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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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biosphere 0

In Rational Reconstructions of Time I noted that stellar evolution takes place on a scale of time many orders of magnitude greater than the human scale of time, but that we are able to reconstruct stellar evolution by looking into the cosmos and, among the billions of stars we can see, picking out examples of stars in various stages of their evolution and sequencing these stages in a kind of astrophysical seriation. Similarly, the geology of Earth takes place on a scale of time many orders of magnitude removed from human scales of time, but we have been able to reconstruct the history of our planet through a careful study of those traces of evidence not wiped away by subsequent geological processes. Moreover, our growing knowledge of exoplanetary systems is providing a context in which the geological history of Earth can be understood. We are a long way from understanding planet formation and development, but we know much more than we did prior to exoplanet discoveries.

The evolution of a biosphere, like the evolution of stars, takes place at a scale of time many orders of magnitude beyond the human scale of time, and, as with stellar evolution, it is only relatively recently that human beings have been able to reconstruct the history of the biosphere of their homeworld. This began with the emergence of scientific geology in the eighteenth century with the work of James Hutton, and accelerated considerably with the nineteenth century work of Charles Lyell. Scientific paleontology, starting with Cuvier, also contributed significantly to understanding the natural history of the biosphere. A more detailed understanding of biosphere evolution has begun to emerge with the systematic application of the methods of scientific historiography. The use of varve chronology for dating annual glacial deposits, dendrochronology, and the Blytt–Sernander system for dating the layers in peat bogs, date to the late nineteenth century; carbon-14 dating, and other methods based on nuclear science, date to the middle of the twentieth century. The study of ice cores from Antarctica has proved to be especially valuable in reconstruction past climatology and atmosphere composition.

The only way to understand biospheric evolution is through the reconstruction of that evolution on the basis of evidence available to us in the present. This includes the reconstruction of past geology, climatology, oceanography, etc. — all Earth “systems,” as it were — which, together with life, constitute the biosphere. We have been able to reconstruct the history of life on Earth not from fossils alone, but from the structure of our genome, which carries within itself a history. This genetic historiography has pushed back the history of the origins of life through molecular phylogeny to the very earliest living organisms on Earth. For example, in July 2016 Nature Microbiology published “The physiology and habitat of the last universal common ancestor” by Madeline C. Weiss, Filipa L. Sousa, Natalia Mrnjavac, Sinje Neukirchen, Mayo Roettger, Shijulal Nelson-Sathi, and William F. Martin (cf. the popular exposition “LUCA, the Ancestor of All Life on Earth: A new genetic analysis points to hydrothermal vents as the planet’s first habitat” by Dirk Schulze-Makuch; also We’ve been wrong about the origins of life for 90 years by Arunas L. Radzvilavicius) showing that recent work in molecular phylogeny points to ocean floor hydrothermal vents as the likely point of origin for life on Earth.

This earliest history of life on Earth — that terrestrial life that is the most different from life as we know it today — is of great interest to us in reconstructing the history of the biosphere. If life began on Earth from a single hydrothermal vent at the bottom of an ocean, life would have spread outward from that point, the biosphere spreading and also thickening as it worked its way down in the lithosphere and as it eventually floated free in the atmosphere. If, on the other hand, life originated in an Oparin ocean, or on the surface of the land, or in something like Darwin’s “warm little pond” (an idea which might be extended to tidepools and shallows), the process by which the biosphere spread to assume its present form of “planetary scale life” (a phrase employed by David Grinspoon) would be different in each case. If the evolution of planetary scale life is indeed different in each case, it is entirely possible that life on Earth is an outlier not because it is the only life in the universe (the rare Earth hypothesis), but because life of Earth may have arisen by a distinct process, or attained planetary scale by a distinct mechanism, not to be found among other living worlds in the cosmos. We simply do not know at present.

Once life originated at some particular point on Earth’s surface, or deep in the oceans, and it expanded to become planetary scale life, there seems to have been a period of time when life consisted primarily of horizontal gene transfer (a synchronic mechanism of life, as it were), before the mechanisms of species individuation with vertical gene transfer and descent with modification (a diachronic mechanism of life). It is now thought the the last universal common ancestor (LUCA) will only be able to be traced back to this moment of transition in the history of life, but this is an area of active research, and we simply do not yet know how it will play out. But if we could visit many different worlds in the earliest stages of the formation of their respective biospheres, we would be able to track this transition, which may occur differently in different biospheres. Or it may not occur at all, and a given biosphere might remain at the level of microbial life, experiencing little or no further development of emergent complexity, until it ceased to be habitable.

While we can be confident that later emergent complexities must wait for earlier emergent complexities to emerge first, no other biosphere is going to experience the same stages of development as Earth’s biosphere, because the development of the biosphere is a function of a confluence of contingent circumstances. The history of a biosphere is the unique fingerprint of life upon its homeworld. Any other planet will have different gravity, different albedo, different axial tilt, axial precession, orbital eccentricity, and orbital precession, and I have explained elsewhere how these cycles function as speciation pumps. The history of life on Earth has also been shaped by catastrophic events like extraterrestrial impacts and episodes of supervolcano eruptions. It was for reasons such as this that Stephen J. Gould said that life on Earth as we know it is, “…the result of a series of highly contingent events that would not happen again if we could rewind the tape.”

