In 1800, there were 1B humans, 1950 is 2.5, 1990 is 5.0B, and we are now at 8.0B.

I think we forget how many more people there are now compared to just 100 years ago. At -5000, there is an estimated 5M people. There's more than 1000x more people now. Per capita carbon footprint would be quite wild to leave any kind of mark on the planet with a total human population that is smaller than a single modern day mid sized city.

(Data is from worldometers.info/world-population)