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

https://www.curtin.edu.au/news/media-release/fresh-findings-earliest-evidence-of-life-bringing-fresh-water-on-earth/

by geox • 2 years ago

69 76 2 years ago

curtin.edu.au

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-journa...

vasco• 2 years 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?

JumpCrisscross18• 2 years 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-journa...

silverquiet• 2 years 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.

JumpCrisscross18• 2 years 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.85.01...

[2] https://www.mindat.org/min-560.html

[3] https://www.osti.gov/biblio/1024694

[4] https://en.m.wikipedia.org/wiki/Earth

actionfromafar2• 2 years ago

But we find fossils of dinosaurs all the time. Wouldn’t tools and stuff also end up in the geological record.

JumpCrisscross18• 2 years 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-journa...

sumsome2• 2 years 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.

lazide6• 2 years ago

Eh, plagues or evolutionary ‘black holes’ followed by an outside context problem are all possible too. Aka Dodo bird type situation.

delichon• 2 years 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.

JumpCrisscross18• 2 years 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.)

ComputerGuru• 2 years ago

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.

BurningFrog• 2 years 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• 2 years 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.

medstrom5• 2 years 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• 2 years 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• 2 years 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.

eru2• 2 years ago

Astronomy can have even wider absolute error margins for dates. Especially for dates that are in the future.

MacrohardDoors2• 2 years 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.

medstrom5• 2 years ago

Joke? Or where'd the water have come from?

MacrohardDoors2• 2 years ago

Vast lakes, smaller rivers, puddles, you know?

setgree3• 2 years 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-tr...

JumpCrisscross18• 2 years 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• 2 years ago

What's your confidence interval for genetic drift?

sethammons• 2 years ago

If we find a tool site or cave painting, what does that have to do with genetic drift?

Symmetry3• 2 years 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.

flatline• 2 years ago

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!

sameerds2• 2 years ago

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.

To me the second option is akin to despair.

setgree3• 2 years ago

I mean in terms of bounds of years. In other words, how much uncertainty surrounds our new estimates.

Symmetry3• 2 years 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-...

[2]https://en.wikipedia.org/wiki/History_of_Earth

OJFord• 2 years 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)

Symmetry3• 2 years 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• 2 years 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).

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

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