Understanding Earth’s biosphere — the particularities of its origins and the sequence of its development — is only the tip of the iceberg of reconstructing biospheres. Ultimately we will need to understand Earth’s biosphere in the context of any possible biosphere, and to do this we will need to understand the different possibilities for the origins of life and for possible sequences of development. There may be several classes of world constituted exclusively with life in the form of microbial mats. Suggestive of this, Abel Mendez wrote on Twitter, “A habitable planet for microbial life is not necessarily habitable too for complex life such as plants and animals.” I responded to this with, “Eventually we will have a taxonomy of biospheres that will distinguish exclusively microbial worlds from others…” And our taxonomy of biospheres will have to go far beyond this, mapping out typical sequences of development from the origins of life to the emergence of intelligence and civilization, when life begins to take control of its own destiny. On our planet, we call this transition the Anthropocene, but we can see from placing the idea in this astrobiological context that the Anthropocene is a kind of threshold event that could have its parallel in any biosphere productive of an intelligent species that becomes the progenitor of a civilization. Thus planetary scale life is, in the case of the Anthropocene, followed by planetary scale intelligence and planetary scale civilization.

levels of biological organization

Ultimately, our taxonomy of the biosphere must transcend the biosphere and consider circumstellar habitable zones (CHZ) and galactic habitable zones (GHZ). In present biological thought, the biosphere is the top level of biological organization; in astrobiological thought, we must become accustomed to yet higher levels of biological organization. We do not yet know if there has been an exchange of life between the bodies of our planetary system (this has been posited, but not yet proved), in the form of lithopanspermia, but whether or not it is instantiated here, it is likely instantiated in some planetary system somewhere in the cosmos, and in such planetary systems the top level of biological organization will be interplanetary. We can go beyond this as well, positing the possibility of an interstellar level of biological organization, whether by lithopanspermia or by some other mechanism (which could include the technological mechanism of a spacefaring civilization; starships may prove to be the ultimate sweepstakes dispersion vector). Given the possibility of multiple distinct interplanetary and interstellar levels of biological organization, we may be able to formulate taxonomies of CHZs for various planetary systems and GHZs for various galaxies.

One can imagine some future interstellar probe that, upon arrival at a planetary system, or at a planet known to possess a biosphere (something we would know long before we arrived), would immediately gather as many microorganisms as possible, perhaps simply by sampling the atmosphere or oceans, and then run the genetic code of these organisms through an onboard supercomputer, and, within hours, or at most days, of arrival, much of the history of the biosphere of that planet would be known through molecular phylogeny. A full understanding of the biospheric evolution (or CHZ evolution) would have to await coring samples from the lithosphere and cryosphere of the planet or planets, and, but the time we have the technology to organize such an endeavor, this may be possible as well. At an ever further future reach of technology, an intergalactic probe arriving at another galaxy might disperse further probes to scatter throughout the galaxy in order to determine if there is any galactic level biological organization.

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Darwin’s Cosmology

12 February 2012


Today is Darwin’s birthday, and therefore an appropriate time to celebrate Darwin by a mediation upon his work. No one has influenced me more than Darwin, and I always find the study of his works to be intellectually rewarding. I also read (and listen to) quite a number of books about Darwin. Recently I listened to Darwin, Darwinism, and the Modern World, 14 lectures by Dr. Chandak Sengoopta. While I enjoyed the lectures, I sharply differed from many of Dr. Sengoopta’s interpretations of Darwin’s thought. One theme that Dr. Sengoopta returned to several times was a denial that Darwin had anything to say about the ultimate origins of life. Each time that Dr. Sengoopta made this point I found myself grow more and more irritated.

To say that Darwin had nothing to say about the ultimate origins of life may be technically correct in a narrow sense, but I do not think that it is an accurate expression of Darwin’s vision of life, which was sweeping and comprehensive. While it may be a little much to say that Darwin ever entertained ideas that could accurately be called “Darwin’s cosmology,” it is obvious in reading Darwin’s notebooks, in which he recorded thoughts that never made it into his published books, his mind ranged far and wide. It is almost as though, once Darwin made the conceptual breakthrough of natural selection he had discovered a new world.

In characterizing Darwin’s thought in this way I am immediately reminded of a famous letter that Janos Bolyai wrote to his father after having independently arrived at the idea of non-Euclidean geometry:

“…I have discovered such wonderful things that I was amazed, and it would be an everlasting piece of bad fortune if they were lost. When you, my dear Father, see them, you will understand; at present I can say nothing except this: that out of nothing I have created a strange new universe. All that I have sent you previously is like a house of cards in comparison with a tower. I am no less convinced that these discoveries will bring me honor than I would be if they were complete.”

