Most of its brain is in its arms.

Distributed mind

A creature that doesn't keep its thoughts in one place.

Of an octopus's roughly half a billion neurons, about two-thirds sit in the eight arms rather than the central brain. Each arm carries its own dense bundle of nerve cells and a real measure of independence — it can reach, taste, grip and recoil on local information, and a severed arm will keep reacting for a while on its own.

So the octopus may not so much command its arms as negotiate with them. We each experience a single seat of self, looking out. Its selfhood seems smeared across its body, eight semi-autonomous explorers loosely held together as one animal.

of its neurons live in the arms, not the head

The colorblind painter

It rewrites its own color while being unable to see it.

An octopus has a single type of photoreceptor, which by the standard definition makes it colorblind. And yet its skin is one of the most sophisticated color displays in all of nature: millions of tiny pigment sacs called chromatophores that it opens and closes muscle by muscle, layered over cells that scatter light into iridescent blues, greens and brilliant whites.

How a colorblind animal blends so exactly into a reef is still genuinely debated. One elegant idea: the odd, off-center shape of its pupil smears different wavelengths into focus at slightly different distances, letting the octopus read color out of the blur instead of from cone cells. Its skin itself may even sense light directly.

Taste by touch

Every sucker is a kind of tongue.

The rim of each sucker is studded with receptors that do something we have no clean word for: they taste by touching. An arm reaching blindly into a dark crevice samples the chemistry of whatever it brushes — sorting prey from rock from something venomous — without the octopus ever needing to see it.

In 2020, researchers identified a whole new family of these chemo-tactile receptors, found nowhere else in the animal kingdom. Spread across roughly two thousand suckers, it means an octopus is, in a sense, tasting the entire world it holds all at once.

Self-editing code

It edits its own genetic instructions on the fly.

Nearly every animal reads its DNA faithfully into protein. Octopuses and their cousins instead rewrite their RNA on a vast scale, recoding tens of thousands of sites — and the editing is concentrated in the nervous system, exactly where flexibility matters most.

They even retune those edits to the temperature of the water, quietly adjusting the proteins of the brain to suit the cold. It's a form of plasticity written one rung below behavior, in the genetic code itself — and it may be part of the price they pay in mutation rate to stay this strange.

Tools, jars & escapes

It plans, improvises, and occasionally just leaves.

A coconut octopus gathers discarded shells and carries them awkwardly across the open seabed to reassemble as armor later — hauling a tool for future use, which is a serious benchmark of cognition. In tanks, octopuses open childproof jars, solve mazes, recognize individual keepers, and reportedly hose down the ones they dislike with a jet of cold water.

And in 2016, an octopus named Inky apparently waited for the quiet of night, squeezed out through a small gap at the top of his tank, slid across the floor, and poured himself down a drainpipe straight back to the sea.

Brilliant & brief

All of this lasts only about two years.

Here is the part that stays with me. For all of that intelligence, most octopuses live just one or two years and die soon after reproducing. A female stops eating to guard her eggs and fades as they hatch; a small gland behind her eyes runs the countdown.

So the smartest invertebrate on the planet has almost no time to be smart, and no elders to learn from. Each generation reinvents its genius from scratch, alone — and then is gone.