Why does it fluctuate to 300ppm ~300k years ago?

A secret ancient civilisation lost to time that also had internal combustion engines. I think Graham Hancock wrote a book on it.

> I think Graham Hancock wrote a book on it.

Just popped up on my news feed, "Archaeologist braves the Joe Rogan podcast to counter Graham Hancock's nonsense":

* https://boingboing.net/2024/04/19/archaeologist-braves-the-j...

Episode in question, "Joe Rogan Experience #2136 - Graham Hancock & Flint Dibble":

* https://www.youtube.com/watch?v=-DL1_EMIw6w

(Entire episode is 4h26m long: I don't have to interest/patience for that personally.)

> (Entire episode is 4h26m long: I don't have to interest/patience for that personally.)

You can watch 70 minutes of another youtuber reviewing the debate:

https://www.youtube.com/watch?v=haKFyj-2OVw

https://www.youtube.com/watch?v=P1_u8N53utw

It looks a little bit periodic before we showed up. If it is random with some periodic tendency, I guess we don’t need a particular justification for the highest peak, right? One has to be. It isn’t massively higher than the previous peak.

Volcanism, most likely.

I don't know, I wasn't there. How old do you think I am?!

Just kidding. I suspect that's an interglacial when you have warming and melting but before the trees have grown back to recapture the co2. But check with an expert if you want a more authoritative answer.

I think is is pretty obvious: those were previous species that tried to become industrial, but were killed by Bigfoots. Humans, with our natural tendency toward absolutely slaughtering other species of large mammals, are the first species to escape the Bigfoot trap.