Saturday


Knowledge relevant to the Fermi paradox will expand if human knowledge continues to expand, and we can expect human knowledge to continue to expand for as long as civilization in its contemporary form endures. Thus the development of scientific knowledge, once the threshold of modern scientific method is attained (which, in terrestrial history, was the scientific revolution), is a function of “L” in the Drake equation, i.e., a function of the longevity of civilization. It is possible that there could be a qualitative change in the nature of civilization that would mean the continuation the civilization but without the continuing expansion of scientific knowledge. However, if we take “L” in the big picture, a civilization may undergo qualitative changes throughout its history, some of which would be favorable to the expansion of scientific knowledge, and some of which would be unfavorable to the same. Under these conditions, scientific knowledge will tend to increase over the long term up to the limit of possible scientific knowledge (if there is such a limit).

At least part of the paradox of the the Fermi paradox is due to our limited knowledge of the universe of which we are a part. With the expansion of our scientific knowledge the “solution” to the Fermi paradox may be slowly revealed to us (which could include the “no paradox” solution to the paradox, i.e., the idea that the Fermi paradox isn’t really paradoxical at all if we properly understand it, which is an understanding that may dawn on us gradually), or it may hit us all at once if we have a major breakthrough that touches upon the Fermi paradox. For example, a robust SETI signal confirmed to emanate from an extraterrestrial source might open up the floodgates of scientific knowledge through interstellar idea diffusion from a more advanced civilization. This isn’t a likely scenario, but it is a scenario in which we not only confirm that we are not alone in the universe, but also in which we learn enough to formulate a scientific explanation of our place in the universe.

The growth of scientific knowledge could push our understanding of the Fermi paradox in several different directions, which again points to our relative paucity of knowledge of our place in the universe. In what follows I want to construct one possible direction of the growth of scientific knowledge and how it might inform our ongoing understanding of the Fermi paradox and its future formulations.

At the present stage of the acquisition of scientific knowledge and the methodological development of science (which includes the development of technologies that expand the scope of scientific research), we are aware of ourselves as the only known instance of life, of consciousness, of intelligence, of technology, and of civilization in the observable universe. These emergent complexities may be represented elsewhere in the universe, but we do not have any empirical evidence of these emergent complexities beyond Earth.

Suppose, then, that scientific knowledge expands along with human civilization. Suppose we arrive at the geologically complex moons of Jupiter and Saturn, whether in the form of human explorers or in the form of automated spacecraft, and despite sampling several subsurface oceans and finding them relatively clement toward life, they are all nevertheless sterile. And suppose that we extensively research Mars and find no subsurface, deep-dwelling microorganisms on the Red Planet. Suppose we search our entire solar system high and low and there is no trace of life anywhere except on Earth. The solar system, in this scenario, is utterly sterile except for Earth and the microbes that may float into space from the upper atmosphere.

Further suppose that, even after we discover a thoroughly sterile solar system, all of the growth of scientific knowledge either confirms or is consistent with the present body of scientific knowledge. That is to say, we add to our scientific knowledge throughout the process of exploring the solar system, but we don’t discover anything that overturns our scientific knowledge in a major way. There may be “revolutionary” expansions of knowledge, but no revolutionary paradigm shifts that force us to rethink science from the ground up.

At this stage, what are we to think? The science that brought to to see the potential problem represented by the Fermi paradox is confirmed, meaning that our understanding of biology, the origins of life, and the development of planets in our solar system is refined but not changed, but we don’t find any other life even in environments in which we would expect to find life, as in clement subsurface oceans. I think this would sharpen the feeling of the paradoxicalness of the Fermi paradox still without shedding much light on an improved formulation of the problem that would seem less paradoxical, but it wouldn’t sharpen the paradox to a degree that would force a paradigm shift and a reassessment of our place in the universe, i.e., it wouldn’t force us to rethink the astrobiology of the human condition.

Let us take this a step further. Suppose our technology improves to the point that we can visit a number of nearby planetary systems, again, whether by human exploration or by automated spacecraft. Supposed we visit a dozen nearby stars in our galactic neighborhood and we find a few planets that would be perfect candidates for living worlds with a biosphere — in the habitable zone of their star, geologically complex with active plate tectonics, liquid surface water, appropriate levels of stellar insolation without deadly levels of radiation or sterilizing flares, etc. — and these worlds are utterly sterile, without even so much as a microbe to be found. No sign of life. And no sign of life in any other nooks and crannies of these other planetary systems, which will no doubt also have subsurface oceans beyond the frost line, and other planets that might give rise to other forms of life.

At this stage in the expansion of our scientific knowledge, we would probably begin to think that the Fermi paradox was to be resolved by the rarity of the origins of life. In other words, the origins of life is the great filter. We know that there is a lot of organic chemistry in the universe, but what doesn’t take place very often is the integration of organic molecules into self-replicating macro-molecules. This would be a reasonable conclusion, and might prove to be an additional spur to studying the origins of life on Earth. Again, our deep dive both into other planets and into the life sciences, confirms what we know about science and finds no other life (in the present thought experiment).

While there would be a certain satisfaction in narrowing the focus of the Fermi paradox to the origins of life, if the growth of scientific knowledge continues to confirm the basic outlines of what we know about the life sciences, it would still be a bit paradoxical that the life sciences understood in a completely naturalistic manner would render the transition from organic molecules to self-replicating macro-molecules so rare. In addition to prompting a deep dive into origins of life research, there would probably also be a lot of number-crunching in order to attempt to nail down the probability of an origins of life event taking place given all the right elements are available (and in this thought experiment we are stipulating that all the right elements and all the right conditions are in place).

