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The Silurian Hypothesis

Filed under: — gavin @ 17 April 2018

One of the benefits of working for NASA is that the enormous range of science the agency covers – from satellite records for the present day, to exoplanet climates, from early Mars and deep time on Earth to the far future – and the opportunity to think ‘big’. This week sees the publication of a paper I wrote with Adam Frank that we hope might provoke some ‘big’ thinking.

The Silurian Hypothesis (preprint) is the idea if industrial civilization had arisen on Earth prior to the existence of hominids, what traces would be left that could be detectable now? As a starting point, we explore what the traces of the Anthropocene will be in millions of years – carbon isotope changes, global warming, increased sedimentation, spikes in heavy metal concentrations, plastics and more – and then look at previous examples of similar events in the geological record. What is unique about our presence on Earth and what might be common to any industrial civilization? Can we rule out similar causes?


(Dino Street (University of Rochester illustration/Michael Osadciw)

Adam had a nice piece in the Atlantic and there is also a good write up on Motherboard.

The naming of this idea comes from a 1970 Dr. Who episode where an ancient race of reptilians (“Silurians”) who had put themselves in hibernation to avoid a global catastrophe were awakened by experimental nuclear physics experiments. (I tried to find ‘prior art’ on pre-human terrestrial civilization that wasn’t based on notions of panspermia or ancient astronauts, but I haven’t yet been successful – anyone?). Needless(?) to say, we aren’t proposing any such occurrence (not least because the Silurian period is too early for the development of complex life on land).

The ideas in the paper lead naturally to many lines of speculation, some of which are relevant to us today, and some of which are just interesting (to us at least). For instance, given that the more sustainable a civilization is, the smaller its geophysical footprint might be, what does that imply for the detectability of long-term civilizations? Does the onset of ocean anoxia at the end of many of these events suggest a possibility of cycle where the collapse of one civilization provides the seeds (fossil fuels) for the next?

The whole idea is so intriguing that I wanted to do more with it than is possible in a journal article. Other scientists have occasionally dabbled in science-fiction (notably Carl Sagan and Fred Hoyle) and so, following their lead, I wrote a short story “Under the Sun” about the consequences for finding such a signal.

Literary as well as scientific criticism welcomed!

References

  1. G.A. Schmidt, and A. Frank, "The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?", International Journal of Astrobiology, pp. 1-9, 2018. http://dx.doi.org/10.1017/S1473550418000095

110 Responses to “The Silurian Hypothesis”

  1. 51
    Oh Brother says:

    Carrie, seriously? You need to relax just a bit.

  2. 52
    Carrie says:

    28 [Response: I wouldn’t use the Express as a primary source for information on new scientific papers. Or indeed anything beyond the day of the week. – gavin]

    Th Express might even get the say of the week wrong as well. Unfortunately the Express is not in fact the issue here.

    Is The Silurian Hypothesis true? No.
    Is The Silurian Hypothesis necessary? No.
    Is The Silurian Hypothesis useful? No.

    https://idioms.thefreedictionary.com/Give+an+inch+and+he%27ll+take+a+mile

    Give an Inch to a liar, a manipulator, a think tank, they’ll take a Mile distorting it to the extreme while destroying the reputation of the man who offered up that Inch.

    Gavin should have kept that Inch to himself. For many obvious logical reasons.

    Is the The Silurian Hypothesis a climate science paper? No. It is not.

    Is The Silurian Hypothesis true backed by hard evidence? No.

    Was The Silurian Hypothesis necessary? No.

    Is The Silurian Hypothesis useful? No.

    Does The Silurian Hypothesis advance the cause of urgently addressing climate change on the planet? No. It sets it back.

    Does The Silurian Hypothesis help to educate or inform the public or journalists about the overwhelming evidence of climate change, it’s causes and solutions? No. It muddies the waters even more than they already are.

    Does The Silurian Hypothesis enhance the credibility and believably of the author/s in regard to their expertise in climate science? No. It decreases it.

    Does The Silurian Hypothesis enhance the credibility of others who are directly connected to the author/s such as Stefan’s recent article here and enhance Michael Mann’s already tarnished reputation in the public sphere any? No. It lessens their credibility by association.

    Does the publication of The Silurian Hypothesis open up a new opportunity for powerful forces to further undermine the credibility of climate science and climate scientists? Yes.

    Will editorials and social media comments labeling The Silurian Hypothesis as a crackpot paper written by a crackpot climate scientist help or diminish the hard work of all climate scientists and many others?

