Was There a Civilization On Earth Before Humans? - The Atlantic
We’re used to imagining extinct civilizations in terms of the sunken statues and subterranean ruins. These kinds of artifacts of previous societies are fine if you’re only interested in timescales of a few thousands of years. But once you roll the clock back to tens of millions or hundreds of millions of years, things get more complicated.
When it comes to direct evidence of an industrial civilization—things like cities, factories, and roads—the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. It’s “just” 1.8 million years old—older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. Go back much farther than the Quaternary and everything has been turned over and crushed to dust.
I think that a lot of industrial artifacts would survive *much* better -- even many preindustrial ones.
Some might - but we would have very little chance of finding them.
Consider all the fossils of bones and shells and leaves.
Yes, consider them. Fossils are RARE. We know that they represent populations of huge numbers of organisms over tens or even hundreds of millions of years, and yet we find very few of them, in specific strata that just happened to form in ideal conditions to preserve them.
Anything organic that did not decompose, like wood and plastic and paint, would get carbonized.
We can barely detect the archaeological traces of the Anglo-Saxon period (approx 1000-1500 years ago) in Western Europe. These were master metalworkers, who made steel that was not equaled until the industrial revolution; But unlike the Romans before them, they didn't build much in stone or use much by way of pottery. So their artifacts (and in most places, even their skeletons) have practically vanished, in less than 0.1% of a mere million years.
Iron would rust, and leave big deposits of rust.
Which would be indistinguishable from other iron ores.
Aluminum might survive, since it makes a thin layer of aluminum oxide that protects it,
Sure, if it was made in large quantities. But it wasn't until well into the 20th Century that we could make large quantities of aluminium alloys that were durable and able to be used for structural purposes. And it decays into oxide very quickly if heated or crushed, so many geological processes would destroy it.
and gold and silver would certainly survive.
Gold, yes. Silver oxidizes pretty fast, and disappears in a few tens of thousands of years unless in very thick ingots. And gold is fairly rare, and very malleable - small gold artifacts in very small numbers might survive, but over tens of millions of years would not be easy to distinguish from natural nuggets - and gold's not really useful; If humans didn't choose it for jewelry, and then as a result as a medium of exchange, then we wouldn't see much of it at all archaeologically. There's no reason to expect any non-human civilization to bother with gold, for anything other than trace applications such as electrical contacts.
Ceramic and glass objects would likely survive very well.
For sure. But how much would remain in places accessible to our miners after tens of millions of years?
Concrete may be more vulnerable, but even if concrete objects disintegrate, their material will survive.
Sure. But not in any form we would recognize as obviously artificial.
The best-surviving objects would be those that get buried in sediment, like coastal cities and continental-shelf shipwrecks. Upland objects would likely suffer a lot of erosion.
Agreed. And the VAST majority of that stuff will have been subducted deep into the Earth, never to be seen again, after ten million years.
Returning to the article, the authors propose that the best evidence might be some bout of global warming that starts very fast. That would be from consumption of fossil fuels.
Fifty-six million years ago, Earth passed through the Paleocene-Eocene Thermal Maximum (PETM). During the PETM, the planet’s average temperature climbed as high as 15 degrees Fahrenheit above what we experience today. It was a world almost without ice, as typical summer temperatures at the poles reached close to a balmy 70 degrees Fahrenheit. Looking at the isotopic record from the PETM, scientists see both carbon and oxygen isotope ratios spiking in exactly the way we expect to see in the Anthropocene record. There are also other events like the PETM in the Earth’s history that show traces like our hypothetical Anthropocene signal. These include an event a few million years after the PETM dubbed the Eocene Layers of Mysterious Origin, and massive events in the Cretaceous that left the ocean without oxygen for many millennia (or even longer).
There were similar bouts of global warming in the Mesozoic and the Paleozoic (
Anoxic event), and these bouts are often associated with mass extinctions. The more recent ones had an interesting side effect. Their lack of oxygen meant that dead algae would accumulate on the ocean floors without getting decomposed, and these remains of algae became petroleum. So we owe our crude oil to past bouts of global warming.
Fossil fuels must be extracted, and their extraction ought to leave behind evidence. Evidence like long-gone coal mines.
If such a thing existed within reach of the surface by modern miners, how would we recognize it?
Also, the easier-to-extract fossil fuels must be gone. But we have had plenty of such fuels, and we have used up many of their easier deposits.
The stuff that's easy to extract today is not the same stuff that would have been easy to reach tens of millions of years ago.
So on our planet, it seems like we are the first.
Probably, but it's far from certain. Detecting such a thing would require a lot of luck. Tens of millions of years is enough time to move almost all of the evidence into the mantle, where it would be inaccessible even if not destroyed.
And a pre-human pre-industrial civilization, similar to our ancient Greece, Rome, or Egypt, would be even harder to detect.
Almost every response so far in this thread has apparently ignored the sentence I
bolded above in the OP article, and discussed the matter as though we are concerned with only a few million years at most.
Fossil remains of large Cretaceous fauna are very rare - and we can be sure that every fossil we have found represents millions of individuals living for tens, or hundreds, of millennia, only one of whom won the 'fossilization lottery' of being both preserved for over 60 million years, and exposed on or near the surface to curious humans. A small population of a few tens of millions of individuals worldwide, who developed an industrial society in (say) the Cretaceous, and whose civilization lasted only a few centuries before they killed themselves off, could easily have gone completely undetected.
