Me four years ago: Imagine that over the entire past and future history of our galaxy, human-level life would be expected to arise spontaneously on about one hundred planets. At least it would if those planets were not disturbed by outsiders. Imagine also that, once life on a planet reaches a human level, it is likely to quickly (e.g., within a million years) expand to permanently colonize the galaxy. And imagine life rarely crosses between galaxies. In this case we should expect Earth to be one of the first few habitable planets created, since otherwise Earth would likely have already been colonized by outsiders. In fact, we should expect Earth to sit near the one percentile rank in the galactic time distribution of habitable planets – only ~1% of such planets would form earlier. …
"Properly understood, evolutionary pressure refers to the increase in a population of genetic traits that mitigate environmental threats"
That is a secondary effect, evolution only responds to "environmental threats" by how much it affects the ability of that organism to reproduce. Evolution is just the almost tautological observation that those that are better at reproducing become more numerous over time. There is a common myth that "removing environmental threats stops evolution", which is pure nonsense, it only shifts selection from survival traits to raw fertility. Modern living seems to neutralize some reproductive instincts in the present breed of humans but this will not be permanent over time humans will evolve genetic adaptations to modern living just as they did to farming etc, and like all life forms reproduce exponentially until they have filled the available habitat if we get something like fusion rockets then that could be the resources of the entire solar system, turn all the minerals in asteroids into cartwheel habitats. Before the solar system is totally mined out it would make sense for habitats to migrate to other solar systems as they will all be descended from those who had the strongest drive to reproduce of each generation.
If robots take over and wipe out organic life its just the same thing the robots that make the most copies of themselves become more numerous over time.
As we have no idea how hard the filters are to cross we dont know how many filters are needed. Could be a single trillion to one filter. Maybe the creation of the first cell and genetic replicator, it involves several components coming together. There could be a lot of lifeless, sterile yet potentially fertile and Earth like worlds out there just waiting for us to seed them.
We are the Firstborn! So exciting!
The only alternative would be if it was possible for many aliens to exist without at least one of them becoming an exponential interstellar replicator. Even a single such organism would very quickly take over all available resources, just as a single bacterium is capable of quickly using up all available media in a ridiculously short time. We can already envision the technologies needed to become interstellar replicators, capable of spreading at a substantial fraction of c, without postulating any new physics. If there were aliens, they would have the physical ability to visibly settle the universe. Since they are not visible, either they don't exist, or else there is some universal non-physical (i.e. social) stricture that prevents, over billions of years and millions of solar systems, the emergence of exponential replicators. I feel it is highly implausible that such anti-exponential social law exists, although it is not completely impossible.
So, yes, most likely we are the Firstborn. Let's build the laser launchers for our von Neumann probes soon, before something bad happens to us.
pre-planning has nothing to do with it. If cognitive capability were *generally* an advantage, then *any* increase would get selected for. "some minimum level" is there from the get go in any organism that discriminates, including microbes. It is because being a better discriminator is not *per se* an evolutionary advantage that the dominant organisms on this planet are unicellular.
" So what are the odds all this complexity would arise in the first place? Very very low I would say."
This a Creationist argument. The odds are very high, *given enough time*; that's how probability works. Complexity arises inexorably in evolution, for the same reason that a bunch of computer cables inexorably become more entangled over time, and stirring cream into coffee mixes them and never unmixes them ... because tangling happens more readily than untangling. But while more intelligence requires more complexity, more complexity alone does not imply more intelligence. And the word "more" there is important; you are treating it like a binary attribute. Of course, there are gates, like harnessing fire and learning to make ever more effective tools, but those are cultural, and culture evolves far more rapidly than biology.
"Robert Koslover specifically mentioned a filter between smart and civilized animals."
No he didn't, Robin Hanson did ... but a) "a filter" is a ridiculous way to talk about such evolutionary paths and b) neither that nor anything else you wrote has any bearing on what I wrote.
P.S. Velociraptors didn't *make* tools, for obvious reasons. For the same reasons, dolphins will never build villages or develop agriculture. Humans, OTOH, were a social species with upright posture and opposable thumbs *before* their brains started to increase in size significantly (see, e.g., https://en.wikipedia.org/wi.... It was a very unusual set of chance circumstances that produced human-level cognition.
