≡ Menu

The Zen of SETI

The SETI challenge has often been likened to archaeology, and for good reason. In both cases, we are trying to recover information about cultures from the past. When Heinrich Schliemann dug into the numerous layers of Troy — and in the process inadvertently damaged precious remnants of later eras — he and his team were exploring the heroic age of Homer. Any SETI detection will likewise deal with a signal from the past. Just how old it is will depend upon how far away the source world is, for this information travels at the speed of light.

The archaeology analogy is hardly perfect, because on Earth we are dealing with artifacts of our own species and are often working with linguistic remains we can decipher to aid our understanding. Figuring out Egyptian hieroglyphs wasn’t easy, but the stele known as the Rosetta Stone gave us a text in three scripts that helped us make sense of them. Even Linear B, the script of the Mycenaean Greeks before the emergence of the Greek alphabet, can be placed into context as the oldest Greek dialect, apparently borrowed as a script from the Minoan Linear A. But a SETI reception will be pure message, and absent the numerous cultural and linguistic cues we rely on to make sense of an undeciphered language, how will we approach it?


While we have significant problems with some ancient languages — the resolution of Mayan awaited seeing the glyphs in an entirely new context, looking at them phonemically and morphologically, and Etruscan is a challenge to this day — the problems with a genuinely alien message from another star dwarf these issues. Which brings me around to Clément Vidal, who has written a book that digs with gusto into the SETI question by way of asking what kind of detection we may expect to make. What we might call ‘traditional’ SETI by and large supposes that a distant civilization will be trying to get a message to us, for we’re highly unlikely to pick up radio signals not beamed in our direction.

The Beginning and the End (Springer, 2014) is subtitled ‘The Meaning of Life in a Cosmological Perspective,’ and SETI is only one aspect of its tripartite discussion. But its analysis of SETI and its application of a cosmological worldview help us see current SETI efforts as part of a larger picture. The communication assumption is sensible given SETI’s roots and the deliberate decision to look for signals in the most probable part of the spectrum, which early advocates saw as the region between the spectral lines of hydrogen and the hydroxyl radical — between 1420 and 1665 MHz. The ‘water hole’ for communication was quiet and presumably would attract cultures looking for other intelligent beings. But there are other ways to search for life that add valuable tools to our quest.

Vidal is a philosopher and, as his book attests, a polymath who delves into astrobiology, complexity science, cosmology and much else in the course of his discussion. Analyzing the weaknesses of our underlying assumptions is a key part of his argument. He believes we do not need to assume communication to conduct a SETI search, nor do we need to confine our efforts to our own galaxy. Radio methods offer us the hope of one day engaging in a two-way conversation with another species, putting the premium on nearby stars, but what I often call ‘interstellar archaeology’ — the science of looking for ETI in the data, and that data may be spread over numerous galaxies — yields on communications while stressing detection of civilizations that may be far more powerful than our own.

‘Zen SETI’ is the entertaining term Vidal coins for this approach, one that has been championed in recent years by Milan Ćirković, though analyzed by many scientists over the years, from Freeman Dyson to Nikolai Kardashev, James Annis, Richard Carrigan and current working groups like Penn State’s Jason Wright, Matthew Povich and Steinn Sigurðsson. I won’t go through a complete round-up here, but you can find current work discussed in my essay Distant Ruins, which ran in Aeon. The point is to think creatively about information that may already be in our astronomical data, and about new searches that put a premium on the signature that a Kardashev Type II or III civilization would leave.

Needless to say, Zen SETI makes no claim at being the only approach to the discipline, and indeed, these methods should be seen as complementary to ongoing radio and optical searches. When Richard Carrigan went to work searching infrared data from the IRAS satellite for the signature of possible Dyson spheres (see Toward an Interstellar Archaeology), he was broadening the effort to study SETI targets in places as distant as M51, the Whirlpool galaxy, pondering how a Kardashev Type III culture might begin turning stars en masse into a wavefront of such spheres as it maximized its energy resources.


Image: M51, the Whirlpool Galaxy. If a Kardashev Type III culture were active here building Dyson spheres, would we be able to see its signature as a growing void in visible light? Credit: NASA/ESA.

Such a search doesn’t preclude communications from a much closer civilization, but it does ask a thoughtful question. We now peg the age of our universe at roughly 13.7-13.8 billion years. We also think that the oldest Sun-like stars formed as early as about 12.5 billion years ago, with rocky planets beginning to emerge at that time. Give life five billion years to emerge, as it did on Earth, and you have the possibility of the earliest intelligence appearing as early as six billion years after the Big Bang. Because the Milky Way is thought to have formed between 10 and 11 billion years ago, intelligence may have appeared in our galaxy as much as five billion years before we humans began turning radio telescope dishes toward the nearby stars.

Charles Lineweaver (Australian National University) is the go-to guy on these matters, with work showing that on average, Earth-like planets around other stars are 1.8 billion years older than our planet, give or take 0.9 billion years either way. Given Lineweaver’s findings, isn’t it likely that any civilization we do discover is going to be significantly advanced over our own? Milan Ćirković made the case in a 2006 paper:

Applying the Copernican assumption naively, we would expect that correspondingly complex life forms on those others to be on the average 1.8 Gyr older. Intelligent societies, therefore, should also be older than ours by the same amount. In fact, the situation is even worse, since this is just the average value, and it is reasonable to assume that there will be, somewhere in the Galaxy, an inhabitable planet (say) 3 Gyr older than Earth. Since the set of intelligent societies is likely to be dominated by a small number of oldest and most advanced members…we are likely to encounter a civilization actually more ancient than 1.8 Gyr (and probably significantly more).

All of which compels Vidal to argue that the terms of our SETI search must be flexible:

We need not be overcautious in our astrobiological speculations. Quite the contrary, we must push them to their extreme limits if we want to glimpse what such advanced civilizations could look like. Naturally, such an ambitious search should be balanced with considered conclusions. Furthermore, given our total ignorance of such civilizations, it remains wise to encourage and maintain a wide variety of search strategies. A commitment to observation, to the scientific method, and to the most general scientific theories remains our best touchstone.

Paul Davies makes much the same point and is quoted by Vidal as saying that “the universe is a rich and complex arena in which signs of alien intelligence might be buried amid a welter of data from natural processes, and unearthed only after some ingenious sifting.” Tomorrow I want to go further into our SETI assumptions and where they might be challenged, using Clément Vidal’s fine discussion of Zen SETI and its consequences for how we proceed.