    Yes. It diminishes them all.

    Making it that little bit harder to cut through.

    All it needs some days is https://idioms.thefreedictionary.com/the+straw+that+broke+the+camel%27s+back

    [Response: Please tell us how you really feel. Seriously though, it’s not that big a deal and every additional minute you spend fretting about something you clearly have no interest in, is time you could be doing something productive. – gavin]

  3. 53
    sidd says:

    Anthro signal writ large in decline of megafauna:

    DOI: 10.1126/science.aao5987

    Disturbing paper, fig 3 in particular.

    Dr. Schmidt, thanks for writing this. I find it quite sad that some here demand that climate scientists confine themselves to the One True Cause of climate activism to the exclusion of all else.

    sidd

  4. 54
    Ron R. says:

    Ok, just listened to the paper. Very interesting. I don’t remember if it’s been factored into the possible signals of present human activity in the future fossil record, but I would think that landfills worldwide would hold evidence for a long time due to the constant accumulation of A LOT of material. I’ve often remarked to myself how dumps, that have been in the same locations for decades, don’t ever seem to fill up. So maybe it’s going lower or wider.

    The other thing that perhaps was addressed but that I might have missed (I’m hiking as I listen) is that for the hypotheses to be true, one similar to the present situation, one would expect that it wouldn’t be scattered individual signals over millions of years you’d need to find but a simultaneous occurrence of most or all of these conditions in one (or more, for other possible civilizations) localized points in time. But maybe I’m muffing this up.

  5. 55
    Carrie says:

    52 [Response: Please tell us how you really feel. Seriously though, it’s not that big a deal and every additional minute you spend fretting about something you clearly have no interest in, is time you could be doing something productive. – gavin]

    How I feel is not relevant. Why bring it up – because Argumentum ad hominen should be beneath you. Unfounded claims of ‘Fretting’ are not useful because that takes away from the dignity of another person rather than arguing his/her ideas. You know that which is likely why you did it.

    I have strong interest in climate science and the consequences already present of climate change. I spoke to that issue and provided examples of how interested I am. Similar to climate scientists I am reviewing some data/info/events then drawing my ‘Hypothesis’ of the likely logical consequences of ‘Action and Reaction.’ I am very confident in the Forecast at present – for they are already occurring as I write eg “Why hasn’t Trump fired that idiot?” Wait until Lamar Smith and others get a hold of it.

    What you do in your own time for recreation and hobbies is your business. I am merely commenting on published paper and it’s related commentary here and elsewhere. It’s on topic.

    As to the advice of “every additional minute you spend fretting about something you clearly have no interest in, is time you could be doing something productive” may be it is you who could look closer to home?

    For example a reminder of what really matters today, as Schmidt said, “Talking to the public and the media is often neglected in assessing people’s contributions, and yet, as taxpayer-funded scientists we have a collective responsibility to share the expertise we have with the broader public. I’m very happy that the efforts I’ve made-in collaboration with many colleagues-have been recognized by this new award. I hope that this can serve as an encouragement for more scientists to dip their toe into the public discussions.”

    or Schmidt, an expert in climate modeling, began his career at GISS in 1996. His primary area of research is the simulation of past, present and future climates.

    “It’s an honor to lead the team of talented scientists at GISS,” he said. “The work being done here has implications for societies across the planet, and I will strive to make that research as valuable as possible.”

    Each to their own self be true. It’s not that big a deal to me either.

  6. 56
    Ray Ladbury says:

    Carrie,
    Get a grip. This is a speculative work. It does raise some interesting questions about how our own species might be changing the planet. That your own imagination is too feeble to see the potential value of such speculation does not mean it has no value. Finally, grow up.

  7. 57
    Fred Magyar says:

    Asteroid, smashteroid!
    Gary Larson of Far Side fame, had a great cartoon titled: ‘The real reason dinosaurs went extinct’. Showing three dinosaurs lighting up and smoking cigarettes.
    http://zettlhomeopathy.ca/zettlme/wp-content/uploads/2014/10/dinosaurs-smoking-farside.png

  8. 58
    Russell says:

    This changes everything.
    Will Carrie’s thoughts be appearing in The Guardian, The American Thinker , or both ?
    SNL needs to know.

  9. 59
    Russell says:

    Given The Express April 1 lede shift to : NASA SHOCK: Huge ‘alien herd of animals found in space probe images of Mars’, I suspect Gavin will survive his Atlantic adventure:

    Jon Austin of The Express continues:

    “MARS could be flourishing with Earth-like life according to a shocking conspiracy theory sparked by these NASA images. Pictures taken from above by space probes reveal there is a thriving ecosystem supporting life on the Red Planet — according to wild claims spreading online.

