Polar Bears Have Irish Ancestors DNA study proves interbreeding with Irish bears of old By Rob Quinn, Newser Staff Posted Jul 8, 2011 1:37 PM CDT 5 comments Comments White, with a hint of green. (AP Photo/U.S. Fish and Wild Life Service, Steve Amstrup, File) (Newser) – Polar bears have as much claim to Irish descent as any St. Patrick's day marcher, according to a DNA study of ancient bear bones. All polar bears alive today have the maternal DNA of the extinct Irish brown bear, the researchers found, suggesting that the two species interbred during the last Ice Age as glacial sheets spread south to Ireland. The researchers believe one hybrid cub became a polar bear matriarch and descendants of the other matriarchal lines died off, the Los Angeles Times reports. "It's amazing to think that Irish brown bears are the ancestors of the modern maternal polar bear lineage," the lead researcher tells the BBC. "As the hybridization between the two species occurred at a time when their home ranges overlapped, most likely during environmental stress, this has implications for polar bears in today's climate."