The Precambrian Era

The Precambrian Era covers about 88 percent of Earth's entire history! It stretches from when Earth formed 4.6 billion years ago to about 541 million years ago. For most of this time, the only living things were tiny microbes. It was a very different world from today.

A Young Earth

When Earth first formed, it was a ball of hot, melted rock. There were no oceans, no air to breathe, and no life at all. Slowly, the planet cooled down. Water vapor in the air turned to rain and filled the first oceans. The first simple life appeared about 3.8 billion years ago.

First Life

The first living things were tiny microbes too small to see. Some of these microbes learned to make oxygen through photosynthesis. Over billions of years, they filled the air with oxygen. Near the end of the Precambrian, the first animals appeared. They were soft, strange creatures unlike anything alive today.

Fun Facts

• The Precambrian covers about 4 billion years — almost 88% of Earth's history.
• The first life on Earth was bacteria, which appeared about 3.8 billion years ago.
• Earth was hit by so many asteroids early on that the surface was a sea of melted rock.

Did You Know?

During the Precambrian, Earth was once almost completely covered in ice! Scientists call this "Snowball Earth." It happened about 700 million years ago, and ice may have reached all the way to the equator.