The First Planetary Civilization

Saturday

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The famous Virgin of the Navigators by Alejo Fernández, on display in Sevilla, like the Tordesillas meridian is one of the great ideological expressions of the Age of Discovery.

Some time ago I wrote Modernism without Industrialism: Europe 1500-1800, in which I identified the period from approximately 1500 to 1800 in western civilization as a distinctive kind of civilization, which I have in subsequent posts simply called “modernism without industrialism.” For present purposes it doesn’t matter whether this is a distinctive kind of civilization, co-equal with other distinctive kinds of civilization, or whether it is a developmental stage in a larger civilization under which it is subsumed. This is an interesting question in the theory of civilization, but it will not bear upon what I have to say here. Whether we take the period 1500-1800 as a stage in the larger development of western civilization, or as a civilization in its own right, it is a period that can be described in terms of properties that do not apply to other periods.

The first two of what I have elsewhere called the “three revolutions” — the scientific revolution, the political revolutions, and the industrial revolution — transformed this period in novel ways, and the last of these three revolutions terminates the period decisively as a new way of life results from industrialization pre-empting the interesting social experiment of modernism without industrialism. Without the preemption of industrialization, this experiment might have continued, and the world today would be a different place than the world we known — it would be a counterfactual planetary high-level equilibrium trap.

There is another great revolution that occurred in this period, and that is the Age of Discovery, when explorers and merchants and conquerors set out from Europe and circled the planet for the first time since our Paleolithic ancestors settled the planet entire, without knowing what they had done. That the explorers and merchants and conquerors of the Age of Discovery knew what they were doing is evidenced by the maps they made and what they wrote about their experiences. They discovered that humanity is one species on one planet, and they knew that this is what they had discovered, though assimilating that knowledge was another matter; we still struggle with this knowledge today.

The Age of Discovery bounds the beginning of this period as the industrial revolution bounds the ending of this period, and, to a large extent, defines the period, since exploration and discovery is what initiates the human recognition of itself as a whole and the planet as a whole. Europe had been building out a shipping capacity in excess of its internal needs since the late Middle Ages, and it was the exaptation of this shipping infrastructure with its attendant technologies and expertise that made the Age of Discovery possible. Once the proof of concept was provided by Columbus, Magellan, and the other early explorers, initiating the Columbian Exchange, the planet opened to global commerce with astonishing rapidity.

What this global transportation infrastructure meant was that this distinctive period of civilization might be called the First Planetary Civilization, since throughout this period trade and communications take place on a global scale, and this in turn makes global empires possible for the first time. There were, of course, many survivals from the medieval period that characterize this first planetary civilization, but there were also perhaps as many novel features of this civilization as well. This was a civilization in possession of science, though science at a small scale, and not yet exploited for human purposes to the extent that science today is exploited for human purposes. This was a civilization in which merchants and industries had a distinctive place, and the political system was no longer dominated by rural manorial estates and their local feudal lords. Planetary-scale concerns now shaped the policies of increasingly centralized regimes, that would only become more centralized as the period drew to a close in the time of the Sun King. And while political regimes were marked by increasing centralization and the rationalization of institutions, it was also a time of great lawlessness, as the expansion of European civilization into the western hemisphere was also an age of piracy.

Since the industrial revolution we have also had a planetary civilization, but the planetary civilization that began to take form in the wake of the industrial revolution is distinct from the first planetary civilization that characterized the period from 1500 to 1800. The planetary civilization we have been building since the industrial revolution might be called the second planetary civilization, and it has been marked by the spread of popular sovereignty and Enlightenment ideals (and, I would argue, the gradual adoption of the Enlightenment project as the central project of planetary civilization), the mechanization and then the electrification of the global transportation and communications network (further accelerating the rapidity of commerce), the planetary propagation of cultural and social influences, and the rise of commerce and industry to a position rivaling that of nation-states. Merchants no longer merely have a place in civilization, but they often dictate to others the place that they will hold in the social order.

Are these successive first and second planetary civilizations an accident of terrestrial history, that could be and probably are different wherever other civilizations are to be found in the universe (if they are to be found)? Or are these first and second planetary civilizations sufficiently distinctive as kinds of civilization that they ought to be present in any taxonomy of civilizations because they are likely to be exemplified wherever there are worlds with civilizations? One of the ways in which to approach the problem mentioned above, that of whether the First Planetary Civilization of 1500-1800 is a kind of civilization in its own right, or whether it is a developmental stage in a larger formation of civilization, would be to identify as a distinctive kind of civilization any formation of civilization that can be formalized to the point of potential applicability to any civilization anywhere, whether on Earth or elsewhere. In this way, a scientific theory of civilization that is sufficiently comprehensive to address any and all civilizations can shed light on the particular problems of human civilization, even if that was not the motivation for formulating a science of civilization.

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Planetary Endemism and the Overview Effect

Friday

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A Conceptual Overview

What is the relationship between planetary endemism and the overview effect? This is the sort of question that might be given a definitive formulation, once once we have gotten sufficiently clear in our understanding of these ideas and their ramifications. I’m not yet at the point of formulating a definitive expression of this relationship, but I’m getting closer to it, so this post will be about formulating relationships among these and related concepts in a way that is hopefully clear and illuminating, while avoiding the ambiguities inherent in novel concepts.

This post is itself a kind of overview, attempting to show in brief compass how a number of interrelated concepts neatly dovetail and provide us with a rough outline of a conceptual overview for understanding the origins, development, distribution, and destiny of civilization (or some other form of emergent complexity) in the universe.

The Stelliferous Era

The Stelliferous Era is that period of cosmological history after the formation of the first stars and before the last stars burn out and leave a cold and dark universe. In the cosmological periodization formulated by Fred Adams and Greg Laughlin, the Stelliferous Era is preceded by the Primordial Era and followed by the Degenerate Era. During the Primordial Era stars have not yet formed, but matter condenses out of the primordial soup; during the Degenerate Era, the degenerate remains of stars, black holes, and some exotic cosmological objects are to the found, but the era of brightly burning stars is over.

What typifies the Stelliferous Era is its many stars, radiating light and heat, and whose nucleosynthesis and supernova explosions forge heavier forms of matter, and therefore the chemical and minerological complexity from which later generations of (high metallicity) stars and planets will form. (A Brief History of the Stelliferous Era is an older post about the Stelliferous Era that needs to be revised and updated.)

In comparison to the later Degenerate Era, Black Hole Era, and Dark Era of cosmological history, the Stelliferous Era is rather brief, extending from 10⁶ to 10¹⁴ years from the origins of the universe, and almost everything that concerns us can be further reduced to the eleventh cosmological decade (from 10 billion to 100 billion years since the origin of the universe). Since this cosmological periodization is logarithmic, the later periods are even longer in duration than they initially appear to be.

Our interest in the Stelliferous Era, and, more narrowly, our interest in the eleventh decade of the Stelliferous Era, does not rule out interesting cosmological events in other eras of cosmological history, and it is possible that civilizations and other forms of emergent complexity that appear during the Stelliferous Era may be able to make the transition to survive into the Degenerate Era (cf. Addendum on Degenerate Era Civilization), but this brief period of starlight in cosmological history is the Stelliferous Era window in which it is possible for peer planetary systems, peer species, and peer civilization to exist.

Planetary Endemism

Planetary Endemism is the condition of life during the Stelliferous Era as being unique to planetary surfaces and their biospheres. Given the parameters of the Stelliferous Era — a universe with planets, stars, and galaxies, in which both water (cf. The Solar System and Beyond is Awash in Water) and carbon-based organic molecules (cf. Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features by Sun Kwok and Yong Zhang) are common — planetary surfaces are a “sweet spot” for emergent complexities, as it is on planetary surfaces that energy from stellar insolation can drive chemical processes on mineral- and chemical-rich surfaces. The chemical and geological complexity of the interface between atmosphere, ocean, and land surfaces provide an opportunity for further emergent complexities to arise, and so it is on planetary surfaces that life has its best opportunity during the Stelliferous Era.

Planetary endemism does not rule out exotic forms of life not derived from water and organic macro-molecules, nor does it rule out life arising in locations other than planetary surfaces, but the nature of the Stelliferous Era and the conditions of the universe we observe points to planetary surfaces being the most common locations for life during the Stelliferous Era. Also, the “planetary” in “planetary endemism” should not be construed too narrowly: moons, planetesimals, asteroids, comets and other bodies within a planetary system are also chemically complex loci where stellar insolation can drive further chemical processes, with the possibility of emergent complexities arising in these contexts as well.

The Homeworld Effect

The homeworld effect is the perspective of intelligent agents still subject to planetary endemism. When the emergent complexities fostered by planetary endemism rise to the level of biological complexity necessary to the emergence of consciousness, there are then biological beings with a point of view, i.e., there is something that it is like to be such a biological being (to draw on Nagel’s formulation from “What is it like to be a bat?”). The first being on Earth to open its eyes and look out onto the world possessed the physical and optical perspective dictated by planetary endemism. As biological beings develop in complexity, adding cognitive faculties, and eventually giving rise to further emergent complexities, such as art, technology, and civilization, embedded in these activities and institutions is a perspective rooted in the homeworld effect.

The emergent complexities arising from the action of intelligent agents are, like the biological beings who create them, derived from the biosphere in which the intelligent agent acts. Thus civilization begins as a biocentric institution, embodying the biophilia that is the cognitive expression of biocentrism, which is, in turn, an expression of planetary endemism and the nature of the intelligent agents of planetary endemism being biological beings among other biological beings.

