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New Theory Explains Periodic Mass Extinctions

Posted by Zonk on from the we're-not-due-for-a-little-while-yet dept.

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."

17 of 383 comments (clear)

  1. Huh. Better get to work! by SatanicPuppy · · Score: 5, Interesting

    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...

    --
    ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
    1. Re:Huh. Better get to work! by Loke+the+Dog · · Score: 4, Interesting

      Which is kind of cool to think about... Imagine if rats have built a civilization about on par with our current civilization, but they are just a few years from this catastrophic event when they discover this pattern. And they are desperately searching the human ruins in hopes of finding some kind of technology to deal with this. It would make a good movie, I think.

    2. Re:Huh. Better get to work! by Shadow+Wrought · · Score: 3, Interesting

      I think we'll hit the crossroads in the next 500 years. Civilization will either keep advancing, or collapse. In the event of a collapse, it will be interesting to see what our distant proginy do to climb back up the hill. The Eden trilogy by Harry Harrison is interesting along those lines because it posits an advanced dinosaur based civilization based more on biotechnology than mechanical technology.

      --
      If brevity is the soul of wit, then how does one explain Twitter?
    3. Re:Huh. Better get to work! by fyngyrz · · Score: 2, Interesting
      Imagine if rats have built a civilization about on par with our current civilization

      "Writing of the Rat" by James Blish, first published in Galaxy magazine, July 1956. Republished in "A Dusk of Idols" by Severn House, May 1996, 0-7278-4967-0.

      First we arose, then the rats, then us again. Well worth reading even today, as is so for many of his works.

      --
      I've fallen off your lawn, and I can't get up.
  2. Sci-fi got there first by joker784 · · Score: 1, Interesting

    I have just finished reading "Second Genesis" by Donald Moffitt from 1986, that has a very similar explanation for mass extinctions!

  3. Figure 4 in the paper by Pausanias · · Score: 5, Interesting

    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.

  4. Perfectly reasonable hypothesis? by benhocking · · Score: 4, Interesting

    It's a perfectly reasonable hypothesis if one accepts the premise that mass extinctions have an approximately 62 million year period. From Wikipedia, 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.

    --
    Ben Hocking
    Need a professional organizer?
    1. Re:Perfectly reasonable hypothesis? by fimbulvetr · · Score: 2, Interesting

      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 making them more likely to survive.

    2. Re:Perfectly reasonable hypothesis? by ajs · · Score: 2, Interesting

      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 center of the galaxy (regions of the nebula closer to the center move faster, and regions further out, slower). This nebula and the proximity of other stellar systems almost certainly provided some shielding from dangerous intergalactic muons, and the whole nebula would have started with a similar orbital eccentricity as Sol. So, over millions of years, as the nebula was pulled apart by galactic tides, our protection has thinned. The upsetting part (if you get upset about events that could affect us in tens of millions of years) is that it probably has more thinning to go, and our exposure to these extra-galactic particles is probably increasing each cycle.
    3. Re:Perfectly reasonable hypothesis? by Burz · · Score: 2, Interesting

      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 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.

    4. Re:Perfectly reasonable hypothesis? by Tatarize · · Score: 2, Interesting

      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 is no longer uncommon to be uncommon.
  5. -1, Totally Irrelevant by athloi · · Score: 2, Interesting

    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).

    --
    technical writing / development
  6. You joke, but look at table 2 by benhocking · · Score: 2, Interesting

    Almost all of the diversity minima precede the cosmic ray maxima, and all of the declines (from diversity maxima) precede the cosmic ray maxima. I think you're on to something there... ;)

    --
    Ben Hocking
    Need a professional organizer?
  7. Not really by Cairnarvon · · Score: 2, Interesting

    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.

  8. Related to something else by gr8_phk · · Score: 2, Interesting

    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 have the extinctions happen at the time of lowest cosmic ray flux. I guess he got the oscillation part right and the cause of the extinctions wrong. Too bad I can remember where I read that...

  9. Re:Well, that would explain by benerivo · · Score: 2, Interesting

    Yeh i'd agree with Bombula. Henrik Svensmark is the guy who is at the forefront of cosmic ray effects on our climate - but the whole theory gets flamed by the mainstream greenhouse gas theory as it threatens it's 100% claim on the explanation of climate change. The correlation between cosmic rays and past climate is almost perfect (see fig. 5)... http://www.sciencebits.com/ice-ages

  10. Re:Why not? by smellsofbikes · · Score: 4, Interesting

    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 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.)

    --
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