Whenever there is research showing that X thing occurred Y years before we previously thought, the big thing we should update on is our confidence intervals. This research pushes back our estimate of freshwater 500M years. What will the next research show?
We’ve had radiocarbon dating age New World artifacts at 20,000+ years, and one in South America up to 60,000 years, but these have all been one-off occurrences that have been mostly regarded as oddities. This study is certainly compelling on its own, but there are many more indications that humans were here well before the land bridge!
Which way would you update our confidence? A: We were so wrong earlier, but now we "know better", due to better measurements, better models and more evidence, so our confidence is higher. B: We have been so wrong in the past, so our confidence is lower.
not for me. I don't know much about the emergence of freshwater, but if I learn at some point that humans were in the Americas 50,000 years ago --- perhaps they used rudimentary rafts? -- I will not be shocked.
> If we find a tool site or cave painting, what does that have to do with genetic drift
They’re separate signals.
If radiometric dating of a cave painting says 10,000 years, that’s obviously evidence. But if drift says 20,000 years, that gives room for doubt. If drift says 12,000 years +/- 2, less so.
I'm confused by this. When I was blogging about life on Mars[1] I was using a date for the emergence of fresh water on Earth of 4.4 billion years ago(bya)[2]. But this article says the date has been pushed back from 3.5 bya to 4.0 bya.
But reading carefully, it looks like by "fresh water" they means water on land aka rain, not just the existence of seas.
I also have a hard time understanding how they differentiate between salt water and fresh water so long ago. It seems like the salinity of the oceans has changed over time. The first seas might have been quite fresh as compared to the ocean today (or even more salty).
It's just that I have a hard time imagining that there were seas without any rain occurring for hundreds of millions of years so it didn't occur to me that these could be separate questions. And most of the comments here seem to be conflating them as well.
“If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today” [1]?
TL; DR Difficult after ~2.5 million years unless they had a nuclear war.
As for humans: “some specific tracers that would be unique” include “persistent synthetic molecules, plastics and (potentially) very long-lived radioactive fallout in the event of nuclear catastrophe. Absent those markers, the uniqueness of the [Anthropocene] may well be seen in the multitude of relatively independent fingerprints as opposed to a coherent set of changes associated with a single geophysical cause.”
Bonus: “…should any of the initial releases of light carbon described above indeed be related to a prior industrial civilization…these releases often triggered episodes of ocean anoxia (via increased nutrient supply) causing a massive burial of organic matter, which eventually became source strata for further fossil fuels. Thus, the prior industrial activity would have actually given rise to the potential for future industry via their own demise. Large-scale anoxia, in effect, might provide a self-limiting but self-perpetuating feedback of industry on the planet.”
So if we’re going out, we should go all the way and suffocate the oceans out of courtesy.
I think people underestimate how long ancient artifacts can survive. For instance searching for pot shards and arrowheads from the local Pueblo people I was lucky enough to find an arrowhead in excellent shape still attached to a fragment of shaft. This find is evidence not only that such things can survive, but that Pueblo people had advanced technology in the fabrication of aluminum and fiberglass.
> find is evidence not only that such things can survive
You’re citing artefacts on the order of centuries to millennia. This is off by many orders of magnitudes from the paper’s subject. Arrowheads would not be expected to survive millions of years, thousands of times longer than they have to date. (EDIT: Obviously wrong.)
We've got stone tools from 2-3 millions years ago. Arrowheads just weren't made back then, only much more primitive oldowan choppers and then acheulean handaxes.
> We've got stone tools from 2-3 millions years ago
You’re right. 3.3mm [1]. Not evidence of “industrial civilisation,” though. And within the few million year guess the paper posited.
Those tools would have to be lucky to survive 10mm years. (The Earth is tearing itself apart not far from the site [2].) Our factories and cars would need more than luck.
Sitting in dry sediments they'd keep being OK until geological processes catch up to them. They're literally rocks.
If something does not degrade biologically/chemically and is shielded from the elements it's going to take a long time to make it unrecognizable. We find biological fossils all the time. And they're old.
Sure. I’m struggling to think of a rock we produce that would evidence industrial processes.
Put another way, if we found this rock in an old stratum, tens or hundreds of millions of years old, would it be proof someone with industry was there?
Very interesting. It's difficult to get hard numbers. It depends a lot on the composition and the temperature, so I'm more optimistic about they lasting for a few millons years at burried at 15°C(60°F), but I agree they don't last forever
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>> asphalt of the roads may dissapear, but the gravel mixed with it and under it will create a very strange pattern
> Would this be recognisable at an industrial scale?
I guess so. We have a lot of roads with a not random patterns.
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>> Panama and Suez channels
> Suez is right above the East African rift, so maybe 10 My. Panama no clue.
I agree. Both are in bad positions to last forever.
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>> Quarries and coal mines are huge
> To where they could evidence industrial activity after millions of years?
