If dinosaurs had a civilization, how primitive must it have been to leave no trace in the present?

Question

I am thinking of, yes, a simple story with intelligent dinosaurs, but I am not interested (And I sincerely prefer) that they are not sufficiently advanced in my history to be comparable to modern humans, at most I imagine them similar to the humans of the Neolithic. BUT, if it is in any way possible that they could be more advanced without leaving a trace in the world I would like to know. If, on the contrary, they need to be even more primitive than Neolithic humans in order to not leave traces of their existence, I will understand, I just want to know.

What I want is to make it almost impossible to prove that they existed, at least for now.

Some details are; In my story there are not several species of intelligent dinos, only some variations of troodons. I imagine them only having 4 or 5 towns or cities in an area of ​​only 40 km. They haven't "spread" around the world or anything. They are basically the first "cities" in the world. I imagine them having primitive wood and stone weapons, art made of wood, amber, and maybe stone, and a couple of religions. I imagine them having a social leader (a king?) And a religious leader, only these would wear clothes and it would only be partial. Maybe the warriors or something could wear ornaments made with their own feathers or those of other species of dinosaurs.

Answer 1

Are there likely to be some traces? Some tools? Some evidence of culture and burial rites? Maybe, and maybe not. Depends upon where the intelligent dinos lives, and what happened to that rather small place afterward.

65 million years is a mind-bendingly long time. And a lot can happen in that time.

• The Pyramids have been around for 5,000 years. You're looking at 13,000 times longer, enough for half the volume of hard granite to be weathered away. It will be much smaller then.

• Niagara Falls erodes roughly 1m (3 ft) annually. 65 million years is much longer than needed for it to erode past the Canadian Shield and all the way to the Pacific Ocean...were the river long enough.

• The mighty Himalaya Mountains are only 50 million years old.

But let's just look at the BIG NEWS events.

• Ice age glaciation occurs every 40,000-100,000 years. You're looking at around a thousand ice ages, each scouring the north and south.

• Tsunamis occur about twice each year. You're looking at over a hundred million tsunamis scouring clean everything at sea level outside the glacier zone.

• Tropical cyclones (hurricanes) form around 80 times each year. That's over five billion ravaging the tropics.

• Magnitude 8+ earthquakes happen roughly one each year. Magnitude 9 earthquakes are estimated at about 1 per century. That's still over half a million.

• A volcano erupts about once each week. Over three billion eruptions, including some mighty big ones.

Cities near the sea will be smashed, flooded, buried in sediment, decayed in swamps, eroded and exposed, overgrown by jungle, scoured by ice, and re-buried...many times.

Cities in the hills will wash away with those hills. (Look what the Grand Canyon has done in only 5-6 million years.)

If an advanced culture left a cache sealed deep inside a reasonably stable, impermeable strata, we might find the cache (those pesky earthquakes and volcanoes might destroy the cache). But we're unlikely to find anything else. And the intelligent dinos in this question lack that capability.

Answer 2

You can basically do what you want!

You say your civilization is not spread around a very large area. (40 km across)

You just have to place this civilization on a part of land that is not suitable to carry fossils and be excavated today.

To help you choose a place that suits your story, maybe This interactive map will help

If you want to make extra sure, give them a burial ritual where their remains are burned and their belongings crushed to dust on what was then the shoreline to be washed into the sea.

Answer 3

Very primitive

As mentioned in another post, there are lots of relics that are still found of humans. Although dinosaurs have the advantage of being much older, we are still finding well preserved fossils in certain strata of the earth. Any tool can become stuck in a strata, or even just leave an imprint, which will have historians break their heads how this is possible. It might be possible to have some tools in area's where preservation is unlikely (not being covered quickly by earth, amber or whatever). If there are few tools enough, it might be put down to a mistake in dating, or that the preservation makes it look older than it probably is.

What is possible is an advanced social structure. Social structures can be inferred by how the dinosaurs are located by historians, but this is unlikely. There aren't many fossils of even the recent dinosaurs. The dinosaurs that are found require something to happen for it to be well preserved. This often means that a lot of context is obliterated, making inferring social structures very difficult if not impossible.

