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Science

Maybe It Wasn't The Meteor, After All 48

Posted by timothy from the all-hearsay-to-me dept.
An anonymous reader writes "In one new argument, David Penny of Massey University in New Zealand and Matt Phillips from the University of Oxford contend the fossil record and the evolution of animals through modern times suggest the demise of dinosaurs began several million years before the catastrophic asteroid collision. '"We agree completely with the geophysicists that an extraterrestrial impact marks the end of the Cretaceous," said Penny, in a statement reported in newspapers and on the Internet this week. "But after 25 years [scientists] have still not provided a single piece of evidence that this was the primary reason for the decline of the dinosaurs and pterosaurs."'"
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Maybe It Wasn't The Meteor, After All More

Maybe It Wasn't The Meteor, After All

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  • So finally my theory is proved correct (Score:3, Funny)

    by antifoidulus ( 807088 ) on Thursday October 14, 2004 @05:38PM (#10529820) Homepage Journal
    The Dinosaurs did die out because they invented, "Starbucks". It will happen to us too.....

  • Maybe It Wasn't The Meteor, After All (Score:3, Funny)

    by Anonymous Coward on Thursday October 14, 2004 @05:43PM (#10529863)
    It was the butler.
  • The dinosaurs were on there way out anyway. I always thought as a child when told these stories of extinction that they were never just fininshed off. Times were deffinatly hard for existing life at the time due to other circumstances e.g. volcanic activity, fluctuation in environmental circumstances affecting wildlife and of course food sources.

    The Earth was a lot younger then. I think it is a more acurate theory that a meteor Impact simply aided the final stages of extinction.

  • It was in fact..... (Score:3, Funny)

    by Andy Mitchell ( 780458 ) on Thursday October 14, 2004 @06:00PM (#10530019) Homepage

    As every fan of the classic science fiction series Doctor Who [bbc.co.uk] knows the Dinosaurs were actually wiped out when a star freighter impacted into the earth.

    This was all part of a Cyberman plot to destroy the earth. This story was also notable in that they finally managed to get rid of Adric, possibly the 2nd most annoying boy genius in the history of SciFi (just after Wesley Crusher). Adric had the decency to die heroically so avoided first place :-)

    For more information see the episode guide for Earth Shock [bbc.co.uk]

  • Non sequitur (Score:5, Informative)

    by Safety Cap ( 253500 ) on Thursday October 14, 2004 @06:22PM (#10530203) Homepage Journal

    People much smarter than you [ucla.edu] already determined that the K-T boundary is uniformly deposited (in terms of time) across the earth, no matter which craton you examine, and it occurs at the same point in time as a significant biomass die-off.

    This indicates that a extreme amount of dust and ash must've been airborne for many years, blocking much of the sunlight that would normally enable plant life to flourish. While it is entirely feasible that dinosaurs were in decline prior to this time, the event that killed them is the same one that ultimately created the K-T.

    • yeah, and populations go through declines with extinctions all the time. populations often fluctuate

    • Re:Non sequitur (Score:4, Insightful)

      by dasunt ( 249686 ) on Friday October 15, 2004 @01:04AM (#10532612)

      This indicates that a extreme amount of dust and ash must've been airborne for many years, blocking much of the sunlight that would normally enable plant life to flourish. While it is entirely feasible that dinosaurs were in decline prior to this time, the event that killed them is the same one that ultimately created the K-T.

      Oddly enough though, birds, mammals, reptiles, amphibians, and fish survived...

      Yet both the bird-hipped and regular-hipped dinosaurs died, pterodactyls were wiped out, and the marine dinosaurs also died.

      The meteor probably had a large influence, but I think the actual story is more complicated than "the meteor hit the earth and all of dinosauria decided to die, along with a few related species"

      • I think that the survival thing largely comes down to "dinosaurs big, other critters small" rather than being anything very complicated. Bigger critters would assumedly be more sensitive to disruption of their ecosystem since they have a much larger biomass to support; also being ectothermic probably really sucked what with many years of blocked sunlight and all. Turtles and such, on the other hand being much smaller, would have lesser requirements for survival and thus would have a much easier time adaptin

        • Re:Non sequitur (Score:3, Interesting)

          by dasunt ( 249686 )

          I think that the survival thing largely comes down to "dinosaurs big, other critters small" rather than being anything very complicated.

          The smallest sized dinosaur was chicken-sized, that we know of. A quick google search indicates that a larger crocodile survived the big extinction.

