The Growth Groove Game

My head is full of big history questions after spending two days at a related workshop.

How did humanity become so influential and powerful?  Apparently we found a growth groove that let us keep on accumulating power-enhancing innovations.  But what key features make this growth groove possible?

A great many features get mentioned, including brains, language, culture, fire, tools, large tribes, mind-reading, trade, specialization, domestication, trust, capital, machines, artificial power, cities, science, writing, printing, leisure, property, law, marriage, patents, and signaling.  They can all seem like plausible candidates, at least for some places and times.  But which features were how important?

It turns out that we just don't know.  But we do have some strong clues.  So a fun armchair game is to guess which were the key features.  But before you play, remember the game's key rule: your story must fit history as we know it.  So let's review that history.

A good measure of humanity's overall influence/power is "world product," and history is reasonably well summarized as:

  1. Animals appeared about a half billion years ago, and very slowly grew in their range of capabilities.  The biggest brains grew roughly exponentially.
  2. Roughly two million years ago, the niche filled by our human-like hunter-gatherer ancestors began to grow roughly exponentially in number (and in world product), doubling roughly every quarter million years,
  3. About ten thousand years ago, humans quickly adopted farming and transitioned to growing exponentially much faster, doubling in number roughly every thousand years,
  4. About two hundred years ago, human world product quickly transitioned to doubling about every fifteen years, as industry become common.

These "quick" transitions took much less than a previous doubling time, though more than a new doubling time. 

So human history consists of a few key growth modes.  During each mode, any tendencies for growth to decelerate, for example via exploring the best looking ideas first, were roughly balanced by other tendencies for growth to accelerate, for example via more powerful eras exploring more ideas.  So change falls into two important classes: most changes are part of some growth mode, helping to sustain it but not modifying its basic pattern of change, while three key changes begot enormous mode-changing revolutions. 

So our key questions are: what caused those three key changes, or equivalently, what key features sustain each growth mode?  But before you go wild proposing stories about which features were key to which modes, remember: your story about when a feature became a key to growth must match what we know about when that feature was how prominent. 

For example, it would be crazy to attribute the arrival of humans to writing, since writing abilities seems way beyond the earliest humans.  One might attribute the farming revolution to writing, but since the earliest known writing appeared well after farming started, you'd have to postulate that we'll find much earlier evidence of writing, and you'll also need a plausible story for how writing enabled farming to appear and to then sustain a faster growth rate.  If you wanted to attribute the industrial revolution to writing, you'd have to explain why there was a strong threshold effect, so that pre-1800 writing levels had weak growth rate effects, while post-1800 writing levels had strong effects.

To start the game play, let me describe my current best guesses.  While hunter-gatherers underwent large genetic changes, the key to their sustained growth may have been new mental features making it easier to pass on behavior innovations via culture, rather than via genes.  While culture-embodied change probably required big enough brains, and it was aided by language and large social groups, it is not clear how necessary were these last two features.

With domestication, I suspect that plants and animals directly embodied key innovations, making it far more useful to find and share new plants and animals than to find and share new ways to make arrows, shoes, etc.  Better seeds might let one colonize whole new territories, while better shoes usually only help a little. 

It is true that less-mobile farmers could invest more in heavy physical capital, and dense areas of farmers could more easily share innovations, specialize in production, and engage in long distance trade.  However, it is not clear how important these were.  Since there had long been some long distance trade, and some less-mobile and denser gatherers at rich fisheries, a threshold effect would be needed for mobility and density to be crucial to the farming revolution.

While the scientific revolution had little direct effect on the arrival and growth of industry, it created a prestigious cultural model for the formation of networks of experts talking to each other in other areas, especially agriculture.  I suspect networks of farming experts drove the initial industrial revolution in Britain, and other experts networks sustained the revolution as economic activity moved away from agriculture.   While capital intensity, leisure, printing, and good property rights probably helped, it is not clear they were necessary. 

Those are my guesses for now, though I'd love to change my mind to a story with stronger support.  Anyone got one?

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  • Will Pearson

    That the industrial revolution was driven somewhat by the improvements in agriculture is a well known hypothesis.

    http://en.wikipedia.org/wiki/British_Agricultural_Revolution

  • michael vassar

    I have repeatedly disputed the claim that the above facts constitute a reasonably accurate summary of what is known about history. Points can be fit to exponentials? Really? When one has a hand full of very unreliable points which were largely created by assuming an exponential and interpolating or extrapolating?