A social structure and no tools also makes more sense for dinosaurs. There are too few that would be able to build and use tools due to their physiology. Humans (and primates) are uniquely build for this. There are a few other species who use tools, like dolphins, but they mostly use the environment directly. These tools would either disintegrate or be unidentifiable as a tool. A Diplodocus ripping off a branch and using it to fend off an enemy would be difficult to see after so many years.

A social structure can involve anything from gathering food for your fellows to complex grieving rituals. Time and bad preservation will likely remove all of the evidence.

No agriculture would be possible though. Besides the difficulty of them sowing and tending crops, these area's might be seen more easily due to the traces in the sediment.

Answer 4

Not Necessarily Primitive, But Certainly Different
One of the universals of human culture is tool making. (This is different from tool using, which as we know many animals do.) Shaping stones sufficiently to make them into tools leaves an essentially permanent record of not only the tools' existence, but also a record of the culture that made them. This in turn leaves a record of the intelligence of the species as a whole. In other words, we don't just see evidence of a handful of ancient cities and absolutely nothing from other humans. All of these activities will leave evidences that can last, essentially indefinitely.

Looking at the fossil record from the saurian age, we find not only fossilised bones, but also eggs, nesting sites, some wood, amber, and even impressions of feathers and skin texture. If your saurians are engaging in tool making and any kind of construction or intentional rearrangement of the natural environment, they're going to leave a trace.

This means your intelligent saurians have to be quite different in their cultural basis. If you want for their civilisation and their cultures to remain entirely without trace, then it's quite simple: culture must not be material in nature. Their culture must be entirely oral (if they speak and use language) and entirely cognitive in nature. The only things that can ever be produced by these kinds of cultures is aural ephemera: stories, legends, myths.

How to do this:
They'd basically have to be wired in the brain to balance intelligence with intense acuriosity; the ability to construct complex and deep levels of cognitive structure without the desire to manifest those structures in the physical world; an entirely spiritual understanding of self, community, and world completely divorced from the physical world around them.

They could construct extremely complex and time deep societies without ever having to shape a single stone or piece of wood to do it. They'll be helped by already being excellent hunters and fighters. Their bodies already provide them with all the tools they need to survive: tooth and claw. They don't need to farm, they don't need to make clubs or swords. They just need community in which to evolve this wonderful and fantastic culture!

Answer 5

Human Blindness and Scientific assumptions:

Every so often, people find strange bits of metal and ceramic-like material in stones. Odd regular shapes turn up in long, strung-out geological arrangements like roads. Jewel-like stone shells can be found in museums around the world - they're beautiful, if you care to go the the Smithsonian and take a look.

Does that mean we've announced to the world that there is an ancient Reptoid civilization? Okay, yes, some people have. No one takes it seriously. They assume things are natural, or fossils, or strange geological formations. Ancient machines people insist must be computers turn up, but there is always an alternative explanation. Nature does tend to produce things that take on extraordinary repetition and apparent organization. Folks assume things come from contamination of fossil sites.

In a world where there had been an ancient (REALLY ancient) civilization, almost everything would have disintegrated from the original form. We're talking orders of magnitude longer than the remains of stone tools from early man. Fossils of worn artifacts might turn up, but that would just mean people would identify these as a certain genus of plant fossil, or a unique erosion pattern. People would find things that defy explanation - and throw them in the discard pile because they assumed the overseer dropped a broken tool. Archeologists today are re-excavating the midden heaps from old archaeological expeditions because the early archaeologists made broad assumptions about what was important.

There would certainly be a few visionaries and crackpots that would announce to the world the ruins of ancient cities, but the experts would point out there were similar formations near the mouths of every river from the time, and attribute it to a primitive form of tree growing on mineral deposits in river deltas (now extinct). The cranium of that iguanodon relative was really big, and you think it could have had opposable fingers? Well, those are vocalization chambers, and they used those manipulators to pick fruit, of course.

So while there might very well be some evidence of an ancient civilization, no one would take it seriously and anyone who did would be laughed out of scientific circles. After all, those weird little shells are ALL OVER the world, and that type of shell always had a really high aluminium content in it.

