Speaker 1: Hey, welcome to Stuff to Blow Your Mind. My name
Speaker 1: is Robert Lamb and I'm Joe McCormick, and it's Saturday.
Speaker 1: Time to dig into the vault for an older episode
Speaker 1: of the show. This is our episode on the Silurian hypothesis,
Speaker 1: originally published January. I hope you enjoy Welcome to Stuff
Speaker 1: to Blow Your Mind production of My Heart Radio. Hey,
Speaker 1: welcome to Stuff to Blow Your Mind. My name is
Speaker 1: Robert Lamb and I'm Joe McCormick, and today we're going
Speaker 1: to be talking about a subject that I've actually had
Speaker 1: on the radar for a while. This is something that
Speaker 1: was making the rounds on science blogs a few years back,
Speaker 1: and it has been suggested by a number of different listeners.
Speaker 1: So I'm glad we're finally coming around to it. I
Speaker 1: think I had some hesitation for a while that I
Speaker 1: want to briefly explain right at the beginning here. But
Speaker 1: today we're gonna be talking about an idea known as
Speaker 1: the Silurian hypothesis. Uh. And just to give you a
Speaker 1: little bit of background knowledge, we spent several minutes before
Speaker 1: recording today trying to look up how they pronounced silurian
Speaker 1: on Doctor Who because I was like, sure they might
Speaker 1: use some kind of British English variation where they say Silurian,
Speaker 1: but but a last we could not ever get the
Speaker 1: doctor to say it right. I watched I think, an
Speaker 1: entire scene where one of the more recent doctors was
Speaker 1: chatting with a Silurian or Silurian out out of your Will,
Speaker 1: and they they it was like they were trying not
Speaker 1: to say it, like if they said it, one would
Speaker 1: would pop up and and crawl out of the screen
Speaker 1: or something. Uh they used they referred to another alien race.
Speaker 1: There wasn't even in the scene, and I don't even
Speaker 1: think was part of that episode. And then in all
Speaker 1: these other terms, but yeah, they were just trying to
Speaker 1: mess with me. So this is a topic that I
Speaker 1: have been interested in covering for quite a while. It's
Speaker 1: it's been a few years now, but Rob, when you
Speaker 1: suggested it, I realized that I'd always been hesitating and
Speaker 1: not wanting to quite go ahead with it. And I
Speaker 1: think I realized the reason for that, which is that
Speaker 1: when I saw people mentioning this paper on the internet,
Speaker 1: it was clear to me that a lot of them
Speaker 1: were getting exactly the wrong takeaway from it, Like they
Speaker 1: were latching onto a very shallow understanding of the concept
Speaker 1: and and running off in a in a very different
Speaker 1: direction than the authors intended. Not only a different direction
Speaker 1: than they intend, but a direction they specifically say do
Speaker 1: not go in, and specifically say that they are not
Speaker 1: trying to to make yeah. Uh So, to to clarify
Speaker 1: what we're talking about here, the Silurian hypothesis paper begins
Speaker 1: with a fascinating question, in the words of the author's quote,
Speaker 1: if an industrial civilization had existed on Earth many millions
Speaker 1: of years prior to our own era, what traces would
Speaker 1: it have left and would they be detectable today? That
Speaker 1: that's the question at the heart of this paper. And
Speaker 1: obviously this is a tantalizing premise. You know, it sets
Speaker 1: your mind racing with images of impossibly weird organisms, you know,
Speaker 1: like land dwelling octopi and stuff in the in their
Speaker 1: own weird cities, and and what kind of technology would
Speaker 1: they have? Things that are as alien as anything you
Speaker 1: could imagine on another planet, except they would have all
Speaker 1: been from here, native to planet Earth, dating back millions
Speaker 1: of years into prehistory. But while this is a really
Speaker 1: attractive imaginative exercise, I think the first order of business
Speaker 1: when talking about this subject is to be clear that
Speaker 1: the Silurian hypothesis paper is about coming up with a
Speaker 1: framework for detecting physical traces of industrial civilizations and understanding
Speaker 1: how long those traces last. So it's about trying to
Speaker 1: say what are the right questions to ask when you're
Speaker 1: when you're looking at a planet and saying, how could
Speaker 1: we tell if there had been a civilization on this
Speaker 1: planet a long time ago. It is not a paper
Speaker 1: arguing that there was in fact a lost civilization deep
Speaker 1: in Earth's past. So it's not evidence for lizardman, ancient aliens,
Speaker 1: Graham Hancock, Junk Atlantis, or any of that stuff. But
Speaker 1: I would say in its true form, it is a
Speaker 1: really interesting question. Yeah, and at hard this episode is
Speaker 1: is not going to be about scientific evidence for lizardman
Speaker 1: civilizations in the Hollow Earth. So if you're looking for that,
Speaker 1: this is this is not the episode for you. But yeah,
Speaker 1: what I love about it is that it takes this
Speaker 1: sort of fantastic idea and then examines it reasonably, and
Speaker 1: that examination illuminates some very interesting geologic, climatic and astrophysical considerations. So,
Speaker 1: you know, setting aside pseudoscience and pseudo archaeology here. But
Speaker 1: on the other hand, I think if you if you're
Speaker 1: looking for some sci fi fund this topic in this episode,
Speaker 1: well also still engage you. Um. But it is interesting
Speaker 1: how from a certain perspective you can imagine people being
Speaker 1: drawn into it by just sort of this sci fi idea,
Speaker 1: this idea that does lean lend itself well to sort
Speaker 1: of conspiracy theorist mindsets, and then realizing actually, this paper
Speaker 1: is about geology and uh and uh and in the
Speaker 1: last year of our planet and also uh, I guess
Speaker 1: kind of you know, in many cases, kind of a
Speaker 1: downbeat message about the lasting impact of human technology on
Speaker 1: our planet. And on the other hand, too, how forgettable
Speaker 1: we may be from the standpoint of geological history. Yeah,
Speaker 1: so if you're on board for all of that, you've
Speaker 1: come to the right place. So real quick, I do
Speaker 1: want to just discuss the Doctor Who reference here, since
Speaker 1: since uh the author's Schmidt and Frank took the name
Speaker 1: for the hypothesis from the Doctor Who species the Silurians
Speaker 1: who first popped in the nineteen seventies series Doctor Who,
Speaker 1: and these Silarians, I think now you've got me saying Silarians. Oh,
Speaker 1: I'm sorry, I'm probably well. It gets even worse because
Speaker 1: so they take the name of the hypothesis from this
Speaker 1: Doctor Who series where these creatures show up. But then
Speaker 1: they say explicitly in the paper, you know, the range
Speaker 1: we would really be looking at would actually be after
Speaker 1: the Silurian geologic periods. Silurian period is something that's like
Speaker 1: a roughly twenty million year period. That's more than four
Speaker 1: hundred million years ago. I don't know, it's like four
Speaker 1: hundred and forty something to four hundred and twenty something,
Speaker 1: I think roughly. But if you were seriously looking for
Speaker 1: evidence of lost civilizations in Earth's ancient past, you'd probably
Speaker 1: be looking for things like after about four hundred million
Speaker 1: years ago, coming you know, forward in time from the
Speaker 1: Devonian period, when you could have the reasonable biological basis
Speaker 1: for land dwelling animals that might have evolved complex technological intelligence. Yes, uh,
Speaker 1: but at any rate. In Doctor Who, especially in that
Speaker 1: original nineteen seventy uh appearance, the Silurians are these kind
Speaker 1: of lizard men um. They factor into this plot with
Speaker 1: the Third Doctor played by John Perkway who lived nineteen
Speaker 1: nine six, and then they subsequently pop up again with
Speaker 1: the fifth Doctor played by Peter Davison and the eleventh
Speaker 1: Doctor played by Matt Smith, and then more recently the
Speaker 1: third teenth Doctor played by Jody Whittaker. So this is
Speaker 1: just the TV show. I can't speak to the various
Speaker 1: books and audio dramas that have come out, and their
Speaker 1: look has changed throughout the film. Um. You know, they are,
Speaker 1: in essence, this cold blooded, prehistoric reptile like species with
Speaker 1: significant technological advancement that they I think they end up
Speaker 1: entering various states of suspended animation to avoid uh you know,
Speaker 1: major changes on Earth, changes to the climate, etcetera. Um,
Speaker 1: and then they re emerge and encounter the Doctor. Um.
