A civilization emerges briefly at the end of Jurassic. What geological evidence would we find today?

Over in this thread, a hijack has developed over whether a very ancient and briefly-lived civilization would leave any traces of itself in the geological record.

Or, put another way, if a civilization similar to ours had developed and flourished briefly at, say, the end of the Jurassic (about 145 million years ago, but let’s say 150 million years for the sake of discussion) would we notice it in the geological record today?

Bear in mind that our own civilization had its beginnings less than 20,000 years ago. This is a blink of an eye in geological time. If our civilization wiped itself out tomorrow, what evidence of our time on the planet would exist in 150 million years? Given the brevity of our civilization, would it be a needle in the geological haystack? Or would there still remain some obvious and unmistakable sign that we were here?

Would a future paleontologist have to get really lucky to notice our works? Or would paleontologists be stumbling over us, or signs of us, at every turn?


How long did it live? There are lots of potential traces - if it was developed enough. Strctures won’t last, but if we started finding extremely high concentrations of radioactives in very small areas, it would be strong evidence of a civilization. Or we might well find evidence of iron depletion in places we strong expected to find it, or whole mountains chewed away for ores. Now, these would require a more developed civ than you might be talking about.

An even better piece of evidence might be fossils. If we find a lot of very stable burial sites, with unsual materials in the rock, that would be good evidence.

That’s the big “L” variable in the drake equation: http://en.wikipedia.org/wiki/Drake_equation. How long does an average civilization last?

I tend to think that if civilization ended tomorrow, civilization would be the stranger marker-bed where (assuming there was active sedimentation during) you get weird stuff like cars and freeways and plastic bags. Even if 99% of it disappears, there’d still be some evidence some places. It’d be very handy for establishing relative dates. Future alien geologists would flock to areas where the weird-ass humanity horizon was well-exposed.

Junkyards full of analog TVs would be a dead give away if ours ended tomorrow. :slight_smile:

I’ve often wondered the same thing. My guess is that there would be some trace of civilization. In our case, future paleontologists might come across some really large-brained mammals that seemed to suddenly flourish in the blink of an eye - this might tip them off to our intelligence. Then if they honed in on strata from that time period, they’d probably find other evidence as well. I’d bet landfills will look pretty interesting to a geologist in 100 million years - strange pockets of metals and complex organic compounds. Perhaps they’d stumble upon a nuclear waste storage facility, and be stunned at the large concentrations of ultra-pure radioactive actinides. And of course, if they ever sent a satellite to map the moon they might have a 2001: Space Odyssey moment.

Granted, 20-30k years isn’t a particularly thick slice of geological time, but I think the odds are good that future geologists/paleontologists/coal miners will stumble upon SOMETHING that might indicate an advanced civilization.

We’ve done this before. In these sorts of time frames you really are reduced to what gets fossilised, and that in turn depends on the physical and temporal extent of your civilisation. 50 million years ago forests covered large areas of the earth, but you don’t see vast amounts of evidence for such forests today despite their mass and vast extent. Only in some very tiny areas you can find fossils of forests from 50 million years ago.

People tend to think that there are fossils everywhere, and thus everywhere has fossils from 50 million years ago. That isn’t accurate. There are fossils in lots of places, but they come from all different ages. Trying to find fossils from a single ecosystems from a single period is literally the lifetimes work of many palaeontolgists. If you want to find fossils of the first flowering plants, for example, you might need need to find fossils of freshwater ecosystems from a period of 5 million years, starting 150 million years ago. And people literally spend their lives looking.

What we are discussing here is very similar. Rural areas just won’t fossilise. Even the most intensively worked farmland will be unrecognisable within a few thousand years at most. Someone in the earlier thread suggested we would get petrified cities like we get petrified forest, which is ridiculously improbable. Forests covered trillions of hectares for hundreds of millions of years, with large areas growing on swampy ground ideal for flooding an in situ fossilisation. An still we have a few of hectares of petrified forest in the whole world. Cities might have covered a few hundred thousand hectares for maybe a hundred millenia, with a few thousand hectares on suitable swamps and floodplains. The odds of an actual petrifeid city is basically nil. You really need to be looking for sediments where garbage from cities is being washed.