The homeworld effect does not rule out the possibility of exotic forms of life or unusual physical dispositions for life that would not evolve with the homeworld effect as a selection pressure, but given that planetary endemism is the most likely existential condition of biological beings during the Stelliferous Era, it is to be expected that the greater part of biological beings during the Stelliferous Era are products of planetary endemism and so will be subject to the homeworld effect.

The Overview Effect

The overview effect is a consequence of transcending planetary endemism. As biocentric civilizations increase in complexity and sophistication, deriving ever more energy from their homeworld biosphere, biocentric institutions and practices begin to be incrementally replaced by technocentric institutions and practices and civilization starts to approximate a technocentric institution. The turning point in this development is the industrial revolution.

Within two hundred years of the industrial revolution, human beings had set foot on a neighboring body of our planetary system. If a civilization experiences an industrial revolution, it will do so on the basis of already advancing scientific knowledge, and within an historically short period of time that civilization will experience the overview effect. But the unfolding of the overview effect is likely to be a long-term historical process, like the scientific revolution. Transcending planetary endemism means transcending the homeworld effect, but as the homeworld effect has shaped the biology and evolutionary psychology of biological beings subject to planetary endemism, the homeworld effect cannot be transcended as easily as the homeworld itself can be transcended.

For biological beings of planetary endemism, the overview effect occurs only once, though its impact may be gradual and spread out over an extended period of time. An intelligent agent that has evolved on the surface of its homeworld leaves that homeworld only once; every subsequent world studied, explored, or appropriated (or expropriated) by such beings will be first encountered from afar, over astronomical distances, and known to be a planet among planets. A homeworld is transcended only once, and is not initially experienced as a planet among planets, but rather as the ground of all being.

The uniqueness of the overview effect to the homeworld of biological beings of planetary endemism does not rule out further overview effects that could be experienced by a spacefaring civilization, as it eventually is able to see its planetary system, its home galaxy, and its supercluster as isolated wholes. However, following the same line of argument above — stars and their planetary systems being common during the Stelliferous Era, emergent complexities appearing on planetary surfaces characterizing planetary endemism, organisms and minds evolving under the selection pressure of the homeworld effect embodying geocentrism in their sinews and their ideas — it is to be expected that the overview effect of an intelligent agent first understanding, and then actually seeing, its homeworld as a planet among other planets, is the decisive intellectual turning point.

Bifurcation of Planetary and Spacefaring Civilizations

What I have tried to explain here is the tightly-coupled nature of these concepts, each of which implicates the others. Indeed, the four concepts outlined above — the Stelliferous Era, planetary endemism, the homeworld effect, and the overview effect — could be used as the basis of a periodization that should, within certain limits, characterize the emergence of intelligence and civilization in any universe such as ours. Peer civlizations would emerge during the Stelliferous Era subject to planetary endemism, and passing from the homeworld effect to the overview effect.

If such a civilization continues to develop, fully conscious of the overview effect, it would develop as a spacefaring civilization evolving under the (intellectual) selection pressure of the overview effect, and such a civilization would birfurcate significantly from civilizations of planetary endemism still exclusively planetary and still subject to the homeworld effect. These two circumstances represent radically different selection pressures, so that we would expect spacefaring civilizations to rapidly speciate and adaptively radiate once exposed to these novel selection pressures. I have previously called this speciation and adaptive radiation the great voluntaristic divergence.

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Overview Effects

● The Epistemic Overview Effect

● The Overview Effect as Perspective Taking

● Hegel and the Overview Effect

● The Overview Effect in Formal Thought

● Brief Addendum on the Overview Effect in Formal Thought

● A Further Addendum on the Overview Effect in Formal Thought, in the Way of Providing a Measure of Disambiguation in Regard to the Role of Temporality

● Our Knowledge of the Internal World

● Personal Experience and Empirical Knowledge

● The Overview Effect over the longue durée

● Cognitive Astrobiology and the Overview Effect

● The Scientific Imperative of Human Spaceflight

Homeworld Effects

● The Homeworld Effect and the Hunter-Gatherer Weltanschauung

● The Martian Standpoint

● Addendum on the Martian Standpoint

● Hunter-Gatherers in Outer Space

● What will it be like to be a Martian?

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The Technocentric Thesis

Thursday

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A biological being among biological beings

A human being is a being among beings, and moreover a biological being among biological beings. We come to an awareness of ourselves, and of what we are, in a biological context. Biophilia, then, is a default consequence of being biological and finding oneself in a biological content; biophilia is a cognitive bias of biological beings. (Previously I considered the relationship between our biological nature and our biological bias in Biocentrism and Biophilia.) From both our biocentrism and our biophilia follows biocentric civilization, which I formulated in terms of the biocentric thesis, so it is natural that I would next attempt to formulate a technocentric thesis, as I have often contrasted biocentric and technocentric conceptions.

Until quite recently there was no possibility of pursing a non-biophilic bent, i.e., of pursuing a technocentric bent. Over the past several thousand years of human civilization, individual human beings had a limited opportunity to immerse themselves into the human world of civilization, and this civilization has been predominantly and pervasively biocentric. Since the Industrial Revolution, however, after which both agriculturalism and pastoralism became economically marginal, and the adoption of technology greatly increased, the ability to separate oneself from biocentric institutions has increased proportionately, but the individual has remained himself a biological being, tied to the biological world through existential needs for personal sustenance. Thus our being biological has repeatedly brought us back to our biological origins. If civilization were to fail, we could still return to an almost exclusively biocentric context and — at least for those who survived this traumatic transition — life would go on.

The emergence of a technological milieu following the industrial revolution suggests the possibility of a technocentric civilization that is the successor to biocentric civilization. Indeed, we may even understand the emergence of a fully technocentric civilization as the telos of industrialized civilization. We can formulate this in greater generality, as this process may hold for any civilization whatsoever that originates as a civilization of planetary endemism and makes the transition to a technological civilization.

Should the intelligent (biological) agents that build a civilization cease to be biological and become, for example, technological instead of biological, over time those intelligent agents could grow apart from their biocentric origins, and the social institutions in which these intelligent agents participate will become increasingly less biocentric. Biocentricity, then, is a function of biological origins, i.e., biocentrism is a consequence of being biological (as I put it in The Biocentric Thesis), and biophilia is an expression of biocentricity. As a technological civilization grows away from its biocentric origins, it is likely to become less biophiliac over time, which will in turn allow for greater expression of technophilia.

An explicit formulation of the technocentric thesis

Let us try to give these ideas a more explicit formulation:

The Technocentric Thesis

Any fully technocentric civilization has evolved from a previous biocentric civilization by descent with modification.

…which implies its corollary formulated in the negative…

Technocentric Corollary

No civilization originates as a technocentric civilization.

By a “biocentric civilization” I mean a civilization that exemplifies the biocentric thesis. I have formulated a strong biocentric thesis (all civilizations in our universe begin as biocentric civilizations originating on planetary surfaces) and a weak biocentric thesis (all civilizations during the Stelliferous Era begin as biocentric civilizations originating on planetary surfaces), each of which has a corollary formulated in the negative. The technocentric thesis could also be given strong and weak formulations, e.g., all technocentric civilizations in our universe evolve from biocentric civilizations (strong) and all technocentric civilizations during the Stelliferous Era evolve from biocentric civilizations (weak). The weaker formulation is in each case constrained by temporal parameter while the stronger formulation is unconstrained.

The mechanism by which a technocentric civilization evolves from a biocentric civilization I call replacement, and replacement can be formulated as the replacement thesis:

The Replacement Thesis

All technocentric civilizations begin as biocentric civilizations and are transformed into technocentric civilizations through the replacement of biological constituents with technological constituents.

This in turn implies a negative formulation as its corollary:

Replacement Thesis Corollary

No technocentric civilization originates as a technocentric civilization, but emerges by replacement from a biocentric civilization of planetary endemism.

How far can replacement go? We can already see in our own industrialized civilization partial replacement, but can there be a complete replacement of biological constituents by technological constituents? For any civilizations originating in intelligent biological organisms, it is unlikely that living organisms could ever be completely eliminated, but they may be rendered superfluous for all practical purposes (i.e., superfluous to civilization).

The argument from consciousness

It would be possible to construct a scenario in which biology can never be completely eliminated as a constituent of civilization. Consider the following scenario, which I will call the argument from consciousness, based on the indispensability of consciousness to civilization and the unknown parameters of machine consciousness.

The Argument from Consciousness

I will assume that there is such a thing as consciousness, that human beings are conscious at least some of the time, and that this human consciousness plays a significant role in human existence and in the civilizations built by human beings. (It is necessary to make these rudimentary stipulations because it is not unusual to find consciousness dismissed, or called an “illusion,” or to see its role in the world minimized or marginalized.)

The view is prevalent, perhaps even dominant, in AI circles such that anything that can pass the Turing test must be called conscious. There is a degree of mutual reinforcement between this common view among AI researchers and the tacit positivism that continues to influence the development of contemporary science, which consigns consciousness of the sphere of metaphysics and thus rules out in principle any metaphysical entity that is consciousness. I will not here attempt to make a case for consciousness as a metaphysical entity, but I will assume, for the purposes of what follows, that a principled refusal to consider consciousness is a barrier to understanding human behavior, including the behavior of building civilizations.

Since we do not yet know what consciousness is, and we cannot produce a scientific account of consciousness, we do not know what the conditions of consciousness are. If we had a scientific theory of consciousness that allowed us to quantify consciousness by taking meaningful measures of consciousness, any putative consciousness, whether generated by a mechanism or by biology, natural or modified or fully synthetic, could be tested by such measures of consciousness and objectively determined to be conscious or not. We do not as yet possess any such science, nor can we take any such measurements.

