Our world had oxygen 700 million years earlier than we thought

About 2.3 billion years ago, Earth underwent what is known as the Great Oxidation Event, as early lifeforms photosynthesized enough oxygen that the gas took hold as a dominant part of our atmosphere. This massive shift allowed for the evolution of pretty much all complex life... but its roots go back far earlier than… » 9/29/13 4:00pm 9/29/13 4:00pm