the world are as remarkable and bizarre. A part of a class of animals called cephalopods,

they are among the most intelligent and most mobile of all the invertebrates. They live

in every ocean in the world, in the deep sea, in kelp forests, in coral reefs, along rocky

shorelines. And they are as diverse as the habitats they live in. They can be massive,

or absolutely tiny. Some species are venomous, and some are just downright strange. In any

given moment, they can appear spikey, or they can appear smooth. They are so different from

us, that most of their 500 million neurons are not in their brain, but in their arms,

which can smell and taste, and even think. And so intelligent that their cognitive ability

matches that of many large-brained vertebrates.

They have left scientists stunned about how a creature so far from us on the evolutionary

tree could evolve such complex behaviors, their intelligence emerging in an entirely

novel and independent way from our own.

So how did the octopus become so biologically complicated - an island of complexity in the

sea of invertebrate animals? Just how intelligent are they, and how can studying them reveal

information about our own minds?

Cephalopods have been around for a long time. Fossil records show that they evolved over

500 million years ago - long before any fish, reptiles, or mammals appeared on earth. The

early ancestor of the octopus was quite small and had a shell, which it used to protect

itself as it crawled along the ocean bottom. Cephalopods are, after all, members of the

mollusk phylum. A group of creatures that are usually slow and simple, with soft bodies

and a hard protective shell - like snails, clams, and oysters. But around 140 million

years ago, the lineage that produced the octopus lost their shells, making them nimble, agile

creatures, but in the process also made them rather vulnerable. Survival of these soft

bodied creatures for so many millions of years therefore seems unlikely in a sea full of

dangerous, hungry predators. But this vulnerability and selective pressure may be precisely what

has allowed the octopus to become the remarkable creature we know today.

Because an octopus has almost no hard parts at all, except its beak, it can squeeze through

any hole as long as it's larger than its eyeball. This allows the octopus to hide in

very small crevices - a certain evolutionary advantage when escaping large predators like

sharks or dolphins. But, the soft-bodied octopus evolved an even more clever way of evading

detection: they are masters of disguise.

Watching this clip of an octopus, you can see just how quickly and drastically it can

change colors. In slow motion reverse, you see the color change spread across its body.

The 3D texture of the skin also changes, to match the surrounding seaweed and coral. In

the blink of an eye, it has almost completely blended in with its surroundings. Cephalopod

camouflage is among the most dynamic in the animal kingdom, and relies on a system of

extremely sophisticated tissues.

Chromatophores are organs that are speckled across the skin of the octopus, like freckles.

They contain tiny pigment filled sacs, like little balloons full of different color dye,

which can be black, red or yellow. The pigment sacs are surrounded by radial muscles, which

can stretch the sac to reveal the pigment's color. Just like balloons full of dye, when

stretched, their pigment color appears bright and vibrant. Depending on which sets of sacs

an octopus opens or closes, it can produce patterns such as bands, stripes, or spots

- helping to turn itself into a rock, a coral, or kelp in an instant.

But if the octopus needs to produce colors outside of black, red, and yellow, it uses

another layer of reflective structures in their skin called iridophores. They are stacks

of very thin cells that lay beneath the chromatophores. They contain a protein called reflectin that

bounces certain wavelengths of light back out. They are responsible for the metallic

blues and greens that appear to shimmer on the skin of the octopus.

Beneath that layer is yet another layer of reflective tissue, called leucophores. These

reflect ambient light, usually producing white hues. By combining reflection from the iridophores

and leucophores with the correct patterning of chromatophores, the octopus can create

a very convincing copy of its surroundings.

But the octopus has one more trick up its sleeve, allowing it to disappear in plain

sight almost completely. Using a structure called papillae, it can change the texture

of its skin, creating ridges and bumps that rise and fall. This helps the octopus match

its surroundings even better. It also gives them a less identifiable edge. Many vertebrate

predators find their prey by looking for visual edges and breaks in the background, and this

tactic disrupts that very effectively.

With all these tools, the shell-free, soft bodied octopus has been able to deceive an

ocean full of predators for millions of years. But, their survival has not hinged on these

camouflage properties alone. It is the way they are controlled that is perhaps an even

more compelling survival tool.

When an octopus travels along the seafloor, they have to assess the background and modify

their camouflage constantly. They are making decisions at a rapid pace - one researcher

observed an octopus changing its camouflage 177 times in 1 hour. Octopus's camouflage

reaction times are faster than any other animals', - up to 200 milliseconds, as fast as the fastest

blink you can do.

But despite doing so much with color, the octopus, and almost all cephalopods, are surprisingly

thought to be colorblind. How can they match colors they can't even see?

In 2015, the answer to this question started to be uncovered. Researchers found that the

skin of an octopus is sensitive to light, due to photoreceptor genes active in the skin.

Even when the skin was detached from the body, it could respond to light and change the shape

of its chromatophores. Scientists realized that an octopus can see with not just its

eyes, but also its skin.

But as the octopus body was evolving its color changing defense mechanisms when it lost its

shell 140 million years ago, another transformation occurred: the development of its large brain

and nervous system. The photoreceptor genes in the skin work in connection with the octopus's

large and complex brain. The octopus can change color so fast, because the octopus controls

its chromatophores neurally. Other animals that can change color, like chameleons, for

example, take much longer because their color change is hormonally controlled. Hormones

take time to get into the blood and distribute around the body. A color change can take over

20 seconds when controlled this way.

Some researchers believe that color change in the octopus may be like breathing or blinking

for us- something it can choose to do, but also something that can happen involuntarily.

It can have awareness from its eyes and brain, but also throughout its body.

The octopus nervous system is large like ours, but built with a different relationship between

body and brain all together. The common octopus has around half a billion neurons in its body.

