How do you differentiate an event that is very improbable and so takes a billion years from an event that is inevitable, but requires many prerequisites, and so takes a billion years?
The article seems to simply assume the former model ("We assume that once an evolutionary transition is possible (i.e., once the previous transition has occurred), it occurs at a constant average rate λi, so that each ti is exponentially distributed with an expected transition time of βi = 1/λi"), but that feels unjustified to me. Is it really the case that the transition from prokaryote to eukaryote was equally likely at any time, and things simply sat stagnant for a billion years until one day life got lucky?
This doesn't contradict the conclusion of the paper, it makes no difference as to whether we're going to find anybody we can have a conversation with, ("hey, how annoying is light speed?") but I think our definition for simple and complex life is off.
eg "more likely to find simple life on Mars."
That ape and octopus exist, says that earth didn't win the intelligence lottery, we are watching the long slow grind of compound interest.
When you look at our world we see that the lipid bilayer is preserved, that rna is preserved in every living thing, but eyes have evolved independently many times. That the last common ancestor of octopus and human was a little wriggly thing, leads me to believe that forming a boundary between self and non self is hard (the bilayer), that forming a system of heredity is hard (first rna then dna). That the accumulation of processes that use energy, resources and information from the environment in new ways is a long relentless grind. The basic body form, multicellularity and a gut were, big difficult changes, but maybe intelligence is just paint on a hard won foundation.
Yeah, in the discussion of "where is the intelligent life", you seldom see the argument that it really does takes 11+ billion years to produce that intelligence life. With a universe "only" 13 billion years old and possibly chaotic, this factor, rather than any specific "filter", might why we're not seeing any other intelligent life.
Consistent with that, evidence suggests that it may have taken billions of years for the precursor molecules of the first Earth-based life to emerge/evolve:
The Earth is made of elements that were formed in supernovas.
We had to have several generations of stars formed out of the remains of older stars that blew themselves apart, to have more than trace amounts of any element apart from hydrogen and helium.
Earliest you could get rocky planets is probably a couple of billion years after the Big Bang. But more time is better.
> an event that is inevitable, but requires many prerequisites, and so takes a billion years?
In support of this idea, the Cambrian explosion of large (large relative to microbial life) multicellular organisms happened immediately after the 2 billion years of work by blue-green algae had produced enough oxygen into the atmosphere to make larger organisms possible.
The article mentions that multicellular life is something that's known to have separately evolved at least 40 times, so it's probably not a useful evolutionary step to compare to ones that only happened once.
While it made complex life possible, at the same time the introduction of oxygen also killed a lot of lifeforms and was a mass extinction. It's not inconceivable that with slightly different circumstances it could have just have wiped out all life. The development of (complex) life seems like a really fine balance.
Precisely. Something taking astoundingly long to evolve isn't conclusive evidence that it's highly improbable (although it might suggest it). It could very well be highly probable. One reason is as you mention is prerequisites. Another reason could be that the solution is deep in the search tree, and while it takes ages to find it, the search algorithm will eventually do so. Consider a global optimizer running on a concave surface for a long period of time, all it needs is time.
Just realized that the eye is a counterexample to their assumption. Took three billion years to evolve but is easy to do so as we've seen it evolve independently many times.
How do you differentiate an event that is very improbable and so takes a billion years from an event that is inevitable, but requires many prerequisites, and so takes a billion years?
I suspect that' gnawing for any research like this. But I could suggest that if we can show that a lot of fundamental changes have come from external shock rather than internal processes, then we might be closer. Further, if the theory of "puncture equilibrium" is true[1], that this would tend to be the case. If we can show that many evolutionary steps involved such external shocks, then we might be closer to this also.
The question would be whether external shocks inevitably produce advances or whether such advances are indeed lucky.
Punctuated equilibrium doesn't really change the calculations involved in the article. Either mutations happen randomly on their own, or random events cause bursts of mutations to happen. The burstiness doesn't matter much when you zoom out enough.
