What can fossils tell us about the history of the Earth? Objective Students will learn the extent of Earth’s history and how life has evolved throughout the geologic timeline. Background Scientists have estimated that the Earth is 4.6 billion years old. During the first billion years of Earth’s history, life was completely absent. It was not until about 3.6 billion years ago that the first life form appeared on Earth. Colonies of single cell cyanobacteria are the first life forms that appeared on Earth. They formed algal mats and nodules called stromatolites. Stromatolites are therefore the fi Duration: 60 Minutes.