Fossils from 1.7 billion years ago reveal oxygen's role in complex life

Scientists studying Australian rocks found over 12,000 fossils belonging to some of Earth's oldest known eukaryotes. Ancient cells inhabited environments from coastal shallows to open ocean, but only where oxygen was available. In oxygen-free zones, only simpler microbes were found. The discovery strengthens the thesis that oxygen played a key role in the origin of complex life.