Extinction 'by man not climate'

BBC News 11 Aug 08;

The extinction of many ancient species may be due to humans rather than climate change, experts say.

Large prehistoric animals in Tasmania may have been wiped out by human hunting and not temperature changes, a team of international scientists argue.

This pattern may have been repeated around the globe on islands such as Great Britain, the scientists say.

The findings were published in the American scientific journal - Proceedings of the National Academy.

Giant kangaroos

For many years, scientists have been arguing about the causes of widespread extinctions of vast numbers of species at the end of the last Ice Age.

What has caused the most debate has been the fate of megafauna - large bodied creatures in Australia that included three-metre tall giant kangaroos and marsupial lions.



Humans arrived in Tasmania about 43,000 years ago, when the island became temporarily connected by a land bridge to mainland Australia.

It had been thought that many megafauna were already extinct by this stage.

But using the latest radiocarbon and luminescence dating techniques, the British and Australian scientists say they were able to determine the age of the fossilised remains of the megafauna more accurately than ever before.

They discovered that some of the giant animals survived for 2,000 years after humans arrived, and at a time when the climate was not changing dramatically.

The researchers concluded that these species were driven to extinction by hunting.

Human blame?

Professor Chris Turney, from the University of Exeter, the lead author on the research paper, said that 150 years after the publication of Charles Darwin's seminal work The Origin of Species, the argument for climate change being the cause of this mass extinction had been seriously undermined.

"It is sad to know that our ancestors played such a major role in the extinction of these species - and sadder still when we consider that this trend continues today," he said.

Given Tasmania's history as an island, the research findings should help to disentangle the role of humans and climate change in other island environments, such as Britain, the scientists said.

Previous research had found that on mainland Australia some 90% of megafauna disappeared about 46,000 years ago - soon after humans first settled on the continent.

Prehistoric giant animals killed by man, not climate: study
Madeleine Coorey, Yahoo News 12 Aug 08;

The chance discovery of the remains of a prehistoric giant kangaroo has cast doubts on the long-held view that climate change drove it and other mega-fauna to extinction, a new study reveals.

The research, published this week in the US-based journal Proceedings of the National Academy of Sciences, argues that man likely hunted to death the giant kangaroo and other very large animals on the southern island of Tasmania.

The debate centres on the skull of a giant kangaroo found in a cave in the thick rainforest of the rugged northwest of Tasmania in 2000.

Scientists dated the find at 41,000 years old, some 2,000 years after humans first began to live in the area.

"Up until now, people thought that the Tasmanian mega-fauna had actually gone extinct before people arrived on the island," a member of the British and Australian study, Professor Richard Roberts, told AFP Tuesday.

He said that it was likely that hunting killed off Tasmania's mega-fauna -- including the long-muzzled, 120 kilogram (264 pound) giant kangaroo, a rhinoceros-sized wombat and marsupial 'lions' which resembled leopards.

Roberts, from the University of Wollongong south of Sydney, said the idea that climate change could account for the death of the animals was disputed by the fact the area had a very stable climate in the critical time period.

"Things were very climatically stable in that part of Australia and yet the mega-fauna still managed to go extinct," he said. "So it's down to humans of one sort or another."

Roberts said because the large animals were slow breeders, it would not have required an aggressive campaign to see them quickly die out.

"A lot of people still have in their minds an axe-wielding, spear-wielding people, bloodthirsty, out there slaughtering all over the place -- it wasn't like that at all," he said.

"It was basically just one joey (baby kangaroo) in the pot for Christmas. And that's all you've got to go to do to drive slow-breeding species to extinction."

Roberts said the Tasmanian results back up the theory that man was responsible for the death of the mega-fauna on mainland Australia, estimated by some to have occurred shortly after human occupation about 46,000 years ago.

The reasons behind the mass extinction of giant animals, which took place around the world towards the end of the last ice age, has been hotly contested with theories ranging from climate change to human and extraterrestrial impacts.

The finding of the latest study has already been contested, with Judith Field of the University of Sydney saying the idea that humans killed the giant creatures was "in the realms of speculative fantasy".

"Humans cannot even be placed at the scene," she told the Sydney Morning Herald.