Punctured equilibrium can matter if fundamentally new adaptation happen only or primarily with external disruptions. Mammals replaced reptiles after a mass extinction event cause by a meteor - another world might not regular meteors or might have too many.
The question is how non-earth world might fail, right.
It doesn't matter to the equations whether you're modeling the chance that a mutation happens on its own, or the chance that an event happens that causes the mutation. You would use the same equation to model either of those.
If the transitions were inevitable given the time they took here, then we would expect to see the transitions happen concurrently throughout the planet in many separate instances. But we see a number of important transitions that happened exactly once on Earth.
Not necessarily. A number of stages in the evolution of life require a planet devoid of more complex life forms. Spontaneous generation of cells, for example, requires very high doses of molecules that more complex life forms eat.
Also worth pointing out that this applies to some potential 'Great Filter' events that we haven't yet encountered. If intelligent cultures don't explore the universe because they destroy their own planets in destructive wars as soon as they have that level of technology, then conditional on our existing, we should expect to be the first such culture to evolve on our planet. If on the other hand, most intelligent cultures neglect to explore the universe because they are busy with art, contemplation or hedonism, we might expect to exist in a world where hyperintelligent dinosaurs, frogs and cephalopods are already sitting around enjoying these things. The fact that they aren't means that maybe our current stage of evolution was hard to reach.
Why hubristic? Because he did it? What would a non-hubristic attempt to estimate the prevalence of life in the universe look like, short of actually finding aliens?
I said 'hubristic' because it seemed to me that the inability to draw conclusions about the cosmos from our own (single data point) limited perspective was a fundamental limitation of the human condition.
It also seems to assume that there is only one "path" to "observer" status. For example, could there be an alternative to Eukaryote cells that would allow equivalent cognition to our own? We don't know because we only have one instance of "observers" coming around.
Sure, all of this is speculative, but the eukaryotic jump is notorious for getting casually dismissed on account of being misunderstood. I think it's one of the better candidates for a filter, so let me advocate it for a second and make sure that if you still want to dismiss it's not due to oversight.
The problem has nothing to do with having a nucleus. That's the solution. As you note, it's possible to imagine other solutions. The problem is dealing with gigabytes of genetic data instead of mere megabytes. Typically one would use units of base pairs, but in the context of talking about potential alternative forms of life I'd argue that units of information are more appropriate. In any case, the "easy" strategies suffer from a severe dead end that prevents them from going beyond a few megabytes. Lots of things go wrong at that limit, and while other forms of life would encounter those obstacles in slightly different places, the problem of "simple strategies that don't scale" is almost certainly universal.
It's not an easy task. The strategies are highly elaborate and severely intrusive. They touch the most fundamental, highly conserved aspects of the genome, of cell functionality, and of reproduction. Genes have to be organized hierarchically, packed and unpacked, and everything that interacts with them has to be made compatible with that reality. Further, everything must be done in parallel. The entire architecture of the genome changes as a result. It's like a distributed system vs a monolith. It's a tough, deep-reaching transition to pull off, it's a tougher transition to justify, and that's if you're an engineer capable of things like planning, prediction, and delayed gratification! A greedy optimizer bumbling around in the dark can't rely on cognition (or even a hype cycle!) to propel itself from one mountain range of local optima to another mountain range.
I'm sure there are plenty of strategies for scaling genomes, but if they're all difficult -- and the crazy elaborate mechanisms we see in Earth eukaryotes suggest that could be the case -- then they still constitute a filter.
But yeah, this is all speculation. Nobody really knows.
This is a much more interesting argument than the ones downthread about mitochondria, et al. It seems to me to increase the urgency of understanding eukaryotic and archaean evolution so we can get a handle on exactly how hard that jump was.
Certainly everything you say is true for our genetic chemistry, but I don't see a reason why that is necessarily true for all genetic chemistry. For example, our data storage for computers scales from megabytes to gigabytes very well. There's no reason to think there aren't other solutions that scale just as well.
