The Silurian Hypothesis | Hacker News Reader

The Silurian Hypothesis

fermatslibrary.com

75 pointsvo2maxer52 comments

That article is full of interesting factoids. My favorite:

> What might distinguish naturally occurring biomarkers from synthetics might be the chirality of the molecules. Most total synthesis pathways do not discriminate between D- and L-chirality, while biological processes are almost exclusively monochiral

The article mentions ocean anoxic events as possible markers of civilizations that ended in disaster. But the opposite might be even more fascinating to ponder.

What if there was a civilization ~2 billion years ago that thrived in the oxygen-poor environment, who accidentally unleashed cyanobacteria upon the world? Kinda like how we're recklessly dumping CO2 into the atmosphere, but on a much grander scale. Life would have had to re-evolve from the unicellular stage, and all evidence of the oxygen-dumping civilization would have been erased by geological forces by now.

The article refers to an interesting paradox:

>>> However, the longer a civilization lasts, the moresustainable its practices would need to have become in order tosurvive

The opposite of a paradox

The paradox is that, because of that the longer a civilization survives, the less visible it would be in the geological record.

That's not a paradox though. More of an archaeological inconvenience.

It's a paradox because a plausible first thought is that the longer a civilization exists, the more artefacts it leaves for future archeologists to find.

The really long term truth might be the opposite, hence there's a paradox (in one sense of the word).

Not a paradox, just an indication that these authors (and you) are not good at thinking like archaeologists. As an archaeologist myself, this whole paper reads like complete nonsense.

I don't think we can imply that 'sustainable' means 'less geological evidence'.

Biologically-produced oxygen resulted in one of the worst mass extinction, with ample geological evidence, but turned out to be quite sustainable.

This might explain "Fermi's paradox".

It seems like all the models of extraterrestrial life being visible rest on the assumption that this life would be the product of the equivalent our present rate of growth continuing and quickly reaching cosmic scales. If that's basically impossible and intelligent life that survives is living sustainably, then we wouldn't have star-enfolding Dyson spheres and similar things that are detectable at cosmic distances.

Or, another possibility is that the sustainability of continuous short-term exponential growth varies from location to location but it's not going to be infinitely sustainable anywhere. Thus we might see blips but we won't see a "colonized galaxy".

IE, the societies that keep up exponential growth to a cosmic scale probably still won't have solved the problem of indefinite exponential growth. We know the ways that, on Earth, the increase in human knowledge and productive produces unintended consequences with significant chances of destroying us. We don't yet know similar mechanism in space but it seems quite plausible these would exist. Dyson spheres aren't even gravitationally stable (see Larry Niven's Ring World series).

I noticed that they didn't provide a citation for that statement, or the statement about "the more sustainable its practices, the less geological impact it would have". I'm not disputing them, but it did cause me to stop and ponder a bit.

If we end up spreading solar panels all over our deserts, and wind farms over our continental shelves, will that be less detectable? Especially since there appears to be natural causes for large changes in atmospheric carbon (volcanoes hitting large oil deposits seems to be the thing they propose for this).

I don't have time to read the entire article right now, but after skimming it, it seems to focus on what we might find but not on what's not there.

Focusing on Earth right now, if human civilization were to go extinct in the near future, whatever comes after us will have a much harder time getting to an industrial civilization (or maybe any civilization) because we have used up a lot of non-renewable resources that aren't ever coming back. Namely, things like abundant and easily accessible coal and oil. There's also things surface metal deposits (tin, copper, iron, etc) which are essential for making those first steps. Granted, we, as a civilization, have placed a lot of metal on the surface but it's scattered all over and I have no idea how much of it will be usable by the roach-people that come millions of years after us with no prior knowledge.

Still, all of that aside, the fact that we have coal today strikes me as a pretty convincing argument that there was no industrial civilization before us. It doesn't rule it out entirely, of course. I can imagine an industrial civilization without coal or oil, but I do have to stretch my imagination farther.

There still is plenty of wood to burn, no?

Wood is much less energy-dense and requires much more manual labour to process. Global steel production only took off after the switch from wood-charcoal to coke made from coal, at Coalbrookdale: https://en.wikipedia.org/wiki/Coalbrookdale

But wood and wood charcoal is still enough to take you past the Renaissance

On geological time-scales (tens of millions of years) fossil fuels will be replenished. In fact the paper presents a speculative, putative mechanism by which an industrial civilisation may inadvertently help provide these resources for future civilisations:

> [...] the prior industrial activity would have actually given rise to the potential for future industry via their own demise.

