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Serina Evolution Thought Experiment
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0:20
What would happen if, on a small terraformed planet, we released… almost nothing but canaries? What if we let this one species evolve into dozens of different ecological niches, with no interference whatsoever — and gave them a few hundred million years to evolve? What would those canaries become? That’s the thought experiment behind Serina, also known as Serina: A Natural History of the World of Birds — a speculative evolution project presented through text and illustration on a website.
0:46
But you and I are going to explore it a little differently.
1:05
Before we dive in, let me quickly introduce the educational partner for this video: Duolingo — Languages, Math, Music — all of which you can learn in a fun, gamified, and completely free way. With Duolingo, you get access to over 100 courses in 41 languages — English, Italian, Latin, Zulu — so yeah, you’ve got options, and it’s actually fun. Learning with Duolingo means learning through play. You get quests, challenges, leagues, leaderboards — Each lesson is a step in your journey —
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short, fun, and engaging. Duolingo makes sure that wherever you are, and no matter how much time you have, you can keep learning. Whether you’ve got a few minutes on the subway, the couch, or in a waiting room — you pull out your phone, make progress, and move on with your day. The idea is to keep growing — maybe you’re aiming for a B2 level in English — while having fun, at your own pace, step by step, whatever your goal may be: a trip, an exam, or just a curiosity about another culture,
1:53
or now even to explore much more. And now, Duolingo goes beyond languages — you can also learn music and math. Train your ear, read sheet music, refresh your skills in arithmetic — all free, and right in your pocket. If that sounds good, check the description — you’ll find everything you need to start your journey.
2:10
Now then — back to our journey.
2:15
Welcome to Serina.
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We don’t know exactly where it is in the universe. We’re not even sure it’s in our own galaxy. What we do know is that Serina is — or was — a moon. More precisely, the moon of a gas giant orbiting within the habitable zone of a distant star system. Roughly two-thirds the size of Earth. One day, an unknown entity — let’s just call it the Other — decides to terraform this moon, reshaping it to resemble our Earth. The goal? To make this once-barren world capable of sustaining life.
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So, the Other builds an Earth-like atmosphere, stabilizes the moon’s rotation, and gives it just enough tilt to create seasons and familiar day-night cycles. Serina’s landmass starts as one massive supercontinent called Cirrus, an arc-shaped landform linking five major regions via narrow isthmuses. Clever move from the Other — this layout lets plant and animal life spread across the world freely, without any oceans in the way. As the biosphere takes hold, Serina’s climate is hot and humid.
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Its atmosphere is rich in oxygen, creating a tropical world with average temps around 16°C. There are no ice caps; only the poles experience a mild winter chill — the rest of the planet is a lush, tropical Eden perfect for life. Once everything is ready, the Other begins introducing life — in small quantities — but life that’s already had millions of years of evolution behind it. It introduces fish, crustaceans, jellyfish. Plants grasses cereals bamboo flowers algae moss. Microorganisms.
3:43
Insects mollusks worms ants… In short, all the elements needed to build a thriving ecosystem. And finally — once all that’s in place — the Other introduces the real subject of this experiment: the one and only terrestrial vertebrate species on Serina… <i>Serinus canaria</i> — the canary.
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Here’s our protagonist, dropped into a world with no interspecies competition. No mammals, no reptiles, no amphibians were ever introduced; Serina is now a world of birds, and birds alone. Ok. So… what happens next?
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Well — they eat.
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And they reproduce. A lot. With near-unlimited food and zero predators, things ramp up quickly. They feed on seeds and young plant shoots. Each mating pair can produce over fifteen chicks a year. Let’s break it down. A male canary, a female canary. Each carries DNA — their genetic recipe. • When the male produces a sperm, half of his recipe is copied into it. • When the female produces an egg, half of hers goes into that. When sperm meets egg, they merge, creating a new being
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with a unique blend of both genetic blueprints. With our canaries, the parents are very similar, they merge very similar genetic recipes— so naturally, their chicks turn out almost identical. Nothing really changes yet.
5:14
But let’s fast-forward a bit. And by “a bit,” I mean a lot. Our first time jump? Ten thousand years.