Life on Earth evolved histones, nuclei, chromosomes, and all the crazy eukaryotic infrastructure instead of altering genetic chemistry, suggesting that doing so would be an even taller order. Each emergence of life probably only gets one roll of this die. While I'm sure a chemistry exists that supports vertical scaling 1000x beyond our own, it's not unreasonable to speculate that such genetic chemistry could be rare.
Energetics and thermodynamics are absolutely capable of imposing harsh boundaries. How long has our battery technology been stuck at this order of magnitude? How long have internal combustion and explosives been stuck at this order of magnitude? A long time, and that's with an enormous number of very clever and motivated people chipping away at the problem.
There's a reason why I chose distributed systems in my analogy: it proves that information science and engineering are not immune to the "difficulty barrier" problem. Vertical scaling hit a soft limit in the software industry long before it enabled the largest cloud-scale applications we see today. The transition from vertical to horizontal scaling was painful, but not nearly as painful as it would have been to wait for vertical scaling to catch up. We'd still be waiting.
> While I'm sure a chemistry exists that supports vertical scaling 1000x beyond our own, it's not unreasonable to speculate that such genetic chemistry could be rare.
This is what I'm talking about. Your making an assumption and straight up saying it's an assumption, but not providing any evidence that this assumption is true. You make another analogy which may or may not apply. I'm not saying you're wrong, and I'm not saying that you're right. I'm saying there is no possible way any of us can know at this point.
This entire field is speculative and nobody argued otherwise. Quite the opposite: I bent over backwards to redundantly state it over and over again. More than I should have, and now I'm beginning to wonder why I bothered if it didn't prevent me from being ignored.
The "you can't prove it" objection must be checked at the door for the sake of keeping the speculation interesting. Nobody is arguing that you should walk through the door. It's probably more respectable to refuse, on the whole. Once you walk through the door, though, complaining about proof is a bit silly, like walking into a speakeasy, ordering a drink, and complaining that they have served you illegal alcohol. It's not wrong, but it's also not helpful.
If the solutions are trivial, we would see them emerge in the insane amount of time it took to eukariotes to apprear. The fact that they didn't suggest they either do not exist, or are equally difficult.
I'm clearly not articulating this well, so let me try to try another tactic.
The evolution of eukaryotes is based on the specific path that Earth went down. The combination of RNA, DNA, proteins, and other cellular chemical building blocks are a way that a cell could be constructed, but not the only possible way a cell could be constructed. For an extreme example, we could have non-carbon based life. If that is true, then all of our assumptions about what is scalable and what is not, based on our biochemistry simple cannot be trusted. So, looking at how long it took for something to develop on Earth tells us basically nothing about how long it would take to do that with this other biochemistry.
I've made the "yes, we know this is speculative" rant in another post. Here I assume you're still interested in moving forward with the speculation. If not, please don't belabor the point.
There is a substantial body of abiogenesis experimentation focused on reproducing DNA/RNA proto-life. They haven't managed to make anything that self-replicates, but they have managed to make nucleic acid polymers with catalytic activity, e.g. you zap the primordial soup with lightning, you get a bunch of short sequences, some of those sequences fold into RNA-zymes that catalytically produce long "AAAAAAAAA" sequences or long repeating "AUAUAUAU" sequences. The critical next step is to demonstrate the ability to do this from a template.
In any case, are you aware of research that aims to do this with alternative polymer chemistries? Such results could inform our speculation about the likelihood of a fundamental 1000x difference.
That does not actually matter - most planets cannot be habitable for very long and stars change in brightness - eath will become uninhabbitable in a billion tlyears. So most life would die before evolving intelligence.
I don’t think we can really make this claim. Life which forms around less stable stars may adapt if there is enough time for them to do so. It’s also important to note the sun is not the mean star. The vast majority of stars are red dwarves which, while more variable, are much longer lived.
“On Earth” is the problem with the argument. If any alien life exists, the one place it isn’t is Earth. A super-Earth in a Goldilocks orbit around a K1V star would keep atmosphere and water for longer.
Eventually they too will become uninhabitable, but the relevant question about alien life is not “eventually” but rather “now”.