Darwin, too, discovered wonderful things and created the strange new universe of evolutionary biology, though it came on him rather slowly — not in a youthful moment that could be recorded to a letter in his father, and not in a fit of fever, as the idea of natural selection came to Wallace — as the result of many years of ruminating on his observations. But the slowness with which Darwin’s mind worked was repaid with thoroughness. Even though Darwin was the first evolutionist in the modern sense of the term, he must also be accounted among the most complete of all evolutionary thinkers, having spent decades thinking through his idea with a Platonic will to follow the argument wherever it leads.

Given that Darwin himself thought that making the idea of natural selection public was like “confessing to a murder,” the fragments of Darwin’s cosmology must be sought in his latter and notebooks as much as in his published works. As for the origins of life, narrowly considered, apart from the cosmological implications of life, Darwin openly speculated on a purely naturalistic origin of life in a letter to Joseph Hooker:

“It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, — light, heat, electricity &c. present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter would be instantly devoured, or absorbed, which would not have been the case before living creatures were formed.”

Darwin’s 1871 letter to Joseph Hooker

What has widely come to be known as “Darwin’s warm little pond” sounds like nothing so much as the famous Stanley L. Miller electrical discharge experiment.

Darwin revealed his consistent naturalism in his rejection of teleology in a letter to Julia Wedgwood, where he indirectly refers to his slow, steady, cumulative mode of thinking (quite the opposite of revelation):

“The mind refuses to look at this universe, being what it is, without having been designed; yet, where would one most expect design, viz. in the structure of a sentient being, the more I think on the subject, the less I can see proof of design.”

Darwin’s letter of 11 July 1861 to Miss Julia Wedgwood

This same refusal continues to a sticking point to the present day, since, like so much that we learn from contemporary science, appearances are deceiving, and the reality behind the appearance can be so alien to the natural constitution of thue human mind that it is rejected as incomprehensible or unthinkable. That Darwin was able to think the unthinkable, and to so with a unparalleled completeness at a time when no one else was doing so, is testimony to the cosmological scope of his thought.

One of the most memorable passages in all of Darwin’s writings is the last page or so of the Origin of Species, which touches not a little on cosmological themes. Take, for instance, the “tangled bank” passage:

“It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.”

Besides anticipating the evolutionary study of ecology and complex adaptive systems long before these disciplines became explicit and constituted their own sciences, Darwin here subtly invokes a law-like naturalism that both suggests Lyell’s uniformitarianism while going beyond it.

Darwin places this law-governed naturalism in cosmological context in the last two sentences of the book, here also implicitly invoking Malthus, whose influence was central to his making the breakthrough to the idea of natural selection:

“Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

This famous passage from Darwin reminds me of a perhaps equally famous passage from Immanuel Kant, who concluded The Critique of Practical Reason with this thought:

“Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry heavens above me and the moral law within me. I do not seek or conjecture either of them as if they were veiled obscurities or extravagances beyond the horizon of my vision; I see them before me and connect them immediately with the consciousness of my existence. The first starts at the place that I occupy in the external world of the senses, and extends the connection in which I stand into the limitless magnitude of worlds upon worlds, systems upon systems, as well as into the boundless times of their periodic motion, their beginning and continuation. The second begins with my invisible self, my personality, and displays to me a world that has true infinity, but which can only be detected through the understanding, and with which . . . I know myself to be in not, as in the first case, merely contingent, but universal and necessary connection. The first perspective of a countless multitude of worlds as it were annihilates my importance as an animal creature, which must give the matter out of which it has grown back to the planet (a mere speck in the cosmos) after it has been (one knows not how) furnished with life-force for a short time.”

Both Darwin and Kant invoke both the laws of the natural world (and both, again, do so by appealing to grandeur of the heavens) and a humanistic ideal. For Kant, the humanistic ideal is morality; for Darwin, the humanistic ideal is beauty, but what Kant said of morality and the moral law is equally applicable, mutatis mutandis, to beauty. Darwin might equally well have said of “the fixed law of gravity” and of “endless forms most beautiful and most wonderful” that he saw them before himself and connected them immediately with the consciousness of his existence. Kant might equally well have said that there is “grandeur in this view of life” that embraces both the starry heavens above and the moral law within.

Darwin did not express himself (and would not have expressed himself) in these philosophical terms; he was a naturalist and a biologist, not a philosopher. But Darwin’s naturalism and biology were so comprehensive to have spanned the universe and to have converged on an entire cosmology — a cosmology, for the most part, not even suspected before Darwin had done his work.

There is a sense in which Darwin fulfilled Marx’s famous pronouncement, from this Theses on Feuerbach, such that: “Philosophers have only interpreted the world in various ways; the point is to change it.” Darwin, however, did not change the world by fomenting a revolution; Darwin changed the world by thinking, like a philosopher. In this sense, at least, Darwin must be counted among the greatest philosophers.

I would be a rewarding project to devote an entire book to the idea of Darwin’s Cosmology. I know that I have not even scratched the surface here, and have not come near to doing justice to the idea. It would be a rewarding project to think through this idea as carefully as Darwin thought through his ideas.

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Happy Birthday Charles Darwin!

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