    A video uploaded to YouTube shows the pictures which show a cluster of objects on the planet’s surface spanning for miles.

    And another angle appears to reveal other parts of the area rumoured to be feeding zones for the “alien animals”.

    conspiracy theorist Neal Evans claims this is proof of life on the Red Planet — alongside an entire environment capable of supporting them.

    He said: “I believe this to be a habitable lush thriving ecosystem on Mars.

    “I studied the section of map for hours and compared it to birds eye views of places on earth, and it seems to be next to the north pole.

    “The images are all low resolution, but you can see clear water lines, lakes, either vegetation or some type of life forms seeming to be dependant on the water source.”

    He posted the original footage to his YouTube channel — named Disclose Screen — where he has received thousands of views, Dailystar.co.uk reports

    Viewers were gobsmacked by what they saw. One comment read: “We have seen bases on Mars, and a space fleet and now they are growing stuff.” And another added: “Well spotted. A real eye opener. Hard to begin to imagine what is out there, and what discoveries will be made in life times to come.”

    Mr Evans added: “I have been studying Mars and its story for years — we only know what they allow us to know.

    RELATED EXPRESS ARTICLES
    ‘Alien face’ in NASA image of Mars is ‘proof of extraterrestrial life’
    ‘Mushroom cloud’ on Mars ‘proof alien life wiped out by nuclear war’

  10. 60
    SecularAnimist says:

    An earlier commenter mentioned this 1997 episode of “Star Trek Voyager” in which Voyager encounters a space-faring species called the Voth, who are discovered (via genetic analysis) to be descendants of a technologically advanced dinosaur species that developed warp drive and fled the Earth millions of years ago to escape environmental catastrophe. The Voth have forgotten their origins and refuse to believe that they come from the same planet as mammals (the Voyager crew) who they despise as inferior.

    There is some brief discussion in the episode along the lines of this paper, regarding the difficulty of finding any evidence of a long-vanished technical civilization buried beneath hundreds of millions of years of geological and biological change.

    https://en.wikipedia.org/wiki/Distant_Origin

  11. 61
    nigelj says:

    Carrie, lighten up a bit. The silurian short story and related research paper was obviously intended to 1) be thought provoking 2) draw the general public into scientific issues and 3) provide some light relief from the serious and sometimes depressing issue of climate change. Everyone needs some light relief to keep functioning.

    I agree scientists could sometimes communicate things better, we can all do so many things better. Just remember scientists are up against a media that only wants to publish the latest celebrity scandal, and denialists determined not to learn anything no matter how brilliantly it is described.

  12. 62
    Russell says:

    The moral hazard Express science writers often pose is making The Wall Street Journal look good.

    Not that that is always a bad thing.

  13. 63
    Nick O. says:

    Phew, I suppose we have to be grateful that the lower branches of the Press have not got round to reading (the late and much lamented) George Box. I mean, just imagine the headlines, “Top scientist says all models are WRONG!!!” By that analysis, global warming would disappear in a puff of smoke (or do I mean a jar of CO2?). The Silurian hypothesis is interesting and really worth discussing, not just as a thought experiment but also because it gets us to think a bit more about our own rather wonderful planet and climate system and how much we really understand about it. That said, I still think the crustal recycling system is not perfect and there would/should be traces left of prior civilisations. If we suppose the continental-tectonic cycle is of the order of 500 Myrs, and there wasn’t much multicellular life before the Cambrian, that gives us a kind of time limit within which we might look.

  14. 64
    sidd says:

    Odd. dx.doi.org was unable to find the doi in my last post. The full reference is

    Body size downgrading of mammals over the late Quaternary

    Smith et al., Science, v360, pp310-313, 2018

    sidd

  15. 65
    Carrie says:

    59 60 61, given The Express and Flat Earthers are more popular than realclimate as a source for info maybe Gavin decided if you can’t beat them join them.

    Carrie, lighten up a bit.

    Me lighten up? Golly, I have been laughing nonstop since I saw this. The best British comedy since The Life of Brian. Though I admit that Science Fiction is an incredibly popular form of entertainment such as Star Trek and Star Wars. So are conspiracy theories. We have now entered the Twilight Zone where climate scientists are equivalent to David Icke (claimed he was Jesus reincarnated at one point) and a “science paper” is up there with an episode of InfoWars.