Robert Koslover specifically mentioned a filter between smart and civilized animals. Smart animals are rare, but did evolve indepently several times and these animals do use tools (perhaps velocitaptors did too, we'll never know).
No, that's not the question. There weren't ever any dinosaurs "smart" enough to produce civilization because, again, it is not the case that "cognitive capability is generally an evolutionary advantage". And so it will be on most planets with life ... ecologies lasting hundreds of millions of years without giving rise to tool users.
This is circular, since you *assumed* a steadily increasing population. Of course increasing populations imply expanding in area, but it's the claim that there is "pressure" to increase population that needs substantiation.
How do you know there were no earlier civilizations here on earth? An very advanced civilization earlier civilization we would see traces off, but it's perfectly possible that many species before us developed hunter-gatherer level civilizations before, and just vanished without a trace.
I don't get the "evolutionary" modifier either. But assuming steadily increasing population requiring steadily increasing resources, this seems to imply over the long term an inexorable pressure to expand (one can only milk so much from a given volume of space).
If any ET kills all other possible ETs, we could be only the first one. (And we will kill all other civilizations). It also explains why we are relatively early from all possible planets. ( first 10 per cent). It is the same as we are the first and only life on Earth, and the only intelligent beings ( we killed Neanderthals).
The question is: were there ever such "smart" dinosaurs? Where smart means as smart as a dolphin, whale or great ape (all of which have existed for much less 150 million years), and if so, for how much of that 150 million years did they exist (the highly specialized theropod dinosaurs who were probably the most intelligent dinosaurs mostly existed near the end of those 150 million years)?
0) what a cool paper to have written - thanks to the authors and to you for the pointer!1) the 8% upper bound is very interesting, but that concerns the currently-visible Hubble volume; and as noted in the last paragraph of 4.1, most of *that* region's planet formation (thus presumably most of its civilizations) will be unobservable to us by the time they occur. As a practical matter wouldn't it be even *more* interesting to calculate the analogous upper bound for *that portion of spacetime potentially observable by us*?2) When I try to confirm Eq (2) I lose a factor of N. Can someone confirm or (more likely) debug my derivation? a) applying Bayes Theorem, P(N|f,E=1) = P(E=1|f,N) * P(N)/P(f,E=1); b) the RHS denominator=1 by assumption so we need only evaluate the 1st factor in the RHS numerator; c) if each of the other (N-1) civilization-spawning planets falls in that fraction f of planets which haven't yet formed (this has probability f^(N-1)), then E=1 definitely; but d) E=1 could also occur if some of the N-1 planets *have* formed but *haven't* yet spawned their respective civilizations; *but* e) if we assume civilization gestation time is small relative to the overall timespan of 100BY-1TY this doesn't affect the answer much and we have P(N|f,E=1) ~ f^(N-1) P(N).3) As a bonus I saw the spiffy diagram in Wikipedia which makes graphical sense of Bayes Theorem - check it out.4) As a double bonus, thanks to that diagram remembering the formula is now as ez as 1-2-3 (actually, easier): 1: P(A|B)P(B) = P(B|A)P(A) is both ez to remember and obviously true (since LHS and RHS each equal P(A AND B)), right? 2: divide both sides by P(B) and you're done!
On top of that, human industrial civilization will likely end within the next two hundred years, and a reoccurrence won't be possible due to resource depletion.
You don't seem to have understood a word that Robert wrote.
Dinosaurs lived for 150 MYA without producing civilization or even tool users. Why not? because evolution does not generally favor such traits. Humans are a fluke.
The most widespread misunderstanding of evolution is that it is directed and that humans are at "the pinnacle" and that cognitive capability is generally an evolutionary advantage. This is completely wrongheaded, but widely believed ... a sad statement about the state of biological education.
There is no "evolutionary pressure to expand". Evolution is simply the change in allele frequency in a population over time. The pressures on populations come from the environment, not evolution. Properly understood, evolutionary pressure refers to the increase in a population of genetic traits that mitigate environmental threats; it is pressure on allele distribution. "evolutionary pressure to expand" is a category mistake.
Populations expand when there're nothing to prevent them from doing so, but that's rare. Most populations are contained, not expansive.
"Imagine also that, once life on a planet reaches a human level, it is likely to quickly (e.g., within a million years) expand to permanently colonize the galaxy."
Imagine all you want, but there's no rational basis for this expectation. On the contrary, physical limitations make this extremely implausible.