Your mind should boggle. It's all pretty amazing.

2.5 billion years ago the earth would have been uninhabitable to most modern life. Single celled life evolved in those conditions and began creating glucose and oxygen from CO2 and water. When those primitive lifeforms died some of them became oil and the CO2 was sequestered.

Over time the CO2 levels dropped until about 20 million years ago the CO2 levels fell to about 300ppm. That's when life as we know it really took off. Yes, it took BILLIONS of years to get there.

Humans have only existed for about 200k years. During that time our CO2 levels have mostly been below about 280ppm. The are now at 429ppm and are rising exponentially. [0]

[0] https://www.co2.earth/daily-co2