5:29
After over 7,000 generations, canaries have slowly spread across the five major landmasses. And even in that relatively short time, we can already start to see some noticeable differences between certain canaries. On the plains of Anciska, we find large, solitary canaries with gray-and-white plumage, strong enough to crack open seed shells the size of almonds. Elsewhere, there are small red canaries gathering in flocks to nibble on fresh shoots.
5:52
After 10,000 years, this moon still has no trees or bushes. So most canaries build their nests directly on the ground — like this female, returning home after hours of foraging… The problem is when she gets back to her nest, she finds her eggs smashed, shells broken. Just a few meters away, a canary watches from the shadows. One of his ancestors, rather than chase after bugs, survived more easily by eating the eggs of others — left unguarded, exposed on the ground.
6:17
That strategy worked. The genes were passed down. A few decades or centuries later, here we are: And now we’ve got a population of specialized canaries — egg-eaters. Serina is already losing its innocence. The canaries are no longer completely safe. But let’s put danger aside for a moment— How are all these differences even possible? Why is it that, after 7,000 generations stemming from a single species of canary, recycling the same genetic recipe over and over,
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we suddenly have so much diversity? That’s evolution— the process by which living organisms transform and diversify over generations. And it’s a good opportunity to dust off the concept a bit. Because when people talk about evolution today, either it’s being questioned entirely, or you get the feeling they’re talking about some kind of sentient being— a mini god of sorts, as if Mother Nature had a will of her own and chose to shape creatures this way or that, depending on the situation.
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That’s really how we talk about it— like it’s some sort of intelligent force. But it’s not. Evolution has no consciousness. It’s a process — blind, painfully slow, and fundamentally random. And yet, it’s beautiful. Let’s go back to our pair of canaries. If they kept passing down identical versions of their genes, even shuffled randomly between them, nothing would change. Our small yellow canaries — 11 centimeters long, 15 grams — would just keep producing more of the same.
7:32
But that’s not how evolution works. It works because of errors. Mutations. Something glitches in the code — a random change in a canary’s DNA. The recipe shifts in a completely unexpected way. These genetic hiccups can happen in a few ways: • Sometimes it’s external — a virus, or UV rays from the sun. • Sometimes it happens during DNA replication — when cells divide and need to copy their DNA to pass it on to the new cells •And sometimes, when sperm and egg are being made —
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DNA gets shuffled and reassembled, sometimes, boom, a glitch. A mutation appears, and it can be passed on to the offspring. That’s how new traits emerge. That’s how evolution happens. From mistakes. A shorter limb, broader wings, a different feather color— it could be anything. Now let’s say it happens to the chick of our canary couple. There was a mutation — and it was born with an unusually long beak. Huh. Interesting. But if it’s the only one with the mutation,
8:28
and all the other canaries still have short beaks, there’s no reason for this long-beaked trait to spread. No reason for a new long-beaked subspecies to emerge. But this is where the beauty of evolution lies— in one of its most cruel and fascinating branches: natural selection. It’s the environment that decides. The real world. The day-to-day struggle. Most of the time, a mutation is either neutral or disadvantageous. It’s pretty unlikely that a random new trait
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would just happen to benefit a bird in its environment. Our long-beaked chick, for example, might not be able to peck at the same food its parents did. If that’s the case, it won’t survive — and its genes die with it. But sometimes, a mutation is beneficial. In another environment, for instance. Our long-beaked canary chick might be able to dig into anthills and eat insects that would’ve otherwise been safe. In that case, the chick survives, mates, and passes on that new trait.
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And the more its descendants thrive with their long beaks, the more they’ll reproduce, and the more of them there’ll be. Eventually, after many generations, a whole new species appears— long-beaked canaries, specialized in insect hunting. Quick detour before we get back to them: What exactly is a “species”? And what’s a “race”? A species includes animals that may look quite different, but are still able to reproduce with each other. If two individuals—no matter how different they seem—
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can mate and have offspring that can also reproduce, they belong to the same species. A race, on the other hand, is a bit more controversial. But on paper, it’s like a species that’s starting to split into two— but hasn’t quite done so yet. It’s not usually an official biological classification, but rather a way of grouping within a population. Alright. That’s the gist of it. No divine plan from Mother Nature. No artistic direction. No grand design. Just chaos—and time. That’s evolution.
