The Silurian Hypothesis

[dps]

If they were anything like us, they would have altered the landscape in easily-recognizable ways - for example, highway cuttings through solid bedrock. These would still be visible millions of years later.

The time scale involved is enough for substantial continental drift.  Entire mountain ranges can form, or be eroded into nothingness.

As Mongers pointed out, we have a pretty good fossil record with no signs of a civilization.

As I pointed out, we don't have a very good fossil record.  Take a dinosaur like therizinosaurus - it's kind of famous because of it's extremely long claws, but it's only known from a couple of partial fossil remains - we don't even know what kind of head it had. 

And the dinosaurs existed for over one hundred million years - lots of time to leave fossils.  Human civilization has been around for what - 5,000 years?  And advanced technology only for 100-200 years.

I agree it's extremely unlikely, but the concept isn't quite so insane as you might think.

Your argument that there may be some specific fossils missing from the fossil record does not address the fact that there are no signs in any of the fossil record we do have.  For the theory to work there would have to be some as yet unexplored fossil lawyer in which the civilization is waiting to be discovered.  Not some detail within well explored fossil layers. 

To put it another way, there has been absolutely no signs of civilization in any of the context in which the numerous fossils we have were found.

OTOH, I've seen estimates that we only have fossil records of 1% or less of all species that have gone extinct.  Of course, most of those would likely be microscopic, but still.

[alfred russel]

Human history is so incredibly short it may make it difficult to find traces hundreds of millions of years from now (assuming it all ends in a poof in the near term), but the natural history of the world would presumably take a sharp turn--we are likely in a significant mass extinction event as we speak.

I think a more relevant question is not whether an advanced civilization lived some distant time ago, but whether we are grossly underestimating the amount of life in the precambrian.

[alfred russel]

Something that really hit me about the dramatic changes over geologic time was the statement that a regional mountain (about 2k m) would be around long after we were. While undoubtably true, I began thinking--the mountain gets a ton of hikers--it seems only logical that from erosion it would lose a 1 cm a year at least. That means a meter in a century. At that pace, in just 200k years--not even a blip in geologic time--it would be at sea level.

[mongers]

Something that really hit me about the dramatic changes over geologic time was the statement that a regional mountain (about 2k m) would be around long after we were. While undoubtably true, I began thinking--the mountain gets a ton of hikers--it seems only logical that from erosion it would lose a 1 cm a year at least. That means a meter in a century. At that pace, in just 200k years--not even a blip in geologic time--it would be at sea level.

A possible flaw in your argument, I guess hikers aim for the top of the mountain, so as they wear it away 1cm at a time, then increasing numbers will have to be spread out over the consequent larger area revealed, so as to continue that rate of erosion.

By the time the mountain is down to half height, there's now an awfully big area that needs to be eroded by a rather large number of not too imaginative hikers.

[alfred russel]

Something that really hit me about the dramatic changes over geologic time was the statement that a regional mountain (about 2k m) would be around long after we were. While undoubtably true, I began thinking--the mountain gets a ton of hikers--it seems only logical that from erosion it would lose a 1 cm a year at least. That means a meter in a century. At that pace, in just 200k years--not even a blip in geologic time--it would be at sea level.

A possible flaw in your argument, I guess hikers aim for the top of the mountain, so as they wear it away 1cm at a time, then increasing numbers will have to be spread out over the consequent larger area revealed, so as to continue that rate of erosion.

By the time the mountain is down to half height, there's now an awfully big area that needs to be eroded by a rather large number of not too imaginative hikers.

Definitely--at a certain point we are talking about eroding basically the eastern seaboard of North America to sea level.

My point was more that 1 cm of activity may not seem like much in a year, but over geologic time that is race car fast.

[Razgovory]

I think you are mistaken with the idea of hikers eroding a mountain.  To lower mountains you'd need to remove millions of cubic meters every year.

[mongers]

I think you are mistaken with the idea of hikers eroding a mountain.  To lower mountains you'd need to remove millions of cubic meters every year.

I think AR is just revealing more of his Buddhism.

[alfred russel]

I think you are mistaken with the idea of hikers eroding a mountain.  To lower mountains you'd need to remove millions of cubic meters every year.

You don't just have erosion at the very summit...you have erosion all the way up and down, plus reduced vegetation leading to more runoff.

Heck, my guide on the matterhorn is building a fireplace for his house with stones from the matterhorn--every time he goes he brings back a stone. There are a lot of stones on the matterhorn, but if people kept doing that for 2 or 3 million years? It would make a difference.

[dps]

I think you are mistaken with the idea of hikers eroding a mountain.  To lower mountains you'd need to remove millions of cubic meters every year.

You don't just have erosion at the very summit...you have erosion all the way up and down, plus reduced vegetation leading to more runoff.

Heck, my guide on the matterhorn is building a fireplace for his house with stones from the matterhorn--every time he goes he brings back a stone. There are a lot of stones on the matterhorn, but if people kept doing that for 2 or 3 million years? It would make a difference.

I'm not sure about the Alps, but some mountain ranges (the Andes for example) are still growing, which would probably more than offset anything hikers or climbers can do.

[alfred russel]

I see why cdm accused everyone of having aspergers. My point was not that hikers are going to erode away the mountains. My point was that even what seems to us to be very modest rates of change--on a geologic time scale--may be operating at a break neck pace.

[dps]

The problem is that you made your point very poorly, not with our reading comprehension.

[grumbler]

The problem is that you made your point very poorly, not with our reading comprehension.

Marti doesn't post here any more, so AR has taken up the mantle of making really shitty analogies.  It's a tough job, but he is a tough man - tough enough to insult everyone who points out shitty analogies when they see them.

[Tamas]

I see why cdm accused everyone of having aspergers. My point was not that hikers are going to erode away the mountains. My point was that even what seems to us to be very modest rates of change--on a geologic time scale--may be operating at a break neck pace.

It did read like you attributed erosion solely to hikers walking the mountain down.

[fromtia]

Read about the Silurian Hypothesis when it arrived on the internets a few weeks ago and thought it was delightfully nutty. More stoner science than actual science I thought, but fun none the less.

Made me immediately think of Harry Harrisons books with the intelligent reptile civilization, which are great fun as well.

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

The Julian May books about the discontents who get sent on a one way trip back in time only to discover that the the Pleiocene Earth is hosting a crashed alien spaceship who have enslaved our hominid ancestors also springs to mind.

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

[KRonn]

Interesting, and this idea has crossed my mind before but as others point out, how we haven't found any traces of a prior civilization yet we've found dinosaur artifacts. The article doesn't point out why that could be, as I assume fossils of bones would have been found. Or if they were advanced far enough other items that would endure over a long time such as metallic objects could be found.

The other side of things could be that we keep finding new types of dinosaurs and pre-human remains so there's always a lot more to discover.