Trekking through the Rocky Mountains on horseback one hundred years ago, Charles Walcott Doolittle stumbled upon a discovery that would forever change the understanding of the evolution of life on earth.

On August 30, 1909, Walcott found one of the most pristine fossils ever encountered. A marrella – a type of anthropod – complete with antennae. The discovery was evidence of the ‘Cambrian explosion’ which is classified as an event where more complex life forms began to take shape for the first time in history. Single cell organism were replaced, and backbones and complex muscle structure are seen for the first time, 500 million years ago.

The discovery led Walcott to dedicate his life to the exploration of the fossil bed – where he extracted 65,000 specimens for the Smithsonian, where he would later become curator. To date, 200 species from the Cambrian era have been identified from the Burgess Shale, making it the most prolific fossil site on the planet.

“Since the discovery in 1909, there have been other sites  - but it’s unparalleled the diversity and abundance of fossils. It’s really the most important fossil deposit in the world,” said Dr. Robert Gaines, a professor of geology with Pomona College in California.

One hundred years later, the Burgess Shale is still yielding new discoveries. In order to commemorate the anniversary of Walcott’s discovery, Parks Canada is re-introducing guided hikes to the area, and visitors are invited in groups of 12 to hike the 10 kilometres to the original site this year. Top paleantologists are gathering in Banff this week to discuss recent findings at the Burgess Shale, and similar sites in the Canadian Rockies.

According to Gaines, what makes the site so special is the level of preservation of life under the ocean 505 million years ago.

“The level of preservation requires some nasty conditions such as the absence of oxygen... The normal process of decomposition was arrested after a few weeks,” Gaines said.

The reason fossils were preserved and not crushed under layers of sediment is the presence of the Cathedral escarpment, according to Parks Canada Burgess Shale interpreter Claudia Harding. The escarpment bore most of the brunt of crushing limestone, preserving the fossils from a elimination.

Jean-Bernard Caron, associate curator of invertebrate paleontology at the Royal Ontario Museum is widely considered the world’s leading expert on the Burgess Shale. He and his team continue to hunt for rare specimens around the globe, however he says the Burgess Shale is the best site so far.

“It provides a better picture than geofossil record as it preserves body of animals that usually aren’t preserved,” Caron said, noting that often the animal’s last meal can be determined.

“We hope to find new species and want to find more specimens of very rare specimens. Now we have much more material. We are hoping to discover new Burgess Shale sites. If you find new sites, there’s a great chance to find new organisms elsewhere.”

Caron discovered a new predator in March, anomalocaris, with rows of teeth like a pencil sharpener and large claws used to shovel its prey to its demise.

The creatures do appear to originate from science fiction, which is a common comment.

“Some of the aliens from the first Star Wars movie in the Cantina scene were based on the Burgess Shale findings,” Harding said.

Caron said he sees similar excitement around these species.

“They excite the imagination. They show forms not seen in modern seas – organisms that aren’t close to anything we know. (But) the more we look at them, the more they aren’t that different. There are common features. For example, anthropods – organism that have jointed limbs. Today, that’s dominant in the seas,” Caron said.

He also said the first signs of humankind can be found in the Burgess Shale, specifically in the existence of backbones.

“Pikana, an organism no bigger than three or four centimetres – has a cord, - we share the same features. We can confidently say there is a common ancestor,” Caron said.

As for what’s next, Caron said new Burgess Shale-type sites should be discovered in order to better understand life 500 million years ago. There are about 50 other sites similar to the Burgess Shale, however Caron hopes to discover more.

“It may be the key to understanding evolution,” he said.