Beware General Visible Prey

Charles Stross recently on possible future great filters:

So IO9 ran a piece by George Dvorsky on ways we could wreck the solar system. And then Anders Sandberg responded in depth on the subject of existential risks, asking what conceivable threats have big enough spatial reach to threaten an interplanetary or star-faring civilization. … The implication of an [future great filter] is that it doesn’t specifically work against life, it works against interplanetary colonization. … much as Kessler syndrome could effectively block all access to low Earth orbit as a side-effect of carelessly launching too much space junk. Here are some example scenarios: …

Simplistic warfare: … Today’s boringly old-hat chemical rockets, even in the absence of nuclear warheads, are formidably destructive weapons. … War, or other resource conflicts, within a polity capable of rapid interplanetary or even slow interstellar flight, is a horrible prospect.

Irreducible complexity: I take issue with one of Anders’ assumptions, which is that a multi-planet civilization is … not just … distributed, but it will almost by necessity have fairly self-sufficient habitats that could act as seeds for a new civilization if they survive. … I doubt that we could make a self-sufficient habitat that was capable of maintaining its infrastructure and perpetuating and refreshing its human culture with a population any smaller than high-single-digit millions. … Building robust self-sufficient off-world habitats … is vastly more expensive than building an off-world outpost and shipping rations there, as we do with Antarctica. …

Griefers: … All it takes is one civilization of alien ass-hat griefers who send out just one Von Neumann Probe programmed to replicate, build N-D lasers, and zap any planet showing signs of technological civilization, and the result is a galaxy sterile of interplanetary civilizations until the end of the stelliferous era. (more)

These are indeed scenarios of concern. But I find it hard to see how, by themselves, they could add up to a big future filter.

On griefers (aka “berserkers”), a griefer equilibrium seems to me unstable to their trying sometimes to switch to rapid growth within a sufficiently large volume that they seem to control. Sometimes that will fail, but once it succeeds enough then competing griefers have little chance to stop them. Yes there’s a chance the first civilization to make them didn’t think to encode that strategy, but that seems a pretty small filter factor.

On simple war, I find it hard to see how war has a substantial chance of killing everyone unless the minimum viable civilization size is large. And I agree that this min size gets bigger for humans in space, who are more fragile there. But it should get smaller for smart robots in space, or on Earth, especially if production becomes more local via nano-factories. The chance that the last big bomb used in a war happens to kill off the last viable group of survivors seems to me relatively small.

Of course none of these chances are low enough to justify complacency. We should explore such scenarios, and work to prevent them. But we should work even harder to find more worrisome scenarios.

So let me explain my nightmare scenario: general non-diminishing prey. Consider the classic post-apocalyptic scenario, such as described in The Road. Desperate starving people ignore the need to save and build for the future, and grab any food they can find, including each other. First all the non-human food is gone, then all the people.

Such situations have been modeled formally via “predator-prey dynamics”:

Volterra_lotka_dynamicsThese are differential equations giving the rates at which counts of predators and prey grow or decline as a function of each other. The standard formulation has a key term whereby prey count falls in proportional to the product of the predator count and the prey count. This formulation embodies an important feature of diminishing returns: the fewer prey are left, the harder it is for predators to find and eat them.

Without enough such diminishing returns, any excess of predators quickly leads to the extinction of prey, followed quickly by the extinction of predators. For example, when starving humans are given easy access to granaries, such granaries are emptied quickly. Not made low; emptied. Which is why granaries in famines are usually either well-protected, or empty.

In nature, there are usually many kinds of predators, and even more kinds of prey. So the real predator-prey dynamic is high-dimensional. The pairwise relations between most predators and preys do in fact usually involve strongly diminishing returns, both because predators must usually search for prey, and because some prey hiding places are much better than others.

If the relation between any one pair of predator and prey types happens to have no diminishing returns, then that particular type of prey will go extinct whenever there is a big enough excess of that particular type of predator. Since this selects against such prey, the prey we see in nature almost all have diminishing returns for all their practical predators.

