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Space Science

New Theory Explains Periodic Mass Extinctions 383

i_like_spam writes "The theory that the dinosaurs were wiped out by an asteroid impact, the K-T extinction, is well known and supported by fossil and geological evidence. Asteroid impact theory does not apply to the other fluctuations in biodiversity, however, which follow an approximate 62 million-year cycle. As reported in Science, a new theory seems to explain periodic mass extinctions. The new theory found that oscillations in the Sun relative to the plane of the Milky Way correlate with changes in biodiversity on Earth. The researchers suggest that an increase in the exposure of Earth to extragalactic cosmic rays causes mass extinctions. The original paper describing the findings is available online."
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New Theory Explains Periodic Mass Extinctions

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  • by SatanicPuppy ( 611928 ) * <Satanicpuppy@g[ ]l.com ['mai' in gap]> on Thursday August 02, 2007 @04:14PM (#20092077) Journal
    Only 7 million years from now, for all you long range planners. Better stock up on beans, bottled water and relocate your house 1 kilometer underground.

    It's a perfectly reasonable hypothesis, though it'll be a while before we can test it. It's always a little weird though, to think of extra-solar events as relevant on a "local" scale. I mean, in the same way that Earth is endangered by rogue meteorites and asteroids, the whole solar system is vulnerable to a rogue star or brown dwarf. Anyone ever read Jack McDevitt? He's obsessed with that sort of disaster (pun intended).

    Hard to get your mind around it...The odds are so long...

    • So we have 7 million years to figure out space flight and/or a way to record the sum of our knowledge for future intelligences.

      We're hosed.

    • What honestly scares me more is something going supernova within a hundred light years of us. That would pretty much destroy all life (or at least all complex, multicellular life).
      • Odds are (Score:2, Informative)

        by Gr8Apes ( 679165 )
        I believe it was 28-30 million light years, and then its axis for gamma rays would have to be pointing directly at where the earth would cross the relatively brief beam. IOW, you're more likely to get directly hit by a killer asteroid.
    • It's a perfectly reasonable hypothesis if one accepts the premise that mass extinctions have an approximately 62 million year period. From Wikipedia [wikipedia.org], the last 6 extinction events happened 65 million years ago, 200 million years ago, 251 million years ago, 360 million years ago, 444 million years ago, and 488 million years ago. The time between extinctions being 135 million years, 51 million years, 109 million years, 84 million years, and 44 million years. I'm having a hard time wrapping even an approximate 62 million year period into those.
      • by gEvil (beta) ( 945888 ) on Thursday August 02, 2007 @04:58PM (#20092849)
        Sounds like someone needs to edit Wikipedia to make this hypothesis fit a little better...
      • not only that but mass extinctions happened a lot earlier than that and with a far less predictable pattern. which leaves us to wonder why this cycle is this recent? why isn't there a cycle like this stretching back over a billion years? presumably the nature of the sun's orbit around the galaxy we should see this happen a lot longer than half a billion years and with many extinctions not following the pattern, the explanation seems a bit weak.
        • Re: (Score:3, Interesting)

          by ajs ( 35943 )

          not only that but mass extinctions happened a lot earlier than that and with a far less predictable pattern. which leaves us to wonder why this cycle is this recent? why isn't there a cycle like this stretching back over a billion years?

          I haven't read the original paper, and the article is thin on details, so I'm not sure exactly how many events they considered... HOWEVER, I do not think you're correct about the conditions being static across spans of billions of years.

          Our sun (Sol) is a member of a cluster of stars that were birthed by a nebula of gas and dust around the same time. That cluster (like all stellar nurseries within a galactic disk) tended to break apart as time went on, due to the difference in orbital speeds around the cen

          • by Xtravar ( 725372 )

            Our sun (Sol) is a member of a cluster of stars that were birthed by a nebula of gas and dust around the same time. That cluster (like all stellar nurseries within a galactic disk) tended to break apart as time went on, due to the difference in orbital speeds around the center of the galaxy.

            My god, this reads like some twisted fairy tale or the Bible.