    So given how the ‘deplorables’ already treat genuine climate science evidence what else would one expect to blow back? With this: “Was prehistoric global warming caused by pre-human species; AN ANCIENT civilisation may have rose up and died out quickly scientists have said;”

    These scientists need urgent funding. We simply must know the answers to these stupid useless irrelevant sci-fi conundrums now! There could not be a better use of a climate scientist’s time and his lifelong public education and training than this matter.

    nigelj, “The silurian short story and related research paper was obviously intended to 1) be thought provoking”

    It’s been a great success. Provoked a few thoughts in me and then there are the many comments about Star Trek and Dr Who. Great stuff. Important news. Very informative. More please!

  16. 66
    Carrie says:

    52 Gavin’s response

    Quit the loose climate talk and get serious! https://youtu.be/skilmEHMsMc

    Scientific Reticence: A Threat to Humanity and Nature
    Hesitancy among scientists to express the gravity of our situation is a major block to our understanding and response to climate change, The reticence arises from political pressure, institutional conservatism, so-called ‘objectivity’ and more. Dr. James Hansen (immediate past Nasa/Giss Director) https://youtu.be/S7z61UZoppM

    Distractions onto non-issues and fictional thought experiments is no help.

    Counterproductive – thwarting the achievement of an intended goal; tending to defeat one’s purpose: surely that is obvious enough.

  17. 67
    nigelj says:

    Carrie says “Distractions onto non-issues and fictional thought experiments is no help.”

    Even when they are clearly at least getting people looking at climate related issues? You are not thinking it through, and I suspect your laughter is more self righteous hysterical laugher than anything! the laughter of the fine actor Jack Nicholson.

    The whole silurian thing is a harmless publicity hook. You keep saying “use marketing more” and when Gavin does you rubbish him (although he probably had a range of motives and theres a serious side to the hypothesis). This makes you a person hard to reason with.

  18. 68
    OhMGBrother says:

    If you actually read the paper “Carrie”, you would have read this statement:

    “While we strongly doubt that any previous industrial civilization existed before our own, asking the question in a formal way that articulates explicitly what evidence for such a civilization might look like raises its own useful questions related both to astrobiology and to Anthropocene studies.”

    Somehow I doubt that you know much about how science works. You see, science is in the business of asking questions, then narrowing down the possible answers through a process of elimination. There is nothing wrong in this exercise because the question that is being asked is legitimate: what was the cause of certain striking anonmalous events in the very distance past and how might we go about finding out? Generally we start out with what we know because the present is key to the past. Since the answer to this question is unknown we begin by entertaining all hypotheticals (even extraterrestrial I’d say). About the use of a fiction story, science fiction by scientists has a long history. Google it.

    But I suspect that you are just enjoying yanking chains here and hoping to create division by feigning outage. Your previous comment, “I expect calls for Gavin’s resignation as Lab Director for GISS to be coming thick and fast” was the giveaway for me. For all I know, you don’t accept the validity of global warming at all – I mean your demeanor is that of a professional skeptic, excessively rude.

    Or maybe your just a troll.

  19. 69
    OhMG Brother says:

    By the way, Carrie, newsflash, just because you personally find something hard to believe doesn’t automatically make it wrong. History is chock full of things people were sure was wrong or utterly impossible until they were proven right. Just sayin.

    https://rationalwiki.org/wiki/Argument_from_incredulity

  20. 70
    OhMG Brother says:

    One last thing, Carrie (without commenting on the validity or not of this or any particular hypothesis) trying to censor discussion by bullying someone into silence is decidedly not a scientific method, i.e. you are not a scientist.

  21. 71

    Interesting. I have speculated about this for some time. I write SF as a hobby and occasionally self-publish. One short story I wrote (not yet in the wild) was about dinosaurs who have a reasonably high-tech civilization but all very sustainable and discover this impact event is due and will put them into an extinction-threatening climate shift. Also working on a novel of a distant future where intelligent insect life has evolved and evidence that humans may have been intelligent shakes things up.

    Until we encounter a different form of intelligent life, we just don’t know if intelligence can evolve from a different start – notwithstanding that some life forms are in various ways pretty intelligent.

