It’s a cold, wet, evening just after dark anywhere in Australia. You can hear the wind rustling the trees as it blows up the street.
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As the streetlight above your head flickers on and off you see…something, a shape through the drizzling rain.
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The hairs on the back of your neck stand up and take notice, your heart starts to beat faster; what is that enormous beast approaching.
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Feet stuck fast with terror, there’s nowhere to escape.
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Out of the shadows it comes, almost two meters tall at the shoulder and over three meters in length.
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Suddenly you’re confronted with two and a half tonnes of enraged…snarling…wombat?
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At least not nowadays, and probably never enraged and snarling, but…50000 years ago you could very well have run into this super-sized herbivorous wombat-like beast – Diprotodon.
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It was the time of the megafauna; when woolly mammoths and sabre-toothed tigers roamed Europe and North America.
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Australia had it’s own unique spread of fearsome giant animals; the marsupial lion Thylacoleo; a 2.5 metre tall kangaroo called Procoptodon, the tallest ever marsupial; and Megalania, the largest-ever lizard, over 5 times heavier than the Komodo dragon.
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Dr Gilbert Price is a Palaeoecologist at the University of Queensland and studies these giant animals and others – including a 30-kilo koala – from the Pleistocene era.
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Dr Price said this research into the past could provide clues for wildlife conservation in the future, especially in light of climate change.
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“I guess the most important thing is the conservation aspect,” he said.
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“Look at the world we live in today and some of the climatic challenges we’re currently facing, things like the effects of droughts, enhanced climatic variability, increased El Nino intensification.”
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“The thing a lot of people don’t realise is that climate change, the big buzzword, isn’t something invented by Al Gore.”
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“Climate change has been shaping, reshaping and moulding the Australian environment for millions of years, especially the last two million years or so.”
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Dr Price said the climatic changes during the last two million years saw the evolution of Australia’s modern ecosystems.
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“It saw the emergence of the modern flora’s and fauna’s, but it’s also associated with major extinction events like the megafauna extinction, which happened somewhere between 30 and 50 000 years ago,” he said.
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“In essence my research is looking at the response of animals to prehistoric environmental and climatic changes.
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“It’s seeing what lessons we can learn from the observation of deep time and applying that to some of the conservation challenges that we’re currently facing.”
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To do this, Dr Price uses uranium-thorium dating – similar to radiocarbon dating – to find out the age of the fossils he finds and how the different animals represented in the fossils interacted.
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“I spent a lot of my early research out in the field digging up the bones of these megafaunal animals; giant wombats, giant kangaroos, giant lizards, whatever; but also smaller things – the frogs associated with them, the bandicoots, the rats,” Dr Price said.
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“I was then trying to reconstruct what the environments would have been like, and finding out how Diprotodon interacted in its environment, along side a bandicoot, which is along side a big lizard, which is along side a frog, et cetera.”
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“That’s important stuff, but the really important thing is to be able to put a date onto these palaeoecological interpretations.”
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Dr Price said that was significant for not only figuring out the timing of when events happened, but also placing the sites he’d been working on into a broader continental and global context.
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In an as yet unpublished review paper, Dr Price investigated the number of available uranium-thorium dates for some of Australia’s megafauna in an attempt to unravel the mystery of their extinction.
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He found Diprotodon, the most common megafauna fossil – found all over Australia, had only 29 actual dated occurrences.
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“Which sounds pretty good, but the reality is that if you divide that number of dates by the time period it’s actually been around, you’ve got one date for this animal every odd 86 thousand years,” Dr Price said.
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“When you’re trying to define exactly when a Diprotodon suffered extinction, with a chronology that coarse, what do you say?”
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“And Diprotodon’s got more dates on it than anything else, the majority of megafauna species out there just lack dates completely, so how do we argue one way or the other the timing of the extinction of these things?”
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Another problem Dr Price faced was: “How many species of Diprotodon were there?”
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Although there are eight species officially described, some early researchers estimated that up to 20 different varieties once roamed the continent.
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This problem is compounded by the fact that many of these early descriptions are based on fragmentary fossil remains collected from all over the continent, and also because Diprotodon comes in two distinct sizes – large and extra-large.
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“It was a really challenging question to answer and it’s something that’s been debated since the discovery of the first fossils back in the 1830’s,” Dr Price said.
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“The general idea was: ok there probably wasn’t eight, there was maybe only two or three species at best.”
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To get a definitive answer, Dr Price began a painstaking study of more than 1000 Diprotodon teeth, jaws and skulls, which took him from the British Museum of Natural History in London to the Australian Museum in Sydney.
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And what he discovered shook the foundations of our knowledge of this mysterious marsupial.
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“My research showed that, yeah, there are definitely two size classes of this thing, but the data actually suggested that rather than multiple species, there was only actually one species,” Dr Price said.
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“The way I explained the two different size classes is that they were simply male and female of the species itself.”
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“So you could say that Diprotodon was really only one of its kind – literally.”
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Dr Price said that on the basis of those results, it was possible to draw some amazing conclusions on how Diprotodon behaved.
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“It was probably the case that Diprotodon was sexually dimorphic – you know big males, smaller females,” he said.
