Speaker 1: Welcome to Stuff to Blow Your Mind, the production of
Speaker 1: My Heart Radio. Hey, welcome to Stuff to Blow Your Mind.
Speaker 1: My name is Robert Lamb, and I'm Joe McCormick. And
Speaker 1: today we're going to be talking about a subject that
Speaker 1: I've actually had on the radar for a while. This
Speaker 1: is something that was making the rounds on science blogs
Speaker 1: a few years back, and it has been suggested by
Speaker 1: a number of different listeners. So I'm glad we're finally
Speaker 1: coming around to it. I think I had some hesitation
Speaker 1: for a while that I want to briefly explain right
Speaker 1: at the beginning here. But today we're gonna be talking
Speaker 1: about an idea known as the Silurian hypothesis. Uh. And
Speaker 1: just to give you a little bit of background knowledge,
Speaker 1: we spent several minutes before recording today trying to look
Speaker 1: up how they pronounced Silurian on Doctor Who, because I
Speaker 1: was like, sure they might use some kind of British
Speaker 1: English variation where they a Silurian, but but a last
Speaker 1: we could not ever get the doctor to say it right.
Speaker 1: I watched I think an entire scene where one of
Speaker 1: the more recent doctors was chatting with us Silurian or
Speaker 1: Silurian out out of your will, and they they it
Speaker 1: was like they were trying not to say it, like
Speaker 1: if they said it, one would would pop up and
Speaker 1: and crawl out of the screen or something they used
Speaker 1: they referred to another alien race. There wasn't even in
Speaker 1: the scene, and I don't even think was part of
Speaker 1: that episode. And then in all these other terms. But yeah,
Speaker 1: they were just trying to mess with me. So this
Speaker 1: is a topic that I have been interested in covering
Speaker 1: for quite a while. It's it's been a few years now,
Speaker 1: But Rob, when you suggested it, I realized that I'd
Speaker 1: always been hesitating and not wanting to quite go ahead
Speaker 1: with it. And I think I realized the reason for that,
Speaker 1: which is that when I saw people mentioning this paper
Speaker 1: on the internet, it was clear to me that a
Speaker 1: lot of them were getting exactly the wrong takeaway from it,
Speaker 1: Like they were matching onto a very shallow understanding of
Speaker 1: the concept and and running off in a in a
Speaker 1: very different direction than the authors intended. Not only a
Speaker 1: different direction than they intend, but a direction they specifically
Speaker 1: say do not go in, and specifically say that they
Speaker 1: are not trying to to make Yeah. Uh, so to
Speaker 1: to clarify what we're talking about here. The Silurian Hypothesis
Speaker 1: paper begins with a fascinating question, in the words of
Speaker 1: the author's quote, if an industrial civilization had existed on
Speaker 1: Earth many millions of years prior to our own era,
Speaker 1: what traces would it have left and would they be
Speaker 1: detectable today? That that's the question at the heart of
Speaker 1: this paper. And obviously this is a tantalizing premise. You know,
Speaker 1: it sets your mind racing with images of impossibly weird organisms,
Speaker 1: you know, like land dwelling octopi and stuff in the
Speaker 1: in their own weird cities, and and what kind of
Speaker 1: technology would they have? Things that are as alien as
Speaker 1: anything you could imagine on another planet, except they would
Speaker 1: have all been from here, native to planet Earth, dating
Speaker 1: back millions of years into prehistory. But while this is
Speaker 1: a really attractive imaginative exercise, I think the first order
Speaker 1: of business when talking about this subject is to be
Speaker 1: clear that the Silurian Hypothesis paper is about coming up
Speaker 1: with a framework for detecting physical traces of industrial civilizations
Speaker 1: and understanding how long those traces last. So it's about
Speaker 1: trying to say, what are the right questions to ask
Speaker 1: when you're when you're looking at a planet and saying,
Speaker 1: how could we tell if there had been a civilization
Speaker 1: on this planet a long time ago? It is not
Speaker 1: a paper arguing that there was in fact a lost
Speaker 1: civilization deep in Earth's past. So it's not evidence for
Speaker 1: lizard men, ancient aliens, Graham Hancock, junk Atlantis, or any
Speaker 1: of that stuff. But I would say in its true form,
Speaker 1: it is a really interesting question. Yeah, And at heart
Speaker 1: this episode is is not going to be about scientific
Speaker 1: evidence for lizard men civilizations in the Hollow Earth. So
Speaker 1: if you're looking for that, this is this is not
Speaker 1: the episode for you. But yeah, what I love about
Speaker 1: it is that it takes this sort of fantastic idea
Speaker 1: and then examines it reasonably, and that examination eliminates some
Speaker 1: very interesting geologic, climatic, and astrophysical considerations, So you know,
Speaker 1: setting aside pseudoscience and pseudo archaeology here. But on the
Speaker 1: other hand, I think if you if you're looking for
Speaker 1: some sci fi fund this topic in this episode will
Speaker 1: also still engage you. Um, but it is interesting how
Speaker 1: from a certain perspective you can imagine people being drawn
Speaker 1: 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 U and the last
Speaker 1: year of our planet and also, oh, I guess kind
Speaker 1: of you know, in many cases, kind of a downbeat
Speaker 1: message about the lasting impact of human technology on our planet.