Humans are general predators, able to eat a great many kinds of prey. And within human societies humans are also relatively general kinds of prey, since we mostly all use the same kinds of resources. So when humans prey on humans, the human prey can more easily go extinct.

For foragers, a key limit on human predation was simple distance. Foragers lived far apart, and were unpredictably located. Also, foragers had little physical property to grab, wives were not treated as property, and land was too plentiful to be worth grabbing. These limits mattered less for farmers, who did predate often via war.

The usual source of diminishing returns in farmer war predation has been the wide range of protection in places to hide; humans have often run to the mountains, jungle, or sea to escape human predators. Even so, humans and proto-humans have quite often driven one another to local relative extinction.

While the extinction of some kinds of humans relative to others has been common, the extinction of all humans in an area has been much less common. This is in part because, when there has been a local excess of humans, most have focused on non-human prey. Such prey are diverse, and most have strongly diminishing returns to human predation.

Even if humans expand into the solar system, and even if they create robot descendants, we expect our descendants to remain relatively general predators, at least for a long while. We also expect the physical resources that they collect to constitute relatively general prey, useful to a wide range of our descendants. Furthermore, we expect nature that isn’t domesticated or descended from humans to hold a decreasing quantity of useful resources.

Thus the future predator-prey dynamic should become lower dimensional than it has been in the past. To a perhaps useful approximation, there’d be only a few kinds of predators and prey. Which raises the key question: how strong are the diminishing returns to predation in that new world? That is, when some of our descendants hunt down others to grab resources, how fast does that task get harder as fewer prey remain?

One source of diminishing returns in predation is a diversity of approaches and interfaces. The more different are the methods that prey use to create and store value, the smaller the fraction of that value a predator can obtain via a simple hostile takeover. This increases the ratio of how hard prey and prey fight. As many have noted, in nature prey fight for their lives, while predators fight only for a meal. Even so, nature still has plenty of predation. Even if predators gain only part of the value contained in prey, they still predate if that costs them even less than this value.

As I said above, the main source of diminishing returns in predation among foragers was travel cost, and among farmers it was the diversity of physical places to run and hide. Such effects might still protect our descendants from predator-prey-dynamic extinction, even if they have only one kind of predator and prey. Alas, we have good reasons to fear that these factors may less protect our descendants.

The basic problem here is our improving techs for travel, communication, and surveillance. We are steadily able to move bits and people more cheaply, and to more cheaply and accurately watch spaces for activity. Yes moving out into the solar system would put more distance between things, and make them harder to see. But that one-time effect will be quickly overwhelmed by improving tech.

A colonized solar system is plausibly a place where predators can see most any civilized activities of any substantial magnitude, and get to them easily if not quickly. So if we ever reach a point where predators fight to grab civilized resources with little concern to save some for the future, they might be able to find and grab pretty much everything in the solar system. Much as easy-access granaries are quickly emptied in a famine.

Whether extinction results from such a scenario depends how small are minimum viable civilization seeds, how obscure and well protected are the nooks and crannies in which they might hide, and how many of them exist and try to hide. Yes, hidden viable seeds drifting at near light-speed to other stars could prevent extinction, but such a prey-collapse scenario could play out well before such seeds are feasible.

So, bottom line, the future great filter scenario that most concerns me is one where our solar-system-bound descendants have killed most of nature, can’t yet colonize other stars, are general predators and prey of each other, and have fallen into a short-term-predatory-focus equilibrium where predators can easily see and travel to most all prey. Yes there are about a hundred billion comets way out there circling the sun, but even that seems a small enough number for predators to careful map and track all of them.

Worry about prey-extinction scenarios like this is a reason I’ve focused on hidden refuges as protection from existential risk. Nick Beckstead has argued against refuges saying:

The most likely ways in which improved refuges could help humanity recover from a global catastrophe are scenarios in which well-stocked refuges with appropriately trained people help civilization to recover after a catastrophe that leaves a substantial portion of humanity alive but disrupts industrial and agricultural infrastructure, and scenarios in which only people in constantly-staffed refuges survive a pandemic purposely engineered to cause human extinction. I would guess that, in the former case, resources and people stocked in refuges would play a relatively small role in helping humanity to recover because they would represent a small share of relevant people and resources. The latter case strikes me as relatively far-fetched and I would guess it would be very challenging to do much better than the largely uncontacted peoples in terms of ensuring the survival of the species. (more)

Nick does at one point seem to point to the scenario that concerns me:

If a refuge is sufficiently isolated and/or secret, it would be easier to ensure that everyone in the refuge had an adequate food supply, even if that meant an inegalitarian food distribution.

