Ice Age Extinctions and Dino-Plagues

October 21, 2009

About a year ago Dr. Bakker wrote a post about the different extinction periods that killed off the dinosaurs, mammoths, and saber-tooths. Recently, one of our readers asked some very thoughtful questions. R. Richards asks,  “How long would it take for this lethal concoction of plagues to do significant damage to a variety of species? Even with multiple pathogens and mutation allowing cross species infections it would have to take quite some time for this scenario to run its course among all of the different fauna.” (To see the full comment, click here.)

Dr. Bakker has taken this opportunity to write a follow-up blog, and hopefully answer any more questions that our faithful readers might have.

Thanks for the nuanced and provocative thoughts about dino-plagues and dino-extinctions.

I’ll discuss the time-line of extinctions first. Then, in a follow-up blog, I’ll talk about body size and rebound after an extinction.

The question here is: When dino-style extinctions happen, do the die-offs occur everywhere in the world at the same time?

Creative Commons License photo credit: Javier Paredes

The most recent extinction event is the Ice Age die-offs, and these extinctions do offer help in interpreting the terminal Cretaceous disaster among dinosaurs. The “Asteroid Theory” predicts that extinction should happen almost instantly – in a matter of weeks or months after the impact. We have an excellent fossil record for what happened when a land bridge permitted exchange between North and South America just as the Ice Age began. South America had been an isolated island continent that evolved its own unique large herbivores and carnivores, very different from what North America had. If the Immigrant Plague Theory works, we should see episodes of extinction that coincide with episodes of mingling of faunas, North and South.

We do. The first pulse of die-off happened when North American mammal carnivores began to invade South America, towards the end of the Pliocene about 3 million years ago. The South American native carnivores suffered right away. The giant carnivorous ground birds died out almost completely and the giant marsupial predators disappeared. The invasions were not all one sided. Some South American herbivorous maxi-fauna did invade North America – giant ground sloths came up in great abundance. And one species of killer ground bird made it to Florida.

Creative Commons License photo credit: BryanKemp

A second pulse happened as mastodons, deer and other Northern large herbivores invaded South America. Several native South American herbivore clans disappeared.

The third round of extinctions happened 15,000 to 10,000 years ago, when all the native South American big mammals went extinct. Humans entered South America about this time. At the same event all the biggest invaders too died out – gone were mastodons and saber-tooth cats that had come across the Panama land bridge from the North. In North America, the saber-cats, mastodons and mammoths died out along with the ground-sloths that had invaded from the south.

The entire Ice Age extinctions, world wide, took over three million years. They did not happen all at once, everywhere.

Creative Commons License photo credit: gwenturnerjuarez

The final dino-die offs were also complicated. You see the beginning of the crash in North American diversity about 72 million years ago, in the Horseshoe Canyon Fauna. Only a very few big dinosaurs have large numbers. In the Lancian Fauna, 67 to 65.5 million years ago, we still have some dinosaurs but only two herbivores are common: Triceratops and Edmontosaurus. Then, at 65.4 million years ago, all the remaining big dinos go extinct.

These pulses of dino die-offs probably coincide with pulses of faunal interchange among the continents.

Conclusion: the Cretaceous dino extinctions were complicated in time and space. They did not happen suddenly all over the globe.

Authored By Bob Bakker

The Museum’s Curator of Paleontology, world-renowned Dr. Robert T. Bakker (or, as some call him, Bob) is the leader of the handful of iconoclastic paleontologists who rewrote the book on dinosaurs three decades ago. Along with other noted paleontologists, Bakker has changed the image of dinosaurs from slow-moving, slow-witted, cold-blooded creatures to — at least in some cases — warm-blooded giants well-equipped to dominate the Earth for 200 million years. Dr. Bakker can be found all over the globe, notably leading the Museum’s paleontology field program.

6 responses to “Ice Age Extinctions and Dino-Plagues”

  1. Jay says:

    I’ve long had issues with the ‘Asteroid Theory’…mostly on the grounds of how many species survived such a cataclysmic event.

    Why do think that the Asteroid Theory has gained so much traction among scientists and the public?

  2. Erin F says:

    Hi Jay,

    Dr. Bakker is in the field digging right now, so it may take some time for him to post a response here. Just wanted to let you know – and thanks for reading!

  3. Erin F says:

    Hi again! Here is Dr. Bakker’s response to your question:

    “‘Why do otherwise sober-minded folks like the “Extreme Asteroid theory of Extinction?’

    Geologists long have looked to physical, not biological catastrophes for extinction agents. Back in the 1830’s, Serial Creationists viewed life as having come through many successive layers of creation. The Jurassic layer was followed by an extinction, then the Cretaceous layer of Creation occurred. New species were created with each layer; old species went extinct. Shifts in climate were the culprit, the agents of die-off, so they thought.

