> Changing your environment at planetary scale and breakneck speed is not necessarily the pinnacle of intelligence, certainly not if you have manifestly not yet understood all its intricacies, interdependence etc. A lack of understanding coupled with aggressive random interventions may even affect the very survival of a species.

Well apparently their strategy to ensure survival didn't do too well since we're discussing an extinct civilization here.

Of course, we do have tree hugging octopus today: Save the Pacific Northwest Tree Octopus! https://zapatopi.net/treeoctopus/ (j/k)

A theory about a previous advanced civilization must first and foremost explain how and why it skipped using all the obvious under-your-feet materials and fuel sources in its initial phase.

And taking it even further, maybe they still exist, but have advanced so far they are undetectable to our simple minds and senses, similar to how an ant or bacteria has no idea about our existence. Maybe there are millions of advanced species that we can't detect, considering that there are millions of species we are aware of, and statistically it's unlikely that we would be the most advanced.

That's actually a factor that diseases aim for. Mortal diseases don't spread as much as the ones that don't damage the host as much. Because of this, severe diseases sometimes evolve into mild ones.

Another one is the Azolla event hypothesis where a variety of fern grew so much that as it died and sank to the ocean it sequestered massive amounts of carbon, enough to alter the climate.

Some ideas for sending messages to the next civilization.

1. Genetically modify as many wild plants and animals as we can to have a message encoded in their DNA, and release them back into the wild.

2. In areas that we expect to be geologically not much changed over the next 50 million years arrange concentrations of long lived radioactive materials in patterns that are obviously not natural. Encode a message in those patterns.

3. We could probably do something on the moon with nuclear weapons that could make a long fairly straight trench or series of parallel trenches that would be visible in telescopes and either be obviously non-natural or at least interesting enough to get them to go take a look.

Leave millions of metal spheres, cubes, tetrahedrons, octahedrons, dodecahedrons, and icosahedrons there which contain messages inside.

Google is telling me that any given spot on the moon gets hit be a meteoroid of ping pong ball size or greater about every 1000 years, so many of the messages will likely be destroyed over 50 million years, but maybe enough will make it.

BTW, is meteoroid the correct term? That's what Google's summary used and according to the dictionary definition as a small body that would become a meteor if it entered the Earth's atmosphere it would be correct but when we are talking about impacts on other planets or moons I'm not sure we should restrict meteor and meteorite to just meteoroids that are in or have hit after passing through Earth's atmosphere, respectively.

> a rapid increasing in global temperature (and CO2 concentrations) around between 60-50 million years ago

> a civilization like this would not leave a trace on the geological record

Am curious: if dinosaurs can be found with intact skin [1], after 110 million years, why not remains of the civilization's "people" (bones etc.) after 60-50 million years?

1. https://en.wikipedia.org/wiki/Borealopelta

If PETM was due to large scale use of hydrocarbons, there should be evidence of depletion in the strata, right? For example, currently not all sources are uniformly exploited -- some coal seams and oilfields are all but depleted, others are currently being extracted, and others are yet to be found/exploited.

We should have seen signs of similar non-uniform usage in the strata from before that time period. I wonder if any research has been done on this.

Has someone done the math on what Hydrocarbons (coil, oil) would have been available 60 million years ago?

Would they have been using the same deposits we are suing, or would new deposits have formed over the last 60 million years?

Or could they have depleted their own, but what was un-usable 60 million years ago, have become usable today. Like something that was marsh land 60 million years ago, be coal today?

I think the only option is to leave several copies of the message on the moon, and hope they stumble upon a copy.

> current climate crisis caused by the rapid use of hydro-carbons.

The problem I see is they either had to use sustainable hydrocarbons (so, carbon-neutral) or they would have used up the fossil fuels we're currently using.

Send it to space. To multiple places. Next guys should be able to find it sooner or later.

> a civilization like this would not leave a trace on the geological record.

At all? Like nothing that would be observable 50M years later?

Put up a plaque reading "This is not a place of honor ..." ?