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Fifteen million years after this whole experiment began, we arrive at the Kyran Islands, straddling the equator in the middle of the ocean. These islands are home to one of the largest bird species on Serina:
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the Chubirds.
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These birds are huge, and heavy. Their wings are stunted—completely useless. Neither of these traits is particularly surprising— we’ve seen them in biology before. Flight, for birds, is incredibly energy-intensive. So if a bird lives in a place with no threats, no need to escape quickly— natural selection can favor reducing or even losing the ability to fly. That energy can be redirected toward other adaptive traits: larger body size, bigger eggs, and so on.
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And on Kyran, the Chubirds have no predators. So—no need to flee. And so, their wings gradually vanish, and their bodies grow massive—up to three meters tall and 400 kilograms. They move slowly—but that’s fine. No one’s hunting them. They just eat whatever they find: shoots nuts leaves. Lots of leaves, and that leads to an interesting evolutionary loop: Over the millennia, as the Chubirds keep growing taller to reach higher foliage, the trees start adapting too, growing taller,
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trying to stay out of reach of the giants. They literally pull each other upward.
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That said, these giant birds do face one real threat —
11:51
or rather, their chicks do. When they hatch, they’re completely vulnerable. The father is never around — he’s off eating all the time. The mother, on the other hand, stays with the chicks to protect and feed them, often remaining by their side for days, wholly dedicated to her young. But eventually, she has to leave to feed herself. And as soon as her towering silhouette disappears over the horizon, creeping in from the undergrowth comes a slow, clicking horde of blue-pink creatures,
12:18
waving their claws in anticipation: Land hermit crabs, who’ve been waiting for this moment for days— for the chicks to be left alone. As soon as the coast is clear, they make their move, swarming the nest. The chicks huddle together, forming a tight cluster, trying to bury themselves in the center to avoid the reaching pincers. And that works… for a while. But eventually, the crabs manage to grab a leg, or a wing, and pull the weakest chick out to devour it whole.
12:45
The Chubirds, born in large numbers to offset high mortality, face an 85% chance of dying within the first three weeks of life. They grow quickly, sure, but until they reach full size, their life is hell. They become heavy—technically large enough to defend themselves— but in practice, they’re still unable to move for several more weeks. And for these chicks, it’s even worse than for the ones that died early. Because once the hermit crabs arrive,
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they can’t flee. They just sit there, being eaten alive. A nibble here, a torn wing there— sometimes over the course of days.
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Eventually, when they’ve grown big enough to move despite their weight, they can finally escape.
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The males will go on to spend their lives eating. The females will live through the loss of most of their offspring. That’s life. At least, on the Kyran Islands.
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Elsewhere, and about 40 million years later, we find a much gentler kind of interspecies relationship. Here’s a finch. Maybe not the flashiest creature in this story — but evolution doesn’t really care about flash. Our finch is wandering across the grasslands, foraging for food — seeds, mostly, and grains. But today’s hunt isn’t going well. He’s struggling to find anything worthwhile. Then, after a while, he hears something.
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Here comes a Serestrider. Like the Chubird before it, this is also a giant herbivorous bird. But this one takes it to a whole new level— standing up to twelve meters tall and weighing several tons. Its massive size protects it from most predators, which is often why some species evolve to be so big in the first place— to eat in peace. Well, “peace” is relative. Some Serestriders have tightly tangled down feathers that form a sort of shaggy coat—
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and that coat is the perfect habitat for small insects. Which is irritating for the giants, who can’t get rid of them. But they’re not alone — they have help. From another species you’ve already met: insect-eating finches. These little birds, much closer to the original canaries, routinely perch on the enormous bodies of the Serestriders and peck away at the bugs scuttling through their feathers. The Serestrider’s body becomes a kind of miniature ecosystem: its blood sustains the insects,
15:06
the insects feed the finches, and the finches, in turn, keep the giant bird clean.
