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It's the end of the world as we know it
May 7, 2012 6:39 PM   Subscribe

I'm trying to think of realistic extinction-event scenarios that don't involve nuclear bombs or things crashing down from outer space, but would doom humanity in about the same time frame (wiped out within a generation, or even quicker.)

When I say "realistic" I mean more "doomed by widespread wheat blight" or "bio-engineered plague" and less "aliens attack" or "robot overlords."

While I'm interested in things that would push humanity into extinction within a generation, I'm also interested in more dramatic events, ecological disasters, etc that could quickly snowball into bringing about the end of the human race within days, weeks, or months.

I've googled this a fair amount so I'm already familiar with the obvious ones (magnetic pole shift, gamma radiation, stray comets, global warming, etc) but I'm looking for the potentialities that we don't often think about. Science-based if possible, please.

posted by egeanin to Science & Nature (37 answers total) 38 users marked this as a favorite
You didn't mention grey goo? Really, anything on the nano-level has this potential; once the ability to design nanites at home is around, it's almost an eventuality that someone will build something horrifying
posted by MangyCarface at 6:47 PM on May 7, 2012

If bio-engineered plague fits your definition, maybe grey goo does?

Within one generation, I guess you only need something that would cause sterility instead of necessarily killing people.
posted by XMLicious at 6:49 PM on May 7, 2012

Geologically, the main ones we learned about this past semester were Super-volcano explosions and Basalt lava floods. Flood basalts in particular are strongly theorized to be a cause of past mass extinctions, mainly because of the large amounts of poisonous gasses emitted into the atmosphere.

Also Ice Ages, while probably not likely to cause the extinction of humans, have been linked to the fall of civilizations somewhere in the 1200-1400 A.D. area.
posted by DoubleLune at 6:49 PM on May 7, 2012 [2 favorites]

In additional the obvious mayhem from the event itself, an asteroid impact or supervolcano eruption could put enough dust into the air to trigger cooling of the earth through reflection of sunlight off said dust, as well as decimate crop production through lack of sunlight and basically make air much less breathable, all of which would have obvious and quickly-noticed effects on humans.

Natural epidemics seem less likely to happen on a global scale (though a man-made epidemic could happen with the right set of flight plans). It could be possible for something bacterial to overrun the population, but unless all our antibiotics fail, we still have a fighting chance to control it. We're overdue for another bout of global influenza, but it would be easier to contain and provide treatment for this time around.
posted by Blazecock Pileon at 6:49 PM on May 7, 2012

David Brin's Earth had scientists creating an artificial microscopic black hole to use for energy production or something and accidentally dropping it.
posted by XMLicious at 6:59 PM on May 7, 2012

Prion diseases are a big wild unknown. They're not a bacteria, not a virus, not even a protein. They're a folded shape of protein, little more than a bit of arcane geometry that can self replicate on unsuspecting proteins. If you understand that and that the only way to destroy a shape is to truly obliterate it, you see how these could be apocalyptic.

That said, they aren't. But the sci-fi leap to unstoppable plague is a tiny one.
posted by chairface at 7:02 PM on May 7, 2012

My money's on a volcano.

But remember, humanity isn't quite as resilient as roaches, but it's awfully close. We only need a single concentrated population in the hundreds or low thousands to rebuild (over a very, very long time, obviously.) The kinds of things that will wipe us out, completely, will need to take out the planet, before we've moved out of the solar system (and preferably before we have any offplanet colonies.)

Anyway, so for true extinction, I expect a direct comet impact, or supernova. Break the Earth apart to ensure catastrophic elimination of the species.
posted by SMPA at 7:02 PM on May 7, 2012 [1 favorite]

Oh, lets see....

1) Gamma Ray Burst within, oh, 1000 LY or so.

Meet WR 104. If the rotational axis is closer to dead on that we currently think, when it goes supernova -- and it will -- there's going to be an *enormous* amount of high energy gammas rays coming at the Earth, and when they hit, well, we die 8000 years later.

If it is aimed at earth, and it went bang 7999 years ago, we wouldn't known it yet. When we find out, well, we die.

2) A 1 solar mass black hole cuts through the solar system. If we're "lucky", it'll run right into the earth and just rip us to bit via tidal interaction. There would be a fun moment where the black hole will be exerting a 1G pull on you, and the planet will be exerting a 1G pull on you, and if they're in opposite directions, hey, everything is *floaty*!.