The Ćirković paper is “Macroengineering in the Galactic Context” (full text). Charles Lineweaver’s study is “An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect,” Icarus Vol. 151, No. 2 (2001), pp. 307-313 (full text).


Comments on this entry are closed.

  • Mike Jude October 27, 2014, 15:52

    I found your piece in Aeon haunting… It made me think about the notion of motivations for advanced civilizations and perhaps a motivation for ours. What if we decide that the continued presence of human life on Earth is an unacceptable threat to the continued existence of something we hold dear. Would we decide that in order to save the Earth we have to leave it? Would other advanced civilizations make the same choice? Maybe the best reason to go to the stars is to preserve our birth place. Maybe we ought to pitch space exploration as the best solution for saving Earth to those who believe that we are causing global warming, species decline, etc. In other words, give the anti-technology types a reason for embracing technology :-)

  • Paul Gilster October 27, 2014, 15:53

    A great SF story in there, Mike — leaving Earth in order to save it. Fascinating notion.

  • NS October 28, 2014, 0:59

    I always thought that if we could solve the technological and transportation problems it would be good idea to get heavy industry and even agriculture into space, using the Earth mainly for a living area.

    Interesting that the post mentions Lineweaver. He’s actually pessimistic about SETI’s chances, since he sees no sign of a general trend toward intelligence in Earth life and believes human-like intelligence is an accident of evolution that is unlikely to be duplicated elsewhere. He does support SETI efforts though, both because he concedes he could be wrong and because they may discover things that we didn’t anticipate.

  • kamal ali October 28, 2014, 2:10

    any chance we can get charles lineweaver to write an article on CD?
    first, i’m really curious to hear the line of reasoning that most earthlike
    planets are 1.8GY older than us.
    Secondly, if that’s even remotely close to being true, it has huge
    implications for Fermi Paradox because the difference between their
    development (and specially motivations) and us then becomes an unimaginable gulf: the difference between us and protozoa.
    it would explain a lot about the Great Silence and would have the
    possibility of anchoring a lot of future discussions.

  • Anthony Mugan October 28, 2014, 7:42

    A very logical argument.

  • kzb October 28, 2014, 8:27

    Prof Brian Cox (Human Universe -BBC2 TV series currently showing in UK)certainly believes we are unique and there are no other technological civilisations.
    I tend to agree with this position, without being absolutely certain of course.
    Reasons for disagreeing with standard model of Lineweaver et al:
    1) Gamma ray bursts (GRBs) may have made the early universe uninhabitable. Contrary to Lineweaver’s ideas on the GHZ (galactic habitable zone), the outer galaxy has only become habitable quite recently, and the inner galaxy is still hostile to advanced life to this day.
    2) Prokaryotes existed for 2 billion years before eukaryotes evolved. This is a strong argument for the endosymbiosis event being extremely rare in the universe.
    3) Evolution of our kind of intelligence depended on some very specific drivers concerning periodic climate change in the Rift Valley.

  • Paul Gilster October 28, 2014, 9:10

    kamal ali writes:

    any chance we can get charles lineweaver to write an article on CD?

    Sounds good to me, Kamal, and I’ll explore the possibility!

  • Eniac October 28, 2014, 9:44


    1) Gamma ray bursts (GRBs) may have made the early universe uninhabitable. Contrary to Lineweaver’s ideas on the GHZ (galactic habitable zone), the outer galaxy has only become habitable quite recently, and the inner galaxy is still hostile to advanced life to this day.

    Given that GRBs are effectively shielded by an atmosphere, and even more effectively by an ocean and crust, they should not be expected to have, or ever have had, any bearing on habitability to life.

    2) Prokaryotes existed for 2 billion years before eukaryotes evolved. This is a strong argument for the endosymbiosis event being extremely rare in the universe.

    Endosymbiosis is common in the history of life, chloroplasts and mitochondria are just two different examples. Sudden spurts in evolution are also common, see the Cambrian explosion or the colonization of land as different examples.

    3) Evolution of our kind of intelligence depended on some very specific drivers concerning periodic climate change in the Rift Valley.

    This is pure speculation. Climate change is common and there is no real clue what this “specific” rare driver might be, nor that one exists.

  • Eniac October 28, 2014, 9:59

    That said, I still agree with Lineweaver (and Davies, too, I believe) that intelligent life is rare or absent, simply based on the evidence. Givent the deep time noted in this article, available for life to spread everywhere, the fact that we have not observed alien life around us can only mean two things:

    1) Life does not spread between stars, or
    2) There is no other life.

    From what we know about our own form of life, we can be fairly confident (or at least hopeful) that #1 is false, which leaves #2 ….

    The culprit for that, in my opinion, is the rarity of spontaneous abiogenesis, but there are, of course, other possibilities.

  • Craig Watkins October 28, 2014, 12:01

    I do think that 2 billion years to produce eukaryotic life is a sign that it is probably rare in the universe, but not necessarily that it is a rare event. Once established, Prokaryotic life seems almost indestructible so I expect it to have an unimaginable amount of opportunities to evolve.

    Human intelligence is unique, but is it more unique than say the land speed of a cheetah? Compared to the intelligence of a worm, human intelligence is only a minor adaptation over ape intelligence and intelligence of that level seems to show up frequently enough through convergent evolution.

    Humans had a unique convergence of traits that led to the development of extreme intelligence, but taken individually – opposable thumbs, two legged locomotion, tool creation, shared cultural knowledge, large brain size all appear elsewhere. The earliest of humans, while seemingly primed to make the leap to sapiens et al, were not particularly notable as animals.

    From our perspective, it’s still really hard to see if we are incredible snowflakes or simply the result of inevitable processes. At this point, I tend to believe that sheer distance, lack of motivation, and lifespan of civilizations are the critical factors that answer the Fermi paradox.

  • Brian October 28, 2014, 13:27

    I have a question about the Fermi paradox, if some galactic civilization existed and they communicated with say lasers or something other than radio waves, could tell from earth? can our telescopes see something like that? I ask because I want to understand if the paradox is simply being us not able to see what is going on or something more.

  • kzb October 28, 2014, 14:36

    Eniac: it’s not the direct gamma radiation from a GRB that is the problem. It is the destruction of the ozone layer. This wipes out the base of the food chain (photosynthetic organisms on land and sea). This causes the evolutionary clock to be re-set back to primitive organisms.

