Since soon after our planet formed, Earth’s 4.6 billion-year-long history was dominated by single-celled life. Something dramatic happened about 500 million years ago called the Cambrian “explosion,” during which an incredible diversity of life forms became preserved in the rock record. These fossils included major groups of diverse animals that evolved into animal groups still living today (including humans). Since soon after our planet formed, Earth’s 4.6 billion-year-long history was dominated by single-celled life. Something dramatic happened about 500 million years ago called the Cambrian “explosion,” during which an incredible diversity of life forms became preserved in the rock record. These fossils included major groups of diverse animals that evolved into animal groups still living today (including humans). Earth Sciences Phys.org – latest science and technology news stories