I think there could be a 5% chance that the paleocene-eocene thermal maximum 55 million years ago was the result of a prior global industrial civilization. Conditional on that being the case, high probability they were birds and a decent possibility they lived on Antarctica.
We are an existence proof for smart industrial animals being a thing that can happen on Earth. We are not an existence proof of smart industrial animals lasting for geologically long periods of time. There is not necessarily reason to think that just because you are successful in an epoch that you burn the black rocks that you will continue to be so.
As you go back in time the fossil record degrades drastically and many species at this time are known from single digit numbers of specimens. The PETM resembles what we are doing to the earth system entirely too closely, from a large release of biogenic carbon within a few thousand years to the spike in mercury levels to ocean anoxia. At the time primates did not exist in significant diversity and any that did exist were tiny, but birds, whose brains differ from the default tetrapod brains in ways quite similar to the way that of primates do and allows very easy increase in neuron number, did exist in profound diversity.
We are tropical animals and spread across the entire world because we came from the hottest place on Earth and you can keep us warm just by wrapping us in clothes in a low-tech way. If somebody evolved on the coldest parts of Earth, you need high technology (refrigeration) to survive anywhere else and they could be limited to polar latitudes, including the only continent we have almost no geological record of and has been poorly explored—Antarctica. Antarctica and nearby continents also bore multiple great-ape-sized flightless bird lineages at this time, and was temperate while Canada was full of Amazon-style rainforest and the equator bore stifling hot supertropics.
Corollary: Industrial civilization is an unstable self-limiting phenomenon and will be gone in centuries to millennia.
I love the idea, but I’m sceptical based on genetics. Our civilisation has moved a lot of species around, from stuff like bringing placental mammals to Australia to things like exporting food crops around the world. Potatoes evolved in the Americas, now you can find them everywhere. Soy beans came from Japan / East Asia but now they’re heavily cultivated in Brazil.
I assume that any previous industrial civilisation, even if it were less adaptable than humans, would probably have spread outside of its home continent, if only to look for oil and minerals. And they’d end up introducing species all over the place, like we have, and modern day geneticists should be scratching their heads and trying to figure out all sorts of mysteries about what evolved where. But so far as I know (I’m not an evolutionary biologist) we just don‘t have those sort of mysteries where species categories suddenly jump continents.
So, sadly, I don’t think that the Earth has had a previous industrial civilisation at least since Australia separated from the other continents. I wouldn’t rule out previous pre-industrial civilisations, though. In fact, given the wide variety of species today which demonstrate at least some tool use—not just great apes but also capuchin monkeys, corvids, even octopuses—I’d be surprised if no previous species ever got to at least homo erectus level.
Would there be wild descendants of the soybean all over the world if we disappeared, can the domesticates go wild without us?
The PETM was associated with a mixup of plant and animal ranges, but it is generally explained as being the result of the 5+ degree C temperature spike shifting all their ranges poleward and this then allowing them to wind up at different longitudes when they shifted back towards the equator, plus the general chaos of a minor extinction churning the ecosystems.
If we go with the least likely part of the scenario mentioned above (antarctic habitat), Antarctica and South America and Australia all were faunally related after the breakup of Gondwana...
Maybe the crop plants weren’t the best example to use. If we all disappeared tomorrow, there would still be rats and dingos and feral hogs in Australia. There would be rats on almost every island worldwide. There would be Japanese knotweed and buddleja and rhododendrons everywhere. There would be bougainvillea across all the tropics. There would be American crayfish and Pacific oysters in Britain. There would be Asian carp in North America. There might be hippopotamuses in South America! Ie it’s not just domesticates, it’s the far larger number of wild species we’ve moved around (probably thousands or more—I couldn’t find an estimate with a quick google search)
If any comparable thing had happened in the past, palaeobiology and genetic taxonomy should be a godawful mess instead of dovetailing nicely with the geological evidence on continental drift. Now maybe I’m just ignorant, and evolutionary biologists are going round scratching their heads and wondering how ancestral koalas suddenly showed up on Madagascar 55 million years ago, or some equivalent mystery. But I’m not aware of any such problem. Maybe the Antarctic habitat explains that, but I have trouble squaring the idea of a civilisation large-scale enough to cause runaway global warming with one that leaves no trace 55 million years later.
The world would be a more interesting place if there was a previous industrial civilisation. I just don’t think there is evidence to support that proposition, and even 55 million years later, there should be some traces. But if someone digs up fossil plastics in Antarctica or something, I will be delighted to be proven wrong.
