This thread brought up a memory of a time travel short story.
I hope it still exists in this timeline!
Some scientists invent a time machine and someone goes back in time to the far past and makes a small change, and it causes changes in the present (no, not ‘A Sound of Thunder’, but similar in some ways).
They try to work out if anything has changed or not, but each time they go back the changes only get worse. They try a few times, and in the last paragraph of the story the scientists are now all blue octopus-like creatures, but they agree with each other that nothing has changed, everything is exactly the same as it always was.
Can anyone identify it?