Speaker 1: So yeah, they're They're one of the many interesting alien
Speaker 1: and otherworldly species that pop up. Uh. Though I guess
Speaker 1: with the Silurians one of the key things is that
Speaker 1: they're they're not pure aliens. They're they're sort of the originals.
Speaker 1: There are their original terrans, original earthlings, uh, that are
Speaker 1: then encountered by these evolved apes that come much later.
Speaker 1: I mean to to them, we are the aliens, yeah, right,
Speaker 1: were like these weird future creatures. Uh the image you
Speaker 1: would tell And I gotta be honest, I'm not a hoovoid,
Speaker 1: so I don't know the lore. But the picture you're
Speaker 1: showing me of the Silurians, they look like they look
Speaker 1: like if the world was all creature from the Black
Speaker 1: Lagoon and there was a leather face of the creature
Speaker 1: from the Black Lagoon civilization. Yeah. I mean, they're definitely
Speaker 1: Doctor Who creatures of this era, which which I tend
Speaker 1: to love these costumes. I know they were working with
Speaker 1: with with with budget limitations here, but yeah, the the
Speaker 1: aliens and robot of this era really really called me. Now.
Speaker 1: You said they look kind of fish like. Bear in mind,
Speaker 1: and I'm sure some Doctor Who listeners Doctor Who viewers
Speaker 1: will will will chime in here. But I believe they
Speaker 1: are related to another species that pops up on the
Speaker 1: show that live in the water. I think they're like
Speaker 1: the sea devils or something. Um, but these guys are
Speaker 1: not aquatic in nature. I think I got that right.
Speaker 1: The seed of Oh wait, this is that like a
Speaker 1: bunch of intelligent euryptorids or something something like that. Yeah, alright,
Speaker 1: so this is two thousand eighteen paper, the Silurian hypothesis.
Speaker 1: Would it be possible to detect an industrial civilization in
Speaker 1: the Geological Record. This was published in the journal International
Speaker 1: Journal of Astrobiology. UH. It draws its name from that
Speaker 1: Doctor Who episode, and the authors here that they point
Speaker 1: out that they may be the first to seriously consider
Speaker 1: whether a technologically advanced civilization could have evolved prior to
Speaker 1: Homo sapiens on Earth, though the authors due stress that
Speaker 1: this is a to the best of the knowledge situation,
Speaker 1: So you know, it's entirely possible somebody was batting around
Speaker 1: the idea of previously, but this may be the first,
Speaker 1: and certainly this was this one really made a splash
Speaker 1: when it came out. Okay, So the two authors here
Speaker 1: would be Adam Frank and Gavin A. Schmidt right and
Speaker 1: Frank is a is a physicist and astronomer, and Schmidt
Speaker 1: is a climate scientist right right. Schmidt is a climatologist,
Speaker 1: climate model and director of the NASA Goddard Institute for
Speaker 1: Space Studies in New York and co founder of the
Speaker 1: award winning climate science blog Real Climate. Frank is a physicist, astronomer,
Speaker 1: and writer whose work has appeared in such publications as
Speaker 1: The New York Times and NPR. And I believe we've
Speaker 1: actually referenced his work on the podcast before. Uh. He
Speaker 1: also has a book. He has a few books, including
Speaker 1: The Constant Fire, The End of the Beginning, and Light
Speaker 1: of the Stars. Those are all nonfiction science books, of course.
Speaker 1: So to be clear, we're talking about two very legitimate
Speaker 1: scientists and science communicators, not you know, not a couple
Speaker 1: of of quacks who were staring into the hollow Earth
Speaker 1: or anything. So the authors here begin with a very
Speaker 1: reasonable consideration of the search for intelligent life elsewhere in
Speaker 1: the universe. Uh. And then this is something we've we've
Speaker 1: touched on the show plenty of times before. Ours is
Speaker 1: the only model of life, but we generally consider technological
Speaker 1: advancement to be a hallmark of intelligent life. And more
Speaker 1: to the point, something we can search for signs of, uh,
Speaker 1: concerning other worlds and other star systems. Uh. You know,
Speaker 1: and anytime you can you can figure out how to
Speaker 1: look for signs of of advanced and expansive energy harvesting
Speaker 1: or consumption. That might be a way for us to
Speaker 1: tell if there's something else out there that is significantly advanced, right,
Speaker 1: and it also might be a simple prerequisite for contact
Speaker 1: because uh, they're talking about so that They started off
Speaker 1: by looking at this as an astrobiology question. You know,
Speaker 1: you're you're looking for signs of life elsewhere in the universe,
Speaker 1: and of course, the the search for intelligent life in
Speaker 1: the universe, in practical terms, what's accessible to us, really
Speaker 1: boils down to the search for life capable of Harvard
Speaker 1: harnessing radio technology within our galaxy. You know, you could
Speaker 1: probably find maybe chemical biosignatures in in the atmospheres of
Speaker 1: exoplanets that would give you an indication that there's some
Speaker 1: kind of life there, maybe bacterial in nature or whatever.
Speaker 1: But if you're looking for intelligent life, you're you're probably
Speaker 1: talking about radio of some kind, right, And so the
Speaker 1: kinds of civilizations that develop radio communication technology would fall
Speaker 1: under the classification of industrial civilizations. And these are what
Speaker 1: author the authors define as civilizations that have the ability
Speaker 1: to harness energy on a global scale. And they bring
Speaker 1: up how this actually feeds into one of the the
Speaker 1: recurring characters in in the astrobiology literature, the Drake equation.
Speaker 1: That's right, Yeah, they bust out the Drake equation, and
Speaker 1: of course consider how how some of the takeaways relate
Speaker 1: to Earth, especially the notion that over the course of
Speaker 1: a planet's existence, multiple industrial civilizations can fear radically arise
Speaker 1: over the span of time that life exists there, And
Speaker 1: then we have to factor in questions over you know,
Speaker 1: how many times life itself may have evolved or started
Speaker 1: out on Earth before our last universal common ancestors got going,
Speaker 1: the possibility of a shadow biosphere, and the idea that
Speaker 1: species like dolphins may suggest independent evolutions of intelligence on Earth. Um,
Speaker 1: you know, so we're left with this idea that, yeah, theoretically,
Speaker 1: given the footprint of life on Earth, you could have
Speaker 1: had multiple intelligences uh evolved and arise during that time period.
Speaker 1: Because that's certainly what the Drake equation UH seems to
Speaker 1: allow for concerning other worlds. Well, yeah, and I you know,
Speaker 1: so I kind of love the Drake equation. You know,
Speaker 1: it's a famous tool that I really enjoy thinking about
Speaker 1: because because it does the job of taking a question
Speaker 1: that seems like we could not possibly answer it. The
Speaker 1: question is how many active technological civilizations are there in
Speaker 1: the Milky Way galaxy? And you know, if you're being
Speaker 1: honest with yourself, the correct answer to that is how
Speaker 1: the hell should I know? Like, there's no way to
Speaker 1: answer that question at all. But what the Drake equation
Speaker 1: does is break that unanswerable question down into a number
Speaker 1: of other questions that you then multiplied together to get
Speaker 1: an estimated number. And many of those smaller questions themselves
Speaker 1: could perhaps be answered, and in fact, some of them
Speaker 1: have been answered since the Drake equation was first formulated.
Speaker 1: Uh So, So it decomposes an unsolvable problem of are
Speaker 1: there aliens out there? And if so, how many, into
Speaker 1: a series of smaller problems, at least some of which
Speaker 1: are solvable, maybe all of which are. You know, you
Speaker 1: could come up with some kind of reasonable guess about.
