There have been five great mass extinctions on this earth, and except for the last one, which was triggered by the asteroid strike that killed the dinosaurs, all have been the result of carbon dioxide flooding into the atmosphere and raising the temperature.
The oxygen one is before those big five.
I’d like to mention learning to handle abstract concepts in particular. This is why “hard” science graduates can do good in software engineering, because it also relies on juggling with a shitload of abstractions. I know someone who’s really good at solving practical and communication problems in daily life, but they didn’t finish highschool, and as soon as the discussion becomes abstract, their brain just blanks.