  • http://t-a-w.blogspot.com/ Tomasz Wegrzanowski

    I second the michael vassar’s objection, and don’t find this summary accurate at all. It is least inaccurate in the fourth indicated period, perhaps still marginally useful in third, but I’d be highly surprised to find any patterns like that in the first and second periods.

  • http://www.shefaly-yogendra.com/blog Shefaly

    I think human beings learning to draw upon synergies within their communities (agrarian societies where role divisions became clear and specialisations developed), and then identifying ways to cooperate with other communities (trade or indeed scientific collaboration) or compete with communities for resources such as territory, raw materials etc (war) is the crux of much development.

    So, short answer – communities. Not very different from the 2.0 version of the web.

    Of course along the way, shorthand related to trust and negotiation had to be developed but those I deem to be ‘second-order’ or ‘derivative’ constructs.

  • http://liveatthewitchtrials.blogspot.com/ davidc

    Profit motive? The badly named but good book “sex science and profits” gives this explanation
    http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/books/non-fiction/article3201917.ece

    “Formation of networks of experts talking to each other in other” idea is written about a lot in it.”A history of the world in six glasses” has a similar explanation of thef ormation of the royal society and it basis in coffee houses.

  • http://www.hegemonicon.com hegemonicon

    Best off the top of my head guess-each period reflects the point when groups of humans had accumulated enough knowledge to combine the things they knew into a new way of doing something.

    The start of the 2nd period was when humans had accumulated enough knowledge (of how to hunt, how to find shelter, etc) to start working together in groups of 50 or so to hunt/gather more efficiently. The start of the 3rd period was when they had accumulated enough knowledge (of cultivation, domestication, irrigation, etc) to start using agriculture to produce more food. The start of the 4th period was when humans had accumulated enough knowledge (of metalurgy, material properties, combustion) for the industrial revolution.

    Once knowledge reaches a certain level, and a certain spread through the population, it allows the formation of a new, better way of doing things.

  • http://profile.typepad.com/robinhanson Robin Hanson

    Will, that is basically accepted as fact. But the question is why farming suddenly improved so much.

    Michael and Tomasz, I’m just relying on standard sources for population and brain size estimates. This isn’t the place to argue with them.

    Shefaly, so what exactly changed about communities, and what enabled those changes?

    davidc, but profit motives have always been common.

    hegemonicon, there might be knowledge thresholds required for new ways of doing things, but why would those new ways of doing things enable growth to be so much faster?

  • http://www.hegemonicon.com hegemonicon

    Another best guess – the big changes come when we’re able to harness exponentially more energy (without having to expend a corresponding amount of energy to get it).

    1 person might be able to kill 1 antelope (or the ancient equivalent). 20 people might be able to kill a wooly mammoth, which provides the energy of 100 antelope. Agriculture gets you even more, by harnessing the power of the sun. Industry harnesses the power of combustion, and gets you even more. Each level gets you more energy – energy that can be relatively easily applied.

  • http://liveatthewitchtrials.blogspot.com/ davidc

    davidc, but profit motives have always been common.

    Good point. “The rise of the Western world” By Douglass Cecil North, Robert Paul Thomas and P.J. O’Rourke take On ‘The Wealth of Nations’ both put it down to “good property rights” but as you ask is that enough to explain the industrial revolution? A Farewell to Alms seems to put it down to some sort of genetic change in Britain. Apologies for just commenting a bibliography of books about the question. Just it is an interesting problem and these are the best explanations on it I have read.

  • Will Pearson

    Robin where do you want to stop the explanation?

    Do we need to explain why the scientific revolution happened when it did as well?

  • HH

    Robin, on your best guess: it strikes me that agriculture and the rise of investment associated with were the beginning of a trend toward peacefulness, in which violence became a costlier way of signaling and improving status. Investment meant having something to lose, such that jockeying for status using violence would have become much more costly. As such direct contests for status declined, others had to arise to take their place: signaling using wealth, for example. Such signaling depended more and more on mental abilities – calculating expected values of investments, maintaining networks of allies, learning technologies to improve one’s wealth, etc. These changes would have favored a bigger brain capable of more complex planning, incrementally leading us toward the benefits of the modern economies [specialization, trading, contracts, dispute resolution]. This trend is self-reinforcing and thus accelerates, and here we are now.