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“When you have sexually dimorphic organisms, whether it be an elephant or a lion, they tend to all exhibit the same breeding strategy.”
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“It’s a polygamous strategy, so the male will try to sire as many offspring as he can with as many different females as he can.”
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While the research shed light on Diprotodon’s behaviour, Dr Price said it was particularly important because it showed there weren’t eight species that suffered extinction – there was only one.
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“It’s sad. Diprotodon was the only one of it’s kind at the time, it was the last surviving member of this massive family of super marsupials that was around for at least 25 to 30 odd million years, possibly even longer,” he said.
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Despite the fact that the worlds biggest ever marsupial is now long gone, future lessons in conservation could be learnt when we fully understand what drove it to extinction – climate change or humans.
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To shed light on this, Dr Price worked on another of Australia’s extinct megafauna – a giant, porky koala.
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“Modern koala’s today might push 10 to 12 kilograms. This giant version would have made branches sag in the eucalypt trees, it got to anywhere between 25 to 30 odd kilograms in weight!” Dr Price said.
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One of Australia’s largest-ever tree-climbing marsupials, this giant koala is known as Stirton’s koala (Phascolarctos stirtoni) and was discovered in the 1960s.
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“The idea is that the small guy is just a dwarf version of this big thing, and there’s all sorts of questions on why is this thing so small today? Why isn’t it big?” Dr Price said.
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“Some people out there say climatic changes did this or that to it and that’s why its smaller, others suggest that maybe humans were hunting specifically for the larger koalas and that drove the decrease in body size over time.”
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“But these hypotheses just don’t hold up when you look at the evidence.”
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To support the dwarfing hypothesis, that is modern koala’s are just a small (dwarf) version of giant koala’s, it must be shown that the modern koala wasn’t around before the 30 to 50 000 year-ago megafaunal extinction, and the giant koala wasn’t around after it.
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This is essentially showing that the modern koala and the giant koala didn’t live together anywhere, at anytime in the past.
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It also has to be shown that both the modern koala and giant koala are morphologically identical; essentially the modern koala is a shrunken, identical version of the giant.
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But Dr Price said his research showed the only one of the afore-mentioned criteria to hold up was the extinction of the giant koala.
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“The fact is that the modern koala isn’t just a dwarf of this big guy, it’s an animal that’s been around for at least 350 000 years and it actually lived along side the giant form,” he said.
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“So we actually had these two forms, this giant and the smaller thing, living together, side by side, for hundreds of thousands of years.”
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“It’s just a case that 50 000 years ago the big guy drops out of the fossil record and the smaller guy continues for some reason.”
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“It also shows that the modern koala is a nuggetty little thing; it’s been around for such a long period of time and it’s survived wave after wave of intense climatic changes – super droughts, massive vegetation changes,” he said.
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“The climatic changes of the last 50 000 years have certainly done things to the modern koala population – like completely reorganized where it lives – but the little guy managed to survive them, whereas the big guy didn’t.”
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“If you can figure out why that’s the case then that’s going to go miles in terms of trying to conserve the koalas today.”
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Dr Price’s current research is dating the megafauna record of the Darling Downs region in Queensland.
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He said it was showing results that could go a long way to ending the debate about what caused the megafaunal extinction and may provide insights into how today’s species will cope with climate change.
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“My previous research showed that at this one particular site, the stuff at the bottom, the bottom unit, which is obviously the oldest fossil unit we’ve got, is just chock full of megafauna,” Dr Price said.
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“We’ve got something like 15 or 16 different species, from the big wombat-like Diprotodons to kangaroo’s and lizards, anything you can think of.”
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“But as you get to the younger and younger layers of sediments, the megafauna just drop out of the fossil records; by the time you get to the top unit of fossils, you’ve only got 4 species of megafauna, versus the 15 or 16 we had at the bottom.”
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“So that’s suggesting that there’s something going on, some sort of extinction going on through time.”
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Dr Price said determining how quickly the megafaunal extinction process occurred would shed light on its cause.
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If the extinction happened rapidly, around about the time the first humans crossed Australian shores, it would be fair to argue that humans drove the extinction patterns at this particular fossil site.
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If the extinction occurred over a longer period of time, and wasn’t associated with humans, it would be fair to argue climate change.
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“What we see in the fossil record in the Darling Downs, and I think it’s fully kick ass, is that megafauna extinction took place over a long period of time, something like 50 000 years,” Dr Price said.
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“And these animals were suffering the local extinction on the Downs at a period immediately prior to the first humans entering Australia.”
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“So I’m certainly arguing for a climatic driver of what we see on the Downs, and even that has massive implications for determining the continental extinctions of these things.”
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“I mean the results suggest that the local megafauna out there were in some serious trouble leading up to the time period of human colonisation.”
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Dr Price said that any of the negative impacts humans had on megafauna – hunting them out or burning landscapes and changing the makeup of habitats – were most likely just compounding the longer-term extinction process.
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“I think research is so important, it allows you to mitigate against the problems that we’ve had previously and predict…predict what’s going to happen, say to a population of kangaroos if a ten year super-drought comes through,” he said.
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“I’d like to think that my research will make a difference in the future, not just to the scientific community but to the public too.”
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“I just see so much application for it in terms of conservation and that’s what drives me now.”
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