Get Out Of Town, Go Back In Time––

A Journey Of 500 Million Years Brings The Burgess Shale To New Haven

By Dottie Evans

Horatio: O day and night, but this is wondrous strange!

 

Hamlet: There are more things in heaven and earth, Horatio,

Than are dreamt of in our philosophy.

 

Anyone who has ever loved looking at fossils or wondered about what the earth was like long before the dinosaurs ruled, should take an afternoon to visit the Peabody Museum of Natural History in New Haven, just an hour’s drive away.

A special traveling exhibit titled “The Burgess Shale: Evolution’s Big Bang,” is on loan from the Smithsonian Museum in Washington, D.C., and will remain up until November 23. The Peabody Museum is open seven days a week including Veteran’s Day, November 11, and afternoon visits are recommended since the school groups usually go in the mornings.

A wealth of information is on display about life on earth 500 million years ago, and despite questions about what might have caused a sudden explosion of species during what paleontologists call the Cambrian Era, there is no denying the thrill of standing “face-to-face” with some extraordinary fossils from that time.

The exhibit’s storyboards and a 15-minute Discovery Channel video presentation inform the visitor about the ocean environment in which these amazing creatures evolved. They also tell about the pre-Cambrian era that spanned nearly two billion years earlier. Most likely, the earliest life forms from that earliest time were unicellular, made of soft tissue only. They floated freely, or they were stationary –– anchored to the ocean floor like ferns or simple sponges. No fossils have survived to tell us more.

Somehow, by an unexplained, evolutionary process that is still being debated by scientists, these simple, unicellular pre-Cambrian life forms were jump-started into a time of tremendous change, growth, and diversity that took place over a relatively “short” period of 15 million years within the Cambrian Era –– from 535 to 520 million years ago.

The causes behind this sudden “explosion of life” may not be clear, but the fossil evidence is stunning.

Now we see a new world of complicated-looking creatures beginning to fill up those warm, shallow Cambrian seas, hunting and being hunted, carving out their own ecological niches. They are mobile and many have developed some form of vision or sensory awareness. All manner of body types and appendages start appearing –– claws and jaws, tentacles and teeth, scales and tails.

The simplest worms begin to show evidence of a central nervous system encased in a spine called a notocord. Soft-bodied mollusks have developed hard shells to protect themselves, and lobsterlike arthropods are scuttling about on long, spiny legs.

These creatures are alien yet strangely familiar. That wormlike tube with the single spine (pikaia) might have been the first chordate from which the fishes, the dinosaurs, the birds, and the human species eventually evolved. The bug-eyed arthropod (anamalocaris) with the spiny foreclaws might have been the precursor of today’s spiders and lobsters.

Many of these bizarre creatures would become the ancestors of all earth’s zoological species that swim, crawl, fly, or walk through our world.

The Burgess Shale Fossils

 The first multicellular creatures evolved rapidly, each developing unique mechanisms for mobility, predation, and self-protection so that over vast periods of time, huge numbers of ecological niches in the world’s vast oceans are becoming filled.

Seeing the Burgess Shale fossils up close is like seeing a snapshot in stone taken long ago. Sometimes it is even possible to make out more than the usual hard parts, and the actual outline of the entire creature emerges. A dark, shiny film around spines or bones indicates where there might have been a stomach or a mouth.

Shale is rock composed of fine-grained sediment that was once a part of the ocean floor. The Burgess Shale, named after Burgess Pass nearby the site, is located in the Rocky Mountains of Canada in British Columbia. During the Cambrian Era before the continents drifted apart and took the positions we recognize today, this area was part of an undersea landmass near the earth’s equator.

A visitor to the Peabody Museum exhibit soon realizes that there has been a double miracle at work. Not only were the Burgess Shale fossils perfectly preserved by the chance catastrophe of an undersea mudslide overtaking them 500 million years ago, but the rock-hard substrate where they became trapped was somehow transported halfway around the earth.

Moved by continental drift and uplifted during mountain building, the fossil-bearing shale was scraped by glaciers and avalanches, eroded by wind and water, until it ended up in an outcropping high in the mountains of western Canada.

Such a transformation over so long a period of time is almost impossible to imagine.

By the strangest of circumstances, therefore, Cambrian fossils finally reached the light of day and were discovered in 1909 by Smithsonian explorer Charles Walcott. Working feverishly over several years, Mr Walcott collected more than 65,000 specimens, and he sent them back to Washington, D.C.

Subsequently, paleontologists from the Smithsonian, from England’s Cambridge University, and from Yale University have reexamined the Burgess Shale fossils and they are still making new discoveries about them. In particular, the fossils are being compared to similar deposits found in China and the west coast of Africa.

The Discovery Channel video, an important component of the Peabody exhibit, documents the chronology of the Burgess Shale discoveries and presents many of the creatures as they might have appeared in real life.

Through animation, we are able to watch while tiny, wormlike pikaia swims along the shallow ocean floor and hides among spongelike growths, or burrows beneath the sand. It has escaped from the ferocious anamalocaris creature that is passing overhead trolling in the shallows, its pincers poised for the kill, grinding jaws ready to crush it out of existence.

Then we can step out of the viewing room into the exhibit hall and look at the fossils themselves. We wonder whether it really happened that way. Maybe not, but something very like it or we might not be here.

The Peabody Museum is in New Haven at 170 Whitney Avenue, at the corner of Whitney Avenue and Sachem Street. It is one block north of the intersection of Whitney and Trumbull Street. Traveling north or south on Interstate 91, take Exit 3 onto the Trumbull Street connector and make a right turn at the second intersection onto Whitney Avenue, and follow posted signs to the Peabody Museum. Hours are 10 am to 5 pm, Monday through Saturday, and noon to 5 pm on Sunday. Admission is $7 for adults and $5 for children ages 3 through 18. Senior citizens 65 years and over are $6. Free admission on Thursday afternoons from 2 pm to 5 pm. Phone number: 203-432-3775.