I guess they are. Look at this video https://www.youtube.com/watch?v=fjp6RHb7MtE the truck are huge, from time to time there appears a normal truck next to them and it looks like a toy truck. I think when abandonded they get filled with water, then with mud and decomposing plants, and then that will solidify and in the future they will have a huge "volvano caldera" but no volcano at the bottom. Also find the internal roads, cuts by explossions and other strange characterisitcs. The truck will have rot a long time ago and dissapeared, but they may find unusual levels of iron contamination in the parking lot.
Concrete is laid on recognizable shapes that would never be present in nature - and while it would lose strength and degrade in time, the underlying minerals would still be present and clearly recognizable.
Same with steel, stainless steel, brass, ceramics (of all types), glass, plastic, etc.
Hell, just all the roadside glass bottles over the years will leave one difficult to ignore trail.
While I agree with most points: steel degrades quickly. Iron-age swords found are in a bad shape already (bronze age swords preserve better!). Stainless is better, but not that better.
And iron oxide girder shapes are going to be pretty hard to blame on something else eh?
Iron oxide is super stable.
Chromium oxide too.
I’m not saying they’ll not oxidize, I’m saying they’ll still form very recognizable, unnatural, and stable shapes when they do. Even a fully oxidized iron sword leaves a sword shaped lump where it is.
And that isn’t something that occurs very often in nature.
I'm not sure how concrete fares with time, but we're making a lot of it. If buried asphalt roads might present a decent head-scratcher. And if not weathered rock carvings should be noticable for a long time.
I think you might not fully grasp what happens on the scale of millions or billions of years. The entire crust folds in over itself repeatedly and everything (probabilistically) ends up boiled down into magma deep within the earth as new crust emerges to take its place. Nothing static survives.
“…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.
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.
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.
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.
> 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 humans and apes easily survive for millions of years.
The Keweenaw copper deposits [1] where copper is mined in boules and nuggets far larger than 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.
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.
I think the completely isolated eco systems in places a fairly short boat ride away shows there hasn't been an advanced civilization for some double digit number of millions of years.
How much of a nuclear war? We already had a tiny one, a few surface tests, and significant underground tests. I know the surfaces tests put enough stuff into the atmosphere that radio-nucleotide changes were found in boomer infant's teeth which led to Kennedy's interest in banning the practice. But I wonder how detectable that period will be in future.
We need to exceed the AMS measurement error of 370 atoms of 244Pu per gram of the rare-earth mineral bastnäsite [1]. Let’s assume this works for 0.2 cubic centimeters of anything [2].
We have about 20 grams of the stuff straight up [3]. Sprinkling those 4.9 x 10^23 atoms around at 18.5mm atoms / m3 we get 26 quadrillion cubic meters of irradiated surface material. Spread over Earths surface of 510mm square kilometers [4] and we get a 51 meter-thick slab of detectably-irradiated soil. Yay! (Let’s double to give us 80 million years of signal at 371 atoms per square centimeter: 26 meters.)
Unfortunately—perhaps unsurprisingly—I’m having trouble finding the 244Pu yield from a thermonuclear blast.
[1] Not Found. Which motivated me to let leGPT write a bash script to increment the URL and send requests in batch until it reaches 10k and returns all non 404 URLs if it finds any. still running, internets and hardware are slow or the curl command is.
EDIT: huh, should have known what was going to happen -.-'
> thought radiometric dating and low-background steel "prove" there were no nuclear detonations prior to WW2?
“Many radioactive isotopes that are related to anthropogenic fission or nuclear arms, have half-lives that are long, but not long enough to be relevant here. However, there are two isotopes that are potentially long-lived enough. Specifically, Plutonium-244 (half-life 80.8 million years) and Curium-247 (half-life 15 million years) would be detectable for a large fraction of the relevant time period if they were deposited in sufficient quantities, say, as a result of a nuclear weapon exchange. There are no known natural sources of 244Pu outside of supernovae” [1].
Attempts have been made to detect primordial 244Pu on Earth with mixed success (Hoffman et al., Reference Hoffman1971; Lachner et al., Reference Lachner2012), indicating the rate of actinide meteorite accretion is small enough (Wallner et al., Reference Wallner2015) for this to be a valid marker in the event of a sufficiently large nuclear exchange. Similarly, 247Cm is present in nuclear fuel waste and as a consequence of a nuclear explosion.”
TL; DR Absent nuclear war, we wouldn’t be able to find evidence of a past nuclear civilisation after a few million years. Even by way of radiometric dating. (Low-background steel deals with atmospheric radiation. That isn’t relevant on sub-geological time scales.)
Iodine-129 has a half life of 15 million years, and would be essentially impossible to confine for that long. In excess of 1% of thermal fissions of U-235 (and 2% of Pu-239) produce this isotope.
(BTW, if I understand correctly this probably isn't an argument against nuclear energy, since if you replaced every iodine atom in your body with this isotope you'd still probably be within safe limits for radiation exposure, and more so if our descendants evolved to tolerate it as it gradually accumulated in the environment over millions of years.)
