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GiveLife.ca

    
At least the dinosaurs had an excuse: Part 2

By Alanna Mitchell

Phil Currie is famous mostly for his work on theropods, the upright meat eaters such as the fearful T. rex, and he is much more interested in their heyday during the Cretaceous period than he is in their demise. But over the past 25 years, as he has mined the Alberta bone beds, he has uncovered many clues to the dinosaurs' mysterious extinction that he cannot ignore.

He casts himself back about 80 million years to a time when Dinosaur Provincial Park was a coastal lowland, a delta something like the mouth of the modern Mississippi. A sea covered most of Saskatchewan and Manitoba and the Gulf of Mexico went all the way to the Arctic Ocean. There were no polar ice caps and the mighty Rocky Mountains would not emerge for 15 million more years.

Alberta's climate was sultry, like Florida's today. Instead of scrub brush, there were forests of cypress trees and redwoods towering over lush ferns and some of the planet's first flowering plants. The air was heavy with the scent of magnolia.

The region not only supported a huge animal population, it was also well-suited to preserving them after death. Many died in water, allowing sediment to cover them and eventually produce fossils. But the bonus for modern science was the Ice Age.

People/Institutions
  • Royal Tyrrell Museum
  • Luis and Walter Alvarez
  • Conservation International
  • International Geosphere-Biosphere Program
  • Places
  • Dinosaur Provincial Park
  • Drumheller, Alta.
  • The Chicxulub Impact Crater
  • Science
  • How to volunteer at the Tyrrell
  • 3D-Cretaceous map
  • Climatic maps from the paleomap project
  • About the K/T boundary
  • Flip forward to about 12,000 years ago, when Homo sapiens was just emerging from its caves and the woolly mammoth roamed the land. As the glaciers retreated, they carved remorselessly through the landscape, peeling off hundreds of metres of geological beds to expose the glory of the dinosaurs.

    Currie points to a bald outcropping against the clear sky. And then another. They are rounded, as if a gigantic hand has scooped them into a sculpture. But the layers that run across these figurative outcroppings are set down with geometric precision - the black seam represents a mucky wet period in Alberta's past, the grey shows when forests covered the land, the sandy one is the residue of an epoch of fast rivers.

    Because these sequences are so precise, Currie can determine which dinosaurs lived when. The fossils tell him that 80 million years ago, at least 35 species lived in southern Alberta. Seventy million years ago, the tally had fallen to 20 to 25. And five million years after that - right before the asteroid hit - there were just six.

    "Whether you look at the big picture or the small," he says, "we are saying that there was a reduction in the diversity of dinosaurs over the last 10 million years - and that would suggest that, in western North America, something big is going on."

    Something like this: In the millions of years before the dinosaurs went extinct, the seas began to pull back from the continents. The Gulf of Mexico inched south, the Arctic Ocean north. Inland seas began to vanish in South America and Australia. As that happened, Currie says, continental climates were established for the first time in eons. That meant warmer days and colder nights. And even though the climatic change was gradual, many of land-living dinosaurs could not adjust.

    "The deterioration of the temperature doesn't have to be a lot," Currie says.

    Another clue to the dinosaur dropoff is the size of the ones that were left at the end. They were big and, strange as it may seem today, nature tends to favour big animals over small ones, if climate and environment remain stable. They live longer, are less active and need to eat proportionately less to survive. (As well as the dinosaurs, the world has seen a rhino that stood 18 feet at the shoulder, amphibians with skulls the size of a dining-room table, bisons the size of elephants, birds 10 feet tall.)

    But big creatures do not cope well with rapid change and the six dinosaur species still on the scene when the asteroid hit included the towering T. rex and hefty triceratops, and others that were among the biggest of their families. So not only was the gene pool thin, it was also a bit slow on its feet.

    To science, the point at which the asteroid fell marks the end of the Cretaceous Period and the beginning of the Tertiary Period, and is known as the K/T boundary. (The T is for Teriary and K is from "Kreide," which is "creta" in German.) Alberta's geological record of what happened at that time on land is most clear, but what it shows is baffling. For one thing, there are no dinosaur bones. If dinosaurs died en masse, where are the bones?

    "We know absolutely not a thing about the dinosaur at the boundary," explains David Eberth, a Tyrrell geologist and paleontologist. "I just about fell out of my chair last year when I realized that."

