Photograph by Joel Sartore, National Geographic Photo Ark The earliest multicelled animals that survived the Precambrian fall into three main categories. The simplest of these soft-bodied ...

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 ...

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 ...