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 ...

Paleontologists now know that the Precambrian actually did swarm with ... However life got started, it had to have been in full swing by the time it left its mark in the Greenland rocks.

A lot has happened in that time. Earth formed and oxygen levels rose in the foundational years of the Precambrian. The productive Paleozoic era gave rise to hard-shelled organisms, vertebrates ...

The alternating layers of rust-colored and gray deposits suggest oxygen production fluctuated over time. As underwater chimneys called deep-sea vents release dissolved iron into Precambrian waters ...