New Theory Links Biodiversity to the Stars

eldavojohn writes "Space.com's Mystery Monday has an article proposing a hypothesis that our solar system's undulations directly affects biodiversity on earth through cosmic-ray exposure. There's data that, through the fossil record, shows us earth's biodiversity peaking again and again until a great cataclysmic period where it is greatly reduced. The theory essentially suggests that this 62 million year cycle can be attributed to how our solar system moves within the milky way galaxy which turns out to be a 64 million year cycle. It's a plausible explanation though very tough to prove, hopefully we don't have to wait around 64 million years to draw a conclusion on this hypothesis."

Comments

So when is this doomsday supposed to be?

[Romancer]

How far into the cycle are we now?

Interesting and plausible theory, but not so new..

[leather_helmet]

A quick search will bring up a lot of similar ideas regarding the 'orbital rhythm' of the solar system and how it affects things like oceanic levels, radiation levels, which in turn, obviously, has an impact on biodiversity

This general idea has been around for a very long time, I've come across it several times in various magazines like Scientific American, etc.

In Other News....

[bossesjoe]

Astrologists are freaking out across the world at the first sign of honest scientific news that shows a link between stars and life on earth, telling everyone that they knew all along the stars are what makes everything the way it is.

Re:542 Million year chart

[Tofystedeth]

I know I could look this up and possibly prevent myself from looking like an idiot, but I feel lazy so I'm just going to work on my own fuzzy recollections. I believe that was a Heinlein (or otherwise famous slightly olderschool sci-fi author) short story about the guy who studied trends and found that all of the cyclic trends were converging at one point and predicted the end of the world by a year or two?

Nemesis

[jafuser]

One interesting hypothesis is is that a red or brown dwarf in a highly elliptical orbit with our sun periodically (every ~26M years) passes through the Oort Cloud and pulls comets into the inner solar system, causing a wave of extinctions.

BTW, one of the physcists researching this idea, Richard A. Muller teaches a great physics course, titled "Physics for Future Presidents" which is available online for free on google video.

You laugh now

[hellfire]

This is not meant to be a funny post.

Here's an article on extinctions in Wikipedia.

Here's a snipet from that article about mass extinctions:

There have been at least five mass extinctions in the history of life, and four in the last 3.5 billion years in which many species have disappeared in a relatively short period of geological time. The most recent of these, the K-T extinction 65 million years ago at the end of the Cretaceous period, is best known for having wiped out the non-avian dinosaurs, among many other species.

In other words, don't laugh about the 62-64 million year cycle. We are due for a mass extinction, according to the fossil record. Maybe this phenomenon has something to do with it. Note that when biodiversity goes down in a species, that's not good, biologically speaking. Less diversity means less chance of a species being able to survive a catastrophic event.

Take it for what you want, but all those people laughing about having to wait 64 million years, my point is, I don't necessarily think you have to wait all that long.

Re:You laugh now

[Coco Lopez]

You're mixing together two biological concepts that may lead to confusion and panic in people reading your post; those being the interspecies diversity which is the diversity of species within an ecosystem, and intraspecies diversity which is genetic diversity within individuals of the same species.

The benefits of varying levels of interspecies diversity for ecosystems is a complicated issue, and I think if you go to the literature you'll find papers that show a correlation between decreasing interspecies diversity and increased primary productivity, which is one measure of ecosystem 'fitness'; and you might find the opposite as well. It's complicated, and it's ecology, so it's not quite science anyway.

In the case of a random global catastrophe such as an asteroid impact, some species are going to live and some species are going to die. If humans were to nominate ourselves as Earth shepherds and try to keep some arbitrary level of interspecies diversity on Earth, we probably would fail miserably. However, the good news is that mammals have survived asteroid impacts in the past, and humans have proven ourselves particularly adaptable; so, perhaps we'd stand a better chance of making it through.

Now, when you talk about diversity as a determinant of whether a species can survive a catastrophic event, you must be talking about intraspecies diversity. The rate of accumulation of intraspecies diversity should be correlated with the mutation rate, which is relatively constant over generations within a species. The mutation rate is where the cosmic rays come in, but variations in solar radiation, radiation from the earth itself, diet, environment and genetic factors will all play a role.