Speaker 1: And so the classic formulation of the Drake equation is
Speaker 1: to get your number of civilizations in in the Milky way,
Speaker 1: you would multiply a bunch of different terms together. So
Speaker 1: one is the rate of average the average rate of
Speaker 1: star formation. You know, how much do you get stars
Speaker 1: times the fraction of stars that have planets times the
Speaker 1: average number of planets per star times the fraction of
Speaker 1: planets that develop life times the portion of those life
Speaker 1: systems that gain intelligence, times the portion of those intelligent
Speaker 1: life systems that develop technological means to communicate times And
Speaker 1: then here's a really interesting term, quote the length of
Speaker 1: time l over which such civilizations released detectable signals. And
Speaker 1: it's this very last term that I think very often
Speaker 1: gets overlooked by people who are thinking about, you know,
Speaker 1: are there aliens out there, and how could we know?
Speaker 1: I think we often tend to assume that, well, once
Speaker 1: there are aliens with technological means to communicate, that's just
Speaker 1: like a you know, progress only extends from their civilizations
Speaker 1: just continue to get bigger and their capabilities expand, and
Speaker 1: they spread out from there. But I don't know that
Speaker 1: there could be severe limitations on the length of a
Speaker 1: radio receptive or radio broadcasting civilist nation. Maybe they only
Speaker 1: exist for a few hundred years. Because one thing we
Speaker 1: know is that our technological civilization is just a tiny
Speaker 1: blip on the history of planet Earth, even a tiny
Speaker 1: blip on the history of life on planet Earth. Earth
Speaker 1: is four point five billion years old. There's been life
Speaker 1: on Earth for most of that time. Uh. The authors
Speaker 1: here estimate that there has been complex life on Earth's
Speaker 1: land surface for only about four hundred million years, So
Speaker 1: that's only a fraction of the entire history of Earth.
Speaker 1: But that but four hundred million years is still a
Speaker 1: gargantuan amount of time compared to the length of human civilization.
Speaker 1: They say, industrial civilization, you know, by their metric, has
Speaker 1: probably existed for only about three hundred years. This is
Speaker 1: since roughly the beginning of mass production methods for for things.
Speaker 1: And so if humans were wiped out by a global
Speaker 1: mass extinction of some kind in the near future, our
Speaker 1: industrial civilization would just be this tiny little splinter, this
Speaker 1: blip of three hundred years on a history of a
Speaker 1: currently four point five billion year old planet. Yeah, and
Speaker 1: so from there we get into the question, Okay, if
Speaker 1: if you have an industrial civilization like this it is
Speaker 1: just a blip, would we be able to see it?
Speaker 1: And if we could see it, what would we look for?
Speaker 1: And this is you know, this is pretty much the
Speaker 1: meat of the paper here analyzing this sort of question,
Speaker 1: which which is great because it again it gets into
Speaker 1: sort of uh, you know, sci fi friendly concepts. It's
Speaker 1: a useful in considering the evolution of life and the
Speaker 1: existence of intelligent life on other worlds. And it also
Speaker 1: shines a light on what we're doing now and where
Speaker 1: we are and and I think also, uh, you know,
Speaker 1: illustrates nicely illustrates this idea that um that that the
Speaker 1: technology is not just this um that this this this
Speaker 1: ramp to Star Trek, you know, or this ramp to
Speaker 1: the culture or any of our more optimistic sci fi
Speaker 1: dreams like there are there are severe challenges. Uh. And
Speaker 1: of course there's there's always the risk of extinction. That's
Speaker 1: exactly right. And one thing that's funny is we don't
Speaker 1: know whether the rise of technological civilization should generally be
Speaker 1: understood as, on average, a linear process where it just
Speaker 1: sort of goes in one direction and keeps going in
Speaker 1: that direction, or whether it should be understood as, on
Speaker 1: average a cyclical process where you get a rise in
Speaker 1: technological civilization and then it disappears for some reason. You
Speaker 1: can imagine what some of those reasons might be, um,
Speaker 1: and uh, and then maybe rises again out of the
Speaker 1: out of the same biosphere. I mean. Either one I
Speaker 1: think is is a perfectly plausible model to entertain is
Speaker 1: like what usually happens in the universe. Uh. And we
Speaker 1: just don't have the Uh, we don't have the evidence
Speaker 1: to really have an opinion on that. Yeah, I mean
Speaker 1: a lot of it just comes back to the fact
Speaker 1: that again we are the only model of intelligent life
Speaker 1: and certainly technologically advanced tech, um, intelligent life that we
Speaker 1: have to look at. So we have nothing to compare
Speaker 1: us to. Yeah, and we don't know what's going to
Speaker 1: happen to us in the long run, right, So, uh, well,
Speaker 1: let's get into the I guess the sort of the
Speaker 1: first part of the paper. And I do want to
Speaker 1: drive home that if you want to just go right
Speaker 1: to the paper yourself and dive in. Um, you just
Speaker 1: do a search for the title and you can find
Speaker 1: it hosted on NASA. They have a NASA has a
Speaker 1: has a PDF of this that's very easily accessible. Uh.
Speaker 1: You can also read it in full on the Cambridge
Speaker 1: University Press website, which I think is the press behind
Speaker 1: the journal, the International Journal Journal of Vester Biology. And yeah,
Speaker 1: so it's all on their end with the references hyperlinked
Speaker 1: and all that, which is nice. Yes, yeah, absolutely so
Speaker 1: if you hit a paywall, don't don't give up. It's
Speaker 1: out there. Um. And I believe Adam Frank also wrote
Speaker 1: a piece for What the Atlantic where he nicely summarizes
Speaker 1: some of the ideas here. Oh yeah, and he also
Speaker 1: tells a funny story about how they arrived at writing
Speaker 1: the paper because I think he says, uh, he showed
Speaker 1: up in Gevin Schmidt's office to talk about UM, to
Speaker 1: talk more about astrobiology, like Drake equation type questions, and
Speaker 1: he's like, okay, so we we we know we've got
Speaker 1: one industrial civilization on Earth. And then Schmidt responded by saying,
Speaker 1: how do we know we're the only one? I think
Speaker 1: just hitting that early like wall, They're like wow, And
Speaker 1: then that turned into the paper, Yeah, and it's it's
Speaker 1: it's quite a paper. Thank So let's see, let's get
Speaker 1: into the first part of it, which I think you
Speaker 1: can loosely think of it's just sort of a look
Speaker 1: at the limits of our vision. So they point out
Speaker 1: that for the last two point five million years, uh,
Speaker 1: there's widespread physical evidence of things like climate change, soil horizons,
Speaker 1: this is where one layer of soil differs from Belower above,
Speaker 1: speaking to changes recorded in the soil, as well as
Speaker 1: archaeological evidence of non Homo sapiens cultures such as the Neanderthals.
Speaker 1: And this two point five million year period is known
Speaker 1: as the Quaternary. Now, going back before the Quaternary again
Speaker 1: more than two point five million years ago, the land
Speaker 1: evidence is harder to come by. You have to depend
Speaker 1: on drilling, mining, and occasional exposed sections of the earth.