            You see, Sol was different from all the other stars in his nursery. He was more advanced than his nebulous peers, and thus started orbiting sooner than all the others. One day, he came upon a rabbit in his journeys and he said, "Oh wise rabbit, why am I all alone in the galaxy?" The rabbit replied, "I will tell you, but only if you can provide me a carrot for I have been traveling very long and am very hungry." And Sol gave the rabbit a carro

        • Re: (Score:3, Informative)

          not only that but mass extinctions happened a lot earlier than that and with a far less predictable pattern. which leaves us to wonder why this cycle is this recent? why isn't there a cycle like this stretching back over a billion years?

          As far as the fossil record is concerned, the only things that existed beyond 550 million years ago are basically algae, bacteria, simple worms, etc. It wasn't until after that time that biodiversity really took off. It's entirely possible that this pattern goes back thro
      • Re: (Score:3, Interesting)

        by fimbulvetr ( 598306 )
        It looks like it just got sensationalized from "Varied levels of cosmic radiation" to "Mass extinctions". What the paper does a better job describing is how such cycles would account for increased diversity in lifeforms. Consider, for instance, the cambrian explosion. Based on what we know about evolution, such an explosion is unprecedented and highly unlikely, despite the evidence. Perhaps increased Cosmic Rays caused a massive amount of mutations that forever changed the genetic data of organisms by makin
      • by ajs ( 35943 ) <ajs.ajs@com> on Thursday August 02, 2007 @05:13PM (#20093049) Homepage Journal

        It's a perfectly reasonable hypothesis if one accepts the premise that mass extinctions have an approximately 62 million year period. From Wikipedia [wikipedia.org], the last 6 extinction events happened 65 million years ago, 200 million years ago, 251 million years ago, 360 million years ago, 444 million years ago, and 488 million years ago.
        You're looking at the largest of the extinction events. This theory is attempting to explain a particular set of events which result in only an approx. 10% drop in biodiversity, and which are about 60ish million years apart.

        The KT event, for example, had a much larger impact on biodiversity but happened off-cycle, and is pretty clearly the result of a specific meteor strike that we already know about.

        Other events may have been volcanic or meteoric or the result of something we didn't know about.

        All extinction events being triggered by only one type of external condition was never very likely.
      • Re: (Score:3, Interesting)

        by Burz ( 138833 )
        As ajs pointed out, the hypothesis is concerned with much smaller extinction events than the large ones you listed.

        However there is at least one supportable theory [sciam.com] for several of the larger ones: Death by hydrogen sulfide eruptions. Briefly, global warming leads to ocean anoxia and the spread H2S-spewing bacteria; death of aerobic ocean life accelerates the bacteria growth in a positive feedback until H2S concentrations also begin to spew from the oceans and kill life on land.
      • Re: (Score:3, Interesting)

        by Tatarize ( 682683 )
        And why exactly do we have this very exactly dated impact in the Yucatan with little bits of it everywhere on Earth, tracing back to the right time period? What are we suppose to do with this massive amount of evidence right at the K-T switch if we are to suppose that it was just solar winds wiping out most life?

        It seems like a lot of evidence to have for something with nothing to do with it.
    • It's a perfectly reasonable hypothesis, though it'll be a while before we can test it.
      Why couldn't we send a probe up (or down) relative to our solar system's plane? Measure the change in radiation readings as it goes and see just how much the Sun interferes with this radiation.
      • Re: (Score:3, Informative)

        by Gospodin ( 547743 )

        Because what matters is the galactic plane, not the solar ecliptic. It's going to take a while (read: about as long as it'll take the Solar System) for the probe to get a decent reading.

      • Some of our oldest [wikipedia.org] probes [wikipedia.org] are just now leaving the heliopause [wikipedia.org] (which tends to move around a bit), and they were launched 30 or more years ago. Also, I think it might be harder to use a multiple-planet gravity assist to help with speed, although I could be wrong about that.
      • The Voyager probes that were launched in the 70's are barely making it to the edge of the solar system.. These would have to go much, much further.
      • The scale is simply too big to allow meaningful data return in less than many millennia. The hypothesis is talking about exposure to the galactic bow shock wave created as the galaxy moves through the intergalactic medium. The probe would need to move significantly "up" relative to the galactic equator to measure the difference in radiation.
    • by Anonymous Coward on Thursday August 02, 2007 @04:36PM (#20092507)
      Dude... A house 1 kilometer underground, and you want to stock up BEANS??
    • by ajs ( 35943 )

      Only 7 million years from now, for all you long range planners. [...] It's a perfectly reasonable hypothesis, though it'll be a while before we can test it.

