> Was There a Civilization on Earth Before Humans? [...] Gavin and I don’t believe the Earth once hosted a 50-million-year-old Paleocene civilization.

Betteridge's Law confirmed. We can track down fossils billions of year back by observing the way they shaped the encasing rocks, and not once have we noticed a ceramic shard, a metal bit or the silhouette of a plastic object.

From the article:

> There are fossils, of course. But the fraction of life that gets fossilized is always minuscule and varies a lot depending on time and habitat. It would be easy, therefore, to miss an industrial civilization that lasted only 100,000 years—which would be 500 times longer than our industrial civilization has made it so far.

> And then there’s all that plastic. Studies have shown that increasing amounts of plastic “marine litter” are being deposited on the seafloor everywhere from coastal areas to deep basins, and even in the Arctic. Wind, sun, and waves grind down large-scale plastic artifacts, leaving the seas full of microscopic plastic particles that will eventually rain down on the ocean floor, creating a layer that could persist for geological timescales.

Sandstones. Sandstones originate as far as hundreds of million years in the past. Occasionally they harbor fossils, which are indeed rare. But a lot of sandstone is made of sanded up organic material which we can readily identify, even if we can't point to the specific organism they originated from. We only need a tiny industrial-related grain of sand (ceramic, glass, metal, plastic traces) to point to a past civilization. Nobody ever noticed such a grain of sand.

Sure, and the article mentions other possible signs of civilization as well, then it goes on to say:

> So it might take both dedicated and novel detection methods to find evidence of a truly short-lived event in ancient sediments. In other words, if you’re not explicitly looking for it, you might not see it. That recognition was, perhaps, the most concrete conclusion of our study.

I'm not bullish on pre-historic civilization, and neither is the article, but the takeaway is we may not have reason to expect that we'd have found these tiny industrialized traces without a search aimed specifically at them. As far as I know, such searches have not been carried out in earnest to date.

We've put old rocks under the electronic microscope. That's how we identified billion year old cyanobacteria fossils. While there is no readily available comprehensive record of who searched for microfossils by looking at what old rocks, with or without a microscope, it's not like it's a new idea.

https://ucmp.berkeley.edu/bacteria/cyanofr.html

I feel like we're talking past each other here. The very first sentence of your link says "The cyanobacteria have an extensive fossil record." In the next paragraph it says "Cyanobacteria are among the easiest microfossils to recognize. Morphologies in the group have remained much the same for billions of years..."

So not a truly short-lived event in ancient sediments then.

They we would not have access to petroleum, so no plastic.