Polar Bears Evolved Just 150,000 Years Ago
Here two polar bear cubs snuggle up. The polar bears, which evolved from brown bears, originated some 150,000 years ago, according to genetic analyses of a polar bear fossil.
Goose Eggs Could Save Polar Bears
Polar bears hunt seals from the ice. When their icy habitat melts, the bears are forced to swim more, move north or retreat to land.
Knut at the zoo
Even though Knut's fur looks white, his hair is really made of clear, hollow tubes filled with air.
Knut weighed just 1.8 pounds (810 grams) at birth, but by age 2 he weighed some 440 pounds (200 kilograms). Here Knut is just a few months old.
Knut made his first pubilc appearance at the Berlin Zoo in March 2007. He was born in captivity on Dec. 5, 2006.
Knut with zookeeper
Polar bear Knut with his zookeeper Thomas Doerflein (who had died in 2008) on the day of the first public appearance of the little bear in March 2007.
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Jennifer Welsh is a Connecticut-based science writer and editor and a regular contributor to Live Science. She also has several years of bench work in cancer research and anti-viral drug discovery under her belt. She has previously written for Science News, VerywellHealth, The Scientist, Discover Magazine, WIRED Science, and Business Insider.