If we're unlucky, we don't get hit, but we have to deal with the inevitable orbit alteration, which means we either burn to death, we freeze to death, or we alternate between the two.

3) When it doubt, hit it with a *big* rock. It worked for the dinosaurs, after all.
posted by eriko at 7:04 PM on May 7, 2012 [16 favorites]

The extinction of bees. No crop pollination means no food, for us and for the animals we eat. Although I bet Monsanto is developing a bioengineered workaround.
posted by MexicanYenta at 7:15 PM on May 7, 2012 [2 favorites]

Similar to the grey goo scenario, a technological singularity could theoretically annihilate us. Or transmogrify us, and every other atom of the Earth, into an undifferentiated, intelligent gas cloud.
posted by Kandarp Von Bontee at 7:17 PM on May 7, 2012

Super-volcano. They are known from geological - not human - history, but they do happen.

Still, even with a big one, if you're clear on the other side of the world and have enough canned food to last a few years, and other supplies, you'd make it through. Civilization could be destroyed though.
posted by -harlequin- at 7:27 PM on May 7, 2012

Have you ever heard of Eta Carinae? It's about 8,000 light years away from us.

It's an immense star. Current estimates are somewhere between 100 and 150 solar masses. Stars that large are right on the ragged edge of blowing themselves up; it's the upper limit of how big a star can be and hold together. And they don't hold together for very long, even under the best of circumstances.

Stars that big burn really, really hot. Eta Carinae produces about 5 million times the output of our sun. Stars that large rarely survive more than a few million years, and then they detonate in what astronomers refer to as a "hypernova". A hypernova makes an ordinary supernova look like a firecracker.

Hypernovas create truly immense amounts of gamma radiation. It is thought that most of that is ejected out the poles of the star, and it turns out that the poles of Eta Carinae don't point at us. (Whew!) But no one really knows for sure how much would go out in other directions (i.e. towards us), and when it does detonate -- which could be any time -- the resulting gamma ray burst could well be an ecological catastrophe for the Earth.

It isn't likely to exterminate all life, but it could reduce us back to single-celled organisms. It all depends on the intensity. At lesser levels, it could result in a mass extinction event greater than the one at the end of the Cretaceous.

There is a theory that the second largest mass-extinction event in Earth's history was caused by a hypernova, but there isn't really any solid evidence for that yet.

The actual extinction mechanism is twofold. First, the gamma rays themselves are deadly, and the part of the surface exposed to them would be a slaughterhouse. Second, a huge influx of gamma rays would deplete a large percentage of atmospheric ozone (maybe as much as half). Then solar ultraviolet would kill off almost everything on land on the whole planet, even the parts that weren't exposed to the gamma ray burst.
posted by Chocolate Pickle at 7:35 PM on May 7, 2012 [1 favorite]

John Barnes's Mother of Storms (1994) uses the clathrate gun hypothesis to set off a massive planet-enveloping storm that almost kills us all. Very gripping book, as I recall.
posted by wdenton at 7:37 PM on May 7, 2012

Three realistic scenarios that turned out to be false:

Not sure if this falls under nuclear bombs, but when preparing to split the atom, it wasn't known if the chain reaction would stop. (As in, scientists were pretty darn sure it would, but the idea it might not did receive some consideration). This was a world-destroying scenario.

Likewise, when preparing to detonate the first atomic bomb, Fermi offered to wager on whether the bomb would ignite the atmosphere, and if so, if it would wipe out life in New Mexico, or the entire world.

Similarly, more recently, the fears of micro black holes being generated by the LHC then growing inside Earth. Again, after studying the issue, it was deemed extraordinarily unlikely, but the issue required study.

Whatever today's "We're pretty sure this button won't destroy the world" is, it's probably classified for now :)
posted by -harlequin- at 7:39 PM on May 7, 2012 [1 favorite]

The extinction of bees. No crop pollination means no food, for us and for the animals we eat.

Not correct. Honey bees are much less important to our food chain than some people think. In particular, grains don't depend on insect pollinators at all, so extinction of bees wouldn't affect production of corn, wheat, rice, barley, rye...

Second, honey bees are not the only insect pollinators. There are many others, including bumble bees, carpenter bees, and a fair number of insects which aren't bees at all (wasps, flies, butterflies, moths, beetles).