  22. 72
    Tokodave says:

    Thanks Gavin and Adam. As a geologist this is something I’ve pondered as well. Think, as an example, about how rare and limited footprints in mud are, and the lucky geologic breaks that allow them to be preserved and lithified. Now think about the pervasive impacts we as a species have on the environment. Also think about the limited geologic time horizon we have occupied and likely will ever occupy.
    I’ve always envisioned this as a future geologist, or whatever they might be called in the future, stumbling on an outcrop in a sequence of sedimentary rocks and thinking…well this is a bit strange…

  23. 73
    OhMG Brother says:

    I should say, re: my last comments about censorship, that once an hypothesis or idea has been put forward, thoroughly studied, debated and discarded (if deficient) then further discussion using the same information that was previously examined and found incorrect (and barring a revision of the examining science itself) would be a distracting waste of time. In that case, then yes, censorship would be appropriate. For example, flat Eartherism.

    But to get to that point, free discussion of the idea needs to be allowed in the first place.

  24. 74
    Hank Roberts says:

    a “science paper” is up there with an episode of InfoWars.

    Your sources are unreliable.

  25. 75
    Hank Roberts says:

    Russell: “This time, the taxpaying audience should demand NASA’s full bandwidth and the eye-popping resolution of an IMAX camera. For if we encounter anything not of this Earth on Mars …”
    https://vvattsupwiththat.blogspot.com/2018/01/what-swell-planet-it-is.html

    Nicely said. Yeah, as long as it’s not going to be looking at Earth as Triana/DSCOVR does, funding for a good imaging system could be possible.

  26. 76
    Radge Havers says:

    @ ~ 72

    Indeed. Looking at a map of metropolitan areas and how much space they occupy, in terms of impact on the record, I wonder if they couldn’t be thought of more as a human ecosystem — say on the scale of fossil reefs. Corals, even tiny forams and fusies, can leave a fairly significant footprint. So an analogy to how few species survive in the record may not be apt.

    (Imagine finding an outcrop of medical waste and cement overshoes off the coast of Mesozoic New Jersey…)

  27. 77
    John Newlands says:

    I doubt a civilisation with language and relics of machines could have occurred as early as the Silurian ~400 mya. I think it was necessary to go through the steps fossil fuels –> metals–> electricity concurrently with anatomical evolution of the dominant species. The first step of accumulating significant burnable carbon didn’t occur until the Permo-Triassic ~250 mya. Electronics all happened in the last 100 years.

    A precursor to the fossil fuel step may be a billion years of algal photosynthesis to build up atmospheric oxygen in which to burn that buried carbon. Those conditions may apply to other planets which need to get the balance of water, sunlight and geology just right as on Earth. Could be why nobody has called or maybe they did all that then self destructed. That’s a more fruitful area for speculation.

  28. 78
    Russell says:

    75: Chill Hank-

    Le Chef Satellite Frog- the ESA Copernicus, Sentinel keeps the public orbital eye on Pruitt’s back yard.

  29. 79
    Brian Dodge says:

    I’m fairly sure that if a single generation of bass fishermen had existed when the Green River formation was being deposited, there would be empty beer cans, fishing gear, aluminum anchors, and delicately preserved imprints of MAGA hats among the other fossils. https://www.google.com/search?q=green+river+formation+fossils&source=lnms&tbm=isch&sa=X&ved=0ahUKEwidlqXZjs_aAhWQ0FMKHQ7aCRoQ_AUICigB&biw=1500&bih=722
    What would one find from an ancient garbage barge dumping into the back arc basin that became the Hunsruck Slate?
    Given the ubiquity of clay, I think it likely that ceramics would be an early development of any technological civilization, and they are robust and inert enough to survive in many metamorphic and some igneous environments.
    https://www.researchgate.net/publication/280737464_Palaeomagnetic_analysis_on_pottery_as_indicator_of_the_pyroclastic_flow_deposits_temperature_New_data_and_statistical_interpretation_from_the_Minoan_eruption_of_Santorini_Greece
    Ceramic tableware, bricks, clay tiles, et cetera should be long lasting indicators of technology development starting with the use of fire; the oldest known pottery dates back ~20000 years.

  30. 80
    Radge Havers says:

    @ ~ 77

    Hmm… Steampunk Dinos?

  31. 81
    Russell says:

    Brian Dodge says:
    22 Apr 2018 at 11:22 PM
    if a single generation of bass fishermen had existed when the Green River formation was being deposited, there would be empty beer cans… Given the ubiquity of clay, I think it likely that ceramics would be an early development of any technological civilization, and they are robust and inert enough to survive in many metamorphic and some igneous environments

    This is apt, as the mightily metamorphosed Green River formation contains natural silicon carbide SiC- the mineral moissanite.