    The other two reasons are direct from Prof. Cox himself. The endosymbiosis event is said to be unique, because ALL eukaryotic life (plant and animal) is descended from ONE original cell (I can only think that chloroplasts were taken in later, by a descendant of the original archea and oxygen-using bacterium symbiotic organism).

    The specific climate change reason is the effect on the Rift Valley climate of 400,000 year periodicity in the ellipticity of Earth’s orbit. Step changes in hominid brain capacity occured in step with this 400,000 year cycle.

  • RobFlores October 28, 2014, 15:59

    C, Watkins “Prokaryotic life seems almost indestructible”

    I don’t think this is much help, and I think a nascent biosphere can be smothered by an event well enough so that those advanced micro-organisms, will be face stasis and/or long decay afterwards.

    Even just before the trinity Test in the dessert and the advent of rockets, we were as vulnerable as any fauna on the Earth to cataclysmic events, that’s
    4 billion years of evolution, put in the trash bin and never to rise again.

    Mars is I believe a textbook case. We may find some microorganisms, but Mars is a dead end, and I am not convinced it need have been that way, but for the gigantic impactor that devastated 1/2 it’s surface, and probably pushed a great part of it’s atmosphere into space.

    Within any Drake Like Equation, there needs to be more emphasis on hazards variable . I think we some pretty good candidates to include in there.

    Additionally I’d like to restate what has been said here a few times.
    If life did arise 5 billions years ago. and say colonized a galaxy. What
    would be the impetus to travel to another one? There would be enough
    Energy and Mass in that galaxy, to create an incredibly detailed simulation
    of another galaxy, or parts thereof. You would not need to travel, once
    you understand the Pillars of Evolution (and they would wouldn’t they) you
    could watch simulation unfold, and more interesting you could control its speed so your don’t have to wait 1 billion years real time for some microbe to
    turn into a higher life form.

  • Eniac October 28, 2014, 19:29


    It is the destruction of the ozone layer. This wipes out the base of the food chain (photosynthetic organisms on land and sea).

    It does no such thing. It increases the UV radiation level somewhat at the surface, but nothing that life could not adapt to. By staying in the ocean, most drastically, but not exclusively. Redder stars will have less UV to begin with, so for the vast majority of stars this is even less of a problem.

    Lastly, there is no real evidence that a GRB would destroy the ozone layer at all, it may just as well enhance it, for all we know.

  • Eniac October 28, 2014, 19:35


    because ALL eukaryotic life (plant and animal) is descended from ONE original cell

    This, also, is nothing special. All of today’s life (including prokaryotes and archaea) descends from one original organism (LUCA). All humans descend from one original male, and one original female (mitochondrial Eve and X chromosomal Adam). It is a mathematical property of any phylogeny in limited populations, and proves nothing about biology or evolution.

  • Rob Henry October 28, 2014, 21:59

    So many questions here and so few answers to give.

    Firstly, I would like question whether the human level of intelligence is truely unique even on Earth. It continues to bother me that any large analysis of a sperm whales simplest coda (or word) taken from a single pod tends to break down into about a hundred discrete variants. This would extrapolate a normal vocabulary (where 95% of it consists of about 20 coda types) as more complex than a human language – which seems to be currently dismissed as an absurdity. But is it? If you Wikipedia ‘fertilization of the oceans’ only one species is given significant and it ain’t humans. We assume they are doing it by dumb luck… okay enough already, but I have many other reasons for believing it possible that this one species, to the exclusion of all other cetaceans might be our intellectual equals.

    Secondly lithopanspermia looks fairly likely to have spread bacterial life between Mars and Earth. That would make Mars the ideal laboratory to test if the major leaps in evolutionary complexity of the highest forms are the product of time and luck, or more by biogeochemical conditions. Particularly interesting would be the possible facilitative effect of O2 levels.

    Thirdly, another reason to leave (sections) of Earth is to restore it (and because many would pay a fortune to see a real ‘Jurassic Park’ even if it was from afar, or behind perspex). In my New Zealand we have copious supplies of DNA of the megafauna we so very recently drove to extinction. Moa might be dangerously aggressive if Australia’s cassowary is anything to go by, but de-extincting the Haast’s eagle would present other problems. How do humans fence themselves off from raptors whose normal prey might well have been quarter ton bipeds (there is much evidence in favour of that possibility including fossils of attacked Moa and Maori legends of a bird that could take down people).

  • NS October 28, 2014, 23:44

    To Brian, besides a number of radio telescope searches there are a few current projects to detect lasers (optical SETI). There have also been examinations of astronomical data from other (non-SETI) projects for lasers, Dyson Spheres, and gamma rays from anti-matter burning engines. Probably others that I haven’t heard of or forgotten about! There are a lot more links than the ones below:


  • NS October 29, 2014, 4:00

    On the issue of the rarity (or not) of abiogenesis, evidence about it will be found when we can investigate other worlds to see if life originated independently on them. But Lineweaver among others suggests investigating here on Earth for life that may have arisen independently of known life. If present it would indicate that abiogenesis may at least be less rare:


  • Anthony Mugan October 29, 2014, 7:03

    I largely agree with the comments above by Eniac (although curiously, perhaps due to a couple of additional factors, I come to a somewhat different conclusion).

    Without repeating too much of the discussion above, and in addition to it:

    The only thing we can say with certainty about the probability of life appearing on a specific planet, evolving multicellular life forms and the eventual appearance of a technological civilisation is that the probability is not zero (as we exist).
    The significance of the developments of our knowledge of the number, distribution and ages of exoplanets in recent years is profound. We are still at an early stage of this particular journey but we can safely conclude that number of potentially habitable planets (and exo-moons) is well into the billions per galaxy.
    At the same time our appreciation of the availability of deep time has improved. We now know that rocky planets have been around for a very long time indeed. The sheer scale of the time available is hard even for those of use used to thinking in astronomical (or geological in my case) time scales to truly grasp.

    When you plug a non-zero probability of the emergence of a technological civilisation into an available number of trials (potential habitats * time) that is literally astronomical you end up with a situation in which it exceptionally unlikely that we are the first technological civilisation. It is of course perfectly possible that these could be rare and far apart. All of which begs the question of where are they?

