FROM 508 MILLION YEARS AGO TO TODAYPreserved in the Burgess ... to one of the deepest and most puzzling mysteries of life on Earth. After burbling along for more than three billion years as ...

But life emerged prior to that; we have fossils of microbes from 3.48 billion years ago. And scientists think that conditions on Earth may have been stable enough to support life from around 4.3 ...

Earth's magnetic field nearly collapsed some 590 million years ago, presumably putting life on the planet's surface ... Earth's magnetic field was strong. Roughly 1.5 billion years later it ...

About 800 million years ago, oxygen levels reached about 21 percent and began to breathe life into more complex organisms. The oxygen-rich ozone layer was also established, shielding the Earth's ...