Milton Lesser's "Prison of a Billion Years" (as by C H Thames) (short story, evolution, free): All life on earth is ultimately descended from...
Story is set on primordial earth - long before there is life here. I've a feeling the descriptions aren't quite accurate & time is certainly inaccurate, but that could be because the story is from 1950s.
Story summary.There is an ultimate jail - set on earth of a billion years ago, back when there was no life, seas were not yet salty, you never saw sun because of mist, etc.
And there is a condemned prisoner - Adam Slade, where "Adam" is significant, in Biblical sense. Hours before his execution time, he killed a guard, took a woman hostage, & escaped out in the wilds where no one can survive because there is no food. He has a desperate plan to take charge of the local time machine, & escape back to livelier times.
Story is mostly his travelogue on this primordial earth. He will be eventually killed by lightning near the sea coast, & claimed by sea. Of course, we're all descended from the bacteria & microbes that inhabited his body!
Fact sheet.First published: Imagination, April 1956.
Download full text from Project Gutenberg, Manybooks, Feedbooks.
Download audio from LibriVox (read by Mark Nelson).
Caution: Main Project Gutenberg page lists author as "Stephen Marlowe", but text has "C H Thames". I wonder if "Stephen Marlowe" is also one of author's pseudonyms?