Speaker 1: Even in the ocean sentiment evidence apparently only goes back
Speaker 1: to around one seventy million years ago. Yeah, And I
Speaker 1: think for me this was actually one of the most
Speaker 1: interesting parts of the paper because I would say, if
Speaker 1: you just go by standard intuition, a person might think, uh,
Speaker 1: you know, if there had been a civilization on Earth,
Speaker 1: you know, a two million years ago or something like that. Uh,
Speaker 1: would wouldn't that just be completely obvious, Like we'd see
Speaker 1: evidence of it all around us. Would there be ruins
Speaker 1: and all that, you know, their their stone hinges, their
Speaker 1: skyscrapers and everything like that. Actually it's not. It might
Speaker 1: not be as obvious as you might think. In fact,
Speaker 1: the evidence of it could be rather scarce. And this
Speaker 1: runs counter to our side five imaginings, right, because when
Speaker 1: you encounter elder civilizations and in other works like there's
Speaker 1: usually some sort of a ruin or a vault or
Speaker 1: some sort of mysterious monolith or something like the idea
Speaker 1: that the elders would just be gone entirely, like just erased,
Speaker 1: not by some sort of a conspiracy or by some
Speaker 1: sort of a you know, alien shenanigans. But just because
Speaker 1: things don't last that long, that's a it's an alien
Speaker 1: concept from too many of our again, too many of
Speaker 1: our creative visions of of what the future in the past,
Speaker 1: maybe exactly so we think, well, you know, there are
Speaker 1: ruins of civilizations from thousands of years ago, but that's
Speaker 1: thousands of years ago. That's nothing in geological time. The
Speaker 1: surface of the I mean, look a look at what
Speaker 1: a map of the land formations on Earth just you know,
Speaker 1: sixty million years ago looked like it's like, you know,
Speaker 1: the the surface of the Earth is not fixed and constant.
Speaker 1: This is a geologically active planet. So would there be
Speaker 1: ruins all around us with evidence of a civilization from
Speaker 1: hundreds of millions of years ago just be totally obvious?
Speaker 1: I think I probably by the answer that the authors
Speaker 1: give here, which is that no, it would probably not
Speaker 1: be totally obvious. In fact, it might be incredibly difficult
Speaker 1: to find evidence of at all. Uh. And so one
Speaker 1: of the the interesting points the authors make here is
Speaker 1: that the the exposed land surface of Earth, of course,
Speaker 1: is geologically very young on average. They cite evidence from
Speaker 1: a study by Mattman at All in two thousand nine
Speaker 1: that the oldest large patch of land surface on Earth
Speaker 1: is probably in the Negev Desert, and that's only about
Speaker 1: one point eight million years old. At one point eight
Speaker 1: million years, I mean, compared to the history of civilization,
Speaker 1: is a long time. But that's again, it's like nothing
Speaker 1: in geological times, a tiny fraction of of Earth history.
Speaker 1: So if we wanted to find remnants of a civilization
Speaker 1: from say, hundreds of millions of years ago, you probably
Speaker 1: would not find that on the surface of the Earth.
Speaker 1: You'd have to look for it in in exposed geological
Speaker 1: strata from from previous eras. And even then you can't
Speaker 1: just count on the fact that you would be finding
Speaker 1: fossils of that civilization all over the place. Yeah, exactly.
Speaker 1: That they that they had done something we you've discussed
Speaker 1: in the show before, which is of course that the
Speaker 1: fossil record is inherently incomplete, because fossilization only occurs when
Speaker 1: conditions are just right. Um. They point out that that
Speaker 1: of all the dinosaurs that ever lived, and there were
Speaker 1: a ton of you know, uh, you know, they're the
Speaker 1: era of the dinosaurs taken as as one gigantic, gigantic
Speaker 1: monolith just dwarfs anything that that that that humanity has
Speaker 1: ever occupied. Uh. You know, it is a it is
Speaker 1: a cathedral, and and we're we're not even like a
Speaker 1: child's dollhouse, uh sort of situation here. Um. So, uh,
Speaker 1: you know, out of out of all of those dinosaurs
Speaker 1: that ever lived, there are only a few thousand near
Speaker 1: complete specimens. And so the authors here contend that given
Speaker 1: the rarity of fossilization, a species is short lived, as
Speaker 1: Homo sapiens m not make it into the fossil record
Speaker 1: at all. And of course, for fossilization to mean anything
Speaker 1: to us or to you know, anybody who's doing and doing,
Speaker 1: you know, some sort of an investigation of a planet
Speaker 1: or our planet, those fossilizations would have to survive and
Speaker 1: then they would have to be found. Yeah, exactly. And
Speaker 1: so again this might be pushing against your intuition. You
Speaker 1: would say, like, wait a minute, there's there's there's there's
Speaker 1: signs of human life all over the surface of Earth.
Speaker 1: And and we have you know, at least a few thousand,
Speaker 1: uh complete dinosaur fossils, enough to have museums of Natural
Speaker 1: history with dinosaur fossils in places all over the world. Uh,
Speaker 1: surely you'd expect more. But dinosaurs existed for almost two
Speaker 1: hundred million years. Human civilization again is like it's a
Speaker 1: few thousand years at this point. Yeah. So the problem
Speaker 1: here is like we have trouble comparing the odds because
Speaker 1: you're not realizing how many millions of times more the
Speaker 1: dinosaur bodies got to roll the dice than our cors would. Yeah. Absolutely.
Speaker 1: Another thing they touch on is that is the example
Speaker 1: of technology. Uh, and they point out how rarely complex
Speaker 1: early examples of human technology are ever found. So if
Speaker 1: you're thinking, well, surely we would find one of these
Speaker 1: factories or something that was made by one of these
Speaker 1: factories that a previous civilization might have had, well not necessarily. Yeah, sure,
Speaker 1: surely my rice cooker would be found hundreds of millions
Speaker 1: of years in the future. But yeah, that that they
Speaker 1: mentioned several reasons why that's maybe not as clear as
Speaker 1: you might assume. So they say urbanization that currently represents
Speaker 1: less than one percent of the Earth's surface, So that's
Speaker 1: a limitation on the deposition side of creating a fossil
Speaker 1: record of our current civilization. Only small parts of Earth's
Speaker 1: surface are actually inhabited by humans. That that sounds counterintuitive,
Speaker 1: but it's true. And then they point out that quote,
Speaker 1: exposed sections and drilling sites for pre quaternary surfaces are
Speaker 1: order of magnitude less as fractions of the original surface.
Speaker 1: So human civilization currently only feels a small portion of
Speaker 1: Earth's surface right now, and we only access tiny fractions
Speaker 1: of Earth's previous surface through through various kinds of drilling,
Speaker 1: and you know, access through exposure to rock strata. So
Speaker 1: there's just like extreme selection filters on both sides, on
Speaker 1: the deposition and on the excavation side. Yeah, it would
Speaker 1: be kind of like even if you knew somehow, with
Speaker 1: some certainty that there was that there was a technological
Speaker 1: civilization during this time and in the ancient ancient past,
Speaker 1: uh yeah, you would. You would have to you have
Speaker 1: to really know exactly where to drill down to hit them.
Speaker 1: You couldn't just expect to randomly do it unless you
Speaker 1: did a lot of drilling and digging and excavation. But
Speaker 1: but but so what we've been talking about here is
Speaker 1: challenging the the intuition that you would just be finding
Speaker 1: physical fossil remnants and artifacts of this civilization from hundreds
Speaker 1: of millions of years ago all over the place, and
Speaker 1: I think they do a very good job of knocking
Speaker 1: that down. But of course it is not hopeless, because
Speaker 1: they say, while our chance of finding the physical remains
Speaker 1: of a hypothetical Silarian civilization might be very low, there
Speaker 1: would be other traces of the existence of that civilization
Speaker 1: that would be preserved in the geologic record, and you
Speaker 1: you would have a very good chance of finding those traces. Yeah,
Speaker 1: and that's that's what most of the rest of the
Speaker 1: paper deals with. I do want to point out one
Speaker 1: other thing that they bring up in passing that I
Speaker 1: thought was interesting. They point out that that you could
Speaker 1: certainly make an argument for or against the evolution of
Speaker 1: intelligent life in a world based on the probable evolution
Speaker 1: of species that are in the fossil record, but that
Speaker 1: they would be focusing on physiochemical tracers for previous industrial civilization.
Speaker 1: So I hadn't really thought about this, but like the
Speaker 1: idea of like looking at say, dinosaur um fall souls
Speaker 1: and saying, well, we don't have evidence that they evolved
Speaker 1: in it into an intelligent technological species, but if we
Speaker 1: but we can make an argument based on this fossil
Speaker 1: and this fossil fossil that they were headed in that direction.
