Inspired by the ET strong AI thread: what is the likelihood intelligent life evolved outside of Earth? For that matter, what is the likelihood that human-like intelligence could evolve again after humans are hypothetically wiped out of this planet?
Complex life is rare. Is human-like levels of intelligence an evolutionary flash in the pan?
We have no idea about the first part. As for the second, given enough time, I don’t see why not.
We don’t know that. On earth, it’s everywhere.
I suspect any ETs would have intelligence that differs from ours in significant aspects. It would be odd if H. sapiens like intelligence evolved on another planet. Of course, playing Devil’s Advocate here, we have seen remarkable examples of convergent evolution on this planet.
There is simply not enough data to give us an idea.
It is possible that replicating molecules are common given there is nothing especially rare about rock, water and nitrogen in the universe.
The question becomes, how frequently can self replicating molecules evolve into structures that allow multiple units to join together and replicate consistently - like cells.
Then you need data to determine how ofter these structures (please just let me call them cells) evolve into multicellular organisms.
Complex intelligence isn’t required to be a successful species but it does appear to convey some sort of advantage. But again what specific environmental pressures drive it to emerge as a evolutionary response? I don’t think we know.
We can guess and argue but until we have some more data we have to say we don’t know.
Sorry if this is naive, I confess to not really understanding evolution, but I thought “specific environemental pressures” could provide an ADVANTAGE (or disadvantage) to intelligence, but the emergence itself is purely accidental (mutation.) Once the mutation has occurred, then environmental pressures come into play. Am I misunderstanding the process?
Well I guess I was trying to say unless the selection pressure exists you wont have the spread of the feature into the general population. In other words, some members of the species have the mutation which allows for a big brain, but there is no selection pressure to make that an advantage. Since it conveys no advantage it may or may not remain in the gene pool. I will admit I could be wrong in how I’m conceiving how it works.
I certainly agree the the selection pressures have to be very specific to select for intelligence. On a theoretical level, I can see how intelligent individuals in a species may have the ability to adapt faster to changing environments. But then compare the current fates of two arguably intelligent species: the brown rat and the common chimpanzee. The chimp, despite having fairly high levels of intelligence in the animal world, is by many measures not a success compared to the common rat, which has spread throughout the world.
Of course, sexual selection may explain intelligence, but that wouldn’t that suggest that human intelligence was the result of very specific selection forces that may not likely be replicated elsewhere?
I’ll take a mild leap of faith and hypothesize that the likelihood is near 100%. I only say near since there is currently no way for us to verify this. We are finding more earth-like exo planets all the time as our technology improves. Additionally, we are finding that complex life and ecosystems can exist in conditions and upon bases that we never even imagined of just a few decades ago. When you combine this with unimaginably vast number of galaxies and planets that universe must contain, it is sensible to assume that life, and intelligent life has and will continue to arise in other areas of the universe. I do not believe that life is a special event, and science is rapidly demolishing the idea that it was a very unlikely event. Intelligent life seems so far to be a one-time event of our own planet; but here again science is pushing the boundaries of our original thought. Recent discoveries are indicating that most animals share a form of sentience and self-awareness. It may well be that there may have been primitive self-aware life before on our planet but the traces of it have long disappeared. Human tool use and complex building certainly seems to be a unique event, though nothing I can conceive of means that this must be unique among the universe.
C K Dexter Haven: That’s generally the right idea. If a random mutation happens to be better-suited for the environment, then that organism will survive better than its competitors. What counts as an environmental pressure can be pretty much anything and everything.
As for the question at hand: Given how huge the universe is, I’d imagine the evolution of intelligence has got to be extremely common. But you have to take into account what “common” means.
We use standard candles in astronomy all the time (they help us dictate distance to faraway objects), and good sources are exploding stars. However, the kind of stars we refer to maybe happen once every 100 years in a given galaxy. That seems absurdly rare. And yet if you were to zoom in on the spot formed by holding a dime up to the sky, there would be 100,000 galaxies or so; which means on any given night, you’ll see around 10 stars explode in just that one tiny section. This is what we see empirically.
Now when you consider how many “dimes” you could hold up to the sky, that number is huge. The point: “Rare” events happen all the time.
If you wish to intuit just how big our universe is: The Known Universe by AMNH - YouTube
Life formed on this planet because conditions were ripe for it. We have a very stable orbit and we had conditions that ultimately gave rise to abiogenetic events (self-replicating molecules) which formed cells and, over billions of years, multicellular life and eventually intelligent life.
We’re made of the most common stuff in the universe, too, with a direct one-to-one mapping (hydrogen, nitrogen, oxygen, carbon, etc). Given how many galaxies there are, and how many stars exist, and thus how many planets are out there, a huge number of those are going to have stable orbits. It’s hard to imagine abiogenetic events NOT occurring at least a few times on all those planets.
Intelligent life is another question. I have no idea how common it is but I think it’s probably very common. However, the dinosaurs seemed to have supreme reign over our planet until they all died out (a rather unfortunate environmental pressure on their end) and allowed for a “shock” away from that local optima so that other creatures could continue to evolve and, well, not get eaten/outclassed.