      I don't think it'll be as long as you think. Within 100 years we will probably have the ability to send very small probes out of our solar system at speeds which measure substantial fractions of the speed of light. At that point, we can start sending out probes to analyze the galactic "weather" of regions that the Earth will occupy further down the line. It's still a slow process (requiring decades to centuries for results), but it's probably not as lengthy a process as you're thinking it is.

  • lead based sun block?
  • It burns... (Score:5, Funny)

    by unchiujar ( 1030510 ) on Thursday August 02, 2007 @04:16PM (#20092117)
    Will my tinfoil hat protect me ?
  • Well, that would explain the world-wide black stratum in the planet's rocks that make the K-T event so readily identifiable.

    Or not. Does this theory merely half-explain what we already know or does it make other stuff that we couldn't explain come out right, too? Sounds like the former...
    • Here's an idea: why not RTFA? It's not long.
    • by eln ( 21727 ) * on Thursday August 02, 2007 @04:22PM (#20092223)
      The article suggests that this does not explain the K-T event, which is already adequately explained by the asteroid impact theory. This theory explains the cyclical decreases in biodiversity that seem to happen about once every 62 million years. The K-T event is not part of this cyclical pattern.
    • Heh. If we caught enough radiation to turn the surface of the earth black every 62 million years, we wouldn't be here talking about it now. Anyway, the K-T boundary doesn't intersect with this, it's off by about 10 million years.

      This would be a period of significant problems, affecting pretty much all living things, but clearly it's not the end of the world, just a period of environmental hard times.
    • Why would it wipe out only 10% of the SPECIES?

      How/Why did the other 90% survive?

      Muons can punch through rock. They'd be hitting every living thing on Earth. Yet 90% of the species seem to survive. While 10% die off.
      • Why not? (Score:5, Insightful)

        by SatanicPuppy ( 611928 ) * <Satanicpuppy@g[ ]l.com ['mai' in gap]> on Thursday August 02, 2007 @04:43PM (#20092595) Journal
        Radiation doesn't kill things off that well. Look at Chernobyl or the Savannah river plant...Both shut down, both radioactive, both experiencing a resurgence of pretty healthy wildlife across the board.

        Lot of the things we assumed about radiation back in the day (e.g. mutants and Godzilla) have turned out to not really happen so much. DNA isn't as fragile as we assumed, and while the extra rads may kill you quicker (only live to 60 instead of 80), it's not quick enough to keep you from reproducing.

        We're not talking some kind of galactic nuke here...It's just a significant upswing in radiation. Hell, the fact that we've had these historically is maybe why the ecosystem tolerates increases in radiation so well.
        • Radiation doesn't kill things off that well. Look at Chernobyl or the Savannah river plant...Both shut down, both radioactive, both experiencing a resurgence of pretty healthy wildlife across the board.

          Take UV light. A veyr small dose causes phenotypic adaptiation to it. A little bit more cause tumors/DNA damage. A lot more causes cellular sterilization. It's all about dosage.
          • Take UV light. A veyr small dose causes phenotypic adaptiation to it. A little bit more cause tumors/DNA damage. A lot more causes cellular sterilization. It's all about dosage.

            Now, subject 100,000 species to a high dosage, over generations.

            Would you expect to see no problems for 90% of the species? While 10% die off?

            I wouldn't. Enough radiation to kill an entire SPECIES would, logically, have an effect on other species that share the same ecosystem.

            But we don't see that in the fossil record.

        • Radiation doesn't kill things off that well.

          That's the problem. This theory says that the radiation killed off 10% of the species on Earth.

          That IS killing things off pretty well. That's "decimating" the number of species on Earth.

          And we're not talking about a specific threat to specific ecosystems. The oceans didn't evaporate nor did they freeze. The radiation covered the Earth and only killed off 10% of the species. Multiple times.

