I think fermentation and radioactive beaches are my favorites. From a thematic perspective, I don't have the brains to actually have an opinion on whats most likely or correct.
Fermentation is funny & resonates with how fermentation is the most important chemical process to civilization
Radioactive beaches are nice if we ever manage to destroy all life in thermonuclear war, dust to dust, radioactive beaches to radioactive beaches.
edit: Creation Myths are acceptable
The Last Question is kinda that idea.I also remember reading a short story about something similar a while ago but I can't find it anymore so it could have been a writing prompt thing or something.
Maybe it was this, by qntm: https://qntm.org/responsibility
qntm is a great source of these type of stories. He writes for scp too.
Hey, that's definitely it. Thanks!