Ancient microbes may have used oxygen 500 million years before it filled Earth’s atmosphere

Life on Earth may have learned to breathe oxygen long before oxygen filled the skies. MIT researchers traced a key oxygen-processing enzyme back hundreds of millions of years before the Great Oxidation Event. Early microbes living near oxygen-producing cyanobacteria may have quickly used up the gas as it formed, slowing its rise in the atmosphere. The results suggest life was adapting to oxygen far earlier — and far more creatively — than once thought.