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Mammoth extinction not due to inbreeding
by Staff Writers
London (UPI) Mar 24, 2012

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A British study on the extinction of woolly mammoths found the last known population of the prehistoric animals did not die out because of inbreeding.

The study, conducted jointly by British and Swedish scientists, examined bones, teeth and tusks from Wrangel Island in the Arctic Ocean where the last known population of woolly mammoths lived about 4,000 years ago, the BBC reported.

Mammoths generally disappeared from mainland Eurasia and North America about 10,000 years ago, but lived on for another 6,000 years on Wrangel Island.

"Wrangel Island is not that big and it was initially thought that such a small population could have suffered problems of inbreeding and a lack of genetic diversity," said the report's co-author, Dr. Love Dalen of the department of molecular systematics at the Swedish Museum of Natural History.

Researchers found that, contrary to popular belief, the animals more likely were killed off by human activity or environmental factors.

The report, published Friday, concluded that the extinction of mammoths on Wrangel Island was "not a delayed outcome of an inevitable process" such as inbreeding.

"This suggests that the final extinction was caused by a rapid change in the mammoths' environment, such as the arrival of humans or a change in climate, rather than a gradual decline in population size," the study said.

The study also found the population of mammoths on the island generally ranged between 500 and 1,000.

Dalen said the study can be useful in modern-day conservation programs.

"What's really interesting is that maintaining 500 effective individuals is a very common target in conservation programs," he said. "Our results therefore support the idea that such an effective population size is enough to maintain genetic diversity for thousands of years. These mammoths did fine with what was originally considered to be a small number."

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Humans blamed for Australian extinctions
Sydney (UPI) Mar 23, 2012 - Human hunting caused the extinction of ancient giant animals, or "megafauna," in Australia about 40,000 years ago, scientists say.

A study has put the blame for the extinction of 600-pound kangaroos and birds twice the size of modern emus on humans rather than on climate change as was once thought, Britain's The Daily Telegraph reported Friday.

"The debate really should be over now," John Alroy, from Macquarie University in Sydney, said. "Hunting did it, end of story."

The researchers studied fungi found in the dung of large herbivores in cores of sediment from a fossilized swamp in Queensland dating back 130,000 years.

"When there was lots of fungus, there was lots of dung and lots of big animals making it," Chris Johnson from the University of Tasmania said. "When they disappeared, their dung fungus went too."

The study shows numbers of megafauna species were stable until 40,000 years ago despite two periods of climate change, the researchers said, suggesting newly arrived humans hunted the animals to extinction.

Still, some scientists say they're not convinced and that the presence of the ancient spores does not reflect an abundance of the giant animals.

"The only evidence we have from Queensland for megafauna indicates that they were gone before humans arrived," Judith Field, from the University of New South Wales, said.

"The interpretations drawn from [the new study] are unsubstantiated and can be explained by other mechanisms."


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Greenland ice sheet may melt completely with 1.6 degrees global warming
Potsdam, Germany (SPX) Mar 19, 2012
The Greenland ice sheet is likely to be more vulnerable to global warming than previously thought. The temperature threshold for melting the ice sheet completely is in the range of 0.8 to 3.2 degrees Celsius global warming, with a best estimate of 1.6 degrees above pre-industrial levels, shows a new study by scientists from the Potsdam Institute for Climate Impact Research (PIK) and the Universi ... read more

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