Speaker 1: I feel like even that's the kind of thing that
Speaker 1: probably wouldn't be quite as clear as your intuition might
Speaker 1: lead you to assign them, because I mean, like intelligence
Speaker 1: in mammals arose very rapidly in geologic time. Yeah, so
Speaker 1: again it reached this situation where the fossil record could
Speaker 1: just be missing that snapshot entirely. So this all leads
Speaker 1: you next to the next major question. Given the limits
Speaker 1: of what we can detect in the geochemical record, what
Speaker 1: exactly could we look for on a planet to see
Speaker 1: if an industrial society ever existed there? And yeah, that's
Speaker 1: what the bulk of the paper focuses on. So in
Speaker 1: the case of Earth, if an organized, intelligent society evolved
Speaker 1: during the pre Quaternary time but they didn't reach the
Speaker 1: level of an industrial society, there simply would be no
Speaker 1: heard off them as far as this paper is concerned.
Speaker 1: Right there, they're looking for the kinds of chemical material
Speaker 1: and climate type changes that would leave a trace in
Speaker 1: the geologic record, and that would primarily be a function
Speaker 1: of of industry, basically of energy production, of of material
Speaker 1: working things like metals and plastics, and the UH and
Speaker 1: the methods of harnessing energy for industrial use. I was
Speaker 1: reminded of our episodes on fire technology because if listeners
Speaker 1: may remember, we discussed well, could something that evolved in
Speaker 1: the water or or on a water world, could they
Speaker 1: ever really get any kind of advanced technology going if
Speaker 1: they didn't have access to the surface. And that seems
Speaker 1: to be a factor here as well, as they're only
Speaker 1: looking at the period during which something could have evolved
Speaker 1: on land. Yeah, so you could maybe have advanced intelligence
Speaker 1: in the water. But it's maybe this is just a
Speaker 1: lack of imagination on our party. You know, you always
Speaker 1: need to be aware of the limitation of your vision.
Speaker 1: But it does seem hard to imagine advanced technology under
Speaker 1: the water, because like, if you don't have fire, you
Speaker 1: can't do metal working, or metal working is very difficult.
Speaker 1: I don't I don't know. It just seems harder to
Speaker 1: imagine how technology like we understand it could come about
Speaker 1: in the water. But again, you know, limits of our vision. Yeah,
Speaker 1: so they say, quote, the focus is thus on the
Speaker 1: period between the emergence of complex life on land in
Speaker 1: the Devonian four million years ago in the Paleozoic era
Speaker 1: and the mid apply a scene. Uh, and that's around
Speaker 1: four million years ago. Yeah, because if it was much
Speaker 1: more recent, you you'd probably get into the area where
Speaker 1: you'd start to expect to actually see those kinds of
Speaker 1: remnants and artifacts that that we were talking about. Right,
Speaker 1: So they get into the discussion of what we might
Speaker 1: look for, and they have it nicely divided up. The
Speaker 1: first one is, uh, well, they basically have two broad
Speaker 1: categories and then some some details on that category. The
Speaker 1: first big one though, would be looking at the geological
Speaker 1: footprint of the anthroposcene. So, as we've discussed in the
Speaker 1: show before, there's an argument to be made that the
Speaker 1: impact of human civilization on the environment and the geologic
Speaker 1: record constitutes its own geologic era, the Anthropocene. So not
Speaker 1: all the changes would be recognizable millions of years later,
Speaker 1: but some would be. Right. So, human activity at this
Speaker 1: point is is large scale enough that we are making
Speaker 1: changes to the earth that that are that are widespread
Speaker 1: or you could even say global, and I was gonna
Speaker 1: say permanent, not permanent, but extremely long lived. You know,
Speaker 1: going way into the future, you will be able to
Speaker 1: find signs in the rocks and the ice and the settiment,
Speaker 1: you know, the things on Earth that persists over long
Speaker 1: periods of time that will leave records of what we
Speaker 1: did to the Earth in just the past three years
Speaker 1: or so. Right and uh, and as we've probably mentioned before,
Speaker 1: the anthroposcene is not a an official geological era, as
Speaker 1: much as any of these things can be, you know, officials.
Speaker 1: It seems like when you're talking about geologic terms, it's
Speaker 1: even more ridiculous. We can consider such a small part
Speaker 1: of geologic history that we occupy, but there's a lot
Speaker 1: of compelling evidence for it, and you often see it discussed,
Speaker 1: especially when we're talking about the changes that that humans
Speaker 1: have made to the planet and arem still making to
Speaker 1: the planet, and how they may show up in the
Speaker 1: geologic record. And just to be super clear, the majority
Speaker 1: of the changes we're talking about of this kind would
Speaker 1: not be changes like physical alterations of the Earth's surface.
Speaker 1: We're not talking about like records of people digging holes
Speaker 1: and building stuff. We're talking about records of like changes
Speaker 1: to the to the level of different carbon isotopes in
Speaker 1: in geological strata and things like that. Right now, they
Speaker 1: also hit upon something that that I thought was really
Speaker 1: interesting in in in a way almost almost encouraging, uh,
Speaker 1: the sustainability paradox. So the idea here is that, of
Speaker 1: course the longer human civilization lasts, especially technological civilization, the
Speaker 1: greater the geologic signal of its impact. Again, that that
Speaker 1: lasting those lasting signs in the environment, not the faces
Speaker 1: they carved into the mountains, but impacts again on their
Speaker 1: their geochemical in nature. Um, so that signal increases. But
Speaker 1: the longer human civilization lasts, the more sustainable it must
Speaker 1: become in order to survive. And this is of course
Speaker 1: the reality we're living in right now. If a civilization
Speaker 1: survives this test and becomes more sustainable, then that signal
Speaker 1: grows weaker. Right. So it's almost like the strength of
Speaker 1: the signal left for future people to discover is directly
Speaker 1: proportional to how suicidal that civilization is, right Like, the
Speaker 1: more it is just burning through fossil fuel resources and
Speaker 1: the rate of that, the stronger the signal will be.
Speaker 1: And so a civilization at some point, they say, well,
Speaker 1: will naturally tend to attenuate for a couple of reasons.
Speaker 1: Either it really says it can't keep going at that rate,
Speaker 1: or it's going to cause climate damage to itself, so
Speaker 1: it will naturally switch to more sustainable uh energy sources
Speaker 1: that are harder to detect in the future, or it
Speaker 1: of course does so much damage to itself that it's
Speaker 1: signal naturally is reduced, right right. So, so basically coming
Speaker 1: back to what you said earlier, it's not just that
Speaker 1: there there's gonna be a sign. There's gonna be the
Speaker 1: signal uh, this footprint of a civilization uh in the
Speaker 1: in the you know, the geochemical record. It's it's also
Speaker 1: that it may just be very short, it may be
Speaker 1: a little it's not going to be this Uh. It's
Speaker 1: not gonna be a symphony. It's going to maybe be
Speaker 1: a note or two. So basically the idea being that
Speaker 1: that that the real strong, much stronger argument for aliens
Speaker 1: existing and having some sort of role or some sort
Speaker 1: of advanced technology having some sort of role on Earth
Speaker 1: and they in the ancient history would not be look
Speaker 1: at the pyramids, I think aliens did this, or I
Speaker 1: think you know, ancient scientists did this. It would be
Speaker 1: pointing at say a blip and uh or an increase
Speaker 1: in global temperatures during a certain period of time and saying,
Speaker 1: I think the aliens did this? Or I think the
Speaker 1: advanced technology and question did this? I mean, even then,
Speaker 1: I think that would be a very speculative and and
Speaker 1: difficult to prove hypothesis. It would be kind of just
Speaker 1: like unfalsifiable speculation, but that that would perhaps be the
Speaker 1: more likely type of signal you would find if there
Speaker 1: had been alien intervention. Then you know, specific artifacts than
Speaker 1: al right, well, let's get into some of the specifics
Speaker 1: of the footprint that the authors lay out here. The
Speaker 1: first one is a stable isotope anomalies of carbon, oxygen, hydrogen,
Speaker 1: and nitrogen. And this is one of the big ones.