Human and animal consciousness constitute existence proofs of the possibility of consciousness arising by natural means, and thus consciousness ought to be amenable to study by methodological naturalism, and also to replication. It is possible that consciousness can only be produced by biological means, i.e., it is possible that machine consciousness cannot be generated. The existence proof of consciousness provided by biological beings is not an existence proof of machine consciousness. Now, I personally think that machine consciousness will eventually come about, but we will not know that this is possible until it has been achieved.

Even if machine consciousness is impossible, it would still be possible to engineer consciousness by biological means, employing some variation on existing biological substrates of consciousness, or producing consciousness by way of synthetic or artificial biology. In this case, a civilization (or post-civilizational social institution) that preserves consciousness, or desires to preserve consciousness, will not be able to become purely technocentric in the sense of entirely eliminating biology, though the biology that is retained may be entirely subordinated to technical means and technical institutions. A civilization that retained consciousness through such biological means, but entirely within a technocentric context, could be called a technocentric civilization in which biology was ineradicable.

The argument from consciousness is merely an argument (and not a proof of anything), because the same absence of a science of consciousness that would allow us to take objective measures of consciousness is the absence of a science that would make it possible to prove either that consciousness can inhere in different kind of substrates (biological or mechanical, for example), or that consciousness can only be generated through biological means. Until we have a science of consciousness, we can advance this line of argumentation only through existence proofs, i.e., proofs of concept.

Even then, even given building a conscious machine, without a science of consciousness we would have no way to rigorously and objectively compare and contrast human consciousness with machine consciousness. One way to resolve this dilemma is the Turing test, as noted above, but no one who has any degree of scientific curiosity could be satisfied with cutting the Gordian knot of consciousness rather than unraveling it.

Final thought

One of the virtues of explicitly formulating one’s ideas as theses (or as arguments), as in the above, is that one can then turn to the explicit criticism of these theses, especially to the task of unpacking the assumptions embedded in the theses. Another virtue of explicit formulations is that they can be explicitly falsified. The existence of a civilization not derived from biological complexity emergent on a planetary surface would falsify the biocentric thesis.

These explicit formulations, then, are not be taken as definitive formulations. I do not consider the biocentric thesis, the technocentric thesis, or the replacement thesis to be in any sense definitive, but rather to be a point of departure in an analysis of the nature of civilization taken in its broadest signification and extrapolated to a cosmological scale. Thus I hope to return to each of these theses in order to tease out their assumptions in order to analytically approach the intuitive conception of civilization with which I began.

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The Biocentric Thesis

Tuesday

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The biocentric character of contemporary civilization is strikingly evident in aerial photographs.

The Centrality of Biology to Civilization

Beyond the formulation of the biological conception of civilization and the ecological conception of civilization, both of which employ concepts from biology, we can identify a particular thesis (or particular theses) addressing the centrality of biological relationships and biological entities to civilization (as we have known civilization to date). I have expressed the centrality of biology to civilization as the biocentric thesis.

Although I have not previously formulated the biocentric thesis explicitly (here I will attempt to do this) though I have used the idea many times. Previously I wrote about biocentric civilizations in From Biocentric Civilization to Post-biological Post-Civilization, Addendum on the Stages of Civilization, and Another Way to Think about Civilization, inter alia, without attempting to clarify my use of “biocentric,” while in The Biological Conception of Civilization and The Ecological Conception of Civilization I considered biologically-derived conceptions of civilization.

Even our mythologies have involved the close association of human beings with fellow biological beings, as in this depiction of the earthly paradise. (‘The garden of Eden with the fall of man,’ Peter Paul Rubens and Jan Brueghel the Elder, 1615)

On Being Biological

Let us begin with the basics: human beings, the progenitors of terrestrial civilization, are biological. Being ourselves biological entities, human life has been integral with the biological world from which it arose. We live by consuming other biological entities, and, when we die, our bodies decompose and their constituents are reintegrated with the biological world from which we sprang. When human beings began the civilizational project, we remained integral with the biological world, exapting it for our new-found purposes, which involved the tightly-coupled coevolutionary cohort of species that I employed as the biological conception of civilization. In western thought it as been traditional to oppose nature to culture, but, being biological, we understand our civilization by understanding ourselves, and we understand ourselves by understanding biology.

Biology is both an old and a young science. Plato had little use for biology, and in reading Plato’s dialogues one could be forgiven for supposing that the Greeks had ever lived in any condition other than a civilization in which nature is kept at a certain distance. Aristotle, on the contrary, was a careful observer of nature, thus we may say that biology as science goes back at least to Aristotle’s treatises The History of Animals, On the Parts of Animals, On the Motion of Animals, and On the Gait of Animals.

Biology in its contemporary form goes back to Darwin, from which time biology has rapidly advanced and is today a mature science, as sophisticated in its own way as particle physics. And while we do not usually think of the growing rigor and sophistication of a body of scientific knowledge as an exercise in introspection, in the case of biology we can think of it in this way — if only we have the hardihood to apply what we have learned from biology to ourselves and to our biologically-based civilization. Because we are biological beings, knowledge of biology is knowledge of ourselves.

In this photograph we not only see the human imprint on the landscape, but also the projection of human civilization into Earth orbit.

Being Biological in an Astrobiological Context

Astrobiology is a very young science, but in so far as it takes up the torch of biology and extrapolates biological concepts to their ultimate cosmological context, astrobiology is simply a greatly expanded biology, and in this sense not a new science at all. In From an Astrobiological Point of View I characterized the emergence of astrobiology in this spirit of continuity as the fourth of four great revolutions in biology, the previous three revolutions being Darwinism, Mendelian genetics, and evolutionary developmental biology (better known as “evo-devo”).

In the context of astrobiology, understanding the conditions for life in the universe is a greatly expanded form of human introspection, in which an evolving body of scientific knowledge has the capability of demonstrating the cosmological context of human life. Once again, in understanding astrobiology we can better understand ourselves, if only we have the willingness to understand ourselves scientifically. Beyond understanding ourselves, astrobiology also holds the promise of better understanding our civilization. An astrobiological formulation of the biological conception of civilization would extrapolate this conception of civilization to a cosmological scope.

In Astrobiology is island biogeography writ large I suggested that spaceflight is to astrobiology as flight is to biogeography, which is an application of the principle that technology is the pursuit of biology by other means. Given technologically-enabled spaceflight (made possible by a technological civilization), terrestrial life can expand beyond Earth and beyond our planetary system to other worlds, just as the innovation of flight made it possible for terrestrial organisms (even those that do not fly) to establish themselves on distant, isolated islands — hence the analogy between biogeographical distribution patterns and astrobiological distribution patterns. This is still a biocentric paradigm, but extrapolated to cosmological scope.

Biocentric Theses

With these considerations of what it means to be a biological being in an astrobiological context, I will attempt an explicit formulation of weak and strong biocentric theses. All of these formulations involve what I have earlier called planetary endemism.

The Weak Biocentric Thesis

All civilizations during the Stelliferous Era begin as biocentric civilizations originating on planetary surfaces.

This thesis is “weak” because it addresses only civilizations during the Stelliferous Era. A corollary of the weak biocentric thesis excludes the possibility of any Stelliferous Era civilization that does not arise from biology, as follows:

Corollary of the Weak Biocentric Thesis

No civilizations during the Stelliferous Era existed prior to the advent of Stelliferous Era biota.

The weak biocentric thesis and its corollary implies a strong biocentric thesis, not limited to the Stelliferous Era:

The Strong Biocentric Thesis

All civilizations in our universe begin as biocentric civilizations originating on planetary surfaces.

The strong biocentric thesis also has a strong corollary:

Corollary of the Strong Biocentric Thesis

No civilizations existed in our universe prior to the biocentric civilizations of Stelliferous Era.

Both strong and weak biocentric theses and their corollaries entail that the emergent complexity of civilization arises from the previous emergent complexity of life, and, in their strongest formulations, that it could be no other way. This excludes the possibility that there exist forms of emergent complexity other than life — sufficiently distinct from life as we know it than any identification of this emergent complexity as life would be problematic — from which civilization might independently arise. This is a rather sweeping claim, and, though it is supported by our parochial knowledge of life and civilization on Earth, it would be quite a stretch to assert this for the universe entire. On the other hand, we would still want to entertain this possibility, as there may be universes in which the only emergent complexity upon which civilization can supervene is life, more or less as we know it.

If the Strong Biocentric Thesis and its corollary are true, then there are no pre-Stelliferous Era civilizations, and all post-Stelliferous Era civilizations are derived from Stelliferous Era civilizations having their origins in planetary endemism. Post-Stelliferous Era civilizations would include Degenerate Era civilizations, Black Hole Era civilizations, and Dark Era civilizations. This might be formulated as another thesis in turn.

According to this understanding of civilization, the Stelliferous Era is uniquely generative of civilizations. In so far as we understand civilizations to belong to a suite of emergent complexities, we might say instead that the Stelliferous Era is uniquely generative of emergent complexity. At least, we say that now, prior to the emergent complexities unique to the Degenerate Era. It seems likely, however, that at some point the universe will reach peak complexity, and after that point it will begin to decay, and emergent complexities will begin to disappear, one by one.

The Terrestrial Eocivilization Hypothesis and Darwin’s Thesis

The above is closely related to what I have previously called the Terrestrial Eocivilization Hypothesis, which I characterized as follows:

“I will call the terrestrial eocivilization hypothesis the position that identifies early civilization, i.e., eocivilization, with terrestrial civilization. In other words, our terrestrial civilization is the earliest civilization to emerge in the cosmos. Thus the terrestrial eocivilization hypothesis is the civilizational parallel to the rare earth hypothesis, which maintains, contrary to the Copernican principle, that life on earth is rare. I could call it the ‘rare civilization hypothesis’ but I prefer ‘terrestrial eocivilization hypothesis’.”

