Could humanity be a recent visitor to this world? Are our true origins on some distant exoplanet?
The fossil record documents our purely terrestrial linage going back hundreds of millions of years. Humans are merely a recent flourish on the tetrapod body plan and suggestions to the contrary are manifestly nonsensical.
Still, no author in possession of a cool story idea ever hesitated merely because it constituted an egregious contradiction of firmly established science. Here are five examples of stories in which humans came from somewhere beyond the sky.