The current problems that honey bees are having don't affect the other bees, or the non-bee pollinators.
posted by Chocolate Pickle at 7:42 PM on May 7, 2012 [12 favorites]

Seconding the bees. Apparently we're approaching a bit of a crisis there right now, with a virus hitting bee colonies.
posted by Jubey at 7:43 PM on May 7, 2012

They say that once the bees are gone, we have four years of no pollination before everything collapses.
posted by Jubey at 7:45 PM on May 7, 2012

Physicists have questioned whether the vacuum of space is the true lowest energy state of the universe. If we are living in a false vacuum, it could collapse at any time. Since this would mean the end of the laws of physics as we know them, it would also be pretty bad news for life.
posted by drdanger at 7:53 PM on May 7, 2012 [4 favorites]

Perhaps the plot of Children of Men where something (chemicals in food/water/atmosphere, etc) led to the inability for humans to reproduce? That wipes out the whole population in one generation.
While it seems a bit inconceivable that the entire planet would suddenly be afflicted at once, you could make a case for something atmospheric that spreads quickly with no way to defend against it.
posted by trivia genius at 7:54 PM on May 7, 2012

The extinction of bees

They say that once the bees are gone, we have four years of no pollination before everything collapses.

Seconding the bees. Apparently we're approaching a bit of a crisis there right now, with a virus hitting bee colonies.

Think about the calories you ate yesterday, and then think about the fraction which bees were responsible for pollinating. I find the bee situation as disturbing as anyone--and if every domestic honeybee in the world disappeared tomorrow, it would certainly affect what we ate over the next few decades--but I think the extent to which our food supply absolutely depends on the pollination services of one domesticated species is often dramatically oversold in the interest of creating a narrative as compelling as (for instance) global warming.
posted by pullayup at 8:04 PM on May 7, 2012 [1 favorite]

Have you ever heard of Eta Carinae? It's about 8,000 light years away from us.

Current thinking is that η Carinae blowing its top will be one hell of a show, but not harmful to us. η Carinae is believed to be a Wolf-Rayet star orbiting a large companion, with a total system mass of about 100 solar masses, but we really can't tell, because it's thrown off so much mass that we can't actually see it.

However, because it *has* thrown off so much mass, we're really confident of the spin orientation, and it doesn't point at us. Thankfully, it appears *none* of the "close by" -- as if 2500 parsecs is close -- WR stars have a spin axis pointed directly at us. So, the Gamma Ray Burst of Doom scenario appears to be out of play.

When it -- or WR104 -- does finally do the Type Ic Supernova Boogie -- it's likely to be a hell of a show. Clearly visible by day, probably somewhere on the order of -15 magnitude, which is "I can read a book by that" levels of light. The full moon is -12.74 to -12.92, and one lux is -14, so we're talking about a point source that's only one millionth of the sun's brightness. To give an idea of how OMG BRIGHT that is, the brightest star in the sky is 2.5x1010 dimmer than the sun, so we're looking at a point source that's 2500x brighter than Sirius, or 7 times brighter than the full moon.

But back to the topic. A little googling tells me that one theory states that the Ordovician-Silurian extinction event may have been caused by a "nearby" Gamma Ray Burst, where "nearby" is 6000 light years.
posted by eriko at 8:07 PM on May 7, 2012 [3 favorites]

Exit Mundi may be an interesting site for you to browse. It's "a collection of end-of-world scenarios" - and while some of them are pretty ridiculous (they examine how a zombie apocalypse would work), others are also science-based and may at least offer a place to start more research.
posted by EmpressCallipygos at 8:44 PM on May 7, 2012 [2 favorites]

More on bees: the two most important crops for feeding livestock are corn and alfalfa. Corn as a grain doesn't rely on insects for pollination at all.

Alfalfa is a legume, and it can be pollinated by honey bees. But the best pollinator for it is the Alfalfa Leafcutter Bee, which is not closely related to the honeybee. It also isn't having any problems.

Despite the name, it doesn't concentrate exclusively on alfalfa; it also pollinates other crops. It's gone feral and is found all over the place.

Another major pollinator is the Orchard Mason Bee, which is one of the primary pollinators of apples and other orchard crops.