Haha! I don't mean to imply that I've uncovered some fatal weakness (or even necessarily a weakness at all)! That's just the question that jumped to mind when I read their paper, and I figured someone else might know the answer.
Science is about testable, falsifiable hypotheses. It's important to question what we think we know, and how we know it.
"Argument from authority" isn't scientific. We can simultaneously believe (a) that well-respected researchers from a well-respected institution are capable of carrying out well-grounded research and (b) that research is in principle understandable with sufficient interrogation. Authority supports (a) but does not render (b) unnecessary.
I think his point, though not well made, is that it’s likely parent is not the first to ask this question and that the researchers have likely already thought about that.
Yeah, both this and the original question are good points. I wonder what the paper itself has to say.
The early bits are pretty readable so far [0], but I doubt it calls the original question out quite as succinctly as it was asked. Lots to mull over though!
I'm fairly amenable to the interpretation that something like prokaryotic-to-eukaryotic jump is a real high barrier.
I would be pretty unsurprised to find prokaryotic life at least sometimes. I would be much more surprised to find eukaryotes possibly at all, and probably at any high frequency.
Doubt it. Cellular endosymbiosis has happened lots of times on Earth. Besides the common algae symbiosis, I once read a paper that contained a casual reference to dinoflagellate-based organnelles in a larger cell. And dinoflagellates are eukaryotes themselves!
Good find. I might have actually remembered the dinoflagellates on the wrong side of the endosymbiosis relationship in my example (this is either similar to our the same as the one I read). The broader point stands. :)
Why would you think that the prokaryotic-to-eukaryotic jump is higher?
If it is engulfment of organelles like mitochondria, that happens all the time. There are fairly good models of the evolutionary tree and how it could happen over time[1].
On the other hand, the ribosome is an amazingly complex machine, which I would expect would be much harder to create. Even synthetically, the path to build a synthetic eukaryote seems a lot easier than the path to build a synthetic ribosome.
It's not clear to me how much these features can be degraded without destroying the ability for organisms to reproduce with heritable traits.
Also, when listening to these videos, ask yourself 'how' and 'why' any time an action is described. For example, the following parenthetical questions from a small chunk of the 'Translation' video:
"The addition of each amino acid is a three-step cycle; (Why three step?)
First the tRNA enters the ribosome at the A-Site (Why does it only enter at the A-Site? How are other options prevented and/or made inconsequential? Was it always this way? How did the features of the A-Site evolve for this to happen. What happened before this? ), and is tested for a codon / anti-codon match with the mRNA. (How is the tRNA tested? What happens when it fails the test or is missing the amino acid? What is the energy budget of this test and what are the specific features of the ribosome, RNA, tRNA and amino acid that make it possible? What happened before this testing was done? How did we get from the lack of ability to test and the ability to test?)
Next, provided there is a correct match, the tRNA is shifted to the P-Site (What is the mechanism of this shifting? Why does it only go one direction? What is the energy budget of this process and how is it powered? How do we prevent multiple tRNA from shifting or keep it from shifting more than one spot? What occurred before the ribosome/RNA/tRNA/amino-acid had the features to allow this to occur?)"
The systems are very complex, but what I see is a few active sites and a bunch of random stuff that happens to hold them in the right spots to control them a bit.
When reasoning from first principals about immune response, it occured to me that just a few simple processes might be all that is required to explore novel active structures in an organism.
Based partly on my understanding of a study of bacteria that evolved the ability to metabolise a new nutrient, a mutation prior to use is required. The ability to detect a molecule might evolve based on immune responses that use random sequences as "test" active sites that are checked for a specific type of deformation.
If this random sequence deforms immediately, it is discarded because this sequence either deforms automatically or deforms in the presence of something common to "host".
If the test remains negative it is released from the host training environment. If the test pattern deforms some time later, it has detected a "foreign" molecule, and has the potential for use as part of a protein that manipulates this molecule.
Recovering the sequence that detects this new foreign molecule becomes the first step in a hereditary immunity. It also stores this useful sequence for possible use in other "testing" systems. These might bring 3 or 4 of these random test systems together to perform another test.
