If you wanted to design an alien, you could hardly do better than the octopus. It has three hearts, blue blood, nine brains by one count, and skin that can sense light and taste what it touches. It solves puzzles, escapes locked tanks, and holds a grudge. And it’s been here the whole time, in our own oceans.
Three hearts, and why it needs them
Two of an octopus’s hearts sit near the gills, pumping blood through them to grab oxygen. The third, central heart then sends that oxygen-rich blood to the body. Oddly, the central heart stops beating when the octopus swims — which is exhausting, and part of why octopuses usually prefer to crawl.
Blue blood is a deep-sea upgrade
Our blood is red because it carries oxygen using hemoglobin, which is built around iron. Octopus blood is blue because it uses hemocyanin, built around copper.
Copper-based blood is worse at carrying oxygen in warm, oxygen-rich water — but better in the cold, near-airless deep. In an octopus’s world, blue beats red.
That trade-off is exactly why the octopus needs three hearts: less efficient blood has to be pushed harder.
Nine brains, mostly in the arms
Here’s the strangest part. An octopus has a central brain, but about two-thirds of its neurons live in its eight arms. Each arm has its own bundle of nerves and can taste, feel, and react on its own — even reaching for food while the central brain is busy with something else.
Sever the connection and an arm will still recoil from danger. It’s less like one animal with eight limbs and more like a committee of nine minds that usually agree.
Skin that sees and tastes
Octopuses are colour-blind — and yet they’re masters of camouflage, matching colour and texture in a heartbeat. How? Their skin contains light-sensing proteins, so in a sense they can “see” with their whole body. Their suckers can taste whatever they touch, letting an arm identify a crab in a dark crevice without looking.
Add it up — distributed brains, chemical-tasting skin, colour-changing camouflage, tool use, escape artistry — and the octopus starts to feel genuinely other. The philosopher’s line has become a cliché because it’s true: meeting an octopus is about as close as we’ll get to meeting an intelligent alien, without leaving the planet.