What would be left of a civilization founded in dinosaur times?

Question

65 million years ago, a mass extinction event (likely caused by the Chicxulub Meteor) wiped out the dinosaurs, and their remains were hidden from us for millions of years.

Humanity was not around at the time, and there were no major societies or civilizations.

But what if there had been? What if there had been a race or civilization at that exact moment in history, approximately like our own currently, but with an advanced spacefaring device that allowed them all to leave at once, leaving only behind the ruins of their society?

What would be left over from their society, assuming they used similar methods of construction and had similar cities, factories, and historic periods to our own, that we would be able to find in modern times?

UPDATE:

To clarify, there would be no fossil records of the actual civilization (all their dead are cremated before departure, and their evacuation is 100% complete, pets included) only the artifacts left behind by their civilization (all habitats, entertainment, and food are provided on their escape vehicles, but everything they had is left behind). And they are not humans, but approximately close enough bipedal creatures that they're very similar to humans.

UPDATE 2:

Assume that they won't be doing anything to impact our world. They could be coming back tomorrow, settled on other worlds, gone forever in a horrible accident, but they can't be having an impact on our world, and we likewise aren't going to find evidence of them from anywhere but here.

Answer 1

An industrial civilization on the same technological scale as our own would leave a layer of odd chemistry in the rock, ratios of isotopes out of whack. Here are some possibilities.

Fossil fuels are made of very old carbon where most of the radioactive carbon-14 has decayed into carbon-12. Our digging up and burning of fossil fuels is putting far more carbon-12 into the atmosphere than carbon-14 than would by natural processes. This change in the ratio of carbon-12 to carbon-14 would be detectable in the industrial layer... UPDATE as @Keith correctly points out carbon-14 would have decayed to undetectable levels in less than 100,000 years.

Similarly, there would be elevated levels of other compounds locked up in fossil fuels such as sulfur, mercury, uranium, thorium, arsenic, and other heavy metals.

Any nuclear industry would leave behind nuclear waste. Some waste products are very short lived, but others like Zirconium 93, Caesium-135, Palladium-107 and Iodine-129 have half lives in millions of years. In addition, the stable products they decay to (lead, iron, xenon) would be elevated.

Answer 2

Dinosaur fossils are dug up all of the time. Including things like fossilized teeth. I wonder what researchers would say to a gold nugget embedded in a tooth.

Things like clothing, watches, ... might leave impressions in the stone, just as there are fossils with skin or feather impressions (wikimedia link to Archaeopteryx).

What happens to ceramics in sedimentary stone? At least impressions, I'd guess.

Nuclear waste could make people wonder, or come to completely wrong conclusions about the natural formation of radioactive materials.

Answer 3

The most likely remnants would be Space Artifacts.

65 million years is such an insanely long time that almost anything left will be wiped out, either by natural processes, chemical reactions (oxidation, etc), or even geological events - the continents of the world are very different now, those changes could have destroyed things. Not to mention that the meteor event itself would cause significant destruction.

Now, it's unlikely that you'd find anything in orbit. But you might find ancient satellite remnants in some of the Lagrange points - these are gravitationally stable points between the Earth and Moon, and it's possible they'd collect some of the Dino's old satellites. You probably wouldn't get something entirely intact - micrometeorites add up over 65 million years - but you could get parts that are clearly artificial and non-human. Another possibility here is the Earth-Sun Lagrange points, which are further away.

More likely to be intact would be a space base somewhere in the solar system. Many other bodies are non-active geologically, which will help preserve a base, and if it's buried it's protected from micrometeorites. These could easily be wiped out by a larger impact, though.

Answer 4

Most of the answers so far are focusing on accidental evidence. But since the civilization was able to leave, they obviously knew the event was coming with some amount of lead time. This makes it quite likely that they would've attempted to leave intentional long-lasting evidence of their presence. This might be messages encoded using long-lasting isotopes as others have mentioned, or perhaps messages left on the moon itself, where the materials are less likely to break down.