          That does not make sense. Either a LOT more die or it only takes out the wea

          • perhaps those 10% didn't have good DNA repair mechanisms as a species and it's only 10% because the species who evolve without it get smacked every 62 mil or so.
        • Re:Why not? (Score:5, Interesting)

          by smellsofbikes ( 890263 ) on Thursday August 02, 2007 @06:42PM (#20094395) Journal
          I have some friends with PhD's in nuclear science who claim that radiation is beneficial. They go further: life started when there was a lot more radiation, so most of our genetic machinery is designed to work with far higher radiation than what we're seeing, which is to say we can stand a lot more radiation with little harm. They go further and claim that because there's less radiation now, we have more problems -- higher background radiation might act to suppress immune system malfunctions (sitting in radioactive hot springs does seem to reduce the symptoms of arthritis.) Life survival vs. number of cells should be inversely proportional as radiation level rises: if a bacterium has its DNA badly injured by a radiative event, it's less likely to survive than an animal with a million cells. (I've read in other places that every strand of DNA in every cell experiences tens of damage events requiring repair every day.) My friends the PhD's go so far as to claim that the reason that the seven counties in the US with the longest average lifespan are all on the Continental Divide in Colorado [plosjournals.org] where the radiation levels are highest because of the elevation.
          (Sorry I can't find a better link for the Eight Americas dataset: you have to download an Excel spreadsheet to get the raw data.)
          • Re: (Score:3, Insightful)

            life started when there was a lot more radiation,

            Life also started in water, that shields out the most harmful radiations. Life on land has to wait until the ozone layer was strong enough.

            if a bacterium has its DNA badly injured by a radiative event, it's less likely to survive than an animal with a million cells.

            The single bacterium is less likely to survive. The population of billions of bacteria isn't. Also bacteria are independent (to a point): they don't need to be nice to each other to survive, at le
    • Don't know if anyone has thought of this... What if there are large meteors or planetoids orbiting some body or the galactic core and every so often we pass into the vacinity? Or, the meteors come from our own solar system but are disturbed by some juxtaposition of gravitic fields causing disruption in the orbits of said meteors.

      Just a thought.
    • by Bombula ( 670389 )
      This recent article [discovermagazine.com] talks about research that suggests cosmic rays significantly affect cloud cover, and thereby have a direct impact on global temperatures. It's fascinating stuff, and while it doesn't nullify anthropogenic climate change, it definitely makes the picture more complicated and more interesting. The interesting stuff starts on page 2 of the article. From the article:

      "The basic idea is that solar activity can turn the cloudiness up and down, which has an effect on the warming or cooling o

      • by inviolet ( 797804 ) <[slashdot] [at] [ideasmatter.org]> on Thursday August 02, 2007 @05:51PM (#20093669) Journal

        Fewer cosmic rays mean fewer clouds will be formed, and so there will be a warmer Earth. If the sun and the solar wind are not so active, then more cosmic rays can come in. That means more clouds [reflecting away more sunlight] and a cooler Earth.

        That's odd. The post-9/11 research into the effects of jet contrails [sciencedaily.com] suggested that they have two faint effects: mild warming and mild day/night temperature moderation. But the above quote seems to contradict that.

        I am now even more suspicious of the conclusions of the contrail research, coming (as it did) in the middle of the global warming craze. Right now you can't even publish the simple observation that plants will grow usefully faster on a warmer Earth; no, you have to spin it as "OMG poison ivy will get worse!" [google.com].

        I'm ready to go nuclear/solar/wind, and drive an electric car, because I've always hated the power that petronomics gives to the backwards nations... but come on guys, can we at least give both sides a fair hearing?

    • by Divebus ( 860563 )
      What if that black stratum is the radioactive remains of everything organic that died all at once?
  • Greg Egan did a book on this very topic, except it was a dual neutron star that collided with each other.

    Egan, near the end of the book, explained that energy was being transfered into extra-dimensional energy, and not sealing behind an event horizon as it normally should.

    In the book, the binary was a hundred light-years away. It caused mass extinction of the flesher human race, however the digitized humans were safe.

