Several thousand intelligent beings have surrounded two funny looking blue trees. On some planet. Elsewhere. [Image source] Back in the old days, when Carl Sagan was alive and at Harvard, there was an annual (or at least frequent) debate between Sagan and my adviser, Irv DeVore. The debate was about the possibility of intelligent life having evolved on other planets.You already know Sagan’s argument: There are billions and billions of Galaxies, each with billions and billions of stars, so there are billions and billions and billions and billions of stars. Even if the probability of planets forming around a star is low, and of an earth like planet being one of them, and being at the right distance from the star, etc. etc. etc. there are still going to be a very large number of worlds amenable to the origin of life, and some of those, the evolution of complex life, and some of those will give rise to intelligent life, and some of them will ask the same question we are asking now and seek to explore the possibility of life on other planets.Then, I guess we get together in a coffee shop on Alpha Centauri and talk about it.DeVore’s argument went the opposite way. He devalued the probability of intelligent life forming on any given planet by going through all the moments in the long evolutionary history of humans (starting with the origin of life) and pointing out each of the numerous moments in geological time when something went “wrong” and nearly wiped out this particular lineage (and a bunch of other lineages as well). This arguement was done with only limited knowledge of the numerous mass extinctions that we are now aware of, and it was still pretty convincing The probability of intelligent life was very very low anywhere.I’m pretty sure both arguments are convincing, and as has been pointed out, the fact that we have only one test case (the Earth) from which to infer probabilities means that many of the key probabilities are simply made up, and not empirically or even deductively derived.Well, now, Andrew Watson of the University of East Anglia proposes an improved model to consider the chance of intelligent life arising somewhere. One of the major differences between this and earlier models is that we now are starting to believe that there are more planets circling the various stars than previously guessed. Perhaps planets are fairly routine. However, Watson actually estimates the chance of intelligent life forming on other planets as being fairly low because of the necessary evolutionary steps life must, according to him, go through to get intelligent creatures. The probability of each of these transitions … including the origin of unicellular life, multicellular life, specialized cellular structures (organs and such), and human language … is very small, and the amount of time for this to happen in is also very small.You can read a summary of Watson’s argument here at Astrobio.My take on the little I’ve read of Watson’s article is that he’s got a lot of it wrong. There seems to be two different and possibly largely independent things going on in evolution. One is the maintenance of the status quo, which results form stabilizing selection and niche filling, and the other is dramatically quick novelty.For instance, it looks like unicellular life formed very quickly after it was environmentally possible. this is still a guess, but it is not the case that a lifeless but potentially life-supporting earth hung around for billions, or even many hundreds of millions, of years waiting for the right lightning bolt to hit the right mud puddle (that’s a metaphor of course …it may have been deep sea floor vents, whatever). No, it seems to have happened right away.For instance, the shift from there only being single celled life to there being differentiated multi celled forms was very very quick. It is not the case that unicellular life formed colonial life forms that kept almost evolving into jelly fish but never quite did until that one lucky conjuncture of events.For a very long time something (many things?) kept change from happening, then suddenly change happened.(When I say suddenly, I’m speaking in geological terms. This does NOT mean that I think things happened over thousands or millions of years and it looks sudden. It does not mean that I think things were sudden like a century or a year or a month. What it means is that we don’t know, but it was not a billion years. “Quick in geological time” does not mean “slow” it means “crappy resolution, the phenomenon we are observing happened in one temporal unit of our observational framework.”)Well, one basic question one might ask is this: Would life on all planets have these two features? It is possible that the change-making and the stabilizing sets of forces may have a different configuration on on other planets. So, some planets may require several tens of billions of years more than those planets will even exist to have even a few evolutionary things happen, while on other planets, evolutionary change may happen 100 orders of magnitude faster than on Earth. Is Earth slow, fast, or average?Another sort of assumption that is usually made in these models is that life