    I agree to an extent with Eniac – I doubt if the technological barrier to interstellar travel is the fundamental block.
    I would also agree to an extent that there may be a basic error in the common assumptions regarding the emergence of life being not too difficult (but again we know the probability is not zero, so we are back with the same problem, given the phenomenal number of potential trials…where are they).
    We may of course have considerable difficulty in imagining how a civilisation a billion years ahead of us may be operating and that could well be a decisive factor. We tend to assume that we are quite close to a final Theory of Everything, but that could well be a touch optimistic. It would only take one or two paradigm shifts in physics over the next goodness knows how many million years to make such an advanced civilisation really beyond what we can imagine at the moment (leaving aside the problem of cultural differences).

    More generally I do feel that this sort of discussion highlights the need to get to the bottom of two current theories that are relevant to this discussion.
    a) Convergent evolution (really the application of complexity to evolution).
    b) Panspermia

    Panspermia in particular strikes me as amenable to direct testing – and to a substantial extent already has been successfully tested – but with some room for doubt remaining, particularly over interstellar distances.

    If either of these hypotheses can be firmly established then life should be very widespread indeed, and given the way each impacts on evolution, intelligent life also. If both were to be falsified then it would seem more credible to me that intelligent life on this planet could just be an exceptionally unlikely event. But to be the first… that is fine tuning on a cosmological scale that is so extreme I really do struggle with the basic idea of it.

  • kzb October 29, 2014, 8:37

    Brian -yes you are right, there are many good reasons why the galaxy could be alive with ET civilisations, but we don’t observe radio waves from them. Radio communication could be very much a passing phase.

    The REAL Fermi paradox is not this, it is why the Earth was not colonised long before we evolved. It’s a bigger problem than simply not picking up anything from SETI.

    The Ćirković paper linked in the main article includes a scathing criticism of SET concepts as it happens.

  • Etienne October 29, 2014, 15:59

    Thank you for this perspective over our possible two billion years old predecessors. I remember a beautiful excerpt from Robert Zubrin’s “Entering space” last chapter. Indeed, mankind may be a “newborn, awakening in the early dawn of the first day of the cosmic spring”. Here is the full sentence: “This fact, that Mind has not yet, at least in any large or apparent way, created something else fundamentally new in the universe, or substantially affected its development, suggests to me that Mind is still immature; that intelligence, while no doubt existing in innumerable locations, has just begun to extend itself outwards to link itself together on a cosmic scale. We have not yet met ET and ET has not yet met us. Could we be the only people out of the loop? Not likely. Rather, it seems to me more probable that the galactic club has yet to get itself organized and everybody connected. And the intergalactic club no doubt has even further to go. Life’s children are newborns, awakening in the early dawn of the first day of the cosmic spring. It will be a while before we all meet.

  • Rob Henry October 29, 2014, 18:46

    Anthony Mugan wrote

    “The only thing we can say with certainty about the probability of life appearing on a specific planet, evolving multicellular life forms and the eventual appearance of a technological civilisation is that the probability is not zero (as we exist).”

    But not even that premise sufficient to the conclusion. The chance may be infinitesimal (ie closer to zero than any number that can be stated) and so exactly equal to zero to any non-mathematician. Even if we combine it with the Copernican principle to allow ourselves a reasonable chance of existence then, under certain conditions of panspermia under the (currently unpopular) steady state theory we can magnify a unique occurrence infinitely, and so still avoid the conclusion.

    True, the popular assumption might well be that were their is water, energy flow, and time, then life will spring up, but we have three powerful and independent reasons to believe otherwise.

    1) For more than two thousand years natural philosophers have debated whether lines of living creatures evolve over time into other more complex forms. Charles Darwin principle of ‘natural selection’ changed that indecision almost overnight. Many today forget that the modern idea of evolution is that NO new biologically useful function can arise EXCEPT by slight modification of a pre-existing one. Abiogenesis was always a problem to modern biology, no matter how simple that form was assumed to be. The ultimate proof of Darwin’s theory came when all life on Earth was shown to have a common origin.

    2) When we look at the complexity of our last universal ancestor we find that it is stunning. It seems highly improbable that, even in the simplest and most sheltered niches, primitive organisms were all outcompeted by far more complex and later forms that all haled from a single line (rather like primates one day evolving into forms that outcompete to extinction all other forms including bacteria)

    3) When we study the simplest non-trivial reproductive forms in cellular automaton designed to facilitate that purpose, even there, the design of the minimal life form seems impossibly complex. In fact so complex that von Neumann couldn’t do it, and had to be content to merely prove that it was possible (even that was no mean feat)

    As to evolution to higher forms, independent lines seem to do that on Earth, even if computer simulations paralleling the process do not (or quickly reach an asymptotic limit). Until we know why there is that discrepancy I cant see how we would estimate the chances elsewhere. My guess is that it would be very high, perhaps even so high that few living planets that have a receptive surface environment for billions of years do not produce it.

  • Eniac October 29, 2014, 19:45

    Anthony Mugan has given a wonderful elaboration on some of the critical ideas, here. To this I would just like to add that non-zero is not the same as “large”, or “significant” by any means.

    Because of our biased position (If there was only one inhabited world in the universe, we necessarily would have to be on it. If there wasn’t any, we would not be in this universe at all), in fact, the non-zero observation has no information value at all. In other words, the probability of us observing the existence of life is 1, exactly, which means the information content of that observation is zero, exactly.

    In my opinion the best estimate we can make of the rate of abiogenesis is r ~ 1 / (number of habitable planets in the universe)*(time passed since the first such planets existed). In other words, the size of the universe follows the chance of abiogenesis, not vice versa. If we lived in a much smaller universe, our very existence would be extremely unlikely, which is why we don’t.

    Unfortunately, from this admittedly more philosophical than logical argument it would follow that there really is only one instance of life in the galaxy, and in this universe, to boot. The former we have evidence for in the Fermi paradox, the latter is pure inference.

  • Anthony Mugan October 30, 2014, 5:24

    NS noted that a major puzzle of the Fermi paradox is that earth was not colonised two billion years ago….
    I hesitate to even suggest the possibilities ( and would note that on balance I don’t these are likely at this time)…
    Crick argues for directed panspermia, which in a sense would be a very ‘hands off’ form of colonisation…but I don’t see what the point would have been.
    I do sometimes wonder if Douglas Adams was closer to the mark than he could have ever imagined. As noted above it took a long time for complexity to begin to build in the biosphere…roughly coinciding with the timelines we are discussing…
    Now I really am in SF mode…but it really would be entertaining to meet Benji mouse (not to mention the meat!).

