19 April 2012 Last updated at 19:57 ET By Helen Briggs BBC News

The polar bear is much older than previously thought, according to new genetic evidence.

DNA studies suggest the Arctic predator split from its ancestor, the brown bear, about 600,000 years ago.

Previous estimates put the polar bear at about 150,000 years old, suggesting the mammal adapted very rapidly to Arctic life.

Conservationists say the new study, published in Science, has implications for bear conservation.

Polar bears are listed as threatened under the US Endangered Species Act.

Conservationists say their survival is at risk, mainly due to the loss of the Arctic sea ice on which they spend much of their lives.

Dr Frank Hailer of the German Biodiversity and Climate Research Centre in Frankfurt, who led the international study, said the genetic information shed new light on conservation issues.

"It fundamentally changes our understanding of polar bears and their conservation today," he told BBC News.

"They have survived previous warm phases but they carry scars from these times - they must have been close to extinction at times."

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DNA reveals polar bear's origins