This might, more simply, be called the “priority thesis,” and is to be distinguished from the “uniqueness thesis,” i.e., that there is one and only one civilization in the universe, and that one is terrestrial civilization. Thinking over this again in retrospect, I realize that priority, uniqueness, and biocentricity can be distinguished. A civilization might be unique in virtue of being first (i.e., having priority), or by being the only civilization, or by being the last of all civilizations. Thus priority is only one form of uniqueness among others. And priority and uniqueness can both be distinguished from biocentricity: according the biocentric theses above, biocentric civilization has priority (at least during the Stelliferous Era) but it not necessarily unique in the universe, nor unique to Earth. Terrestrial civilization is a biocentric civilization, and it may also have priority and it may be unique.

The biocentric theses are also related to what I have called Darwin’s Thesis on the Origins of Civilization, according to which civilization emerges from non-civilization, much as naturalistic accounts of life hold that life emerges from non-life (sometimes called abiogenesis). Whereas the priority thesis (i.e., the terrestrial eocivilization hypothesis, that the earliest civilization is terrestrial civilization) is specific to Earth, Darwin’s thesis, like the biocentric theses above, can be applied universally without reference to the historical accidents of civilization on Earth (including its emergence, and whether this emergence was earlier than or later than any other emergence of civilization).

From a scientific standpoint, then, it is more important to determine the exact logical relationships between the biocentric theses and Darwin’s thesis, as the details of what happened on Earth belong to the accidents of cosmological history. As I said in my post on Darwin’s thesis, these ideas about civilization are rudimentary in the extreme, but since a science of civilization does not yet exist, we must begin with these simplest of concepts if we are ever to think clearly about civilization.

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The Martian Standpoint

Thursday

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Red Planet Perspectives

It is difficult to discuss human habitation of Mars scientifically because Mars has for so long played an disproportionate role in fiction, and any future human habitation of Mars will take place against this imaginative background. Future human inhabitants of Mars will themselves read this cultural legacy of fiction centered on Mars, and while some of it will be laughable, there are also likely to be passages that start heads nodding, however dated and inaccurate the portrayal of human life on Mars. And this human future on Mars is seeming increasingly likely as private space enterprises vie with national space agencies, and both public and private space programs are publicly discussing the possibility of sending human beings to Mars.

Panoramic view of the Payson outcrop near the Opportunity rover’s landing site. (NASA/JPL-Caltech/USGS/Cornell)

A human population on Mars would eventually come to identify as Martians, even though entirely human — Ray Bradbury already said as much decades ago — and it would be expected that the Martian perspective would be different in detail from the terrestrial perspective, though scientifically literate persons in both communities would share the Copernican perspective. There would be countless small differences — Martians would come to number their lives both in Terrestrial years and Martian years, for example — that would cumulatively and over time come to constitute a distinctively Martian way of looking at the world. There would also be unavoidably important differences — being separated from the bulk of humanity, having no large cities at first, not being able to go outside without protective gear, and so on — that would define the lives of Martian human beings.

Wernher von Braun’s Mars mission concept as imagined by Chesley Bonestell

At what point will Martians come to understand themselves as Martians? At what point will Mars become a homeworld? There will be a first human being to set foot on Mars, a first human being born on Mars, a first human being to die on Mars and be buried in its red soil, a first crime committed on Mars, and so on. Any of these “firsts” might come to be identified as a crucial turning point, the moment at which a distinctively Martian consciousness emerges among Mars residents, but any such symbolic turning point can only come about against the background of the countless small differences that accumulate over time. Given human settlement on Mars, this Martian consciousness will surely emerge in time, but the Martian conscious that perceives Mars as a homeworld will differ from the sense in which Earth is perceived as our homeworld.

An actual, and not a mythical, canal on Mars.

Human beings lived on Earth for more than a hundred thousand years without knowing that we lived on a planet among planets. We have only known ourselves as a planetary species for two or three thousand years, and it is only in the past century that we have learned what it means, in a scientific sense, to be a planet among countless planets in the universe. A consequence of our terrestrial endemism is that we as a species can only transcend our homeworld once. Once and once only we ascend into the cosmos at large; every other celestial body we visit thereafter we will see first from afar, and we will descend to its surface after having first seen that celestial body as a planet among planets. Thus when we arrive at Mars, we will arrive at Mars knowing that we arrive at a planet, and knowing that, if we settle there, we settle on a planet among planets — and not even the most hospitable planet for life in our planetary system. In the case of Mars, our knowledge of our circumstances will precede our experience, whereas on Earth our experience of our circumstances preceded our knowledge. This reversal in the order of experience and knowledge follows from planetary endemism — that civilizations during the Stelliferous Era emerge on planetary surfaces, and only if they become spacefaring civilizations do they leave these planetary surfaces to visit other celestial bodies.

A sunset on Mars photographed by NASA’s Mars Exploration Rover Spirit

What is it like, or what will it be like, to be a Martian? The question immediately reminds us of Thomas Nagel’s well known paper, “What is it like to be a bat?” (I have previously discussed this famous philosophical paper in What is it like to be a serpent? and Computational Omniscience, inter alia.) Nagel holds that, “…the fact that an organism has conscious experience at all means, basically, that there is something it is like to be that organism.” A generalization of Nagel’s contention that there is something that it is like to be a bat suggests that there is something that it is like to be a conscious being that perceives the world. If we narrow our conception somewhat from this pure generalization, we arrive at level of generality at which there is something that it is like to be a Terrestrial being. That there is something that it is like to be a bat, or a human being, are further constrictions on the conception of being a consciousness being that perceives the world. But at the same level of generality that there is something that it is like to be a Terrestrial being, there is also something that it is like to be a Martian. Let us call this the Martian standpoint.

Seeing Earth as a mere point of light in the night sky of Mars will certainly have a formative influence on Martian consciousness.

To stand on the surface of Mars would be to experience the Martian standpoint. I am here adopting the term “standpoint” to refer to the actual physical point of view of an intelligent being capable of looking out into the world and understanding themselves as a part of the world in which they find themselves. Every intelligent being emergent from life as we know it has such a standpoint as a consequence of being embodied. Being an embodied mind that acquires knowledge through particular senses means that our evolutionary history has furnished us with the particular sensory endowments with which we view the world. Being an embodied intelligence also means having a particular spatio-temporal location and having a perspective on the world determined by this location and the sensory locus of embodiment. The perspective we have in virtue of being a being on the surface of a planet at the bottom of a gravity well might be understood as a yet deeper level of cosmological evolution than the terrestrial evolutionary process that resulted in our particular suite of sensory endowments, because all life as we know it during the Stelliferous Era originates on planetary surfaces, and this precedes in evolutionary order the evolution of particular senses.

Sometimes the surface of Mars looks strangely familiar, and at other times profoundly alien.

Mars, like Earth, will offer a planetary perspective. Someday there may be great cities and extensive industries on the moon, supporting a burgeoning population, but, even with cities and industries, the moon will not be a world like Earth, with an atmosphere, and therefore a sky and a landscape in which a human being can feel at home. For those native to Mars — for eventually there will be human beings native to Mars — Mars will be their homeworld. As such, Mars will have a certain homeworld effect, though limited in comparison to Earth. Even those born on Mars will carry a genome that is the result of natural selection on Earth; they will have a body created by the selection pressures of Earth, and their minds will function according to an inherited evolutionary psychology formed on Earth. Mars will be a homeworld, then, but it will not produce a homeworld effect — or, at least, no homeworld effect equivalent to that experienced due to the origins of humanity on Earth. The homeworld effect of Mars, then, will be ontogenic and not phylogenic.

The von Braun Mars mission concept was visionary for its time.

If, however, human beings were to reside on Mars for an evolutionarily significant period of time, the ontogenic homeworld effect of individual development on Mars would be transformed into a phylogenic homeworld effect as Mars became an environment of evolutionary adaptedness. As the idea of million-year-old or even billion-year-old civilizations is a familiar theme of SETI, we should not reject this possibility out of hand. If human civilization comes to maturity within our planetary system and conforms to the SETI paradigm (i.e., that civilizations are trapped within their planetary systems and communicate rather than travel), we should expect such an eventuality, though over these time scales we will probably change Mars more than Mars will change us. At this point, Mars would become a homeworld among homeworlds — one of many for humanity. But it would still be a homeworld absent the homeworld effect specific to human origins on Earth — unless human beings settled Mars, civilization utterly collapsed, resulting in a total ellipsis of knowledge, and humanity had to rediscover itself as a species living on a planetary surface. For this to happen, Mars would have to be Terraformed in order for human beings to live on Mars without the preservation of knowledge sufficient to maintain an advanced technology, and this, too, is possible over time scales of a million years or more. Thus Mars could eventually be a homeworld for humanity in a sense parallel to Earth being a homeworld, though for civilization to continue its development based on cumulative knowledge implies consciousness of only a single homeworld, which we might call the singular homeworld thesis.

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The descent to the surface of Mars will shape our perception of the planet.

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Civilizations of Planetary Endemism: Part V

Friday

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‘This is an artist’s impression of innumerable Earth-like planets that have yet to be born over the next trillion years in the evolving universe.’
Credits for image and text: NASA, ESA, and G. Bacon (STScI)

Review of Planetary Endemism

So that the reader doesn’t lose the thread of this series on planetary endemism (and to remind myself as well), I began by attempting to formulate a “big picture” taxonomy of planetary civilizations (Part I), but realized that this taxonomy ought to acknowledge the differences in civilization that would follow from civilizations emerging on different kinds of planets (Part II). Then I focused on the question, “What physical gradient is, or would be, correlated with the greatest qualitative gradient in the civilization supervening upon that physical gradient?” (Part III), and next considered how fundamentally different forms of energy flow would beget different kinds of biospheres, which would in turn result in different kinds of civilizations supervening upon these biospheres (Part IV).