    More seriously it may be quite hard for us to really anticipate the motivations of a truly alien ETC, hence my interest in strategies that go are not to focused on what we’d do now or in the near future

  • Wojciech J October 30, 2014, 6:17

    Moving heavy industry and agricultural offworld once the cost of doing is so is low enough seems a good idea. I recall it being discussed by Kim Stanley Robinson and Stanislaw Lem. One thing that strikes me from the idea of life being billions of years advanced from our own is that any potential intelligent starfaring civilization would know of Earth’s existence since millions if not billions of years, and thus the worries of some of the thinkers about contacting alien life are unfounded.

    Another thing is, that such advanced civilization would be far beyond what we can imagine technologically. Dyson Spheres are fine and interesting, and I would speculate such mega-engineering projects could be undertaken by some civilizations, HOWEVER, these are concepts and ideas that we can imagine TODAY. Speculating I can imagine our civilization being able to undertake such projects maybe in 500 or 1000 years. But what about million or billion years? By then they would probably be laughable to us, unless there is some limit to technological advancement(although I have doubts Dyson Spheres are within this limit). Perhaps creation of artificial dimensions, alternate universes would be something these civilizations would engage in? But this is highly speculative.

    As to life spreading-this is the trait of life, but not necesarrily of intelligent life which is capable to of self-awareness and setting itself limits to what it is movitated to do by biology. We already have natural parks and protected areas. And we already as civilization withdraw from colonization of several natural areas such as Antarctica or Pacific Islands where settlements were simpl abandonded. It is not unlikely that an advanced civilization would decide to leave natural biospheres and early civilizations untouched to allow them to develop in their own unique way, without intereference.

  • ljk October 30, 2014, 10:35

    Will it be difficult or even impossible to set up permanent space colonies for organic beings due to all that cosmic radiation? Does this mean other organic ETI that wanted to colonize the galaxy have also run into the same problems?


    Maybe we’re just a passing phase anyway:


    Add to the news above science spokesman and former rock star Brian Cox declaring there are no aliens and Sten Odenwald declares interstellar travel to be impractical. Throw in ebola and increasingly nasty terrorists threatening the civilized world and we may soon discover the values of L and N on the Drake Equation at least for the residents of Earth.

    Well at least Pope Francis I says it is okay to “believe” in evolution and the Big Bang, though he is not the first pontiff to support these concepts (they are not a belief system).


    The Roman Catholic Church has also said it is okay to “believe” in aliens for decades now, just in case you were wondering or had not caught up on such things.


    And speaking of aliens and human reactions to them, it is the 75th anniversary of the War of the Worlds radio broadcast…


    Here is the original broadcast:


  • Anthony Mugan October 30, 2014, 11:33

    Just to follow on briefly the interesting points raised by Rob Henry and Eniac..

    I would agree that a non-zero probability for the emergence of life and its eventual evolution to a technological species could (as far as we can say at the moment) be extremely close to zero. I would just note that the ‘window’ for the range of probabilities for it to be credible that we are the first is extremely small…I’ll let others attempt to put an upper limit on it but even something like one chance per billion potentially habitable planets in five billion years following planetary formation would still be a bit on the high side for the galaxy. To translate that onto the scale of the universe…well, the mind boggles.

    Ok – yes, we could, in principle, be a statistical fluke where life just happened to spring up more or less as soon as the earth was capable of sustaining it and that this was a unique event. That would be a cosmic coincidence of such epic proportions (not that we observe ourselves to be here, rather that we would live in such a astonishingly fine tuned universe) that it would almost get me thinking seriously about religion.

    The interesting point about the complexity of the LUCA is very significant one and is one of the reasons I’m inclined favourably towards panspermia models. It is indeed extremely unlikely that something that complex just ‘popped’ into existence all by itself. Complexity theory may play a role here but I tend to prefer models in which the observed result emerges naturally and predictably rather than relying on extremely unlikely chance events. I do think it is high time panspermia was subjected to an all out battery of tests to really see if it holds up. So far it seems to have past every test, which I take as a fairly big hint given how far this theory has come since the 1970’s.

    I’m not sure we can conclude that the ‘great silence’ means we are alone in this galaxy at all. I was just wondering what would persuade me otherwise…

    If in 30 years time we’ve managed to go back to Mars and to visit some of the astrobiologically interesting places in the outer solar system, and ideally had some sample return missions on comets and found no sign of life that would be a pretty big blow to panspermia.
    If, again in about 30 years time, we’ve got the ability to detect bio-markers in exoplanet atmospheres and the results are clearly negative for a sample of earth like planets, it would again be looking bad for the prospects of life elsewhere. (Let’s be realistic – there would probably just be a ding dong arguments about possibly positive signals).

    Perhaps I would then have to brush up on my catechism…

  • kzb October 30, 2014, 14:15

    Prokaryotic life started just about as soon as it could.
    However, eukaryotes didn’t appear until 2 billion years later.
    Now admittedly the sample size is one, but this is evidence that abiogenesis is common, but making eukaryotes is rare.
    That is the arguement anyway.

  • Rob Henry October 30, 2014, 18:51

    Once more I find myself agreeing with the substance, if not the thrust, of Anthony Mugan’s arguments, save for one point. Once more I find it that point having high consequence. Anthony wrote…

    “…we could, in principle, be a statistical fluke where life just happened to spring up more or less as soon as the earth was capable of sustaining it and that this was a unique event. That would be a cosmic coincidence of such epic proportions…”

    Later, kzb also put in “Prokaryotic life started just about as soon as it could.” With that sentiment in mind, I would like to examine the evidence for the earliest life on Earth too see what consequences its impact might have on estimating the probability of abiogenesis. Here, step by step, is the way it goes.

    1) The evidence for such early life here is reasonably strong, but not unequivocal till about a billion years after the Late Heavy Bombardment (LHB). As we will see, we really need the earliest evidence to prove correct.

    2) For our purpose, we next need a mechanism for abiogenesis that is not much much more active in the first few hundred million years after the LHB. For example, it now seems that a reducing atmosphere that could produce the prebiotic soup could have only existed on Earth for a few million years, and in the early Earth volcanic activity would be very much higher. If it works out that abiogenesis is driven only by early occurring mechanisms, then, obviously, life would be expected to appear early or not at all. The dates for the earliest fossil signs of life is of most evidence value if the probability of abiogenic events is completely time invariant. Let us assume that, no matter how unrealistic.