        • persistant indeed. life sucks doesnt it. and its an unfortunate thing us big creatures have a hard time dealing with it.
      • "This indicates that a extreme amount of dust and ash must've been airborne for many years, blocking much of the sunlight that would normally enable plant life to flourish. While it is entirely feasible that dinosaurs were in decline prior to this time, the event that killed them is the same one that ultimately created the K-T." Just adding to this point eveidence also suggests that their is no impact crater big enough to completly support a theroy of a meteor impact. Admitidly the Earth is mostly water. B

    • People much smarter than you already determined that the K-T boundary is uniformly deposited (in terms of time) across the earth, no matter which craton you examine, and it occurs at the same point in time as a significant biomass die-off.

      This indicates that a extreme amount of dust and ash must've been airborne for many years, blocking much of the sunlight that would normally enable plant life to flourish. While it is entirely feasible that dinosaurs were in decline prior to this time, the event that ki

  • Declines and Ends (Score:3, Insightful)

    by cephyn ( 461066 ) on Thursday October 14, 2004 @06:54PM (#10530450) Homepage
    Really its a hairsplitting sort of argument. They both agree the meteor killed the dinos. Whether the dinosaurs were in "decline" well -- what's decline mean? One group says the dinos were at the peak of their diversity or whatnot. The other says they were waning. And this is of course based on an incomplete fossil record (both of them).

    And there's declines, and consolidations. There used to be more primate species on earth, now there are fewer -- are they in decline? Tough to say yes, tough to say no. Sure, they're in decline in variation, but not in numbers or population. So I'd like to hear more about what both groups mean by "decline".

    Just my 2c.

  • Sounds Sketchy to Me (Score:5, Informative)

    by CheshireCatCO ( 185193 ) on Thursday October 14, 2004 @07:20PM (#10530642) Homepage
    I should preface this by admitting that I'm not a palentologist or a geologist, but this sounds like a sketchy argument. It is (as the article points out in the middle) difficult to pin down the date of an extinction from the fossil record. Since only a small fraction of the dead organisms are preserved, you will generally see the last fossil of a given species some time before the actuall extinction event, even if the extinction is basically instantaneous. (i.e. -- a steady population to the moment of extinction, then zero population.) We had a colloquium speaker here in my (Astronomy) department a couple of years ago who explained how this works in pretty convincing detail. So you'll always see what looks like a decline in the biodiversity before an extinction event. Exactly how to deconvolve the effects of the spotty fossilization and the actual event itself is a bit tricky. So I approach the claims for the gradual decline with a lot of caution.

    Which isn't to say that it's impossible. But given the trickiness of the data analysis and the odd coincidence of the asteroid impact just then, I'm skeptical.

  • ohhhh come on (Score:3, Interesting)

    by Madcapjack ( 635982 ) on Thursday October 14, 2004 @08:29PM (#10531052)
    Space.com has an article on this, and has an interesting view. The article can be found here. [space.com]

  • Unlike the Dinosaurs, some things never die... (Score:4, Interesting)

    by Anonymous Coward on Thursday October 14, 2004 @08:39PM (#10531129)
    Really, the "slow decline" idea is, by itself, an old and fairly tired argument. There is little dispute that the dinosaurs were in decline in N. America before the K-T boundary, but the fact of decline doesn't imply that the deathblow wasn't strongly related to the Yucatan impact.

    Most people who have studied the Earth's history of mass extinctions have come to understand a few important points. First, it doesn't appear that bolide impacts are the primary cause of many of them. Second, when mass extinctions occur, they appear to have been the result of several factors acting simultaneously to cause a collapse of the food chain.

    At the K-T boundary there were several things going on at once, and they appear to have (together) resulted in the extinction of the dinosaurs:

    First, the dinosaurs were already in decline in N. America, with most dinosaur populations concentrated in N. America and part of Asia. Major disruptions in the breeding cycle of dinosaurs would have been disasterous.

    Second, reconfiguration of the continents was changing the ocean's circulation patterns. This affected climate, ocean temperature, ocean mixing, and most fundamentally ocean productivity.

    Third, the dinosaurs weren't the only creatures that went extinct at the KT boundary, lots of things had been in decline, probably due to ongoing climate change & major volcanism...

    Fourth, major volcanism was occurring during the end-days of the Cretaceous. High rates of seafloor spreading along a couple major ridges probably changed seawater chemistry, and the Deccan Traps were erupting in the vicinity of Asia. If you're not familiar with the Deccan Traps, imagine 200,000 square miles of volcanic rock a few thousand feet thick -- about 12,000 cubic miles of lava (for reference, that's about half a million times more material than Mt. St. Helens erupted in 1980). This would have been a significant stressor affected climate and biosphere; Asian dinosaurs might have been particularly hard hit, but the presence of this large igneous province bws probably not sufficient to collapse the food web and by itself result in the demise of the dinosaurs.