15:21
This relationship between Serestriders and finches is what’s called mutualism: a direct interaction between two species that isn’t strictly necessary for survival, but mutually beneficial nonetheless. The finches get a steady food source. The Serestriders get rid of their unwanted pests. Sometimes, this duo wanders into the bamboo forests: the Serestrider munches on bamboo shoots, while the finches feast on the ants that climb up its body to defend their territory. It’s a beautiful partnership.
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Fast-forward 50 million years, and birds have now colonized the oceans. Every ocean on Serina. It might seem strange to imagine animals shifting— even gradually—from a fully terrestrial lifestyle to a completely aquatic, and radically different environment. But the driving force is more or less always the same: Food. Some land-dwelling creatures occasionally find food near rivers, or along the coastline. And for a few of them, the more time they spend in the water foraging,
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the more natural selection kicks in, favoring traits that let them stay a bit longer… then even longer… until, eventually, after millions of years of evolution, they become fully aquatic. It takes time, obviously—but on Serina, food is plentiful.
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Up north, we find a species called the Birdwhales.
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Massive creatures — though admittedly, not the most creatively named.
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In the ocean, you might’ve noticed, gigantism is more common than on land. Thanks to buoyancy, gravity’s less of a burden. The ocean's lack of pronounced seasons means constant access to food year-round. Movement is more efficient too — less energy needed to travel through water. On top of that, larger bodies retain heat better, making them less sensitivity to the cold. All of this makes the ocean the perfect place for some creatures to grow massive— like our Birdwhales.
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These creatures feed on fish, plankton, and other marine invertebrates. Their wings have evolved into flippers. Their bodies are nearly featherless, covered in smooth skin, and kept warm by a thick insulating layer of fat. They’ve also developed what are known as pseudo-teeth— bony outgrowths that act like teeth to help grasp prey— and bristly structures on their tongues for filtering plankton. And these traits aren’t unique to Birdwhales.
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A few tens of millions of years later, we find the Giant Snark, a creature descended from gastropod mollusks that has radically converged on a ray-fish body plan. Like the Birdwhale, it has broad fins and a wide mouth lined with filtering structures for capturing plankton. Around the same time, we also find the Rakewhale — which evolved from one of the original fish species introduced to Serina. This animal developed a digging-filtering feeding method—
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scraping the sea floor, sucking in water, then pushing it back out while straining for hidden organisms. Fascinating right? Some organisms descended from birds, mollusks, and fish have developed in remarkably similar ways. And that’s no coincidence. It’s what we call evolutionary convergence— when different animals, faced with the same environmental pressures, end up evolving similar traits. Here, our birds, mollusks, and fish were all up against similar selective pressures:
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• The abundance of plankton in the polar seas • The need for efficient propulsion in aquatic environments, and so on. To feed on plankton, each lineage developed its own filtration system. For locomotion, they each evolved flipper-like structures— from wings in the case of birds, from a foot in mollusks, and, well, from fins in fish. Radically different species, exposed to similar constraints, evolving in similar ways. That’s the beauty of evolution.
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100 million years later. The weather is mild. At least in Serina’s temperate forests, it is. In her burrow, a small creature huddles for warmth. It’s hungry. But no one really cares. Higher up in the trees, though—it’s a different story. A Sparrowgull has been tending to its newborn for a little while now. But upon returning home to feed it— its chick is gone. It happens. Some chicks fall—out of nests, off branches, from wherever they were clumsily perched.
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And to find them, the parents rely on sound. That’s the case here. The mother hears a familiar chirp from below, hurries down, and drops a cricket straight into the wide-open mouth of her baby. Except… it’s not her baby. The creature she just fed— without knowing—is a Nest Goblin. A grayish animal, with long ears, hooked fingers, a pointed snout, and a mouth full of sharp teeth— its fate is deeply intertwined with that of the Sparrowgull. A few minutes earlier,
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when it heard a chick chirping after falling from the nest, the Goblin crept from its hiding spot, rushed to the sound, and devoured the chick.
