Polar bears older and more vulnerable

Polar bears have roamed the Arctic for five times longer than previously thought and adapted slowly to their frozen habitat, suggesting rapid climate change could be a bigger threat to them than had been assumed.

Scientists now believe polar bears date back some 600,000 years – first appearing during one of the Earth’s coldest periods – and evolved gradually over a series of repeated glacial cycles.

If this is true, they may not have time to adjust to a rapidly changing climate caused by man-made carbon emissions.

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The pressure on polar bears would be made worse by human factors such as habitat loss, hunting and pollution, the experts fear.

Earlier research suggested polar bears were a recently evolved type of northern brown bear.

They were believed to have acquired their white coats and ability to cope with icy environments relatively quickly.

Those studies were based mainly on studies of a type of DNA passed down through the generations by females.

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But the authors of the new research say large chunks of information, were missed as if reading only a few pages of a book.

They carried out a new analysis of nuclear DNA – the DNA found in the hearts of cells – and after looking at many independently inherited regions of the genetic code concluded that both polar and brown bears had a much longer history.

At the time, the bears’ immediate ancestor split into two species, global temperatures had reached a long-term low.

International experts led by Dr Frank Hailer, from the Biodiversity and Climate Research Centre in Frankfurt, Germany, report the findings in the journal Science.

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They wrote: “An evolutionary origin several hundred thousand years ago implies that polar bears as a species have experienced multiple glacial cycles and have had considerable time to adapt to arctic conditions.”

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