    The book was called Diaspora.
  • Err.. (Score:4, Insightful)

    by HitekHobo ( 1132869 ) on Thursday August 02, 2007 @04:19PM (#20092179) Homepage
    How about 'new hypothesis may explain...'
  • by 140Mandak262Jamuna ( 970587 ) on Thursday August 02, 2007 @04:20PM (#20092187) Journal
    What? Sun? Galactic Plane? Intergalactic Rays? You guys are watching way too many reruns of Star Trek.

    Everyone knows the extinctions were perfectly explained using the Theory of Intelligent Smiting.

    • by Himring ( 646324 ) on Thursday August 02, 2007 @04:37PM (#20092521) Homepage Journal
      lol! I love making fun of god. It's ok too, cuz god's gotta sense of hu

      [NO CARRIER]

    • by Dunbal ( 464142 )
      Everyone knows the extinctions were perfectly explained using the Theory of Intelligent Smiting.

      It's not a theory. If you turn your bible to Hebrews 13:1:
      "Let brotherly love continue. Do not neglect to show hospitality to strangers, for thereby some have entertained angels unawares."

      by this we can interpret that at some point creatures on the earth neglected "hospitality", which can be taken to mean they were far to aggressive. By doing so, they have "entertained
    • That is the best name for the Noah story yet.
  • by Pausanias ( 681077 ) <pausaniasx@gm[ ].com ['ail' in gap]> on Thursday August 02, 2007 @04:20PM (#20092193)
    Check out Figure 4 at the end of the linked paper. It shows that the periods of highest diversity coincide with the periods where the cosmic ray flux is lowest. Really amazing correlation if you ask me.
    • I recall reading one guys work on galactic dynamics where he suggested that our solar system "orbits" or oscillates (planar) through one of the arms (dense areas - we're not a pinwheel) of the galaxy. He suggested that as we pass through the middle, we're more likely to be hit by other objects. This was his explanation for the extinctions. Now we see that someone has concluded such an oscillation is really happening, however they suggest the a different phase relationship. The guy I was talking about would
  • by clusterlizard ( 1136803 ) on Thursday August 02, 2007 @04:23PM (#20092267) Homepage
    It's not even a new slashdot article [slashdot.org].
  • Or Maybe... (Score:5, Insightful)

    by MxTxL ( 307166 ) on Thursday August 02, 2007 @04:26PM (#20092319)
    The researchers suggest that an increase in the exposure of Earth to extragalactic cosmic rays causes mass extinctions.

    Or maybe, the increased radiation merely causes some periods of increased mutations... extinctions follow as species are outcompeted for resources.
  • But NOVA Science Now told me it was global warming :(
  • by ggvaidya ( 747058 ) on Thursday August 02, 2007 @04:26PM (#20092327) Homepage Journal

    ... extragalactic cosmic rays causes mass extinctions ...

    Can we please oh please oh please call them death rays?
  • by athloi ( 1075845 ) on Thursday August 02, 2007 @04:34PM (#20092459) Homepage Journal
    Humanity's chances of avoiding self-destruction or regression to a simian mean within the next 7 million years approximate zero, or worse (Cantor sets).
    • by wurp ( 51446 )
      I hardly agree with your assertion, but moreover...
      what the hell do Cantor sets (lines with a fraction recursively removed from each segment) have to do with it?
  • Maybe there's an impact every 62 million years after all. I hereby posit that Earth is one of spheres in a giant Newton's Cradle [wikipedia.org]
  • Well... (Score:5, Funny)

    by Chouonsoku ( 1009817 ) on Thursday August 02, 2007 @04:36PM (#20092491) Homepage
    I for one welcome our new cosmic ray-based overlords! (I just felt like I hadn't seen that lately. :'( Mod me as you wish. But, be gentle.)
  • ..it is just that whenever I hear about a spectacular new hypothesis about anything that relates to: evolution, climate, weather, nuclear power, solar power, cellphone's or HIV, I almost immediately start grinding my teeth because I just know it will be jumped upon by some media outlet and spun into political propaganda. With this particular one I'm expecting at the very least a few GW sceptics and ID promoters, but with some (bad)luck maybe we can get some references to free energy devices as well... Heck
  • Not really (Score:2, Interesting)

    by Cairnarvon ( 901868 )
    The extinction events are too abrupt to be explained this way, and the "approximate 62 million-year cycle" only looks like a cycle if you squint really hard.
  • Although radiation sources in other galaxies are locally very powerful, I believe that these sources are too far away to have such a drastic effect on earth life. The closest galaxy is 2.3 million light years away. You do the math.
  • ...but what about all of the physical evidence that suggests a massive asteroid impact that sent a fireball around the world killing off vitually all large land-dwelling reptiles?

