Why the anatomy of the deep sea octopus is truly terrifying

Most of this creature's mind is not in its head. It is in its arms. And each of those arms can think on its own. Right now, somewhere in a tide pool, or a coral reef, or two miles down in the freezing dark, there is an animal watching the world with a kind of intelligence that did not come from anywhere near us. We do share an ancestor with it, but you have to travel back around 600 million years to find that ancestor, and it was basically a little flatworm with almost no brain at all. So everything clever about you, and everything clever about the octopus, was invented completely separately, two different times, on the same planet. That is why scientists keep describing it, alien, not as a joke, as the most honest word they have. The octopus may be the closest thing to alien intelligence we will ever meet, and the truly strange part is that it grew up right here. So how does a soft, boneless cousin of the snail end up this smart? How can anything think at all when its brain isn't kept in one place? Let's go meet it. Start with the part of the octopus we think we understand, the brain. Neurons are the cells you think with, the tiny living wires that carry every thought, every memory, every flicker of a decision. You have around a hundred billion of them. A snail, which is a close cousin of the octopus, has about 20,000. That is the entire mental budget of a snail. The common octopus has around 500 million. That is not snail territory at all. That is roughly the same range as a dog, a cat, or a parrot. A soft little sea animal with no bones is carrying about as much raw brain power as the pet sleeping at the foot of your bed. Only about a third of those neurons actually sit in the central brain. The other two thirds are spread out, running down its eight arms. The octopus does not keep its mind tucked behind its eyes the way we do. It smears it across its whole body. And the central brain it does have is shaped like a ring, a little donut. And that donut is wrapped around the animal's throat, so its food slides straight through the hole in the middle of its brain on the way to its stomach. Picture your own brain as a bagel with every meal you eat passing right through the center of it. For an octopus, that is just Tuesday. So there is no single command room behind the eyes. There is a small ring of a brain looped around the throat. And then there are eight arms, each one packed with its own private tangle of nerves. It is less like a company with one boss barking orders, and more like eight expert workers who mostly run their own departments and only loop in head office when something big comes up. For most of the animal kingdom, that arrangement would be chaos. A body needs one chain of command, one place where decisions get made, where everything falls apart. The octopus throws that whole assumption out and somehow comes out faster and smarter for a tea. If most of the thinking is happening out in the arms, far from the central brain, then what exactly are those arms doing on their own? Cut an octopus arm off, and for up to an hour, it keeps going. It reaches. It explores. It pulls away from anything sharp or painful. It will even try to pass food toward where the No central brain, no connection to the body at all. The arm just carries on, making its own little decisions in the dark. That it is everyday octopus biology, and it points to something remarkable about how this animal is wired. Each arm is lined with suckers, and those suckers are not just for gripping. They taste. A giant Pacific octopus has around 280 suckers on every single arm. That is more than 2,000 taste and touch sensors across its body, and a single sucker can hold tens of thousands of tiny receptors. So the octopus reaches into a black crack in the reef, and it does not need to see what's in there. The arm tastes the crab. The arm feels the shape. And the arm itself decides, grab it or keep searching, before the central brain is even part of the conversation. Its arms taste by touch, as if your fingers could lick everything they brushed against. When it hunts, an octopus can send several arms into several different cracks at once. Each arm works its own problem at the same time. The brain isn't micromanaging any of it. The brain sets the goal, like a conductor who sets the tempo, and then lets each musician play their own part. People who study this describe it as having something like nine minds working in parallel, one in the middle and one in each arm. When scientists actually filmed octopuses exploring and tracked how the arms moved, they found exactly that. Sometimes the arms moved together, taking direction from the brain, and sometimes they worked independently, each one making its own call, with some of the information never reaching the central brain at all. That is why it reacts so fast. A single central brain like ours has to pull every scrap of information back to one place before it can act. The octopus doesn't bother. It handles a dozen streams at the same time, out at the edges, where the action is. What time are you watching this video? Check in and let me know. A mind turned inside out would be strange enough on its own, but the body wrapped around it might be even harder to believe. The octopus has three hearts. Two of them push blood to the gills to pick up oxygen, and the third pumps it out to the rest of the body. Here is the catch. That third heart stops beating every time the octopus swims. Swimming