This discussion of planetary civilization in terms of planetary endemism provides a new perspective on how we are to understand a civilization that has expanded to the limits dictated by planetary constraints. I have learned that most attempts to discuss planetary civilization get hung up on assumptions of global political and legal unification, which then inevitably gets hung up on utopianism, because nothing like global political and legal unification is on the horizon so this can only be discussed in utopian terms. Thinking about civilization, then, in terms of planetary endemism allows us to get to the substance of planetary civilization without getting distracted by utopian proposals for world government. And what I find to be the substance of planetary civilization is the relationship of a civilization to the intelligent species that produces a civilization, and the relation of an intelligent species to the biosphere from which it emerges.

Thinking about biospheres

How can we scientifically discuss biospheres when we have only the single instance of the terrestrial biosphere as a reference? In order to discuss planetary civilizations scientifically we need to be able to scientifically discuss the biospheres upon which these civilizations supervene. We need a purely formal and general conception of a biosphere not tied to the specifics of the terrestrial biosphere. Ecology is not yet at the stage of development at which it can make this leap to full formalization, but we can make some general remarks about biospheres, continuous with previous observations in this series.

In the Immediately previous post in this series, Part IV, I considered the possibilities of biospheres that fall short of expanding to cover the entire surface of a planet, and so are not quite a biosphere, but constitute what we might call a partial biosphere. In that post I mentioned the terminological difficulties of finding an appropriate word for this and suggested that topology might provide some insight.

Biospheres and Partial Biospheres

In topology, a biosphere would be what is called a spherical shell, which is bounded by two concentric spheres of different radii. This is the three dimensional extrapolation of what mathematicians call an annulus, which is the area bounded by two concentric circles of different radii. Understanding the biosphere as a spherical shell is a good way to come to an appreciation of the “thickness” of the biosphere. The Terrestrial biosphere may be understood as that spherical shell bounded by the deepest living microbes as the shorter radius and the upper atmosphere as the longer radius. The entry on Deep Subsurface Microbes at MicrobeWiki states: “In oceanic crusts, the temperature of the subsurface increases at a rate of about 15 degrees C per kilometer of depth, giving a maximum livable depth of about 7 kilometers.” The convention establishing the distinction between the upper atmosphere and extraterrestrial space is the Kármán line, 100 km above Earth’s surface. Taking these as the deepest and highest figures, the terrestrial biosphere is a spherical shell approximately 107 km thick, though more conservative numbers could also be employed (as in the illustration above).

A partial biosphere that failed to expand across an entire planetary surface would in topological terms be a punctured spherical shell. Now, a punctured spherical shell is continuously deformable into a sphere, making the two topologically equivalent. This may sound a bit strange, but there is an old joke that a topologist is someone who can’t tell the difference between a doughnut and a coffee cup: each is continually deformable into the other (i.e., both are topologically equivalent to a torus, which is what topologists call a genus 1 surface). In topological terms, then, there is little difference between a biosphere and a partial biosphere (I will discuss a prominent exception in the next installment of this series).

While there is no topological difference between a biosphere and a partial biosphere, there could be a dramatic ecological difference, as a partial biosphere that covered too small of a proportion of a planetary surface would at some point fall below the threshold of viability, while, at the other end of the scale, if it becomes sufficiently extensive it passes the threshold beyond which it can support the evolution of complex life forms. And since only complex life forms produce civilizations, there may be a threshold below which a partial biosphere cannot be associated with a biota of sufficient complexity to allow for the emergence of an intelligent species and hence a civilization.

The extent of a biosphere may place a constraint upon life and civilization emerging from smaller celestial bodies, such as exomoons. So it is not only the possibility of a partial biosphere that may limit the development of complexity in a biota. On the other hand, a system of exomoons, i.e., several inhabitable exomoons orbiting an exoplanet, may have the opposite effect, serving as a speciation pump, leading to higher biodiversity and the emergence of higher forms of emergent complexity. Earlier I suggested that astrobiology is island biogeograpy writ large; a system of inhabitable exomoons, each with its own biosphere, orbiting an exoplanet would offer a particular elegant test of this idea, should we ever discover such a system (and in the immensity of the universe it seems likely that something like this would have happened at least once).

The topology of the biology of a system of exomoons no longer even approximates a biosphere, and this points to the limitation of the concept of a biosphere, and the need for a formalized science of inhabitability that is applicable to any inhabitable region whatever. However, this still is not sufficient for our needs. We must recognize the degree of biological relatedness or difference among separate but biologically related worlds as in the example above.

“This artist’s concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. X-rays emerge from the very central region, while thermal infrared radiation is emitted by dust throughout most of the torus. While this figure shows the quasar’s torus approximately edge-on, the torus around APM 08279+5255 is likely positioned face-on from our point of view.” (Image and text: NASA/ESA)

The long tail of planetary habitability

However exotic the topology of biospheres to be found in the universe, the biochemistry that populates these biologically connected regions is likely to be constrained by the chemical makeup of the universe. This chemical makeup seems to point to vaguely anthropocentric conditions for life in the universe, but this should not surprise us, as it would be a confirmation of the principle of mediocrity in biology. Water and carbon-based biochemistry is the basis of life on Earth, and the prevalence of these elements in the cosmos at large suggests this as the most common basis of life elsewhere.

Not only are there likely to be liquid subsurface oceans on Europa, Enceladus, and other moons of the outer solar system, possibly with a greater total amount of water on some of these small moons than in all the oceans of Earth, so that we know our solar system possesses enormous resources of water, but we now also know that the universe beyond our solar system possesses significant water resources. The discovery of water vapor at the quasar APM 08279+5255 (described in Astronomers Find Largest, Most Distant Reservoir of Water) represents the presence of vast amounts of water 12 billion light years away — so also 12 billion years in the past — demonstrating both the pervasive spatial and temporal distribution of water in the universe. Astrobiologists have been saying, “To find life, follow the water,” but we now know that following the water would take us far afield.

In additional to water being common in the universe, carbon-based organic chemistry is also known to be common in the universe:

“Astronomers who study the interstellar medium… have found roughly 150 different molecules floating in space… The list boasts many organic (which is to say, carbon-containing) molecules, including some sugars and a still controversial detection of the simplest amino acid, glycine…”

Seth Shostak, Confessions of an Alien Hunter: A Scientist’s Search for Extraterrestrial Intelligence, Washington, DC: National Geographic, 2009, p. 260

Thus, not only is water pervasively present in the universe, but so also are the basic molecules of organic chemistry. I had something like this in mind when in previous post (and elaborated in Not Terraforming, but Something Else…) I tried to outline what might be called variations on the theme of carbon-based life:

“…if life in the outer solar system is to be found, and it is significantly different from life of the inner solar system, how do we recognize it as life? How different is different? It is easy to imagine life that is different in detail from terrestrial life, but, for all intents and purposes, the same thing. What do I mean by this? Think of terrestrial DNA and its base paring of adenine with thymine, and cytosine with guanine: the related but distinct RNA molecule uses uracil instead of thymine for a slightly different biochemistry. Could something like DNA form with G-U-A-C instead of G-T-A-C? Well, if we can consider RNA as being ‘something like’ DNA, then the answer is yes, but beyond that I know too little of biochemistry to elaborate. As several theories of the origins of life on Earth posit the appearance of RNA before DNA, the question becomes whether the ‘RNA world’ of early life on Earth might have also been the origin of life elsewhere, and whether that RNA world matured into something other than the DNA world of terrestrial life.”

I think this is similar to some of the points made by Peter Ward in his book Life as We Do Not Know It, in which Ward wrote:

“…the simplest way to make an alien would be to change DNA slightly. Our familiar DNA is a double helix made up of two on strands of sugar, with the steps of this twisted ladder made up of four different bases. The code is based on triplet sequences, with each triplet either an order to go fetch a specific amino acid or a punctuation mark like ‘stop here.’ Within this elaborate system there are many specific changes that could be made — at least theoretically — that would be ‘alien’ yet might still work.”

Peter Ward, Life as We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life, New York et al.: Penguin, 2005, p. 66-67

Ward considers variations such as changing the backbone of RNA, changing or adding proteins, changing chirality (the direction of the DNA spiral), changing solvents (i.e., a medium for biochemistry other than water), and substituting proteins for nucleic acids. All of these, I think, count as variations on the theme of carbon-based life, which is what we are to expect in the universe rich in carbon-based organic molecules.

Alternative biochemistries with methane-metabolizing microorganisms as described in the recent paper Methane metabolism in the archaeal phylum Bathyarchaeota revealed by genome-centric metagenomics might also be consistent with the dominant chemistry observed in the universe, and would constitute slightly more exotic variations on the theme of carbon-based life. Just as we will have investigated the subsurface oceans of the moons of the outer planets and will know how readily biochemistry emerges in these environments before we even pass the threshold of our own solar system to become an interstellar civilization, so too we will have the opportunity within our own solar system to investigate alternative biochemistries in environments such as Saturn’s moon Titan.

Both water and carbon-based organic chemistry are common in the universe during the Stelliferous Era in the same way that planetary surfaces are common loci of energy flows during the Stelliferous Era; indeed, planetary surfaces provide the vehicle upon which water and carbon-based organic chemistry can produce emergent complexity from energy flows.