    “Another best guess – the big changes come when we’re able to harness exponentially more energy (without having to expend a corresponding amount of energy to get it).”

    If that’s your argument, the discussion should start with fire. Evidence shows that our brains had a growth spurt shortly after fire was first used for cooking. Experiments show that cooked food is digested far more efficiently, so that he same amount of food results in a bigger net energy consumption.

  • josh

    How about the joint stock company?

  • sdb

    Perhaps the reason is simply the total number of humans available to try new things.

  • http://profile.typepad.com/robinhanson Robin Hanson

    hegemonicon, your theory would seem to predict jumps between output levels, instead of the jumps between output growth rates that we see.

    davidc, genetic changes were too slow, unless there was some sharp threshold effect in getting “good enough” genes. Good property rights were feasible long long ago, so surely that could only be a part of the story.

    Will, well the more detail the better, but the bar is pretty low at the moment.

    HH, your story has only one transition, but we have three to explain.

    sdb, increasing growth rates with increasing numbers of people doesn’t predict sharp transitions.

  • http://macroethics.blogspot.com nazgulnarsil

    I agree with hegimonicon, it’s all about energy density. each epoch involves something that was formerly energy intensive becoming cheap. our next major step appears to be making information processing cheap.

  • http://williambswift.blogspot.com/ billswift

    The earliest one is purely biological and genetic. For the others, the best explanation I’ve seen is Julian Simon’s “The Great Breakthrough and Its Cause”, where he basically argues that human progress is a positive feedback cycle between increasing technology and increasing population. Higher population allows and encourages technological development which allows higher population which increases technology, etc, etc. His concentration in the book is on the takeoff of the industrial revolution over the last few centuries, but it looks applicable to earlier periods and transitions also.

  • http://timtyler.org/ Tim Tyler

    My take on this would centre around heritable information capacities:

    Human culture started around 3 billion years ago, fuelling brain growth in our ancestors – as memes made space for themselves – and invented hunting and fishing technologies that removed nutritionally-imposed limits on brain development.

    Some time later humans began to live together in large communities. That allowed mental specialisation. Up to that point, all human culture had been stored in a few types of mind – man, woman, shaman, chief. Communities allowed for many more roles, expanding the types of minds where ideas could find homes – this led to much more knowledge, writing money, religion etc.

    More recently, printing was invented – which made libraries more economically feasible, resulting in an explosion of knowledge.

    Recent developments in this general area include ubiquitous digitalisation, the formation of the internet, and machine intelligence.

  • Lord Duppy

    You’re forgetting something — our planet has ready-made sources of chemical energy. It’s hard to imagine how a civilization could get off the ground without wood, coal, natural gas, petroleum, &c. It wouldn’t be possible to invent other forms of energy production without using them first. We got lucky.

  • gwern

    Hegemonicon, Tim Tyler: One of the best things to do, if you have a hypothetical cause for the Industrial Revolution and the modern world, is to ask ‘and is this also true of China?’ (the Song, Ming, or Qing dynasties will do)

    A large European population sparked the IR? Then why didn’t China have an IR centuries or millennia before? Having metallurgy, gun powder, printing, and paper are enough? Then why didn’t Song and later China have an IR? England had coal reserves? China *invented* coal (cf. Marco Polo’s ‘burning rocks’). Fiat money, complex economic organizations etc. led to the IR? But then, how many centuries before Europe did China have things like ‘flying money’? Intensive agriculture is the explanation? China excelled in intensive agriculture, with incredible average yields for the time; certes, a rice paddy was more productive than an English fields…

    I subscribe to Clark’s view: explaining the IR is very very hard, and most of the conventional explanations just don’t work as universal explanations. (I particularly liked his material on how strong property rights were in medieval times, since it ties in well with Nick Szabo’s stuff.)

  • http://profile.typepad.com/riemannzeta Michael F. Martin

    While the scientific revolution had little direct effect on the arrival and growth of industry, it created a prestigious cultural model for the formation of networks of experts talking to each other in other areas, especially agriculture.

    Sounds exactly right to me. Note that as networks grow to larger and larger scales, new divisions of labor AND mechanisms for coordination among the different specializations become necessary to sustain the rate of growth. This is ultimately why power laws are not rigorously correct as an approximation for economic growth.