Speaker 1: And on the other hand, too, how forgettable we may
Speaker 1: be from the standpoint of geological history. Yeah, so if
Speaker 1: you're on board for all of that, you've come to
Speaker 1: the right place. So real quick, I do want to
Speaker 1: just discuss the Doctor Who reference here, since since uh,
Speaker 1: the authors Schmidt and Frank took the name for the
Speaker 1: hypothesis from the Doctor Who species the Silurians, who first
Speaker 1: popped up in the nineteen seventies series Doctor Who. And
Speaker 1: these Silurians, I think, now you've got me saying silurians,
Speaker 1: I probably probably stuff this way. Well, it gets even
Speaker 1: worse because so they take the name of the hypothesis
Speaker 1: from this Doctor Who series where these creatures show up.
Speaker 1: But then they say explicitly in the paper, you know,
Speaker 1: the range we would really be looking at would actually
Speaker 1: be after the Lurian geologic period, the Silurian period is
Speaker 1: something that's like a roughly twenty million year period that's
Speaker 1: more than four hundred million years ago. I don't remember.
Speaker 1: It's like four hundred and forty something to four hundred
Speaker 1: and twenty something, I think roughly. But if you were
Speaker 1: seriously looking for evidence of lost civilizations in Earth's ancient past,
Speaker 1: you'd probably be looking for things like after about four
Speaker 1: hundred million years ago, coming you know, forward in time
Speaker 1: from the Devonian period, when you could have the reasonable
Speaker 1: biological basis for land dwelling animals that might have evolved
Speaker 1: complex technological intelligence. Yes, but any rate. In Doctor Who,
Speaker 1: especially in that original nineteen seventy uh appearance, the Silurians
Speaker 1: are these kind of lizard men um. They factor into
Speaker 1: this plot with the third Doctor played by John part
Speaker 1: Way Who nineteen nine, nine ninety six, and then they
Speaker 1: subsequently pop up again with the fifth Doctor played by
Speaker 1: Peter Davison and the eleventh Doctor played by Matt Smith,
Speaker 1: and then more recently the third teenth Doctor played by
Speaker 1: Jody Whittaker. So this is just the TV show. I
Speaker 1: can't speak to the various books and audio dramas that
Speaker 1: have come out, and their look has changed throughout the film. Um,
Speaker 1: you know, they are, in essence, this cold blooded, prehistoric
Speaker 1: reptile like species with significant technological advancement that they they
Speaker 1: I think they end up entering various states of suspended
Speaker 1: animation to avoid uh you know, major changes on Earth,
Speaker 1: changes to the climate, etcetera. Um, and then they re
Speaker 1: emerge and encounter the Doctor. Um. So yeah, they're They're
Speaker 1: one of the many interesting alien and otherworldly species that
Speaker 1: pop up. Uh. Though, I guess with the Silurians, one
Speaker 1: of the key things is that they're they're not pure aliens.
Speaker 1: They're they're sort of the originals. There are their original terrans,
Speaker 1: original earthlings, uh, that are then encountered by these evolved
Speaker 1: apes that come much later. I mean to to them,
Speaker 1: we are the aliens. Yeah right, we're these weird future creatures. Uh.
Speaker 1: The image would tend And I gotta be honest, I'm
Speaker 1: not a hoovoid, so I don't know the lore. But
Speaker 1: the picture you're showing me of the Silurians, they look
Speaker 1: like they look like if the world was all creature
Speaker 1: from the Black Lagoon and there was a leather face
Speaker 1: of the creature from the Black Lagoon civilization. Yeah, I
Speaker 1: mean they're definitely Doctor Who creatures of this era, which
Speaker 1: which I tend to love these costumes. I know they
Speaker 1: were working with with with with budget limitations here, but yeah,
Speaker 1: the the aliens and robots of this era really really
Speaker 1: called me. Now you said you look kind of fish like.
Speaker 1: Bear in mind, and I'm sure some Doctor Who listeners
Speaker 1: Doctor Who viewers will will will chime in here, But
Speaker 1: I believe they are related to another species that pops
Speaker 1: up on the show that live in the water. I
Speaker 1: think they're like the sea devils or something. Um, but
Speaker 1: these guys are not aquatic in nature. I think I
Speaker 1: got that right. The seed of Oh wait, this is
Speaker 1: that like a a bunch of intelligent euryptorids or something
Speaker 1: something like that. Yeah, alright, So this is two thousand
Speaker 1: eighteen paper the Silurian hypothesis, Would it be possible to
Speaker 1: detect an industrial civilization in the Geological Record? This was
Speaker 1: published in the journal International Journal of Astrobiology. UH. It
Speaker 1: draws its name from that Doctor Who episode, and the
Speaker 1: authors here that they point out that they may be
Speaker 1: the first to seriously consider whether a technologically advanced civilization
Speaker 1: could have evolved prior to Homo sapiens on Earth, though
Speaker 1: the authors due stress that this is a to the
Speaker 1: best of their knowledge situation, so you know, it's entirely
Speaker 1: possible somebody was batting around the idea previously, but this
Speaker 1: may be the first, and certainly this was. This one
Speaker 1: really made a splash when it came out. Okay, So
Speaker 1: the two authors here would be Adam Frank and Givin A.