Simple systems that explore a complex space can come up with seemingly elegant solutions.
The most obvious answer to any of your questions is that, if it worked a different way, that's what the video would show... or there would be no video at all.
I wonder how often eukaryotes were created but then failed to outcompete the existing prokaryotes. Complexity often results in poorer algorithmical fit in the short term.
Indeed. It's probably the case for every step in the evolutionary ladder.
As for eukaryotes, often, evolution rewards larger size, simply because if you are larger you can't be eaten as easily, you can eat larger prey more easily, etc. Compared to prokaryotes, eukaryotes are gigantic. And they seem to cover the niche of huge lifeforms really well.
But would have that been the case for the first eukaryotes? The very first might have been a similar size to its predecessor, no?
I wonder how many early iterations of eukaryote might have actually been smaller, perhaps, if the organism required additional energy sources to support growth.
Eukaryotes have lots of ribosomes, so I'm confused about why it would be easier to create eukaryotes.
And while bigger cells absorbing smaller cells happens all the time, it seems extremely, extremely rare that those events lead to reproducing life. It's probably happened 2X on earth (whatever lead to the original eukaryotes, and the absorption by that lineage of cyanobacteria).
There are tons of insects with novel endosymbionts. For example, Camponotus ants have some novel endosymbionts - https://pubmed.ncbi.nlm.nih.gov/8866472/ . There are even synthetic endosymbionts nowadays (e coli in yeast), and there are cytoplasmic parasites like Wolbachia that you could imagine evolving into an endosymbionts.
On the other hand, even if had only occurred 2x, ribosomes occurred 1x - all ribosomes are related to each other and didn’t evolve separately.
Engulfing new creatures is a lot easier for large eukaryotic cells without a cell wall than it is for prokaryotes or archaea. We have a model of how it happened but there were a lot of problems that had to be overcome in the process, problems that didn't later have to be overcome for chloroplasts, etc.
My understanding is that metabolic-induced stress (degradation, esspecially genetic) was a major factor.
It's also possible that earlier similar transitions occured but were overwhelmed by the surviving eukaryotic line, whether due to greater metabolic effectiveness, superior repair capabilities, or other factors.
>So just looking at the timelines involved it seems like the origin of life wasn't the hard part.
The OP twitter thread has a very interesting counterargument to this point in your article:
>Life emerged fairly early on Earth: evidence that it is easy and common? Not so fast: if you need multiple hard steps to evolve an observer to marvel at it, then on those super-rare worlds where observers show up life statistically tend to be early.
At least this does just amplify your conclusion, that intelligent life is more likely to be exceedingly rare rather than die out prematurely.
According to Wikipedia symbiogenesis[1] is the leading theory for the development of eukaryotes.
If this holds, then multicellularity is not at all a hard step from eukaryotes. It's just more of the same.
From a similarly naive viewpoint, once you have evolution, predation, and liminal environments, intelligence is going to be selected for to some degree.[2] It's by no means any kind of saltation.
So one hard step, abiogenesis (maybe-I have doubts about that too).
2. And that's what we have, some degree of intelligence but not much. We can barely understand the input from a few thousand pixels in our foveas (we live about 80 ms in the past), and mostly can't operate our eyes and speech processing centres at the same time.
The argument regarding intelligence is that the type of intelligence which humans show is rare on Earth as a evolutionary strategy. Other highly intelligent animals do not seem close to even the first steps of space exploration. Perhaps a better term than intelligence is 'culture'.
The fact that human abilities are very limited in some ways supports this. For most evolutionary branches it was a much better strategy to develop excellent eyesight, hearing, running or fighting than to trade off mediocre ones against a sort of general-purpose intelligence and communication skills.
>Other highly intelligent animals do not seem close to even the first steps of space exploration.
Ten thousands years ago humans didn't seem close to it either and yet they were same as us (and also same as their ancestors for dozens thousands years). 100,000 years is nothing on evolutionary scales and yet during this time our ancestors managed to outcompete other intelligent specie, Neanderthals and probably caused their demise. Considering what our species did to environment it's likely that as long as humans exist, another intelligent species can't evolve here.