Ok, that does sound wierd. Do I understand correctly, that you postulate a PETM civilization that had developed sufficient technology to extract fossil fuels (as source of negative D13 carbon) to explain the observed carbon and climate? What population and per capita energy extraction rates did you factor? And if they let no trace, presumably they somehow found all this FF very close to Antarctica? If so, I think I would struggle to assign even 0.1% weight to this hypothesis compared to competing hypotheses. It has the feel of an invisible dragon in the garage to me.
I propose very few details and a low probability (and as I add more details from ‘someone burned a lot of carbon’ I give even less), and the scenario outlines above total carbon release could be split between an artificial release and later positive feedbacks (seafloor clatherate and the like). As for no trace, finding bedding planes within the PETM itself is a celebrated event in many places and trying to hit a bedding plane within a short period is hard, and I would need to look into the work of a scientist I really like about erosion rates across continental crust to see what the odds of a carbon deposit near the surface now being near the surface millions of years ago would be...
Well Australia is right beside Antarctica at that time. Its coal deposits are Permian/Jurassic and the continent has hardly changed geologically. Would seem like an obvious place to mine. A civilization mining and burning coal on large enough scale to impact climate is also going to have to manage quick a bit of other tech (esp metallurgy) as well, with the evidence also conveniently hidden. So from Baysian perspective we have quite a number of competing hypotheses for PETM founded on evidence but hard to constrain as to relative effect. The “ancient civilization” hypothesis has no evidence supporting it that I can see. I would of course shift my beliefs rapidly if evidence of past civilization appeared. Calculating sedimentary flux (proxy for erosion rate) through time is routine input into basin modelling. I would guess data exists for practically all sedimentary basins with any potential for hydrocarbons. (And paleogene flux from Australia is really low). Can you be more specific about what carbon deposit you are talking about. (Erosion rates are also estimated from fission-track dating and similar techniques but this is really only relevent to high erosion rate features ie mountain chains). I should say that I am deep in accumulating this kind of data for whole of NZ as it is input into models for surface heat flow that I am helping out with.
Thinking about this some more, if there was an industrial civilisation at the PETM I think it would be most likely marine based. (Maybe cephalopods?)
I previously asked myself what evidence we would see if there was a prior industrial civilisation on Earth and I came up with 1) transfer of biological species to other continents as per my previous comments 2) depletion of fossil fuels (I don’t remotely know enough geology to begin to answer the question of whether we are ‘missing’ fossil fuels that ought to be there) and 3) technofossils especially plastics. I only commented about 1) because that’s the one I thought the most compelling argument.
But actually, a marine civilisation accounts for all three arguments. The oceans were and are connected, so it’s not a surprise to find the same species in both the Pacific and the Atlantic. And the oceans are severely under-studied so we’d be much less likely to notice any oddities. We’re also much less likely to notice missing fossil fuels under water (yes our civilisation drills in the sea if it’s shallow enough but it’s less explored and less understood than the land). And the odds of us finding fossils under the seabed are practically zero. (Unless there’s a good area where what was seafloor at the PETM is now uplifted into a landmass?)
We still have a complete absence of evidence that any such civilisation existed, but I might join you in giving it a 5% possibility.
And now my mind goes down more speculative routes—what does the tech tree of a marine civilisation look like? They couldn’t have fire, therefore no metalworking or pottery. Is there some other basic technology, as hard-to-imagine for us terrestrials as fire would be to a stone-age squid? (Maybe: can you exploit large changes in water pressure to change the properties of wood or other materials? Could a marine civ drop or lower objects a couple of kilometres down, leave them for a while, and then retrieve them, and would that produce useful changes?) How would a civilisation without fire invent combustion engines or steam turbines or other ways to get energy out of fossil fuels? Hmm. I will stop now before I spend all day going down this rabbit hole.
The sad thing is that if we mess it up, there is not enough time before the sun renders multicellular life untenable on earth to restore fossil fuels. So for earth we are the last roll of the dice.
Someone has actually written up a scientific paper discussing the hypothesis that the PETM or other events in the geologic record was caused by a prior industrial civilisation. (If you’re one of the authors, I apologise for telling you something you already know, but if you’re not, I thought you might be interested.) The short version is that there’s no smoking gun, but they can’t rule it out either.
One item the authors don’t go into, which I think is relevant, is the question of whether there are missing fossil fuels. Google tells me that pretty much all existing fossil fuels were formed at least 65 million years ago, which I think makes it unlikely that the PETM 55mya was a previous industrial civilisation, because they’d have burned those fuels instead of leaving them for us to find. But I have zero geological expertise, so someone who knows better than me might be able to pick holes in that argument.
I think there could be a 5% chance that the paleocene-eocene thermal maximum 55 million years ago was the result of a prior global industrial civilization. Conditional on that being the case, high probability they were birds and a decent possibility they lived on Antarctica.