If there was a single regional civilisation, akin to Mespotamia 10, 000 years ago, and it lasted 100, 000 years, you would never find it. The odds of any evidence even being fossilised is staggeringly remote. The odds of the fossils lasting 50 million years is even more remote. The chances of the fossil bed being revealed by erosion are miniscule, and the odds of someone who knew what they were looking at finding the exact portion of the fossil bed that contains the incriminating fossils is about as close to zero as makes no difference.

If you had a truly world spanning civilisation as we have today you might have better odds. We are producing so much garbage now that we have probably left some evidence of our existence in most fossil beds. But the evidence is still dispersed. There might be one electric drill or equivalent in ever hundred square metres of ocean sediment. That’s still not a readily detectable signature but it might show up.

Then we come to the issue of attribution. We find odd fossils all the time today. We don’t attribute them to technology, we simply file them away as “unclassified” and they languish in museum drawers for decades. Occasionally someone knew has a stab at what they are. Even if someone did find a fossilised circuit board from this civilisation, it wouldn’t be attributed to technology unless it was clearly identical to their own technology, which is unlikely, as noted in that other thread. Instead it would be published with guesses about it being an odd mineral formation or the tunnel system of some burrowing worm and then it would be put in the museum drawer.

The same attribution problem applies to other evidence such as radioactivity, species distributions and similar. We already find areas of unusually high or low radioactivity, shocked quartz, odd species distributions and so forth. We invent rational explanations for them without ever invoking ancient civilisations.

To convince scientists that you had a real civilisation you need something that is clearly built by intelligence. That isn’t that easy to do. Most furniture could be ascribed to unknown organisms. Broken fragments of things like circuit boards the same. You really need an intact piece of complex equipment like a car or DVD player.

Unless a civilisation lasted along time over the whole world, I wouldn’t put money on finding any convincing evidence that it existed.

You won’t find metal or organics in even 100, 000 years time, never mind 100, 000, 000. Fossils are not the remains of the original material. They are minerals that have *replaced *the original material. They have the same shape, not the same chemistry. You are about as likely to get organics and metal out of a 50 million years old landfill as you are to get blood out of a 50 million year old fossil rat.

This is the attribution problem again. We find things like this occasionally, and we invent perfectly plausible explanations as to how they occurred naturally.

How often does the moon get hit by meteors?

This I think might be the best bet for both the hypothetical “long lost civilization” from the OP and for us as well, as signs for someone to look for if they’re searching back hundreds of thousands of years. Mines, stripe mines, open-cut mines. Enormous earthworks, basically: gigantic, hundreds of meters deep, multiple-kilometers across holes in the ground, in geologically stable areas. Sure, they would erode over the eons, but erosion can be measured: a future geologist could determine that, at the current rates of various types of erosion, a hole such as the Super Pit in Australia couldn’t be formed naturally.

Fossils of dinos (or whatever) with huge braincases compared to their body weight and hands suited for manipulation would be the first clue. The best bet for evidence such a being had technology would be if it left an imprint along with it – if you found an outline of a watch or gun or glasses or something. Fossils with imprints are rare, but it could happen.

If they were on our level we could find their spacecraft on the moon. Is it possible a satellite could remain in a stable orbit for that long? As long as a little pebble didn’t smack it, anyway.

Even if we went out of our way to make a time capsule in a geologically stable location it’d be pretty wild if it lasted 50 million years. That’s a loooong time. It could end up at the bottom of an ocean, in a glacier, in a volcano, or just plain buried under a mile of dirt. For all we know there’s evidence of a dinosaur civilization on Antarctica but it’s under 2 miles of ice.

Again, we end up with the attribution problem. So we know it couldn’t occur under normal natural conditions. The world is full of geological anomalies like that though. Everything from the Tunguska blast to Mima mounds to oriented lakes to the origins of dolomite and coal are just as mysterious and inexplicable as a big hole in the ground. We don’t invoke ancient civilisations to explain such things. We come up with a whole range of explanations, none of which ever get consensus approval amongst geologists.

In reality anomalous ancient holes in the ground would just be put in the same category. I can even see someone linking them to Tunguska-type blasts. We can be fairly certain that if a such a hole were discovered tomorrow, not one geologist would invoke it as evidence of ancient astronauts.

What is it, 90% of species never leave any fossil record? The odds of any species actually being fossillised at all is remote.

A species that burns and buries its dead has even less chance of leaving direct evidence. Even in places like east Asia and western Europe where people have been living in high densities for thousands of years it’s difficult to find human remains more than a few thousand years old. The odds of finding remains after 5 million years is considerably less.