But he doesn’t appear to think this relevant for his conclusions. In contrast, I fear that a predatory-collapse scenario is the most likely future great filter, where unequal survival key to preventing extinction.

Added 10a: Of course the concern isn’t just that some parties would have short term orientations, but that most would pursue short-term predation so vigorously that they force most everyone to put in similar effort levels, even if they take have long-term view. When enemies mass on the border, one might have to turn farmers into soldiers to resist them, even if it is harvest time.

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  • Cambias

    Two objections — which are really the same objection rotated in spacetime:

    The “prey-on-themselves-until-nobody’s-left” filter has to apply to every civilization that has arisen in the Galaxy. NONE of them managed a stable democracy or even an efficient tyranny to keep the predators in check? That seems unlikely, to say the least, especially if you consider the following:

    My second objection is that this situation has been possible (indeed much MORE possible) throughout human history. Why did Western Europe recover after the fall of Rome? Or after the Black Death? Or the World Wars? If the diminishing cycle of predation is so devastating, how come it hasn’t already happened? This suggests that it’s not as bad as painted — that humans, at any rate, do have mechanisms and strategies to break out of it. It’s extremely noteworthy that your best example is a work of fiction, _The Road_, rather than a historical situation.

    • http://overcomingbias.com RobinHanson

      This doesn’t have to be the whole filter to be part of it. And past population collapses hit diminishing returns as humans predate mostly on a diverse and evasive nature.

  • lump1

    Of course, you’re not talking about literal predation, where the predators chew our flesh and gnaw our bones. I assume that you mean that the predators will grab our stuff. I can imagine that once they have it, they will want more stuff, and maybe every colony in the solar system will succumb to their raids.

    But here the disanalogy with flesh-eating predation becomes important. Once the predators killed all the prey they will have *lots of durable stuff*, and that stuff will presumably enhance their lives. (If it wouldn’t, why work so hard to grab it?) So now they can kick back and enjoy their spoils, right? Whether they want farmland, mines, computers or solar cells, all this productive stuff will be theirs. They won’t be like lions who killed the last gazelle, they’ll be more like Pizzaro, who killed all meaningful Inca resistance and could impose his will on the resources of a whole continent. That may be nasty, but it’s hardly extinction.

    Flesh munching predators have a metabolism, and they die if they go too long between predations. The sort of metaphorical predators you talk about don’t have an analogue of a metabolism. Is there a tribe in human history that relied on conquest for its very survival, because they would literally die out if they went too long without killing others?

    • http://overcomingbias.com RobinHanson

      If everyone is both prey and predator, then they might keep fighting and depleting their capital. Sure they might agree to a big truce and then the winners could enjoy their spoils. But what if there is no truce?

      • lump1

        Aren’t there people who model this kind of thing? I don’t know that literature, but here’s what I predict it says: When given the choice between predation (sub-zero-sum) and cooperation (above-zero-sum), the best move depends on the following factors: 1. cost in effort and danger to vanquishing the prey (increases as prey get less dense) 2. net subjective value of their stuff, which declines on the margin, the more stuff you have, 3. the opportunity costs of not cooperating with them, whereby you forego the possibility of trade, mutual protection, economies of scale, etc. My point is, even if predation is rational among dense, poor agents, it doesn’t remain rational indefinitely. At some point it makes sense to consolidate your victories.

        You’re the economist – not me – so I doubt that the answer to your worry is something so Econ 101. But I just don’t get why this isn’t the answer. In order for predators to turn on each other until only one remains, wouldn’t they have to inexplicably irrational towards the end? And wouldn’t agents with such dispositions be vanquished earlier by a coalition of powers who are capable of genuine cooperation? And even if one single power did remain, it’s not like it would starve to death without more prey. It would command all the resources in the solar system, and might become the galaxy’s berserker, but that’s very different from extinction.

