The Burgess Shale: A Fossil Find That Changed Our Understanding of Life on Earth

 In the early 20th century, Charles Doolittle Walcott stood at the pinnacle of American science. As a key figure in U.S. geology and paleontology—holding roles such as Director of the U.S. Geological Survey, Secretary of the Smithsonian, and President of nearly every major scientific body—Walcott’s legacy seemed complete even before his most famous discovery.

A Fossil Hunter at Heart

Born in 1850 in New York, Walcott never completed high school but was deeply fascinated by nature. He began his career selling fossils, which led him to a long tenure in geology and paleontology. In 1886, while working for the U.S. Geological Survey, he received a small batch of unusual fossils from Mount Stephen in British Columbia. His interest piqued, Walcott began summer expeditions to the Canadian Rockies that would span nearly two decades.

A Momentous Discovery

In August 1909, near the end of a field season, Walcott stumbled upon a trail on Mount Burgess littered with strange fossils. These were unlike anything he—or anyone—had ever seen. They dated back to the Middle Cambrian period, around 508 million years ago, and were preserved in fine-grained black shale as dark compressions.

Over the next several days, Walcott and his family, who often accompanied him in the field, collected numerous specimens. Although it was too late in the season to begin a full excavation, he returned the following summer in 1910, launching one of the most remarkable paleontological projects in history.

The Birth of the Walcott Quarry

Traveling on horseback through the rugged terrain of Yoho National Park, the Walcotts established a base camp near Burgess Pass and began excavating shale from a steep slope on Mount Burgess. The work was grueling. Fossils were pried from rock slabs using hammers and chisels, then carefully packed and transported back to Washington, D.C.

Over 14 years, Walcott’s efforts yielded more than 65,000 fossil specimens, many of which are now housed at the Smithsonian Institution. His 1911 publications introduced the world to bizarre and previously unimaginable ancient creatures.

Creatures from a Forgotten World

Walcott’s fossils included familiar organisms like trilobites, sponges, and mollusks—but also strange and enigmatic lifeforms. Among them were:

• Opabinia, with five eyes and a vacuum-like trunk.

• Marella, a segmented arthropod with delicate spines.

• Anomalocaris, a meter-long predator with barbed appendages and no modern counterpart.

• Hallucigenia, a worm-like creature so perplexing it was named for the hallucination it resembled.

• Wiwaxia, a spiny, armor-clad being possibly related to mollusks.

Many of these creatures could not be classified within any known group at the time. Walcott attempted to fit them into modern taxonomic categories—what we now call crown groups—but he was wrong.

The Crown and the Stem

Walcott’s major oversight was his assumption that the fossils belonged to modern animal lineages. In truth, many of them were stem group organisms—early evolutionary experiments that branched off before the ancestors of modern species had fully evolved.

For example, modern arthropods (like insects and crustaceans) share four key features: a chitinous exoskeleton, molting, segmented bodies, and segmented appendages. Fossils from the Burgess Shale may possess some but not all of these traits, placing them lower on the evolutionary tree.

Rediscovery and Reinterpretation

It wasn’t until the 1960s–80s that a new generation of paleontologists—such as Harry Whittington, Simon Conway Morris, and Derek Briggs—revisited the Burgess Shale with fresh eyes and new tools. They unearthed additional fossils, established new quarries like the Raymond Quarry, and reshaped our understanding of early animal evolution.

Today, much of the fossil work is managed by the Royal Ontario Museum in Field, British Columbia, and the Burgess Shale is protected as a UNESCO World Heritage Site. Collecting fossils is strictly prohibited without special permits, with heavy fines imposed on violators.

Why the Burgess Shale Matters

The Burgess Shale is more than just a collection of odd creatures. It offers an unparalleled view into early animal life and evolution, for three key reasons:

1. Exceptional Preservation: It's a textbook example of a conservat-Lagerstätte, a rare site where even soft tissues like eyes, guts, and muscles are fossilized in exquisite detail.

2. A Complete Community Snapshot: Unlike most fossil records, which preserve only hard parts (like shells), the Burgess Shale captures an entire Cambrian marine ecosystem—including algae, soft-bodied worms, predators, and even early chordates.

3. Morphological Disparity: The fossils demonstrate a dizzying array of body plans and evolutionary experiments. Some, like Anomalocaris, have no modern analogues. Others, like Hallucigenia, were so bizarre they were originally reconstructed upside-down.

These fossils have spurred a wealth of research into Cambrian paleoecology: How many species lived there? What roles did they play? Which were benthic (seafloor dwellers) or nectonic (swimmers)? Which were prey or predators?

A Snapshot of Evolution in Motion

The Cambrian period was a time of explosive evolutionary experimentation. In just 10–20 million years, life diversified rapidly. Some species, like Hallucigenia, were evolutionary dead-ends. Others became ancestors of modern animal groups.

The Burgess Shale captures this experimentation in full: strange, beautiful, and utterly alien. It helps us understand not just what life looked like 508 million years ago, but how it became what it is today.

Though Charles Walcott could not have known the full implications of his discovery, his tireless work collecting and describing the fossils laid the foundation for a scientific revolution. His legacy continues to shape our understanding of the history of life on Earth.