    3) Next we must live on a planet where intelligent life would have a chance of emerging in our absence for a much longer time than the gap between the LHB and life’s first appearance. Many believe that Earth would have remained in that receptive condition for 1-2 billion more years, but some disagree. If it ever proves that this possible period of a benign Earth is only circa 100 million, our methods would once more be invalidated, this time due to constraints on the observer.

    4) Now we have it Lineweaver Davis, carefully specifying the above preconditions, did a couple of analyses and found “evidence that the probability of abiogenesis is moderate (> 13% with 95% probability)
    and cannot be extremely small.”

    This was a triumph for conditional probability. Unfortunately, very many have quoted this without understanding the context. Also note that 13% figure is per billion years – an arbitrary time interval chosen because it seems reasonable to extrapolate out to but an unreasonable stretch to extrapolate much further.

  • Rob Henry October 30, 2014, 22:11

    As a second followup to Anthony Mugan’s 30 Oct comment, I am also intrigued by the possibility life on Mars, but find NASA’s approach to it strange. As a kid I vividly remember the Viking lander results, and how they found a soil chemistry that both oxidised expected nutrients and synthesized complex organics in the presence of light that was devoid of all uv wavelengths. I understood why they came to see life as an unlikely explanation, but have never understood why they weren’t equally enamored with the unique – and still unexplained – chemistry they had discovered. Its almost as if they had a secret conference and decided that chemical searches for life were too academically challenging for the agency, and ‘following the water’ was a future policy that would be more suited to their skill level!

    Also of note is the seasonal Wave of Darkening that could point to a massive scale for life on Mars. In the last published attempts (that I could find when I last looked) to model this through dust dispersal, the fit was so poor that the predicted albedo change seemed to go in the opposite direction to the observed one. That seemed like yet another failing of imagination when the going got tough, were once more it was assumed that an explanation could be found (and it probably could but, to me, probably ain’t good enough where the implications are so high).

  • NS October 31, 2014, 1:48

    If there is life on other worlds in our solar system, is there any way it could be detected remotely? There was an observation of excess methane in Mars’ atmosphere (which I guess didn’t pan out) and there’s discussion of getting spectra that might indicate life from extra-solar planets, but would that work with places like Europa? In terms of cost and relatively quick return of information, building some sort of life-detector in near-Earth space might be better than sending probes to every possibly life-bearing world in the solar system (which would be great, but doesn’t seem to be in the cards). Just speculating…

  • Anthony Mugan October 31, 2014, 11:15

    @Rob Henry
    Thanks for the very interesting responses. I had missed the paper you reference, for which many thanks…I shall be reading it with interest. I hadn’t realised it was possible to constrain the probabilities to that extent ( allowing the specific assumptions in the model). It does rather seem to support the idea that life could be quite common, after which point I would argue natural selection should be a universal phenomenon and one well suited to increasing diversity over a period of time.

    I know what you mean about NASA seeming to be taking an awefully long time to get to grips with this question. I was reading something the other day which suggested the proposed Mars 2020 mission would include some equipment that could potentially detect life, but it would need someone more expert than I to be certain of the capabilities or limitations of them. Hopefully we’ll get there in the end, but there is a cynical little voice in the back of my head, for reasons that wouldn’t be appropriate to go into here, which is telling me not to get too optimistic about it.

  • Rob Henry October 31, 2014, 19:16

    Yes Anthony, deriving that sort of probability from a single data point is so counterintuitive to we humans, that we never realised we could do it until Richard Gott famously stared at the Berlin Wall in 1969 and wondered if there any way to tell how long it would last. The maths were so simple that it came to him instantly. At first some debated its validity (because it just seems wrong, no matter how logical) but it has passed every objection and is now widely used. Unfortunately, it is also the basis for the Doomsday Argument. Perhaps that obvious extension was why we had such initial difficulty seeing this simple method? brief details of this are in this Wikipedia article under the heading ‘Copernicus method and Doomsday theory’

  • Eniac November 1, 2014, 23:10

    Anthony Mugan and Rob Henry: I am not sure we are talking about the same paper. Is it the one that says in the abstract

    Previous authors have analysed this information, concluding that it is evidence that the probability of abiogenesis is moderate (>13% with 95% probability) and cannot be extremely small. In this paper I use simple prob
    abilistic model to show that this conclusion was based more on an unintentional assumption than on the data. While the early formation of life on Earth provides some evidence in the direction of life being common, it is far from conclusive, and in particular does not rule out the possibility that abiogenesis has only occurred once in the history of the universe

    It seems to me that this is fairly consistent with my earlier arguments and expressly allows a “indistinguishable from zero” chance of abiogenesis. Add to that Rob’s excellent argument that the reason abiogenesis occurred early (if indeed it did; the evidence is weak) might be that conditions only were good then, and there is no case left for common abiogenesis.

  • Eniac November 1, 2014, 23:39

    There seem to be a few misunderstandings about LUCA, here. First, Rob Henry says:

    It seems highly improbable that, even in the simplest and most sheltered niches, primitive organisms were all outcompeted by far more complex and later forms that all haled from a single line (rather like primates one day evolving into forms that outcompete to extinction all other forms including bacteria)

    While it seems improbable, it is actually the expectation for any constrained phylogeny that if you go back far enough, you end out at a single source, and that source is way downstream of the root, or origin, of the phylogeny. I have often cited the mitochondrial Eve as an example: Eve lived about 200,000 years ago, and despite being the sole ancestor of all humans along female lines, she was not alone in the world, and probably not very special, either.

    When it comes to all of life, say that Rob is right and there is an undiscovered life form left on Earth the does not descend from LUCA. What does this mean? It means nothing, the consequence is purely semantic: It means that LUCA is not LUCA and that the real LUCA is a little bit further up the line. Still far down from the root, in any case.

    LUCA was not special at all, it was surrounded by many other life forms different from it. Its special status exists only in its far future, after all its contemporaries become extinct.

    Second, Anthony Mugan says:

    The interesting point about the complexity of the LUCA is very significant one and is one of the reasons I’m inclined favourably towards panspermia models. It is indeed extremely unlikely that something that complex just ‘popped’ into existence all by itself.