Thanks! Macroexpanded:

Possible to detect an industrial civilization in geological record? (2018) - https://news.ycombinator.com/item?id=38668884 - Dec 2023 (187 comments)

Silurian Hypothesis - https://news.ycombinator.com/item?id=34755970 - Feb 2023 (60 comments)

Did Advanced Civilizations Exist Before Humans? Silurian Hypothesis [video] - https://news.ycombinator.com/item?id=32837757 - Sept 2022 (1 comment)

Silurian Hypothesis: Were There Civilizations on Earth Before Humans? (2018) - https://news.ycombinator.com/item?id=23654393 - June 2020 (138 comments)

The Silurian Hypothesis - https://news.ycombinator.com/item?id=21840320 - Dec 2019 (52 comments)

Silurian hypothesis - https://news.ycombinator.com/item?id=17899478 - Sept 2018 (7 comments)

It could be as simple as the evolution of fish jaws making the mollusc shell insufficient defense. Or fish eyes/pressure sense/etc developing enough to notice hiding molluscs better. It's plausible that earlier predators were below the threshold of extinction-level risk. Flipping the perspective, humans were below an extinction-level risk for most large land animals for a long time.

The presence of fast predators on land certainly didn't prevent us from evolving.

I read somewhere that cephalopods are kind of like "individual flashes of genius".

They develop large brains very rapidly, with lots of skills, BUT they don't pass on their skills, in part because they die quickly!

This article mentions that:

https://www.nytimes.com/2016/12/02/opinion/sunday/octopuses-...

Despite being mollusks, like clams and oysters, these animals have very large brains and exhibit a curious, enigmatic intelligence.

I followed them through the sea, and also began reading about them, and one of the first things I learned came as a shock: They have extremely short lives — just one or two years.

Other discussion - https://tonmo.com/threads/why-dont-octopus-and-other-cephlap...

---

Humans do seem to have some the longest life spans on the planet, and that's an important adaptation -- "grandmother hypothesis" and all that. I can see that generational knowledge is big deal, even in my own family, and in my coworkers' families.

Or you can look at the family of (ironically) Charles Darwin, with Francis Galton, and so forth

The outliers among primates move the civilization forward. So just having a few people with big brains, who absorb knowledge from their predecessors, is a big deal.

Though of course there could be some cephalopod species that evolved to live 100 years ... and then for some reason they disappeared, or lost that adaptation

One point to note is that humans evolved from apes at a quick pace. I've heard claims that longer life-span, the ability to engage in complex vocalizations, opposable thumbs, upright stance, binocular vision and so-forth are all pretty recent innovation over evolutionary short period, with large brain size turning out to be last addition.

The human package might be not much more complex than "start with a rock-throwing mob and features providing benefits"

So, on the surface, you could have a species that sprinted to all the features required for civilization - and then destroyed itself in a blaze of less-than-glory as we seem on a trajectory to do.

Edit: Note, I should add that I'd actually doubt this scenario could happen only because the evolution of human seems part of the general acceleration of evolution that can be seen throughout geological history.

There is discussion in the article about cephalopod communication, and how they use complex patterning and physical movement to communicate with each other. Is their level of communication and their information transfer speed as high as language? I don't think we can know very well without asking a cephalopod.

Now, that whole section is talking about modern cuttlefish, so I would agree with you regarding the author's hypothetical nautilus civilization.

The cephalopods we observe today would be many millions of years removed from the Silurian cephalopods. It would be like trying to gauge the language capabilities of humans from observing squirrels.

Memorized inherited tacit knowledge around campfires may had been our own specie's cultural medium, but other ways (with slower bitrate) can easily be entertained.

Vocalizations and their evolution were banned from discussion in the Royal Society because they did not leave a fossil record, so even meta-science was harder back then.

Would you count group hunting as “highly complex social behavior”? It’s not just a numbers thing, they communicate and coordinate with the group.

https://www.npr.org/2024/09/23/nx-s1-5120912/octopuses-and-f...

Octopuses also build colonies, using coconut shells and other tools.

https://www.newscientist.com/article/dn18281-octopuses-use-c...

https://www.science.org/content/article/scientists-discover-...

https://mashable.com/article/octopus-garden-colony-deep-sea-...

They can also solve human made puzzles.

https://journals.plos.org/plosone/article?id=10.1371/journal...

As for knowledge transfer, we know that they can teach other how to perform certain tasks. But beyond that, there seems to be a lack of research. Do they have complex language and can they transfer abstract “ideas”? My guess would be yes, but they communicate through color changes in ways that we have a hard time understanding. It seems likely that birds and whales have complex language, but we haven’t cracked the code on that even though their communication is much more like ours. Hopefully we find out some day.

https://www.scientificamerican.com/article/the-mind-of-an-oc...

https://www.forkingpaths.co/p/the-evolution-of-stupidity-and...

Check out the book "Mountain in the Sea", it's based on that premise and is a nebula award winner

> We are terribly preoccupied with tool use and physical artefacts as a defining factor of intelligence

In the context of civilisation, intelligence isn’t enough. Nomadic tribes are sapient, intelligent and have rich cultures, but they aren’t strictly civilisations.

The urban distinction is important because of economies of scale: pastoral societies are energy constrained. That doesn’t make them less interesting, again strictly speaking, personally it sort of does, but it does make them less powerful.

Within the Silurian context, the urban distinction is almost demanding: if humans stopped at Neolithic pastoralism, there is a good chance all evidence of our tool use would have disappeared within a few millennia, let alone millions of years.

tool use and physical artefacts

Maybe but it's also because these things are evidence of cultural transmission - a thing for which there hasn't been strong evidence of in other species and people do look for it in other ways.

When talking about aliens people often use the word "civilisation" to mean just "intelligence" and perhaps that's what you're doing because you're thinking about something that doesn't resemble a human civilisation. I agree with you that an alien intelligence might be very different from a human civilisation. Also, an alien intelligence might not even qualify as a form of life (it might be an artificial intelligence).

There probably is depending on your definition of a civilization. I’d imagine it looks something like an https://en.m.wikipedia.org/wiki/Ant_supercolony

our senses are only equipped to experience small subsets of the whole - there's a huge range of sounds impercetible to human ears, our eyes can only perceive light in the visible spectrum, a dog's nose can detect orders of magnitude more information than a human's.

if the five senses can only percieve a fraction of that which they have been honed for over millennia, it's not unreasonable to wonder if there is much more to the world/earth than meets the eye, inaccessible and unintelligible to physical ape life or existing in ways we aren't equipped to percieve.

yeah, and as far as I'm aware there isn't even a definition of "civilization" or "intelligence" that doesn't boil down to "sufficiently like me".

Trust me, if there were another civilization anywhere near us, we'd be at war with it.

No matter what the other civilization looks like, that's how we've always reacted. It's almost a defining characteristic of our civilization.

This is also pretty heavily explored in Voyager's Distant Origin episode.

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

And in Leonard Richardson's somewhat silly "Let Us Now Praise Awesome Dinosaurs" http://strangehorizons.com/fiction/let-us-now-praise-awesome...

And in Cixin Liu’s short story "Devourer" they even come back to earth for a last visit...

Of course, this has a back-story/history, see "Of Ants and Dinosaurs".

As a wise man once said, "Extraordinary claims require extraordinary evidence"...

> extremely likely

I think you misspelled "unlikely"...?

> It feels like an indictment of the pop-materialist world view, mass media control structures or just our current era of Internet.

Or maybe a triumph thereof? If people now care about what's true and dislike spreading interesting falsehoods, isn't that a good thing?

> Unfortunately, the era of "fact-check" and truthiness has spawned a class of professional debunkers.

This is a reaction to the “alternative facts” and the waves of general bullshit.

> At one point there were those who engaged in debates over flat-earth for the sake of honing rhetorical skills.

It’s one thing to engage in debates with your mates; it’s another to be subjected to a constant barrage of misinformation. Also, a couple of my mates from the “just asking rhetorical questions” period went full conspiracy theorists after a decade or so. I am less and less inclined to think that they were playing the devil’s advocates even back then.