    But fifth, on the other side of the globe from the Deccan Traps, a bolide collided with what would become the Yucatan Peninsula. The sedimentary rocks there contained thick anhydrite deposits (that's calcium sulfate) and thick layers of limestone (calcium carbonate). The blast would have rapidly liberated the sulfate and carbon dioxide from those minerals, then thrown billions of tons of particulate matter in to the stratosphere. The particles thrown up from the impact would have blotted out the sun, while the sulfur rained back as sulfuric acid rain (this isn't good for vegatation or aquatic critters). Darkness would have slowed primary photosynthesis, but even after the skies cleared the climate would have been thrown in to chaos: the CO2 liberated from the blast could have caused severe greenhouse warming in the few thousand years after the impact, wreaking yet more biological havoc. I could keep describing various aspects of the chaos that would follow such an impact, but don't think it's really necessary. The impact may not have, by itself, been enough to kill off the dinosaurs, but it must have severely stressed and already severely stressed ecosystem, and following a multi-faceted attack on the base of the food chain, the top macrofauna would have had a rough go of it.

    Finally, the impact event is very strongly correlated with the extinction of the dinosaurs; there's very little evidence that any dinosaurs in N. America survived the impact -- to my knowledge, no dinosaur fossils have been found stratigraphically above the iridium layer (there are cases where fossils could have weathered out of Cretaceous strata and been redeposited on younger Tertiary strata, but that's not evidence for the dinos having survived the boundary).

    In conclusion, there's no proof that the dinosaurs would have survived had there not been an impact, nor

  • Not convinced. (Score:4, Interesting)

    by jd ( 1658 ) <imipakNO@SPAMyahoo.com> on Thursday October 14, 2004 @09:30PM (#10531569) Homepage Journal
    Part of the problem with the "they were dying anyway" theory is that many relatives survived. This is evidenced by the direct path between dinosaurs and birds, for example. Certain reptiles, such as crocodiles and alligators, also originate from this time period.


    If conditions, even millions of years prior to the extinction, were so hostile to reptilian life that the dinosaurs were dying out, conditions for millions of years after must've been considerably worse. How, then, have so many reptiles from that time period survived?


    Certainly I believe there was a mass extinction, and that it was caused by a sudden event. Sheer dumb luck is all that is required to explain the survival of reptilian life from this time. Luck, though, tends not to hold out over timeframes spanning tens or hundreds of millions of years.

    • The reason reptiles, small dinosaur relatives and small mammals survived such an upheaval where the giants died lies in their energy requirements.

      I've seen a fairly good case made for the dinosaurs being warm-blooded. This means that they required a huge, steady supply of food, which was disrupted by the catastrophe.

      A cold-blooded crocodile gets by on a lot less food, since it doesn't heat itself constantly. It just grows more slowly with less food.

      Now, mice. Take a brontosaur's mass of mice, say 20,000.
      • Minor quibbles:

        Take a brontosaur's mass of mice, say 20,000

        20000 mice per apatosaur??? Must be some HUGE mice. The size of my cat, perhaps. How about 1,000,000 mice, instead? But the basic idea is sound

        Also, for us purists, brontosaur is an invalid designation. Apatosaur is considered correct, since it predates the brontosaur label by some years.

  • When I studied Biology at my first foray to university it was believed by academics at my uni that it is impossible to pin down a single cause for the extinction of dinosaurs. There were many factors that could have contributed. By far my favorite theory for a contributing factor is that the evolution of angiosperms (flowering plants) allowed for the development of defensive poisons for the first time (few if any non-angiospems produce toxins except for fungi which are not plants anyway). Evolving slowly
  • Using the theroy that a meteor struck the Earth with enough force to cause devistation to the environment, bloking out the sunlight. Perhaps this caused the plants to then evolve creating the poisons to increase their chance of survival. This link www.unknowncountry.com/news/?id=3328 suggests that oxygen fell to dangerously low levels wiping out 90% of all existence on the planet. Indeed i am not sure of the estimated date of the meteor impact, but the decline in oxygen was estimated at 175 to 275 million
  • .... Maybe a huge chunk of Strange matter (ie. a strange-nugget) [wired.com] wiped them all out.

    Instead of playing find the big crater, maybe we should be playing find the big tunnel in the Earth...

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