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Once done, it started imitating the cries of the chick it had just eaten— but louder, to drown out the calls of any remaining nestlings. The Sparrowgull mother, panicked, races over and drops food into the Goblin’s oversized mouth— thinking she’s feeding her own. She’s unknowingly feeding the killer of her child. This is a form of avian parasitism— manipulating other birds into feeding you. And a core tactic of this parasitism is mimicry: Imitating the visual and auditory cues of baby birds—
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begging calls, the colored marks inside their beaks, the frantic flapping of wings, etc. This leads to an evolutionary arms race between Goblins and Sparrowgulls. Every defense the host evolves triggers a counter-adaptation in the parasite— a back-and-forth of natural selection stretching over millions of years. The Sparrowgulls evolve defenses, which in turn drive the Goblins to develop even trickier deceptions. And through this escalating adaptation, they’ve been co-evolving
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in a kind of dynamic equilibrium. Again, these seemingly “calculated” behaviors are nothing more than a chain of changes shaped by time and selection. No adaptation is conscious. It is the outcome of a mutation and the effect of natural selection.
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Sneaky little things.
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Now we’re in the far south—of Serina’s southernmost continent, Stehvlandea. It’s cold. The air is dry. Sparse grass is coated with a brittle frost, which crunches under pressure.
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Especially under the pressure of the Goliath Tyrant Serin. With that weight, anything would crunch. Two tons. Nine meters tall. The Goliath is a superpredator— a predator at the very top of the food chain. The absence of predators on Serina allowed the canaries to fill the role of apex predators— just like they filled every other ecological niche.
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Its call is enough to keep any other animal well away from its territory. And that’s the whole point. Not far from this massive creature is its mate—pregnant, and focused on a critical task.
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In southern Stehvlandea, the weather is cold—very cold— and while Tyrant eggs require warmth, neither mother nor father can sit on them: their enormous bodies would crush the clutch. But they’ve found a workaround. The region is volcanic. Hot springs are everywhere. And while the mother won’t lay her eggs directly in the water, she can bury them in soil warmed by geothermal heat. Then let them rest.
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Now, for the first time, I’m going to break the timeline a bit. I’m jumping back a few tens of millions of years. I know, that breaks the rule—but it shows just how important the next species is. We’re south of the equator. In a dense, humid, tropical forest teeming with life.
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Among those lifeforms is one perched high in the canopy. A bird. A member of a very new species— barely four thousand years old. That might’ve made you smile at the start of this video, but 175 million years in, I figure you’re used to the scale by now. This bird is the Fork-tailed Babbling Jay. Compared to some of the creatures we’ve seen, this one’s not very exciting. Modest size, unremarkable colors— it looks like it hasn’t evolved much at all. But the interest lies elsewhere.
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Its name: <i>Loquax philosophus</i>— the “philosopher chatterer.” Its brain weighs just 14 grams— tiny, really—crammed into a skull that can’t afford to get too heavy, or it would lose the ability to fly. So, instead of growing bigger, evolution made it more efficient. Like many birds, this one maximized its brain’s organization and neural density. The result? That tiny brain—barely 1% the mass of ours— functions in a way that’s remarkably similar to a human’s.
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This bird is highly intelligent, as intelligent as we are. It has even reached the point of self-awareness. And if you’re wondering how we get from inert atoms to a being capable of knowing itself— let me know, I’ll make an episode just for that. But our bird has more pressing concerns. It may be aware of itself. But more painfully—it’s also aware that it is the last of its kind. Because this forest…
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wasn’t always a forest. This place used to be called the Rainshadow Desert — a vast, dry expanse on the sheltered side of a mountain range within what was once a tropical belt on Serina. Its name comes from the meteorological phenomenon that shaped it: moisture-laden clouds were blocked by surrounding mountains, leaving this region without significant rainfall. The result? A semi-arid environment marked by extreme seasonal contrasts —
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brief periods of relative abundance followed by long, harsh droughts. But the times have changed. Where once stood only a few withered, cracked trees clinging to life in parched soil, now rise towering giants surrounded by lush, warm, humid vegetation. Drastic climate shifts have transformed the Rainshadow Desert ecosystem — it’s no longer a desert, but a land of shadow and rain. And our Fork-tailed Babbling Jays — clever, adaptive, and long accustomed to abrupt environmental changes —
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have risen to the challenge. They adapted — again and again. They changed their habits without waiting for evolution to catch up. But all the intelligence, all the ingenuity, all the adaptability of their species was powerless against a challenge they didn’t understand. These birds, shaped by generations in dry terrain, had no defenses against the bacteria and pathogens common to humid forest environments.
