Bears the earliest dated to about 2400-2500 million years ago, due to the connects of Arctic with Asia and Europe, as long as the weather conditions are appropriate and with adequate food, the animals on the mainland will be able to freedom to move to the North Pole, the Arctic bears and Arctic plant-eating bear are live in Arctic in early years, but because of the cold climate in the Tertiary on Earth, the south and north polar form glaciers in short period, a lot polar thermopiles animals fail to move to warmer areas and finally extinct, these including the burrowing-Bear. But a fur thick, carnivore, and good thermoregulation, wintering physiological and fast adaptation to cold bears survive in the Arctic, this is the polar bears we know today.

Antarctica since 60 million years ago would be completely isolated with the neighboring mainland, the mainland become independent which surrounded by the Pacific Ocean, Indian Ocean and the Atlantic ocean, the partition of ocean is impossible for terrestrial bears to migrate from a long-distance of swimming, so the Antarctic have no bears. In fact, in this area of 14 million square kilometers of the continent, there are no bears and others landing animal, all animals were placed under the marine fauna.