It might be hard to imagine to you, but like everybody else, you just don’t know one way or the other because you don’t have any clue about the likelihood of life appearing. Let alone sentient life.
How comes Drake equationhasn’t been mentioned?
Well, we do have some clue of the likelihood in the sense that we know our evolution is largely resultant of certain characteristics of our planet (as Neil deGrasse Tyson says, we are connected to each other biologically, to the earth chemically, and to the rest of the universe atomically). Our universe is overflowing with variety when it comes to shapes, sizes, and characteristics of different stars/planets/systems to the point where you’re going to have a very hard time arguing that Earth-like conditions are rare. Heck, even here in our own humble galaxy, we find plenty of such planets to exist.
I find it extremely arrogant to even entertain the idea that somehow there isn’t intelligent life on other worlds.
It’s hardly arrogant to defer a conclusion when you have no evidence. You can’t think with your gut.
Given the size of the Universe, I would consider it a mathematical certainty that Intelligent life has evolved on more than one world.
How many worlds, how distant they are and how long ago they evolved is a quite different story, about which we can only speculate.
Humility aside, the fact that technical intelligence appears to have evolved only once (and rather late in the timeline of life on this planet) is intriguing. Arrogant or not, the facts don’t appear to suggest that intelligence has been a particularly common trait that has been selected for in nature.
Although certain aspects of intelligence would probably be different among ETs, some features of our intelligence would appear to have broad application.
A technological species will almost certainly be a social species of some form or another, simply because of the difficulty of manufacturing complex technologies without specialization and cooperation.
A social species may be immutably hierarchical (e.g., ants), and that could lead to a very different intelligence–one lacking, for example, concepts of fairness and justice and empathy. If it’s not immutably hierarchical, though, there will be a conflict between the individual and the society: what’s good for the individual won’t always be what’s good for the society, and vice versa. The maximum spread of genes will probably occur among creatures that have intellectual tools to balance individual good with social good. Too strongly individualistic, and the society rejects you (or it crumbles); too strongly social, and the more individualistic critters will take advantage of you, leading to your genes not spreading as well.
Fairness, empathy, justice, etc., or at least some analog of these concepts, is likely to be found amongst any social species that lacks immutable hierarchies.
Language is something we’re likely to find, too, by which I mean an ability to order concepts in a syntax with theoretically infinite variations, as well as the ability to assign new signifiers to new concepts. Because of the necessity of complex language for creating complex structures or technologies, it’s likely the alien society would prize critters with greater facility at using language.
We do have some clue about the likelihood of life appearing. If something is very unlikely, you can expect it to take a very long time to come about, whereas if it’s likely you would expect it to come about fairly quickly. You’d expect to sit there rolling dice for a lot longer if you were waiting for ten “12s” to show up in sequence than if you were just waiting for a few “7’s.”
On geological timescales, once conditions were suitable for it life arose in the blink of an eye. The Earth developed a solid crust around 4 billion years ago, and the first cells appeared between 3.9 and 3.5 billion years ago. It didn’t take untold billions of years, it happened almost instantly.
Of course, it’s also possible that it was a highly improbable event and we were just the one in a billion case where it happened quickly. But it’s more likely that life arising just isn’t that difficult. Granted, it took a few billion years for multicellular life to take off, so maybe intelligent life is highly improbable. But life itself doesn’t seem very picky to me.
I think this is an important point. The planet is full of intelligent animals, but only one of them rose to the level of technological civilization. There doesn’t appear to be any particularly strong selection bias that would push a species towards our level of intelligence. There are plenty of species that have been remarkably successful and which have been around a lot longer than us without gaining in intelligence at all.
So we have a sample set of one - us. But we have millions of other species that have survived without becoming intelligent. And it’s easy to believe that, had the dinosaurs not been wiped out, we wouldn’t be here either.
So how likely is it that a planet that develops life will develop the kind of life that will lead to the characteristics that would create a technological civilization and a desire to explore the stars? One in a million? One in a billion? One in a trillion? No one knows.
My guess is that life in the universe is common, but that technological, spacefaring life is incredibly rare. Now, given the vastness of the universe, that means it’s probably still close to inevitable that there are other intelligent civilizations out there. But if you narrow the sphere of observation to those stars close enough that we could feasibly detect a civilization or be affected by its self-replicating probes, the number of candidate stars drops down to a small enough number that it just may be very unlikely for us to find another intelligent species.
What, you’re speaking in the present tense? Remember, there has been life on this world for at least two billion years, and no intelligent life for all but the most recent infinitesimal fraction of that. Any intelligent ETs visiting Earth at practically any time past, seeing only a momentary snapshot of the evolutionary history of Earth’s biosphere, would have concluded, “Nope! No intelligent life on this planet! Who knows if there ever will be?” And probably there never would be, until long after their own species had gone extinct. And that applies to any other life-bearing planet in the universe that we might explore. It’s amazing how many people simply ignore the time-scale factor here.
See this discussion of the Fermi paradox (“Where is everybody?!” – i.e., if intelligent life exists elswhere in the universe why has it not contacted us yet?):
I think we also need to take into account that intelligent life, as we know it, typically requires heavier elements and stable planet formations for events to take place. This wasn’t around until the heavier elements were cooked in those stars that went nova.