We are an existence proof for smart industrial animals being a thing that can happen on Earth. We are not an existence proof of smart industrial animals lasting for geologically long periods of time. There is not necessarily reason to think that just because you are successful in an epoch that you burn the black rocks that you will continue to be so.
As you go back in time the fossil record degrades drastically and many species at this time are known from single digit numbers of specimens. The PETM resembles what we are doing to the earth system entirely too closely, from a large release of biogenic carbon within a few thousand years to the spike in mercury levels to ocean anoxia. At the time primates did not exist in significant diversity and any that did exist were tiny, but birds, whose brains differ from the default tetrapod brains in ways quite similar to the way that of primates do and allows very easy increase in neuron number, did exist in profound diversity.
We are tropical animals and spread across the entire world because we came from the hottest place on Earth and you can keep us warm just by wrapping us in clothes in a low-tech way. If somebody evolved on the coldest parts of Earth, you need high technology (refrigeration) to survive anywhere else and they could be limited to polar latitudes, including the only continent we have almost no geological record of and has been poorly explored—Antarctica. Antarctica and nearby continents also bore multiple great-ape-sized flightless bird lineages at this time, and was temperate while Canada was full of Amazon-style rainforest and the equator bore stifling hot supertropics.
Corollary: Industrial civilization is an unstable self-limiting phenomenon and will be gone in centuries to millennia.
I love the idea, but I’m sceptical based on genetics. Our civilisation has moved a lot of species around, from stuff like bringing placental mammals to Australia to things like exporting food crops around the world. Potatoes evolved in the Americas, now you can find them everywhere. Soy beans came from Japan / East Asia but now they’re heavily cultivated in Brazil.
I assume that any previous industrial civilisation, even if it were less adaptable than humans, would probably have spread outside of its home continent, if only to look for oil and minerals. And they’d end up introducing species all over the place, like we have, and modern day geneticists should be scratching their heads and trying to figure out all sorts of mysteries about what evolved where. But so far as I know (I’m not an evolutionary biologist) we just don‘t have those sort of mysteries where species categories suddenly jump continents.
So, sadly, I don’t think that the Earth has had a previous industrial civilisation at least since Australia separated from the other continents. I wouldn’t rule out previous pre-industrial civilisations, though. In fact, given the wide variety of species today which demonstrate at least some tool use—not just great apes but also capuchin monkeys, corvids, even octopuses—I’d be surprised if no previous species ever got to at least homo erectus level.
My brain goes interesting places from here.
Would there be wild descendants of the soybean all over the world if we disappeared, can the domesticates go wild without us?
The PETM was associated with a mixup of plant and animal ranges, but it is generally explained as being the result of the 5+ degree C temperature spike shifting all their ranges poleward and this then allowing them to wind up at different longitudes when they shifted back towards the equator, plus the general chaos of a minor extinction churning the ecosystems.
If we go with the least likely part of the scenario mentioned above (antarctic habitat), Antarctica and South America and Australia all were faunally related after the breakup of Gondwana...
Maybe the crop plants weren’t the best example to use. If we all disappeared tomorrow, there would still be rats and dingos and feral hogs in Australia. There would be rats on almost every island worldwide. There would be Japanese knotweed and buddleja and rhododendrons everywhere. There would be bougainvillea across all the tropics. There would be American crayfish and Pacific oysters in Britain. There would be Asian carp in North America. There might be hippopotamuses in South America! Ie it’s not just domesticates, it’s the far larger number of wild species we’ve moved around (probably thousands or more—I couldn’t find an estimate with a quick google search)
If any comparable thing had happened in the past, palaeobiology and genetic taxonomy should be a godawful mess instead of dovetailing nicely with the geological evidence on continental drift. Now maybe I’m just ignorant, and evolutionary biologists are going round scratching their heads and wondering how ancestral koalas suddenly showed up on Madagascar 55 million years ago, or some equivalent mystery. But I’m not aware of any such problem. Maybe the Antarctic habitat explains that, but I have trouble squaring the idea of a civilisation large-scale enough to cause runaway global warming with one that leaves no trace 55 million years later.
The world would be a more interesting place if there was a previous industrial civilisation. I just don’t think there is evidence to support that proposition, and even 55 million years later, there should be some traces. But if someone digs up fossil plastics in Antarctica or something, I will be delighted to be proven wrong.
Ok, that does sound wierd. Do I understand correctly, that you postulate a PETM civilization that had developed sufficient technology to extract fossil fuels (as source of negative D13 carbon) to explain the observed carbon and climate? What population and per capita energy extraction rates did you factor? And if they let no trace, presumably they somehow found all this FF very close to Antarctica? If so, I think I would struggle to assign even 0.1% weight to this hypothesis compared to competing hypotheses. It has the feel of an invisible dragon in the garage to me.
