The Earth was already more than 600 million years ... is not unlike one of the first life forms that appeared in the Precambrian era. Photograph by Joel Sartore, National Geographic Photo Ark ...

The Precambrian encompasses 86 percent of the history of Earth. As its name implies, this includes all of geological time prior to the Cambrian period. Hadean Era (4,550-3,850 mya) The Precambrian ...

Paleontologists now know that the Precambrian actually did swarm with ... Any sedimentary rocks that formed before life appeared on Earth would have the high C-13 ratio of a volcanic origin.