Answer 6

If your entire dino civilization was localized to a small area that was right underneath the Chixhulub impactor, then they could have been relatively advanced and almost all evidence would have been obliterated by the impact.

Unfortunately, per all the paleomap reconstructions I've seen, there were no large landmasses at the impact site around that time; what would eventually become the Yucatan peninsula wouldn't emerge until something like 40 million years later. You could maybe handwave that away by having an island or island chain in that area, which would also help explain why the civilization was localized in the first place.

Answer 7

If your civilisation is restricted to a small area, and won't leave any chemical record widely around the earth it is virtually impossible that they would ever be discovered. Fosilisation, for example, is incredibly rare and most of earth's surface is actually from after about 3m years ago.

Most of my information comes from here

But this is a distillation of the information in:

Gavin A. Schmidt, Adam Frank. The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record? (pdf) International Journal of Astrobiology, 2018; 1 DOI: 10.1017/S1473550418000095. Or see a summary here

To actually answer your question, you don't have to do anything, you could actually have a widely distributed industrial civilization almost as advanced as our own, and we probably still wouldn't detect it after 65 million years.

Answer 8

Any level of advancement, if the location was somewhere hard to access today

Expanding on my comment, because no other answer has addressed this. We would not have stumbled across evidence of an ancient civilization if it was under water (think - there were probably villages on the Bering land bridge during the last ice age, but there's no chance we'd discover them). We also wouldn't stumble across archaeological evidence if it was buried under a deep glacier in Greenland or Antarctica.

Your civilization wouldn't have to be confined to 40km^2 if it were on a "lost continent". I mean, they could have cars and trucks down there. Hiding it in Antarctica might be a good idea for your plot, so you can have the evidence discovered by researchers in the modern day (as opposed to "stumbled across" in the 19th century).

Answer 9

See these stone tools in an museum exhibit:

These have survived to modern day. So none of these things can be made in your civilisation. No arrow heads. No spear heads. No morter and pestle. No cups. No jewellery. No axes. No knives. No saws. Basically you cant enter the stone age.

You can make things out of wood, but you wont have any tools to work that wood into decent shapes. You'll need to find branches close in shape to what you need and then "that'll do" it. This does leave some interesting opportunities for building a society:

You will be able to weave things out of reeds, strap thick branches into a structure with vines as lashings, and cover roofs with dried grasses. Simple huts are very plausible.

You may be able to have rammed earth walls on your structures too, for a bit more weather resistance or for indoor fireplaces. I'm assuming theres a good chance this land will get flooded many times over the next millions years to erode the walls.

You'll be able to dig irrigation channels to fertile farmland. Probably cant have viaducts or dams without risking leaving a trace, dams may leave water level hints.

Paths would get flattened by use and become roads. Simple wooden sleds for carrying loads can be used. Wooden wheels are possible and unlikely to survive.

Answer 10

Many tribal societies today will have no archaeological record in a thousand years, much less millions of years

We don't really know how far back our own civilization goes because evidence of early man is so degraded and hard to interpret. There are many primitive technologies that we only know about because modern tribal societies make them, but they have no way of lasting for very long unless preserved by a very rare and well timed fossilization event. Such events are so rare that you are more likely than not to have an entire civilization rise and fall without it happening once.

Tool Making:

The beginning of our own tool record begins with a technology called stone napping: a technique of chipping stones against each other to make a sharp edge, but we have no clue how long man was making un-napped stone tools or non-stone tools before that. Napping is easy to identify, even if a tool is somewhat degraded because it is so clearly unnatural, but it takes a lot of skill and dexterity to make. When you look at primitive civilizations today, many of them prefer ground stone tools because they are easier to make, but they also closely resemble the effects of natural weathering; so, when we find ground stone tools, we can rarely make conclusive statements about if they are tools or just random sharp rocks. If your dinosaures don't quite have human levels of dexterity, they may be stuck making ground stone tools indefinitely, even if they are just as smart as humans.

These examples of ground stone tools would be almost impossible to identify if they were not found alongside other signs of civilization, and these are not nearly as old.