The observable universe, then, is rich in planets, in water, and in organic molecules — everything for which one might hope in a search for life. There is no reason for our universe not to be a living universe, in which biochemistry is as common — or will be as common — as as there are planetary surfaces providing energy flows consistent with life as we know it. However, these multitudinous opportunities for life will be constrained by the prevalent organic chemistry of the universe, and this points to variations on the theme of carbon-based like. Other forms of life may exist as outliers, just as biospheres may be driven by energy flows other than insolation, but these will be unusual.

Provisional conclusions

As a provisional conclusion we assert that the same reasoning that leads us to planetary surfaces as the “Goldilocks” zone for energy flows during the Stelliferous Era also leads us to carbon-based life forms employing liquid water as a solvent during the same period of cosmological natural history.

Having thought a bit about the different kind of biospheres that might be possible given different forms of energy flow (Part IV), I have realized that these are probably outliers, and, if we remain focused on civilizations of the Stelliferous Era, insolation of planetary surfaces will be the primary source of energy flows, hence the primary basis of biospheres during the Stelliferous Era, hence the primary basis of civilization up to the point of development when biocentric civilization transitions into technocentric civilization and is no longer exclusively dependent upon a biosphere.

That being said, other sources of energy flow may play a significant role. Radioactive decay has played a significant role in the temperature of Earth (not taking account of radioactive decay, which was not then known, was the reason for Lord Kelvin’s attack on Darwinian time scales). Extrapolating from our own biosphere, we would expect to see a variety of biospheres in which stellar insolation is supplemented by other drivers of energy flow.

Later in the Stelliferous Era, when planetary systems have a greater proportion of heavy elements (due to the process of chemical enrichment), the habitable zone may move further out from parent stars because of the increased availability radioactive decay and natural fission reactors contributing relatively more to the energy flows of biospheres. The increased availability of heavier elements may also eventually impact biochemisty, as forms of life as we do not know it become more likely as the overall mixture of chemicals in the universe matures. The farther we depart in time from the present moment of cosmological natural history, the farther we depart from likely energy flows and biota depending upon these energy flows, until we reach the end of the Stelliferous Era. All that I have written above concerning the Stelliferous Era will cease to be true in the Degenerate Era, when stellar insolation ceases to be a source of energy flows.

For the time being, however, throughout the Stelliferous Era we can count on certain predictable features of life and civilization. Civilization follows intelligence, intelligence follows complex life, and complex life follows from habitability that passes beyond the kind of thresholds described above. Thus the cohort of emergent complexities found in the Stelliferous Era can be traced to the same root.

We may even discover that planetary biospheres exhibit a kind of convergent evolution, not in terms of specific species, but in terms of the kind of biomes and niches available, hence ecological structures to be found, and even the kinds of civilizations supervening upon these ecological structures. For example, I wrote a post on Civilizations of the Tropical Rainforest Biome: on another world with a peer biosphere and an intelligent species, any civilizations we found emergent in the equivalent of a tropical rainforest biome (high temperatures and high rainfall year round) would probably share certain structural features with civilizations of the tropical rainforest biome found on Earth.

The civilizations of planetary endemism, then, include all those classes of sub-planetary civilizations defined by regional biomes, prior to the emergence of a planetary civilization. Each regional (sub-planetary) civilization is consistent with its biome (i.e., it can supply the needs of its agents with the resources available within the biome in question), and in so far as the resources in a given biome govern what is possible for a biocentric civilization emergent within that biome, each such civilization is forced into a kind of uniformity that the institutions of civilization then take up in a spirit of iteration and refinement of a model (i.e., the iterative conception of civilization). When civilization expands until civilizations emergent in distinct biomes are forced into contact, resulting in communication, commerce, and conflict, new forms of planetary scale uniformity emerge in order to facilitate interchanges on a planetary scale.

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Planetary Endemism

● Civilizations of Planetary Endemism: Introduction (forthcoming)

● Civilizations of Planetary Endemism: Part I

● Civilizations of Planetary Endemism: Part II

● Civilizations of Planetary Endemism: Part III

● Civilizations of Planetary Endemism: Part IV

● Civilizations of Planetary Endemism: Part V

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Civilizations of Planetary Endemism: Part IV

Thursday

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“Io is the most volcanically active body in the solar system. At 2,263 miles in diameter, it is slightly larger than Earth’s moon.” (NASA)

In earlier posts of this series on Civilizations of Planetary Endemism we saw that planets not only constitute a “Goldilocks” zone for liquid water, but also for energy flows consistent with life as we know it. I would like to go into this in a little more detail, as there is much to be said on this. It is entirely possible that energy flows on a planet or moon outside the circumstellar habitable zone (CHZ) could produce sufficient heat to allow for the presence of liquid water in the outer reaches of a planetary system. Indeed, it may be misleading to think of habitable zones (for life as we know it) primarily in terms of the availability of liquid water; it might be preferable to conceive a habitable zone primarily in terms of regions of optimal energy flow (i.e., optimal for life as we know it), and to understand the availability of liquid water as a consequence of optimal energy flow.

Our conception of habitability, despite what we already know, and what we can derive from plausible projections of scientific knowledge, is being boxed in by the common conceptions (and misconceptions) of biospheres and CHZs. We can posit the possibility of “oasis” civilizations on worlds where only a limited portion of the surface is inhabitable and no “biosphere” develops, although enough of a fragment of a biosphere develops in order for complex life, intelligence, and civilization to emerge. We do not yet have an accurate term for the living envelope that can emerge on a planetary surface, but which does not necessary cover the entire planetary surface. I have experimented with a variety of terms to describe this previously. For example, I used “biospace” in my 2011 presentation “The Moral Imperative of Human Spaceflight,” but this is still dissatisfying.

As is so often the case, we run into problems when we attempt to extrapolate Earth sciences formulated for the explicit purpose of accounting for contingent terrestrial facts, and never conceived as a purely general scientific exercise applicable to any comparable phenomena anywhere in the universe. This is especially true of ecology, and since I find myself employing ecological concepts so frequently, I often feel the want of such formulations. Ecology as a science is theoretically weak (it is much stronger on its observational side, which goes back to traditional nature studies that predate ecology), and its chaos of criss-crossing classification systems reflects this.

There are a great many terms for subdivisions of the biosphere — ecozone, bioregion, ecoregion, life zone, biome, ecotope — which are sometimes organized serially from more comprehensive to less comprehensive. None of these subdivisions of a biosphere, however, would accurately describe the inhabited portion of a world on which biology does not culminate in a biosphere. Perhaps we will require recourse to the language and concepts of topology, since a biosphere, as a sphere, is simply connected. The bioring of a tidally locked M dwarf planet would not be simply connected in this topological sense.

If we conceptualize habitable zones not in terms of a celestial body being the right temperature to have liquid water on its surface, or perhaps in a subsurface ocean, but rather view this availability of liquid water as a consequence of habitable zones defined in terms of the presence of energy flows consistent with life as we know it, then we will need to investigate alternative sources of energy flow, i.e., distinct from the patterns of energy flow that we understand from our homeworld. Energy flows consistent with life as we know it are consistent with conditions that allow for the presence of liquid water on a celestial body, but this also means energy flows that would not overwhelm biochemistry and energy flows that are not insufficient for biochemistry and the origins and maintenance of metabolism.

Energy flows might be derived from stellar output (thus a consequence of gravitational confinement fusion), from radioactivity, which could take the form of radioactive decay or even a naturally-occurring nuclear reactor, as as Oklo in Gabon (thus a consequence of fission), from gravitational tidal forces, or from the kinetic energy of impacts. All of these sources of energy flows have been considered in another connection: suggested ways to resolve the faint young sun paradox (the problem that the sun was significantly dimmer earlier in its life cycle, while there still seems to have been liquid water on Earth) are the contributions of other energy sources to maintaining a temperature on Earth similar to that of today, including greater tidal heating from a closer moon, more heating from radioactive decay, and naturally occurring nuclear fission.

It would be possible in a series of thought experiments to consider counterfactual worlds in which each of these sources of energy flow are the primary source of energy for a biosphere (or a subspherical biological region of a planetary surface). The Jovian moon Io, for example, is the most volcanically active body in our solar system; while Io seems to barren, one could imagine an Io of more clement conditions for biology in which the tidal heating of a moon with an atmosphere was the basis of the energy flow for an ecosystem. A world with more fissionables in its crust than Earth (the kind of worlds likely to be found during the late Stelliferous Era under conditions of high metallicity) might be heated by radioactive decay or natural fission reactors (or some combination of the two) sufficient to generate energy flows for a biosphere, even at a great distance from its parent star. It seems unlikely that kinetic impacts from collisions could provide a sufficiently consistent flow of energy without a biosphere suffering mass extinctions from the same impacts, but this could merely be a failure of imagination. Perhaps a steady rain of smaller impacts without major impacts could contribute to energy flows without passing over the threshold of triggering an extinction event.

Each of these exotic counterfactual biospheres suggests the possibility of a living world very different from our own. The source of an energy flow might be inconsistent, that is to say, consistent up to the point of making life possible, but not sufficiently consistent for civilization, or the development of civilization. That is to say, it is possible that a planetary biosphere or subspheric biological region might possess sufficient energy flows for the emergence of life, but insufficient energy flows (or excessive energy flows) for the emergence of complex life or civilization. Once can easily imagine this being the case with extremophile life. And it is possible that a bioregion might possess sufficient energy flows for the emergence of a rudimentary civilization, but insufficient for the development of industrial-technological civilization that can make the transition to spacefaring civilization and thus ensure its longevity.

Civlizations of planetary endemism on these exotic worlds would be radically different from our own civilization due to differences in the structure and distribution of energy flow. Civilizations of planetary endemism are continuous with the biosphere upon which they supervene, so that a distinct biosphere supervening upon a distinct energy flow would produce a distinct civilization. Ultimately and ideally, these distinct forms of energy flow could be given an exhaustive taxonomy, which would, at the same time, be a taxonomy of civilizations supervening upon these energy flows.

