New Theory Explains Periodic Mass Extinctions

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."

Comments

Huh. Better get to work!

[SatanicPuppy]

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...

Re:Huh. Better get to work!

[Loke the Dog]

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.

Figure 4 in the paper

[Pausanias]

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.

Perfectly reasonable hypothesis?

[benhocking]

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.

Re:Why not?

[smellsofbikes]

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.)