    I think there is a critical mistake here: LUCA is not LUCA because nothing else existed before it. It did not pop into existence, it came from a whole other tree of life which is hidden from us. There are no fossils for life this far back, and without known descendants there is nothing we can know about what the siblings or ancestors of LUCA were like. That does not mean they didn’t exist. Quite the contrary, we know they must have existed. Unfortunately, we also know we’ll never find out more about them, which is very frustrating.

  • Eniac November 2, 2014, 0:00

    Rob Henry: Richard Gott’s argument is not really relevant, here. He predicted future events, without a posterior constrain, aka survivorship bias. Statistics on the existence of life, on the other hand, must be restricted by the posterior knowledge that we are here to make the observations. Let us make two assumptions:
    1) We are here, after 4 billion years have passed on Earth
    2) There is no limit to how fast we could appear after abiogenesis

    Then, looking back, any time between 0 and 4 Gy would are equally likely for abiogenesis to have happened. The expectation should be 2, with 1 and 3 also quite likely. Assumption 1) seems safe. Assumption 2) is conservative: If we relax it and assume that some minimum time is needed for evolution to go from abiogenesis to us humans, it shifts the probablities towards an earlier abiogenesis (1 Gy rather than 3), which is indeed what we find.

    I see no evidence whatsoever in these obervations that would give us information about the rate of abiogenesis when the posterior assumption (# 1) is taken away. The information value of knowing the start time is exactly zero.

  • Rob Henry November 2, 2014, 16:08

    Sorry Eniac, wrong reference. It should be

    As for the mathematical approach, I acknowledge the important differences that you point out, but, from memory, the confidence interval is extracted with the same maths as per Gott. Glancing at it again it looks different, and that presents a problem to me as, if we attempt to adjust for that observer effect we would have a neigh insuperable problem as follows…

    We now need the probability distribution of the emergence times of intelligent life, as referenced against a living planet that is receptive to it forever. This won’t be Poisson, as it cant appear at t=0 as it would seem to involve several major evolutionary transitions. Worse still, it seems reasonable to assume that we are very early occurring on that distribution, making those constraints very important if the remaining natural receptive time (wrt evolution of intelligence) of Earth is comparable to the LHB – abiogenesis interval. Best find it is not, and ignore the small (in that instance), but incalculable adjustment.

  • Rob Henry November 2, 2014, 16:51

    As to LUCA and extinction patterns, yes Eniac, some, such as the late Jay Gould, believed that random walk pattern models extinctions, and that could bolster your case. There is some good data for it fitting well in post-Cambrian animals up to the level of class, though not phylum (with an admittedly small sample size) level. The problem is it does not seem to extend well to its simpler brethren (here we must switch from analytically to anecdotal mode, due to the nature of microfossils). For example, cyanobacteria fossils appear about the first time they can fossilize, around 3.5 billion years ago.

    The question still remains, is it realistic to assume that an overly complex creature can displace a simpler one from every niche just as easily one complex creature can displace other complex ones?

    Having said that there is a third option outside competitive displacement and panspermia. The last major impactor of the LHB would have stearilised the entire surface of the Earth at >1000K. Some rocks that it knocked off would have fallen back and, if life had started here already, reinfected the world with only those lines that were complex enough to have a stringent mode or spore.

  • Eniac November 3, 2014, 22:24

    Rob Henry:

    … some, such as the late Jay Gould, believed that random walk pattern models extinctions …

    To my knowledge, this is not a belief held by some, but rather a textbook fact in population genetics. Look under “genetic drift”.

    The question still remains, is it realistic to assume that an overly complex creature can displace a simpler one from every niche just as easily one complex creature can displace other complex ones?

    Given the enormous variety of those two branches, it would be hard to imagine a niche in which a more primitive organism would outcompete both archea and bacteria. So, yes, I think this is quite plausible. Not that this is necessary, as random drift in finite populations is already sufficient to explain the extinctions.

  • Eniac November 3, 2014, 22:40

    I am not sure I follow your argument that leads to a “neigh insuperable problem”. It seems really simple to me: Abiogenesis would have to have occurred between 4Gy and now. The most pessimistic model would be one where we neglect the fact that some time is required to get from abiogenesis and humanity. In this model, abiogenesis occurs at a constant rate between 4Gy ago and now, i.e. the chance of it having occurred after just 1 Gy would be 0.25.

    Adding a minimum time necessary between abiogenesis and humanity increases this likelihood, as does an assumption that abiogenesis was more favored under earlier geological condition (such as a reducing atmosphere) than it would be now.

    After considering all this, I can only conclude that the often stated “surprise” at how early abiogenesis occurred on Earth is completely baseless, statistically. It is probably a myth propagated in some popular book that I don’t know about, like so many other modern myths. With a probability that, in the worst case, is 0.25, abiogenesis within the first Gy can hardly be called a surprise.

  • Anthony Mugan November 4, 2014, 5:02

    Yes – I was too flippant with my ‘pop into existence’ phrase. Yes, of course there would have to be an extended period of evolution prior to LUCA before we get back to abiogenesis and a pre-biotic phase before that.

    That was the point I was trying to get at but phrased it badly – we run out of time (the alternative – an extremely early appearance of life, for which there are some suggestions in the data would just add to the scale of the paradox)

  • Wojciech J November 4, 2014, 9:10

    ” The REAL Fermi paradox is not this, it is why the Earth was not colonised long before we evolved. It’s a bigger problem than simply not picking up anything from SETI.”
    I don’t see it as any difficult paradox. Colonizing alien biosphere is counter-productive. You get more information and advantage from studying it rather than erasing innovative designs and natural biological and chemical laboratory.
    To get to other stars and planets you have to create artificial environment or change your bodies in a way that makes colonization for sake of living space pointless.
    So I don’t believe any alien civilizations would be particularly keen on colonizing other biospheres.

  • Rob Henry November 4, 2014, 16:02

    Eniac,genetic drift can’t be applied to this situation, and if we did try we recover the opposite effect. Firstly it applies to genes within populations, not populations themselves.

    Secondly, the rate of drift may be characteristic of one gene, but it varies by orders of magnitude between different genes. If we applied it to populations, this would equate to some being far deeper ensconced in their specialist niche than others.

