“The octopus is a stupid creature, for it will approach a man’s hand if it is lowered in the water,” the ancient Greek Philosopher Aristotle famously wrote over 2,300 years ago. By now, we know better though.

Octopuses are some of the most bizarrely fascinating creatures on Earth. Not only are they smart, adaptable, and cunning, but they show a remarkable capacity for empathy as well. Plus, their undeniable intelligence is very different from the intelligence of other creatures, which is why many consider them to be the closest thing you can see to an alien.

If you’re fascinated by octopuses, you’re not the only one — scientists are also intrigued, as highlighted by some of the studies they’ve been publishing. Read on and prepare to have your mind blown.

Each arm has its own mini-brain that can make decisions

Having a brain is a big deal in itself, but how about having nine?

Researchers have long suspected that octopus arms have a mind of their own but proving it is a completely different thing. Still, a 2019 study managed to prove just that, showing that the arms can send information to each other while bypassing the brain, basically showing an alternative model to intelligence than the centralized version we have ourselves.

The octopus’ arms have a neural ring that bypasses the brain, and so the arms can send information to each other without the brain being aware of it,”said Dominic Sivitilli, author of the study. “So while the brain isn’t quite sure where the arms are in space, the arms know where each other are and this allows the arms to coordinate during actions like crawling locomotion.”

They can change their genetic code

We’ve all had a cold. What do you do when you get a cold? You rest, drink lots of fluids, that sort of thing. What does an octopus do when it gets a cold? It changes its RNA to beat the cold.

Octopuses and their relatives (the cephalopods) practice a type of RNA editing that is extremely rare in the animal kingdom, fine-tuning the information encoded by their genes without changing the genes themselves — and they do so to a much greater extent than any other group of animals.

It’s hard to say whether this unusual ability is linked to their alien-like intelect, but Noa Liscovitch-Brauer, one of the researchers who worked on the study, told The Atlantic that “It makes for a very compelling hypothesis in my eyes.”

They build cities (or villages)

Surely building settlements is something that only humans can do on Earth, right? Well, think again! In 2017, researchers were stunned to find another octopus settlement.

We say another because the first octopus city was found in 2009, but when researchers found that one, they thought it must be a freak occurrence. The theory was that the Octopolis was created only due to an unidentifiable human object which formed a central point that the cephalopods surrounded with dens. But when they found a second, similar settlement, there could be no more talk of freak accidents.

The city isn’t that big, measuring 18 by 4 meters (59 by 13 feet) and lying 10 to 15 meters (33 to 49 feet) underwater. So it’s really more like a village than a city, but that doesn’t make it any less interesting. It comprises 16 individuals who have constructed dens from sand and shells. Remarkably, these neighbors show complex interactions and aren’t always friendly — they even chase and attack each other once in a while. It’s not clear why octopuses build villages.

They can rip off poisonous tentacles from other creatures and use them as weapons

Using tools is a clear sign of intelligence, and octopuses mastered that a long time ago. They can use coconut shells, discarded human objects, and all sorts of things they find on the ocean floor as tools. But they do something way cooler.

The blanket octopus rips poisonous tentacles from the Portuguese Man o’War and uses them as weapons. The Portuguese Man o’War resembles a jellyfish but it’s actually a colonial organism that drags behind it several long tentacles that deliver a powerful venomous sting to fish.

The blanket octopus is immune to the venom, but it seems to be aware that most creatures are not — so it rips off the tentacles from the Portuguese Man o’War and carries them around, using them as weapons. Biological weapons are not unavailable to octopuses.

They can dream and change color when they do

A few years ago, a video of an octopus named Heidi became viral. Heidi was sleeping and changing colors; quite possibly, she was dreaming.

Not everyone was convinced of this idea (and to be fair, some people still aren’t), but recent research suggests that octopuses have alternating sleep states and could have fleeting dreams.

Proving that an animal dreams is one of the hardest things to do but increasingly, research is showing that some animals (including octopuses) have alternating sleep states similar to humans and are quite likely to have dreams as well.

They love to play and can get bored or annoyed

Juggling your aquarium flatmates, smashing rocks against the glass, and turning off the power by short circuiting a lamp — Otto the octopus went on quite a spree because he was bored.

“We knew that he was bored as the aquarium is closed for winter, and at two feet, seven inches Otto had discovered he was big enough to swing onto the edge of his tank and shoot out the 2000 Watt spot light above him with a carefully directed jet of water,” said a spokesperson for the Sea Star Aquarium in Coburg, Germany, where this happened. Otto is constantly craving for attention and doing stunts to get what he wants — one time, he threw rocks at the aquarium glass; another time, he started juggling crabs from his aquarium; and sometimes, he arranges things in the aquarium to his liking, much to the chagrin of his fellow inhabitants.

Otto isn’t nearly the only octopus to do this. Octopuses love to play and they get bored when they have nothing to do — yet again, two clear hallmarks of higher intelligence. Their personality also plays a role: some love playing more than others, and some can be a bit mischievous, like Otto.