Then there is fire-sharpened wood. A stick can be sharpened and hardened by burning the end in a fire and grinding the tip into a point. Tribal societies today often make their spears and arrows this way and they are nearly as sharp and hard as stone, but since wood rarely lasts for over a couple of centuries, a civilization could make 10s of thousands of such tools and not a single one would last anywhere near as long as the time frame you are asking about. Similarly, your civilization could practice weaving, textile making, leather working, and various other crafts involving organic materials and no one would know.

It is even possible your dinosaurs could discover iron working since iron tools rarely last much longer than wooden ones, but if they do this, they will probably also discover ceramics. You want to avoid them having ceramics since this will be the most likely thing to survive that long.

Housing:

There are a lot of ways to make a house that don't last long. Compressed Earth, wood, reeds, hide, etc are all used as building materials in primitive societies today and have basically no chance of lasting for very long. Now let's say your dinos are a bit more advanced than this and decide to make stacked stone structures. These tend to fall apart and just look like unusually dense concentrations of buried rock after a while. Since many birds make nests out of things like stones, we could find an entire dinosaur city, and just assume it is some kind of dinosaur nesting ground that started off as just piles of stone. We'd think it's neat, but would not jump to any conclusions of particularly intelligent design.

It is also possible your dinosaurs build their homes into the ground, but many uncivilized animals build burrows too: bears, snakes, frogs, meerkats, etc. So, you could likewise find an entire city of dinosaur burrows and not even consider this a sign of civilization.

Clothing:

While it is true that soft materials like skin and clothes are sometimes caught in fossil records, this is VERY rare. We have no more than a dozen or so fossiles of nearly any given dinosaur species, and very few of those have preserved any such details as skin. It took nearly 100 years of archaeology for scientists to realize dinosaurs in general where feathered animals, and that is while looking at the remains of every single dinosaur species over a period of over 200 million years. If a single species of dinosaur had a civilization that only lasted a few hundred thousand years, then the likelihood of there being a single surviving fossil showing it wearing clothes would be slim to none.

Answer 11

We have found dinosaur bones. Something made of stone (let alone metals) would be at least as durable as those bones. So you are limited to stuff that doesn't end up preserved or that doesn't end near those preserved dinosaurs.

You can't have simple stone tools or weapons, because at least SOME dead dinosaurs should have some tools nearby, or you need a very convenient excuse why they wouldn't.

You could have wooden wheels, stone/wooden houses, paper etc, as all of that will be long gone in those millions of years, while houses destroyed dinosaur bones when they shattered ... But how would you explain existence of those things when they lack stone tools needed to make them? That I do not know.

If you are willing to handwave quite a lot, you can simply proclaim that those advanced settlements and surrounding area were completely wiped out by earthquakes, volcanoes or whatever else. Those bones we have found would be of dinosaurs that weren't in or near the city when disaster hit. Perhaps their spiritual folks traveling from place to place preaching about dangers of using stone ("bones of the Earth").

Answer 12

An unusual setup is an advanced civilization which chooses to live perfectly integrated with nature. Think of "the Nox" in Stargate SG-1, but ignore the flying city. They might have "magic" powers.

Your beings could use telepathy, teleportation, telekinesis for feeding, communicating, defending, hiding, healing, traveling. They can use their abilities on themselves, or on others. They can affect equally living matter, and non-living. I do not know yet if they can resurrect the dead, you have not yet decided on this matter :)

Living in natural burrows or caves, and using only plants / wood for anything they need (shelter, food), they would not leave a trace even after 50 years.

Remember, they do not need any stone / metal tools, since they can do everything mentally. So there is nothing to be left behind.

Answer 13

What is a civilisation? It's entirely plausible to have a civilisation with neither tools nor permanent records, but with a high degree of culture based on oral history and embellished legends presented by bards at periodic eisteddfodau.

Answer 14

"Primitive" is a loaded term, which is why it would not be used by a modern athropologist.

Let's consider, rather, an extremely advanced society, one far in advance of current humanity. They live in peace, with no crime, poverty or disease. They live in harmony with nature, with no need for technology. (Perhaps they do it all via spiritual strength or psychic power, maybe it's a form of biotechnology; hard to tell) They are, essentially, living in a state of paradise: but there is nothing for future paleontologists to puzzle over.

