They first determined that polar bears and brown bears diverged less than 500,000 years ago. That's incredible, considering that prior theories estimated the two species parted evolutionary ways up to 5 million years ago.
Video: Why Polar Bears Don't Hibernate
"In this limited amount of time, polar bears became uniquely adapted to the extremities of life out on the Arctic sea ice, enabling them to inhabit some of the world's harshest climates and most inhospitable conditions," the study's senior author Rasmus Nielsen, also of UC Berkeley, said in a press release.
Up to half of the body weight of polar bears consists of fat, and their blood cholesterol levels are high enough to cause cardiovascular disease in humans.
Nielsen and his team, however, discovered that mutations in genes involved in cardiovascular function allowed polar bears to rapidly evolve the ability to consume a fatty diet without developing high rates of heart disease. One such gene, called APOB, is known to play a role in moving cholesterol from the bloodstream into cells, thus reducing the risk of heart disease.