Where does that come from? If they didn’t leave a fossil record, how do we know they existed?

Previous thread: [POST=8766489]Ancient advanced civilizations[/POST]

Geological evidence: even if they built concrete or stone buildings, we’d be hard pressed to find any identifibly remains after tens of millions of years, much less 140-200 MYrs. Wind, water, and plantlife tend to break down even the most hardy stone structures. They would almost certainly be buried under hundreds of meters of soil and rock, or scraped away by glaciers, depending upon where they were locations.

Fossil evidence: it’s possible. While sparse, we have skeletal fossils going back to the Neoproterozoic era. A civilization that flourished enough might have produced both species and persistent waste products that could be found in fossil record. However, that would be almost completely of line with what has been reconstructed of Jurassic species.


Two ways:

  1. If two closely related, endemic species of *Canis * appear in North America in the Eocene, then a third, common ancestor mist have existed prior to the Eocene. The fact that it never left any physical evidence doesn’t change the fact it must have existed, unless we posit that the two daughter species sprang out of the ground fully formed.

  2. We can do a comparison with similar, better preserved sites elsewhere. A 1 ha area of Jurassic swamp forest in France yields 1, 000 species of beetle. We know that there were also 6 million ha of such forest at the same latitude in South America at the same time. We can then use some basic species-area curves and safely assume that there were at least 100, 000 species of beetle in South America. We have fossils of just 2 of them, but unless something totally inexplicable was happening we know that there must have been hundreds of thousands, they just left no trace.

Uncultivated farmland would likely return to a natural state with a few hundred years. Save for the odd tractor with a thick cast bathtub frame rusting away in the center of a field (which would probably take a few thousand years to completely dissolve) there wouldn’t be anything to indicate agricultural development. Heck, if you go look at a plot left uncultivated for a few dozen years it’ll barely be distinguishable from untouched land. Fenceposts will have rotted away, barbwire will be buried or broken, and the only remaining indications of agriculture may be the curious lack of normal distribution of rocks in square patches of land.

Shades of A Canticle for Leibowitz, with monks spending decades illuminating circuit diagrams without having a clue as to what the drawing is for.


Many unknown species must have existed as intermediate species between known species. It’s part of the paradox in which children generally look like their parents, yet species still evolve such that descendants eventually no longer resemble their ancestors.

And if you throw in a period of glaciation, which occurs every few tens of thousands of years, you will scrape up the bedrock and all of the unconsolidated soil above it such that you will again have a normal distribution of rocks and boulders in the former fields, along with obliterating just about anything manmade.

If you throw in the type of continental landform changes that occur in the timeframes comparable to the time since the Jurassic (hundreds of millions of years), then you have enough time for plate tectonics to raise mountains and erode existing mountains to plains.

In wetter temperate regions, certainly. In more arid regions, or on the more fragile rainforest soils, you could almost certainly detect the signs of disturbance for much longer than that. Trees take much longer to colonise in drier environments, and the distribution patterns from fertiliser take longer to disperse. There are old sheep stations in Central Australia that were abandoned on the 20s and thirties, and there is only minimal alteration. Some fence posts have burned out, there are some shrubby bushes colonising the cleared areas, but it look like it’s going to take much more then 200 years to eradicate even the gross traces.

In the case of the rainforests the full cycle from colonisation to mature climax community would take a bare minimum of 500 years.

But I think that after 2, 000 years there would be no evidence at all that farmland existed.

Yes, and that’s a critical counterpoint to anyone who thinks traces of our mining or roadbuilding operations will be discernible in 150 million years. They won’t.

The only thing I can imagine that might give us away would be fossilized imprints (a la dinosaur tracks). You could theoretically have fossilized tire tracks, or the fossilized outline of anything, I suppose, that happened to be encased in fine silt. If silt can preserve the imprint of Archaeopteryx feathers, I suppose it could also preserve the imprint of, say, a motherboard or a Studebaker.

The problem is the narrow geological time frame. I think the odds against finding such a well-preserved fossil from a particular 20,000-year geological period would be awfully large.

A worldwide civilization might leave evidence in the form of a sudden mass extinction simultaneous with a mass transplantation of species into regions distant from their previous habitats. The latter would be particularly significant in cases that would be difficult to attribute to natural migration (rabbits in Australia, potatoes and tobacco in the Old World, etc) – barring that, it could probably be chalked up to a climate upheaval or something.