From which continent do polar bears come?

Polar bears, native to the Artic Circle, were once believed to have evolved from female brown bears at the height of the ice age. Recent studies, however, insist they are a genetically differentiated species. As an ice-dependent mammal, distinct from brown bears, surviving the shrinking Arctic ice along with other threats caused by people, such as loss of habitat, conflict with people and chemical spills, may push the species to the verge of extinction.