  • Julian Morrison

    I suggest for behavioral modernity: brain plasticity and neophilia as a neotenic trait, resulting in copying behavior in adults. That’s what sets apart on the one hand lower and middle paleolithic Hom Sap and close cousins such as Neanderthals, who pass on a barely changed culture for millennia, and on the other, upper paleolithic Hom Sap who quickly innovate in culture and tools. I think language is oversold. Do you tell someone how to bang out a flint ax? No, you show them. But can you show an adult, or only a child?

  • bysl

    Presuming that there is a single attribute with sufficient explanatory power to justify and characterize the (ostensibly) three transitions (and four growth phases) implies that it was, in fact, a deterministic system. Could it be that the transitions are the result of (the new trendy term, and its explanatory power is still being explored, I suppose) “black swan” effects? This was perhaps unintentionally touched on by hegimonicon and nazgulnarsil–i.e. that black swan events which provide massive shifts in the effective cost of a particular resource are what drove each transition.

  • Will Pearson

    Good point gwern. I’m wondering whether the competition between the nation states of europe was an important ingredient about why the IR happened there.

    How many competitors did china have? I’m thinking that the push from the rulers for better military and naval technology could have kick started the IR by creating specialists and improving ships and metal working techniques on a large scale.

    So that might be the catalyst…

  • snuffbox

    Go read ‘Man the Hunted’ by Sussman and Hart, a primatologist and paleontologist. They discuss early human adaptation as the byproduct of a past where we were hunted without mercy during the night by apex-predators (to which we eventually adapted through use of weapons, language, and team work), while during the day we were scavengers. The evidence provided in the book makes it out that humanity was a prey species for far, far longer than it was a hunter-gatherer and eventual apex-predator species (in fact the authors argue primarily against the “humans as hunter-gatherer” as only a very small aspect for humanity’s lineage, and thus not as influential). The authors don’t extrapolate too far onto the psychological effects of this, but they do point out some areas where it could have influenced our psychology given the long term effects of being hunted day-in, day-out.

  • http://liberalvichy.blogspot.com/ Vichy

    “You’re forgetting something — our planet has ready-made sources of chemical energy. It’s hard to imagine how a civilization could get off the ground without wood, coal, natural gas, petroleum, &c. It wouldn’t be possible to invent other forms of energy production without using them first. We got lucky.”
    Actually, since we’re based on oxygen combustion the fact that there was readily accessible chemical energy would fall more under the anthropic principle.
    Even further, though, it’s very hard to imagine a complex system replicative like DNA developing under the conditions of any system of really high energy (fusion, for example). This may mean that all life probably has its origins in environments of relatively abundant chemical energy. Which shouldn’t be controversial – not stars, and not ice worlds.

  • http://timtyler.org/ Tim Tyler

    Chemical energy and the origin of life? See: http://originoflife.net/cairns_smith/

    That hypothesis uses energy from super-saturated solutions – not really “chemical energy” as the term is usually understood.

  • Brian Gerard

    You start with, “How did humanity become so influential and powerful?” Then proceed with an interesting example of confirmation bias. What even prompts the question?

  • http://homepage.mac.com/bobembry/iblog/index.html Bob Embry

    For Peter Drucker’s view: See Introduction: The Transformation and chapter 1 (From Capitalism to Knowledge Society) of Post-Capitalist Society (http://is.gd/B1Bt). Please be sure to view the entire page.

  • nick

    gwern is on the money in saying that (a) explaining the IR is hard, and (b)the explanation has to include something that China didn’t have much sooner.

    Indeed, the most important thing in this area is to be aware of enough of those kinds of facts and common sense that you can eliminate theories that should obviously be wrong. For example, be aware that hunter-gatherers were experts on botany and animal behavior. It’s not plausible that the simple ideas that seeds can grow into plants that you can eat later, or that you can keep an animal tied or penned up and eat it later, were not discovered and known countless times during the c. 100,000 years between when our brains became modern-sized and agriculture developed. There has to have been some major barrier to benefitting from such obvious ideas to have kept agriculture from developing far sooner. I also don’t find genetics plausible as a cause of agriculture, since agriculture ended up spreading to a very large number of human groups that had become genetically isolated long before the dawn of agriculture. (Genetic evolution cause _by_ agriculture is another story — Cochran and Harpending have some ideas very much worth thinking about). Also not plausible are climate explanations — there were many local climates hospitable to agriculture throughout those 100,000 years — just not necessarily at Mediterranean or higher lattitudes.

