This episode is also on Bilibili too.
In this first episode where I actually show my face, let’s talk about the “psychological explanation of the Fermi paradox.” Anyone who likes science fiction or topics like aliens and astronomy will be familiar with the term Fermi paradox, but let me explain it briefly. The Fermi paradox says that, on the one hand, the universe is clearly enormous, so in theory the probability of advanced extraterrestrial civilizations existing should also be huge. But on the other hand, we have never actually found any aliens. The universe is so big, yet so quiet. There is a huge contradiction between these two facts, and that is the Fermi paradox.
Why does the Fermi paradox exist? Why can’t we find aliens? This isn’t a question where only physicists and cosmologists get a say. Psychologists, believe it or not, have something to say too.
Today I’ll organize some psychologically interesting explanations of the Fermi paradox and chat about them with you.
The material mainly comes from two books. The first is Where Is Everybody? Seventy-Five Solutions to the Fermi Paradox, written by British astronomer Stephen Webb. You can tell from the title that it’s practically an encyclopedia of the Fermi paradox. It covers almost every explanation of the paradox you can find on the market, from the downright absurd, to the wildly imaginative, to the highly scientific. But for some reason, this excellent book is very obscure. Even though aliens have been such a hot topic over the past year or two, hardly anyone seems to mention it. In a moment I’ll talk about several of the book’s most intriguing psychological explanations.
The second book we’ll be discussing today is a classic of psychology, an early landmark work by the world’s most famous psychologist, Steven Pinker: How the Mind Works.
One important, and quite plausible, explanation of the Fermi paradox goes like this: the reason there are no advanced extraterrestrial civilizations is that intelligence at the human level is extremely rare. The evolution of human intelligence was an extraordinarily unlikely accident—so unlikely that it may be unique in the entire universe. So perhaps there simply aren’t any aliens in the universe about as intelligent as we are. In Where Is Everybody?, the explanation is a little vague. But How the Mind Works happens to contain a chapter that analyzes in detail which accidental factors had to come together for our human ancestors to evolve intelligence. That section is almost an expanded explanation of the idea I just mentioned.
So, read together, these two books give us a fairly complete picture of the psychological explanation of the Fermi paradox.
All right, the main feature starts now. We’ll go through these psychologically interesting explanations of the Fermi paradox one by one.
The first explanation is that aliens have a different mathematical system from ours—and their mathematical system may not be suitable for developing a technological civilization.
This explanation is pretty counterintuitive. We often hear that mathematics is the universal language of the universe. Mathematical laws should be exactly the same everywhere in the universe, so how can we say that aliens have a different mathematical system? Could alien mathematics really be as mutually unintelligible with Earth mathematics as Chinese and English?
Actually, yes, that’s possible.
Some mathematicians and psychologists believe that mathematics isn’t entirely an objective thing. To some extent, mathematics is an invention of the human mind. Whatever characteristics human thinking has, the mathematics we invent will have corresponding characteristics.
The most important characteristic here is probably that the kind of mathematics we invented is based on the concept of “integers.” In our mathematics, we started with 1234567, and only then came everything else. In our mathematics, everything is built on numbers that can be counted.
The reason we invented this kind of mathematics has to be found in the evolutionary history of our ancestors. Our ancestors lived in a world full of discrete objects. By discrete objects, I mean things that can be counted one by one: how many fruits are on a tree, how many antelopes are in the distance, how many people are in our tribe. These things that mattered to our ancestors’ survival were all integers, all countable. Counting them was crucial to staying alive. So the human brain gradually evolved the ability to count. Neuroscience has also found evidence that there are dedicated counting regions in our brains.
Counting is a human instinct. Based on that instinct, we invented our human mathematics, with integers at its foundation.
So here’s the question: can aliens invent this kind of mathematics?
Maybe not. For example, suppose a gaseous intelligent life-form emerged on a gaseous planet. Its body would be a cloud of gas, like that gold-farting cloud in Rick and Morty.
On such a gaseous planet, most things wouldn’t be discrete. There would be nothing like individual fruits or individual people, but continuous, ever-changing things everywhere: clouds that grow and shrink, light that changes color, and so on. Life evolving in this environment might never invent the concept of “integers.” Instead, it might well invent a mathematical system based on concepts of shape and size.
