Polar bears descended from extinct brown bears

Scientists have discovered that modern polar bears are descended from now extinct brown bears that roamed the region we know today as Britain and Ireland. It is thought that polar bears moved into Britain just before, or during the last Ice Age, where they mated with female brown bears.

The maternal lineage of the extinct Irish brown bear can still be traced to all modern polar bears today, according to the research published in the latest issue of the journal Current Biology. However, perhaps surprisingly, this DNA sequence does not appear in modern brown bears, but only in polar bears and the ancient brown bears that inhabited Ireland when it was experiencing much cooler temperatures.

The lead author said: “Hybridisation between ancient Irish brown bears and polar bears has led to the complete replacement of the original polar bear mitochondria. This maternal lineage is now present in all modern polar bears. Environmental conditions appear to have played, and continue to play, a big part in the evolutionary history of polar bears. Today’s warming climate is again bringing modern polar bears into contact with brown bears in places like Canada and Alaska.”

Read more at University of Oxford