    This alone does not prove that dinosaurs were already extinct. But it does mean there is no proof, so far, that they were still alive. The record also shows quite clearly that Earth's climate had undergone a sharp change and was becoming more harsh. Quickly. Rapid change makes it difficult for life to adapt. Species were dying.

    Scanning the fossil-laden hills of the badlands, it is hard not to think of the incredible pace of today's climate change. Already, there is more carbon dioxide in the air than at any other time in three million years, the Intergovernmental Panel on Climate Change reported this year. Arctic Sea ice is 40-per-cent thinner than it was 40 years ago. Glaciers around the world are vanishing. Scientists believe that the pace is faster than what preceded the K/T boundary - the fastest, in fact, in Earth's history.


    The K/T boundary does not look all that remarkable. Dennis Braman, a specialist in plant microfossils at the Tyrrell, is holding a piece of it in his hands - a sliver of claystone sediment between one centimetre and two centimetres thick that is packed between layers of mudstone and coal.

    It represents perhaps a decade, an unimaginably small slice of Earth's 4.6 billion years of existence, but an unimaginably important one: a rare geochemical marker of a single point in time across the planet.

    Braman is one of the scientists who, leaping off Alvarez's findings, have taken the boundary apart molecule by molecule, spore by spore. A major surprise has been the astonishing amount of iridium - the so-called "iridium spike" - found along the boundary all over the world. Iridium is a very rare element - on Earth. Extraterrestrial bodies have lots of it.

    As well, there is "shocked" quartz (crystal is so finely fractured that it resembles miniature graph paper), a concentration of unusual primordial microdiamonds and an array of bizarre amino acids, all of which Braman says point to something falling from the sky.

    Above the boundary is between half a centimetre and two centimetres of what Braman calls an "impoverished zone." It should be a good spot to find pollens and other evidence of life - but hardly any is there to be found. "Something very major happened," he says. "But there seem to be other things happening before."


    No one knows better than a dinosaur scholar that extinction is normal. Phil Currie is no alarmist. But he has read first-hand the history of Earth. He has seen the calamitous results of rapid ecosystem change, has catalogued the imperatives of evolution. The parallels between then and now haunt him.

    He fears that humans are doing something no other plant or animal has done: defying the law of evolution. We have forestalled natural selection and unleashed our own series of extinctions. We have sidestepped the nasty effects of human evolution, but we have failed to cash in on the benefits of continual evolution. That means our sick do not necessarily die off, but we have not developed the biological nimbleness to adapt to new challenges.

    "Right now," he says, "we're blindly going along and destroying things and that could ultimately contribute to our own destruction. As long as things keep going like this, we really aren't doing much to ensure our own future."

    And not just our own. The future of thousands of other creatures that have survived the evolution wars of billions of years hangs in the balance. And the unknown ways they contribute to the functioning of the planet.

    Is he right? Has humanity really become what amounts to the fifth element? Some experts agree. "I can say, undeniably, that human actions are so profound that they equal the forces of nature," Will Steffen says from his office in Stockholm. A chemist, Steffen is in charge of the International Geosphere-Biosphere Program, which brings together a decade of research on how the natural world is changing.

    Asked whether the planet is robust enough to withstand the shock of human interference, he replies that it is hard even to tell where the point of no return is. "Can humans actually push the Earth into operating in a different state that's not suitable for human civilization? That's way beyond scientific enterprise."

    Modern researchers now believe that the ancients conjured up the notion of the griffin - the monstrous winged hound of Zeus with a lion's body and an eagle's head - after seeing bones of the protoceratops found in the Gobi Desert. Legend helped them make sense of a world they did not really understand.

    Today, however, there is no such escape in myth. Science has told us how species evolve and die out and the role Homo sapiens plays in that. And now, scientists such as Phil Currie are beginning to read the lessons the fossils have to teach, rather than relying on imagination.

    The question, Currie says, is what we make of it. "We do recognize our past. It's a very important advantage we should have. We think of more than just food and surviving - and that's something that definitely didn't go on during the Cretaceous.

    "But if things play out and we drive ourselves to extinction, then what do we really accomplish by doing things differently? Nothing." He shakes his head. The logic escapes him.


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