    That bizarre outcrop of fossil carborundum may have inspired my old-school petrology professor to introduce his course with the words:
    “Rocks are just ceramics that happen to have been made by God.”

  32. 82
    Hank Roberts says:

    One of my favorite unwritten science fiction stories describes how our alien overlords encouraged coal mining to eliminate interesting fossil strata. Those big coal-stripping machines don’t leave much evidence behind.

    http://www.slate.com/articles/health_and_science/coal/2012/11/coal_mine_fossils_paleontology_shows_us_past_climate_change.html

  33. 83
    Martin Smith says:

    We have paleo evidence that dinosaurs were thriving in a high CO2 warmer world. They would have become intelligent, eventually, were it not for an asteroid collision. So maybe the reptilian evolution pathway is more likely than the mammalian one, and then it is more likely that intelligent life in other star systems will be intelligent dinosaurs.

    If they needed another planet to save their race, earth would be a good prospect. All they would have to do to make it suitable for their race would be to encourage us to burn more fossil fuels, add CO2 and methane to the atmosphere, and wait.

    We are being terraformed by reptilian aliens. They are already among us.

  34. 84
    Chris Machens says:

    #82 Hank, “One of my favorite unwritten science fiction stories describes how our alien overlords encouraged coal mining to eliminate interesting fossil strata.”

    Plot of the 1996 film The Arrival https://en.wikipedia.org/wiki/The_Arrival_(1996_film)

    The film starts with NCAR climatologist Ilana Green (Lindsay Crouse) examining a poppy field and remarking that it “shouldn’t be here”. It is revealed that the poppy field is in the middle of the Arctic.

    Zane Zaminsky (Charlie Sheen), a radio astronomer working for SETI, discovers an extraterrestrial radio signal from Wolf 336, a star 14 light years from Earth. Zane reports this to his supervisor, Phil Gordian (Ron Silver) at the NASA Jet Propulsion Laboratory (JPL), but Phil dismisses the claims. Zane soon finds that he has been fired because of supposed budget cuts, and blacklisted, preventing him from working at other telescopes. Taking a job as a television satellite installer, he creates his own telescope array using his customers’ dishes in the neighborhood, operating it secretly from his attic

    The very different looking aliens are able to disguise themselves with an external skin to infiltrate human society. Zane finds that all of the bases expel large amounts of greenhouse gas into the atmosphere.

    #

    A small alien crew, might find it entertaining to infiltrate our society to make sure we are gone or in chaos once the mothership arrives at stardate 48k!!

  35. 85
    Chris Machens says:

    1988 cult film https://en.wikipedia.org/wiki/They_Live The aliens control Earth as they have other planets in the past; they deplete each planet’s resources and destroy its environment before moving on to others.

    According to some comment, terraforming Earth with global warming. Have yet to watch this one.

  36. 86
    Russell says:

    The real question for Gavin is:
    Is the Silurian hypothesis Silurian?

    Cool as the cartoon of bipedal dinosaurs pushing baby carriages may be, the sad fact is that reptiles didn’t evolve until the Carboniferous– over a hundred million years later.

    Unless of course, you believe the Earth was created 6,021 years ago, in which case the dinosaurs should have shown up in time to enliven the Trojan War.

  37. 87
    Daniel Vallstrom says:

    I enjoyed the short story a lot. The different time lines were fine. There was a typo in it, a duplicated word — “grep -E -o -n ‘\b([a-zA-Z-]+) \1\b’ ” gives back “31:back back”.

    Typos in the paper:

    “estimating of the number”

    “i.e. Pagani” should be “e.g. Pagani”.

    “consider of events”

    Missing end parenthesis for “(asteroid”.

    “it may be just be a part”

    ((‘and/or’ means the same as ‘or’.))

    Comments and questions:

    The Drake equation, with its R*, is the equivalent of estimating enrolled college students. It seems to me that that is not quite what one wants and that this could be improved upon. But you would know this better already. See [a] for such an improvement, but maybe there are others?

    A long, vague, and probably unconvincing note on the idea of the self-perpetuating civilizations loop:

    The note that “Large-scale anoxia, in effect, might provide a self-limiting but self-perpetuating feedback of industry on the planet” is appealing. Elsewhere you also note that “the generality of [the human] pathway for other industrial species is totally unknown”. I’d argue that this is likely false:

    More than 100 years ago we could have foreseen that CO2 pollution could cause problems, and should have taken action already then. (Svante Arrhenius laid out the basic mechanisms of CO2 pollution in the late 19th century. We then could have noted that CO2 pollution was tied to GDP, maybe linearly (which Arrhenius maybe even did?). So with exponential economic growth (which you get from yearly growth) there would likely be a problem.)

