Please forgive me if this has been posted before, but I tried the search engine, and no results for this came up. This has been around for a while, but is pretty historical. Around 1936 while Siegel and Shuster were still looking for publishers for Superman, Jerry actually enlisted the help of illustrator Russell Keaton to work on a proposed strip for Superman in which The Man of Tomorrow was literally
that! The last super-evolved survivor of a future Earth, who was sent back in time to survive! The strip didn't get past the origin story, and there appear to be portions of the script that were never even illustrated. But these restored versions show a very different backstory for the iconic character.
https://thoughtsandramblingsofhardwickebenthow.wordpress.com/man-of-tomorrow-siegel-and-keatons-superman/