Simple answer: they can be extremely advanced and leave no trace if you're looking for the wrong thing.

Answer 15

More advanced than ours. After industrialisation caused CO2 levels to rise from 1200 to 2500 ppm at the end of the Jurassic, the Silurians invested in all manner of technologies to remove all Sauroprogenic effects on the environment, nanotech removing all trace of previous industrialisation and only using materials which biodegraded completely in a few centuries. This tread lightly philosophy led to their civilisation continuing to thrive for many millennia, but leave no trace.

Answer 16

Saurian Sapiens (to give them a semi-sciencey name) evolved in what would later become modern Africa from a creature similar to Troodon

Unlike humans, they never left their cradle continent to spread across the world. Their metabolisms and tolerance for different environments is significantly lower than that of humans. Consequence of their smaller body-mass and biology. Their high intelligence and social nature combined well with their omnivorous diets to increase their brain-mass.

They built their society on river-deltas and coasts and their biggest challenges were the much larger predatory dinosaurs.

Their numbers were never high far from their communities a matter of a couple million all told, but they did well enough for a few thousand years at a stone-age level. They had tools, homes, art and a strong tradition of history, they even developed weaving, writing and a theory of mathematics.

The Chixhulub impactor killed them all. The plummeting temperatures were unsurvivable and the tsunamis wiped out their coastal towns entirely.

Humanity has not found evidence of them simply because those that weren't in towns largely weren't fossilised, while the ones in the towns were destroyed wholesale and their bodies scattered or buried under tons of mud.

There may be remains to be found 65 million years later. A variant therapod with an enlarged brain, hints of small stone or bone tools here and there. But without intense study, those tools are quite similar to stone age human tools.

It is vanishingly unlikely that what little evidence there is will be interpreted correctly, even if they are found.

Answer 17

I think primitive hunter gatherer nomadic tribes (though personally I think agricultural may possible too, considering some that as far as I know is still debatable regarding its existence as myth civilization or not). Either without houses or making their houses out of animal skin with branches as support. Since I believe your dinosaur can manipulate tools, use organic materials except stone and bone as @Ash has said, except I believe some of your dinosaurs have sharp teeth or strong teeth to chew bark or the wood or branch, so I think they can craft it using their mouth.

And I suggest not to use burial but use cremation, assuming your dinosaurs know how to make fire or doing corpse cannibalism or eating the different species' corpses in that society (assuming it was a multi-species or -ethnic dinosaur society) and crush the bones to ash to leave no trace.

Answer 18

They need to be Pre-glassblowing

Time is the big issue, very few things can survive tens of millions of years, metals and organic materials breakdown, stone tools become degraded, even pottery suffers water damage. Fossils from that long ago are never completely intact even well preserved material suffer cracking and chemical degradation. As long as the civilization is using natural materials their existence will be contentious. Consider how few fossil bearing deposits there is as you get older in time, it is entirely possible for nothing conclusive to survive. Metals are not good enough because metals tend not to survive on their original shapes in sedimentary environments. Even pottery suffers chemical alteration which will destroy it. worse it is too soft and has no real chemical distinction so confusion for concretions or even biologicals trace is too easy.

Blown glass however is a dead giveaway, smooth edges, purity, chemical stability, hardness, all favor long term preservation of glass. A glass bottle in good burial for a hundred million years will still look undeniably like a glass bottle and will not be confused for any natural glasses. Its chemistry and shape leave little room for interpretation. Now of course most glass will not survive, physical weather will destory most of it, but it only takes a few cups or jugs in fossilization like conditions to leave undeniable evidence, and preservation of glass is likely becasue it is chemically inert burial and ground water has no effect on it. Blown glass is both physically identifiable and chemically distinct from any natural glass, the removal of impurities and variety of still purposeful shapes makes it impossible to confuse with natural glasses, including biological ones.

keep in mind this covers most of human history, you can even use early Roman history. Location can play a lot in this. If the center of your civilization is around a major mountain building zone most of it would be completely erased. If there was a civilization on the northern coast of India 50 million years ago we would have no idea.