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  • http://praxtime.com/ Nathan Taylor (praxtime)

    If technology makes it more likely for a predator-prey war to deplete resources to the point of extinction, it simulataneously makes it easier to create a Noah’s ark to escape the catastrophe. Assume Stross is right and it takes let’s say 8 million people to sustain our current civilization. If we go back in time to the year 5000 BC, clearly that number would be less. And if we go forward 5000 or even 500 years, again I think the number would be less. In the future easier and cheaper to store computerized culture and knowledge, and easier to build an ark with egg and sperm and seed. So while it may take 8 million to keep tech going right now, we may also be at a “peak headcount to regrow civilization” point. Eventaully an ark could be built with no people, just machines. At which point we get to Von Nueman probes – self replicating machines which can build themselves, and with cheap tech for memory storage, potentially restart civilization. Even a biological one.

    My point here is that even if a short term war of all on all forces the complete depletion of all stocks, the relative cost of building an ark also goes down at the same time. And of course we have to assume people in the future won’t be unaware of what’s happening.

    So even if this is the most likely future filter, I think the downside risk could be greatly mitigated by the relatively decreasing cost of building an ark to wait out the storm and restart. Of course at some point you just shoot that ark off to nearby stars and we are past the great filter risk for our solar system. So the force of this argument is highly dependent on which technolgies have the fastest relative improvement.

    • lump1

      So are you saying that if the future intelligence of the solar system starts eating itself into extinction, the cost of building an ark to wait this out will be low, because the extinction will happen rather fast, so the ark doesn’t have to be dormant for very long?

      That would work only if the last of the predators didn’t “salt the earth” on their way out, leaving behind Von Neumann machines to prevent the rise of any rivals. Much more promising is to make an ark that actually travels – perhaps slowly – to another planetary system, and starts the reboot there. I don’t think that our futurists are thinking hard enough about how such a seed ship could be made with near-future tech. I wish some group would put their heads together and make a list of what tech we need to develop in order to create a seed ship that would actually have a good chance of sprouting. In essence, it would need to be a very small 3D printer, a simple computer, a small power source and a great deal of data, stored in some robust way, with parity files for error correction. Right now, the most dense form of data storage we have is DNA, where we can encode gigabytes in a cubic micron.

      The simple 3D printer would use the materials at the destination to build a more sophisticated 3D printer, which would produce scaled up material extraction and construction devices, until they had tools which could make a DNA reader, and a bio-replicator that could turn genetic data into viable germ cells, which could be incubated in some sort of artificial wombs, etc. If the plans we send are good enough, this simple seed ship could build a massive space station habitat from local asteroids, and populate it with diversity of terrestrial life, including people, initially parented by AI. Conceivably, all the material we’d need to send would fit into the volume of a beer keg, which would be easy to accelerate and decelerate using non-exotic propulsion tech. It might also not be that insanely expensive, and fast tracking the relevant research would have obviously useful technological spinoffs. So I think the engineering details of building a genuine ark ship should get more attention from futurists. Once we start making these, I will feel like we will have beaten the filters, so I want it to be asap.

      • http://praxtime.com/ Nathan Taylor (praxtime)

        To clarify, my argument is that if Von Nueman probe techonlogy advances faster than solar system wide civilization hits severe resource constraints, causing an associated prey-predator war, then the likelihood of this being the biggest future filter decreases greatly. I lean toward believing this is true. Easier to build a von nueman probe than fill the solar system beyond capacity. But who knows.

  • jpt4

    Human technology has already attained the cusp of species filtering destructive power in the form of submarine launched thermonuclear missiles. For 70 years, however, both their use (and in hindsight, committed threat-of-use) have been minimal; the general decline in the incidence of total war, and open skepticism of its foregoing applicability as an option of statecraft, imputes to the nuke-builders not a hunger for predation, elastic in proportion to their prowess, but a veritable sober-mindedness in comparison to the wanton Kabinettskriege, revolutions, and Imperial-era brinksmanship immediately preceeding.

