If there were any high-intelligence species before they must have exited in a time predating current coal and oil formation, or were not technologically capable, or found some other way of harvesting energy. The fact that we found massive amounts of planet-killing coal and immediately started exploiting it with abandon means that that did not happen before, ergo no technologically capable species on this planet for at last 300M years back. Now you could argue that 'intelligent species' tend not to shit in their own beds. We talk about Fermi filters for a reason.

Do keep in mind that diversity enables diversity. If biosphere complexity falls enough changes are it will never recover. Earth had live almost immediately after formation. It took more than 2.5B years for something more complex to emerge from the ur uni-cellular broth. Evolution or linear increasing complexity is not guaranteed by any means. What will a chimp bashing rocks in the bush be doing in 1000 000 years? Building quantum computers or bashing rocks. Overwhelming evidence points to bashing rocks.

I absolutely believe that any intelligent species that has enough intelligence to become interstellar will heavily invest in camouflage and become a lurker. Only reacting when something threatens its survival. The universe is like a jungle full of scary things, the only wise move is to watch out, be invisible and not make a lot of noise.

I get your point, but I posit that this is a very human point of view. Once you've cracked the energy needs for interstellar travel, what's the point of raising a war campaign light years away (especially if you need generation ships to attack)? Furthermore, it doesn't seem very intelligent to me that all capable species just hunker down in their own gravity well to die off unnoticed and without having explored the universe. Humans have thus far always endeavoured to go one step beyond; why stop now?

Besides, I'd rather we risk ending up on the galactic buffet table for the chance of finding life forms we can "compare notes with". We're all going to die and go extinct regardless.

They wouldn't need generation ships. You "just" need sufficient tech to put engines on a suitable astroid and accelerate it to a decent fraction of c; it only needs enough logic to fine tune the path. An invasion force is horribly inefficient vs. just slamming a lot of mass at someone at high enough speed.

And it only takes one massively paranoid, xenophobic species lobbing big rocks at people to ruin the entire neighbourhood.

I don't think camouflaging necessarily means not leaving your gravity well, but if there's someone lobbing big rocks at potential threats, then the only ones exploring will be the ones powerful enough or good enough at hiding for us to be unlikely to spot them unless they want us to. Everyone else will be dead.

It's one of the more compelling answers to the Fermi paradox to me, while at the same time being profoundly depressing. But it's less depressing than the chance that there might not be any other civilizations.

It's funny, I just spent the last 18 months deep-diving into the history and literature of World War 1.

"And it only takes one massively paranoid, xenophobic species lobbing big rocks at people to ruin the entire neighbourhood."

Ahh, Germany ...

> They wouldn't need generation ships. You "just" need sufficient tech to put engines on a suitable astroid and accelerate it to a decent fraction of c; it only needs enough logic to fine tune the path. An invasion force is horribly inefficient vs. just slamming a lot of mass at someone at high enough speed.

I misplaced a link and the name of an author of a sci-fi novel in which space battles are much more science based than the usual laser-tag shoot off. I'll dig through my bookmarks and hopefully post the name in the reply when I get to my pc..

I think there was also a reddit thread about it sometimes in the past.

The Remembrance of Earth's Past series by Liu Cixin? It also has the "lurker" theory of cosmic sociology being discussed in this thread.

Isn't that only a problem if you're completely planet-bound? If you want to play it safe, you shouldn't put all of your eggs into a single basket anyway.

Correct, but while exploring the universe, doing it undetected is actually a great strategy. Imagine self replicating nano bots that embed themselves into asteroids. Everything thinks its just big rocks flying in space that sometimes smash into planets. But its a strategy to slowly colonize the galaxy and put a mark everywhere. Kind of how plants spread their pollen into the wind or have bees and butterflies do their dirty work.

An interesting view on this perspective can be found in the sci find novel 'the killing Star'

https://en.m.wikipedia.org/wiki/The_Killing_Star

If this is interesting to you, read The Dark Forest: https://www.goodreads.com/book/show/23168817-the-dark-forest...

Thanks for the recommendation

This is an interesting theory. Perhaps you could expand on it and form a new social science called "Cosmic Sociology".

Aren't Twitter, FB and selfies a sign of the opposite happening at the micro level?

Despite the occasional swatting, for the most part the consequence of being spotted on social networks is not to have the local lunatic show up to shoot you in the face.

That's a rather significant difference to the proposed idea.

He was talking about intelligent species.

Good thing we're keeping so quiet then... :P /s

1000000 years ago, homo erectus was bashing rocks. You cannot really know what Bonobo chimps are going to evolve into so far in the future.

Curious if anyone's ever observed something similar to this? It'd be super easy to detect if you're looking for it, but most miners aren't thinking "Hmm, I wonder if a previous intelligent species existed on earth millions of years before us."

Mining companies generally hire very smart geologists who care a lot about the processes that shape resource deposits, in order to predict where new deposits will be found. If there were any pattern that didn't fit with natural processes people would notice

Surely if a previous society extracted megatons of ore from the ground there would be something left of that civilisation. At least a wheel track or a scrape mark, not to mention maybe a spanner.

Pretty sure evidence of Roman metallurgy can be detected in the ice record.

http://science.sciencemag.org/content/265/5180/1841

I started thinking that another species after us would find it odd that there are so few hydrocarbon deposits - but would they look for something that's not there?

Similarly, maybe there's something missing from the Earth that we're just not thinking of because, well, you can't miss something if you never had it.

The fungus (white rot) that breaks down an important binder in woody plants (lignin) had not yet evolved when the plants that make up our coal and gas deposits died. because white rot now exists, we aren't making new coal or oil at anywhere near the same rate.

https://www.scientificamerican.com/article/mushroom-evolutio...

If we cause a mass extinction, including that of ourselves, wouldn't we be creating a lot of hydrocarbon deposits eventually?

(Not asking critically - serious, I have no idea, do billions of people and whatever else we take down with us replenish what we've pulled out of the ground?)

My understanding is that most of them came from plant life, and a lot of that from the ocean - so I don't think the animal biomass would really add that much.

That's assuming intelligent life always builds an industrial civilization...

How else could they cope with growing needs for goods or, say, entertaiment as their civilization develops?

Or would you then argue that intelligent life could develop sort of moratorium on further development in line with their value system?

Or they fail to thrive like humans have. Early humans were few in number and might have nearly died out a few times. We just got lucky.

I've also wondered how a race without something like a hand ever gets around to making complex tools with multiple moving parts. If Dolphins had twice the brain power that they do now, would they be able to build anything? The intelligence of other races may simply fail to be expressed in any way that is noticeable once they are gone. Hell dinosaurs might of been smarter than us and simply unable to use and create tools.

I don't think you're allowed to pose the dolphin question. If we assume that dolphins and humans have a common ancestor and that the dolphin branch ever had a need for using tools to sustain their species, over time enough random permutations of specific genes would have selected those dolphins which had appendages capable of aiding in the use of tools. As it turns out, they did not need to have hand like appendages to survive and thus apes have hands and ocean mammals do not.

Given the constraints (earth located in our universe) of the probability space of physical interactions which produce life, I believe that our current state is the only possible state.