Early life may have breathed oxygen earlier than believed

MIT geobiologists have found evidence that aerobic respiration evolved hundreds of millions of years before the Great Oxidation Event 2.3 billion years ago. By mapping enzyme sequences from thousands of modern organisms onto an evolutionary tree of life, researchers traced the origins of a key oxygen-using enzyme to the Mesoarchean period (3.2–2.8 billion years ago). This finding may explain why atmospheric oxygen didn't accumulate until much later — early organisms near oxygen-producing cyanobacteria likely consumed the oxygen as fast as it was produced.