I can't pull the sources immediately from the back of my mind, but I have read some interesting conjectures by paleontologist/archaeologist/anthropoligist type researchers that throughout Asia Minor, Southern Europe, and the Middle East the exposed Mesozoic age rocks, with abundant dinosaur fossils, had to be at least partly responsible for ancient humans realizing that there was another world scene that existed before them at some time in the distant past.
It's not too hard to imagine that the dinosaur fossils gave rise to the myths about ancient monsters. And surely, if there were humans on the earth simulateously, they could not have been ordinary humans to deal with these ferrocious life forms, but rather the humans must have been imbued with great size or superhuman abilities or titanic mental power, etc., etc.....
Additionally, the Bible is replete with life forms (a la' Revelation, Daniel, Ezekiel) that, if explained genetically, would be considered mutant freaks.
Man-beast hybrids seem to be fairly common across cultures in artwork, literature, and oral traditions. The fact that the Bible comes out and explicitly condemns beasiality, at the very least, means that the writers were thinking about it.