elsewhere would “look” like life on earth. That there would be photosynthesizing plants and heterotorphic animals. Balderdash, I say! The particular configuration of life we have on Earth is in part, possibly large part, a product of the strange and quirky history that this particular planet has undergone. Why not photosynthesizing motile things with neural structures, or highly “intelligent” non-motile organisms anchored to the sea floor near hydrothermal vents?Speaking of neurons, this is my favorite wrench to throw into the works. Neurons. They suck. A given neuron can contain, pretty much, one piece of data, and can have only one output (which can be split to a number of different receiving cells, but they need to be kind of near each other). Neurons only communicate in one direction.Neurons evolved to transmit a small amount of information in one direction at a time in simple organisms that did not have brains.If by chance Neurons had numerous organelles that could each contain lots of data, and could duplicate these organelles before cell division, and/or if what we usually think of as neural information could be coded in a molecule for transport and reproduction (i.e., like storing neural data in a DNA like molecule) and so on and so forth, the structure of information acquisition and use could potentially be very different than it is on Earth.On Earth, intelligence is expensive. Neurons are inefficient and picky, and each organism has to reconstruct its system of managing information fresh from birth. Neural tissue is expensive to operate. In other words, there are all sorts of selective forces working AGAINST intelligence.This is an idea totally lost on most people, even those who are busy being smart asses about the chance of life on other planets. It is NOT the case that there is overwhelming selection FOR intelligence (meaning whatever you think it means, we need not get bogged down here in defining intelligence). No, intelligence is selected for, and it is selected against, but mostly, it is selected against.The concept that intelligence is wonderful and is therefore selected for is a teleological misunderstanding of evolution.But, on some other planet, intelligence might be cheap and generally useful. On some other planet, intelligence could be widespread among whatever sort of freaky alien organisms have evolved there. Watson’s key step … “human language” could be utterly mundane and embarrassingly simplistic and useless by the standards of some other life systems.But this range of possible life systems is usually not considered very important in these models. Human intelligence is often a considered typical, or average end product, just like one needs to consider other aspects of life on Earth average just to get a start on these calculations, for better or worse. But while we may be able to make the argument that replicating molecules (like DNA), photosynthesis or chemosynthesis, or certain other aspect of life may be likely to occur in many different life systems, mammals, brainy things, humans, these are all oddities of this planet and the usual way of getting any kind of memory-tracking, exploratory, “thinking” organ in an organism on earth is absolutely ridiculous.The only thing that I am prepared to assume is this: Somewhere in the Universe, there are intelligent entities that are way ‘smarter’ than humans, but still can’t get this right.
In homage to an inspiration of this post, I provide this link to the secret, generally unseen obituary of Professor Irven Boyd DeVore.
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There is a statistical principle which says that if you have only a single example, you can assume it is near the average of the population. In a normally distributed population (even if more or less) most individuals are near average. Can we stretch this to think that earth is somewhat like the average planet with life? Life as we know it is greatly constrained by physics and chemistry; to the point that I find it difficult to think of life as we don’t know it. For example, I doubt that an organism dependent on photosynthesis could keep enough of an energy stream going to be highly mobile. I can’t picture a technological civilization in an environment where fire is not possible.My fuzzy understanding of big bang theory,etc, suggests that the universe is evolving with time. That there was a long period of time before the elements necessary for life as we know it became present in useful quantities. So a long period of time passed before life as we know it was possible. That suggests that living things first originated somewhere at sometime in the past. As you mentioned, the road to tchnological civilization is mostly pitfalls; and, takes time to traverse, even with fantastic luck. So it is possible we are the first technological civilization in the universe. On the other hand we may be the youngest.There is a George Gaylord Simpson paper; something like “On the nonprevalence of hominoids”, which makes the point that life as we know it, from somewhere else, should be quite different.All very interesting speculation, if not particularly well informed at this point in time.