    Even being as slow as we have been won’t, with very high probability, bring about civilization ending consequences.

    Furthermore, there wouldn’t have needed to be a general awareness in order to take action and get a head-start in tackling CO2 pollution. E.g. the Scandinavian countries, perhaps the Netherlands, maybe New Zealand, should long ago have taken action, knowing that their future citizens would be content to pay any accrued debt, because of societal and ethical progression.[b]

    And, arguably, because of e.g. evolution and game theory, the same holds for all civilizations.[c]

    References:
    [a] https://www.centauri-dreams.org/2018/02/16/mistakes-in-the-drake-equation/
    [b] https://www.researchgate.net/publication/322539162_How_to_Live
    [c] https://www.researchgate.net/publication/315082483_What_Advanced_Civilizations_Are_Like_and_Why_We_Don't_See_Them

  38. 88
    Radge Havers says:

    Leaving aside loose talk of dinosaurs and the generalized use of ‘Silurian’ to refer to any prehistoric, industrialized civilization, let us for a moment examine the original Silurian in its fully developed phase:

    https://upload.wikimedia.org/wikipedia/en/8/8c/Silurian2.jpg

    You will no doubt recognize features reminiscent of modern Oxudercinae. Furthermore note the texture of the skin which is not unlike that occasionally found in certain members of the Anura order. This has led to a rethinking of the pace of evolution among megafaunal species around the time of the Silurian-Devonian boundary. While much is still poorly understood about conditions that could account for such accelerated development, new discoveries of glazed ceramic pottery from that period have driven academics of mercurial disposition into paroxysms of wild theorization. While we don’t condone such unseemly behavior, we can certainly understand and perhaps even sympathize with it to a limited extent.

    We will discuss these developments in greater detail in later posts after several lengthy digressions into turbidity flows of the early Cenozoic and the formation muddy sludge casts of what are believed to be early troll dens.

  39. 89
    Dan DaSilva says:

    27 James Cross
    So do you see a mechanism for the formation of the first cell? That to me is a higher hurdle than complex life. Or do you consider life with cells to be complex?

  40. 90
    Dan DaSilva says:

    87 Daniel Vallstrom
    “Even being as slow as we have been won’t, with very high probability, bring about civilization ending consequences.” You are fast approaching a position which could get you lumped into a group of people who you may not want to be identified with. However, this is a very accurate statement.

  41. 91

    #87, 90–

    Even being as slow [to mitigate] as we have been won’t, with very high probability, bring about civilization ending consequences.

    Mmm. I’d like to see that formally demonstrated, as my opinion is that the knowledge base to make that determination doesn’t yet exist, and won’t for a very long time, if ever.

    We don’t really know in depth how our own society works, economically, socially, and politically, and our ignorance of the pan-Terran ecosystem is orders of magnitude deeper than that. But we are poking at the machinery of both in an extremely reckless manner. We understand some, but not all, of the first order consequences of climate change, and even a few second order ones (say, the oft-quoted idea that in terms of the military and political security environment, climate change is a ‘threat multiplier.’) As to third order consequences, not a clue, and as to the interactions of the consequences we do know about, we’re little better off.

    (For a relatively non-dire-sounding example, how will the loss of most of the world’s coral reefs affect the UN, the WTO and other international bodies, and what will the macroeconomic effects be around the world? And what will the security effects be? Will future populists be putting bans on travel to, and immigration from, littoral nations, for example? And what would such actions mean in terms of adapting to, and mitigating to the extent still possible, climate change and other forms of environmental degradation, bearing in mind that such actions are necessarily international in scope? Don’t know? Me, either, and neither does any scholar of such things; all we can do, basically, is write qualitative scenarios, perhaps buttressed by some limited qualitative modeling.)

    We do, however, have quite a few examples of past societies being thoroughly undone by regional climate change or ecological disruption (often human-induced), so we know to a certainty that that is a possible outcome. Quite a few folks feel that our technologically-advanced society would be more robust; they may be right, but I’m not persuaded of that, since virtually all members of that society are far more dependent on the artificial systems we’ve built than in the past, and hence far more vulnerable to disruptions thereto.