Speaker 1: Schmidt right and Frank is a is a physicist and astronomer,
Speaker 1: and Schmidt is a climate scientist right right. Schmidt is
Speaker 1: a climatologist, climate model and director of the NASA Gotted
Speaker 1: Institute for Space Studies in New York and co founder
Speaker 1: of the award winning climate science blog Real Climate. Frank
Speaker 1: is a physicist, astronomer, and writer whose work has appeared
Speaker 1: in such publications as The New York Times and NPR,
Speaker 1: and I believe we've actually referenced his work on the
Speaker 1: podcast before. Uh. He also has a book. He has
Speaker 1: a few books, including The Constant Fire, The End of
Speaker 1: the Beginning, and Light of the Stars. Those are all
Speaker 1: nonfiction science books, of course, So to be clear, we're
Speaker 1: talking about two very legitimate scientists and science communicators, not
Speaker 1: you know, not a couple of of quacks who were
Speaker 1: staring into the hollow Earth or anything. So the authors
Speaker 1: here begin with a very reasonable consideration of the search
Speaker 1: for intelligent life elsewhere in the universe. Uh. And then
Speaker 1: this is something we've we've touched on the show plenty
Speaker 1: of times before. Ours is the only model of life,
Speaker 1: but we generally consider technological advancement to be a hallmark
Speaker 1: of intelligent life. And more to the point, something we
Speaker 1: can search for signs of, uh concerning other worlds and
Speaker 1: other star systems. Uh. You know, and anytime you can,
Speaker 1: you can figure out how to look for signs of
Speaker 1: of advanced and expansive energy harvesting or consumption. Uh. That
Speaker 1: might be a way for us to tell if there's
Speaker 1: something else out there that is significantly advanced. Right, and
Speaker 1: it also might be a simple prerequisite for contact, because uh,
Speaker 1: they're talking about so that they started off by looking
Speaker 1: at this as an astrobiology question. You know, you're you're
Speaker 1: looking for signs of life elsewhere in the universe. And
Speaker 1: of course, the the search for intelligent life in the
Speaker 1: universe in practical terms, what's accessible to us really boils
Speaker 1: down to the search for life capable of Harvard harnessing
Speaker 1: radio technology within our galaxy. You know, you could probably
Speaker 1: find maybe chemical biosignatures in in the atmospheres of exoplanets
Speaker 1: that would give you an indication that there's some kind
Speaker 1: of life there, maybe bacterial in nature or whatever. But
Speaker 1: if you're looking for intelligent life, you're you're probably talking
Speaker 1: about radio of some kind, right, And so the kinds
Speaker 1: of civilizations that develop radio communication technology would fall under
Speaker 1: the classification of industrial civilizations. And these are what author
Speaker 1: the authors define as civilizations that have the ability to
Speaker 1: harness energy on a global scale. And they bring up
Speaker 1: how this actually feeds into one of the the recurring
Speaker 1: characters in in the astrobiology literature, the Drake equation. That's right, Yeah,
Speaker 1: they bust out the Drake equation, and of course consider
Speaker 1: how how some of the takeaways relate to Earth, especially
Speaker 1: the notion that over the course of a planet's existence,
Speaker 1: multiple industrial civilizations can theoretically arise over the span of
Speaker 1: time that life exists there. And then we have to
Speaker 1: factor in questions over you know, how many times life
Speaker 1: itself may have evolved or started out on Earth before
Speaker 1: our last universal common ancestors got going. The possibility of
Speaker 1: a shadow biosphere and the idea that species like dolphins
Speaker 1: may suggest independent evolutions of intelligence on Earth. Um, you know,
Speaker 1: so we're left with this idea that, yeah, the radically
Speaker 1: and given the footprint of life on Earth, you could
Speaker 1: have had multiple intelligences uh evolved and arise during that
Speaker 1: time period. Because that's certainly what the Drake equation seems
Speaker 1: to allow for concerning other worlds. Well, yeah, and I
Speaker 1: you know so I kind of love the Drake equation.
Speaker 1: You know, it's a famous tool that I really enjoy
Speaker 1: thinking about because because it does the job of taking
Speaker 1: a question that seems like we could not possibly answer.
Speaker 1: The question is how many active technological civilizations are there
Speaker 1: in the Milky Way galaxy? And you know, if you're
Speaker 1: being honest with yourself, the correct answer to that is
Speaker 1: how the hell should I know? Like, there's no way
Speaker 1: to answer that question at all. But what the Drake
Speaker 1: equation does is break that unanswerable question down into a
Speaker 1: number of other questions that you then multiplied together to
Speaker 1: get an estimated number. And many of those smaller questions
Speaker 1: themselves could perhaps be answered, and in fact, some of
Speaker 1: them 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 gas about.
Speaker 1: And so the classic formulation of the Drake equation is
Speaker 1: to get your number of civilizations 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 civilization. Maybe they only exist
Speaker 1: for a few hundred years. Because one thing we know
Speaker 1: is that our technological civilization is just a tiny blip
Speaker 1: on the history of planet Earth, even a tiny blip
Speaker 1: on the history of life on planet Earth. Earth is
Speaker 1: four point five billion years old. There's been life on
Speaker 1: Earth for most of that time. Uh. The authors here
Speaker 1: estimate that there has been complex life on Earth to
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 it again it gets
Speaker 1: into sort of uh, you know, sci fi friendly concepts.
Speaker 1: It's a useful in considering the evolution of life and
Speaker 1: the existence of intelligent life on other worlds. And it
Speaker 1: also shines a light on what we're doing now and
Speaker 1: where 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 sick clickal process where you get a rise
Speaker 1: in technological civilization, then then it disappears for some reason.
