8 ms·

Fresh water on Earth emerged 500M years earlier than previously thought

69 points by geox 2y ago

JumpCrisscross 2y ago
Silurian hypothesis! “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. [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...
- vasco 2y ago
  > TL; DR Difficult after ~2.5 million years unless they had a nuclear war. I thought radiometric dating and low-background steel "prove" there were no nuclear detonations prior to WW2?
  - JumpCrisscross 2y ago
    > 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.) [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...
    - pfdietz 2y ago
      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.)
      - JumpCrisscross 2y ago
        > Iodine-129 has a half life of 15 million years, and would be essentially impossible to confine for that long Seems to be running wild already [1]. Unclear if, due to it being naturally occurring, that would be a definitive signal. [1] https://pubmed.ncbi.nlm.nih.gov/15556197/ https://pubmed.ncbi.nlm.nih.gov/15556197/
  - deleted 2y ago
    [deleted]
- silverquiet 2y ago
  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.
  - JumpCrisscross 2y ago
    > How much of a nuclear war? 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] https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.0158 https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.01... [2] https://www.mindat.org/min-560.html https://www.mindat.org/min-560.html [3] https://www.osti.gov/biblio/1024694 https://www.osti.gov/biblio/1024694 [4] https://en.m.wikipedia.org/wiki/Earth https://en.m.wikipedia.org/wiki/Earth
    - sumsome 2y ago
      [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 -.-'
      - JumpCrisscross 2y ago
        [1] should be https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.015801 https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.01...
- actionfromafar 2y ago
  But we find fossils of dinosaurs all the time. Wouldn’t tools and stuff also end up in the geological record.
  - JumpCrisscross 2y ago
    > 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-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...
    - throwup238 2y ago
      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.
      - JumpCrisscross 2y ago
        > 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/10.1029/2007GC001743 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... Figure 1 [2] http://www.lithosphere.info/papers/2006-Tecto-Art-TC1-small.pdf http://www.lithosphere.info/papers/2006-Tecto-Art-TC1-small.... Table 1
- sumsome 2y ago
  > 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.
  - lazide 2y ago
    Eh, plagues or evolutionary ‘black holes’ followed by an outside context problem are all possible too. Aka Dodo bird type situation.
- delichon 2y ago
  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.
  - JumpCrisscross 2y ago
    > 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.)
    - IsTom 2y ago
      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.
      - JumpCrisscross 2y ago
        > 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. [1] https://www.smithsonianmag.com/science-nature/oldest-known-stone-tools-unearthed-kenya-180955341/ https://www.smithsonianmag.com/science-nature/oldest-known-s... [2] https://www.sciencealert.com/there-s-mounting-evidence-the-continent-of-africa-is-splitting-in-two https://www.sciencealert.com/there-s-mounting-evidence-the-c...
        IsTom 2y ago
        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.
- BurningFrog 2y ago
  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.
dansafee 2y ago
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.
- medstrom 2y ago
  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.
- vikramkr 2y ago
  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. 500 million/4 billion is only about 12%.
- bitcharmer 2y ago
  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.
- eru 2y ago
  Astronomy can have even wider absolute error margins for dates. Especially for dates that are in the future.
MacrohardDoors 2y ago
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.
- medstrom 2y ago
  Joke? Or where'd the water have come from?
  - MacrohardDoors 2y ago
    Vast lakes, smaller rivers, puddles, you know?
    - JumpCrisscross 2y ago
      > Vast lakes, smaller rivers, puddles, you know? The same volume of water was just…higher?
      - lazide 2y ago
        Notably, that is how melting glaciers raise sea levels.
        medstrom 2y ago
        So where'd the original glacier ice come from? :-) Earth has 1.386 billion cubic km (333 million cubic miles) of water. Lot of glaciers, that.
        lazide 2y ago
        Not proposing it ever actually happened, but one hypothesis [https://en.m.wikipedia.org/wiki/Snowball_Earth https://en.m.wikipedia.org/wiki/Snowball_Earth]. 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!
deleted 2y ago
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setgree 2y ago
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? 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-tramped-around-north-america-more-than-20-000-years-ago/ https://news.berkeley.edu/2023/10/05/tests-confirm-humans-tr...
- JumpCrisscross 2y ago
  > 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 Can’t we use genetic drift to bound those estimates?
  - davidmurdoch 2y ago
    What's your confidence interval for genetic drift?
  - sethammons 2y ago
    If we find a tool site or cave painting, what does that have to do with genetic drift?
    - JumpCrisscross 2y ago
      > 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.
  - Symmetry 2y ago
    If there's a subsequent population replacement the estimate will thrown completely off. Edit: And to be clear, not all population replacement is violent. The Norse in Greeneland were gone when the Inuit showed up for instance.
defrost 2y ago
[flagged]
- deleted 2y ago
  [deleted]
Symmetry 2y ago
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. [1]https://hopefullyintersting.blogspot.com/2019/04/how-likely-is-it-that-there-was-life-on.html https://hopefullyintersting.blogspot.com/2019/04/how-likely-... [2]https://en.wikipedia.org/wiki/History_of_Earth https://en.wikipedia.org/wiki/History_of_Earth
- OJFord 2y ago
  'Fresh water' always means as opposed to salt/sea water. 'Fresh water fishing', etc. (I'm not sure where you draw the line in rivers though)
  - Symmetry 2y ago
    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.
  - didgetmaster 2y ago
    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).