    That said, going back to the IR there a number of likely-to-firm differences between China and Western Europe (or Great Britain in particular):

    (1) Differences in political and legal culture. What differences, specifically, it’s hard to say, because there is very little about, for example, Sung or Ming dynasty commercial law that has been translated into English: far too little to compare to English law in the 18th century, for example. We know some very general things, such as that Western Europe was (and still is) a far more legalistic culture than China. Also, we know that Western Europe (contrary to Clark’s claim) radically changed its property law between the 16th and 19th centuries, from a fuedal model of of hierarchy of tenures and bundled political property rights to a model based on old Roman law with flattened and purely economic ownership. There ensued movements such as the enclosure movement in England and an accompanying large increase in capital investments in land. But we don’t know when or to what extent similar incentives to capital investment might have been present or missing in China.

    (2) China never controlled the world’s oceans and merchant marine, but the British just prior and during its IR did. If this explains the IR, then to explain our explanation (i.e. why did Brtain come to control the world’s ocean-going trade) we have to step back and solve the even more puzzling question of how a tiny country of fishing-folk, Portugal, and not an advanced superpower like China, was the first country to take over most of the world’s oceanic trade routes (later to be beaten back by other Western European countries and eventually Great Britain).

    (3) China had the printing press, but in contrast to Western Europe it did not lead to a rapid growth in literacy sustained over several centuries — perhaps because of bureaucratic central control rather than the free-enterprise printing businesses that sprung up all over Western Europe, perhaps because the much greater number of symbols did not as efficiently lend itself to printing, or a combination of these two factors.

    Other interesting related phenomenon to explain, (and it would be nice per Occam’s Razor if it was the same general explanation, but social life is rarely that simple) is why Japan industrialized well in advance of China and Britain was a fuew decades ahead of the rest of Western Europe during most of the 18th and the first half of the 19th century.

    Robin: “If you wanted to attribute the industrial revolution to writing, you’d have to explain why there was a strong threshold effect, so that pre-1800 writing levels had weak growth rate effects, while post-1800 writing levels had strong effects.”

    Besides strong threshold effects, there could be delay effects: for example, the the rapid growth of books and literacy after the mid-15th century in Western Europe gave rise to a slow but accelerating series of innovations (most obviously scientific and technological advances, but perhaps also innovations in business or law), which in turn gave rise to the IR (and happened in England rather than other parts of Western Europe for orthogonal reasons).

  • http://asymptosis.com Steve Roth

    It seems likely to me that recent genetic evolution is a–perhaps the–key factor in the growth of human influence and power. (Nick is quite right to point to Cochran and Harpending, if only glancingly.) But it’s a factor that we don’t yet know enough about to draw firm conclusions from.

    We can say with a great deal of confidence that the emergence and spread of lactose tolerance was a strong contributor to the rise of humans. But the temperamental and behavioral changes are much harder to tease out.

    Did Hamlet’s (decidedly Elizabethan/early modern) character vary so greatly from his father’s (decidedly 10th-century, Viking-like) character for genetic reasons? Is that genetic change on display there?

  • http://profile.typepad.com/robinhanson Robin Hanson

    bill, population and tech encouraging each other has been constant all along, so this can’t explain sudden spurts.

    Tim, some hunter gatherers lived in large dense communities. Printing showed up long before the industrial revolution.

    Lord, if the energy was always there, that doesn’t explain why particular things happened at particular times.

    gwern, yes the growth groove game is hard.

    Juilian, unless you think brain plasticity showed up about 10KBC, I don’t see how it explains the timing.

    bysl, black swans are not mystical causes beyond science; once you see them you can usually understand them – the hard part is to foresee them.

    snuff, I don’t see the prey to predator transition explaining the timing, unless you think it happened over a million years ago.

    Brian, are you saying we are not influential and powerful?

    nick, do you have specific delay effects in mind, or are you just guessing there might be some, since the effects you focus on appeared centuries before the industrial revolution?

    Steve, are you postulating specific genetic innovations at the key 10KBC and 1800 dates?