    Note that some genes are so highly conserved that 50 odd of them have recognisable form in neigh every single descendant line, and many more will be extant in one or more modern lines (a few hundred to several hundred, though we may never know exact numbers). Once more we must say, ‘if so much of LUCA has survived, why not the genes of its contemporaries?’ It’s a question I can think of answers to but none involve genetic drift. The most parsimonious solution is that it is very very close to the abiogenesis event – so soon that biological specialisation had no opportunity to play its heavy hand.

  • Rob Henry November 4, 2014, 17:50

    oops, Above in my last comment I left out something rather important, namely why didn’t Gould et al see this problem. The answer is they did, but they has a rather clever possible fix. I now see how important it is to recount that.

    They postulated that a high proportion of all extinctions occur during mass extinction events. Further, after examining a couple of these they postulated that survival was more due to factors that occurred so infrequently that natural selection could not adapt them to it. Only traits they had picked up for incidental reasons eg if a species had the ability to hibernate seasonally, then a few aberrant individuals may have been able to hibernate without preparation upon a meteorite impact. If you were a large animal without this trait – then you had no show.

    That is how they recovered a random walk. It was the opposite to what would be expected by theory alone under classic uniformitarian conditions.

  • Eniac November 4, 2014, 19:02


    ‘if so much of LUCA has survived, why not the genes of its contemporaries?’

    This is a tautology. It is the very definition of LUCA that none of its contemporaries’ descendants survive.

    The only thing you may wonder about is whether LUCA should be more or less complex than it is, but I think it will be hard to make a good argument for any sort of surprise, here.

    I am not even sure we know exactly how complex LUCA was. We know is it had RNA, DNA, polypeptides and (presumably) lipids, plus a genetic code very similar to today’s for making the polypeptides. How complex the organism itself was, though, may be hard to estimate.

  • Rob Henry November 5, 2014, 18:38

    I must apologise Eniac, but you suggestion that random drift could be directly theoretically extended to population themselves, took me to a realm so far beyond this world that it was easy to get lost. That diversion over there is a little more I want to say.

    In some regards LUCA, looks more complex than modern forms, such as with evidence that it used 22 amino acids, where modern forms typically use twenty. Also, the one membrane organelle that I know of in prokaryotes is the acidocalcisome, and was almost certainly in LUCA, hinting that it may have had more. There are also other regards in which it is expected to be more eukaryote – nucleus like, such as with a linear genome.

    However, no matter how complex it was, and how parsimonious the assumption that it lay near the root of all life, there is at least one strong bit of evidence that something far different (presumably simpler) preceded it (other than our fanciful want of believing that life can be simple).

    RNA world is so hypothetical that we should not normally use it as too much of a crutch, but here’s the rub. The idea came into the mainstream after it was found that a few stretches of RNA have some limited degree of catalytic-type activity. Soon after, some made the bold prediction that ribosomal catalytic action would be mediated by RNA, with protein as the scaffold, not the other way round. Incredibly (though the system is so complex it is hard to study) this has so far been borne out, and it seems very hard to explain any other way (than a bygone RNA world).

  • Eniac November 7, 2014, 13:13

    Rob: RNA world is an important stop/path on the way from life’s origin to LUCA. It is the one thing from that time we reasonably know to be real, as there is too much cirumstantial evidence to dismiss. To me, the most damning is that RNA molecules survive to this day in key functions that could otherwise be done much better by proteins.

    Ribosomal RNA, in particular, which makes sense with respect to the chicken/egg problem: If ribosomes make proteins, what made the first ribosomes? The answer, of course, is that the original ribosomes were all RNA. Proteins were adopted as components later, but never quite managed to squeeze RNA out of some key positions.

    We also know that the very first reproducing molecules must have been capable of carrying at least some information, which pretty much rules out lipids (although they may have had a role as cofactors, of course). As I see it, the key molecules in abiogenesis must have been RNA of some sort, as the only species we know of that can comfortably act as enzyme and information carrier, both.

  • Rob Henry November 7, 2014, 19:02

    Eniac, if that in fact RNA world was the first life I don’t know if we would need lipids. For abiogenesis a sufficiently complex far from equilibrium system of chemicals may be expected to contain autocatylitic sub-cycles, but the lethal dilution problem prevents us getting any further. One of the few answers is a semipermeable (presumably lipid) membrane. Another is strong surface adsorption.

    Nucleic acid is poly anionic. If it and almost all its metabolic intermediates were polyanionic or attached to polyanion co-factors that would also solve the problem if they evolved beside positively charged (clay). Our oldest biochemical pathways do indeed seem to have this characteristic. Such a start might also answer another fundamental problem.

    It is usually energetically unfavorable to form longer molecules in aqueous solution through condensation. If the molecules of a sub-cycle are all (water excepted) restricted into a two dimensional diffusion, that can change, since new bonds no longer restrict the subunits to loss of as much rotational freedom.

  • Eniac November 9, 2014, 0:04

    Rob: I like the suggestion that the earliest abiogenetic chemistry might have happened on surfaces (membrane or solid), where diffusion characteristics are much different and molecular associations more favorable. I have not heard it put quite this way before.

  • ljk November 18, 2014, 16:47

    Names in bottles: a new tool for exploration?

    by Dan Lester

    Monday, November 17, 2014

    I’m in space! Well, my name is in space. Okay, the letters of my name are encoded on a chip in space. Those ten bytes occupy a few nanograms of memory on a space vehicle. It cost me nothing to send them there, and maybe a minute of my online time. Now, I confess, I don’t remember which mission vehicle that chip is on, so I really don’t have a clue where those bytes are right now. It was a few years ago when I did it. I was led to believe that as a result of putting my name there, I would feel more involved in space exploration. I’m frankly still waiting for that to happen. But I recognize that such action may have a more profound effect on others who do it.

    I was led to believe that as a result of putting my name there, I would feel more involved in space exploration. I’m frankly still waiting for that to happen.

    The outreach strategy of inviting people to put small digital pieces of themselves on space missions is one that generates good response. Most opportunities have been for NASA missions, but ESA and JAXA have offered some as well. Most have been planetary/small body missions or, more generally, planet-related missions such as Kepler. That is probably because such objects are considered more tangible cosmic destinations for humans than an active galaxy or a coronal hole. Most allow just a dozen or so bytes for a name, but a few missions were somewhat more generous about solicited digital content. The “Face In Space” opportunity had STS-133 and -134 Space Shuttle missions carry digital images uploaded by the public. Cassini carried to Saturn more than half a million digitized signatures and even some digitized paw prints from beloved pets.

    Full article here: