> we find fossils of dinosaurs all the time

“…for all the dinosaurs that ever lived, there are only a few thousand near-complete specimens, or equivalently only a handful of individual animals across thousands of taxa per 100,000 years. Given the rate of new discovery of taxa of this age, it is clear that species as short-lived as Homo sapiens (so far) might not be represented in the existing fossil record at all” [1].

> Wouldn’t tools and stuff also end up in the geological record

Corrode, break down, subsume into the mantle, et cetera.

[1] https://www.cambridge.org/core/journals/international-journa...

I think that oversells just how rare fossils are. Complete skeletons are rare but the regions that are known for producing fossils are extremely productive, for lack of a better word.

If you’re in California, you can go to Sharktooth Hill in Bakersfield to understand what that means. Million year old Megalodon teeth are plentiful and a few days digging is all but guaranteed to find several of them, among many other bones. The hard part is identifying the geological formations and excavating them while preserving context, which is impossible when its open to the public for digging. Once we’ve found the formations, it takes decades and decades because of a lack of funding and manpower (especially to assemble and research them).

Complete skeletons are especially rare because we haven’t had the technology to reassemble bone correctly until recently with surface proteomic analysis.

Dinosaurs have also been around orders of magnitude longer than humans. Behaviourally modern humans have been around for 50k years, while Dinosaurs were dominant on this planet from the T-J to C-P extinction events, so approximately 140 million years. That's three orders of magnitude. Also, even though nowadays 95% of mammalian biomass is either humans or exists to serve human needs, we still will need a long period to catch up to the legacy of the dinosaurs.

> the regions that are known for producing fossils are extremely productive, for lack of a better word

Source that might quantify that in terms of frequency?

> you can go to Sharktooth Hill in Bakersfield

Or Scott’s Valley or Capitola. There are a lot. Now consider how many clams or trilobites existed across those hundreds of millions of years.

Pushing back because I’ve never seen this prong of their hypothesis contested.

Keep in mind that most oceanic crust formed less than 200 Mya [1]. (Continents are better, clocking in at Ga timescales [2].)

[1] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... Figure 1

[2] http://www.lithosphere.info/papers/2006-Tecto-Art-TC1-small.... Table 1

I don’t know of any studies of the scale but there are millions of bones and fragments in museum storage that will never see the light of day because there’s no one to study them, and that’s just the bones people bothered to collect and save.

Obviously thats out of trillions of animals and only a tiny fraction of animals get fossilized and plenty of species never left a record, but at the human scale, we have so many freaking fossils we have no idea what to do with them. We bring our kids out on field trips to dig for them and leave with dozens of bones per kid that are at least hundreds of thousands of year old, because no one bothers if they're <10My old otherwise.

I’m not arguing that the fossil record is any more than a minuscule sliver of all animals that have ever lived, but there are still a lot of them and there’s no doubt human civilization is leaving its own behind that will be detectable millions of years from now.

> we have so many freaking fossils

Does that challenge that we only have fossils for “only a handful of individual animals across thousands of taxa per 100,000 years”?

Less than 0.1% of species wind up in the fossil record [1]. (I’ve heard but can’t reliably source 5% for animals.)

Most of those species existed far longer than we have. Hence why the astrophysicists who came up with the hypothesis ruled out fossils, much less fossils that would show evidence of industrial civilisation.

> no doubt human civilization is leaving its own behind that will be detectable millions of years from now

Sure, 2+ million, per the paper that sparked this.

[1] https://www.bbc.com/future/article/20180215-how-does-fossili...

We have littered the entire planet with stuff, some of it virtually indestructible, like the silicon chips in our digital dust, like mobile phones.

> like the silicon chips in our digital dust, like mobile phones

Rigorously work out how long each of those components would last under even ideal natural circumstances. Silicon doesn't devitrify like glass. But it will weather away, atomically, chemically and physically.

Megalodons are estimated to have gone extinct over 3 million years ago so that's the floor for how long bone can survive in significant numbers. They were huge carnivores so even though they constantly grew new teeth, the population was never that large to begin with compared to the billions of humans alive now, all leaving their durable refuse in a single contiguous layer.

They may have been around for 1000x longer than humans but the billions and billions of tons of gold, copper, and other native metals will be obvious non-degradable remnants that will survive us for hundreds of millions of years. Any metal that can be found in its native form will survive for a very, very long time and the list of such metals is long. We already know that stone tools from archaic human and apes easily survives for millions of years.

The Keweenaw copper deposits [1] where copper is mined in boules and nuggets far larger a strand of copper wire is about a billion years old. That's how long our bulk metal artifacts will survive, despite rigorous geological activity. Those artifacts already number in the hundreds of billions if not trillions. The only reason they don't already litter the planet like ancient pottery and arrow heads is that they're highly recyclable and reusable.

> But I expected HN’s responses to be a touch more thought through.

We've just been talking past each other which is par for the course for HN.

[1] https://en.wikipedia.org/wiki/Copper_mining_in_Michigan