I propose very few details and a low probability (and as I add more details from ‘someone burned a lot of carbon’ I give even less), and the scenario outlines above total carbon release could be split between an artificial release and later positive feedbacks (seafloor clatherate and the like). As for no trace, finding bedding planes within the PETM itself is a celebrated event in many places and trying to hit a bedding plane within a short period is hard, and I would need to look into the work of a scientist I really like about erosion rates across continental crust to see what the odds of a carbon deposit near the surface now being near the surface millions of years ago would be...
Well Australia is right beside Antarctica at that time. Its coal deposits are Permian/Jurassic and the continent has hardly changed geologically. Would seem like an obvious place to mine. A civilization mining and burning coal on large enough scale to impact climate is also going to have to manage quick a bit of other tech (esp metallurgy) as well, with the evidence also conveniently hidden. So from Baysian perspective we have quite a number of competing hypotheses for PETM founded on evidence but hard to constrain as to relative effect. The “ancient civilization” hypothesis has no evidence supporting it that I can see. I would of course shift my beliefs rapidly if evidence of past civilization appeared. Calculating sedimentary flux (proxy for erosion rate) through time is routine input into basin modelling. I would guess data exists for practically all sedimentary basins with any potential for hydrocarbons. (And paleogene flux from Australia is really low). Can you be more specific about what carbon deposit you are talking about. (Erosion rates are also estimated from fission-track dating and similar techniques but this is really only relevent to high erosion rate features ie mountain chains). I should say that I am deep in accumulating this kind of data for whole of NZ as it is input into models for surface heat flow that I am helping out with.
Should add that constraints on d13C of source for PETM are getting better. eg https://www.pnas.org/content/117/39/24088 - favouring volcanic (-6) rather than coal (-25) or gas (-60).
Thinking about this some more, if there was an industrial civilisation at the PETM I think it would be most likely marine based. (Maybe cephalopods?)
I previously asked myself what evidence we would see if there was a prior industrial civilisation on Earth and I came up with 1) transfer of biological species to other continents as per my previous comments 2) depletion of fossil fuels (I don’t remotely know enough geology to begin to answer the question of whether we are ‘missing’ fossil fuels that ought to be there) and 3) technofossils especially plastics. I only commented about 1) because that’s the one I thought the most compelling argument.
But actually, a marine civilisation accounts for all three arguments. The oceans were and are connected, so it’s not a surprise to find the same species in both the Pacific and the Atlantic. And the oceans are severely under-studied so we’d be much less likely to notice any oddities. We’re also much less likely to notice missing fossil fuels under water (yes our civilisation drills in the sea if it’s shallow enough but it’s less explored and less understood than the land). And the odds of us finding fossils under the seabed are practically zero. (Unless there’s a good area where what was seafloor at the PETM is now uplifted into a landmass?)
We still have a complete absence of evidence that any such civilisation existed, but I might join you in giving it a 5% possibility.
And now my mind goes down more speculative routes—what does the tech tree of a marine civilisation look like? They couldn’t have fire, therefore no metalworking or pottery. Is there some other basic technology, as hard-to-imagine for us terrestrials as fire would be to a stone-age squid? (Maybe: can you exploit large changes in water pressure to change the properties of wood or other materials? Could a marine civ drop or lower objects a couple of kilometres down, leave them for a while, and then retrieve them, and would that produce useful changes?) How would a civilisation without fire invent combustion engines or steam turbines or other ways to get energy out of fossil fuels? Hmm. I will stop now before I spend all day going down this rabbit hole.
Good post.
I have wondered about this myself actually.
The sad thing is that if we mess it up, there is not enough time before the sun renders multicellular life untenable on earth to restore fossil fuels. So for earth we are the last roll of the dice.
Amazing. This is the best thing I’ve read all week. How do I subscribe to your newsletter? When is the novelization coming out?
I should start up that astrobiology and evolutionary biology blog again shouldn’t I...
That is weird.
Someone has actually written up a scientific paper discussing the hypothesis that the PETM or other events in the geologic record was caused by a prior industrial civilisation. (If you’re one of the authors, I apologise for telling you something you already know, but if you’re not, I thought you might be interested.) The short version is that there’s no smoking gun, but they can’t rule it out either.
One item the authors don’t go into, which I think is relevant, is the question of whether there are missing fossil fuels. Google tells me that pretty much all existing fossil fuels were formed at least 65 million years ago, which I think makes it unlikely that the PETM 55mya was a previous industrial civilisation, because they’d have burned those fuels instead of leaving them for us to find. But I have zero geological expertise, so someone who knows better than me might be able to pick holes in that argument.