What happened to Australia’s Ice Age megafauna?

UQ vertebrate palaeoecologist Dr Gilbert Price investigates what happened to Australia's megafauna. 

Huge land turtles, 2.5 metre tall kangaroos, massive cold-blooded killer goannas… These are but a few of the giant animals that once roamed Australia during the Quaternary: the period of geological time that we often refer to as the ‘Ice Ages’.

But what happened to these megafauna? When did they go extinct and why?

It’s a research area that I am most fascinated by. And talking to others, it’s definitely something that inspires a lot of discussion and debate. I mean, who doesn’t love a good mystery, right? And in this case, it’s an Ice Age cold case and one of the biggest research questions in the Australian palaeo-sciences.

Extinction and public opinion

I recently had the privilege of being invited to give a presentation for BrisScience. BrisScience is a Brisbane-based monthly lecture series that aims to bring scientists and their science out of the lab and deliver it direct to the public. So for me, that meant packing up my thoughts and turning it into something digestible and interesting for a diverse audience.

What happened to the marsupial ‘rhino’, Zygomaturus?

It doesn’t matter if you’re a hardcore scientist or just a regular person walking down the street, everyone seems to have an idea about what happened to the megafauna. For scientists, they might form their opinion based on reading scientific literature. For members of the public, a lot of the time their thoughts might be crafted by things like media reports or easily assessable information websites such as Wikipedia.

Working in this space day in, day out, it’s sometimes hard to gauge what people outside of the research community actually think. But here at BrisScience, I had an opportunity to go direct to the public and get their thoughts.

Why the megafauna went extinct: the audience votes! (credit: Tara Horner via Twitter)

During the presentation, rather than have the audience put up their hands and shout things out, I used Mentimeter software to pose the question: “Why did the megafauna go extinct?” The audience was invited to go to a particular website and type in answers using their phones. The answers were then broadcast live directly into my PowerPoint presentation as an evolving word cloud.

The results were really fascinating! There were 105 respondents out of the 300 or so in the room. Aside from a few creative answers such as unicorns, Jesus, and Flying Spaghetti Monsters, there seemed to be a clear candidate for the extinctions: climate change.

The results are in!

An unexpected response

Science tells us that the time of the megafauna was punctuated by repetitive wet and dry phases in climate, with a long-term trend towards progressively drier and drier conditions. In fact, the last glacial cycle that led into the most recent Ice Age was the harshest episode of climatic change of the entire Quaternary.

But I didn’t tell the audience that prior to the survey. All I had mentioned was that humans arrived in Australia around 55-60 thousand years ago, that the Quaternary was characterised by swings in climate, and that the megafauna were (mostly) extinct.

Climate change was not the answer that I was expecting; I thought it would have been human hunters for sure. But, in a way, I found a lot of comfort in the overarching public view.

That’s not because I necessarily think that climate change wiped out all 90 species of Australian megafauna, but because of the worrying way that the debate has been playing out of late.

What we really know about the extinctions

There has been a spate of finger-pointing research articles recently, all arguing that human hunters solely drove the extinctions. Those research articles have translated into extensive and global media coverage as well, with headlines screaming out: ‘PEOPLE DID IT!’

I’ve read those research papers very closely and must say that I’m not convinced. Aside from some howling mistakes (like this one reporting the extinction of the kangaroo, Macropus, 43 thousand years ago… Macropus are very much alive and well, and include modern species like Red and Grey kangaroos, as well as 13 or so other extant members), the data just don’t stack-up to comprehensively ‘prove’ that humans did it.

Some of the recent headlines

Ideally, to test the human overkill model, you need to first show that as soon as humans arrived, all 90 species of megafauna immediately went extinct, and that climate change was not significant at the time.

A close reading of the actual datasets shows only around 15 species of megafauna date to the time period of human arrival. Most species significantly pre-date humans, or have no reliable dates at all. That is, we don’t even know when the majority of megafauna evolved, let alone went extinct. As for climate change, a huge range of independent datasets demonstrates a big shift toward arid conditions right around the time of human arrival, so obviously, climate change cannot be excluded from the extinction equation.

The BrisScience survey was a great exercise in the end. The thing that pleased me the most, perhaps with the possible exception of whoever gave the answer “Flying Spaghetti Monster”(!), was seeing a public that are independent thinkers and are driven in seeking out the truth using alternative media.

To the BrisScience audience that night, thank you so much for coming and, of course, thank you for your wonderful participation!

Dr Gilbert Price is a vertebrate palaeoecologist in the School of Earth Sciences at The University of Queensland. You can read more about megafauna and his research on his blog, Diprotodon

Last updated:
22 April 2016