Speaker 1: You 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 a perfectly plausible model to entertain is like
Speaker 1: what usually happens in the universe. Uh. And we just
Speaker 1: don't have the h we don't have the evidence to
Speaker 1: really have an opinion on that. Yeah, I mean a
Speaker 1: lot of it just comes back to the fact that, again,
Speaker 1: we are the only model of intelligent life, and certainly
Speaker 1: technologically advanced intelligent life that we have to look at,
Speaker 1: So we have nothing to compare us to. Yeah, and
Speaker 1: we don't know what's going to happen to us in
Speaker 1: the long run. Right. So uh, Well, let's get into
Speaker 1: the I guess the sort of the first part of
Speaker 1: the paper, and I do want to drive home that
Speaker 1: if you want to just go right to the paper
Speaker 1: yourself and dive in. Um, you just do a search
Speaker 1: for the title and you can find it hosted on NASA.
Speaker 1: They have as has a as a PDF of this
Speaker 1: that's very easily accessible. Uh. You can also read it
Speaker 1: in full on the Cambridge University Press website, which I
Speaker 1: think is the press behind the journal, the International Journal
Speaker 1: Journal of Astrobiology. And yeah, so it's all on their
Speaker 1: end with the references hyper linked and all that, which
Speaker 1: is nice. Yes, yeah, absolutely so if he hit a paywall,
Speaker 1: don't don't give up. It's out there. UM. And I
Speaker 1: believe Adam Frank also wrote a piece for What the
Speaker 1: Atlantic where he nicely summarizes some of the ideas here.
Speaker 1: Oh yeah, and he also tells a funny story about
Speaker 1: how they arrived at writing the paper, because I think
Speaker 1: he says, uh, he showed up in Gevin Schmidt's office
Speaker 1: to to talk about UM, to talk more about astrobiology
Speaker 1: like Drake equation type questions, and he's like, okay, so
Speaker 1: we we we know we've got one industrial civilization on Earth.
Speaker 1: And then Schmidt responded by saying, how do we know
Speaker 1: we're the only one just hitting that early like wall.
Speaker 1: They're like wow, And then that turned into the paper. Yeah,
Speaker 1: and it's it's it's quite a paper. So let's see,
Speaker 1: let's get into the first part of it, which I
Speaker 1: think you can loosely think of it's just sort of
Speaker 1: a look at the limits of our vision. So they
Speaker 1: point out that for the last two point five million years, uh,
Speaker 1: there's widespread physical evidence of things like climate change, soil
Speaker 1: horizons this is where one layer of soil differs from
Speaker 1: belower above, speaking to changes recorded in the soil, as
Speaker 1: well as archaeological evidence of non Homo sapiens cultures such
Speaker 1: as the Neanderthals. And this two point five million year
Speaker 1: period is known as the Quaternary. Now, going back before
Speaker 1: the Quaternary again more than two point five million years ago,
Speaker 1: the land evidence is harder to come by. You have
Speaker 1: to depend on drilling, mining, and occasional exposed sections of
Speaker 1: the earth. Even in the ocean, sentiment evidence apparently only
Speaker 1: goes back to around one seventy million years ago. Yeah,
Speaker 1: and I think for me this was actually one of
Speaker 1: the most interesting parts of the paper because I would say,
Speaker 1: if 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 sci fi imaginings, right, because you
Speaker 1: encounter elder civilizations and in other works like there's usually
Speaker 1: some sort of a ruin or a vault or some
Speaker 1: sort of mysterious monolith or something like the idea that
Speaker 1: 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 uh, 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? Would 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 ma at mon at All in two
Speaker 1: thousand nine that the oldest large patch of land surface
Speaker 1: on Earth is probably in the Negev Desert, and that's
Speaker 1: only about one point eight million years old. One point
Speaker 1: eight million years, I mean, compared to the history of
Speaker 1: civilization is a long time. But that's again, it's like
Speaker 1: nothing in geological time. It's a tiny fraction of of
Speaker 1: earth history. So if we wanted to find remnants of
Speaker 1: a civilization from say, hundreds of millions of years ago,
Speaker 1: you probably would not find that on the surface of
Speaker 1: the Earth. You'd have to look for it in in
Speaker 1: exposed geological strata from from previous eras. And even then
Speaker 1: you can't just count on the fact that you would
Speaker 1: be finding fossils of that civilization all over the place. Yeah, exactly.
Speaker 1: That They that they hit on something we we've discussed
Speaker 1: on 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 might 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 a
Speaker 1: uh doing you know, some sort of an investigation of
Speaker 1: a planet or our planet, those fossilizations would have to
Speaker 1: survive and then they would have to be found. Yeah, exactly.
Speaker 1: And and so again this might be pushing against your intuition.
Speaker 1: You would say, like, wait a minute, there's there's there's
Speaker 1: there's signs of human life all over the surface of Earth.
Speaker 1: And and we have, you know, at least a few
Speaker 1: thousand uh complete dinosaur fossils, enough to have museums of
Speaker 1: natural 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 ours 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,
Speaker 1: sure surely my rice cooker would be found hundreds of
Speaker 1: millions of years in the future. But yeah, 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 of creating a
Speaker 1: fossil record of our current civilization. Only small parts of
Speaker 1: Earth's 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: orders 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 you knew somehow,
Speaker 1: with some certainty that there was that that there was
Speaker 1: a technological civilization during this time in the ancient ancient past. Uh, yeah,
Speaker 1: you would. You would have to you have to really
Speaker 1: know exactly where to drill down to hit them. You
Speaker 1: couldn't just expect to randomly do it unless you did
Speaker 1: a lot of drilling and digging and and excavation. Um.
Speaker 1: But but but so what we've been talking about here
Speaker 1: is challenging the the intuition that you would just be
Speaker 1: finding physical fossil remnants and artifacts of this civilization from
Speaker 1: hundreds of millions of years ago all over the place.