Perhaps a better term than "close to...space exploration" would be "having a syntactic language." Humans of 10k years ago certainly had that, as probably did humans at least 4x that long ago. I think that's a pre-requisite for developing any kind of civilization that will develop technology.
And no, as far as anyone has been able to determine, neither birds, whales, dolphins nor apes have anything like a syntactic language, or even our vocabulary.
The comparison is not just with other animals today but across time. Dinosaurs dominated the planet for 100 million years but do not appear to ever have been as close to space exploration as the humans of 30,000 years ago.
Octopuses have been around for 500 million years. For most of this time humans were not holding back or inhibiting their propensity to study, receive signals from, send messages to, or travel to, other stars.
But it's not qualitatively different from other species' intelligence. It's just a sample from a distribution, and as such, only a matter of time and speciation.
I don't find this argument terribly convincing, especially since it (and apparently all of the author's reasoning[1]) rest upon the unstated assumption that we are randomly distributed over possible observers of the universe. The endpoint of that whole (bs) line of reasoning is that we are all Boltzmann brains[2].
In the end I am only convinced that the authors' main specialty is grabbing headlines.
[1] from browsing a paper he co-authored with Nick Bostrom, offender #1 of bad probabilistic thinking
It took approximately 4.5 billion years for a series of evolutionary transitions resulting in intelligent life to unfold on Earth. In another billion years, the increasing luminosity of the Sun will make Earth uninhabitable for complex life. Intelligence therefore emerged late in Earth's lifetime. Together with the dispersed timing of key evolutionary transitions and plausible priors, one can conclude that the expected transition times likely exceed the lifetime of Earth, perhaps by many orders of magnitude. In turn, this suggests that intelligent life is likely to be exceptionally rare. Arriving at an alternative conclusion would require either exceptionally conservative priors, finding additional instances of evolutionary transitions, or adopting an alternative model that can explain why evolutionary transitions took so long on Earth without appealing to rare stochastic occurrences. The model provides a number of other testable predictions, including that M dwarf stars are uninhabitable, that many biological paradoxes will remain unsolved without allowing for extremely unlikely events, and that, counterintuitively, we might be slightly more likely to find simple life on Mars."
BTW, the first book that extensively wrote about the basic idea is 20 years old:
"Rare Earth: Why Complex Life Is Uncommon in the Universe" 2000, by Peter Ward, a geologist and evolutionary biologist, and Donald E. Brownlee, a cosmologist and astrobiologist.
I've always wondered, given enough time could any species on Earth become "intelligent"? If one day humans all left Earth, then in a million years when we come back to visit, is it possible for Octopus to have made octopus space suit and fly in octopus craft and visit the moon?
I think its possible. I think if humans just helped them a little it make take alot less than a million years. It would be cool for Humanity to just foster civilizations in all species on earth. It would really interesting to see how other species's approach to technology.
It’s possible but far from inevitable without intervention. It seems a confluence of unlikely (and still debated) factors combined to make tool-wielding + symbolic reasoning + language + culture etc an evolutionarily winning strategy. This is sometimes called the cognitive niche. But most species reach an evolutionary local maximum where increased intelligence offers no further survival gains; for example, sharks and crocodiles have been relatively unchanged for millions of years.
I like this term "cognitive niche" a lot. The term "Evolutionary winning strategies" kind of implies an ordering, as if there was only one winner in the grand scheme of things. Humanity may seem like the apex predator on Earth but we live just where we live, in the circumstances we find ourselves in, that our genes have adapted to. In other circumstances, spaces or timescales, other lifeforms prevail. And on a cosmic scale, who knows...
This is called uplifting, and it should be possible to do it in the 21st century by using genetic engineering to give creatures progressively bigger and better brains with each generation.
When a brain is of sufficient capacity for consciousness to emerge, we can begin to educate these sentients, and teach them all we know, leaving them to figure out how they can apply our knowledge to their perspective of the world, which is alien to us.
