Life on earth began over 3.5 billion years ago. Life became abundant on our planet about 570 million years ago (Ma). The time since life became abundant is called the Phanerozoic, which means "many animals."

The Phanerozoic is divided into three eras. The oldest is called the Paleozoic (which means "ancient animals"). The most recent era is the Cenozoic ("recent animals"), and the middle is the Mesozoic.