Speaker 1: And I think they do a very good job of
Speaker 1: knocking that down. But of course it is not hopeless
Speaker 1: because they say, while our chance of finding the physical
Speaker 1: remains of a hypothetical Silarian civilization might be very low,
Speaker 1: there would be other traces of the existence of that
Speaker 1: civilization that would be preserved in the geologic record, and
Speaker 1: you you would have a very good chance of finding
Speaker 1: those traces. Yeah, and that's that's what most of the
Speaker 1: rest of the paper deals with. I do want to
Speaker 1: point out one of the things that they bring up
Speaker 1: in passing that I thought was interesting. They point out
Speaker 1: that that you could certainly make an argument for or
Speaker 1: against the evolution of intelligent life in a world based
Speaker 1: on the probable evolution of species that are in the
Speaker 1: fossil record, but that they would be focusing on physiochemical
Speaker 1: tracers for previous industrial civilization. So I hadn't really thought
Speaker 1: about this, but like the idea of like looking at say,
Speaker 1: dinosaur fossils and saying, well, we don't have evidence that
Speaker 1: they evolved in into an intelligent technological species, but if
Speaker 1: we but we can make an argument based on this
Speaker 1: fossil and this fosil fossil that they were headed in
Speaker 1: that direction. I feel like even that's the kind of
Speaker 1: thing that probably wouldn't be quite as clear as your
Speaker 1: intuition might lead you to assign them, because I mean,
Speaker 1: like intelligence in mammals arose very rapidly in geologic time. Yeah,
Speaker 1: So again it reached this situation where the fossil record
Speaker 1: could just be missing that snapshot entirely. So this all
Speaker 1: leads you the next to the next major question. Given
Speaker 1: the limits of what we can dettacked in the geochemical record,
Speaker 1: what exactly could we look for on a planet to
Speaker 1: see if an industrial society ever existed there? And yeah,
Speaker 1: that's what the bulk of the paper focuses on. So
Speaker 1: in the case of Earth, if an organized, intelligent society
Speaker 1: evolved during the pre Quaternary time but they didn't reach
Speaker 1: the level of an industrial society, there simply would be
Speaker 1: no record of 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 harn using energy for industrial use. I
Speaker 1: was reminded of our episodes on fire technology because if
Speaker 1: listeners may remember, we discussed, well, could something that evolved
Speaker 1: in the water or or on a water world, could
Speaker 1: they ever really get any kind of advanced technology going
Speaker 1: if they didn't have access to the surface, and that
Speaker 1: seems to be a factor here as well, as they're
Speaker 1: only looking at the period during which something could have
Speaker 1: evolved on land. Yeah, so you could maybe have advanced
Speaker 1: intelligence in the water. But it's maybe this is just
Speaker 1: a lack of imagination on our part. You know, you
Speaker 1: always need to be aware of the limitations 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 appli A scene. Uh, and that's around
Speaker 1: four million years ago, Yeah, because if it was much
Speaker 1: more recent, you'd 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 haven't nicely divided up. The first
Speaker 1: one is, uh, well, they basically have two broad categories
Speaker 1: and then some some details on that category. The first
Speaker 1: big one though, would be looking at the geological footprint
Speaker 1: of the anthroposcene. So, as we've discussed in the show before,
Speaker 1: there's an argument to be made that the impact of
Speaker 1: human civilization on the environment and the geologic record constitutes
Speaker 1: its own geologic era, the Anthropocene. So not all the
Speaker 1: changes would be recognizable millions of years later, but some
Speaker 1: would be. Right. So, human activity at this point is
Speaker 1: is large scale enough that we are making change is
Speaker 1: to the earth that that are that are widespread or
Speaker 1: you could even say global, And I was gonna say permanent,
Speaker 1: not permanent, but extremely long lived. You know, going way
Speaker 1: into the future, you will be able to find signs
Speaker 1: in the rocks and the ice and the setiment, you know,
Speaker 1: the things on Earth that persists over long periods of
Speaker 1: time that will leave records of what we did to
Speaker 1: the earth in just the past three years or so. Right,
Speaker 1: And uh, And as we've probably mentioned before, the anthropasyn
Speaker 1: is not a an official geological era as much as
Speaker 1: any of these things can be, you know, official if
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 are 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: any of the changes we're talking about of this kind
Speaker 1: would 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 and in a way almost almost encouraging, uh, the
Speaker 1: sustainability paradox. So the idea here is that of course
Speaker 1: the longer human civilization lasts, especially technological civilization, the greater
Speaker 1: the geologic signal of its impact. Again, that that lasting
Speaker 1: those lasting signs in the environment, not the faces they
Speaker 1: carved into the mountains but impacts again on their their
Speaker 1: geochemical and nature. Um, so that signal increases. But the
Speaker 1: longer human civilization lasts, the more sustainable it must become
Speaker 1: in order to revive. And this is of course the
Speaker 1: reality we're living in right now. If a civilization survives
Speaker 1: this test and becomes more sustainable, then that signal grows weaker. Right.
