Earths Original Oxygen Catastrophe

Over two billion years ago, life on Earth triggered an accidental mass extinction by releasing oxygen into the air. This toxic gas, now vital for us, poisoned the anaerobic organisms that dominated the planet at the time.

Long ago, most life forms thrived in a world without free oxygen. When cyanobacteria evolved to harness sunlight, they pumped out oxygen as a byproduct that proved lethal to almost everything else living then. This massive environmental shift is sometimes called the Oxygen Holocaust because it permanently altered the planet’s chemistry. It essentially cleared the stage for complex life to evolve, proving that one organism's waste can change the course of history.