Suppose, now, that human civilization becomes a spacefaring supercivilization, in possession of technologies so advanced that we are more-or-less empowered to explore the universe at will. In our continued exploration of the universe and the continued growth of scientific knowledge, the same scenario as previously described continues to obtain: our scientific knowledge is refined and improved but not greatly upset, but we find that the universe is utterly and completely sterile except for ourselves and other life derived from the terrestrial biosphere. This would be “proof” of a definitive kind that terrestrial life is unique in the universe, but would this finding resolve the Fermi paradox? Wouldn’t it be a lot like cutting the Gordian knot to assert that the Fermi paradox was resolved because only a single origins of life event occurred in the universe? Wouldn’t we want to know why the origins of life was such a hurdle? We would, and I suspect that origins of life research would be pervasively informed by a desire to understand the rarity of the event.

Suppose that we ran the numbers on the kind of supercomputers that a supercivilization would have available to it, and we found that, even though our application of probability to the life sciences indicated the origins of life events should, strictly speaking, be very rare, they shouldn’t be so rare that there was only a single, unique origins of life event in the history of the universe. Say, given the age and the extent of the universe, which is very old and vast beyond human comprehension, life should have originated, say, a half dozen times. However, at this point we are a spacefaring supercivilization, we can can empirically confirm that there is no other life in the universe. We would not have missed another half dozen instances of life, and yet our science points to this. However, a half dozen compared to no other instances of life isn’t yet even an order of magnitude difference, so it doesn’t bother us much.

We can ratchet up this scenario as we have ratcheted up the previous scenarios: probability and biology might converge upon a likelihood of a dozen instances of other origins of life events, or a hundred such instances, and so on, until the orders of magnitude pile up and we have a paradox on our hands again, despite having exhaustive empirical evidence of the universe and its sterility.

At what point in the escalation of this scenario do we begin to question ourselves and our scientific understanding in a more radical way? At what point does the strangeness of the universe begin to point beyond itself, and we begin to consider non-naturalistic solutions to the Fermi paradox, when, by some ways of understanding the paradox, it has been fully resolved, and should be regarded as such by any reasonable person? At what point should a rational person consider as a possibility that a universe empty of life except for ourselves might be the result of supernatural creation? At what point would we seriously consider the naturalistic equivalent of supernatural creation, say, in a scenario such as the simulation hypothesis? It might make more sense to suppose that we are an experiment in cosmic isolation conducted by some greater intelligence, than to suppose that the universe entire is sterile except for ourselves.

I should be clear that I am not advocating a non-naturalistic solution to the Fermi paradox. However, I find it an interesting philosophical question that there might come a point at which the resolution of a paradox requires that we look beyond naturalistic explanations, and perhaps we may have to, in extremis, reconsider the boundary between the naturalistic and the non-naturalistic. I have been thinking about this problem a lot lately, and it seems to me that the farther we depart from the ordinary business of life, when we attempt to think about scales of space and time inaccessible to human experience (whether the very large or the very small), the line between the naturalistic and the non-naturalistic becomes blurred, and perhaps it ultimately ceases to be meaningful. In order to solve the problem of the universe and our place within the universe (if it is a problem), we may have to consider a solution set that is larger than that dictated by the naturalism of science on a human scale. This is not a call for supernaturalistic explanations for scientific problems, but rather a call to expand the scope of science beyond the bounds with which we are currently comfortable.

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Saturday


Eusocial insect colonies achieve an impressive degree of social differentiation and specialization without the kind of intelligence found among mammals. Some scientists call this collective behavior social intelligence.

Eusocial insect colonies achieve an impressive degree of social differentiation and specialization without the kind of intelligence found among mammals. Some scientists call this collective behavior ‘social intelligence.’

In a couple of blog posts, Is encephalization the great filter? and Of Filters, Great and Small, I argued that encephalization is the great filter — clearly implying that this is a single filter that is more significant than another filters, and that encephalization is the great filter. The “great filter” is an idea due to Robin Hanson, according to whom, “The Great Silence implies that one or more of these steps [to visible colonization] are very improbable; there is a ‘Great Filter’ along the path between simple dead stuff and explosive life. The vast vast majority of stuff that starts along this path never makes it. In fact, so far nothing among the billion trillion stars in our whole past universe has made it all the way along this path.”

In the second of the two blog posts noted above, Of Filters, Great and Small, I considered the different possible structures that filters might take, and this is a more nuanced view of the great filter that departs from the idea that a single element of the great filter is uniquely responsible for the great silence and the Fermi paradox. The journey to higher forms of emergent complexity seems to be robust, and therefore likely to have been repeated elsewhere, but it is also a long journey of later emergent complexities multiply supervening upon earlier emergent complexities. This structure of emergent complexities over time is itself a structure more complex than any one of the emergent complexities taken in isolation. In so far as we understand the great filter in this content, we understand a more nuanced view than the idea of one step among many steps along this journey being the unique hurdle to the aggressive expansion of life in the universe, and therefore its visible traces discoverable through cosmology.