Speaker 1: An estimated point five trillion tons of fossil carbon via
Speaker 1: the burning of fossil fuels and warming of the planet
Speaker 1: um they quote, we we expect this temperature rise to
Speaker 1: be detectable and so FA ocean uh carbonates notably forminifera.
Speaker 1: This is a single celled organism with a with a
Speaker 1: with a chalky shell. UM. Organic biomarkers cave records, stuches
Speaker 1: such as stalactites, lake ostracods. These are minute aquatic crustaceans
Speaker 1: and high latitude ice cores, though only the first two
Speaker 1: of these will be retrievable in the time scales considered
Speaker 1: here un Right, So this thing about the the isotope
Speaker 1: anomalies of of carbon and these other elements is very interesting.
Speaker 1: So they say, you know, there are natural distributions that
Speaker 1: you would find records of in the different isotopes of
Speaker 1: carbon that are that are moving around in Earth's atmosphere.
Speaker 1: But when people suddenly start pulling huge amounts of fossil carbon,
Speaker 1: carbon of a biological origin out of the ground and
Speaker 1: burning it, you suddenly start throwing those isotopes out of whack,
Speaker 1: and that will be something that will leave records for
Speaker 1: millions of years to come. So you can look in
Speaker 1: the geological records, you know, the record of of strata
Speaker 1: from previous eras, and say hunh. For some reason, in
Speaker 1: this one period deep in history, suddenly the carbon isotopes
Speaker 1: got way out of whack, as if suddenly a bunch
Speaker 1: of fossil carbon like coal or oil or whatever had
Speaker 1: been burned at a at a hideous rate into the atmosphere. Right.
Speaker 1: And so you know, looking at our our time now
Speaker 1: of of of modern human civilization, you know this that
Speaker 1: we have this fossil fuel consumption and we have the
Speaker 1: invention of the haber Bosch process and the large scale
Speaker 1: use of of nitrogenous fertilizers and agriculture, which will also
Speaker 1: heavily impact the planet's nitrogen cycling. Yeah, the haber Bosch process, Yeah,
Speaker 1: as part of the changes in the nitrogen cycle that
Speaker 1: have come about as a result of of industrial civilization.
Speaker 1: As well. They also touched on sediment to logical records.
Speaker 1: The key causes here would be major soil erosion brought
Speaker 1: on by agriculture, but also by agriculture lated deforestation. Um. Now,
Speaker 1: this would be partially mitigated by dams, they point out,
Speaker 1: but erosion is also heightened by climate changes and thawing
Speaker 1: perma frost. Also sediment content changes due to just industrialization
Speaker 1: in general. Uh. Now here's a There's another big one
Speaker 1: that I think will be pretty obvious. Faunnel radiation and extinctions. Um. Basically,
Speaker 1: humans have brought about many extinctions already, and we're living
Speaker 1: in the midst of an extinction event. Uh. This will
Speaker 1: likely register in the fossil record. Yeah. Now, of course,
Speaker 1: previous major extinction events have usually been chalked up to
Speaker 1: two natural things like uh, oh, we can track massive
Speaker 1: vulcanisms as the cause of this one, or say a
Speaker 1: large space impact like the Katie extinction event. But there
Speaker 1: are other extinction events in Earth's history where the cause
Speaker 1: is not totally clear. You know, there are some speculations,
Speaker 1: but we don't know exactly why. Suddenly it seemed like
Speaker 1: there was a great reduction in marine biodiversity at this
Speaker 1: point in history. All right. The next area is non
Speaker 1: naturally occurring synthetics, So non naturally occurring chemicals generated by
Speaker 1: industrial activity that persists in the environment. Things persistent organic pollutants,
Speaker 1: chlorofluoral carbons, in related compounds. And they also point out
Speaker 1: that steroids, leaf waxes, alkanones, and lipids can be preserved
Speaker 1: in sediment for many millions of years. Now, that one
Speaker 1: naturally makes me think of King plastic baby. Yeah, yeah,
Speaker 1: And that's that's the next thing that they mentioned. And
Speaker 1: this one's you know, this one's disheartening but obvious. We've
Speaker 1: created tons of plastics, tons upon tons upon tons of plastics,
Speaker 1: and they sadly persist not only in heaps and floating masses,
Speaker 1: but inside the bodies of organisms, including ourselves, uh so quote.
Speaker 1: The potential for very long term persistence and detectability is high. Now.
Speaker 1: One of the things they point out about plastic that's
Speaker 1: interesting is that plastics may well proved to be a
Speaker 1: very long term signature of human civilization and the geologic
Speaker 1: record for you know, millions and millions of years to come.
Speaker 1: But the development of plastic is also something they would
Speaker 1: class under the I don't remember the umbrella term they
Speaker 1: use for this, but sort of chemical contingencies. A technological
Speaker 1: civilization does not have to use plastics. Plastics are just
Speaker 1: something that humans happen to use. There are other things
Speaker 1: that seem probably more universal, like almost any industrial civilization
Speaker 1: you would expect to burn lots of fossil fuels, But plastics,
Speaker 1: that's more of a question mark. Is that unusual that
Speaker 1: we did it, or is that a very common thing
Speaker 1: that the civilizations would do all right. The next area
Speaker 1: that they highlight transuranic elements. These are elements having a
Speaker 1: higher atomic number than uranium, which is ninety two. Most
Speaker 1: radioactive isotopes created via nuclear energy or weaponry have long
Speaker 1: half lives, but not long enough to be a factor
Speaker 1: on the time scale that they're talking about here. But
Speaker 1: the exceptions are plutonium to forty four and um curium
Speaker 1: two forty seven. So plutonium has a half life of
Speaker 1: eight point eight million years, and curium in this case
Speaker 1: we're talking about a half life of fifteen million years.
Speaker 1: So in sufficient quantities of disposal, these would these would
Speaker 1: pop up. And plutonium has no known natural causes outside
Speaker 1: of an actual supernova or something like that. This isotope
Speaker 1: of plutonium. Yes, this particularly yea plutonium two forty four
Speaker 1: so um. So, Yeah, if you found enough of this
Speaker 1: uh in the geologic record, that would be a sign
Speaker 1: that's that's something was at work, there was some sort
Speaker 1: of technological atomic uh enterprise that was in place. Now,
Speaker 1: I guess we've already mentioned earlier that the authors are
Speaker 1: not going to claim that there was in fact a
Speaker 1: a long lost civilization hundreds of millions of years ago.
Speaker 1: But they do actually look at the geologic record to say,
Speaker 1: are there anythings that that match these criteria we've been
Speaker 1: looking at, And they do find some interesting partial matches
Speaker 1: that have though of course nothing really comes close to
Speaker 1: evidence that would be conclusive that there actually was a civilization,
Speaker 1: but some of these matches raise interesting questions of their own. Yeah,
Speaker 1: they don't look at everything, and they point out that
Speaker 1: things like the kt extinction event. We know that that
Speaker 1: was not an industrial accident or anything. Um and uh
Speaker 1: and again they're not arguing that these are evidence of
Speaker 1: past pre human industrial civilizations on Earth, but merely point
Speaker 1: to them as the source of events we might look at. Yeah.
Speaker 1: And I would say the biggest one that they focus
Speaker 1: on in the paper is the event known as the
Speaker 1: Paleocene Eocene Thermal Maximum or p e t M. Yeah.
Speaker 1: This is an abrupt spike in carbon and oxygen isotopes
Speaker 1: near the Paleocene Eocene transition fifty six million years ago,
Speaker 1: resulting in a five to eight degree celsius global average
Speaker 1: temperature rise. This is widely thought to be due to well,
Speaker 1: I think they're there are different theories. One is that
Speaker 1: it's volcanic activity. Um. But there have also been hypotheses
Speaker 1: put forth that it could have been a common impact.
