One of the earliest great extinctions in Earth’s history may have been caused not by an asteroid or a volcano but by oxygen itself, when tiny photosynthetic microbes slowly filled the air with a gas that was poison to much of the anaerobic life that ruled the planet long before us

Around 2.4 billion years ago, the air over Earth began to change. Microbes in the oceans, the cyanobacteria, had been running a chemical reaction that split water and released oxygen as waste. For a long time that oxygen was mopped up almost as fast as it was made. Then the sinks filled, and it began [...] The post One of the earliest great extinctions in Earth’s history may have been caused not by an asteroid or a volcano but by oxygen itself, when tiny photosynthetic microbes slowly filled the