Even given this more nuanced view of the great filter, later forms of emergent complexity will be less common than earlier forms, and within the structure of the great filter we can identify particular emergent complexities where the iterated structure falters. If we place this stalling point at exponential encephalization, we might find a universe filled with complex life, but with few or no other intelligent species capable of building a civilization. This is the sense in which I wish my claim that encephalization is the great filter to be understood.

Recently I have had reason to revisit the idea that encephalization is the great filter, and this is primarily due to having read The Social Conquest of Earth by E. O. Wilson, which emphasizes the role of eusociality in the construction of complex societies. I think that Wilson is right about this. Wilson notes that eusociality has emerged on Earth only a handful of times, making it a rare form of emergent complexity: “Eusociality arose in ants once, three times independently in wasps, and at least four times — probably more, but it is hard to tell — in bees.” (p. 136) We can compare this rarity of eusociality as an adaptation to the rarity of intelligence as an adaptation.

The insects that have achieved robust eusociality — perhaps I should say arthropods — are very different from mammals. We must go back more than 500 million years to the split between protostomes and dueterostomes to find the last common ancestor of the two. With the arthropods we share being bilaterally symmetrical, but the split between us — hence the split between our brains and central nervous systems (CNS) — is about as old as the split between mammals and molluscs: chordata, mollusca, and arthropoda are distinct phyla. On the one hand, we know from a recent fossil find something about the CNS of the earliest chordates, which we thus have in common with most other terrestrial animalia (cf. How early a mind?); on the other hand, we also know that neural structures have evolved independently on Earth (cf. The ctenophore genome and the evolutionary origins of neural systems), so that we might speak of neurodiversity among terrestrial animalia. Different brains, when sufficiently complex, are substrates for different forms of emergent consciousness, i.e., different forms of mind.

It is not only dramatically different kinds of minds that might give rise to dramatically different forms of encephalization, and thus intelligence and civilization. Part of the differentness of eusocial insects is their reproductive specialization, which goes along with a genetic structure of a colony in which the superorganism of the colony benefits overall from a majority of individuals not reproducing. This is also dramatically different from human societies. It has been objected to Wilson’s thesis of the eusociality of human beings that human beings are not eusocial, but rather prosocial, and that human cooperative societies cannot be compared to insect cooperative societies because there is no parallel to reproductive specialization among human beings. This, I think, is an unnecessarily narrow conception of eusociality. All we have to do is to recognize that eusociality can take multiple forms (as minds and intelligence can take multiple forms, supervening upon multiple distinct neural structures), some of which involve reproductive specialization and some of which do not, in order for us to recognize human cooperative societies as eusocial.

The most developed brain of the molluscs is that of the octopus, a solitary hunter. Octopi have been hunting in the depths of the sea for hundreds of millions of years, and, apparently, they have never experienced competition on the basis of intelligence, and, perhaps because of this, have never experienced an encephalization event. (Recently in How early a mind? I quoted E. O. Wilson to the effect that, “A Homo sapiens level of intelligence can arise only on land, whether here on Earth or on any other conceivable planet.” ) So octopi have a respectable level of intelligence, but are far from being eusocial. The eusocial insects have a much less powerful brain than octopi or mammals, but they did make the breakthrough to eusociality. Only human beings made the breakthrough to both eusociality and high individual intelligence.

Since reading Wilson on the eusociality of human societies, I can come to think that human civilization is what happens when eusociality coincides with intelligence. Termite mounds and bee hives are what happens when eusociality coincides with insect-level intelligence. And this observation of the interaction of eusociality and intelligence immediately suggests two possible counterfactuals to human civilzation, which I will sketch below. Understand that, in this context, when I use the term “human civilization” I am using this is in its most generic signification, covering all the many different human civilizations that have existed, i.e., the class of all human civilizations (which is the class of all known civilizations constructed by a biological being both eusocial and intelligent).

I noted above that we can employ a conception of eusociality less narrow than that restricted to eusocial insects with reproductive specialization. Similarly, the other element in civilization — intelligence — ought also to be construed broadly. Many different kinds of intelligence interacting with many different kinds of eusociality suggest many different possibilities for civilization distinct from the class of human civilizations. At the present time I am not going to consider kinds of eusociality and intelligence as much as degrees of eusociality and intelligence, and I will assume that the insect transition to reproductive specialization represents eusociality taken to a higher degree than eusociality has progressed in human beings. Similarly, I will assume that human intelligence represents a higher degree of intelligence than now-extinct branches of the genus homo, i.e., our ancestors with lower degrees of encephalization and lower intelligence.

From these assumptions about degrees of eusociality and intelligence, two counterfactual classes of civilization are suggested:

High Eusociality/Low Intelligence

A species might be less intelligent than human beings (i.e., possess a lower degree of encephalization) but more eusocial than human beings, and be able to build a civilization.

Low Eusociality/High Intelligence

A species might be more intelligent than human beings (i.e., possessing a higher degree of encephalization, or a thicker neocortex) but less eusocial than human beings, and be able to build a civilization.

This formulation has the virtue of existing human civilization embodying the principle of mediocrity: our eusociality and intelligence are balanced; we are not as eusocial or as individualistic as we might have been, and we are not as intelligence or as unintelligent as we might have been. We are in the “Goldilocks zone” of coinciding eusociality and intelligence, and this human “sweet spot” for civilization may account for the fact that civilization emerged independently in widely separated geographical regions, not as a result of idea diffusion, but rather as a consequence of independent invention.