Answer 19

Keeping them on the primitive scale you picture could work with no known evidence of their having "achieved" that.

Consider all the things above about physical evidence, then consider that we might not even realize evidence existed. That doesn't apply to troodons, I suppose, but consider anything a fair deal larger would have houses, for example, on a much different scale than humans. Posthole remnants, often all that remains, would look more like circles in very old henges, if one even realized they went together because of the out-of-the-box scale. Like the recent enlargement of the scale of the Stonehenge site. Eventually realized, but... "eventually"... and archeologists are like anyone else, not wanting to have everything they do ridiculed because they dealt seriously with a workers' "campfire story" conflation (?... or was it?) of odd pieces of evidence. Could take a LONG time for serious analysis.

But... in the example we have, human history, seven million years or so of differentiation was needed to reach the "a few small cities" stage and there is a lot of evidence along that time path. So that would be there. Just how much would ever be in places we would explore is the question. If it was inside a reasonably new mountain, well, even construction projects might never find it, much less notice it.

(Funnily enough, the ones most likely to interpret any such evidence correctly, the "it was ancient aliens" crowd, is also the least likely to ever really want evidence to interpret.)

And evidence can be misinterpreted too, giving rise to longstanding, unimpeachable beliefs that impede scientific explanation in various ways. What are two (of many) things common to people almost everywhere? One is fossils exposed by weathering, even in mountains, many of fish, thousands of feet above any known sea and far from them all too. Another is flood myths. Find a fossil fish a mile up a mountain and 500 miles from sea and a flooded earth story just makes sense. And might easily be more believable with a god as the agent since no natural event floods anything, much less the whole earth, a mile deep for the fish to get there and die. Another common myth is misshapen monsters. Ever seen some of those fossils folk find? We have common ancestors, the basic bones are all there, the heads misshapen, the proportions wrong... must be monsters and see the size??? Gods and their enemies... Even give them animalistic interpretations and all you see is monstrous animals, not normal, natural ones. It is all so easy. Hence my belief archeology might go a LONG LONG time with evidence they shoehorn into sketchy seeming explanations backed by "I'm a professional archeologist and you're the fellow who balances the IQ scale at 100." Or just shove them into a shoebox and store them to never even film for outsiders to view, much less see or handle. A fairly small-scale four-five town civilization might leave traces that no one ever put together.

Then the comet hits and that's that.

However, all that aside, you cannot take them much further along the scale. Let them reach a fossil fuel burning level and the fossil fuels are GONE. Never to be renewed as the activity that created them cannot happen on any meaningful scale ever again. We WOULD have noticed that and if enough were left, we would have advanced to the point where we realized a great deal had been used up. Might not have to go far along the path either because coal miners would surely have discovered enough evidence to get people thinking. It simply couldn't be missed for long, and would have been discovered long before we got going discovering our own past. (Might even have kickstarted that archeology, actually.)

And we would have never reached our current place in the sun. Wouldn't worry about what came before, just curse it.

By the way, it's not a pretty future for our own species if we peak and fall back. Kinda hard to go from campfires to nuclear reactors in one step. Even windmills like today's take a lot of tech advancement.

So a fair ways back on the physical advancement path could probably slide under the radar pretty easily. But much more and it would start to be difficult to picture. Those fossil skeletons we find, they made it. One thinks a stone or concrete building or two or ten thousand could survive with noticeable over just as long a period would not be hard to picture either.

Answer 20

You can discern tribal society and civilization. Humans went through a tribal phase prior to becoming a civilization. The tribal phase was the same as Aboriginal Australia or North America prior to European colonization, tribes living in wigwams and caves.

Humans only made civilizations when they had genetically selected crops that could generally provide a lot more food than wild crops, and then they can make dinosaur stone henges.

Caves are awesome for preserving artefacts but they rarely last for 65 million years, unless you found some kind of special cave which hasn't turned to rock in that time. Stone tools can last that long, so any kinds of stone tools which precede a civlization by about 1 million years, and art on bones and sculptures, which span about 0.1 million, are probably the kind of technologies that would be easiest detected later.

Answer 21

Everything Leaves Behind Evidence

It would have to be so primitive that calling it a "civilization" wouldn't be accurate.