See page "148", mid-way through the second column for details. (It's a shame that Fermat's Library doesn't provide an interface for deep-linking parts of the article.)

On a time-scale of thousands of years to (probably) single-digit millions of years, you're almost certainly right, though.

Mmm. Maybe. There is a plausible theory [0] that our coal deposits came from the era between when plants learned to produce lignin but bacteria didn't know how to break it down.

Given that lignin eating bacteria are now quite common, it is unlikely coal seams will form of the same quantity and quality.

[0] https://en.wikipedia.org/wiki/Coal#Formation

I believe it's fungus that breaks down the lignin.

I Think there is some confusion between coal formation rate and coal formation volume. My understanding is that more coal has been formed since the cretaceous than during the cretaceous.

Figure 1 in the link below provides a good demonstration of north american coal formation over time.

https://www.pnas.org/content/113/9/2442

> On geological time-scales (tens of millions of years) fossil fuels will be replenished.

Will they? My understanding is that we have abundant coal thanks to the Carboniferous period, during which trees emerged but no organisms had yet adapted to break down lignin, causing massive fossilized tree deposits -- coal. As far as I see, that was an unique period in Earth's history that will not take place again.

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

My understanding is that the carboniferous was a particularly productive coal forming period, but in no way unique. The majority of the coal on earth has been formed since the carboniferous and the process is ongoing today.

Figure 1 in the link below provides a good demonstration of north american coal formation over time/

https://www.pnas.org/content/113/9/2442

Heaps of twisted, rusted steel on the surface is a much more efficient source of iron than iron ore in the ground. Ditto for aluminum, which is easy to handle and recycle once it has been refined (provided you can pick it out of the garbage dump) but terribly energy-intensive to extract from the ground.

Anyone who comes after us will not have much coal and oil to burn, but they'll have orders of magnitude easier access to useful metals. Imagine venturing into the half-collapsed vault of an ancient bank and finding tons of pure gold! There's a lot of fun waiting for the Indiana Jones of the next civilization.

Or washed all the phosphorus deposits to the seas. The future is going to be interesting.

https://phys.org/news/2019-09-global-phosphorus-crisis.html

I would imagine it would be much easier for the next civilization. Instead of individual mines for raw material they would set up shop over old landfills. Lots of highly refined materials there which took us thousands of years to learn how to make.

I wonder if you might find evidence in near-earth orbits.

Would a geosynchronous satellite stay in place after 400 m.y.a? Or a descent stage of a moon lander, perforated by impacts, from a Troodon?

The worst part of this, the realization that the K-T boundary was the fallout of a nuclear exchange.

We are pretty sure KT was caused by a giant asteroid. Maybe the space Silurians redirected it into Earth? (Not serious)

The question would probably hinge on whether they were given to building cyclopean architecture. If the Egyptians were just content to build mudbrick cities, rather than erecting pyramids, colossal stone statues, stelae, obelisks, and the like, they would be much harder to detect.

On geological timescales, that makes no odds. Nothing built of stone will survive natural weathering over millions of years. Mountains don't survive it.

Concrete won't survive it either, even modern reinforced concrete (actually, our modern reinforced concrete won't last as long as the concrete the Romans used, and their concrete might actually outlive lots of ours).

Pyramids made of gold then.

I'm curious about the change in metal availability. From the paper

"The Paleocene–Eocene thermal maximum (PETM)" ... "Additionally, many metal abundances (including V,Zn, Mo, Cr) spiked during the event "

How does metal availability increase like this?

Obviously, our industry will increase metal availability, because we spend lots of time and energy digging through other geological layers and dragging all their metal deposits into ours. But how could this happen naturally?

On a global, semi-uniform scale? Not sure. But locally, maybe intense vulcanism? The Siberian Traps[1] were bringing up material from below ground on a scale that's kind of hard to fathom.

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

that makes sense, though that was a 2-million-year event, so maybe something smaller ;)

I would assume that V, Zn, Mo, and Cr form some compound with carbon dioxide that isn't soluble - so it collects in sediment. Or, it could be the acidity levels? I think it's often the case that metal concentrations come from the release of oxygen from primitive micro-organisms, as the oxygen reacts with elemental metals to form layers of insoluble metal oxides on the seabed.

Check http://geopolymer.org About a concrete technology that probably existed worldwide.

Because a lot of these structures are very old and some are even under water, I think that they likely existed during the ice-age. Later cultures like the Incas build on top of these huge structures.

Fascinating stuff "Archaeologists cannot give any rational explanations on how this was possible."