There's been a huge amount of hype about the problems that honey bees are having, but most of it has been hysterical shrieking with little basis in fact. The Honey Bee Colony Collapse Disorder is emphatically not a potential extinction event for the human race.
posted by Chocolate Pickle at 9:01 PM on May 7, 2012 [1 favorite]

It wouldn't even have to be a bio-engineered plague. Something a little nastier than the 1918 Spanish flu could put us in a world of hurt, especially if it spread too fast for governments to respond or enough people got infected to overwhelm health care systems. You'd potentially have small isolated pockets that could survive (the Madagascar problem from Pandemic), but consider the way something like that could spread given modern air travel and the way everyone moves around.

Or they've found antibiotic resistant bacteria from 4 million years ago. Considering that, I think it's reasonably feasible there's something millions of years old lurking in a cave somewhere that could really mess us up.
posted by Ghostride The Whip at 9:06 PM on May 7, 2012

If you're just brainstorming, the Keter Files on the SCP Archives can give you some inspiration. It's basically a giant collection of fictional files on items/phenomena from the collective imaginations of the denizens of the interwebz. They're all written in a scientific documentation-type format, and span some wildly creative ideas far beyond the oh-noes-zombie-plague-nuclear-bomb scenarios that you usually see.
posted by Conspire at 9:13 PM on May 7, 2012 [4 favorites]

The whole gray goo thing is "Skippy Goes to Venus" stuff if you take a moment to think about what makes molecular bonds form and break. It's an issue of kinetics - once you make a molecule big enough to have enzymatic sites to cut all the different bonds out there, the Einstein-Stokes equation would pretty much tell it to get in line behind the loofah sponge as a force that is slowly grinding humanity into a fine powder. And while it's waiting in line the gray gooification molecules would be just as likely to grind on one another.

Wiping out humanity with a disease is also pretty unlikely as there would almost certainly be some individuals who would be immune to whatever came down the pike. It might do a pretty efficient number on civilization though, but once we're knocked back to wandering tribes it's hard to imagine a pandemic taking place.
posted by Kid Charlemagne at 10:17 PM on May 7, 2012

Single catastrophic effects can be compensated for. Big space rock hitting the earth? Maybe microenvironments in mountain valleys afford survivability. &c.

It's when multiple events happen. Bad bad bad coincidences are the stuff of drama. One disaster is anticipitated and prepared for? Preparations are counter productive for the preventation/amelioration of the second.

Viruses are very scary but are actually pretty limiting; however, if the calculus of virulence/lethality runs away, it could potentially run too far and kill most of a population and leave the virus without a host.

Especially if you work into the plot that a comet nucleus (containing alien DNA/RNA/analogues that interact with terrestrial cells) crashes into the earth and creates a nuclear winter/accelerated-global-climate-change scenario.


Global climate change leading to a different distribution of people - concentrated masses in cities. Plus contagion - damaging virus with scary easy transmission vectors.


Our sun turning into a red giant is estimated to occur in about 5 billion years.

The sun could be a lot more capricious than humanity has had records observing it. It (the sun) might have a hiccup that fries part of earth. Depending on how long that hiccup lasts, figure 1/2 to 3/4 of earth's surface population as fried. But it's already been done in short story form, probably more times than I've encountered.
posted by porpoise at 10:42 PM on May 7, 2012

How about honeybees plus genetically modified "terminator" technology for rice, wheat, and soy somehow running amok. Is that realistic enough? That link says "Late in 2006, Monsanto acquired Delta and Pine Land company, along with its greenhouse tests of Terminator seeds and rights to its Canadian patent on Terminator granted on October 11 2005. D&PL has long vowed to commercialize Terminator, targeting rice, wheat and soy in particular." Combine that with with ocean acidification and depleted fisheries, limited wild animal populations, and a high human population that could quickly hunt those animals into near-extinction -- would that do it?
posted by salvia at 11:41 PM on May 7, 2012 [1 favorite]

Pollen bioengineered as a weapon.
And you thought your allergies were a bitch......
posted by Bighappyfunhouse at 11:49 PM on May 7, 2012

Kid Charlemagne: Wiping out humanity with a disease is also pretty unlikely as there would almost certainly be some individuals who would be immune to whatever came down the pike.

Well, I wonder. If we assume some sort of very efficient plague -- say, an antibiotic-resistant, rapidly mutating strain of pneumonic plague that would wipe out, say 95% of the population within the course of a couple of years. Survivors would be forced to organize very quickly to gather and preserve food to survive the first post-plague winter, and inevitably some groups would starve, others would be marauded, still others would succumb to influenza, infection, food poisoning and various ills that, without medical care can easily turn fatal.

