Shapeshifters

1. What's the basis for shapeshifters in pagan mythology and folklore? Are they purely figments of the imagination, which undergo further embellishment, or do they have analogues in reality? 

The werewolf character is the best known example, popularized by Hollywood, but I believe that's a part of some American Indian lore. Not sure how widespread that is, and whether that reflects independent traditions or cultural diffusion.

Is that just a legend, or does witchcraft enable practitioners to become animals? If so, do they retain human intelligence in that condition, or have animal psychology? 

2. This isn't confined to mythology and folklore. The cherubim in Ezekiel's theophanies are tetramorphs. Is that physical, or an optical or telepathic illusion?

What about the hybrid monsters in Daniel's visions? Are those merely artificial symbolic constructs? Or is there something analogous in reality that gave rise to the imagery? 

3. In some narratives, angels seem to have the ability to materialize, dematerialize, or even assume the form of human males. How deep does that go? Complete internal anatomy?

An alternative interpretation might be that angels don't have the power to assume human form; rather, they have the power to possess human bodies. If demons can do it, why not angels? Perhaps some descriptions involve angels taking possession of human males as temporary vehicles to perform a particular mission, then releasing the host after the mission is completed. 

4. On a natural level, the closest thing to metamorphosis might be male sexual arousal, which involves a degree of physical and psychological transformation, although nothing like shapeshifters. Human beings are composite entities: ensouled animal bodies. Male sexual arousal taps into something wild and primal. And that doesn't require an evolutionary explanation.

5. A more clear-cut example is the snake magic in Exodus, where the staff of Moses becomes a snake and vice versa. The Egyptian sorcerers are able to duplicate that feat. There is a naturalistic explanation for what the Egyptians sorcerers do, but for reasons I've stated elsewhere, I find that unconvincing.