A thing has been making the rounds again — the claim that octopuses can rewrite their own genetic code while alive, have three hearts and blue blood and nine brains, and that scientists "still debate whether they truly belong here."
Most of it is true. One part is wrong in an interesting way. And the actual answer to *is the octopus an alien* turns out to be much better than the version going viral.
## What's true
**Three hearts.** One systemic heart that pushes oxygenated blood through the body, and two branchial hearts that pump it through the gills. If you ever watch an octopus swim, the systemic heart actually stops beating — which is part of why they prefer to crawl.
**Blue blood.** They run on hemocyanin, a copper-based oxygen carrier, instead of the iron-based hemoglobin we use. Copper plus oxygen reads blue. It works better than ours in cold, low-oxygen water and worse almost everywhere else, which is part of why they live where they live.
**Nine brains.** Directionally true. There's one central brain, plus a large cluster of neurons in each of the eight arms. Roughly two-thirds of an octopus's neurons live in its arms, and the arms can do meaningful processing on their own — a severed arm will still grab food and recoil from pain. Calling each cluster a "brain" is generous. The underlying fact is real: the octopus is partly a distributed system, with cognition pushed out to the periphery in a way no vertebrate would tolerate.
## What's wrong (and weirder)
The "rewrites its own genetic code" line is the one that gets garbled in every viral version.
Octopuses don't edit their DNA. They edit their **RNA** — the messenger molecules that carry instructions from genes to proteins — at a level no other animal comes close to.
Most species barely use RNA editing at all. Cephalopods recode something like 60% of the transcripts in their nervous tissue. They use this to fine-tune neural proteins on the fly, including in response to temperature. The trade-off is that heavy RNA editing locks the surrounding DNA into a conserved shape, which means cephalopods evolve their core genome more slowly than they otherwise would.
That's actually a much stranger thing than the viral version. They have *chosen a different layer of biology to be plastic on.* Vertebrates change their genome over generations and keep their proteins fixed. Octopuses keep their genome relatively still and let their proteins drift in real time. It's a different bet about where flexibility belongs in a nervous system.
If you build software, the analogy is interpreted vs. compiled. We're compiled. They're partly interpreted.
## The alien question
The "doesn't belong on the tree of life" line gestures at a 2018 paper by Steele et al. that proposed cephalopod genes might have arrived from space — panspermia, frozen embryos riding in on comets, the works. Almost no biologist takes it seriously. Cephalopods have a perfectly traceable Earth lineage going back to the Cambrian. The paper exists; it isn't right.
But here's the thing.
When you look an octopus in the eye, you're looking at a kind of intelligence that arrived independently of yours. The last common ancestor of humans and octopuses lived about 600 million years ago — something flat and worm-like with no real brain. Every neuron in your head and every neuron in an octopus arm developed along separate paths, solving similar problems with totally different hardware.
That's the actual answer to *is the octopus an alien*.
It isn't from another planet. It's from this one, evolved here, in our oceans, eating our crabs. But complex cognition on Earth has happened at least twice. The vertebrate version (centralized brain, hierarchical processing, lateralization) and the cephalopod version (distributed, arm-mediated, RNA-tunable) are the only two problem-solving, tool-using nervous systems we know about. They share an ocean and almost nothing else.
The octopus is a control experiment. It's what intelligence looks like when you grow it on different substrate.
If we ever do meet a real alien — if cognition is convergent enough to evolve elsewhere too — it will probably look more like an octopus than like us. Vertebrate-shaped is one solution. The universe is not obligated to favor it.
So: the post going around is directionally correct. Just for the wrong reason. The octopus isn't from another tree. It's from this one. It's just sitting on a branch most of us forget is there.