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Lying just within Yoho National Park are several small rock outcroppings collectively known as the Burgess Shales. These fossil bearing layers of rock have forced scientists to completely revise many of their theories on the evolution of life. So unique and vital were the discoveries at this site that it was designated a World Heritage Site by the United Nations.

Discovered by Charles Walcott in 1909, it is one of the only sites in the world where soft bodied animals left almost perfect fossils. This may not seem important until you realize that most of the study of early life is the study of hard parts--trying to learn something about an animal from a mold of it's shell. This tells us little about what lived inside the shell. This quarry uniquely preserved a huge variety of soft bodied creatures along with their shells. For the first time we could see the whole picture. How did this level of preservation occur? Scientists believe that a mud slide came down into a shallow bay and then washed the animals caught in its flow down into the oxygen poor depths far below. Since oxygen is a major factor in decay, this strange incident allowed the soft bodied animals to remain for a long time before disappearing--long enough to leave their remains fossilized.

The other unique factor of this quarry lies in the timing of this tragic slide. It occurred in middle Cambrian times, basically around 550 million years ago. This puts it right in the middle of the greatest explosion of life in the history of the planet. The Cambrian was the first period in which multicellular life exploded, and within a geologic blink of the eye, the world was populated with a diversity never before (or since) experienced. In no other fossil site on the globe can scientists match the high level of preservation of this site along with such excellent timing. There are a few other important Cambrian sites in other parts of the world, but they are much more recent and as a result don't show nearly the diversity found in this site.

As Walcott began to grapple with the significance of this site as a fossil bed, he began to collect, ravenously carrying tens of thousands of specimens back across the border. At the time, he was one of the most powerful scientists in the U.S. and this would be his greatest discovery. Over the next 18 years he would publish small preliminary works on the fossils but he never found the time to truly study them and unravel their true significance.

In the small amount of actual study of the fossils that he completed, he tended to group them according to the same groupings of animals present on the planet today, and although this may seem a natural conclusion, it would become his greatest error. Many of the animals present in the Burgess Shales, would eventually be found not to be part of any group of animals present on the planet today. 

Harry Whittington, one of Walcott's successors slowly began to unravel the true mysteries of the Burgess by careful and thorough examination of the multitude of fossils left behind. One of the techniques used by Whittington to carefully rebuild the creatures of the Burgess Shales was to slowly dissect the actual fossils. Like living beings, even though crushed flat, the fossil remains retained most of their original structure and by carefully removing micro-thin layers, one by one, Whittington was able to make much more detailed examinations of each specimen.

Whittington began in 1971 with a creature called Marella. This animal was clearly an Arthropod (the group of animals containing all the insects, spiders and crustaceans as well as the extinct trilobites) but he found that it didn't fit into any of the major grouping of Arthropods known to exist today. His next specimen Yohoia led him to a similar conclusion--it was an arthropod but of no known group.

Moving onto Opabina, he received his biggest surprise to date. This creature didn't fit into any group of animals known on the planet. The Arthropods are one of around 25 or 30 known phylums and all living creatures found on the planet fit into one of these major groupings. Further examination of some of the other residents of the shales led similar conclusions. These were creatures that could not be classified based on todays system of scientific terminology. Never before, at any other fossil site in the world, had fossils been found that could not be classified. This would have far reaching consequences.

Most standard discussions of evolution show a single primitive ancestor giving rise to a wide variety of future species. As a result we expected there to be less diversity early in the history of life--not more. In actual fact, what we have found is that there were many more basic structural plans at the beginning of life than today. This is contrary to standard discussions.

Survival of the fittest may be invoked to say that these early animals were merely inferior and failed to survive. However, survival of the fittest should be predictable and scientists could not find anything that would indicate inferiority in these unclassifiable animals. This has led to the theory that evolution may have another component--luck. Perhaps many of the extinctions were merely based on some environmental of otherwise unpredictable fluke, and as a result, animals not inferior in any way ended up perishing.

The long term results become very interesting indeed. If chance plays a major role in the extinction of species, than perhaps if we were to turn the clock back in time an entirely different outcome could arise. This could in turn change the entire sequence of events following this particular event--and could have even changed the eventual evolution of man. We may have never evolved! This does bring a whole new view to evolution. This chance factor is known as contingency and is being widely accepted as a valid aspect of evolution today--and all because of a tiny quarry in Yoho National Park.