The best time to go back to would be Pangaea. I'd cough up phlegm, puke up bacteria, torch random things, it'd be great. Since my ability to timetravel makes the development of it a set point in spacetime, nothing I do can alter the fact that I came back to do those things, meaning humanity will eventually flourish, but I can fundamentally re-roll all of history from the era of the Precambrian.
The best time to go back to would be Pangaea. I'd cough up phlegm, puke up bacteria, torch random things, it'd be great. Since my ability to timetravel makes the development of it a set point in spacetime, nothing I do can alter the fact that I came back to do those things, meaning humanity will eventually flourish, but I can fundamentally re-roll all of history from the era of the Precambrian.