Antarctica is an island. The closest land mass with a bear population is South America. There is roughly 1,000km (600 miles) of ocean between them. Bears can't swim that far.

Migration is unlikely due to distance and because most of the world between these locations is too warm for polar bears. That is also why you don't find Penguins in the Arctic.

If it wasn't for global warming -- Chicago would still be under a mile of ice.

Fortunately, Cro Magnon people learned how to make fire -- the smoke from their campsites melted the glaciers.

They are scared of penguins.

http://images.nationalgeographic.com/wpf/media-live/photos/000/003/cache/polar-bear-leaping_337_600x450.jpg

Why Polar Bears live in the Arctic and not Antarctic are there unfavourable conditions in the Antarctic or the conditions are similar but the migration was unlikely due to the distance?