Precambrian time covers the vast bulk of the Earth's history, starting with the planet's creation about 4.5 billion years ago and ending with the emergence of complex, multicelled life-forms ...

During the Proterozoic era, oxygen produced by photosynthesizing bacteria collects in the oceans and then in the atmosphere. Iron present in exposed rocks reacts with this oxygen, and rust colors ...

Paleontologists now know that the Precambrian actually did swarm with living creatures, and it was swarming more than 3.85 billion years ago. The earliest evidence of life comes from the ...