[gorgoiler]

The counter argument: dinosaurs were around for a staggering amount of time, no pun intended. 165 million years is reasonably long enough to ensure they left behind some nests, bones, and a feather or two. Modern humans have been around for more like 0.02 million years.

The counter-counter argument is that while we’ve been here for a comparative blink of an eye, we’ve left behind 4 orders of magnitude more stuff than just nests, bones, and a feather or two.

[throw310822]

Indeed. Did a rapid check on T-rex, just as an example. Was around for max 3.6 million years. Max population at any one time must have been around 20k individuals. We have about 150 skeletons.

So current human population is 400 thousand times the maximum T-rex population at any one time. A few decades are enough to produce more human individuals than the entire T-rexes history. We also have the ability to go (and die) pretty much anywhere, so there will be human skeletons in every crevice, depth and environment on Earth. We also produce an absolutely staggering amount of artifacts of all kinds, from plastic straws to giant tunnels and artificial caves. There are zero chances an advanced civilisation on Earth won't be aware of us in 400 million years.

[T-A]

>We also produce an absolutely staggering amount of artifacts of all kinds, from plastic straws to giant tunnels and artificial caves.

Plastic will be gone in ~1000 years,

https://www.activesustainability.com/environment/waste-plane...

tunnels and artificial caves in a few million years at most as they are compressed by the weight of the rocks above them ("tunnel squeezing").

[throw310822]

How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?)

And how long does it take to dissolve skin? Footprints? Because we have those from hundreds of millions of years ago.

[T-A]

> How long to dissolve carved stone sculptures (in sizes ranging from 1cm to 100m?)

A quick search on "rock weathering depth per century" suggests a "typical range" of 0.05 mm to 6 mm, depending on rock type and environmental factors. At 0.05 mm, a stone object with radius 0.5 cm would crumble in 10000 years. With radius 50 m, it would take 100 million years.

I would expect them to be unrecognizable long before that though.

> And how long does it take to dissolve skin? Footprints? Because we have those from hundreds of millions of years ago.

What do those findings tell you about the cognitive abilities and social organization of the creatures who left them behind?

[throw310822]

> A quick search on "rock weathering depth per century"

That's a great illustration of what I meant. Of course an exposed rock consumes away in the space of a few millennia- this is exactly where the "Silurian theory" comes from. Yet it's also obvious that we have plenty of perfectly conserved rocks that are intact after hundreds of millions of years- i.e. fossils. Any small sculpture buried in clay can survive for an eternity.

> What do those findings tell you about the cognitive abilities and social organization

Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots? Drawings "I LOVE YOU" in the sand? The shape of a coca-cola bottle buried in solidified clay? Come on...

[T-A]

> Any small sculpture buried in clay can survive for an eternity.

If it's made of granite, maybe. But how many granite sculptures have you seen? Sculptors tend to prefer prettier and more easily shaped materials, like marble and limestone. Those happen to be mostly calcium carbonate, just like bones and teeth, so section 1.2 in [1] (chemical dissolution in acidic environments) applies, along with section 1.3 and [2] (mechanical fracturing and dispersion during wetting-drying cycles).

Even if your sculpture was buried in a maximally favorable environment, it would not have stayed that way over tens of millions of years. 50 million years ago, the Himalayas were just starting to rise as India crashed into Eurasia, Australia was waving goodbye to a forest-covered Antarctica while the Americas, North and South, had yet to link up. At a rate of one ice age every 100k years, 500 ice ages separate us from those days. One is enough to raze half a continent and turn a muddy seabed into granite.

> Skin? Like, with clothes on, or the shape of clothes? And shoes and hiking gear? Footprints with the shape of boots?

This is extremely anthropocentric. A hypothetical "Silurian" civilization would obviously not have been human, and may have had no need for such things. Would bears endowed with human-level intelligence want to wear clothes and boots?

> Drawings "I LOVE YOU" in the sand?

Have any such preserved drawings in the sand been found from the ~200k years humans have been around?

> The shape of a coca-cola bottle buried in solidified clay?

See section 1.3 in [1], and remember that the time scale discussed in that kind of paper is a few thousand years, not tens of millions.

[1] https://www.sciencedirect.com/science/article/pii/S004896971...

[2] https://www.tandfonline.com/doi/abs/10.1179/0197136978063731...

[nwah1]

Yea, but if humans went extinct tomorrow, very little human artifacts would remain after millions of years. Indeed, most would be gone well before that. How much stuff from the 18th century still remains, in percentage terms?

[bensyverson]

Unless it was burned, melted, decomposed or crushed to dust, it's all out there or in a landfill somewhere.

I do find it difficult to believe that we would not leave enough fossil and mineral evidence for future paleontologists to find. I get that the surface will churn, but layers of rock routinely become exposed, revealing the geological history of the area. No tea cup shards, no impressions of rusted cars in the mud, no concentration of metal in strangely rectilinear formations that suggests skyscrapers?

[neaden]

There would still be many signs. Dug up mines, metal alloys that don't exist in nature along with refined metals in quantities they don't exist, animal and plant species we bred along with all the ones we made extinct.

[nkrisc]

Very few things would in fact remain, you’re correct. But we’ve also created radioactive elements with half lives of many millions of years.

While there would probably very little direct evidence of humans after millions of years, there would probably be at least some anomalous evidence someone could find.