Those who survive the first winter (or the first monsoon season or whatever big annual bout of bad weather strikes that part of the globe) would then be such a fragmentary group that humanity's place in the predator/prey system would be vastly altered. How long could one survive in a city, for example, outnumbered by a thousand feral cats and dogs to each human-- not to mention rats?

I don't think it's too far-fetched a scenario that under these conditions human life might be extinct within a few generations.
posted by La Cieca at 1:05 AM on May 8, 2012

La Cieca: "Kid Charlemagne: Wiping out humanity with a disease is also pretty unlikely as there would almost certainly be some individuals who would be immune to whatever came down the pike.

Well, I wonder. If we assume some sort of very efficient plague -- say, an antibiotic-resistant, rapidly mutating strain of pneumonic plague that would wipe out, say 95% of the population within the course of a couple of years (....) I don't think it's too far-fetched a scenario that under these conditions human life might be extinct within a few generations.

Doubt it. Even if it wiped out 99% of the world's population there would still be about 68.5 million people left. That's about how many were around between 500-1000 BC and they all did fine. True, the population would be much less dense, and most people have no idea how to live in a world without society as we know it and convenient technology, but I think enough would figure it out to keep the human race alive (and growing).
posted by Defenestrator at 1:24 AM on May 8, 2012

Lack of carbon dioxide. A few sleeps away, but rather inevitable. Timeline of the far future.
posted by shoesfullofdust at 2:03 AM on May 8, 2012 [1 favorite]

Martin Rees, the UK Astronomer Royal, wrote a book a number of years ago called "Our Final Century", on exactly this subject. Chasing the book on Wikipedia, I came across a link to a page which describes all kinds of risks to us or the planet.

The end of civilization is quite possible, maybe even probable. It'll take something quite out of the ordinary to wipe us out as a species, imo.
posted by daveje at 3:41 AM on May 8, 2012

Our part of the galaxy is actually in a bubble within a bubble. As I understand it, we're in the Local Fluff, which is in the Local Bubble, and we are headed for the Loop I Bubble. They are all in the Interstellar Medium. If you want to visualize it, we're in the white part, headed for the blue part, here.

- ... which means, if we hit one of the pink parts, molecular clouds (good places for stellar nurseries), things could get dark and rocky. Literally.
- Some idiot starts generating lots of neutrinos, which changes the rate of decay for some nuclear elements (jury's still out on that). Since decay is an integral part of the geothermal gradient (keeps us warm), Snowball Earth is created. Or we fry. Pick one.
- The doomsday device I was told about as a kid is real. I haven't seen it described (this is the closest), so . . .
- The missing Dark Matter is found right as it passes close to us.
- Airborne STD prevents fertilization. Everyone catches it. No one can have kids as a result.
- Revelation turns out to be real.
- Cannibalism becomes trendy.
posted by jwells at 6:26 AM on May 8, 2012

How about honeybees plus genetically modified "terminator" technology for rice, wheat, and soy somehow running amok. Is that realistic enough?

How does a gene that causes sterility get into the next generation?
posted by Kid Charlemagne at 4:15 PM on May 8, 2012

I know I'm late to the party, but I have been thinking about a scenario lately.

In the early 80's, Minneapolis (as well as many other places in the US) fell victim to Dutch Elm Disease. I remember my dad and our neighbors drenching the roots of our beautiful Elm trees in a futile attempt to save them. Alas, the disease claimed the vast, vast majority of Elm trees.

I was thinking about how sad that was - but how lucky we are that the disease was only specific to that one kind of tree. If there were a general tree blight - one that took out ALL trees with the same speed as Dutch Elm Disease (and people were helpless to do anything), that would be truly fucking scary.
posted by Elly Vortex at 4:50 PM on May 8, 2012

salvia writes "How about honeybees plus genetically modified 'terminator' technology for rice, wheat, and soy somehow running amok."

Lots of people would die if we had no insect pollinators and every single rice, wheat and soy plant died. But we'd still have lots of other grains like rye, barley and canola. We'd still have corn. We'd still have crops like potatoes and bananas that propagate by cloning or cuttings. And we'd still have many wind pollinated plants. The human species would survive. If nothing else goat herders feeding their stock on perennial grasses.
posted by Mitheral at 6:07 PM on May 8, 2012

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