Jim:Yes, this is my point exactly. We can assume that the earth is average in many respects. But the question at hand is about intelligent life, and intelligent life on the earth is itself so quirky and weird that this is not a case where that assumption would be safe at all. That, I am totally convinced must be true. Beyond that, the interplay between stasis and punctuated change is also in some ways quirky and links to a number of contingencies, such as linear inheritance of a relatively simple molecule, the earthy version of species and individuality, continents moving about on a sea bed, an ocean, and whatever aspects of cosmology of our solar system result in the particular pattern of impacts.So I’m not sure of stasis/rapid change patterns should be considered typical or not.As I mention above, it is reasonable to figure that some things woudl be typical … photo or chemo synthesis has to be happening. Indeed, most of the biomass of the planet earth is based on a chemosynthetic system, and a smaller part of the biomass, the part that includes “intelligent” life, is based on photosynthesis. Does that mean anything?My guess is that across the universe there is more chemosynthetic life than photosynthetic life.Your big bang thinking here may be a bit off if you are talking about the earth specifically. All of the elements needed for life existed way, way before the earth formed.The Universe is about 14 billion years old, stars started forming right at the beginning of that time, and then produced the various elements. So all the elements were in place really near the beginning of that.DeVore’s argument derives directly from when DeVore was a junior instructor rubbing elbows with George Gaylord Simpson!
I should ad this: The oldest known planet is believed to be about 12.7 billion years old.
I found your arguments interesting and the reasoning coherent. A good read and gave me a new perspective to consider.
Very good points to remember about the evolution of intelligence and its human tools (here, neurons). Would your (Greg’s) argument point to the feature of intelligence (as well as perhaps other “major” features, however defined) evolving by drift rather than natural selection?I’m not sure whether I ever introduced myself here, though I’ve been reading for a while. I’m a musicologist, but work currently on the intersection of music research and biology in the late nineteenth century. Additionally, I have a weakness for the natural sciences, as well as all kinds of ales and wines.Cheers, Ben
I concur with you on the Watson paper. Very much in the anthropic/rare earth corner. As long as we are restricted to the single sample of terrestrial life, all theories are equally (in)valid.
Since we’ve never been visited by aliens and SETI has never gotten anywhere, one assumption that we can make is that technology must be pretty damn rare in the universe regardless of how prevalent intelligence is. A Star Trek universe where various species are at more or less the same level of development that we are seems wildly improbable. It was Arthur C. Clarke who pointed out that once we start exploring, “we’ll find apes or angels, but never men”.
Romeo, as a math geek, I think that’s better evidence that we live in an awfully big universe. I mean, even if every star had planets, on a galactic scale, planets would still be very rare (i.e., lots more places where they weren’t than where they were). The power that would be required to broadcast broadly above the background noise over interstellar distances and the time required for such a broadcast to reach the next planetary system, much less us, make it hugely unlikely that SETI will ever pick up what it’s looking for even if it’s relatively close.But that isn’t the same as measuring how rare technology is if we limit our sampling to planetary systems. That’s why most science fiction involving aliens assumes (sometimes very quietly) that someone has solved the speed of light problem. It’s the only way to make the premise remotely plausible.Speaking of assumptions, Clarke assumes that an intelligent species will want to push on to angelhood. Based on the current political climate, I’m not sure that’s valid.
Adding absolutely nothing to the argument but wasn’t Sagan at Cornell?
Again, fuzzy memory. It is my impression that it took several episodes of stellar evolution before all the necessary elements were formed. Perhaps as much time as half the age of the universe?Hal Clements wrote a number of fairly well thought out science fiction stories about creatures who had evolved on not exactly earth-like planets and their interaction with humans. So far as the technology goes, I recall one science fiction story where the aliens landed. They were polite to us, but they were really here to visit the dolphins.
Jim, you know, this whole origin of the elements thing is kind of tricky. My understanding is that the heaviest natural elements (which have a radioactive decay and must have been formed after the not as heavy elements such as C) were being formed 12 mya.