literally tires its heart out, which is exactly why an octopus would almost always rather crawl than swim. Three hearts and it still gets winded. Its blood isn't even red, it's blue. Yours carries oxygen using iron, and iron turns red when it grabs oxygen. The octopus uses copper instead, and copper turns blue. It isn't just for show either. That copper-based blood is better at hauling oxygen around in cold, low-oxygen water, which is precisely the kind of place a lot of octopuses live. And there aren't any. The only hard part of an octopus is its beak, a little parrot-like bite right at the center of its arms. Everything else is pure muscle and skin, which means it can pour its entire body through any gap bigger than that beak. A two-foot octopus can squeeze through a hole the size of a coin, because there is nothing rigid to stop it. The range of these animals is just as wild. At the big end, you have the giant Pacific octopus, stretching up to about 16 feet across, which is roughly 5 meters, and weighing up to 110 pounds, around 50 kilograms. At the other end is the blue-ringed octopus, small enough to sit in the palm of your hand, carrying a venom strong enough to kill a grown adult in minutes. Three hearts, blue blood, no bones. We are barely getting started, and nothing about this body follows the usual rules. And we still haven't reached the trick that made half the internet call it alien in the first place. The one where it simply, completely disappears. Watch an octopus vanish, and your brain refuses to believe it. One second there is an animal sitting on the sand. The next second there is a rock, or a clump of seaweed, or a patch of coral, and the animal is gone, even though you never saw it move. An octopus can change both the color and the actual three-dimensional texture of its skin in about a fifth of a second. Its fastest reactions land near 200 milliseconds, which is about as quick as the fastest blink you can manage. So it can go from a smooth pebble to a spiky lump of coral in less time than it takes you to close your eyes. And it doesn't do this once in a while. One researcher watched a single octopus change its disguise 177 times in a single hour. That is a brand new costume roughly every 20 seconds all day long, while it crawls across a constantly shifting seafloor and repaints itself to match every new patch of ground. So how does it work? Its skin is packed with tiny pockets of color, like thousands of little balloons of dye, and around each one is a ring of muscle. Squeeze the muscle and the balloon stretches open so the color blooms out bright. Relax it and the color shrinks away to nothing. Underneath those color pockets sit mirror-like layers that bounce light around to make blues, greens, and whites. Combine all of that and the octopus can copy almost anything in its surroundings. The real secret is in the speed. A chameleon changes color using hormones, chemical signals carried through the blood, and that is slow. Sometimes 20 seconds or more. The octopus runs its color with nerves instead. It fires the change like flipping a light switch, which is why it is basically instant. And it goes one step further. It can raise little bumps and ridges across its skin because predators tend to spot prey by catching the hard edges and outlines of a shape. So the octopus erases its own edges. Some species push this into pure theater. The mimic octopus doesn't just blend in. It impersonates other animals, flattening out like a venomous flatfish or trailing its arms to look like a sea snake. It performs, which leads straight into one of the strangest contradictions in all of biology. Because to copy a color, shouldn't you first be able to see it? Here is the part that stumped scientists for years. Octopuses are almost certainly colorblind. As far as we can tell, they see the world in shades of brightness, light and dark, not in color at all. And yet they match colors perfectly. Colors they shouldn't even be able to see. An animal painting itself to blend in with a reef, it experiences in black and white. For a long time that made no sense. Then in 2015, researchers found a clue that was hiding in plain sight. The same light-detecting proteins that an octopus has in its eyes are also scattered all over its skin. Even a piece of octopus skin, cut off from the body entirely, still reacts to light. In a very real way, the octopus doesn't just see through two eyes, it sees with its entire body. Its skin is studded with the same light sensors as its eyeballs. Some scientists think color change for an octopus might be a bit like breathing is for us. Something it can choose to do on purpose, but also something that can simply happen on its own, automatically, without a single conscious thought. A whole body that perceives, reacts, and disguises itself, sometimes without checking in with the brain at all. So we have an animal with its mind in its arms, three hearts, blue blood, no bones, and skin that can see. The obvious question is the one we opened with. How on earth did a soft, colorblind cousin of the snail ever become this? The answer is one of the strangest stories evolution has ever told. To find the last ancestor we share with the octopus, you have to go back around 600 million years, to a simple flatworm, drifting in an ancient sea, with barely any brain to speak of. After that point, our paths split for good. Everything intelligent about us, and everything intelligent about them, grew up on completely separate branches of the tree of