Here's an update on that unusual bear that was killed by an American hunter- it was a grizzly/polar hybrid after all. No surprise there, polar bears are not very far removed from grizzlies on the evolutionary tree. In fact, there are grizzlies on Alaska's Admiralty Island that are genetically closer to polar bears than they are to mainland grizz.
Did you like how the article stated that "It was considered nearly impossible for the two species to mate, since polar bears mate on the ice, while grizzlies mate on land." I would presume this conclusion was drawn based on this quote from the earlier story:

"The probability of a grizzly and a polar bear mating is actually pretty low. Partly because polar bears mate on the sea ice and grizzly bears mate on the land."
(Dr. Ian Sterling)