The key point is that our human mathematics happens to let us invent airplanes, bridges, cars, radio, computers, and all these other things. Our mathematics happens to support the development of a technological civilization. Other mathematical systems developed by other civilizations, however, might not lead to technological civilizations. So intelligent life might arise on those planets, and they might even have mathematics, but their technology could remain stuck at a very primitive stage forever.
Aliens having different mathematics—that’s one possible explanation of the Fermi paradox. Do you think it makes sense?
Actually, this explanation has a major loophole: it can only explain why some civilizations might turn out this way. It certainly can’t apply to all extraterrestrial civilizations. As long as there is a counterexample in the universe—as long as some alien civilization invents mathematics like ours—we still need another explanation for why we can’t find them.
Many explanations of the Fermi paradox have this same problem: they can explain why we can’t find some extraterrestrial civilizations, but not why we can’t find all of them. If this comes up again later, I won’t spell it out every time.
All right, let’s move on to the second psychologically meaningful explanation of the Fermi paradox. The second explanation is that humanity is inside a restricted zone established by an advanced extraterrestrial civilization. This is a wonderfully conspiratorial flight of fancy. It assumes that the Milky Way actually reached a stage of highly advanced civilization long ago, with many planets already highly developed. The galaxy isn’t desolate at all; it’s actually bustling. But for a highly advanced civilization, expansion stopped being a need a long time ago. Extending its sphere of influence to the solar system would be terribly low-class, beneath its notice.
So what matters most to them? Knowledge created by newly independent civilizations—that is what they value most.
In other words, advanced civilizations are really pursuing diversity, or as Wang Xiaobo put it, “Remember: variety and multiplicity are the source of happiness.” In this explanation, Wang Xiaobo is the god of the Milky Way.
In pursuit of this highest goal of diversity, the advanced civilizations of the Milky Way reached an agreement. Together, they designated the star systems inhabited by less-developed civilizations as restricted zones that advanced civilizations may neither enter nor interfere with. No one is allowed to contact these less-developed civilizations or reveal their existence. The advanced civilizations even use their black technology to wrap the zones in an illusion, so that the less-developed civilizations can’t observe any signs of advanced civilizations.
Earth belongs to one of these less-developed civilizations, and our solar system is inside one of these restricted zones. Only one day, when Earth’s civilization has advanced beyond a certain threshold, will we join the Milky Way’s club of advanced civilizations. Then the truth of the universe will finally be revealed before our eyes.
Leaving aside how likely this flight of fancy is, I think the most interesting thing about it is how it understands the question of diversity. Let me ask you something: if you want to produce diversity—for example, cultural diversity, as between Chinese and American culture—what do you think is the most important precondition for that diversity to arise?
The most important precondition is actually mutual isolation.
Diversity comes from isolation. With enough mutual exchange, things that were originally different gradually converge, and diversity slowly disappears. That’s because many problems actually have one solution that is the most advantageous and dominant. When things are isolated, less-dominant alternatives can survive too. But once everything merges, the strongest winner often takes all. Biological evolution works this way: if the biosphere interacted fully with itself, biodiversity would plummet. Art is like this too. After globalization, winner-takes-all dynamics in music and film have intensified as well.
So in that “restricted-zone explanation,” the alien civilizations’ understanding of diversity is remarkably on point. Only isolation can create diversity. That’s why they have to keep less-developed civilizations inside restricted zones and avoid contact with them. For this operation, I give them full marks.
Actually, many explanations of the Fermi paradox, like the one just discussed, work by focusing on the motives and mental states of alien civilizations. These explanations are all highly psychological. For example, Cixin Liu’s “Dark Forest Theory” is also a kind of psychological explanation of the Fermi paradox. The core of Dark Forest Theory is the emotion of fear. It says that advanced extraterrestrial civilizations are all afraid that the moment they show themselves, another civilization will destroy them, so they all hide themselves. Where Is Everybody? contains several hypotheses quite close to Dark Forest Theory, but I won’t go into them here.
