And cyanobacteria transformed the entire atmosphere, to such a degree that almost everything else died out: https://en.wikipedia.org/wiki/Great_Oxygenation_Even

And cyanobacteria transformed the entire atmosphere, to such a degree that almost everything else died out: https://en.wikipedia.org/wiki/Great_Oxygenation_Event https://en.wikipedia.org/wiki/Great_Oxygenation_Event