Someone last week went to the core of humans in the New Yorker.
It first discussed a game asking players to rank fantasy beings, not by whether or not they believe them to be real, but by the extent to which they seem as if they could be real. Those to be ranked included angels, demons, dragons, elves, ghosts, mermaids, unicorns, tooth fairy, Big Foot, unicorns, etc. People tend to rank them in a consistent way.
We can assume skills of tale telling were honed around campfires for 200,000 years. Further, we can assume these tale telling skills found their way into the written word in the recent few thousand years.
Around the fourth century, BCE, Aristotle mused about tale telling. He suggested writers of a tale “should prefer a probable impossibility to an unconvincing possibility.” That is, better for Odysseus to return safely with the aid of ghosts, gods, sea nymphs and a bag containing the wind than for his wife, Penelope, to get bored waiting for him and become a black smith.
For a being to be considered real it needs to be grounded in something the reader considers plausible–something he is familiar with. Disney knew this so his cartoon characters are always subject to gravity and have human-like features.
Tales about religion need to portray their god in a form familiar to the reader. That is why gods, i.e., Jesus, are depicted has having human-like appearances. This is Aristole’s “probable impossibility” and the Disney cartoon character’s human illusion.