Answer 5

There would be very few, if any surviving artifacts remaining if there was an advanced humanoid society at the time of the dinosaurs.

There would have been very significant Earth changes between that time and now. If we traveled back to that time, we would have a hard time recognizing the world. Continents would not be in the same place as they are now. Climate and atmospheric conditions including weather patterns would be alien to us. Sea levels would be drastically different. There could be entire landmasses existing which no longer exist today. Mountain ranges that we know today may not have formed yet. Other features that we know well today would not be present like the Great Lakes, Long Island, and all of the other geological formations which were formed by glaciers during the ice ages.

Because of these differences, it would be very tough to pinpoint where to even look for these civilizations in the modern day, even if we knew where they were in the past. They could be deep underwater, or at the top of a mountain, or they could have been vaporized by a volcano, or a meteorite or asteroid collision. These cities could have also been sucked into a subduction zone and melted into the Earth's crust.

If this civilization attempted to come back to Earth after all that time, there would most likely not be any remnants of their civilization. It would all be buried deep in the sands of time.

It may be possible that there could be fragments of their civilization remaining. However, it would be difficult to identify these remains as nothing more than an oddity. Over the years, there have been several claims about people finding artifacts that supposedly came from extreme antiquity. Most of these claims have proved to be dubious or completely unfounded. They are usually just the result of elaborate hoaxes brought on people with an agenda.

Even if legitimate evidence was found, it would be very difficult to prove that it was made at the time of the dinosaurs. There could be some form of advanced technology available which could accurately date these remnants.

There would be very little evidence of the buildings themselves. Any structure made out of wood or metal would have returned to its natural state long before modern humans could lay eyes on it. The only thing that may be left over are features made of stone which may have been buried millions of years ago and preserved.

Answer 6

There would be abundant fossil evidence of their buildings, tools, art, technology and trash. As abundant as other fossil evidence from the same period, at least, which would be plenty to show many clues about the civilization.

Consider: How do we know that dinosaurs existed at all? Fossils from their time. We also have fossils of plants, insects and microbes from even before their time. If as you say they left behind entire cities, and had a pre-modern history, there would be many fossils left of all the stuff they built and made and wore and littered and lost and so on.

The oldest insect fossil is about 400 million years old. Here's an insect wing from over 100 million years ago: http://en.wikipedia.org/wiki/Necroraphidia#/media/File:ZooKeys-204-001-g004_Necroraphidia_fig1.jpg

Given the right circumstances, such as ash or mud suddenly covering a town and later being uncovered, there could be decent archaeological sites too, although they might be sites of fossils and impressions rather than intact objects. Major constructions could leave recognizable traces too: roads, aqueducts, industry, dumps, scrapyards.

Answer 7

Some salt deposits were created 250 million of years ago in geologically stable areas. They have remained undisturbed until humans start burying the waste of nuclear centrals, see why the U.S. government chose salt mines to bury long-lived radioactive wastes.

It would be the most obvious place to bury artifacts for the benefit of later civilizations. With no running water and humidity, you could even get away with storing paper!

Answer 8

It seems to me that the subsequent evolution of Velociraptor, some million years before dinosaur extinction, would be the place to look for potentially intelligent species. They were effectively bipedal, forearms with claws for manipulation, and social (hunted in packs). One idea: if some brainy dinos survived (or anticipated) a mega-collision, other than leaving Earth, they could have moved underground? I speculate that extraterrestrials described with large eyes are evidence of subterranean life (after all, where could you live on Mars or on bombardment-likely planets but underground? John Caddy

Answer 9

Great question.

Many of the products of civilization could survive, particularly large structures, and items of particular metals.

I'd expect most of these to be deeply buried in strata, much of it inaccessible.

However, if the civilization was global, some areas of land surface would survive and hence be able to show traces. For example, most of the Australian continent was around 65M years ago or longer.