They can recognize humans — and be nice or mean to them

Octopuses have large eyes and while they are color blind, their well developed visual system allows them to see excellently underwater and they have no blind spots. Octopuses also seem able to visually differentiate between members of their species, which is rare but not unique. But more impressively, they also seem able to differentiate between people — and remember them.

For instance, an octopus from the University of Otago in New Zealand took a dislike to one of the staff members, and every time the staff member would pass by the tank, the octopus would squirt a jet of water at her.

In a more controlled experiment, biologists at the Seattle Aquarium showed that octopuses can recall who feeds them and who is mean to them. They also seem to appreciate when people try to communicate with them.

They can perceive light through their skin

Octopus skin contains a light-sensitive pigment that’s also found in their eyes. In other words, they can “see” (or rather, perceive light) with their skin.

These clever creatures can change color based on their surroundings, using specialized cells called chromatophores. But these cells do even more than just changing color.

Basically, as environmental light hits the skin of the octopus, the light can stimulate the expansion or contraction of these chromatophores. The cells also react to mechanical touch, and it’s not clear if they evolved this way as a response to light, mechanical touch, or both.

They share some of our intelligence genes

Octopuses and humans don’t have much in common biologically, but we do share one important thing: jumping genes.

So-called jumping genes, or transposons, make up 45% of the human genome. These genes are short DNA sequences that have the ability to copy and paste themselves to another location in our genome. In octopuses, like in humans, they have also been detected in areas of the brain linked to behavioral plasticity — adaptability. This is a sort of confirmation that octopuses are adaptable, and the similarity to humans is striking.

In fact, one of the researchers working on the study ‘literally jumped on the chair’ when they noticed activity in the octopus’ vertical lobe — the structure that is their seat of learning and cognitive abilities (sort of like how the hippocampus is for humans).

They’ve learned how to use the litter from the ocean floor

Using tools is one thing, but adapting to using man-made litter is a different challenge, one that octopuses pass with flying colors.

Stuff sinks down in the ocean, and a lot of that is our fault — because the stuff that sinks down is often pollution. That’s obviously bad for wildlife, but some creatures (you can probably guess which ones) have actually learned to use that to their advantage.

Octopuses have been found using litter (mostly for defense) several times, and they’re able to use a large variety of objects: from cans and bottles to glasses and even batteries. They use the litter for camouflage for themselves or for laying eggs. However, hiding or laying eggs among plastic and chemical pollution could expose octopuses to harmful chemicals.

They can pull themselves out of the water and walk on land

It may seem crazy, but most species of octopus can survive out of water for 30-60 minutes, and they often use this ability.

Basically, octopuses use their tentacles to walk on land if they get trapped in a low tide, or if they are chased by predators — sometimes, even to find their own prey.

Remarkably, this doesn’t only happen in the wild. Inky, a male common New Zealand octopus, escaped his enclosure through a small opening, slid across the floor when no one was watching, and squeezed his body through a narrow pipe leading to open waters.

They’re older than the dinosaurs

There’s an octopus fossil from a period called the Carboniferous, some 296 million years ago — for comparison, dinosaurs appeared 252 million years ago. But that’s not even the oldest one we know. The oldest known octopus comes from around 329 million years ago and had 10 arms.

They can feel emotional pain

When we talk about pain, we don’t just refer to a simple reflex reaction to something harmful — pain also involves an emotional component, and octopuses seem to experience it as well.

A 2021 study showed that octopuses feel pain much like mammals do, supporting the case for establishing welfare regulations for these animals.

While again, this is very hard to prove beyond the shadow of a doubt, a growing body of research hints at the complex emotions that octopuses feel. If they can feel bored, curious, or annoyed, it’s hard to argue that they don’t have emotions.

Despite all this, some people want to farm and eat them

We’re still only starting to understand them — perhaps this is the craziest thing of all. We’ve known octopuses for thousands of years, but we’re still just scratching the surface of their cognitive abilities. A hundred years ago, most people would have likely agreed with Aristotle, but now we know much better. Even just two decades ago, our understanding of them was completely different, and it’s changing with every study and observation.

There are more than 300 different species of octopus that we know of, and many (if not all) seem to have such a developed intelligence. But octopuses are in trouble. Seriously threatened by pollution, overfishing, and loss of habitat, most species are struggling. Their decline is accentuated by the fact that their food is also severely threatened.

To make matters even worse for octopuses, there are growing calls to build octopus farms. Just now, when we are learning that octopuses feel emotions and have culture, we want to grow them as meat animals. “It is exactly the wrong moment to propose such a scheme. We now know better,” wrote Professor of Philosophy Kristin Andrews in an article for The Conversation.

If you’re looking for more information about octopuses, there are a lot of studies and articles out there, as well as several books and documentaries. In fact, My Octopus Teacher, one such documentary, was awarded the Oscar for Best Documentary. The world of octopuses is complex and surprising. We’d be wise to pay attention.