Now let’s discuss the third psychological explanation of the Fermi paradox. The third explanation: advanced extraterrestrial civilizations have lost the motivation to expand. This too explains the Fermi paradox from the angle of mentality and motivation.
One core assumption of the Fermi paradox is that if an alien civilization becomes advanced enough, it will inevitably expand across the stars, and we should therefore encounter it. But what if, after a civilization reaches a certain level of development, living beings simply lose the desire for interstellar expansion?
Could that happen?
It could very well happen. Civilizations don’t necessarily have the drive to expand outward. The example given in Where Is Everybody? is our own Ming dynasty. The Ming was an empire that had almost no incentive to expand and was entirely turned inward. So why wasn’t it interested in expansion? There were cultural reasons, but economic reasons are more likely: under the conditions of the time, expanding outward simply wasn’t economical. The costs were too high and the returns too small.
Likewise, because the universe has a speed-of-light limit, even if advanced civilizations have the technological capability for interstellar expansion, they’ll eventually discover that interstellar expansion has an absolutely terrible cost-benefit ratio.
So which direction would they develop in the end? Most likely, they’d explore virtual worlds. In other words, they all ended up playing video games. After all, it’s hard to push beyond the limits of the physical world, while the virtual world has infinite possibilities.
So why can’t we find any alien civilizations? Under this explanation, the answer is simple: all the aliens eventually turned into gamers.
Is this explanation reasonable? Think about our own reality and you’ll find that it is. Aren’t we humans already heading down this road? Musk, with his plans to go to Mars, is basically a lone hero; the internet is the true master of this world. Science-fiction fans often complain: “I was promised the stars and the sea, but all I got was an iPhone, TikTok, and Honor of Kings.” But for all we know, the iPhone, TikTok, and Honor of Kings may be humanity’s final destination—and the final destination of every advanced civilization in the universe.
Now let’s move on to the fourth psychologically meaningful explanation of the Fermi paradox. This is the heavyweight explanation in today’s video: the idea we mentioned at the beginning—that intelligence at the human level is extremely rare, that the evolution of human intelligence may have been pure chance, and that we may even be the only example in the entire universe so far.
I’ll discuss this part with reference to Steven Pinker’s How the Mind Works.
Could the emergence of intelligence have been accidental?
It could.
Because becoming smarter isn’t actually an inevitable outcome of evolution. Organisms can become bigger, faster, more poisonous, more fertile, or capable of flying higher and farther. None of that means becoming smarter. Evolution is about “surviving”; becoming smarter is merely one of millions of ways to survive.
What’s more, becoming smarter doesn’t necessarily make survival easier. In fact, it comes with some obvious disadvantages.
Intelligence depends on a highly developed brain. But a highly developed brain creates a lot of problems.
First, the brain is too bulky. Before a baby is even born, its brain has already grown to an excessive size. Before modern medicine, many women died in childbirth. And then there’s the fact that we have these heavy heads bobbing around on our fragile necks, which makes it easy to suffer a fatal injury when we fall. Other mammals aren’t nearly as prone to brain injuries, but we humans are practically concussion specialists.
The second problem with a highly developed brain is that it consumes too much energy. The nervous system is a major energy hog: our brain accounts for only 2% of our body weight, yet it consumes 20% of our nutrients and energy.
The third problem with becoming smarter is that the brain needs time to learn how to use itself. We humans spend a huge portion of our lives either being children or looking after children. Why is human childhood so long? To give the brain time to mature, of course.
The final problem with becoming smarter is that as the brain becomes more advanced, it also becomes slower. Even when carrying out a very simple action, the human brain’s complexity often makes it take several detours. As a result, humans react far more slowly to many simple tasks than some simple-minded animals do. The average human IQ is around 100, and a fish’s is close to 0, but it is basically impossible for a human to catch a fish with bare hands.
So if becoming smarter has so many disadvantages, why did our human ancestors still take the evolutionary path of developing a big, clever brain?
No one actually knows the definitive answer. This evolution happened only once on Earth, and perhaps only once in the universe. But in Steven Pinker’s view, the evidence we have gives us reason to believe that our ancestors at least collected all seven Dragon Balls—well, five of them. These five either made evolving a clever brain relatively easy or made becoming smarter more beneficial than harmful. That was what summoned the dragon and enabled humans to develop intelligence.