It's not obvious to me that one should look in the regular fossil beds, but I stand to be corrected. Such sites have a duration that might be very long relative to a civilization. Presuming that they represent swamps or river or lake beds, I guess a certain amount of junk might end up there, but not necessarily.

I agree that isotope anomalies the nuclear industry might be an indicator. However, if one does not find the site of a reactor or accident, I do not know that the overall environment would leave evidence in the strata.

In conclusion, I suspect evidence would be somewhat hit and miss with not a lot to show for it today. At the same time, I think that means that a civilization of our current level of industrialisation or above would have left a fair amount of evidence scattered around.

Answer 10

I've seen this question asked elsewhere many years ago. The most convincing answer for me was that EARTHWORKS would be fairly easy to find millions of years later. Any advanced civilisation would rely on metals and getting them from the ground often involves opencast mining - leaving a huge pit in rock which will tend to be filled in such a way that its purpose is clear to future archaeologists.

Answer 11

The easiest way to detect such a civilisation after 65 million years is to look at its effects on other life. You'd be looking for geological evidence of a mass extinction 65 million years ago, like the one that's in progress at present, as the dinosaur civilisation expanded and used up the available biological resources for itself.

Answer 12

Mines and mineral deposits. Many of the mines humans have exploited through history were formed long before 65 million years ago, which means those resources would have been there for some civilization to exploit, but yet those deposits were untouched prior to humans working them, indicating no one else had been around to exploit them first.

If one had, that's a huge honking clue. You'd find things like underground deposits where what should be the richest ore was missing, replaced by what looks like filled-in tunnels that show unnatural regularity. You'd have surface deposits where, again, the richest ores were missing, leaving a halo of surrounding lower-grade rock surrounding a plug of sedimentary rock, what you'd expect if someone had been open-pitting and the mine had gradually been filled with sediment. You'd see areas of very fine mudstones with disseminated minerals that looked in no way natural, the remains of tailings. And so on and so forth.

Now, mines tend to take up a geographically small area so the odds of just stumbling on the remains of one a few million years old are small, but their locations aren't random; they're determined by geology a lot older than this hypothetical civilization, and where they'd mine is where we'd currently be looking for things to mine. Someone, at some point, would have stumbled on something so freaking anomalous that everyone would know about it.

Answer 13

A civilization advanced to the point of leaving the planet before a catastrophy might as well have the means to restore parts of it to its previous state. They could, for example, build some sort of "Noah's Ark", where eggs and embryos (or the genetic information) of the most threatened species could be stored, allowing them to repopulate the Earth after some time. In this scenario, the "leftovers" of such a civilization would be dinossaurs surviving up to our time.

Answer 14

See this paper The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?

Looks like Nitrogen-15 level would be a tell (fertilisers), also Plutonium-244 (half-life 80.8 million years) and Curium-247 (half-life 15 million years) produced by nuclear industry, also some specific chemicals:

steroids, leaf waxes, alkenones and lipids can be preserved in sediment for many millions of years (i.e. Pagani et al., 2006).

Answer 15

Imagine if the human civilization suddenly ceased to exist. What would a future geologist or paleontologist find of our civilization. Assuming it is 65 million years after we're gone, not much. By this time, metals have been corroded, concrete structures such as sidewalks and damns has been eroded away and plastics have been biodegraded. Most of our satellites have fallen back to earth by this time. Unless for some miraculous situation where a bunker or sanctuary had survived for this amount of time, the only safe place is space.

However, some of our spacecraft, including the voyagers would survive to this time, assuming nothing went wrong.

Even if a dinosaur civilization did develop in the Cretaceous, any surface structures would be long gone. A subterranean bunker would stand a better chance of surviving, especially if it was far enough away from fault lines where volcanoes and earthquakes wouldn't be a problem.

As a space faring species, if they were as advanced as us, the only place they could really go is mars, but even that is unlikely.

However, no one can say with certainty that a dinosaur civilization did NOT exist.