 All North American bears descended from Etruscan bear stock in Asia.
 First to arrive in North America 2.5 million years ago was the black bear.
 Brown bears made their way to North America 300,000 years ago by way of the Aleutian land bridge.
 DNA evidence confirms the polar bear evolved from the brown bear 150,000 years ago.
 There are grizzly bear hybrids, where a polar bear and grizzly have produced offspring.
 In North America there are an estimated 750,000 black bears, 60,000 brown bears and 25,000 polar bears.