Examples of where intraspecies diversity has saved humans in the past are in malaria-affected populations in Africa with individuals having sickle-cell haemoglobin, and in some European populations (and I believe a small group of people somewhere in Asia) who needed to survive off of milk products having lactase being expressed in adults. These are just some well known clear examples.

If the point of the parent was that we should be scared about our own asses becoming extinct, I don't think we need to worry too much. One thing that guarantees intraspecies diversity is having a large sexually reproducing population spread over diverse geographical regions. But, if you want to be proactive about it, spend more time with your gonads exposed to the sun --- better yet, put your gonads in an X-ray machine.

Re:You laugh now

[vertigoCiel]

I'm a lot more worried about the Yellowstone Supervolcanoe going than the stars. The thing blows, on average, every 600,000 years. Want to know the last time it erupted? 640,000 years ago. When it goes, it'll take most of Northern America with it.

Take that, astronomical mutation-mongers!

Why this is not so: evolving DNA repair

[G4from128k]

I really doubt this hypothesis because it assumes that organisms are helpless in the face of change levels of cosmic radiation. The reality is that DNA repair mechanisms are subject to evolution (and can evolve relatively quickly in lab experiments). If background radiation rose, organisms would simply evolve more robust DNA repair mechanisms. If cosmic radiation dropped off, then organisms would simply evolve less robust DNA repair mechanisms.

Totally Implausible

[Anonymous Coward]

The 64 million year cycle they are invoking is an up and down cycle through the galactic plane. This means the danger zone must be associated with a certain Galactic height
(distance above the mid-plane of the Galactic disk). But:
1) the bio-diversity cycle would not be a fixed 64 billion year cycle, unless the danger zone was at the sun's peak Galactic height. Otherwise, the
sun would pass through the danger zone at uneven (though still periodic) time intervals.
2) the height of the danger zone would have to be at a roughly uniform Galactic height throughout the disk, otherwise the sun would aperiodically emerge into the danger zone.
3) the danger zone would have to exist on one side of the galaxy, but not the other.

Seems unlikely to me.

Out of Phase?

[SoVeryTired]

I would really like to see a larger chart than the one they give. Cycles which are 64 and 62 years long respectively will begin to shift out of phase with each other eventually, and after (I think) 32 cycles they will be 180 degrees out of phase. If the biodiversity cycles still are still the same when the two are out of phase, it would discredit the theory. Of course, this means you have to go back almost two billion years, when the only life was a kind of blue-green sludge (at best).

55 million years? Possible additional evidence

[iamlucky13]

It's hard to read off the chart, and I didn't see mention in the article, but this submission immediately brought a few things to mind:

About 55 million years ago the earth apparently underwent a significant warming event called the Paleocene-Eocene Thermal Maximum that resulted in the extinction of 30-40% of deep sea life, and may have been equally instrumental in the emergence of mammals as the asteroid 10 million years before that killed off the dinosaurs.

The trigger is unknown, but it is believed that warming oceans due to a natural cycle caused the sublimation of large quantities of methanes from clathrate deposits on the sea-floor. Methane, of course, is a potent greenhouse gas. The result was average ocean surface temperatures as much as 10 deg C warmer than before. The cause of the natural cycle is unknown. However, I just did some digging around, and it appears the major long term thermal cycles (based mostly on O-18/O-16 ratios in sediments, is my understanding) run 140 million years on average, but higher frequency signals definitely exist.

Now, there has been some recent research finding that cosmic ray activity may be an influencing factor on global warming (Note: No need to revive the global warming debate...I'm just sharing my thoughts, and am not claiming anything). Basically cosmic rays appear to affect the formation of clouds in the upper atmosphere, which in turn effects solar insolation.

It would be very interesting if this 62 million year cycle happened to coincide with the PETM extinction 55 million years ago. My thought being perhaps a cosmic ray cycle caused a typical warming cycle that happened to induce the "big burp" of methane-clathrates, which significantly magnified the warming effect.

Actually, with some further poking around, I see this basic theory has been proposed for explaining the 140 MY cycle, minus the methane-clathrate bonus.