Burgess Shale, British Columbia, Canada
A Paleontologist’s Heaven
Think of it as biology’s Big Bang.
About 542 million years ago, the earth’s most complex inhabitants were multicellular soft-bodied organisms. Then, over the next 20 million years, an extraordinary diversity of life-forms first appeared. Most of the phyla of the animals that now dominate the world got their start, including arthropods (ancestors of today’s spiders and crustaceans); annelids (worms); and the first chordates, the predecessors of all creatures with a backbone, human beings included. This burst of life (if an event lasting some millions of years can be described as a burst) is known to scientists as the Cambrian Explosion, the defining characteristic of the Cambrian period.
The Burgess Shale, a crumbling slope in Canada’s Rocky Mountains some 50 miles west of the resort town of Banff, is riddled with shrapnel from the Cambrian Explosion. This spot provided our first good look at the rich variety of organisms that flourished then. Though the site today is at an elevation of almost 7,500 feet, 505 million years ago it was a different place entirely. It was beneath the sea, for one thing, and much of today’s Canada was near the Equator. Violent underwater mudslides periodically engulfed the marine ecosystem, instantly killing all sorts of organisms—and preserving them as exquisite fossils. Whereas most soft-bodied animals decay before they can leave a permanent trace, the organisms at the Burgess Shale are so well preserved that, in rare cases, there’s evidence of gut contents.