In the High Eusociality/Low Intelligence class of civilizations, we would see somewhat individually intelligent beings capable of a high degree of cooperation through eusociality forming socieites (superorganisms) quite early in their history. We can see the degree to which bees and ants and termites can develop societies based on eusociality and an almost negligible individual intelligence; with a degree of eusociality approaching this, but in a species endowed with more cognitive capacity, cities might be built that look like something between a human city and a termite mound, and this might happen spontaneously. If this had happened with an earlier human ancestor — a counterfactual ancestor with greater eusociality than any actual human ancestor — it could have preempted the emergence of human civilization by occurring millions of years earlier.

In the Low Eusociality/High Intelligence class of civilizations, civilization may have come about at the level of scattered bands of hunter-gatherers, or, at least, human beings in small groups may have been able to develop science and technology without large social institutions such as governments, universities, and corporations, which discipline unruly human beings and make it possible for them to work cooperatively together. One can imagine that a more intelligent (counterfactual) species of the genus homo might have been sufficiently intelligent to pursue science at a much earlier period of its history, and one can imagine members of such a species coming together for scientific purposes much as our ancestors came together at Göbekli Tepe (which I first wrote about in The Birth of Agriculture from the Spirit of Religion) possibly for religious rituals, even before they gathered in settlements for agriculture.

Both counterfactual scenarios I have described above could have resulted in civilization on Earth emerging tens of thousands or hundreds of thousands of years earlier than it did in fact emerge. I suppose it would be equally possible to formulate counterfactuals in which different classes of civilization emerged much later.

Each of the three classes of civilizations considered here — moderate eusociality/moderate intelligence, high eusociality/low intelligence, and low eusociality/high intelligence — have distinct advantages and disadvantages, in terms of the viability of the civilization that results. However, cognitive capability begins to play a much greater role in civilization after industrialization when civilization becomes technological and scientific. If a given civilization can survive to make the breakthrough to science-driven technology, all other things being equal, the species with the greatest intelligence will have the greatest advantage in deploying science to further the ends of that species. I suspect that a high eusociality/low intelligence civilization would be stagnant, and possibly so stagnant that the breakthrough to industrialization never occurs. I also suspect that human beings were just smart enough to make that breakthrough, as indicated by the single point of origin of the industrial revolution. Short of that threshold, any civilization remains cosmologically invisible, exclusively bound to its homeworld, and incapable of long-term existential risk mitigation. This scenario is consistent with the great silence, and may constitute another approach to the Fermi paradox.

The research questions that follow from these considerations include: Are there intrinsic limits to eusociality among beings whose biology is not consistent with reproductive specialization? Are there intrinsic limits to intelligence for biological beings of known biochemistry? How do eusociality and intelligence interact biologically and ecologically? Does either constitute a check upon the other?

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Cooperation among human beings has its limits -- as illustrated by the story of the Tower of Babel -- and one limit to cooperation is our level of eusociality.  With a higher or lower level of eusociality, civilization would have had a different structure.

Cooperation among human beings has its limits — as illustrated by the story of the Tower of Babel — and one limit to cooperation is our level of eusociality. With a higher or lower level of eusociality, civilization would have had a different structure.

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Wednesday


filter layers

In my recent post Is encephalization the Great Filter? I quoted Robin Hansen’s paper that gave the original formulation of the Great Filter. Again, Hanson wrote:

“Consider our best-guess evolutionary path to an explosion which leads to visible colonization of most of the visible universe… The Great Silence implies that one or more of these steps are very improbable; there is a ‘Great Filter’ along the path between simple dead stuff and explosive life. The vast vast majority of stuff that starts along this path never makes it. In fact, so far nothing among the billion trillion stars in our whole past universe has made it all the way along this path. (There may of course be such explosions outside our past light cone [Wesson 90].)”

Robin Hanson, The Great Filter — Are We Almost Past It? 15 Sept. 1998

In filtration technology, the “steps” between the input and the output of a filter are called “elements,” “layers,” or “media.” I will here speak of “elements” of the Great Filter, and I will here take seriously the idea that, “…one or more of these [elements] are very improbable.” In other words, the Great Filter may be one or many, and we do not yet know which one of these alternatives is the case. Most formulations of the Great Filter reduce it to a single factor, but I want to here explicitly consider the Great Filter as many.

What is the Great Filter filtering? Presumably, the higher forms of complexity that are represented by the successive terms of the Drake equation, and which Big History recognizes (according to a slightly different schema) as levels of emergent complexity. The highest forms of complexity of which we are aware seem to be very rare in the universe, whereas the relatively low level of complexity — like hydrogen atoms — seems to be very common in the universe. Somewhere between plentiful hydrogen atoms and scarce civilizations the Great Filter interposes. And there may yet be forms of complexity not yet emergent, and therefore a filter through which we have not yet passed.

Hanson mentions visible colonization of the visible universe — this is a different and a much stronger standard to overcome than that of mere intelligence or civilization. Our own civilization does not constitute visible colonization of the universe, in so far as visible colonization means the consequences of intelligent colonization of the universe are obvious in the visible spectrum, but there is a sense in which we are highly visible in the EM spectrum. Thus the scope of the “visibility” of a civilization can be construed narrowly or broadly.