While a neuron may only have a single output (pulse or no-pulse), there is time/rate coding, consideration of whether the neuron is inhibitory or excitatory, and the weighting/number of synaptic connections between a given pair of neurons. I don’t have my neurobiology book in front of me, but there are even some neurons with axons that run most of the way across the brain.Also, each neuron acts as a weighted integrator when it comes to its firing rate. How many excitatory and inhibitory inputs is it getting, what are their weights, and how often is it getting them? The complexity of the interconnections grows very quickly.There are even neurons where information transmission is a product of the lack of firing. The retinal ganglion do this, I believe. There “normal” mode is one where they spike at a relatively monotonic rate and when they “see” light, that transmission is inhibited. This is to raise the noise floor since neurons will fire intermittently even in the absence of stimulation. If the retinal ganglion were excitatory-only, you’d see random flashes of light all the time.It’s also not really true that “each organism has to reconstruct its system of managing information fresh from birth”. There are many static information management structures in the human brain and in brains all the way down to the common housefly (and below, in all likelihood (whatever below means … )).Your visual cortex is a good example. Everyone on the planet, unless they’ve had some sort of brain damage and gone through neural remapping, has the part of their brain that deals with extracting the angle of an object in their visual field in the same place. Ditto for phase discrimination in the auditory cortex so you can determine the direction a sound is coming from. Ditto for thousands of other “prebuilt” processing structures in the brain.I am admittedly no expert in the field, but some of the books I’ve read (check Spikes: Exploring the Neural Code and The Computational Brain) even suggest the information content per spike is damned near the Shannon limit in efficiency.I guess my main issue is your conclusion. In what ways is intelligence mostly selected against? At a base level, being able to figure out where your predators are sneaking up on you, where your prey is hiding, where there’s a good mating opportunity, all seem to be highly selective towards intelligence (intelligence here not meaning just self-reflective consciousness, but the entire gamut of behaviors that neural tissue is responsible for).As to “high” intelligence, I don’t see that evolving in your non-motile thermal vent creature. Where’s the selective pressure for it? Now, a motile, photosynthesizing intelligent creature I can see, but only if there was some sort of predator/prey relationship pushing it along.On second thought, I guess my main problem is pinning down the definition of intelligence. I suppose when we ask about “intelligent life” in the universe, we’re talking about human-level+. I guess I don’t see that huge of a leap from chimpanzees to us. I see it more as an incremental change that took us (humans, for all you aliens reading this) over an intelligence tipping point where we’ve built up language, tools, and survival techniques over tens of thousands of years to where we’ve reached something of a technological tipping point in the last hundred years or so.
As to intelligence, it really depends on how you define it. If you try to define it anthropocentrically, it is rare, since we’re the only example on Earth. But it you define it more broadly, as I think you should, intelligence is actually quite common on Earth. It is certainly common among the “higher” animals, including both mammals and birds. It is present at some level in virtually every living thing bigger than a bug. Of course they don’t all have spoken languages or use computers, but they have to process information and take actions, and that requires intelligence. There may be only one species of life on Earth that is intelligent enough to build space ships, but intelligence itself is pretty common here.