    I'm sure increased cosmic ray exposure would increase genetic mutation and increase biodiversity though. :)

  • The K-T boundary is not the only one with some pretty good geological/impact evidence to go along with it.

    I recall reading about two separate other ones, T-P in particular comes to mind. Some just need the "gun" (a crater or volcano).

    So, you sort of not only need to come up with a new theory, but come up with a new theory that better fits the time lines and the details of what we think happened better than the existing one. For T-P, there are volcanic deposits that could have been involved around that tim
  • Nova Science Now [pbs.org] was looking at the Permian extinction 250 million years ago. The quick summary:

    So it starts with volcanoes spewing carbon dioxide; next step: global warming. The oceans heat up and lose their oxygen, nasty bacteria take over, burping out lots of poisonous gas. End result? Mass extinction.

    I think what we can learn from any theory is that our time on this planet isn't guaranteed forever. There's a reason people want to look at colonizing other planets and moons.

  • I have long thought that asteroid impact was responsible for the K-T Extinction Event [wikipedia.org], but as to other extinctions, I still don't really see them as cyclic with any real constant period. Add to that the fact that the largest such event ever, the Permian-Triassic Extinction Event [wikipedia.org] appears to have been caused by massive volcanic activity in the Siberian Traps of Asia (itself caused by mantle plumes). What you are left with is an assortment of lesser events which, as measured by the marine biodiversity historic
  • by Michael Woodhams ( 112247 ) on Thursday August 02, 2007 @05:07PM (#20092971) Journal
    OK, I've only read the summary (I have a lecture to give half an hour from now to prepare for) but I can see some objections:

    * My boss (David Penny, Massey University) argues that the mammals and birds were already outcompeting the dinosaurs at the end of the cretaceous, so the asteroid was at best a coup-de-grace for them.
    * The "periodic extinctions" idea has been around for decades, including the possible link to oscillations through the galactic plane.
    * Mass extinctions are sudden. The increase in extragalactic cosmic rays exposure would be slow, over millions of years.
    * The extragalactic cosmic ray exposure changes should be highly regular. The extinctions are irregular.
  • by markk ( 35828 ) on Thursday August 02, 2007 @05:28PM (#20093313)
    The title of the summary is totally wrong. This has nothing to do with mass extinctions. Its looking at fossil Species and Family counts vs time correlated with Solar motion. The 62 MY cycle barely touches the Mass extinction events.
    Better summary title - "Life's Diversity changes with Solar Galactic Orbit". Or something like that.
  • Eulogies (Score:3, Funny)

    by StikyPad ( 445176 ) on Thursday August 02, 2007 @07:00PM (#20094613) Homepage
    I, for one, would like to commemorate a few periodic mass extinctions:

    Dear AU, what has become of you? You may not be extinct, but I can never find you.
    Humble Promethium. Your existence was "predicted" long after your demise.
    Oh 271 Seaborgium, how did you decay? Let me count the ways. Alpha decay. Spontaneous fission.
    272 Roentgenium, we hardly knew you. Half extinct at the tender age of 1.5ms. You're the one we'll truly miss.
  • by syousef ( 465911 ) on Thursday August 02, 2007 @08:35PM (#20095523) Journal
    I'm sure I've seen this before, possibly found out about it on /.

    Here's an article from March 2005
    http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/ 03/10/MNGFIBN6PO1.DTL [sfgate.com]

    It's only one of many theories. The wikipedia page that points to the article above discusses them all
    http://en.wikipedia.org/wiki/Mass_extinction [wikipedia.org]

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