I've been reading Monster of God, by David Quammen. It's pretty interesting- he explores the effect that man-eating predators have on culture and the human psyche. In the section on bears (my favorite!) he talks about how the classic heroic literature such as Beowulf, or the Epic of Gilgamesh, though dealing with mythical themes, heroes and monsters, may not have been all that fantastic (in the sense of, just fantasy) for their contemporary audiences:

No one can prove just how much Grendel and Fafnir and Grendel's mother (charging ferociously, enraged by the death of her cub) owe to the real physical presence of the brown bear, and I don't propose to try. But it's interesting to remember that the old dark woods weren't empty of inspiration.

Can you imagine grumpy ole Grendel as a grizzly?