I don’t think the plant-like autotrophs and moving heterotrophs scenario would be particularly unique to Earth. Motility is liable to be somewhat expensive, so if you need not move to receive your energy, you are bound to be somewhat sessile, and that fits autotrophs to a T.I’ve been reading The Living Cosmos, and it’s a pretty good tour of life on planets, life on this planet, etc.One thing I found pretty interesting was the discussion of what happened to Earth after photosynthesis started. Now, I don’t know how accepted this particular interpretation (Snowball Earth) is, but they make a fairly compelling case that the production of oxygen from carbon dioxide caused a major temperature crash lasting until not all that long before the Cambrian, in geological terms.Heterotrophs returning carbon dioxide and other greenhouse gases to the atmosphere would have helped reverse that, making the Earth more habitable and opening the way for the Cambrian explosion.*grin* Your complaints about neurons are not totally founded 🙂 They are not bit-holders! The inputs and outputs average 10,000, which is nonetheless a small portion of the other neurons in range.Sensory neurons are unidirectional, as are motor neurons, but other neural populations have inhibitory and excitatory neurons, and can feedback in loops. Feedback with a gain of 1.0 or more can produce pulses spontaneously once started. There is a constant but shifting background pattern and learning forms deviations, which also shift. You can smell vanilla, and the smell of vanilla a week later will be a totally different 2-D voltage pattern.One thing that it seemed they were finding out in the early 2000s was that there is no directed “lookup” stage – the brain does not, for example, take the olfactory input and compare it with a bank of learned scents – the learning “basins” in the pattern are enough to make the association.Yeah, that’s a lot of jargon, but the source book (Mitchell’s) is even thicker on the jargon :)I would agree that intelligence is by and large not selected for.One interesting SciAm article I remember reading was one about howler monkeys versus spider monkeys. Howler monkeys have an enlarged cecum (analogous to our appendix area, I believe), which is kept alkaline and ferments the leaves that the howler monkeys eat. Howler monkeys do not have particularly large brains.Spider monkeys, on the other hand, eat fruit, and they cannot ferment mature leaves like howlers can. When food supplies are low, they can survive off young leaves, and their digestive tracts respond to the fiber by moving things along faster (young leaves give up their scant nutrients fairly quickly, so moving things along allows more leaves to be eaten – it’s an interesting possible take on the human reaction to fiber).In the forest, edible fruit-bearing trees are fairly few and far between. Spider monkeys can generally remember where the trees are when they find them, as well as remember how recently they visited and when the fruits are in season. Spider monkey brains are about double the size of those of howler monkeys. That gives one possible indication of the sorts of situation where intelligence is rewarded.Technology could very well be rare. We could also just be out of the loop communication-wise because electromagnetic communication might just suck compared to other alternatives that we have yet to discover. It could be somewhat like being on a desert island without a radio.Or we could just be alone in the universe!Ah, I miss Carl Sagan. Neil DeGrasse Tyson and other potential heirs to the “throne” are just lacking… something. I’m not sure what it is, but it’s more than just saying “yumans” :)Anyhow, that’s enough blether from me for now 🙂
I wonder if there could be a platypus on another planet. Maybe a naked mole rat…I understand that people are interested in intelligence because they want companionship that they can’t find within there own community, planet, galaxy, whatever, but aren’t there more important questions regarding life on other planets?What is life on other planets likely to be like? Is it going to be carbon based, oxygen breathing, DNA coded? It seems to me that the primordial soup of another planet is probably much different than it was on earth. I suspect that if we find life on another planet it will be gold-based or maybe silver… something that we have to conquer and kill anyway, would the human race have it any other way?