    Why then would not the development of yet greater weaponry not spur the creation of equally more restraining compensation structures? Some possible confounds to a simple extrapolation:
    1. Nuclear weapons are currently resource-intensive, with effective Filter-grade capability limited to a half-dozen nation states. Future inelastic prey reduction will be enabled by low activation energy Filter-grade technology.
    2. Because Mutually Assured Destruction is modelled as a threshold event, predators only need to make the isolated decision not to cross the point of no return; Future War will end the species by a thousand cuts, and a thousand high time preference choices.
    Counter: The longer the chain of behavior required to effect a Filtration, the more opportunities to prevent it.
    3. World-endlingly powerful weapons do not in and of themselves inspire reluctance towards their maximum potential use; the actual psychological check is obtained by observing their use, as at Hiroshima and Nagasaki. Future Filter-grade weapons will require only one activation, a visceral repulsion against which will not have the opportunity to be culturally engrained.
    4. Alternatively, the invention of nuclear weapons came at a historically fortuitous time, on the tails of the greatest conventional (non-existentially-threatening) total war, the subsequent loathing of which subsumed and extended to nuclear weapons.

    In short, if the salient part of the rampant militancy of humanity is the absence of clearly apprehensible costs, then very obviously strong walls and big sticks might form a stable attractor of deterrence, as demonstrated by the history of nuclear weapons policy, even unto Dyson Sphere lasers and redirectable asteroids.

  • Phil H

    I can’t see much reason to think that the particular coincidence of technological abilities and disabilities that you posit will actually happen.

    I think the gap between us colonising the solar system and colonising other systems will be small. You suggest we would have technology sufficiently powerful to “kill nature”, but not sufficiently powerful to recreate human habitats or to instantiate ourselves in other media. Such a phase might happen, or it might not; it would be a significant coincidence, I think, if it happened to fall at just the time in between solar system colonisation and extra-solar spread.

    • http://overcomingbias.com RobinHanson

      I think you underestimate the difference in difficulty in colonizing a solar system and colonizing other stars.

      • http://www.quora.com/Richard-Treitel/answers Richard T

        The Oort cloud is said to be about a light-year in radius. And I don’t think the cutoff is all that sharp. Shall we take bets on how big the cloud around Alpha Centauri is?

  • Silent Cal

    Can you elaborate on farmer era predation? That era seems dominated by long term predation in the form of kleptocracy, and the superiority of that option seems like the main check on shorter term predation.

    • Silent Cal

      Oh, this is kind of what your next post is about.

  • chaosmosis

    Perhaps similarly, maybe the reason there appears to be a Great Filter is that smart civilizations are hiding from everyone else?

    • http://overcomingbias.com RobinHanson

      That is the “griefer” scenario Stross mentioned.

      • chaosmosis

        Oh. Not sure what I was thinking there.

        I’d question the assumption that it’s possible to defensively control a sphere of territory that you then build within. It would be trivial for a society outside the sphere to lob threats towards it. You’re conflating machines that detect then destroy advanced civilizations with machines that detect then destroy von Neumann probes, I think, the difference is that probes are smaller and so can go undetectable. You’d need to cover the surface area of your entire sphere of influence with sensors to prevent enemy probes from reaching your planets. And doing that gets harder and harder as your sphere expands in size.

      • chaosmosis

        Urgh. I realized I was being dumb and tried to delete this comment, but instead the website removed the comment from my control. Just ignore this.

      • http://overcomingbias.com RobinHanson

        If you simultaneously grow fast in a large sphere, and if you in fact mostly control that sphere, then the probes they send from inside can’t do that much damage, and the probes they send from outside take too long to get there. Once you have densely colonized a large volume you win on defending the surface area vs huge volume resources to draw upon.

      • IMASBA

        If you control your sphere then defense is always relatively easy: a lone berserker (or at least only a small number of them, given the vastness of space) enters your sphere after traveling for god knows how long, you have 20 anti-berserkers (cheaper than berserkers because they don’t have to travel as far/fast) converge on it immediately, plus nearby resources and production facilities to build a million more anti-berserkers.