  • http://asymptosis.com Steve Roth

    Robin: “Steve, are you postulating specific genetic innovations at the key 10KBC and 1800 dates?”

    More accurately: the rapid spread of specific genetic innovations.

    With that caveat: In the centuries leading up to those lift-off dates, yes–with a concurrent/resultant exponential leap.

    As an example: Cochran and Harpending posit strong selection for intelligence among a particular genetically and professionally isolated European group during the late middle ages/early renaissance. Since I am one-half Ashkenazi Jew and hence am likely to be biased, I hesitate to give any endorsement for this view.

  • nick

    Robin, like everybody else I’m just making hopefully informed guesses, but Clark gives a good graph of the rise in literacy in England in the 16th-19th centuries. It’s a fairly steady rise. During this period manufacturing productivity was increasing at about the same rate as it was during the IR. The exponential growth in manufacturing productivity in Western Europe dates to at least 16th century and probably earlier, starting from the very low level of the depths of the Dark Ages in the 9th century. The increase in literacy had been steady since the introduction of paper in Europe and got new energy and reached much higher levels because of the spread of printed books.

    So part of my explanation (based on Clarks’ data) is that the IR was much less of a “spurt” than commonly believed — it was mainly just a long-standing exponential trend becoming the largest percentage of the economy. The rate of growth in that productivity, and in agricultural productivity that allowed manufacturing to come to dominate the economy, was higher than China due to a faster growth of literacy and growth of that literacy to a much higher percent of the population — of which literacy the rise of science, the engineering profession, some of the legal and political changes, etc. were effects.

    It’s as if electronics became the dominant sector of our economy such that economic growth was dominated by Moore’s Law, because we became satiated with our service sector (analogous to the fact that we only need so much food, so the agricultural sector was able to drop as a percent of the economy as Great Britain started to violate Malthusian limits). I don’t expect that to happen for a variety of reasons, but if it did, and if it were fully monetized (i.e. inernalized into the measurable economy), we’d see our GDP doubling every two years. At some point it would look like an economic revolution is happening as Moore’s law came to dominate the economy, but the actual reason would be just a long-standing trend not a revolution in the specific decade when electronics came to dominate the economy. (I’ve just been reading your 1998 paper on exponential trends. Ah, the Internet Bubble, those were heady days. 🙂

  • gwern

    Will Pearson wrote:
    “How many competitors did china have? I’m thinking that the push from the rulers for better military and naval technology could have kick started the IR by creating specialists and improving ships and metal working techniques on a large scale.”

    nick szabo wrote:
    “(2) China never controlled the world’s oceans and merchant marine, but the British just prior and during its IR did. If this explains the IR, then to explain our explanation (i.e. why did Brtain come to control the world’s ocean-going trade) we have to step back and solve the even more puzzling question of how a tiny country of fishing-folk, Portugal, and not an advanced superpower like China, was the first country to take over most of the world’s oceanic trade routes (later to be beaten back by other Western European countries and eventually Great Britain).”

    One of the most important episodes for people interested in the Industrial Revolution & China are the famous voyages of Zheng He; they demonstrate that China had seafaring ability on the order of Portugal or Britain, and long before them. The executive summary for those not already familiar with Zheng He: he lead expeditions of dozens/hundreds of truly enormous junks all over East Asia and the Indian Ocean, trading and fighting, in the early 1400s; the expeditions were ended by imperial fiat.

    In particular, it’s worth noting that the Chinese had already developed the compass and techniques like water-tight compartments. This was in the earlier Song dynasty; the Songs were fighting the incursing Mongols, and their navy was one of their key advantages, so they sponsored and generally supported naval innovation.

    Given this, ‘lack of competition’ is a viable explanation for why naval expeditions & technology stagnated or were abandoned in the later Ming.

  • Brian Gerard

    Yes, Robin, I am saying that we are not influential and powerful. We can observe that there are many more of us than several thousand years ago and that we have made a lot of things. Past that we are confined by our own point of view. Influence and power are normative and your question presumes human norms for a world that is much more than that.

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  • http://brokensymmetry.typepad.com Michael F. Martin

    It’s the mechanisms for coordinating dispersed activities to new spatial and temporal scales that put limits on exponential growth. Occasionally, new ones get introduced and new scales become feasible.

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