> Flat-earth is typically used as a pejorative at HN.

Well, yeah. It’s the dumbest, most falsifiable of the stupid conspiracy theories, mixed in with a solid dose of religious fundamentalist. It’s not just games, at least not for everyone. Far too many people take it seriously, so it is unreasonable to act like it’s all fun and games.

Conspiracy theory is a self-reinforcing loop and people primed for this sort of thing do jump onto the next one without much critical thinking.

> We haven't entirely lost the ability to have stimulating conversations about Silurians, Atlanteans or other improbable fantasy scenarios, but the trend is approaching.

Fantasy is fantasy. This is not it. If you want to write a book about whatever thing you can think of, then have at it. The problem is when a fairy tale about aliens becomes gospel. So, if you don’t want to be debunked, don’t present fantasies as established facts.

> Today adults crusade against these absurdities without the slightest inkling of self-irony.

> Perhaps other posters can point to the underlying causes.

It's because a lot of the flat-earthers out there on the internet actually believe it. It's no longer an amusing discourse, fun little game or intellectual pursuit for the high-minded playful contrarian, it has transitioned to an actual conspiracy theory with actual adherents.

> Flat-earth is typically used as a pejorative at HN.

As it should be, given the above. It has become part of the wider conspiracy-sphere alongside chemtrails, 9/11 'truth' and all the other crap. It's no longer a sign of high intelligence or curiosity when someone brings it up, if it ever was.

Compare "BirdsArentReal", though honestly I expect that eventually to go the same way.

> At one point there were those who engaged in debates over flat-earth for the sake of honing rhetorical skills.

Do you have any proof that modern flat earthers were ever anything but a silly conspiracy group? The history I know of is of bizarre little flat earth cult groups denying basic science like this, and people outside their bubbles being amazed that they are not being sarcastic when encountering them in the wild.

Denying basic knowledge known since the ancient greeks or earlier is absurd to engage with.

[dead]

> Atlanteans

> Improbable fantasy

You mean as improbable and fantastical as the ancient Troy?

Oh right it turned out to actually exist, after much ridicule of its idea!

If anything, this kind of closed-mindedness is part of the problem.

Dismissing the abundant evidence for Atlantis is hindering our progress of finding it at best.

And now I'm just sitting here imagining tentacles rising up from a puddle, holding a tightly wrapped fish-skin container, to do an experiment in the air.

Maybe they'd think of "going into the air" like early human chemists think of donning protective aprons. Air keeps the chemicals from getting on your skin.

Actually it's the shoe layer.

It's not any particular technical development that separates humans from other animals, but the human relationship to technology as such. Humans only live by way of inserting external objects between themselves and nature, and they do this in an open-ended way. One could also talk about human self-domestication, and agriculture as a self-expanding ecosystem... Fire doesn't really capture the way humans actively modify their own conditions of life.

Why fire? Why is that so different from other tools that require significant effort to create?

Some animals use some tools, but mostly just sticks IIRC, with no effort to creating them, beyond breaking one off a tree. Maybe the criterion 'spend a lot of effort to create a tool' is the criterion, since having the time to spend on tool making requires someone else to get food for you etc. so is that getting towards a civilization?

>In particular, I believe the domestication of fire is the dividing line between humans and animals.

Must there be only 1 line? To me, language is another important one as it greatly increases the efficiency that one can communicate information generation to generation and it seems to have an impact on how we think. Children raised without exposure to language seem to suffer developmental issues, though this isn't well studied given the ethical issues involved in such a study.

As to how much communication is needed to count as a language, that is much harder to draw a definite line given that other species do communicate, but we don't consider them to have a language.

We don't even know when humans domesticated fire, though it certainly long predates the rise of civilization by any reasonable definition.

Certainly fire was a killer app for early hominids, but it doesn't mean it is a necessary step, nonetheless the necessary step on the road to intelligence.

The LAGEOS satellites, which are in an extremely stable orbit and made from dense materials that should maximize their stability, are expected to re-enter Earth's atmosphere in 8.4 million years.

The ones in high orbits would probably remain a very long time.