This is one of those discussions where you can speculate your ass off because the real benchmarks are unknown. Tailor-made for the internet. Speculative blabbing out the wazoo!I have read Michio Kaku’s idea on this and he refers to earlier works that tried to (speculatively, of course) rate a civilization by the level of energy it could harness.Is the civilization limited to fossil fuels? Can it harness the energy of the local planet? Can it harness the energy of a star? Can it harness the energy of a galaxy? These would be used as benchmarks for measuring the advancement of civilizations.He also makes the interesting analogy arguing that we could be surrounded by more advanced civilizations and not know it. The example is of an ant colony living near a freeway. The freeway users would not know (and most probably not care) there was an ant colony 50 yards from the freeway. The ants of course, know nothing about human society. But there they are, two societies living so close they could touch each other, each oblivious to the existence of the other.Another interesting thing to speculate on is that on earth at least, the evolutionary time scales have gotten smaller as the more intelligent animals have arisen. Single celled life and small multicellular organisms existed for hundreds of millions of years, so and on. Humans evolved in a very short period of time, and perhaps our particular form – Homo Sapiens – will not last more than a few million years at most before we evolve into something else.So that brings us the idea that it may take a long time for life to evolve to a certain level, but at a critical point, the timescales that it takes to evolve newer, more intelligent organisms starts shrinking exponentially.It might take 4 billion years to evolve the first form with a recognizable intelligent responses and some kind of multi-lobed brain.. But then things start happening much faster.Once an organism understands it’s genetic makeup, then theoretically it can start evolving itself, which would again shrink exponentially the time it takes to evolve the more intelligent life forms.What if, after 5 billion years, an organism that understands how to evolve organisms is arrived at? Theoretically, there would be at least 5 billion more years to tinker – on purpose – with evolving new, stronger, more adaptive, more intelligent lifeforms.At that point, if they could figure out how to survive the death of their local star, they would become a true interplanetary intelligent species.I think it’s not so improbable when you throw in this idea that the evolution happens faster and faster as you climb up the intelligence scale.Five billion years is a LOT of tinkering time for an intelligent species that knows how to manipulate genetics and how to harness various energy sources.No doubt if one of us ever got off our “anthill” and realized we were surrounded by superhighways, such beings could easily appear Godlike to our simple brains.
Saying intelligence is not selected for is like saying locomotion is not selected for. If you define intelligence narrowly enough (or anthropocentrically enough), then it might be true, but it begs the question.
A lot of interesting comments are developing here, but I’m only going to address one now: That of “intelligence” being selected for/selected against.Please not that I never said that intelligence is not selected for. Or if I did, I did not mean it. I did, say, however, that it is selected against. And this is true.There are no adaptations that lack a cost. The cost is what makes a particular adaptation selected against, the benefit is what makes it selected for. This is pretty basic.My main argument here is that neural structures are a) expensive and troublesome in a number of ways, and thus have costs. The benefits do not come without these costs; and b) the way neural systems happen to work on earth can be argued to be more costly than they have to be. This can be said of virtually any adaptation, of course. My argument, though, is that since neurons were initially shaped by selection under conditions where quantity and complexity was not a big issue, and that intelligence requires quantity, by chance, neurons as a way of processing and storing information in quantity and in complex systems may be especially costly.
Perhaps intelligence is not a good thing from an evolutionary point of view. I think there are many examples of why this wouldn’t be desirable trait in a species in terms of survival. We can have a nice saber-tooth tiger sandwich, but at what cost? Nightmares and delusions and superstitions and the ability to destroy the earth with the things we create? Things like evil aren’t scientific in nature, they are bad trait of intelligence. The fish in the ocean aren’t threatened by destruction from evil fish, in the same way we all live on the brink of destruction by an evil intelligent person with their finger on the button.
Life as we know it is based on the unique properties of the C atom and H2O. There is no other atom which has the “life-giving” (hate that term!) properties of C. There is also no other compound which has the unique properties of water. So I find it hard to picture life which is not C and H2O based. I leave this to others who know more about the subject than I do.If there are advanced beings in the universe, who understand physics as we don’t know it, and are thus capable of interstellar travel on a practical basis, I hope the evolution toward angels is right. If so, and they are aware of us, they are leaving us strictly alone. They are waiting for us to come to them. The history of contact between more and less technologically advanced human populations clearly demonstrates that such contact is not a good thing for the less technologically advanced group.
“The Universe is about 14 billion years old, stars started forming right at the beginning of that time, and then produced the various elements. So all the elements were in place really near the beginning of that.”Are you sure about that? The abundance on a planet of heavy elements needed to sustain life requires that they be created in a supernova, and then that a new star be formed. That takes some time, doesn’t it?
Nimonnet: Yes, it does take time, and as far as I can tell, there is a certain amount of disagreement on how much time, or what the timing of key early events was.