However, the supervenience of civilization upon biosheres and biospheres upon energy flows is not exhaustive. Civilizations consciously harness energy flows to the benefit of the intelligent agent engaged in the civilizing process. The first stage of terrestrial civilization, that of agricuturalism and pastoralism, was a natural extension of energy flows already present in the bioshere, but once the breakthrough to industrialization occurred, energy sources became more distant from terrestrial energy flows. Fossil fuels are, in a sense, stored solar energy, and derive from the past biology of our planet, but this is the use of biological resources at one or more remove. As technologies became more sophisticated, in became possible to harness energy sources of a more elemental nature that were not contingent upon extant energy flows on a planet.

It may be, then, that biocentric civilizations are rightly said to supervene upon biospheres. However, with the breakthrough to industrialization, and the beginning of the transition to a technocentric civilization, this supervenience begins to fail and a discontinuity is interpolated between a civilization and its homeworld. According to this account, the transition from biocentric to technocentric civilization is the end point of civilizations of planetary endemism, and the emergence of a spacefaring civilization as the consequence of technologies enabled by technocentric civilization is a mere contingent epiphenomenon of a deeper civilizational process. This in itself provides a deeper and more fundamental perspective on civilization.

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Planetary Endemism

● Civilizations of Planetary Endemism: Introduction (forthcoming)

● Civilizations of Planetary Endemism: Part I

● Civilizations of Planetary Endemism: Part II

● Civilizations of Planetary Endemism: Part III

● Civilizations of Planetary Endemism: Part IV

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Civilizations of Planetary Endemism: Part III

Saturday

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There are a lot of Earth-like planets out there, and they vary from Earth according to physical gradients.

In my previous posts on planetary endemism (see links below) I started to explore the ideas of how civilization is shaped by the planet upon which a given civilization arises. I began to sketch a taxonomy based on developmental factors arising from planetary endemism, but I have realized the inadequacy of this. As I have no systematic idea for a taxonomy based on a more comprehensive understanding of planetary types, I must undertake a series of thought experiments to explore the relevant ideas in more detail. This I intend to do.

I should point out that taxonomy I began to sketch in my 2015 Starship Congress talk, “What kind of civilizations build starships?” — a taxonomy employing a binomial nomenclature based on a distinction between economic infrastructure and intellectual superstructure — still remains valid to make fine-grained distinctions among terrestrial civilizations, or indeed within the history of any civilization of planetary endemism. What I am seeking to do now to arrive at a more comprehensive taxonomy under which this more fine-grained taxonomy can be subsumed, and which, as a large-scale conception of civilization, is consistent with and integrated into our knowledge of cosmology and planetology.

While I have no systematic idea of taxonomy at present taking account of types of planets, I think I can identify a crucial question for this inquiry, and it is this:

What physical gradient is, or would be, correlated with the greatest qualitative gradient in the civilization supervening upon that physical gradient?

In other words, if we could experiment with civilization under controlled condition, systematically substituting different valuables for a given variable while holding all over variables constant, and these variables are the physical conditions to which a given planetary civilization is subject, which one of these variables when its value is changed would produce the greatest variation on the supervening civilization? A qualitative change in civilization yields another kind of civilization, so that if varying a physical condition produces a range of different kinds of civilizations, this is the variable to which we would want to pay the greatest attention in formulating a taxonomy of civilizations that takes into account the kind of planet on which a civilization arises. Understood in this way, civilization, or at least the kind of civilization, can be seen as an emergent property with the physical condition given a varying value as the substructure upon which emergent civilization supervenes.

Some gradients of physical conditions will be closely correlated: planet size correlates with surface area, surface gravity, and atmospheric density. These multiple physical conditions are in turn correlated with multiple constraints upon civilization. With the single variable of planet size correlated to so many different conditions and constraints upon civilization, planet size will probably figure prominently in a taxonomy of civilizations based on homeworld conditions. Large planets and small planets both have advantages and disadvantages for supervening civilizations. Large planets have a large surface area, but the higher gravity may pose an insuperable challenge for the emergence of spacefaring civilization. Small planets would pose less of a barrier to a spacefaring breakout, but they also have less surface area and probably a thinner atmosphere, possibly limiting the size of organisms that could survive in its biosphere. Also, there may be a point at which the surface area on a small planet falls below the minimum threshold necessary for the unimpeded development of civilization.

Planets too large or too small may be inhabitable, in terms of possessing a biosphere, but may be too challenging for a civilization to arise. Any intelligent being on a planet too large or too small would be faced with challenges too great to overcome, resulting in what Toynbee called an arrested civilization. But how large is too large, and how small is too small? We don’t have an answer for these questions yet, but to formulate the question explicitly provides a research agenda.

Other important physical gradients are likely to be temperature (or insolation, which largely determines the temperature of a planet), which can result in planets too hot (Venus) or too cold (Mars), and the amount of water present, which could mean a world too wet or too dry. A planet with a higher temperature would probably have a higher proportion of its surface as desert biomes, and possibly also a greater variety of desert biomes than we find on Earth, while a planet with a lower temperature would probably possess a more extensive cryosphere and a large proportion of it surface in arctic biomes. And a planet mostly ocean (i.e., too wet), with extensive island archipelagos, might foster the emergence of a vigorous seafaring civilization, or it might result in the civilizational equivalent of insular dwarfism. Again, we don’t yet know the parameters the values of these variables can take and still be consistent with the emergence of civilization, but to formulate the question is to contribute to the research agenda.

I think it is likely that we will someday be able to reduce to most significant variables to a small number — perhaps two, size and insolation, much as the two crucial variables for determining a biome are temperature and rainfall — and a variety of qualitatively distinct civilizations will be seen to emerge from variations to these variables — again, as in a wide variety of biomes that emerge from changes in temperature and rainfall. And, again, like ecology, we will probably begin with a haphazard system of taxonomy, as today we have several different taxonomies of biomes.

Civilizations (i.e., civilizations of planetary endemism during the Stelliferous Era) supervene upon biospheres, and a biosphere is a biome writ large. We can study the many terrestrial biomes found in the terrestrial biosphere, but we do not yet have a variety of biospheres to study. When we are able to study a variety of distinct biospheres, we will, of course, in the spirit of science, want to produce a taxonomy of biospheres. With a taxonomy of biospheres, we will be more than half way to a taxonomy of civilizations, and in this way astrobiology is immediately relevant to the study of civilization.

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Planetary Endemism

● Civilizations of Planetary Endemism: Introduction (forthcoming)

● Civilizations of Planetary Endemism: Part I

● Civilizations of Planetary Endemism: Part II

● Civilizations of Planetary Endemism: Part III

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Civilizations of Planetary Endemism, Part II

Thursday

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This artist’s impression shows a sunset seen from the super-Earth Gliese 667 Cc. The brightest star in the sky is the red dwarf Gliese 667 C, which is part of a triple star system. The other two more distant stars, Gliese 667 A and B appear in the sky also to the right. Astronomers have estimated that there are tens of billions of such rocky worlds orbiting faint red dwarf stars in the Milky Way alone. (Credit: ESO/L. Calçada)

When I wrote Civilizations of Planetary Endemism I didn’t call it “Part I” because I didn’t realize that I would need to write a Part II, but my recent post on Night Side Detection of M Dwarf Civilizations made me realize that my earlier post on planetary endemism, and specifically using planetary endemism as the basis for a taxonomy of civilizations during the Stelliferous Era, was only one side of a coin, and that the other side of the same coin remains to be examined.

As we saw in Civilizations of Planetary Endemism, during the Stelliferous Era emergent complexities arise on planetary surfaces, which are “Goldilocks” zones not only for liquid water, but also for energy flows. As a consequence, civilizations begin on planetary surfaces, and this entails certain observation selection effects for the worldview of civilizations. In other words, civilizations are shaped by planetary endemism.

One aspect of planetary endemism is temporal, or developmental; this is the aspect of planetary endemism I explored in the first part of Civilizations of Planetary Endemism. Another aspect of planetary endemism is spatial, or structural. The developmental taxonomy of civilizations in my previous post — Nascent Civilization, Developing Sub-planetary Civilization, Arrested Sub-planetary Civilization, Developing Planetary Civilization, and Arrested Planetary Civilization — took account of the spatial consequences of planetary endemism, but in a purely generic way. The spatial limitation of a planetary surface supplies the crucial distinction between planetary and sub-planetary civilizations, while the temporal dimension supplies the crucial distinction between civilizations still developing, and which may therefore transcend their present limitations, and civilizations that have stagnated (and therefore will produce no further taxonomic divisions).

My post on Night Side Detection of M Dwarf Civilizations suggested an approach to planetary endemism in which the spatial constraint enters into a civilizational taxonomy as more than merely the generic constraint of limited planetary surface area. In that post I discussed some properties that would distinctively characterize civilizations emergent on planetary systems of M dwarf stars. In some cases we can derive the likely properties of a civilization from the properties of the planet on which that civilization supervenes. This is essentially a taxonomic idea.

The idea is quite simple, and it is this: different kinds of planets, in different kinds of planetary systems (presumably predicated upon different kinds of stars, and of different kinds of protoplanetary disks that were the precursors to planetary systems), result in different kinds of civilizations supervening upon these different kinds of planets. Given this idea, a taxonomy of civilizations would follow from a taxonomy of planets and of planetary systems.