Speaker 1: So it's almost like the strength of the signal left
Speaker 1: for future people to discover is directly proportional to how
Speaker 1: suicidal that civilization is, right Like, the more it is
Speaker 1: just burning through fossil fuel resources and the rate of that,
Speaker 1: the stronger the signal will be. And so a civilization
Speaker 1: at some point, they say, well, will naturally tend to
Speaker 1: attenuate for a couple of reasons. Either it realizes it
Speaker 1: can't keep going at that rate, or it's going to
Speaker 1: cause climate damage to itself, so it will naturally switch
Speaker 1: to more sustainable uh energy sources that are harder to
Speaker 1: detect in the future, or it of course does so
Speaker 1: much damage to itself that it's signal naturally is reduced,
Speaker 1: right right. So, so basically coming back to what you
Speaker 1: said earlier, it's not just that there there's gonna be
Speaker 1: a sign. There's gonna be the signal, uh, this footprint
Speaker 1: of a civilized ation, uh in the in the you know,
Speaker 1: the geochemical record. It's it's also that it may just
Speaker 1: be very short. It may be a little it's not
Speaker 1: going to be this. Uh, it's not gonna be a symphony.
Speaker 1: It's going to maybe be a note or two. So basically,
Speaker 1: the idea being that that that a real strong, much
Speaker 1: stronger argument for aliens existing and having some sort of
Speaker 1: role or some sort of advanced technology having some sort
Speaker 1: of role on Earth in the in the ancient history
Speaker 1: would not be look at the pyramids, I think aliens
Speaker 1: did this, or I think, you know, ancient scientists did this.
Speaker 1: It would be pointing at say a blip in uh,
Speaker 1: you know, or an increase in global temperatures during a
Speaker 1: certain period of time and saying, I think the aliens
Speaker 1: did this, or I think the advanced technology in question
Speaker 1: did this. I mean, even then, I think that would
Speaker 1: be a very speculative and and difficult to prove hypothesis.
Speaker 1: It would be kind of just like unfalsifiable speculation, but
Speaker 1: that that would perhaps be the more likely type of
Speaker 1: signal you would find if there had been alien intervention,
Speaker 1: then you know specific artifacts than all right, well, let's
Speaker 1: get into some of the specifics of the footprint that
Speaker 1: the authors lay out here. The first one is a
Speaker 1: stable isotope anomalies of carbon, oxygen, hydrogen, and nitrogen. And
Speaker 1: this is one of the big ones, an estimated point
Speaker 1: five trillion tons of fossil carbon via the burning of
Speaker 1: fossil fuels and warming of the planet. Um they quote,
Speaker 1: we we expect this temperature rise to be detectable and
Speaker 1: surface ocean uh carbonates, notably for Manifera. This is a
Speaker 1: single celled organism with with with a chalky shell. UM.
Speaker 1: Organic biomarkers cave records, such such as stalactites, lake ostracods.
Speaker 1: These are minute aquatic crustaceans and high latitude ice cores,
Speaker 1: though only the first two of these will be a
Speaker 1: retrievable in the time scales considered here. Right, So this
Speaker 1: thing about the the isotope anomalies of of carbon and
Speaker 1: these other elements is very interesting. So they say, you know,
Speaker 1: there are natural distributions that you would find records of
Speaker 1: in the different isotopes of carbon that are that are
Speaker 1: moving around in Earth's atmosphere. But when people suddenly start
Speaker 1: pulling huge amounts of fossil carbon, carbon of a biological
Speaker 1: origin out of the ground and burning it, you suddenly
Speaker 1: start throwing those isotopes out of whack, and that will
Speaker 1: be something that will leave records for millions of years
Speaker 1: to come. So you you can look in the geological records,
Speaker 1: you know, the record of of strata from previous eras,
Speaker 1: and say, huh, for some reason, in this one period
Speaker 1: deep in history, suddenly the carbon isotopes got way out
Speaker 1: of whack, as if suddenly a bunch of fossil carbon
Speaker 1: like coal or oil or whatever had been burned at
Speaker 1: a at a hideous rate into the atmosphere. Right. And
Speaker 1: so you know, looking at our our time now of
Speaker 1: of of modern human civilization, you know this that we
Speaker 1: have this fossil fuel consumption, and we have the invention
Speaker 1: of the haber Bosch process and the large scale use
Speaker 1: of of nitrogenous fertilizers and agriculture, which will also heavily
Speaker 1: 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 related 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 Here'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 extinct actions already, and we're
Speaker 1: living in the midst of an extinction event. Uh. This
Speaker 1: will 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: vulcanism as as the cause of this one, or say
Speaker 1: a large space impact like the Kti extinction event. But
Speaker 1: there are other extinction events in Earth's history where the
Speaker 1: cause 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 prove 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 sort of chemical contingencies. A technological civilization
Speaker 1: does not have to use plastics. Plastics are just something
Speaker 1: that humans happen to use. There are other things that
Speaker 1: seem probably more universal, like almost any industrial civilization you
Speaker 1: 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 M 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 bernova or something like that. This isotope
Speaker 1: of plutonium. Yes, this particular 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 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 though of course nothing really comes close to evidence
Speaker 1: 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 and again they're not arguing that these are evidence
Speaker 1: of past pre human industrial civilizations on Earth, but merely
Speaker 1: point to them as the sources of events we might
Speaker 1: look at. Yeah, and I would say the biggest one
Speaker 1: that they focus on in the paper is the event
Speaker 1: known as the Paleocene Eocene Thermal Maximum or p E
Speaker 1: t M. Yeah. This is an abrupt spike in carbon
Speaker 1: and oxygen isotopes near the Paleocene Eocene transition uh fifty
Speaker 1: six million years ago, resulting in a five to eight
Speaker 1: degree celsius global average temperature rise. This is widely thought
Speaker 1: to be due to well, I think they're there are
Speaker 1: different theories of One is that it's volcanic activity, um.