life. Evolution didn't invent the mind once. It did it at least twice, in two totally different ways. And the octopus side of the family is old. Cephalopods, the group octopuses belong to, have been around for roughly 500 million years. These animals were thinking before there were trees, before there was anything alive on land at all. They were very likely the first truly intelligent animals this planet ever produced. The turning point came around 140 million years ago, when the octopus line did something risky. It gave up its shell. For a creature built like a soft water balloon, that should have been a death sentence in an ocean full of sharks. With no armor, no speed, and no shell to hide in, there was really only one way left to survive. Outthink everything trying to eat you. The vulnerability may be exactly what forced the intelligence. The octopus left its shell behind, and what it found on the other side was a bigger brain. This actually breaks the old theory of how minds evolve. For years we assumed big brains came from social life. Humans, dolphins, elephants, primates. We all live in complicated groups, and keeping track of friends and rivals, who owes you, who to trust, who to avoid, takes serious mental horsepower. The idea was that intelligence was basically a tool for handling each other. But the octopus is a loner. It mostly lives alone and hunts alone, with no family group to outwit. So its intelligence had to come from somewhere else entirely. From the daily grind of finding food, and not becoming food. Outsmarting the reef instead of outsmarting the neighbors. And if that's true, it means there is more than one road to a mind, which quietly rewrites a story we'd been telling ourselves about our own intelligence for decades. And the proof is everywhere once you look. There is an octopus that gathers up coconut shell halves and carries them across open sand. An awkward, exhausting job. Just so it has a shelter to climb into later. That means it is planning. It is imagining a future that hasn't happened yet. A skill we once thought belonged only to humans, apes, and a few clever birds. Or take Inky. In 2016, an octopus, named Inky, waited until night at an aquarium in New Zealand, slipped out through a small gap at the top of his tank, slid about 8 feet, roughly 2.5 meters, across the floor, found a drain pipe more than 160 feet long, which is around 50 meters, the length of a blue whale, and followed it all the way out to the open sea. Inky was never seen again. He didn't escape by accident. He solved it. And if you think rewriting the rules of intelligence is wild, wait until you hear what this animal does to its own genetic code. Think of your DNA as a fixed instruction book, locked in every cell, telling your body how to Your body never edits that book. Instead, it makes a working photocopy, called RNA, and reads off the copy to build proteins. Almost every animal on earth copies that book faithfully, word for word. The octopus does not. The octopus edits the photocopy on the fly, changing the instructions after they've already been written down. And it does this constantly, especially when the water turns cold. When the temperature drops, a two-spot octopus rewrites tens of thousands of spots in its own RNA. Scientists have counted over 20,000 editing sites changing at once, and it happens within hours. It's editing the very proteins that run its brain and its nerves. In plain terms, when the seasons shift, the octopus quietly retunes its own nervous system to match. Sit with that for a second. To pull this off, the octopus is going through something like a and changing thousands of words overnight, then changing them back when the water warms up again. You and I barely touch this trick. Our cells edit our RNA in only a tiny handful of places. The octopus does it on an industrial scale, all across the proteins that build its nervous system. Most animals are stuck reading whatever instructions they were born with for life. The octopus rewrites itself to fit the moment, then rewrites itself again when the moment changes. This is so unusual that medical researchers are now studying octopus RNA editing on purpose, hoping it might one day teach us new ways to treat disease in our own bodies. An animal that should be food for everything in the sea may end up helping rewrite human medicine, simply because it learned to rewrite itself first. Editing your own biology is lonely work though, and that fits because for 200 years we were absolutely certain the octopus was a loner. It turns out we had that wrong too. In 2024, scientists filmed something that rewrote the rulebook on octopus behavior. Octopuses were hunting in groups out in the open alongside fish. And the octopus wasn't just tagging along, the octopus was leading. The fish acted as scouts, fanning out to find prey, while the octopus reached into all the cracks and crevices the fish couldn't fit into. A genuine team made of completely different species working a reef together. But the best part is what happens when a fish slacks off. If a fish freeloads, just hanging around expecting a free meal without doing any of the work, the octopus punches it. An actual jab from an arm to keep the group in line. Researchers tracked 13 octopuses for around 120 hours of diving off the coast of Eilat to document it. The octopus, it turns out, runs a tight ship and does not tolerate dead weight. And the whole solitary creature label is falling apart. Off the coast of Australia, in two spots that biologists