    And not only that, but we’re simultaneously setting up unprecedented disruptions of the natural systems that remaining traditional or quasi-traditional societies depend upon. (Probably the leading example is the Inuit and other Arctic people, who often still depend to a surprising degree on traditional lifeways–but whose profound practical knowledge of the environment is becoming ever less relevant to current conditions.) The civilizational survival challenge is thus being increased across the entire technological spectrum occupied by human societies.

    So, the assurance felt by Daniel and Dan on this topic seems to me misplaced. I sure hope they are right, just as I hope that the Curry-Lewis lowball ECS estimate–as reiterated in a recent paper getting a lot of play by the ‘lukewarmer’ crowd–is correct. But, famously, ‘hope isn’t a plan.’

  42. 92
    Russell says:

    As climate warriors write more science fiction than they are given credit for, perhaps Gavin’s story will inspire a primeval tale of Green dinosaurs committed to staving off The 0.6th Extinction.

    It could be parsed as a Pangaean Affairs article by an editorial collective of ammonites critical of the elitist vertibrate policy debate between coprolite carbon sequestration advocates, and radical therapods demanding more tree fern peatbeds to fuel posterity’s struggle to power through Snowball Earth episodes in epochs to come.

    https://vvattsupwiththat.blogspot.com/2013/01/annals-of-expeditionary-climatology.html

  43. 93
    nigelj says:

    Dan De Silva @89

    Here’s a suggested mechanism for the development of the first cells from New Scientist.

    https://www.newscientist.com/article/dn17987-how-life-evolved-10-steps-to-the-first-cells/

    Some ideas on how mitochondria developed:

    http://bioscience.jbpub.com/cells/MBIO1322.aspx

  44. 94
    nigelj says:

    “Even being as slow as we have been won’t, with very high probability, bring about civilization ending consequences.”

    We are changing the climate, but remember we are also going through mineral resources very fast, population is still exploding near exponentially, we are altering the entire landscape and biosphere of the planet often in destructive ways, and loading up future generations with huge levels of financial debt, all at the same time, and within a very short time period of human history.

    This is a collection of multiple simultaneous pressures unprecedented in human history, pressures that all interact and reinforce each other in mostly negative ways. Worse still, some nations are retreating into nationalism at a time when we need global cooperation and more social order and empathy not less.

    We don’t know enough to quantify collapse scenarios accurately, but modern society is “loading the dice” towards the collapse of civilisation.

  45. 95
    Daniel Vallstrom says:

    Kevin McKinney, #91, that claim that you quote is based on common estimates, with uncertainties, of emissions and its consequences. For answers to questions you pose, see e.g. the references in the references I gave. You also underappreciate what ‘civilization ending’ mean.

  46. 96
    Daniel Vallstrom says:

    Nigelj, #94, the discussion was about CO2 pollution. Regardless, the references in the references I gave, and the one below, also cover the new things that you brought up.

    Population growth rate is falling since around 1970. The number of children has stopped increasing. Population will stop increasing fairly soon. E.g. the recent [i] reviews population estimates. Or see the references in the references I gave.

    This talk of “unknown”, in Kevin McKinney’s #91, in nigelj’s #94, and possibly even to some extent in the Schmidt and Frank paper, borders philosophical nonsense, as in “things are unknown, therefor CERN experiments must stop because they might cause a black hole that will eat Earth”.

    [i] From Bottleneck to Breakthrough: Urbanization and the Future of Biodiversity Conservation, Eric W Sanderson Joseph Walston John G Robinson,
    https://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biy039/4976422

  47. 97
    James Cross says:

    #89 Dan

    I think the various theories around hydrothermal vents are the best explanations for origin of life. Nigelj has a link to one of these theories. All evidence is this occurred not that long in geological time after the Earth cooled sufficiently to allow it to happen. So, although it still is and maybe always will be a mystery, it happened in a much shorter time than it took to establish complex life which required almost 4 billion years. But then after we have relatively complex life (by this I mean worms, for example) a whole series of additional evolutionary events had to occur to create a big brained primate with appendages that can manipulate the environment to the extent humans do.

  48. 98
    James Cross says:

    An interesting side question.

    If fossils of anatomically modern humans can be found from 200-300 thousand years ago, why didn’t a technological civilization develop during the Eemian interglacial?

  49. 99
    Russell says:

    Is Gavin aware that President Trump has endorsed The Silurian Hypothesis on camera?

    Here’s the television interview.

  50. 100

    JC 98,

    My best guess is that there was never a long enough interglacial for agriculture to be an effective cultural pattern, until the present very long interglacial.

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