Speaker 1: But there have also been hypotheses put forth that it
Speaker 1: could have been a common impact. It could be due
Speaker 1: to burning pete methane being released, and a few other candidates. Um.
Speaker 1: It's also used as a means of of understanding and
Speaker 1: kind of like kind of modeling out the effects of
Speaker 1: climate change during our own era. Yeah. And and one
Speaker 1: of the reasons this one gets singled out is, uh
Speaker 1: so it really looks like, Okay, here we're seeing, for example,
Speaker 1: these carbon isotope signature changes that would signal that huge
Speaker 1: amounts of biogenic carbon carbon that originally came from life forms,
Speaker 1: like the stuff you would find in fossil fuels, is
Speaker 1: being burned and released into the atmosphere. Now, how would
Speaker 1: that happen if if if it wasn't creatures from the
Speaker 1: Black Lagoon with leather face masks digging up a bunch
Speaker 1: of fossil fuels and burning them for their civilization. Well, no,
Speaker 1: you probably don't need to jump to that conclusion, because
Speaker 1: there are other solutions on offer, like, for example, there
Speaker 1: might have somehow been lots of access of volcanic magma
Speaker 1: two beds of fossil fuels. Maybe certain types of volcanic
Speaker 1: activity tended to set a light to a lot of
Speaker 1: natural reserves of fossil fuels and shale beds and things
Speaker 1: like that. And this almost acted as if the Earth itself,
Speaker 1: we're we're setting off an industrial revolution, but it was
Speaker 1: just volcano interacting with with these reservoirs of carbon in
Speaker 1: the ground. Yeah, all you need is geologic upheaval and
Speaker 1: volcanic activity. And again um our our planet has a
Speaker 1: as a as a very active geological life, so there's
Speaker 1: plenty of opportunity for this sort of thing to potentially
Speaker 1: have taken place. So it kind of comes back to
Speaker 1: a problem with the signal here, the signal you would
Speaker 1: be looking for in the geochemical record, in many cases,
Speaker 1: the very sort of signal we're looking for especially concerning
Speaker 1: carbon and warming, could have also been caused by these
Speaker 1: naturally occurring causes, and so strong signals might be coming
Speaker 1: from something else, and more specific signals that we might
Speaker 1: look to just might be too weak to to ever
Speaker 1: possibly observe or to really make much out of. Oh yeah,
Speaker 1: this is an interesting paradox they talk about in their
Speaker 1: conclusion of all of the criteria they're able to come
Speaker 1: up with in this framework for for looking for past
Speaker 1: industrial civilizations, the stuff that you would expect any industrial
Speaker 1: civilization to do also has other explanations, and so so
Speaker 1: it's not conclusive that it was an industrial civilization that
Speaker 1: this would be things like, you know, the carbon stuff. Meanwhile,
Speaker 1: the stuff that would be really strong evidence of of
Speaker 1: an intelligent civilization origin, that stuff that civilizations might not do.
Speaker 1: It's more contingent things like plastics and stuff. You know,
Speaker 1: you could have a civilization without plastics. That's not a
Speaker 1: necessary milestone in the in the progress of energy harnessing,
Speaker 1: and maybe it's even the sort of thing, uh, an
Speaker 1: advance civilization would move away from. Coming back to that
Speaker 1: the sustainability paradox, when one could hope, I imagine now
Speaker 1: the authors again they're very clear about just how far
Speaker 1: you should take this hypothesis, stating that quote the Silarian
Speaker 1: hypothesis cannot be regarded as likely merely because no other
Speaker 1: valid idea presents itself. Uh So they admit that this
Speaker 1: this sort of thing could easily get out of hand
Speaker 1: with folks pointing to any sort of signal in the
Speaker 1: geochemical record as being possible proof of human technological societies.
Speaker 1: If you're doing that, you're you're really taking it and
Speaker 1: running with 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 aliens 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 uh left by our own um Anthropocene era, as
Speaker 1: well as a deeper exploration of the elemental and um
Speaker 1: compositional anomalies that we find in extant sediments. Basically, we
Speaker 1: look 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, uh,
Speaker 1: it gives us a little more of a sort of
Speaker 1: a robust spectrum. And how to interpret these things and
Speaker 1: and then moving forward to you know, potentially considering other worlds,
Speaker 1: looking at other planets like even Mars. Uh. It gives
Speaker 1: us one more tool, one more UH way to look
Speaker 1: at the evidence. Yeah, exactly. They're not arguing this because
Speaker 1: they think there was a civilization. It's that we should
Speaker 1: consider these possibilities when looking at planets, even including our own,
Speaker 1: and know what we would look for if we wanted
Speaker 1: to consider that possibility, right, Because ultimately this is not
Speaker 1: a supernatural explanation. This is ultimately, you know, a natural hypothesis.