69 points by geox 2y ago

Silurian hypothesis! “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. [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...

vasco 2y ago
> TL; DR Difficult after ~2.5 million years unless they had a nuclear war. I thought radiometric dating and low-background steel "prove" there were no nuclear detonations prior to WW2?
- JumpCrisscross 2y ago
  > 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.) [1] https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...
  - pfdietz 2y ago
    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.)
    - JumpCrisscross 2y ago
      > Iodine-129 has a half life of 15 million years, and would be essentially impossible to confine for that long Seems to be running wild already [1]. Unclear if, due to it being naturally occurring, that would be a definitive signal. [1] https://pubmed.ncbi.nlm.nih.gov/15556197/ https://pubmed.ncbi.nlm.nih.gov/15556197/
- deleted 2y ago
  [deleted]
silverquiet 2y ago
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.
- JumpCrisscross 2y ago
  > How much of a nuclear war? 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] https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.0158 https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.01... [2] https://www.mindat.org/min-560.html https://www.mindat.org/min-560.html [3] https://www.osti.gov/biblio/1024694 https://www.osti.gov/biblio/1024694 [4] https://en.m.wikipedia.org/wiki/Earth https://en.m.wikipedia.org/wiki/Earth
  - sumsome 2y ago
    [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 -.-'
    - JumpCrisscross 2y ago
      [1] should be https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.015801 https://journals.aps.org/prc/abstract/10.1103/PhysRevC.85.01...
actionfromafar 2y ago
But we find fossils of dinosaurs all the time. Wouldn’t tools and stuff also end up in the geological record.
- JumpCrisscross 2y ago
  > 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-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6 https://www.cambridge.org/core/journals/international-journa...
  - throwup238 2y ago
    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.
    - JumpCrisscross 2y ago
      > 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/10.1029/2007GC001743 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... Figure 1 [2] http://www.lithosphere.info/papers/2006-Tecto-Art-TC1-small.pdf http://www.lithosphere.info/papers/2006-Tecto-Art-TC1-small.... Table 1
sumsome 2y ago
> 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.
- lazide 2y ago
  Eh, plagues or evolutionary ‘black holes’ followed by an outside context problem are all possible too. Aka Dodo bird type situation.
delichon 2y ago
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.
- JumpCrisscross 2y ago
  > 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.)
  - IsTom 2y ago
    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.
    - JumpCrisscross 2y ago
      > 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. [1] https://www.smithsonianmag.com/science-nature/oldest-known-stone-tools-unearthed-kenya-180955341/ https://www.smithsonianmag.com/science-nature/oldest-known-s... [2] https://www.sciencealert.com/there-s-mounting-evidence-the-continent-of-africa-is-splitting-in-two https://www.sciencealert.com/there-s-mounting-evidence-the-c...
      - IsTom 2y ago
        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.
BurningFrog 2y ago
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.

dansafee 2y ago

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.

medstrom 2y ago
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.
vikramkr 2y ago
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. 500 million/4 billion is only about 12%.
bitcharmer 2y ago
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.
eru 2y ago
Astronomy can have even wider absolute error margins for dates. Especially for dates that are in the future.

MacrohardDoors 2y ago

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.

medstrom 2y ago
Joke? Or where'd the water have come from?
- MacrohardDoors 2y ago
  Vast lakes, smaller rivers, puddles, you know?
  - JumpCrisscross 2y ago
    > Vast lakes, smaller rivers, puddles, you know? The same volume of water was just…higher?
    - lazide 2y ago
      Notably, that is how melting glaciers raise sea levels.
      - medstrom 2y ago
        So where'd the original glacier ice come from? :-) Earth has 1.386 billion cubic km (333 million cubic miles) of water. Lot of glaciers, that.
        lazide 2y ago
        Not proposing it ever actually happened, but one hypothesis [https://en.m.wikipedia.org/wiki/Snowball_Earth https://en.m.wikipedia.org/wiki/Snowball_Earth]. 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!

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setgree 2y ago

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? 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-tramped-around-north-america-more-than-20-000-years-ago/ https://news.berkeley.edu/2023/10/05/tests-confirm-humans-tr...

JumpCrisscross 2y ago
> 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 Can’t we use genetic drift to bound those estimates?
- davidmurdoch 2y ago
  What's your confidence interval for genetic drift?
- sethammons 2y ago
  If we find a tool site or cave painting, what does that have to do with genetic drift?
  - JumpCrisscross 2y ago
    > 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.
- Symmetry 2y ago
  If there's a subsequent population replacement the estimate will thrown completely off. Edit: And to be clear, not all population replacement is violent. The Norse in Greeneland were gone when the Inuit showed up for instance.

defrost 2y ago

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Symmetry 2y ago

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. [1]https://hopefullyintersting.blogspot.com/2019/04/how-likely-is-it-that-there-was-life-on.html https://hopefullyintersting.blogspot.com/2019/04/how-likely-... [2]https://en.wikipedia.org/wiki/History_of_Earth https://en.wikipedia.org/wiki/History_of_Earth

OJFord 2y ago
'Fresh water' always means as opposed to salt/sea water. 'Fresh water fishing', etc. (I'm not sure where you draw the line in rivers though)
- Symmetry 2y ago
  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.
- didgetmaster 2y ago
  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).