What kinds of planets are there, and what kinds of planetary systems are there? It is only in the past few years that science has begun to answer this question in earnest, as we have begun to discover and classify exoplanets and exoplanetary systems, as the result of the Kepler mission. This is a work in progress, and we can literally expect to continue to add to our knowledge of planets and planetary systems for hundreds of years to come. We are still in a stage of knowledge where classifications for kinds of planets are emerging spontaneously from unexpected observations, such as “hot Jupiters” — large gas giants orbiting close to their parent stars — and we do not yet have anything like a systematic taxonomy yet.

Since we want to focus on peer life, however, i.e., life as we know it, more or less, this narrows the kinds of planets of interest to far fewer candidates, though ultimately we will need to account for the planetary system context of these habitable exoplanets, and in so doing we will have to take account of all types of planets. There has been a significant amount of attention given to habitable planets around M dwarf stars (one of the reasons I wrote Night Side Detection of M Dwarf Civilizations), which are interesting partly because there are so many M dwarf stars. We can derive interesting consequences for habitable planets around M dwarf stars, such as their being tidally locked, though we have to break this down further according to the size of the planet (since gravity will have an important influence on civilization), the presence of plate tectonics (as a tidally locked planet with active plate tectonics would be a very different place from such a planet without plate tectonics), the strength of the planet’s electrical field, and so on.

Other kinds of planets that have come to attention are “super-Earths,” which are rocky, habitable planets, but larger than Earth, and therefore with a higher surface gravity (therefore with a greater barrier to the transition to spacefaring civilization). The observation selection effects of the transit method employed by the Kepler mission favor larger planets, so the Kepler data sets have not inspired much thinking about smaller planets, but we know from our own planetary system with the smaller Earth twin of Venus, which is too hot, and the smaller yet Earth twin Mars, which is too cold, that the habitable zone of a star can host several Earth-size and smaller planets. When some future science mission makes it possible to survey exoplanetary systems inclusive of smaller worlds, I suspect we will discover a great many of them, and this will generate more questions, like the ability of a smaller planet to maintain its atmosphere and its electrical field, etc.

One way to produce a planetary taxonomy for the civilizations of planetary endemism would be to take Earth as the “standard” inhabitable planet, and to treat all planets inhabited by peer life as departing from the terrestrial norm. We already do this when we speak of Earth twins and super-Earths, but this could be done more systematically and schematically. This, however, does not take into account the parent star or planetary system, so we would have to take our entire planetary system as the “standard” inhabitable planetary system, and work outward from that based on deviations from this norm.

The above is only to suggest the complex taxonomic possibilities for civilizations based on the kind of planet where a civilization originates. I don’t yet have even a schematic breakdown such as I formulated in my previous post on planetary endemism. The variety of planetary conditions where civilizations may arise may be so diverse that it defeats the purpose of a taxonomy, as each individual civilization would have to be approached not as exemplifying a kind, but as something unprecedented in every instance. Still, the scientific mind wants to put its observations in a rational order, so that some of us will always to trying to find order in apparent chaos.

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Kepler Orrery III animation of planetary systems (also see Kepler Orrery III at NASA)

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Civilizations of Planetary Endemism, Part I

Saturday

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During the Stelliferous Era planetary surfaces are uniquely suited for emergent complexity such as life and civilization. Planetary surfaces are by their nature complex, being the interface between planet and planetary atmosphere. Planetary surfaces are moreover a “Goldilocks” zone for energy flows during the Stelliferous Era; energy flows on stars themselves are too great for life, while energy flows in space (in the clouds of gas and dust that surround a star) are too little for life. Planetary surfaces, then, provide “just right” energy flows at the interface of atmospheric gases and the minerals constituting the planet. If emergent complexity is going to arise during the Stelliferous, it is going arise here, hence civilizations begin on planets.

That civilizations begin on planets during the Stelliferous Era has certain consequences. Civilizations originate at the bottom of a gravity well, and if they are to expand beyond a planetary surface, they must reach a level of technological sophistication adequate to lift off from its homeworld a demographically significant proportion of its population of the intelligent organism upon which the civilization supervenes. This is the first and the most significant of the horizons of spacefaring civilization, and the spacefaring horizon that provides the initial overview effect of the civilization’s homeworld.

What this means is that there is thus a natural tendency to planetary endemism among civilizations of the Stelliferous Era. In my posts on planetary constraints I outlined the limitations imposed upon a civilization the development of which is limited to the surface of a planet. These constraints include: 1. the spatial constraint, 2. the temporal constraint, 3. the gravitational constraint, 4. the agrarian constraint, 5. the population constraint, 6. the energy constraint, 7. the material constraint, 8. the ontic constraint, and 9. the endemic constraint. These constraints define the scope of the civilizations of planetary endemism.

A planetary civilization is the limit (and, some might argue, the telos) of planetary endemism. Let us define a planetary civilization as a single civilization uniquely determined by the biosphere of a single planet, which means that, for planetary civilizations, there is a one-to-one correspondence between civilizations and their homeworlds. (Here “planet” is to be understood in the broadest possible sense, including dwarf planets, moons, and so on.) In my post Origins of Globalization I argued that terrestrial civilization today is a planetary civilization (and I further commented on this in Civilization and Uniformity).

In the particular case of terrestrial civilization, a single planetary civilization has emerged from the concrescence of multiple civilizations formerly geographically isolated. Once we think of civilization in this schematic and formal way, at least some alternatives to the particular pattern of terrestrial development become obvious. For example, civilization might begin at a single geographical locus on a planet, and spread outward from there, rather than originating independently on multiple occasions. Even given these alternative pathways to planetary civilization, from the most formal perspective these are variations on a theme of planetary civilization, and the big picture distinctions we can make, and which we can expect to be exemplified in the case of other civilizations (if there are other civilizations), can be narrowed to a few classes. If we think of planetary civilization as a classification in a developmental account of civilization, other classifications naturally grow out of this idea. For example:

● Nascent Civilization What I have also called proto-civilization, are cultures on the verge of producing civilization, i.e., intelligent species at a level of social organization immediately anterior to the threshold of civilization. The Human World of the Upper Paleolithic frequently approximated nascent civilization.

● Developing Sub-planetary Civilization Before a civilization or civilizations reach their planetary limit, they may be called sub-planetary. A sub-planetary civilization still undergoing development, and retaining the capability to expanding to its planetary limit, is a developing sub-planetary civilization. As noted above, developing sub-planetary civilizations may be one or many prior to converging upon a planetary civilization.

● Arrested Sub-planetary Civilization A less-than-planetary civilization that has ceased in its development and so no longer retains the capability of expanding to its planetary limit may be called an arrested sub-planetary civilization. Arrested sub-planetary civilizations, which constitute instances of suboptimal civilization, and will eventually become extinct when planetary conditions eventually change beyond the ability of the civilization to adapt. A sub-planetary civilization is, by definition, a geographically regional civilization, so it is a civilization predicated upon the ecological conditions of a particular region of a planet, and is probably limited to inhabiting one or two biomes of its homeworld. This makes an arrested sub-planetary civilization especially vulnerable to extinction, and, in fact, many local civilizations in terrestrial history have gone extinct leaving no successor civilization (e.g., Minoan civilization, Nazca civilization, etc.).

● Developing Planetary Civilization A civilization that has reached the limits of its homeworld, and yet continues in its development, is a planetary civilization on the cusp of making the transition to becoming a spacefaring civilization. While such development might be cut short by the realization of some existential risk, there is nevertheless a distinction to be made between a planetary civilization in possession of the resources (potentially) to make the transition to spacefaring civilization, and a civilization that happens to reach the limits of its homeworld, but which has no hope of making the transition to spacefaring civilization.

● Arrested Planetary Civilization Arrested planetary civilizations, like arrested sub-planetary civilizations, are also a species of suboptimal civilization, and are also subject to inevitable extinction. However, arrested planetary civilizations are somewhat less vulnerable and more robust than arrested sub-planetary civilizations, since the ability to establish a planetary civilization means that transportation and communication networks unify the homeworld and the civilization in possession of such an infrastructure can compensate for regional ecological changes that could mean the end for a geographically regional civilization. Thus, in general, it is to be expected that arrested planetary civilizations can endure for a longer period of time than arrested sub-planetary civilizations, though a planetary civilization is, in turn, likely to endure for a shorter period of time than a spacefaring civilization, which latter possesses access to far greater resources and can achieve redundancy on a scale than no planetary civilization can achieve.

It is interesting to observe that a sub-planetary civilization might seek existential risk mitigation through redundancy by “seeding” copies of itself in different regions of its homeworld. How would we distinguish between such a project and more familiar categories of civilizational expansion or colonization? I will not attempt to answer this question at present. However, I will make the further observation that this approach to redundancy is closed off to any planetary civilization, whether arrested or still in the process of development.

Several of the terms I have employed here are admittedly rather awkward; my point is to try to capture the most general, “big picture” features of a civilization as we might observe its development from outside. For if SETI, in any of its forms, is eventually successful, we will be scientists of civilization looking from the outside in, and if there are many civilizations to be discovered, they will be roughly sortable into a handful of varieties. The varieties of civilization outlined above are based on the root idea of a planetary civilization, which is in turn based on the idea of the planetary endemism of civilizations, which is likely to be a feature of the Stellierous Era.

The argument implied in the above classification is that this classification possesses a certain conceptual naturalness as a consequence of its being rooted in structural features of the universe in which we happen to find ourselves. A different universe, or a different kind of universe, or a universe with a different natural history, might demand a scheme for the classification of any civilizations it hosted which differed from the above, which is an artifact of particular conditions. Thus if we depart sufficiently from the Stellierous Era, a different taxonomy for the classification of civilization may be necessary. For example, in the case of Degenerate Era civilizations, which would probably consist of civilizations descended with modification from civilizations of the Stellierous Era, the above scheme of classification would not likely be very helpful.

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