Polar bears probably first appeared 200,000 years ago during the Pleistocene and were much larger than they are today. They are the most recent of the eight bear species.
Scientists believe polar bears descended from a group of brown bears that became isolated by glaciers in an area near Siberia. These bears underwent a rapid series of evolutionary changes in order to survive—from changes in the color of their fur and shape of their body to keener senses to sharper teeth.
Today's polar bear is superbly adapted to life in the Arctic.
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