• They can't have tools. Those show up in fossil records.
• They can't have written language or art. That would show up on rocks and in caves.
• They can't have burial rites. Archaeologists would find graves.
• They can't have agriculture. That's easy to infer from fossils and artifacts.
• They definitely can't have metal anything. Metals nearly exclusively exist as ores naturally, so finding a chunk of solid rusty iron is automatically suspicious.
• They can't have money because that would show up in fossils even if it weren't metallic. ("Hmmmm... this T-Rex fossil appears to have 50 seashells by its pelvis. Maybe it's money or something")
• They can't have permanent structures. These show up in digs.
• They can't have clay or brick. Pottery shows up, even if mere fragments.
• They can't have cities. Those not only depend on other technologies that would leave a trace, but they're really obvious in archaeological records.

65 million years is a long time, but not long enough to erase evidence of a civilization.

The most you can really do without leaving evidence is talking dinosaurs with a deep oral tradition.

... Unless ...

There would need to be a god or sufficiently powerful being who can erase all evidence of dinosaur civilization, preferably one with a really good reason to do so.

This is pretty handwavey, but it gets the job done.

Answer 22

The absence of proof of a dinosaur civilization is not proof of absence.

We can look to our own civilization as our technology evolves. In our earliest artifacts, function dominates form. Ancient arrowheads are easily recognized even though the cultures that made them are distant memories, whose only existence is often only told by the same stone arrowheads. Fast forwarding today, and the smart phone whose form trumps its function. It's designed to fit easily our hand and a pocket and to be pleasing to our human esthetic sense. After 50 million years, exposed to weather, erosion, and geological forces, nothing would remain of a cell phone, or at least nothing recognizable to hint at its original nature with the organic plastics and glues, and metal and semiconductor components ground down into so much muck and gravel.

The obvious object to this statement that nothing would remain is to point to our great buildings, surely they would remain and I think that there would be something remaining, especially facilities we built to withstand nuclear attack. They'll last as long as mountain ranges I expect. But this objection supposes that dinosaurs needed or wanted to buildings.

We, as hairless primates, need to create our own shelters, but a sapient evolved from dinosaurs could imaginably not want artificial shelter, or might find organic based shelters more esthetically pleasing. Harry Harrison's 'West of Eden' posits intelligent dinosaurs that excelled at biological technology, and could alter living beings to be weapons or factories. When a culture like that died out, its footprint could imaginably fade to nothing in a few thousand years.

Answer 23

Even human civilization as it is now might be completely lost in deep time.

A lot of people might think of fossils as unavoidable evidence for past species/civilizations. One thing that is not generally realized is how exceedingly rare fossils are. To quote Bill Bryson in "A Brief History of Time", Chapter 21:

Only about one bone in a billion, it is thought, ever becomes fossilized. If that is so, it means that the complete fossil legacy of all the Americans alive today—that's 270 million people with 206 bones each—will only be about fifty bones, one quarter of a complete skeleton. That's not to say of course that any of these bones will actually be found. Bearing in mind that they can be buried anywhere within an area of slightly over 3.6 million square miles, little of which will ever be turned over, much less examined, it would be something of a miracle if they were. Fossils are in every sense vanishingly rare.

Combine that with tectonic subsidence, glaciation, meteor impacts, lava flows and just general erosion and in 65 million years everything our civilization was would be long-gone dust. Yes, there might be the equivalent of a granite dinosaur statue buried somewhere - finding it is a different matter.

Have a look at this article in the Atlantic for some more perspective how deep deep time really is. An advanced industrial civilization will leave some chemical and radioactive markers in sediments, but those could be interpreted as natural processes - even nowadays, there is no guarantee scientists are not seeing some kind of vague evidence for previous advanced civilization and holding it for a natural process.

I would say, you are safe to have a pretty advanced civilization; even satellites launched by it would not stay in orbit that long.

Answer 24

Very advanced

Consider a civilisation that discovers something so terrible that they choose voluntary extinction to ensure that any future civilisation is not exposed to it. In doing so they go to considerable efforts to hide any trace that they ever existed; even things that we haven’t so far thought to look for.