Construed broadly, the “visible” colonization of the universe would mean that the effects of colonization of the universe would be somewhere obvious along some portion of the EM spectrum. We can imagine several such scenarios. It might have been that, as soon as human beings put up the first radio telescope, we would have immediately detected a universe crowded with intelligent radio signals. We might have rapidly come to a science of analyzing the classifying the variety of signals and signatures of exocivilizations in the way that we now routinely classify kinds of stars and galaxies and now, increasingly, exoplanets. Or it might have been that, as soon as we thought to look for the infrared signatures of Dyson civilizations, we would have found many of these signatures. Neither of these things did, in fact, happen, but we can entertain them as counterfactuals and we easily visualize how either could have been the case.

The difference between a universe that is visibly colonized and one that is not is like the difference between coming over the ridge of hill and seeing a vast forest spread out below — i.e., a natural landscape that came about without the intervention of intelligence — and coming over the ridge of a hill and seeing an equally vast landscape of a city spread out below, with roads and building and lights and so on — i.e., an obvious built environment that did not come about naturally — out of reach from a distance, but no less obvious for being out of reach. At present, when we look out into the cosmos we see the cosmological equivalent of the forest primeval — call it the cosmos primeval, if you will (with a nod to Longfellow’s Evangeline).

In the illustration below the Great Filter is everything that stands between an empty universe and a universe filled with visible colonization by intelligent agents and their civilization. The Great Filter is then broken down into seven (7) diminutive filters, each a filter “element” of the Great Filter, which correspond to the terms of the Drake Equation. We could choose other elements for the Great Filter than the terms of the Drake equation, but this is a familiar and accessible formalism so I will employ it without insisting that it is exhaustive or even the best breakdown of the elements of the Great Filter. The reader is free to substitute any other appropriate formalism as an expression of the Great Filter, with any number of elements.

drake equation 1

In this illustration the lower case letters along the left margin that correspond to arrows each stopped by an element of the Great Filter are to be understood as follows:

a – failure of stars to form

b – failure of planets to form

c – failure of planets to be consistent with the emergence of a biosphere

d – failure of planets consistent with the emergence of a biosphere to produce a biosphere

e – failure of a biosphere to produce intelligent life and civilization

f – failure of a civilization to produce technically detectable signatures

g – failure of a technologically detectable civilization to survive a period of time sufficient to communicate

h – a civilization on a trajectory toward visible colonization of the universe

Given a Great Filter constructed from a series of lesser filters, relations between the elements of the Great Filter (the individual lesser filters) describe possible permutations in the overall structure of the Great Filter, as I have attempted to illustrate in the image below.

great filter elements

In this illustration the pathways marked by arrows are to be understood as curves, the X axis of which is the difficulty of passing through an element of the Great Filter, and the Y axis of which marks the gradual emergence of complexity strung out in time, as follows:

A – An inverse logarithmic Great Filter in which successive elements of the filter are easier to pass through by an order of magnitude with each element

B – An inverse linear gradient Great Filter in which successive elements of the filter are easier to pass through by degrees defined by the gradient

C – A constant Great Filter in which each element is equally easy, or equally difficult, to pass

D – A linear gradient Great Filter in which successive elements of the filter are progressively more difficult to pass through, with the change in the degree of difficulty between any two elements defined by the gradient (call it Δe, for change in difficulty of passage through an element)

E – A logarithmic Great Filter in which successive elements of the filter are each progressively more difficult to pass through by an order of magnitude for each element (my drawings are, or course, inexact, so I appeal to the leniency of the reader to get my general drift).

In the case of a Great Filter of an inverse logarithmic scale, the first filter element is by far the most difficult to pass through, and every subsequent element is an order of magnitude easier to pass. Once given the universe, then, intelligence and civilization are nearly inevitable. While such a filter seems counter-intuitive (most filters begin with coarse filtration elements and proceed in steps to finer filtration elements), something like may be unconsciously in mind in the accounts of the universe as a place teaming not only with life, but with civilizations — what I have elsewhere called an intelligence-rich galactic habitable zone (IRGHZ) — and I note that such visions of an IRGHZ often invoke the idea of inevitability in relation to life and intelligence.

However, this is not the problem that the universe presents to us. We do not find ourselves in the position of having to explain the prolixity of civilization in the universe; rather, we find ourselves in the predicament of having to explain the silentium universi.

The above analysis ought to make it clear that, not only do we not know what the Great Filter is — i.e., we do not know if there is one factor, one element among others, that is the stumbling block to the broadly-based emergence of higher complexity — but also that we do not know the overall structure of the Great Filter. Even if I am right that encephalization could be singled out at the Great Filter (as I postulated in Is encephalization the Great Filter?), and the one especially difficult element of the Great Filter to pass beyond, there are still further filters that could prevent our civilization from developing into the kind of civilization that Hanson describes as visibly colonizing the universe, that is to say, a cosmologically visible civilization.

encephalization filter

We can easily project a universe with a spacefaring civilization so pervasive that the stars in their courses are diverted from any trajectory that would be based on natural forces, that the constellations would have an obviously artificial character, and that use of energy on a cosmological scale leaves unambiguous infrared traces due to waste heat. A universe that was home to such a civilization would have passed beyond a filtration element that we have not yet passed beyond.

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Sunday


Hominid encephalization reveals an exponential growth curve.

Hominid encephalization reveals an exponential growth curve.

