During the Archean Eon—roughly 4 billion years ago—the Earth was a lifeless planet. The atmosphere lacked oxygen, and there were few, if any, organisms to be found anywhere on the globe. Then something incredible happened. Microscopic bacteria appeared in freshwater lakes, likely in what is now present-day Australia. These bacteria—known now as cyanobacteria—had the near-magical ability to convert sunlight and water into oxygen and other chemical energy. ...read more read less