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News in Science
Komodo dragon had Australian origins
Wednesday, 30 September 2009 Sarah Clarke for The World Today
True blue: Fossil evidence suggests the komodo dragon may have evolved in Australia (Source: STR New/Reuters)
Giant lizards pack venomous bite, Science Online, 19 Oct 2009
Cold comfort for reptiles in warmer world, Science Online, 17 Feb 2009
Australia's lizards are venomous too, Science Online, 17 Nov 2005
A team of scientists has overturned the theory that the world's largest lizard evolved on the islands of Indonesia.
Weighing around 70 kilograms and growing up to three metres long, the Komodo dragon is regarded as the world's largest lizard.
But the discovery of an array of fossilised bones at three different sites across Queensland has triggered a new theory - that Australia was a hub for lizard evolution.
The research, which involved scientists from Malaysia, Indonesia and Australia and led by Dr Scott Hocknull of the Queensland Museum, is published today on the science journal website PLoS ONE.
Once reputed to be the origin of the Chinese dragon myth, the Komodo dragon is now in such small numbers it's considered a vulnerable species.
The remaining five thousand or so live on a handful of isolated islands in eastern Indonesia, which many scientists always believed was their birthplace.
Hocknull says the fossilised bones discovered in Queensland are identical to the Komodo dragon.
"It was a particular set of fossils that were found at Mount Etna in Queensland that were dated around 300,000 years old that really sparked my interest," says Hocknull.
"I was figuring out what on earth they were and my assumption was that it was just going be another species of lizard that lived in Australia, and still does, say for example a lace monitor. But it was much much bigger."
Hocknull says the fossils show that the komodo dragon had its origins here in Australia about four million years ago and persisted in Australia until at least 300,000 years ago.
"What it shows is that again Australia is home to some very strange and very peculiar animals that now no longer live on our continent and have found a home elsewhere," he says.
Extinction trigger
The researchers believe the komodo dragon dispersed westward, reaching the island of Flores around 900,000 years ago.
The size of the fossils found in Australia suggest it was always a large land-based lizard and it spent four million years here before it became extinct.
The question is what caused its extinction?
"Well we don't know because the 300,000 year record is the youngest record that we have," says Hocknull. "We can assume that the komodo may have kicked along in Australia right up until human arrival. There's no reason to assume not."
"Perhaps humans were the cause of their extinction; perhaps it was climate change, perhaps a combination of both.
"What the record on Flores shows in Indonesia is that the komodo dragon was there for over a million years kicking along quite nicely. Big faunal changes, volcanic eruptions, all these amazing things happening on that island and yet the komodo dragon existed without any major issues."
According to Hocknull that all changed about 2000 years ago when its range retracted to the coast lines of where it is now found.
"The only thing you can link that to is habitat destruction and persecution by modern humans," he says.
Man versus dragon
The Komodo dragon is well known as a man eater, and would have no doubt put up a good fight against modern man
But why did it survive and thrive on the tiny isolated Indonesian island of Flores?
Palaeontologist Professor Tim Flannery of Macquarie University in Sydney has a theory.
"It became extinct, we think about 50,000 years ago, about the time that humans arrived in Australia, and of course it disappeared from every other island in Indonesia except Flores," says Flannery.
"The one interesting thing about Flores is that it is the home of the 'hobbit'. The hobbit was there for about two million years and maybe hobbit hunting was a bit like pre-school for the komodo dragon, they learnt how to deal with human-like hunters.
"Whereas in Australia and the rest of the islands the first thing that turned up was fully modern humans and they seem not to have been able to cope with that."
Tags: fossils, evolution, palaeontology, reptiles
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