So which five Dragon Balls did our ancestors collect?
The first Dragon Ball was vision.
This element may be pretty surprising. We don’t usually connect intelligence with vision. But in reality, human intelligence is highly dependent on vision.
This point probably needs a bit more explanation.
We humans belong to the primate order, a group of animals with highly developed visual perception. A large part of a primate’s brain is devoted to visual perception. In a rhesus macaque, for example, half the brain is allocated to vision.
Early in their evolution, primates first developed stereoscopic vision. They use the difference between what their two eyes see to perceive depth: the left eye sees a little more of the left side, and the right eye sees a little more of the right. The cerebral cortex combines the two images into depth perception—basically the same principle as a 3D movie. At that time, primates lived in trees and were mainly active at night, so depth perception gave them a huge survival advantage. It let those monkeys move nimbly between branches and also locate and catch insects.
In addition to stereoscopic vision, our primate ancestors evolved sophisticated color vision. Color vision is thought to have emerged when our primate ancestors shifted from nocturnal to diurnal activity.
Why are these two visual abilities so important?
Because depth perception turns 2D vision into 3D vision. And with color vision, an animal can easily separate an object from its background. Think about it: on a black-and-white television, it’s hard to tell where the person ends and the tree begins, but on a color television, everything is immediately obvious.
When depth and color are combined, they allow our primate ancestors to reconstruct a three-dimensional space very accurately in the brain, and to precisely perceive the position and movement of objects within it. That’s all extremely useful information for survival.
One side effect of the evolution of depth and color vision was the corresponding evolution of our ancestors’ thinking abilities. Vision left a deep imprint on their thinking, and that imprint has continued into us. Human thought is in fact highly visual.
The first sign of the visual nature of thought is that when we think through different problems, we actually use visual images to do it. Even when thinking about abstract questions, we generate all kinds of “visible” visual imagery in our minds and use those images to understand the problem. Many creative people, for example, say that they “saw” the solution to a problem in their mind’s eye rather than “thought” of it.
Faraday and Maxwell imagined the electromagnetic field as tiny tubes filled with liquid, and from that came electromagnetic theory.
When the chemist Kekulé was thinking about the structure of the benzene ring, he imagined seeing a snake biting its own tail, which led him to work out the structure of the benzene ring.
Einstein imagined what he would see if he traveled along a beam of light, and what he would see if he dropped a coin into a rapidly falling elevator. That led, eventually, to the theory of relativity. Einstein once wrote: “My special ability lies not in mathematical calculation but in imagining effects, possibilities, and results.” That imagination was essentially imagination in the form of visual scenes.
The second sign that our thinking is highly visual is that our language contains a huge number of metaphors about space and position. When expressing many ideas, we use an object’s location or the movement of an object through space as a metaphor. Let me give you a few Chinese idioms and see what you make of them:
Do not forget past events; they are lessons for the future.
Highly virtuous and greatly respected.
To place oneself outside the matter.
Where are the metaphors? You can’t really hear them, can you? That’s because these metaphors are so universal that you’ve become deaf to them. “Do not forget past events; they are lessons for the future”—why does “in front” represent the past and “behind” represent the future? “Highly virtuous and greatly respected”—why is a “high” position associated with good morals? “To place oneself outside the matter”—why does “outside” represent distancing yourself from an affair?
If you pay a little attention, you’ll find that language is full of metaphors involving direction, space, and the movement of things through space. And this is cross-cultural: every language in the world is packed with metaphors related to vision. In the bullet comments and the comments section, feel free to add examples of similar metaphors you’ve learned in English. The reason this happens is that human thought relies enormously on visual scenes.
That’s why vision is the foundation of human intelligence.
Conversely, if our primate ancestors hadn’t happened, by sheer coincidence, to develop brain regions for processing visual information, humans could never have acquired the kind of intelligence we have today. We probably couldn’t have invented the mathematical knowledge I mentioned earlier, and we wouldn’t have developed the technologies we’re familiar with now.
