Not long ago I read some interesting theories regarding the origins of myths and legends. One fascinating theory states various ancient societies unearthed fossils while digging for stones to build their civilizations. The bones of long extinct animals perplexed the ancient people who then created imaginative stories to explain them.
For example, imagine you lived in ancient Greece and one day while hunting for food you come across this strange skull as large as your chest:
Well obviously, this must be from some large one-eyed creature with vicious teeth capable of rending a man in half:
(of course, since you live no where close to the Serengeti you wouldn't recognize a the skull as that of a dwarf elephant , complete with a large hole for the trunk, which lived on Mediterranean island until 9,000 years ago)
Similarly, if you came across a protoceratops skeleton (ie a triceratops without horns) you may assume it was an beaked creature the size of a lion with giant wings connecting to the frilly areas behind the neck.
Thus the griffin was "born".
Finally, if you lived in ancient China/South America/Europe/India/pretty-much-anywhere-thanks-to-Pangaea and you came across this skeleton larger than your house:
That must be a dragon (and not a Spinosaurus). Better call a knight to dispatch of him, and then eat his bones to claim his power.
Many of history's most fantastical stories have humble beginnings grounded in reality.