nicknamed Octopolis and Octlantis, gloomy octopuses live crowded together, 10 to 16 of them at a time, surrounded by dozens of dens. They meet. They signal to each other by changing color, going dark when they're feeling bold and pale when they back down. They chase off octopuses they don't like and evict each other from the best real estate. Researchers think these sites pop up where good hiding spots are rare and food is plentiful, so the animals end up tolerating neighbors they would normally avoid. It is, for all intents and purposes, a small octopus town, complete with arguments over property. They can even reach across the species barrier and communicate. A coral trout will point its whole body at prey hiding in a crevice, and an octopus understands the gesture and flushes the prey out. Two minds separated by more than 500 million years of evolution having something close to a conversation just by pointing. So the octopus was never really antisocial. Looking at all this, it almost seems like it just didn't like you. For all that intelligence, all that hidden society, all that genius for rewriting itself, this animal pays a price that is genuinely hard to read about, especially if it's a mother. An octopus gets exactly one shot at being a parent. A female reproduces a single time in her whole life, and that one event is the end of her. Once she lays her eggs, something shuts off inside her. She stops eating. She stops caring for herself. She does nothing but guard those eggs, cleaning them one by one, fanning fresh water over them, fighting off anything that comes near, slowly wasting away the entire time. Her body begins to fail while she works, and by the moment the eggs finally hatch, she is gone. She never meets a single one of the babies she gave everything for. She pours her whole life into a generation she will never get to see. For a long time, this looked almost like cruelty from nature. Then scientists traced it to a small gland sitting between her eyes, a kind of self-destruct switch. And in a famous experiment back in 1977, when researchers carefully removed that gland from brooding mothers, the spell broke. The mothers stopped starving. They started eating again. They gained weight. Some of them even went on to live nearly six more months. Left alone, that one little gland quietly ends her life on schedule the moment her job is done. And here is the loneliest part of all. Because she dies right as her young hatch, she can never teach them anything. Every octopus has to work out the entire world, all of that breathtaking intelligence, completely on its own, from scratch, with no parent to show it how. Yet even in the cold and the dark, there is tenderness in this story. Off the coast of California, about 70 miles out, roughly 110 kilometers and 10,500 feet down, which is around 3,200 meters, lies a place scientists named the octopus garden. Roughly 6,000 pearl octopus mothers gather there, nestled against warm volcanic springs, with maybe 20,000 nests in all. The warmth speeds the eggs along and gives the babies a better chance. And in a canyon near Monterey, scientists returned again and again to one deep-sea octopus mother and watched her guard her eggs for 53 months, more than four and a half years. She never left. She never ate. It is the animal on Earth is known to protect its young. And when they finally hatched, she died, exactly as she was built to. It makes you wonder which part of this animal feels the most alien to you. The brain spread out across its arms? Or a creature that rewrites its own genetic code? Tell me in the comments. I read them. So, is the octopus actually an alien? For years, a fringe idea floated around that octopuses really did arrive from space, riding in on a frozen comet. It is a fun story, and it has no real evidence behind it at all. The octopus didn't fall from the sky. Its origins are murky for a much simpler reason. Octopus and squid lineages split somewhere around 270 to 300 million years ago. And because soft bodies almost never turn into fossils, the deep past stays blurry. In fact, in 2026, scientists re-examined what was long called the oldest octopus fossil ever found, and discovered it wasn't an octopus at all. It was a relative of the Nautilus. The trail keeps going cold, but nothing about it points to the stars. And that is the wonderful part. This mind didn't come from another world. It grew up on ours, from the same little flatworm we came from, just down a completely different road. The philosopher and scientist Peter Godfrey Smith, who wrote an entire book about octopus minds, put it perfectly. Evolution, he said, built minds twice over. And meeting an octopus is probably the closest we will ever come to meeting an intelligent alien. Minds built twice, on one planet. We spent centuries staring up at the sky, scanning for a signal, wondering if any other kind of intelligence is really out there. And the first genuinely alien mind we ever met turned out to be eight-armed, three-hearted, colorblind, and quietly watching us back from a tide pool. We keep asking whether octopuses are aliens. Maybe the better question is the one they'd ask about us. If a mind this strange grew up right beside us, unnoticed, how many other kinds of And how many more are waiting on this Earth, or somewhere far beyond it? If you want to keep going down here in the deep, where the rules of biology keep bending, there's another creature waiting in the next video that may be even harder to explain than this one.