The idea of the great filter was formulated by Robin Hanson. In the exposition below Hanson also names a number of steps (acknowledged to be non-exhaustive) in the development of explosively expanding life:

“Consider our best-guess evolutionary path to an explosion which leads to visible colonization of most of the visible universe… The Great Silence implies that one or more of these steps are very improbable; there is a ‘Great Filter’ along the path between simple dead stuff and explosive life. The vast vast majority of stuff that starts along this path never makes it. In fact, so far nothing among the billion trillion stars in our whole past universe has made it all the way along this path. (There may of course be such explosions outside our past light cone [Wesson 90].)”

Robin Hanson, The Great Filter — Are We Almost Past It? 15 Sept. 1998

Discussion of the Great Filter has focused on singling out one factor and identifying this one factor as the Great Filter, although Hanson is explicit that, “one or more of these steps are very improbable.” In the event that several steps in the development of explosively expanding life rather than some one single step is unlikely, the Great Filter may consist of several elements. I think that this is an important qualification to make, but at present I will adopt the conventional presumption that one step in the development of advanced civilization is improbable (or especially improbable) and constitutes the Great Filter.

Graph of the encephalization quotient of several mammals.

Graph of the encephalization quotient of several mammals.

What we know about the cosmos is consistent with it being rich in life, but poor in technologically advanced civilization. The more that we learn about exoplanetary systems (living, as we do, in the Golden Age of exoplanet discovery), the more our scientific understanding of the universe points toward a superfluity of habitable worlds (or, at least, potentially habitable worlds), even while no trace of intelligence has yet been seen or heard beyond Earth. Some of this may have to do with the amount of research funding that is channeled into astronomy and astrophysics in comparison to SETI research, which has received relatively little to date. This is about to change. A “Breakthrough Initiative” will be funneling a large amount of money into SETI — Breakthrough Listen — but there is no reason as yet to suppose that this effort will be any more successful than past efforts, though I would be quite pleased to be proved wrong.

Brain to body mass ratio is distinct from encephalization quotient (EQ).

Brain to body mass ratio is distinct from encephalization quotient (EQ).

The point that I made some time ago in SETI as a Process of Elimination still holds good: as our scientific instrumentation improves with each generation of technology, and our research methods become more sophisticated, we are able to exclude (and, correlatively, to include) an increasing number of possibilities and instances. In other words, progress in science comes about by falsifying certain hypotheses, as would be expected from a philosophy of science derived from the Popper-Lakatos axis. (It is often discussed in relation to SETI research that investigators are hesitant to publish negative results; perhaps if they better understood the crucial role of falsification in the methodology of the scientific research program that is SETI they would be more inspired to publish negative results.)

Comparative brain sizes of several mammals.

Comparative brain sizes of several mammals.

When, in the coming decades, we are able to obtain spectroscopic analyses of exoplanet atmospheres, our knowledge of what is going on on exoplanets — as opposed to merely knowing about their existence, location, size, orbital period, and so on, which is the kind of scientific knowledge we have only recently come into — will improve by an order of magnitude. At this point in time we will move from ne in the Drake equation (number of planets, per solar system, with an environment suitable for life) to fl (fraction of suitable planets on which life actually appears) and possibly also fc (fraction of civilizations that develop a technology that releases detectable signs of their existence into space, from which we can infer fi, fraction of life bearing planets on which intelligent life emerges) if exoplanet atmospheric signatures reveal signs of unambiguous industrial activity.

Frank Drake

We do not know the prevalence of life in our galaxy, much less in the universe at large — i.e., whether or not we live in a biota-rich GHZ, or even CHZ (cosmic habitable zone) — but we may soon be able to estimate the presence of life in the cosmos as we can now estimate the number of planets in the cosmos. It is entirely possible that the universe is teaming with life, even advanced life that is as sophisticated as the life of the terrestrial biosphere. I have written elsewhere that we may live in a “universe of stromatolites” (cf. A Needle in the Cosmic Haystack), but we may also be living in the universe rich in the ecological equivalents of sharks, koalas, and penguins. With one exception: the emergence of the cognitive capacity that makes abstract intelligence possible as well as the civilization that is predicated upon it.

Do we live in a universe of stromatolites?

Do we live in a universe of stromatolites?

In an earlier post, A Note on the Great Filter, I suggested that we are the Great Filter. I would now like to refine this: if I were to identify a “Great Filter” (i.e., a single element constituting the Great Filter) somewhere between plentiful life and absent advanced technological civilizations, I would put my finger on hominid encephalization. It was the rapid encephalization of our hominid ancestors that made what we recognize as intelligence and civilization possible. While there are many other large brains in the animal kingdom — the whale brain and the elephant brain are significantly larger than the human brain — and other mammals have brains as convoluted as the human brain — meaning more of the neocortex, which makes up the outer layer of gray matter — the encephalization quotient of the human brain is significantly greater than any other animal.

neocortex

Brain size in absolute terms may have to exceed a certain threshold before intelligence of the sort we seek to measure can be said to be present. Neurons are of a nearly constant size, so the minimal neuronal structure necessary to control bodily functions take up about the same space in a mouse and an elephant. Factors other than sheer brain size are relevant to brain function, as, for example, the portion of the brain made up by the cerebral cortex and the amount of convolutions (therefore outer surface area, and the cerebral cortex is outer layer). Hence the introduction of encephalization quotient: encephalization quotient is not simply a ratio of brain mass to body mass, but is also based on the expected brain size for a given body plan — this introduces an admitted interpretive element into EQ, but that does not vitiate the measure. When, in the distant future, we can compare EQs over many different species from many different biospheres, we can firm up these numbers. Someday this will be the work of astroneurology.