I wonder if NORAD would have detected it if a satellite remained from the previous civilization.

That was actually put to the test, by really thinking hard about it, around 2018, or so. By serious scientists, not van Däniken types, or similar.

The conclusion was that we couldn't tell, between slowly milled between mile-high ice-shields and fluctuations of seawater-level alone.

Maybe, just maybe there would be the chance of some monument surviving buried in the center of a 'kraton', but why?

Do we build monuments there, now?

Let's do the math.

An adult human at rest breathes about 500mL air per breath, at about 12 breaths per minute. The inhaled air is about 21% O2, and the exhaled air is about 16% O2.

The density of air is 1.225 kg/m3, which is 1.225 g/liter. So 5% of a half-liter breath is, ballpark, 0.03 grams oxygen per breath, which at one breath per five seconds is 0.006 grams oxygen per second.

Dissolved oxygen in ocean water is about 0.008 g/liter. Fish are very efficient at extracting this, up to 80%. Squids and octopi are much less efficient, with octopi hanging out more in the 40% range, and squids much lower.

So this means that for every liter of water processed, an example octopus receives 0.003 grams oxygen, and if such an octopus were able to process two liters of water per second across their gills, they would receive as much O2 as a human.

This is not such an incredibly high number that it rules out cephalopod intelligence, especially when considering size differences.

to save any interested parties a search: groups of 10-15 octopi have been dubbed 'octlantis' and 'octopolis' after being discovered off the coast of Australia. this is remarkable because octopi (including gloomy octopi) were previously thought to be largely solitary creatures which only interact when mating. octlantis features social hierarchies, disputes, and dens fashioned out of the shells of their prey which the creatures have been recorded evicting each other from. interesting stuff

https://www.smithsonianmag.com/smart-news/octopus-city-obser...

I haven't read the paper either but billions upon billions of organisms constantly have some tiny chance of ending up in the conditions where they fossilize and could later be found. A few thousand or million exposed structures over the few-thousand-year lifetime of a civilization is, in comparison, a microscopically smaller chance of preservation. Nature, in contrast, gets effectively infinite shots at this, the fossils record still has gaps that dwarf the lifespan of human civilization as it is.

> how does "They conclude that no ruins of ancient football stadiums, highways or housing projects would survive geological time" square with the existence of fossils?

Broadly speaking, fossils are rare and we site our cities on river deltas and such which have bad conditions for them.

Perhaps it's down to scale? If a single relief of a single building block survives, is that still considered a ruin of a football stadium, or just an imprint of a building block? The Colosseum would certainly not be able to survive for 100 million years. If some intelligent beings find a single building block while doing archaeology, they'll likely not be able to recognize it's purpose, if they even recognize the building block for what it is.

The structural integrity of (comparatively) smaller fossils is much more likely to survive for 100s of millions of years. A large building will be eroded by roots, wind, acid rain, etc. A fist sized rock containing the imprint of a trilobite, buried in soil and safe from most elements, will easily survive for 100s of millions of years.

Or perhaps the author meant that the vast majority of our buildings are not built to last. An asphalt highway - if unmaintained - will be unrecognizable in a hundred years. Roman roads survived for a few 1000 years because of their very crude nature: they are just a pile of rocks. But even such structures will fall prey to soil erosion and the relentless assault of nature. Unless said roads see foot traffic, they'd be also quickly overrun by trees and grasses.

It's a numbers game. The stadiums, highways, etc. are very few and are being built during a blink of history, compared to fossils which typically come from animals that were around for tens or even hundreds of millions of years. The sheer number of creatures that lived and died means we've had a few lucky pieces preserved.

Earth's surface isn't very static. On a geological timescale it is constantly moving and churning.

The fossil record is incredibly fragmented and incomplete.

There are weird structures that we discovered and haven't yet made sense of as well.

The known unknowns in science vast outnumber the known knowns.

We are in a golden age of comedy. There is literally more comedy in wider and deeper streams available for your consumption than ever before.

I prefer Randall W. Carlson.

I'm waiting for it to become octopies.

octopodes