Speaker 1: It could be due to burning pete, methane being released,
Speaker 1: and a few other candidates. Um. It's also used as
Speaker 1: a means of of understanding and kind of like kind
Speaker 1: of modeling out the effects of climate change during our
Speaker 1: own era. Yeah. And and one of the reasons this
Speaker 1: one gets singled out is, uh, so it really looks like, Okay,
Speaker 1: here we're seeing, for example, these carbon isotope signature changes
Speaker 1: that would signal that huge amounts of biogenic carbon carbon
Speaker 1: that originally came from life forms, like the stuff you
Speaker 1: would find in fossil fuels, is being burned and released
Speaker 1: into the atmosphere. Now, how would that happen if if
Speaker 1: if it wasn't creatures from the Black Lagoon with leather
Speaker 1: face masks digging up a bunch of fossil fuels and
Speaker 1: burning them for their civilization. Well, no, you probably don't
Speaker 1: need to jump to that conclusion because there are other
Speaker 1: solutions on off for like, for example, there might have
Speaker 1: somehow been lots of access of volcanic magma two beds
Speaker 1: of fossil fuels. Maybe certain types of volcanic activity tended
Speaker 1: to set a light to a lot of natural reserves
Speaker 1: of fossil fuels and shale beds and things like that.
Speaker 1: And this almost acted as if the Earth itself, we're
Speaker 1: we're setting off an industrial revolution, but it was just
Speaker 1: volcanoes interacting with with these reservoirs of carbon in the ground. Yeah,
Speaker 1: all you need is geologic upheaval and volcanic activity and
Speaker 1: again um our Our planet has A has A has
Speaker 1: a very active geological life, so there's plenty of opportunity
Speaker 1: for this sort of thing to potentially have taken place.
Speaker 1: So it kind of comes back to a problem with
Speaker 1: the signal here, the signal you would be looking for
Speaker 1: in the geochemical record. In many cases, the very sort
Speaker 1: of signal we're looking for, especially concerning carbon and warming,
Speaker 1: could have also been caused by these naturally occurring causes,
Speaker 1: and so strong signals might be coming from something else,
Speaker 1: and more specific signals that we might look to just
Speaker 1: might be too weak to to ever possibly observe or
Speaker 1: to really make much out of. Oh yeah, this is
Speaker 1: an interesting paradox they talk about in their conclusion of
Speaker 1: all of the criteria they're able to come up with
Speaker 1: in this framework for for looking for past industrial civilizations,
Speaker 1: the stuff that you would expect any industrial civilization to
Speaker 1: do also has other explanations, and so so it's not
Speaker 1: conclusive that it was an industrial civilization that this would
Speaker 1: be things like you know, the carbon stuff. Meanwhile, the
Speaker 1: stuff that would be really strong evidence of an intelligent
Speaker 1: civilization origin, that stuff that civilizations might not do. It's
Speaker 1: more contingent things like plastics, and stuff. You know, you
Speaker 1: could have a civilization without plastics. That's not a necessary
Speaker 1: milestone in the in the progress of energy harnessing. And
Speaker 1: maybe it's even the sort of thing. Uh an advance
Speaker 1: civilization would move away from coming back to that the
Speaker 1: sustainability paradox, when one could hope, I imagine. Now the
Speaker 1: authors again, they're very clear about just how far you
Speaker 1: should take this hypothesis, stating that quote, the Silurian hypothesis
Speaker 1: cannot be regarded as likely merely because no other valid
Speaker 1: idea presents itself. Uh So they admit that this this
Speaker 1: sort of thing could easily get out of hand with
Speaker 1: folks pointing to any sort of signal in the geochemical
Speaker 1: record as being possible proof of pre human technological societies.
Speaker 1: If you're doing that, you're really taking it and running
Speaker 1: with it in the wrong direction. Yeah, I guess that's
Speaker 1: one of the frustrating things about about interesting work of
Speaker 1: this kind is so you can point out a lot
Speaker 1: of the ways that it's difficult to rule out past civilizations.
Speaker 1: But then for a lot of people who just want
Speaker 1: to have a theory that changes everything, you know, for
Speaker 1: a lot it's just like it's fun to believe that.
Speaker 1: So a lot of people just want to believe it.
Speaker 1: I want to believe, you know, that there was an
Speaker 1: Atlantis mother civilization that birthed everything, or I want to
Speaker 1: believe that there were alien on Earth before humans or
Speaker 1: anything like that, because that would change everything, and it
Speaker 1: feels so cool to believe it. Therefore becomes your default belief.
Speaker 1: And so thus a paper that says, well, it's more
Speaker 1: difficult to rule out that kind of thing than you
Speaker 1: might think. Uh, some people can erroneously conclude that that
Speaker 1: is in fact evidence for the thing they want to
Speaker 1: believe because it feels cool. It's not positive evidence for it, yes, yeah, absolutely,
Speaker 1: um yes, So so you know, they argue that that
Speaker 1: we need to to further research, you know, the likely
Speaker 1: signature left by our own um anthroposyne era, as well
Speaker 1: as a deeper exploration of the elemental and um compositional
Speaker 1: anomalies that we find in extant sediments. Basically, we look
Speaker 1: at past events mainly with stuff like impacts in mind,
Speaker 1: but perhaps the Silarian hypothesis needs to be at least
Speaker 1: on the table as well. Not because again we think
Speaker 1: it is, you know, actually a valid explanation for what
Speaker 1: has happened. Um, you know, ultimately it's an outside possibility,
Speaker 1: not a conclusion we should jump to, but perhaps it
Speaker 1: should just be part of sort of the spectrum of
Speaker 1: possibilities there. Again, not because we think it happened, but because,
Speaker 1: uh it gives us a little more of a sort
Speaker 1: of a robust spectrum and how to interpret these things.
Speaker 1: And and then moving forward to you know, potentially considering
Speaker 1: other worlds, looking at other planets like even Mars. Uh
Speaker 1: it gives us one more tool, one more uh way
Speaker 1: to look at the evidence. Yeah, exactly, they're not arguing
Speaker 1: this because they think there was a civilization. It's that
Speaker 1: we should consider these possibilities when looking at planets, even
Speaker 1: including our own, and know what we would look for
Speaker 1: if we wanted to consider that possibility, right, Yeah, because
Speaker 1: ultimately this is not a supernatural explanation. This is ultimately,
Speaker 1: you know, a natural hypothesis. But but it is admittedly
Speaker 1: an outside possibility. Now, of course we're here talking about
Speaker 1: reasons why you shouldn't just jump to the conclusion of
Speaker 1: a Silurian civilization, but but there are also some arguments
Speaker 1: against it in some of the specific events that they
Speaker 1: look at. For example, if you know, maybe the best
Speaker 1: possibility is this interesting event in Earth history, the Paleocene
Speaker 1: Eocene thermal maximum. More suddenly there was there was rapid
Speaker 1: global warming and UH and these in these chemical changes
Speaker 1: like with carbon isotopes. They even put some arguments back
Speaker 1: against considering UH civilization as a cause of this global
Speaker 1: warming in Earth's history, because they say, look, the kind
Speaker 1: of global warming caused by our civilization is happening in
Speaker 1: an incredibly rapid fashion over just a few hundred years.
Speaker 1: This actually, though it's it's relatively rapid in geologic terms.
