Scientists said the Thursday in journal Cell that the reason lies in their genes.
Some speedy evolutionary tricks, particularly in the genes which handle how fats are metabolized and how fats are transported in the blood, have allowed polar bears to survive in the Arctic, scientists said.
And it all happened within the last 500,000 years, after the polar bear split from its cousin, the brown bear, according to research that compared the two animals' genomes.
Scientists found that polar bears are much younger than previously thought, with past estimates of the divergence time between polar and brown bears ranging from 600,000 to five million years ago.
"It's really surprising that the divergence time is so short," said Rasmus Nielsen, a University of California Berkeley professor of integrative biology and of statistics
[via - natureworldnews.com]