A study of the DNA of ancient brown bear bones in Ireland proved that the maternal ancestors of modern polar bears were Irish.
By studying 17 sets of brown bear teeth and skeletons, found in eight caves across Ireland, in 2011 scientists found conclusive evidence of the connection.
The study was the work of Prof Daniel Bradley, of Trinity College Dublin (TCD) and Dr. Ceiridwen Edwards, formerly of TCD and now at Oxford University who collaborated with Prof Beth Shapiro, of Pennsylvania State University.
Dr. Edwards said "It's amazing to think that Irish brown bears are the ancestors of the modern maternal polar bear lineage.
"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."