... "Several people tried to discover the secret of this stone making. They were successful in softening the limestone that they reduced to a soft mass. But they failed to harden it again. This has been the reason, why, 40 years ago, Davidovits and Aliaga stopped their studies. They could disaggregate (limestone) but they were not capable to re-agglomerate it, to harden it again.

The appropriate knowledge was acquired very recently (2 years ago)"

Interesting, but the Prof Joseph Davidovits sounds like he is on the fringe of theories with respect to these stones.

Paper via wikipedia: https://www.tandfonline.com/doi/abs/10.5408/0022-1368-40.1.2...

> It is not easy to give a geological education to a brilliant and determined chemist.

Savage

If you enjoy thinking about epic timescales I recommend Olaf Stapledon's 'Last and First Men: A Story of the Near and Far Future' fairly outdated, heavy going, but unique.

If there is anything more to UFOs than just mass hysteria and wishful thinking, then I've always thought it much more likely that they are from a previous industrial civilization here on earth than being extraterrestrial - the PETM from 56 million years ago would be a good candidate for their home time.

>If an industrial civilization had existed on Earth many millions of years prior to our own era,what traces would it have left

What about space based traces? Abandoned spacecrafts, which can easily remain preserved millions of years.

Wikipedia:

https://en.wikipedia.org/wiki/Silurian_hypothesis

"The Silurian hypothesis is a thought experiment[1] which assesses modern science's ability to detect evidence of a prior advanced civilization, perhaps several million years ago. In a 2018 paper, Adam Frank, an astrophysicist at the University of Rochester, and Gavin Schmidt, director of the NASA Goddard Institute, imagined an advanced civilization before humans and pondered whether it would "be possible to detect an industrial civilization in the geological record".[2]"

The geological record is an interesting possibility -- but a better question might be:

"If you wanted to preserve the record of an advanced civilization across super long periods of time -- how would you do it?"

I've thought about this question long and hard.

Stone buildings seem to last no more than 10,000 years, and by the time they are discovered, they have usually been ransacked by grave-robbers and treasure-hunters:

https://en.wikipedia.org/wiki/List_of_oldest_known_surviving...

Satellites would fall out of orbit by that time, and I don't know any piece of high-technology that has had an uptime of more than maybe 20 years... the more complex something is -- the more prone to failure it becomes.

A USB Drive from an advanced civilization in our past -- just wouldn't make it through to today...

So here's my idea:

Why not put the knowledge of an advanced civilization, into the DNA of some plants? 98% of DNA is unused, aka, non-coding DNA, aka, "Junk DNA":

https://en.wikipedia.org/wiki/Non-coding_DNA

So... why not put it there?

But... there's a problem! DNA is going to shift around a bit over time, so we're going to need to account for that! (We'd accomplish this by replicating the same information over and over at least several times).

So with all of that in mind -- here is my top candidate as one potential carrier of that information:

https://www.sciencemag.org/news/2010/10/scienceshot-biggest-...

The Flowering Plant: Paris Japonica

Why?

Its DNA apparently contains 130 billion base pairs... that's a lot of room for information, and replication of that information!

Maybe there's something in there, or then again, maybe I'm a crackpot!

History will tell! <g>

But, that would be my top candidate for where that information might be, if it exists anywhere at all...

I'd build something that's impossible to miss, and hard to destroy. A stone henge on the moon maybe.

Or just a moon.

This is actually the premise of a Star Trek TNG episode. They combine the dna from species and receive a message from their distant ancestors.

I’m more curious what sorts of communities exist(ed) which didn’t have our predilection for changing the environment. I’m sure vastly different environments lead to vastly different needs. Would we build homes if we essentially already lived in a climate as controlled as a house?

Obligatory Dresden Codak: http://dresdencodak.com/2009/07/12/fabulous-prizes/

A fascinating read!

Unpopular opinion(?): Fermat's Library makes the experience of reading papers worse. This and many other linked papers I see there seem interesting, but I'm not interested reading in the marginalia, or logging in, or signing up for their mailing list to receive a paper every week.

What I would like to do is download the PDF and read it on my iPad, or even print it out. But if that's possible, I haven't been able to find the link or button to do it.

Save to books or pdf on your iOS device through Share Page With..., then read at your leisure. You can also print it the same way. There is no need to create an account. I hope this helps.

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

On some physics papers on Fermat’s Library the good comments are drowned out by the crank posts. Not a fan.

> Unpopular opinion(?):

Not that unpopular.

(Partially tongue-in-cheek:)

Select the doi, in this case on the left side of the first page, but usually present somewhere in the article, and paste it in a new tab. In this case:

https://doi.org/10.1017/S1473550418000095

which leads to what zgniatacz linked.

Reply on news.ycombinator.com