If you entertain the notion that 55M years ago the PETM was caused by the Silurian civilization then geologically you have to realize that it was only 40M years ago that the Indian plate slammed into the Eurasian plate and caused the uplift of the Himalayas. Mt Everest just didn't exist at all back then. And shield glaciers have carved the continents on a 100k year cycle for at least the past 1M years which would have destroyed all of the surface mining evidence at northern latitudes. A lot changes geologically over those kinds of time periods.

Of course most of our oil reserves come from the Mesozoic age (66-252 million years ago) so either the Silurians quickly transitioned away from fossil fuels, or blew themselves up and went extinct before they could extract all of it.

There could have been a much larger amount of fossil fuels in the ground that was almost used up by the Silurians and now we believe what they left us with is all there ever was.

This makes me wonder: which methods of resource extraction lead to the complete destruction of evidence that resource existed, and which methods lead to a preservation of evidence? If you insert a deep well into a fossil water aquifer, and only use 10% of it, will it all have evaporated after 5 million years due to exposure to the elements?

Over the timescales we’re talking about, most all of the evidence would be shredded, compacted, oxidized/metamorphized then the above, filled with sediment then the above, etc.

One example of those - Intact fossils are very rare, and life has been ever present on the surface of the planet a billion+ years, near as we can tell.

That said, unless they weren’t around for long or didn’t have much success/impact, some difficult to dismiss evidence would likely to be present somewhere we ran across already - like fossils. Even if 99.99999% of all our evidence gets subducted, anyone doing as much digging 50 million years from now as we’ve done recently would have a hard time missing all of traces we’ve left.

A really weird set of isotopes and geological features (like in Oklo, but not explainable naturally) from something like the National Test Site, or a layer of something like lead or mercury or radioisotopes in the sediment record not explainable by other means (like we’ve left), or a landfill full of plastic+stainless steel+carbon since metamorphized, or weird geological features like road fragments with no plausible natural explanation.

So unlikely, but not impossible. We are talking lengths of time 1000x (approx.) the furthest back of our own artifacts we’ve found.

No, they are mere surface scratches on the timescale of geologic activity.

Considering how much tiny fossils we have, those scratchrs as you call them are huge and we would have them by now.

But then we often have nothing for millions of generations and absurdly large amounts of biomass for species that we know well enough to know where to dig – but nothing was preserved there, and we can't dig in more than a few tiny spots. The crust's top layers are an immensely big volume and very hard to penetrate and not sure there would be a reason to dig right into an oil well that was emptied millions of years ago. Also, there is a strong aversion to sensationalist explantations in the sciences, so such scratches might even be known but attributed to some ill-understood kind of volcanic activity or earthquake scarring just because speculation towards a Silurian civilization isn't conducive to swift career progression.

Among the stuff we can use to proof the hypthesis of such a civilization (from skimming the linked paper):

- evolutionary evidence pointing at the possibility of species with large enough brains to build industrial civilizations

- sedimentary proof of artificial pollution and CO2 levels

- fossils

Any hypothesis has to be proven to be true, proofing it to be wrong is impossible and not things work. What the cambrisge paper did, was pointing towards wayw to proof the existence of an ibdustrial civilization millions of years ago. Now the work is on the people believing that theory to proof it.

Speculating without considering the basic principles behind said claim, concluding it is impossible to proof that theory wrong and finishing all that off with a the claim that such a civilization most definetly did or could have existed is just stupid. It worries me so, that this kind of shit shows up on HN more and more often.

> proofing it to be wrong is impossible and not things work.

That's pretty much entirely how science works ever since Karl Popper: You find an observation that the hypothesis cannot predict or predicts wrong. Bam, hypothesis falsified and rejected, no matter how much positive proof was uncovered until that point.

We have a different view when it comes to the hypothesis then: the hypothesis is that there was no pre-historic idustrial civilization, proof that hypothesis wrong. The paper we discuss gives hints on how to proof that non-existence hypothesis wrong, or, in my ill choosesn words, proof the existence of said civilaztion.

Or, if you like, find and show proof making the existence of such a civilaztion likely. And no, the burden of proof is not on the side diaputing the claim of such an civilization, as only the existence of something can be proven, not the absence. Hence the very exact formulation of any null-hypothesis.

Coming back to some pre-dinosaur industrial civilization (why stop at industrial so, why not an instellar one?): there is a ton of data and samples from that time periods (litterally reaching back hundreda of million of years), so everyone trying to find evidence for such a very bald claim has a lot of data to work with. Just putting out the claim and saying it must be true brcause nody can proof it wrong is not how things work, in reality that is, on the internet everything goes apparantly.