Scientists have found that the female ancestor of all polar bears was a brown bear which lived in present-day Britain and Ireland during the last ice age – 20,000 to 50,000 years ago. Changes in climate affecting the North Atlantic ice sheet probably gave rise to periodic overlaps in bear habitats and these overlaps then led to interbreeding between bears, causing maternal DNA from brown bears to be introduced into polar bears, according to a study by British and American researchers.
