Steve Amstrup/U.S. Fish and Wildlife Service, via Associated Press
Polar bears on pack ice in the Beaufort Sea off northern Alaska. Scientists say polar bears are not descended from brown bears
By JAMES GORMAN
Polar bears, long thought to have branched off relatively recently from brown bears, developing their white coats, webbed paws and other adaptations over the last 150,000 years or so to cope with life on Arctic Sea ice, are not descended from brown bears, scientists report.
Instead, according to a research team that looked at DNA samples from the two species and from black bears, the brown bear and polar bear ancestral lines have a common ancestor and split about 600,000 years ago.