The 'WOW!' signal -- fugitive signature of intelligence in an otherwise lonely universe? Perhaps astroneurology will someday study neural architecture across biospheres and arrive at a non-anthropocentric measure of intelligence that could account for something like the 'WOW!' signal.

The ‘WOW!’ signal — fugitive signature of intelligence in an otherwise lonely universe? Perhaps astroneurology will someday study neural architecture across biospheres and arrive at a non-anthropocentric measure of intelligence that could account for something like the ‘WOW!’ signal.

The human brain (with its distinctive and even disproportionate EQ) has not changed since anatomical modernity — at least a hundred thousand years, and maybe as much as three hundred thousand years — and human thought has probably not greatly changed since the advent of cognitive modernity, perhaps seventy thousand years ago. We must continually remind ourselves that even the earliest anatomically modern human beings had a brain structurally indistinguishable from the human brain today. With the blindingly rapid gains of technological civilization over the past hundred years it is increasingly difficult to maintain a sense of connection to the past, not to mention the distant past. But when the human brain appeared in its modern form, it was unprecedented in its cognitive capacity — it was and still is an extreme outlier. There was nothing else like it on the planet, and from this brain followed control of fire, language, technology, art, and eventually civilization.

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Tuesday


Copernicus

Today we celebrate the 540th anniversary of the birth of Nicolaus Copernicus. The great astronomer was born 19 February 1473 in Toruń, now part of Poland. The name of Copernicus belongs with the short list of thinkers who not only changed the direction of civilization, but also the nature and character of Western civilization. Copernicus as the distinction of having a cosmology named in his honor.

We would do well to recall how radically our understanding of the world has changed in relatively recent years. Up until the advent of modern science, several ancient traditions of Western civilization had come together in a comfortingly stable picture of the world in which all of Western society was deeply invested. The Aristotelian systematization of Christian theology carried out by Thomas Aquinas was especially influential. Questioning this framework was not welcome. But science was an idea whose time had come, and, as we all know, nothing can stop the progress of an idea whose time had come.

Copernicus began questioning this cosmology by putting the sun in the center of the universe; Galileo pointed his telescope into the heavens and showed that the sun has spots, the moon has mountains, and that Jupiter had moons of its own, the center of its own miniature planetary system. Others took up the mantle and went even farther: Tycho Brahe, Johannes Kepler, and eventually Newton and then Einstein.

Copernicus was a polymath, but essentially a theoretician. One must wonder if Copernicus ever read William of Ockham, since it was Ockham along with Copernicus who initiated the unraveling of the scholastic synthesis, out of which the modern world would rise like a Phoenix from the ashes of the medieval world. Ockham provided the theoretical justification for the sweeping simplification of cosmology that Copernicus effected; it is not outside the realm of possibility that the later theoretician read the work of the earlier.

Today, when our knowledge of cosmology is expanding at breathtaking speed, Copernicus is more relevant than ever. We find ourselves forced to consider and to reconsider the central Copernican idea from every possible angle. The Fermi Paradox and the Great Filter force us to seek new insights into Copernicanism. I quite literally think about Copernicanism every day, making Copernicus a living influence on my thought.

As our civilization grows in sophistication, the question “Are we alone?” becomes more and more pressing. Arthur C. Clarke wrote, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” This insight is profound in its simplicity. Thus we search for peer civilizations and peer life in the universe. That is to say, we look for other civilizations like ours, and for life that resembles us.

SETI must be considered a process of elimination, which I take to already have eliminated “near by” exocivilizations, although we cannot rule out the possibility that we currency find ourselves within the “halo” of a vanished cosmological civilization.

A peer civilization only slightly advanced over our own (say 100-500 years more industrial development), if it is in fact a peer and not incomprehensibly alien, would also be asking themselves “Are we alone?” They, too, would be equally terrified at being alone in the cosmos or at having another peer civilization present. Because we know that we exist as an industrial-technological civilization, and we know the extent to which we can eliminate peer civilizations in the immediate neighborhood of our own star, we can assume that a more advanced peer civilization would have an even more extensive sphere of SETI elimination. They would home in on us as incredibly interesting, as an exception to the rule of the eerie silence, in the same way that we seek out others like ourselves. That is to say, they would have found us, not least because they would be actively seeking us. So this may be considered an alternative formulation of the Fermi paradox.

Despite the growing tally of planets discovered in the habitable zones of stars, including nearby examples at Tau Ceti which lies within our SETI exclusion zone (which excludes only civilizations producing EM spectrum signals), there is no evidence that there are other peer civilizations, and advanced peer civilizations would already have found us — and they would be as excited by discovering us as we would be excited in discovering a peer civilization. There are none close, which we know from the SETI zone of exclusion; we must look further afield. Other peer civilizations would also likely have to look further afield. In looking further afield they would find us.

I don’t believe that any of this contradicts the Copernican principle in spirit. I think it is just a matter of random chance that our civilization happens to be the first industrial-technological civilization to emerge in the Milky Way, and possibly also the first in the local cluster of galaxies. We are, after all, an accidental world. However, it will take considerable refinement of this idea to show exactly how the uniqueness of human civilization (if it is in fact locally unique) is consistent with Copernicanism — and this keeps Copernicus in my thoughts.

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A Note on the Great Filter

29 October 2012

Monday


Are we ourselves, as the sole hominid species, the Great Filter?