Octopus for instance may begin to construct tools that will allow for them to practice aquaculture and build more civilized social structures that move them away from hunter-gatherer lifestyles. When they are not farming, they could develop written language to record their history and debts. Surely if you checked back in tens of thousands of years you would find advanced cities and societies as complex as human ones, except entirely underwater with occasional structures breaking above the surface.
Other creatures like chimpanzees could be taught how to work with humans as a cheap form of labor, digging ditches or mining resources.
This article seems to take the wrong stance that evolution is a slow change over extended time in population. The new models of evolution is actually population change happens rapidly in a few generations caused by outside stimuli. The resulting change lasts a long time until new stimuli cause population change. Evolution if graphed is steps instead of a curve.
Did they even address the cause for "intelligence?" As I see it two possible signs of intelligence before documented communications (ie. Pictures and what not) would be simple tools and fire.
It is outside the scope of this paper(maybe), but, I think they did to be able to address if humans today are actually any more intelligent than humans in the past, or human record knowledge is the cause of human advancement today. Also I did not see them define intellgence as it pertains to nonintellgent life.
I sometimes wonder about the odds of the most chilling questions. What are the chances we're the only intelligent life currently in existence? ("We" including other primates, dolphins, etc.) The only intelligent life to have ever existed? The only intelligent life to have ever existed and that will ever exist? Even the first and last instance of any kind of life at all?
For a long time, I thought surely these probabilities must basically be zero, due to the sheer amount of dice that can be rolled (tons of space + tons of time), but after hearing a lot of smart people talk about it, I think all of these things do carry a non-zero possibility.
Of course, we'll probably never know, though. There could be some galaxy clusters teeming with life and visible structures but they could be so incredibly far away from us that they basically don't exist from our perspective, and vice versa.
I'm not so sure. I recall seeing calculations that show that, unless an intelligent species was deliberately sending out very high energy, very well targeted signals, it's really unlikely we'd detect them.
May as well argue about "Civilizations that produce iPhones are rare" - the definition is particular to humans. Monkey-troupe intelligence may indeed be rare, and insectoid emergent reasoning the norm. Or whatever.
The metric they used was the oldest artwork. The table contains a citation to "Pääbo (2014)" in the line where intelligent life forms. Of course, question is, what do you consider as art :). Is a dolphin frolicking in the water performing a piece of art? Our own judgement might be clouded.
Careful with that one. Francine Patterson has been attacked by her "intelligent" peers for all these years because she was able to teach sign language to Koko the gorilla... and since a gorilla obviously cannot be intelligent, she must have faked the reports... or the best one: even though it looked like the gorilla was using the sign language, what was really happening was that it was just imitating the humans for the treats.
Something about saying that animals are intelligent triggers some people, specially the "scientist" types.
There are legitimate issues with Patterson's work that do cast doubt on her results. Things like speaking for Koko or "correcting" for her when it seemed like Koko was signing something nonsensical.
For example, Koko had an apparent fascination with nipples. In front of cameras, Patterson would always say Koko actually meant something else because nipple rhymes with whatever word she's trying to say but in private, according to other caretakers who worked with Koko, Patterson often showed her nipples to Koko almost like a greeting and made other female workers do the same to their discomfort. She would also ask Koko leading questions to get desired responses for cameras which doesn't demonstrate intelligence.
Patterson apparently also spoiled Koko, feeding her things that weren't good for her nutritionally, but went to great lengths to keep Koko to herself, going so far as to keep her separated from the male they brought in to keep Koko company.
So while I would be excited at the prospect of intelligent animals, I think Koko is unfortunately not a good example.
No. As if she was doing the sign language equivalent of putting words in someone's mouth. It's not like viewers would know the difference. But the other caretakers did and they've spoken out about it.
There's no doubt Koko probably understood some things, but not to the complexity that Patterson tried to portray it.
And the thing I was getting at with the nipples was Koko was apparently asking to see people's nipples all the time but in demonstrations Patterson would always play it off like Koko was saying something completely different and more intelligent than it actually was.
