I'd say that no, myths aren't based in reality though they are grounded in culture. As a good example, take the Coyote myths (I'm sure that nobody went tossing his eyeballs around as a result of what the birds said --just one of many hundreds of myths about him.) I'm quite sure that there wasn't a monkey or person who looked like a monkey who was born on a mountain and rose to become the king of a group of monkeys and who became a scholar.

Myths are explainations and moral lessons. It's the legends that are partly based on some truth (a true location, etc).
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You must be careful in assuming what is real and what isn't... you are seeing from a distance of thousands of years with incomplete knowledge.