That says anthropogenic (the uneven distribution in seawater shows a recent source). But it does show how highly detectable the isotope is, that it shows up even after just a few decades of use of fission. A putative pre-human civilization could have been pumping it out for much longer.
Sorry, wrong link from the rabbit hole. Iodine-129 is “naturally produced in small quantities” [1].
The paper restricted itself to transuranic radioisotopes, but it’s unclear why. The operant question would be, if we found 129I on Mars, would that be evidence of technological civilisation?
It’s great to find somehow who knows about some of these unorthodox ideas and can also explain them well technically. Have you ever assembled information on this topic into a reddit post somewhere? I think you should.
Basically you are aware of the Silurian hypothesis and also the lost Mars civilization hypothesis. I’m guessing you also know of the recent cryptoterrestrial hypothesis [1] and how that might relate.
These are all admittedly fringe ideas but they have way more evidence and merit to them than people realize. reddit is a more appropriate place than HN to discuss these ideas because of the very speculative nature.
To rephrase your comments today are excellent contributions to such a discussion and if you haven’t already considered collecting them together and post on your favorite fridge sub and please let me know.
> admittedly fringe ideas but they have way more evidence and merit to them than people realize
To be clear, I don’t buy these hypotheses. But they force us to ask questions that show the limits of our technology. If Mars had water 4 billion years ago, and an alien civilisation existed, my naïve guess is we’d find buried evidence of it. Weathering happens differently on Mars. But to know the answer is maybe not puts boundaries on what we can conclude from the data we find there, as well as our interpretation of our Fermi paradox observations.
I think you probably do subconsciously but you don’t want to admit it as they carry stigma which your background and training probably insists you avoid.
Im regards to Mars we have very little idea what is going on there. There is serious paper proposing fungi like life has already been observed but we haven’t recognized it. My understanding is a significant number of serious astro biologists think it’s likely there is currently life on Mars.
I’m definitely unaware of any archeological digs on Mars.
Since we are on the fringe topics I’ll mention that another related thought experiment is assume an advanced earlier Mars or Earth civilization moved to the Saturn system and currently resides there leveraging its abundant resources. Would we have actually detected it already?
Back of the envelope I estimate if the world economy were fission powered the rate of I-129 production would be six orders of magnitude higher than the natural rate. The power from U-238 spontaneous fission in the entire earth is maybe 20 MW.
> TL; DR Difficult after ~2.5 million years unless they had a nuclear war
Scary if they didn't!
EDIT: what else killed them off or where did they go and will they come back, so it's actually quite curious and less scary but it made me shiver when I read it the first time.
I think much of the sea is there because of massive nuclear war millions of years ago which created enormous craters that the water just seeped into and filled up.
I mean, I never thought of it prior to today. But why not.
Personally, I’m of the ‘shits whack yo’ school of geohistorical projections. So got me. I’m still pondering what weird confluence of events could cause Salt Domes combined with massive oil and natural gas deposits like in the Gulf of Mexico.
Chicxulub?
Something else?
One thing is for sure, the more you understand and analyze the geological record, the more the doomsday preppers seem like insane optimists!
That's still not really a hypothesis that connects to TFA as we're still basically proposing "well, the water just flowed down from higher up!" Put it this way, Snowball Earth is not itself a hypothesis for where'd the snow come from to make the snowball.
Also doomsday preppers live on the scale of a human lifetime -- you do agree that geological events don't really factor in?
If earth were a smooth sphere, the water would be about 2500m deep.
You can't get that amount of water from lakes, rivers and puddles.
If you want to less of earth by water (than the oceans cover today), you need those parts to be covered in deeper water (on average) than the oceans are today.
The margin of error seems to be +/- 500M years on these things. In no other area of "science" has there been such widely innacurate predictions and hypotheses that we are still changing things by millions of years after all this time.
It does not sound like a wide margin to me. 3,500M or 4,000M are kind of close targets, when you consider that the Earth has been a continually changing system (unlike a rock such as the moon). Pretty hard to construct a timeline accounting for all the changes that might have lead any one of your supporting conclusions down the wrong path.
When you revise one of your conclusions, you have to revise all the conclusions it supported, and it might turn out that one of your numeric estimates was 500M off. Easy.
Astronomy by contrast is much more regular, so then a 500M year difference can indeed be a big deal.
This is confidently incorrect. If you're making observations of very short-lived processes your margin of error will be in micro-, nano-, atto-seconds etc.
If you're looking at processes that take billions of years, naturally the margin will be wider, especially that it's very hard to make accurate observations about stuff that took place a very long time ago. It's not that hard to grasp.
This comment is a perfect reminder of how humans have a really rough time telling large numbers apart and don't have an intuition for orders of magnitude at these scales.
It’s analogous to finding evidence that humans were in North America 10,000 years before we previously thought, but there is no way we should treat that as a lower bound: https://news.berkeley.edu/2023/10/05/tests-confirm-humans-tr...