“The Irish genetic sequences are much closer to the modern polar bear,” said study researcher Daniel Bradley, of Trinity College Dublin. “As the climate has changed, what we are seeing is the tracking of that climatic change in the sequences in the bears.”

The researchers started by analyzing the DNA of brown bears from Ireland and comparing it with that of ancient and modern polar bears. They used samples from bear skeletons found in Irish and British caves. The oldest skeletons were 120,000 years old and the youngest were at least 3,000 years old, the latter having died shortly before the bears went extinct in the area.