Polar Bears Not as Closely Related to Brown Bears as Once Thought

When is a bear not a bear? When it's a distant cousin.

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A mother polar bear plays with two of her three cubs at the Moscow Zoo on March 22, 2012.

When is a bear not a bear? When it’s a distant cousin.

Scientists have long thought that polar bears became established as their own species relatively recently, their fur whitening as an evolutionary response to their icy environment. But it turns out that polar bears aren’t just brown bears in white coats: they may have in fact split off from a common ancestor as early as 600,000 years ago. That would make brown and polar bears more like sixth cousins, than they are brother and sister.

Axel Janke and Frank Hailer, researchers from the Biodiversity and Climate Research Center in Frankfurt, Germany compared genetic sequences from 19 polar bears, 18 brown bears and 7 black bears. Fourteen stretches of DNA were compared against each other before scientists arrived at the revamped conclusion. The results were published in Science journal online last week.

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Several recent studies involving mitochondrial DNA suggested that polar bears split off from brown bear lineage much earlier than previously thought – 150,000 years ago or thereabouts. But mitochondrial DNA studies tend to give “an incomplete picture of evolution,” according to the Times. It was also around that same time that polar bears could have very well interbred with extinct Irish brown bears, leading to the confusion.

Hailer attested that polar bears seem to be “older and much more genetically unique” than previously thought. The species is currently listed as “vulnerable” on the international animal conservation list, just before “endangered” — due to the accelerating loss of sea ice which the bear depends on.

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Erica Ho is a contributor at TIME and the editor of Map Happy. Find her on Twitter at @ericamho and Google+. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.