For comparison, humans have about 100 billion. Most invertebrates usually have much less.

Snails have only 20,000. But cephalopods like the octopus score in the same range as many

vertebrates, like cats and dogs and parrots - more than any other invertebrate

And of their 500 million neurons, only a third are found in their brain. The majority are

found in their eight arms. And as strange as it sounds, this allows the octopus to in

a way, think with its arms.

For a long time, scientists have known that a severed octopus arm can respond to stimuli

an hour after being separated from the central brain. But a paper last year began to reveal

the extent of this autonomy. Using video modelling they observed the octopus as it explored objects

in its tank and looked for food. The program quantified movements of the arms, tracking

how the arms work together in synchrony, suggesting direction from the brain, or asynchronously,

suggesting independent decision-making in each appendage. And they found that in the

flow of information from the environment to the octopus, some information bypasses the

central brain entirely. The suckers and arms can, in a way, think for themselves, allowing

the octopus to analyze its environment extremely quickly, and react with matching speed. Along

with skin that can perceive and change color on its own, the relationship between brain

and body in the octopus is full of blurred lines.

And on top of this unusual neural layout and strange body autonomy, cephalopods are smart

- extremely smart - and this is really what gives the octopus its alien-like status. They

are so far from any other intelligent life on the tree of evolution, but still compete

with vertebrates in their raw cognitive ability. Evolution invented intelligent life not once,

but twice, in two completely different ways.

In the evolutionary tree of life, we sit upon the branch of mammals. Nearby are the fish,

reptiles, birds, amphibians - the other members of the larger classification of vertebrates.

This group is where we see all of the 'intelligent' life we normally think of - humans, primates,

dogs, cats, dolphins, and some birds. When we collect these animals and trace back to

our common ancestor, it was likely a lizard-like animal that lived around 320 million years

ago. Like us, this animal would have had a backbone, four limbs, a head, and a skeleton.

It would have walked around, well adapted to land, and had a well developed central

nervous system.

But to find where we split from the octopus, we have to travel much further down the branches

- to around 600 million years ago. The creature we find there is a simple, flat worm. It had

an extremely basic nervous system, and no inklings of what we would consider 'intelligence.'

As the evolutionary tree branched and diverged, intelligence blossomed on our branch of vertebrates,

and totally separately, in the cephalopods. [7] And, with the cephalopods evolving before

any of the intelligent vertebrates, it's likely that they were the first intelligent animals

that appeared on earth.

But what actually is 'intelligence? How can we identify - or even measure - such a

thing in an animal so different to us?

In humans, intelligence is commonly defined as the ability to think abstractly, understand,

communicate, problem-solve, learn, form memories, and plan actions. This is usually measured

by intelligence tests which can be given a numerical value. But, we can not give a standardized

test to an octopus. We can only observe their behaviors.

- “they're the most interesting mollusks in

terms of behavior. No question.”

To learn more about the depth of octopus intelligence as researchers currently understand it, I

spoke with Jennifer Mather, professor in the Department of Psychology at University of

Lethbridge - and scientific advisor for the film My Octopus Teacher.

“every learning task you give them they can do. Short term, long term spatial memory,

object perception. But it's more than learning. They also go in for planning. And planning

is not so obvious.

One of the famous examples is what's been called a coconut carrying octopus. So the

octopus is going off to a place where there's no shelter. And it takes these coconut halves

with them. And when it wants to stop and rest, it picks them up and brings them up like this

around it. It's amazing.”

Some scientists argue that this behavior is a rare example of composite tool use - a behavior

previously thought to only exist in humans, some primates, and some birds. And it may

be evidence of complex intelligence for two reasons. First, this tool use might represent

a behavioural innovation allowing octopuses to protect themselves in areas where they

cannot otherwise hide. Second, because the coconut shells are transported, with great

effort, to meet future needs this behaviour might indicate an octopus's planning ability.

The octopus has to imagine the future and connect the dots between past events, current

actions, and future events, which is not a simple task.

Octopuses also do well in memory tests, and can differentiate between different people,

even when they are wearing the same outfit. Octopuses are also great problem solvers.

For instance, they remove lids from jars and open opaque boxes to acquire hidden prey.

And, in a study done by Professor Mather, the common octopus has also been shown to

be extremely playful.

I would describe them as extremely exploratory, sort of like a five year old kid, taking stuff

apart, going off and feeling around with the landscape, just grabbing more information.

Play is often defined as a behavior that is not necessary for survival, done on purpose,

but seemingly for pleasure. The action is often repeated, exaggerated, and carried out

when the animal is adequately fed, healthy, and not under stress.

“We figured that the animals are more likely to play if they're safe and bored. So we

set up octopuses in an aquarium with a place to hide, and nothing else. And then we got

a pill bottle, put enough water in it, but it floated at the surface.

Also in the mix was a water intake pump for the aquarium that the researchers hadn't

necessarily intended to be part of the experiment. It created a current that pushed the pill

bottle across the top of the tank, which sparked the curiosity of some of the octopuses.

So we did this with six animals, okay, in two cases, the pill bottle came across like

this. The octopus shot a jet of water at it, which meant that it went back towards the

water intake and it came back again.

If an octopus did this once, or even twice, it would not be experimentally significant.

But a few carried out this behavior so many times that it couldn't be ignored.

one of them did this, I think it was 14 times. And one of them did it 21 times.

it was the marine equivalent of bouncing the ball!

In addition to helping establish motor coordination, play in most species is largely needed for

social purposes - for establishing social rank, for learning social rules, or for social

bonding. And due to its complexity, play is considered to be almost exclusive to mammals,

with a few exceptions in other vertebrates like some birds.

But the octopus is a solitary creature. It has no social bonds, no social hierarchy.

It makes us rethink the evolutionary reasons for play. In fact, much of our idea of intelligence