Intelligent life could evolve frequently, even within their model, if you consider panspermia (life transmission via rocks between star systems). The infrequent evolutionary events just have to happen once, then get spread all over the place, in the bodies of something like an alien-Tardigrade. Moreover, life could exist off planet. Here is a presentation by Freeman Dyson talking about searching for life in the Kuiper belt (where all the real estate is):
Even if panspermia is happening, that only gets other planets past the first rare transition. We know from the fossil record that the rest of the transitions happened on Earth rather than before Earth was seeded. The other planets would still need to separately make it past all of the other rare transitions to also have intelligent life.
The diverse examples of octopus, dolphins, elephants, parrots and great apes strongly suggests that intelligent life is not particularly rare. However the combination of a species' intelligence and an anatomy that can take advantage of the synergy between intelligence and tool making might be rare.
All fine and well but this tries to draw significant statistical conclusions from a sample of one, and it's unclear if that's even remotely possible or wise. The instant we find a counter example all this nice thinking will have to be trashed.
quick skim of paper, looking at final stats - 4.5Byr out of 5.5Byr planetary habitable timezone looks like a Pareto distribution - it took 80% of the planet's lifespan to evolve intelligent life; leaves me optimistic
It could be that the average amount of time for intelligent life to evolve would be much longer, like 1000x a regular planet's lifespan. Then you would only very rarely have intelligent life actually evolve, and that intelligent life would generally notice that it came into existence near the end of their planet's lifespan, and that simple life happened to get started very near the beginning of their planet's lifespan (or else intelligent life probably wouldn't have had enough time to evolve).
> but we only developed intelligence once it seems.
Depends on where your cutoff point of "intelligence" is, we've seen some form of intelligence evolve at least 3 times in birds, mammals and cephalopods. If it's evolved independently 3 times on earth I'd say it's quite likely elsewhere.
Intelligence has developed in multiple Earth species (see crows, dolphins, etc.)
Intelligence isn't what separates humans from crows. It's our ability to time bind information past our lifetime. We can use oral traditions, or write down what we have learned. And the next generation doesn't have to start from scratch. And thus you get exponential growth in knowledge.
It is complex language that separates us.
As a data point, it is true some crows have taught their nestlings how to use cars to crack shells to get at the tasty tidbits inside, but that learning doesn't seem to have propagated very far.
As much as I like the Drake equation, sometimes I think the big breakdown ought to be "life," "intelligent life," and "intelligent life that thinks communicating with strangers is a good idea," wherein the third phase might be brief -- for one reason or another.
You have an array of hypothetical explanations for the Fermi paradox (mostly drawn from sci-fi. mostly.) to bounce off of all of these estimates and I confess a great curiosity as to which estimates and explanations are true, although it is unlikely that I will ever know.
Still, the silence has tilts me toward the more pessimistic explanations.
This is a good point, often forgotten: imagine if dolfins are infact as smart as humans / cavemen - can you prove otherwise? They can't write or develop technology because they live in water and have no hands.
Perhaps the spontaneous auto assemblage of cell life, and from there, intelligent life is merely time dependent in an absolute sense? In that scenario, all sapient life in the universe evolved at the same time. When we develop the technology to discern communication attempts, so will they. And so will all the others. It will be a Cambrian explosion, simultaneously throughout the universe. Oh happy day!
Tangential to this, but one of the authors, Anders Sandberg, has a great page on transhumanism that I loved reading a long time ago. If anyone is interested:
I think that whatever our expectations are, we should all be prepared to be surprised. We simply don't have enough information to make any conclusions.
The article seems to simply assume the former model ("We assume that once an evolutionary transition is possible (i.e., once the previous transition has occurred), it occurs at a constant average rate λi, so that each ti is exponentially distributed with an expected transition time of βi = 1/λi"), but that feels unjustified to me. Is it really the case that the transition from prokaryote to eukaryote was equally likely at any time, and things simply sat stagnant for a billion years until one day life got lucky?