Speaker 1: The the p et M actually happened probably over hundreds
Speaker 1: of thousands of years, which which is incredibly slow if
Speaker 1: you're imagining that civilization was the cause of it, right,
Speaker 1: if you're if you're comparing it to the model of
Speaker 1: of human industrial advancement, it's incredibly slow. So there's not
Speaker 1: only the point that you shouldn't just jump to the
Speaker 1: conclusion of there was a law civilization because it feels cool,
Speaker 1: but like in the specific instances they look at, there
Speaker 1: are some reasons for thinking that's probably not true. I
Speaker 1: don't know, I guess unless those civilizations were like just
Speaker 1: really lazy, Yeah, I mean, you can sort of, you know,
Speaker 1: pull out your sci fi hat and and put it
Speaker 1: on and come up with various ideas of you know,
Speaker 1: for why they might have been this way. Maybe they
Speaker 1: were super long lived. Yeah, they weren't very ambitious, and
Speaker 1: they're like this, note, this is the right level of industrialization,
Speaker 1: and we want to, uh, we need to keep going
Speaker 1: at this rate. I don't know. They didn't reproduce all
Speaker 1: that much. I don't know. I mean that that's ultimately
Speaker 1: one of the problems with with imagining uh, you know,
Speaker 1: other life forms. It's like it's just you know, it's
Speaker 1: you can you can make a case for any number
Speaker 1: of things, um and and try and make it fit
Speaker 1: your your hypothesis. And of course that's not really the
Speaker 1: way to go about it. I mean, not in from
Speaker 1: a scientific perspective, from a sci fi dreaming creative perspective. Yeah,
Speaker 1: go for it, um though, though I guess it does
Speaker 1: kind of come down to the conundrum two at the
Speaker 1: end of the day, like like when does when does
Speaker 1: mere creativity and um and dream weaving become this kind
Speaker 1: of corruption of our thought and uh and and a
Speaker 1: pollution of our ability to understand our place in the
Speaker 1: world and are where we're going in the future and
Speaker 1: where we were in the past. Well, you know, I
Speaker 1: feel like a thread without maybe intending intending to do so.
Speaker 1: That we've pursued A good bit on this podcast is
Speaker 1: understanding the ideally, the difference between your sort of interest
Speaker 1: and imagination and your epistemology. That like that an idea.
Speaker 1: You can like an idea because it's interesting and cool,
Speaker 1: and that doesn't necessarily mean it's true. You know that,
Speaker 1: like that, your your epistemology is probably best to based
Speaker 1: on evidence, and you should be skeptical of things that
Speaker 1: you want to believe because you like them and so forth.
Speaker 1: But it's still totally valid to, like, say, be interested
Speaker 1: in the bicameral mind or whatever because it's a fun idea,
Speaker 1: even if you know, you probably accepted as you know,
Speaker 1: there's not a lot of evidence for it, right right,
Speaker 1: You can you can altomly engage in a number of
Speaker 1: these ideas as as more as art than science, and
Speaker 1: there's certainly nothing wrong with that. Is when you start
Speaker 1: arguing that your art is science, that's where you can
Speaker 1: get into into some trouble. Um. I was reminded in
Speaker 1: all of this of Carl Sagan's approach to ancient aliens
Speaker 1: and ancient astronauts, particularly in the book that he co
Speaker 1: authored with Joseph Shklovsky, Intelligent Life in the Universe. Um.
Speaker 1: In this particular book, you know, they they examine this idea.
Speaker 1: They said, Okay, here's the speculative idea, and we don't
Speaker 1: have evidence that had ever happened. But if it were
Speaker 1: to have happened, what sorts of specific evidence might we
Speaker 1: look for? And in this case, we're talking about science
Speaker 1: ends that are evident in ancient religions and uh and
Speaker 1: so forth. Uh. And I thought that was a great
Speaker 1: treatment of that question. Uh. And against Sagan's treatment reminds
Speaker 1: me of the treatment given in this paper by these authors.
Speaker 1: But of course Segand had to come back and continue
Speaker 1: to argue with the ancient alien people who were, you know,
Speaker 1: very much going off in their own director is true, ye, yeah,
Speaker 1: and pushing pushing art as science, and Sagan having to
Speaker 1: remind them like, no, I love art as much as
Speaker 1: the next guy, but here's how we approach this from
Speaker 1: a scientific perspective. Well, I mean, I think the important
Speaker 1: thing about this stuff, like Sagan's work on that or
Speaker 1: or or the paper we're looking at here is it's
Speaker 1: good too when you're when you're exploring it like a
Speaker 1: tantalizing and juicy idea. It's a good idea to have
Speaker 1: criteria for what would be good evidence of such a
Speaker 1: thing before you're actually looking at individual evidence in cases,
Speaker 1: because if you look at the evidence first and then
Speaker 1: you try to come up with criteria, you're gonna have
Speaker 1: a tendency to want to fit your criteria or whatever
Speaker 1: evidence you've already got. The cherry picking model or what
Speaker 1: is it the other name of the barn wall fallacy
Speaker 1: or something like that. Remember, the idea is like, you know,
Speaker 1: somebody says, you know, I'm a great shot, and so
Speaker 1: they shoot at the side of a barn, and then
Speaker 1: they go up, they walk up to their bullet hole,
Speaker 1: and then they draw a bulls eye perfectly around it.
Speaker 1: That's that's a great point. That's that's a great way
Speaker 1: of looking at it. All Right, Well, I guess we're
Speaker 1: gonna go ahead and wrap this episode up. But we'd
Speaker 1: love to hear from everyone out there. I love to
Speaker 1: hear from any doctor who fans who have some additional
Speaker 1: information they want to share about the Silurians. And various
Speaker 1: related um species that have popped up in that show.
Speaker 1: And perhaps you have specific thoughts about about you know,
Speaker 1: just this this basic you know view, uh, and what
Speaker 1: it reveals about humanities uh place on Earth right now,
Speaker 1: and what technological civilization is doing to the planet, and
Speaker 1: just you know, ultimately, what kind of a you know,
Speaker 1: a small lip a week signal we may be in
Speaker 1: the future as opposed to this kind of lasting thing
Speaker 1: that we sometimes imagine that human civilization is. I'm going
Speaker 1: to say, I hope that I'll be optimistic, so I
Speaker 1: hope we do stick around. I hope we attenuate the
Speaker 1: kinds of geologic signal we leave due to climate change,
Speaker 1: in chemical alteration of the atmosphere and all you know
Speaker 1: stuff like that, uh, you know, heavy metal pollutions and things,
Speaker 1: and that we the signal of our civilization can always
Speaker 1: be charted against the geologic record because of the continuance
Speaker 1: of Doctor Who Seasons. So when we're on the like,
Speaker 1: you know, eventually we'll get into the exponential notation of
Speaker 1: the Doctor who Seasons. Yeah yeah, yeah. Well, one day
Speaker 1: some sort of ancient uh or rather some sort of
Speaker 1: far flung future civilization will look back and say, look,
Speaker 1: clearly they knew what they were doing. Uh, they were
Speaker 1: able to do you know, some three million years of
Speaker 1: doctor who though maybe at a certain point the doctor
Speaker 1: will be a robot and the enemy, as will be
Speaker 1: will be organics. And I don't know, Yeah, I wonder
Speaker 1: at what point do we get a robot doctor. I mean,
Speaker 1: they they're they've only recently really been been been mixing
Speaker 1: up the casting on that role. All right, Well, let
Speaker 1: us know in the meantime, if you want to listen
Speaker 1: to other episodes of Stuff to Blow Your Mind, we
Speaker 1: have core episodes on Tuesdays and Thursdays and the Stuff
Speaker 1: to Blow Your Mind podcast feed. On Monday's we do
Speaker 1: listener mail, where we hear from from you, the listeners,
Speaker 1: and we we read your various listener mails, always a
Speaker 1: good time. On Wednesday's we do a short form artifact
Speaker 1: or monster fact, and then on Fridays we do Weird
Speaker 1: How Cinema. That's our time to set aside most serious
Speaker 1: issues and just talk about a weird film. Huge thanks
Speaker 1: as always to our excellent audio producer Seth Nipolis Johnson.
Speaker 1: If you would like to get in touch with us
Speaker 1: with feedback on this episode or any other to suggest
Speaker 1: topic for the future, or just to say hello. You
Speaker 1: can email us at contact that Stuff to Blow Your
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