In fact, this highly developed visual ability is extremely unusual among mammals. Most mammals lie close to the ground, sniffing the chemical traces left by other organisms and using smell to perceive all sorts of things. My dog is a living example. Going out for a walk is like playing Minesweeper: he keeps sniffing everywhere. His nose is excellent, but his eyes are hopeless. He’ll smell another dog’s urine from far away and run over, only to become blind at close range and fail to see where that puddle is. The brains of most mammals don’t understand the world as a three-dimensional coordinate space. They understand it as a flat, two-dimensional plane, where smell is more useful than vision.
So our human ancestors collecting the Dragon Ball of vision was pure coincidence.
All right, here’s the second Dragon Ball. This one should be easy to guess: language.
Language lets humans refer to abstract concepts, use words to point out all kinds of things around us, and describe events that happened in the past as well as events that will or might happen in the future. Through grammar, we can generate an infinite number of combinations of meaning. It’s because of language that our thinking can become this complex. You could say that our intelligence is built on language.
How language originated is still a scientific mystery. But so far, roughly 50 billion species have appeared on Earth, and only our species has developed language. That alone strongly suggests that evolving language is extremely difficult.
It’s very likely the result of a whole series of evolutionary coincidences coming together. For example, producing clear speech with all kinds of changes in pitch and tone requires an organism to control its breathing freely. In other words, it has to be able to actively control how much air enters its lungs, as well as the rate of its breathing. That’s easy for us humans, right?
But did you know that most four-legged mammals can’t breathe voluntarily? Leopards, lions, and tigers can’t consciously control the rate or depth of their breathing. They can only rely on the movement of their limbs while running to drive the expansion and contraction of the chest, breathing passively in the process. We humans may have evolved voluntary breathing in response to the evolutionary pressure of long-distance running across the grasslands, giving us complete freedom to control the rate and depth of our breathing. And, by a wonderfully roundabout twist of fate, that prepared the ground for language to appear.
The emergence of language required a whole pile of conditions like this, all of which had to come together. The odds were incredibly, incredibly small. And our human ancestors just happened to be the super-lucky winners of the jackpot.
See? Getting our hands on the second Dragon Ball also took an unbelievable amount of dumb luck.
And now we come to the third Dragon Ball. The third one collected by our human ancestors was—living in groups.
The overwhelming majority of apes and monkeys live in groups, and living together has many advantages. First, if a troop of monkeys is spotted by a tiger or lion, the chance of any one individual being chosen as the meal gets spread around. When the tiger charges, I don’t have to run the fastest; I only have to be a tiny bit faster than the monkey next to me. Second, finding food becomes much more efficient. Group-living monkeys can hunt cooperatively and share meat and fruit.
This group life probably promoted the evolution of intelligence in two ways. First, group living itself created enormous cognitive challenges. A bunch of monkeys living packed together have to compete for food, water, and mates. Sartre said, “Hell is other people.” If monkeys could talk, they would definitely say that other monkeys were hell too.
So figuring out how to outwit and outmaneuver these monkey neighbors created pressure that promoted the evolution of intelligence. In the process, our primate ancestors gradually evolved the ability to deceive, the ability to read other people’s expressions and moods, and the ability to temporarily suppress their impulses to please a leader. In a word, they became smarter and smarter. So “smart” may well be something that these group-living animals worked themselves into through endless internal competition.
Still, this internal-competition mechanism probably wasn’t the only prerequisite for intelligence to evolve. Otherwise, every group-living animal on Earth should have evolved intelligence. So there must have been other factors promoting the evolution of human intelligence. For a species with language like ours, for example, information becomes especially valuable in group life. The information contained in language is knowledge—and you can use that knowledge to exchange things with the other people, the other monkeys, living alongside you. So for a solitary monkey, being clever at making effective use of information might not be much use. For a group-living monkey, that kind of cleverness is a major advantage.
Let’s look at the fourth Dragon Ball—the hand.
Dexterous hands and sophisticated intelligence very likely co-evolved. Without intelligence, the hand wouldn’t know what complex operation to perform; without the hand, intelligence would lose one of its most important outlets. You might have the ability, but nowhere to put it to work.
So hands and intelligence very likely brought out the best in each other.
