The Great Oxygenation
The primordial atmosphere of the earth didn’t contain Oxygen (O2). The atmosphere was a “reducing atmosphere”, the exact opposite of today’s “oxidizing atmosphere”. Somewhere along the line life evolved. Single-celled organisms. Weirdos by today’s standards. Methanogens and sulfate-reducing microorganisms. That was just life for a couple billion years. And then chlorophyll evolved. Chlorophyll changes everything. …