Oxygen. Just google “air oxygen content historically” without the quotation marks, and be amazed how much you don’t know.
Humanity, life, evolved to a certain mix of conditions on Planet Earth, long long time ego. Billions of years? Long time.
Billions of dollars I may understand… 1-2-3 and I count to billions. But billions of years? So between 1 and 2 I have to wait a year? lol… I can’t fathom that. So a long long time ago is enough for me.
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