Grizzly Bear Evolution into Polar Bears
Polar bears evolved directly from grizzly bears. The polar bear evolved recently (in geological time) and the two species have even been known to mate in present day. The photo above shows a grizzly bear with striking polar bear like traits. He has a long neck which helps keep the nose above water while swimming and very small ears which reduces loss of heat. Since polar bears do not hibernate through winter like grizzlies, they have evolved traits like small ears and fur covered paws to conserve precious body heat.
The photo below shows one of the white/blond grizzly bears that inhabit the coast of Alaska. It is easy to imagine how blond bears and bears with long necks would be more successful hunting for seals in the water and on white ice like the polar bear. Over time, grizzlies with these traits evolved into the white, long necked, smaller eared polar bear.