Have you ever just looked in the sky and wondered if some bacteria from a world far off in the universe landed in the ocean mutated over eons to cause us to have the bodies we have today?
I read many years ago about a theory that small (house-sized) water-ice comets are continually hitting earth--and pretty much instantly vaporizing (theory was disputed then; may have been proven or completely debunked by now idk evidence was spotty at best).
The takeaway is the idea that all of Earth's water may have had extraterrestrial origins, and extraterrestrial water may be continually supplementing our atmosphere.
If that's true, who knows what else might be in those water-ice comets...
I had read that they found the potential for the existence of bacteria on a larger meritorite amino acid.
The Hollywood classic... "Body Snatchers"
It's a possibility? Not anything that has crossed my mind.