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The species of the babbling thinker is a new one — just a few thousand years old. A newborn species. Unlike ours, which has had hundreds of thousands of years to learn and adapt before any major disaster wiped us out. But we came close to extinction too. For 99% of our species' existence, had a meteor of the right size struck Earth, we’d be gone. If an aggressive enough virus had spread widely, we’d be gone. In fact, we think it nearly happened — around 900,000 years ago,
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when the human population may have dwindled to barely more than 1,200 individuals, possibly due to climate shifts.
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Today, we have tools to face such threats — at least partially. But we owe that not to genius, but to sheer luck. Without luck — without the time it gave us to develop, to think, to discover — we might have perished at the hands of a threat we couldn’t even comprehend.
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So yes — luck. A stroke of fortune that the babbling jays didn’t have. One by one, group by group, they died out.
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All except this one, high up in the canopy. The last of his kind. His mind full of questions. Beside him, a female from a related — but not identical — lineage, with whom he found refuge. He finds comfort in her warmth, in her calls, in the safety of her group. But his cognitive abilities far surpass those of his new companions. He is the last of a brilliant, now-extinct species. His mind still buzzing with thoughts. About what he is. Where he comes from. About life. And death. And meaning.
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Questions he’ll never get answers to. Because the world never gave his species the chance.
28:55
As we journey across millennia on Serina, we meet creatures that look increasingly different — even downright bizarre. And yes, some of them might seem far-fetched. When you look at this thing, or that one, or that other one, it might all feel like a whimsical thought experiment — but that Serina, in the end, is just the result of its author’s overactive imagination, indulging in wildly exaggerated genetic detours that don’t seem all that realistic.
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But then you remember: this is exactly what happened on Earth. In fact, long before primates, or even mammals — even more incredible things happened right here. Roughly 3 to 4 billion years ago, on Earth, there existed a tiny creature known as LUCA — the shared origin of every single form of life that inhabits our planet today. Everything. That little speck floating in a puddle was the ancestor of all life we know. LUCA is the ancestor of bacteria, archaea, protists… of every fungus…
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every plant…
30:04
and yes, the ancestor of every animal — the Galápagos marine iguana, and the finches that pick its ticks; the tardigrade, microscopic and nearly indestructible, capable of cryptobiosis to survive extreme temperatures, radiation, even the vacuum of space; the whale and the shark, descending from radically different ancestors, yet converging into strikingly similar forms; the axolotl, with its astonishing regenerative powers, able to regenerating limbs, spinal cord, even parts of its brain;
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the cuckoo chick that hatches in another bird’s nest and shoves its rivals out. the flying snake, the cuttlefish, the mantis shrimp, the peregrine falcon, the elephant, the chimpanzee… … and us.
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Our ancestor — and the ancestor of every living thing around us — is that little blob, floating in ancient water. It evolved exactly like Serina’s creatures did: by adapting to pressure and change. Wherever we go, no matter how strange the life around us may seem, we are surrounded by distant relatives.
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And yes — this idea is fascinating on a purely intellectual level. It’s a nice thought on its own — but it becomes something truly magical when you actually feel it. Not just understand it in your head — but feel it in your body. Try it — wherever you are: in a room, on the subway, on the street, in a garden, or out on a balcony. Look at the living things around you, and try to experience them with your whole body. A cat on the sidewalk. A dog curled up on a cushion. A fly on the ceiling.
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A spider tucked in a corner. A slug sliding across the pavement. A butterfly resting on a flower. Then the flower itself. A tree. A single blade of grass. Really look, and feel — in your bones — that the only thing separating you from them is that your ancestors walked different paths. But trace that path far enough back… and you’ll find we all had the same grandparent. We are, quite literally, surrounded by members of our gigantic, sprawling family.
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