And the prerequisite for hands to evolve was walking on two feet. Once again, we have our primate ancestors to thank. Back when our ancestors were still living in trees, their upper limbs had already begun evolving toward grasping things rather than bearing weight. Those ancestors were already better adapted than other mammals to holding their upper bodies upright.
Then, when our ancestors moved down to the ground—to the grasslands—the advantages of walking on two feet became fully apparent. Upright bipedal walking is the best form of locomotion for traveling long distances, allowing our ancestors to cover very long distances across the grasslands. Human ancestors could also go out and be active under the blazing sun at the hottest time of day, using this time difference to avoid most predators. Scientists suspect that our lack of body hair and our ability to sweat heavily both evolved along with this history. Upright walking may also have evolved to serve this purpose, because an upright posture exposes the body to the least sunlight.
Only with upright walking could our ancestors’ upper limbs eventually evolve into hands capable of precisely manipulating objects. But as you can see, hands also required quite a few prerequisites. Leave out even one of them, and hands might never have evolved. Our human ancestors were lucky to get this Dragon Ball too.
Finally, the fifth Dragon Ball our human ancestors got their hands on was—hunting.
When hunting large prey, our human ancestors needed highly sophisticated teamwork and the ability to make far-sighted plans. In other words, they needed a good brain. Hunting may therefore also have been a major factor in the evolution of intelligence.
But this explanation is very liable to annoy women. It implies that the evolution of intelligence owes a great deal to male ancestors, since it seems the men were the ones who went hunting. But let’s not rush to object. First, quite a bit of recent archaeological evidence suggests that the proportion of female hunters may have been far higher than we used to imagine. Second, how much the mind contributed during the process of hunting actually isn’t the key point. What really matters is the result—what effect the meat obtained through hunting had on the mind.
Hunting provided meat, a highly concentrated source of nutrition. Plant foods also provide calories and other nutrients, but meat is complete protein containing all 20 amino acids, and it also provides energy-rich fat and essential fatty acids. And as we said earlier, the brain is an extremely energy-hungry organ. Without hunting, the nutritional foundation for the evolution of the brain would never have existed.
What’s more, hunting is largely a matter of luck. Three hunting teams—A, B, and C—from one tribe might go out, and only Team A might come back with a huge haul while the other two return empty-handed. But next time, the wheel of fortune turns, and Team A might be the one that gets nothing. So in ancient times, before refrigeration, the hunters’ best strategy was to agree to share the meat they got on every hunt. The tribe therefore needed to establish a system of reciprocity and mutual constraint. And that brings us back to the role of the third Dragon Ball: the more complex the cooperative relationships in group life, the more they depended on a clever brain.
Putting it all together, you can see that our human ancestors had to collect at least five Dragon Balls before they could summon the dragon and develop our current level of intelligence. At least two or three of these five Dragon Balls could only be obtained through cosmic-level dumb luck.
That kind of dumb luck has appeared only once on Earth. But what about the universe? Could we be the only jackpot winners in the entire cosmos?
Personally, I think this may be the most reasonable answer to the Fermi paradox. There may be plenty of planets in the universe capable of producing life, even complex life. But the emergence of intelligence at the human level from life is almost impossible. We humans spend all day imagining that there are worlds beyond our world, but it’s entirely possible that we ourselves are the ceiling of the universe. On the stage of the universe, we’re the only actors—and the only audience.
Actually, one of the most likely answers to the Fermi paradox is this: the reason we can’t find aliens is that the kind of high-tech aliens capable of interstellar travel and sending signals simply doesn’t exist. Stephen Webb, the author of Where Is Everybody?, agrees with this view. We humans may well be orphans of the universe. The universe is so quiet not because of some illusion; the universe really is utterly silent.
The French biologist Jacques Monod once wrote: “Humanity finally knows that it is alone in the indifferent immensity of the universe, from which it emerged only by chance.” That’s a genuinely melancholy thought.
But alongside that melancholy, shouldn’t we also feel an enormous sense of responsibility? That responsibility is this: we really have to respect ourselves, do fewer stupid things, and be very careful not to casually kill ourselves off. We need to make sure the human species continues for as long as possible. Because this species that keeps doing stupid things may actually be the only intelligent species in the universe! If we accidentally wipe ourselves out, how lonely would this universe be?
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