Parochialism, ironically, knows no bounds. Our habit of blinkering ourselves — what visionary poet William Blake called “mind-forged manacles” — is nearly universal. Sometimes even the most sophisticated minds miss the simple things that are staring them in the face. Usually, I think this is a function of the absence of a theoretical context that would make it possible to understand the simple truth staring us in the face.

I have elsewhere written that one of the things that makes Marx a truly visionary thinker is that he saw the industrial revolution for what it was — a revolution — even while many who lived through this profound series of events where unaware that they were living through a revolution. So even if one’s theoretical context is almost completely wrong, or seriously flawed, the mere fact of having the more comprehensive perspective bequeathed by a theoretical understanding of contemporary events can be enough to make it possible for one to see the forest for the trees.

Darwin wrote somewhere (I can’t recall where as I write this, but will add the reference later when I run across it) that from his conversations with biologists prior to publishing The Origin of Species he knew how few were willing to thing in terms of the mutability of species, but once he had made his theory public it was rapidly adopted as a research program by biologists, and Darwin suggested that countless facts familiar to biologists but hitherto not systematically incorporated into theory suddenly found a framework in which they could be expressed. Obviously, these are my words rather than Darwin’s, and when I can find the actual quote I will include it here, but I think I have remembered the gist of the passage to which I refer.

It would be comical, if it were not so pathetic, that one of the first responses to Darwin’s systematic exposition of evolution was for people to look around for “transitional” evolutionary forms, and, strange to say, they didn’t find any. This failure to find transitional forms was interpreted as a problem for evolution, and expeditions were mounted in order to search for the so-called “missing link.”

The idea that the present consists entirely of life forms having attained a completed and perfected form, and that all previous natural history culminates in these finished forms of the present, therefore placing all transitional forms in the past, is a relic of teleological and equilibrium thinking. Once we dispense the unnecessary and mistaken idea that the present is the aim of the past and exemplifies a kind of equilibrium in the history of life that can henceforth be iterated to infinity, it becomes immediately obvious that every life form is a transitional form, including ourselves.

A few radical thinkers understood this. Nietzsche, for example, understood this all-too-clearly, and wrote that, “Man is a rope stretched between the beasts and the Superman — a rope over an abyss. A dangerous crossing, a dangerous wayfaring, a dangerous looking-back, a dangerous trembling and halting. What is great in man is that he is a bridge and not a goal..” But assertions as bold as that of Nietzsche were rare. Darwin himself didn’t even mention human evolution in The Origin of Species (though he later came back to human origins in The Descent of Man): Darwin first offered a modest formulation of a radical theory.

So what has all this in regard to Marx and Darwin to do with the great filter, mentioned in the title of this post? I have written many posts about the Fermi paradox recently without ever mentioning the great filter, which is an important part of the way that the Fermi paradox is formulated today. If we ask, if the universe is supposedly teaming with alien life, and possibly also with alien civilizations, why we haven’t met any of them, we have to draw that conclusion that, among all the contingencies that must hold in order for an industrial-technological civilization to arise within our cosmos, at least one of these contingencies has tripped up all previous advanced civilizations, or else they would be here already (and we would probably be their slaves).

The contingency that has prevented any other advanced civilization in the cosmos from beating us to the punch is called the great filter. Many who write on the Fermi paradox, then, ask whether the great filter is in our past or in our future. If it is in our past, we have good reason to hope that our civilization can be an ongoing concern. If it is in our future, we have a very real reason to be concerned, since if no other advanced civilization has made it through the great filter in their development, it would seem unlikely that we would prove the exception to that rule. So a neat way to divide the optimists and the pessimists in regard to the future of human civilization is whether someone places the great filter in the past (optimists) or in the future (pessimists).

I would like to suggest that the great filter is neither in our past or in our future. The great filter is now; we ourselves are the great filter.

Human beings are the only species (on the only biosphere known to us) known to have created industrial-technological civilization. This is our special claim to intelligence. But before us there were numerous precursor species, and many hominid species that have since gone extinct. Many of these hominids (who cannot all be called human “ancestors” since many of them were dead ends on the evolutionary tree) were tool users, and it is for this reason that I noted in Civilization and the Technium that the technium is older than civilization (and more widely distributed than civilization). But now we are only only remaining hominid species on the planet. So in the past, we can already see a filter that has narrowed down the human experience to a single sentient and intelligent species.

Writers on the technological singularity and on the post-human and even post-biological future have speculated on a wide variety of possible scenarios in which post-human beings, industrial-technological civilization, and the technium will expand throughout the cosmos. If these events come to past, the narrowing of the human experience to a single biological species will eventually be followed by a great blossoming of sentient and intelligent agents who may not be precisely human in the narrow sense, but in a wider sense will all be our descendants and our progeny. In this eventuality, the narrow bottleneck of humanity will expand exponentially from its present condition.

Looking at the present human condition from the perspective of multiple predecessor species and multiple future species, we see that the history of sentient and intelligent life on earth has narrowed in the present to a single hominid species. The natural history of intelligence on the Earth has all its eggs in one basket. Our existence as the sole sentient and intelligent species means that we are the great filter.

If we survive ourselves, we will have a right to be optimistic about the future of intelligent life in the universe — but not until then. Not until we have been superseded, not until the human era has ended, ought we to be optimistic.

Man is a narrow strand stretched between pre-human diversity and post-human diversity.

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