    Darwinian geologists too saw climate as a fauna-killer. Sudden changes in heat and humidity would wipe out whole ecosystems. There simply was a preference for external causes coming from outside the actual biotic systems.

    Few were the scholars who searched for extinction agents right in the critter-critter interactions themselves. Exception: H. F. Osborn, who was the first to suspect immigrant mammals as carriers of diseases that exterminated many waves of large furry species in the Tertiary.

    Now, in the age of “Star Wars”, “Star Trek” and successful NASA explorations, it’s just human nature to prefer visions of astral collisions to scenes of T. rexes dying of explosive diarrhea.

    ……but diarrhea is proven to be a super-deadly killer, of both non-human species and humans themselves.”

    Thanks again for reading!

  4. Jay says:

    Thank you Erin and Dr. Bakker for the prompt and remote response!

  5. Gaston says:

    Years ago I heard an interview where the professor R.T. Bakker said that Comet was not responsible for the extinction of the dinosaurs, if the asteroid had been responsible for the extinction of the dinosaurs, turtles and frogs also had to be extinguished.

    Your answer agrees with my experience, frogs and turtles in general do not survive small changes in temperature or conditions of their niches, we can now confirm what is happening to the frog “Arlequin” in Costa Rica.

    I don’t know the challenges in the past on the route of our solar system, perhaps the murderer is one or more asteroids or perhaps there are areas of the galaxy with large amounts of interstellar dust that periodically cools the planet.

    These conjectures unfortunately not explain the presence of a selective murderer. The extinction caused by periodic cataclysms, every 80 million years, they should first affect the frogs and turtles.

    I read an article from the BBC’s Jana Beris published on MSN. The article was written about an Israeli company (Nucleix) has developed a system for detecting whether the DNA sample is genuine or not.

    The article explained that DNA samples can be duplicated, however the copy is missing an enzyme called “metyl CH3 “, therefore there are limits to the process of DNA replication; the process of cell division, are also limited by telomeres.

    Telomeres do not play in the processes of DNA duplication, that causes the DNA polymerase in each new duplication is diminishing their ability to copy all the genes on a chromosome, until it can no longer duplicate it.

    Telomerase is present in protozoa, plants, insects, roundworms, mold, fungi, other vertebrates such as mice, life forms, including us, are descended from protozoa.

    There are genetic limitations to cell reproduction, which determine our death. I wonder if there may be in the genetic code, instructions for the degradation and ultimate extinction of one or more species.

    Of course I cannot make a rude and arbitrary amphibology such data. But I think the role of genes in the processes that cause a mass extinction and then I can explain the survival of frogs and turtles.

    Thanks for reading.

    Gaston Velasquez

  6. Paula Crook says:

    In the early 1980’s, two hypotheses were introduced in regards to the dinosaur extinctions..the first, that an asteroid struck the earth, was based on rare elements found in the KP Boundary layer (Alvarez, 1980) that has now been found all over the globe…the second, that massive amounts of lava erupting onto the Indian plate (Deccan Traps) would have increased CO2 levels in the atmosphere, thereby causing the extinctions (McLean, 1981). These two hypotheses have gone back and forth for over 20 years now. When a piece of evidence does not fit one event, it is assigned to the other, leading scientists today to claim that it must have been both together.
    However, many of the scientists that are studying the extinctions are biologists and paleontologists who are not studying plate tectonics. On researching causes of extinction, one of the main elements that seems to be overlooked time and time again is what was happening on earth at that particular time. The theory of plate tectonics is relatively new in the field of sciences. Only since the 60’s have we known about mid-ocean ridges and subduction zones. Our ideas of what the earth is capable of are still evolving.
    In 1996, Dr. Charles Officer and Jake Page wrote a book entitled The Great Dinosaur Extinction Controversy. In their book, they showed how not only were the Deccan Traps occurring in India, but also, that large magmatic and uplifting events were also occurring in North America that were not only coeval with the extinctions, but also with the uplifting of the Laramide Orogeny and the disappearance of the Western Interior Seaway. Not only did habitats become fragmented and disrupted, but an entire biosphere disappeared as the peaceful bays and estuaries of that sea were replaced by mountains, volcanoes, and large igneous provinces.
    So then what I wanted to know was…could an asteroid strike have caused some sort of disturbance in the mantle that would account for the large magmatic and uplifting events that were occurring on opposite sides of the planet at the same time as the extinctions? The answer to that was clearly NO as the uplifting was occurring hundreds of thousands, if not, millions of years before the asteroid supposedly hit. So, then, what DID cause that uplifting and magmatism on opposite sides of the globe? The answer…plate tectonics….
    I am also introducing a new theory on what really killed the dinosaurs. For those who might be interested, I gave a presentation at the GSA Annual meeting in Houston in 2008. ( And, at the GeoLaramide Symposium in Mexico this year.
    Thank you for listening,
    Paula Crook

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