      • chaosmosis

        That assumes detection is easy. But it is easy to make detection easy if your occupied territory is smaller than your Anti-berserker sphere of influence, which is what made me realize I was being silly and attempt to delete that comment.

      • IMASBA

        Yes, you’d have your anti-berserker capabilities range to outside of your sphere. But even if a berserker gets through it’ll get spotted and intercepted (you’ll have defenses near your most important planets/bases too): after all, it has to get close to some important target before it can do any damage. If it tries to replicate inside your sphere or near it then that increased activity (heat output) will make it easier for you to detect the coming threat.

        Most of all your doctrine will be to delay berserkers because in most scenarios you can (re)build your defensive capabilities faster than they can receive reinforcements.

      • chaosmosis

        Is that how the math works out? I’d think that since the vast majority of the volume is empty, increasing volume would be a liability and become more and more disproportionately expensive. But, since defending unoccupied of the sphere of influence isn’t necessary, ultimately I agree with you.

  • Marcus135

    For the predator-prey scenario to play out in a time of solar colonization and great scientific progress then some weird regressive irrationality need to win out, like superior but defunct runaway constructs, artificial mind-virus pandemics, or some weird evolution of humans. It’s also a scenario local in scope, so not really “The Great Filter”, just one of many possible outcomes some species might face.

    Assuming the galaxy is in fact unexploited and clear of griefers, and assuming there is a single great filter ahead of us, I think it’s likely it will be quite near in time. It should happen before a species is well established in their star system, otherwise surely the window for galactic colonization in some manner will have been opened far enough for some to escape it (unless there is some vast technological leap required compared to colonizing the home system that I am unaware of, beyond the different scales in time and space?).

    If we assume a great filter exist which has not yet come to pass, then we must also accept that the probability of us passing through it is extremely slim. So, a filter that happens between where we are now and the colonization of the star system, with a very high extinction-rate. I don’t think nuclear technology or “total war” represent a high enough rate to be a good candidate, but it leads into another scenario – any species that have reached the nuclear age will have a keen interest in particle physic research. The theory is then that there exists an incredibly dangerous phenomenon related to particle physics research, and that this phenomenon is virtually impossible to infer with any certainty beforehand. This would in effect represent a keyhole only the most absurdly cautious of species will pass through (the ones not likely to become galaxy exploiters). In this scenario there is room for threats we think we know about, like surprisingly persistent black holes, or “unknown unknowns” out of left field. It seems scientists are convinced indeed that there is no possibility of persistent black holes 🙂 Assuming this phenomenon will only wreck the planet itself, then for it to be The Great Filter, it should consistently occur rather early, before a species is likely to have time to develop the technology to establish mature and self-sufficient industrial complexes and colonies in the rest of the star system.

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  • IMASBA

    Btw, this post touches on a current ecological issue. The diminishing returns on hunting rare prey explains why some species have been critically endangered for decades without fully going extinct (wrongly convincing some people that environmental activists were just being alarmist). Tigers are probably a good example: the remaining wild tigers are so widely dispersed that poachers can’t find them anymore, the species survives because it has the ability to find mates across huge distances (species that do not have this ability eventually go extinct when dispersed, but depending on lifespan this can take decades, even centuries when there is still sporadic mating, to current humans this can give the impression of such species doing ok).

  • bcg

    Doesn’t this end when random variation in predation abilities produces a super predator who takes everything? The predators you’re describing seem like foragers, wandering around for prey. But the really good predators would probably use threat of predation to extract tributes, more like farmers who cultivate their prey, a.k.a. empire.

    • IMASBA

      Empires come and go… (historically they’ve also been prone to civil wars that weakened them until they could no longer defend against external enemies, external enemies who may consist of seceded parts of the empire itself).

  • Tom_Craver

    A fGF needs to be nearly universal across all intelligent aliens that become space-faring, to explain the great silence.

    But even if the Predator-Prey extinction trap somehow were universal across all alien races, at least some should have lasted long enough to send self-replicating machines out into the galaxy.