Speaker 1: But but it is admittedly an outside possibility. Now, of
Speaker 1: course we're here talking about reasons why you shouldn't just
Speaker 1: jump to the conclusion of a Salurian civilization. But but
Speaker 1: there are also some arguments against it in some of
Speaker 1: the specific events that they look at. For example, if
Speaker 1: you know, maybe the best possibility is this interesting event
Speaker 1: in Earth history, the Paleocene Eocene thermal maximum. More suddenly
Speaker 1: there was there was rapid global warming and UH and
Speaker 1: these in these chemical changes like with carbon isotopes. They
Speaker 1: even put some arguments back against considering UH civilization as
Speaker 1: a cause of this global warming in Earth's history. Because
Speaker 1: they say, look, the kind of global warming caused by
Speaker 1: our civilization is happening in an incredibly rapid fashion over
Speaker 1: just a few hundred years. This actually, though it's it's
Speaker 1: relatively rapid in geologic terms. The the p et M
Speaker 1: actually happened probably over hundreds of thousands of years, which
Speaker 1: which is incredibly slow if you're imagining that civilization was
Speaker 1: the cause of it, right, if you're if you're comparing
Speaker 1: it to the model of of human industrial advancement, it's
Speaker 1: incredibly slow. So there's not only the point that you
Speaker 1: shouldn't just jump to the conclusion of there was a
Speaker 1: law civilization because it feels cool, but like in the
Speaker 1: specific instances they look at, there are some reasons for
Speaker 1: thinking that's probably not true. I don't know, I guess
Speaker 1: unless those civilizations were like just really lazy. I mean,
Speaker 1: you can sort of, you know, pull out your sci
Speaker 1: fi hat and and put it on and come up
Speaker 1: with various ideas of, you know, for why they might
Speaker 1: have been this way. Maybe they were super long lived. Yeah,
Speaker 1: they weren't very ambitious, and they're like this, note, this
Speaker 1: is the right level of industrialization, and we want to, uh,
Speaker 1: we need to keep going at this rate. I don't know,
Speaker 1: they didn't reproduce all that much. I don't know. I
Speaker 1: mean that that's ultimately one of the problems with with imagining, uh,
Speaker 1: you know, other life forms. It's like it's just you know,
Speaker 1: it's you can you can make a case for any
Speaker 1: number of things, um and and try and make it
Speaker 1: fit your your hypothesis. And of course that's not really
Speaker 1: the way to go about it, I mean, not in
Speaker 1: from a scientific perspective, from a sci fi dreaming creative perspective, yeah,
Speaker 1: go for it. Um So, 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 corrupt 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 alpoly engage in a number of
Speaker 1: these ideas as as more as art than science, and
Speaker 1: there there's 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: The in in this particular book, you know, the the
Speaker 1: examine this idea. They said, okay, here's the speculative idea,
Speaker 1: and we don't have evidence that had ever happened, But
Speaker 1: if it were to have happened, what sorts of specific
Speaker 1: evidence might we look for? And in this case, we're
Speaker 1: talking about signs that are evident in ancient religions and
Speaker 1: uh and so forth. Uh. And I thought that was
Speaker 1: a great treatment of that question. Uh and against Sagan's
Speaker 1: treatment reminds me of the treatment given in this paper
Speaker 1: by these authors. But of course Segand had to come
Speaker 1: back and continue to argue with the ancient alien people
Speaker 1: who were you know, very much going off in their
Speaker 1: own directions, yeah, and pushing pushing art as science, and
Speaker 1: Sagan having to remind them like, no, I love art
Speaker 1: as much as the next guy. But here's how we
Speaker 1: approach this from a scientific perspective. Well, I mean, I
Speaker 1: think the important thing about this stuff, like Sagan's work
Speaker 1: on that or or or the paper we're looking at here,
Speaker 1: is it's good too when you're when you're exploring it
Speaker 1: like a tantalizing and juicy idea. It's a good idea
Speaker 1: to have criteria for what would be good evidence of
Speaker 1: such a thing before you're actually looking at individual evidence
Speaker 1: in cases, because if you look at the evidence first
Speaker 1: and then you try to come up with criteria. You're
Speaker 1: gonna have a tendency to want to fit your criteria
Speaker 1: to whatever evidence you've already got. The cherry picking model
Speaker 1: or what is it the other name of the barn
Speaker 1: wall fallacy or something like that. Remember, the idea is like,
Speaker 1: you know, somebody says, you know, I'm a great shot,
Speaker 1: and so they shoot at the side of a barn
Speaker 1: and then they go up, they walk up to their
Speaker 1: bullet hole, and then they draw a bull's eye perfectly
Speaker 1: around it. That's that's a great point. That's that's a
Speaker 1: great way of looking at it. All Right, Well, I
Speaker 1: guess we're good and go ahead and wrap this episode up.
Speaker 1: But we'd love to hear from everyone out there. I
Speaker 1: love to hear from any doctor who fans who have
Speaker 1: some additional information they want to share about the Silurians
Speaker 1: and various related um species that have popped up in
Speaker 1: that show. And perhaps you have specific thoughts about about
Speaker 1: you know, just this this basic you know view uh
Speaker 1: and what it reveals about humanities uh place on Earth
Speaker 1: right now, and what technological civilization is doing to the planet,
Speaker 1: and just you know, ultimately what kind of a you know,
Speaker 1: a small blip 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: and chemical alteration of the atmosphere and all you know,
Speaker 1: stuff like that, uh, and 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 U, 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 enemies will be will
Speaker 1: be organics, and I don't know, Yeah, I wonder at
Speaker 1: 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. Al 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 read your various listener mails, always a good time.
Speaker 1: On Wednesday's we do a short form artifact or monster fact,
Speaker 1: and then on Friday's we do Weird How Cinema. That's
Speaker 1: our time to set aside most serious issues and just
Speaker 1: talk about a weird film. Huge thanks as always to
Speaker 1: our excellent audio producer Seth Nicholas Johnson. If you would
Speaker 1: like to get in touch with us with feedback on
Speaker 1: this episode or any other, to suggest a topic for
Speaker 1: the future, or just to say hello, you can email
Speaker 1: us at contact at stuff to Blow your Mind dot com.
Speaker 1: Stuff to Blow Your Mind is production of I Heart Radio.
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Speaker 1: Props had a chat ba