In Search of the First Animals

In Search of the First Animals

Near the tops of some of the most remote peaks in the Canadian Rockies, well above the tree line, jagged limestone and shale rocks known as the Little Dal Group preserve the remains of 900-million-year-old reefs. Today the sun doesn’t fully set over the fossil reefs on summer nights—they lie just south of the Arctic Circle. But millions of years ago, these reefs grew in a tropical sea not far from the equator. The movements of tectonic plates la…