ago.

Hocknull holds that the trend of extinction continues, with the mantle taken up by major environmental change driven by human activity, that the geological record sounds an alarm.

‘The fossil record provides us with a window into our past that can help us understand our present. As our study shows, dramatic environmental change takes a heavy toll on species survival, especially for those at the top of the food chain. Will we heed the warnings from the past or suffer the consequences?’

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