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Octopuses and humans share a distant evolutionary ancestor, but the evidence cited here does not establish that ancestor’s age as exactly 518 million years—or show that it explains cephalopod intelligence. Octopuses are molluscs and humans are vertebrates; their complex nervous systems evolved along separate branches, with strikingly different organization.
Is 518 million years the confirmed age of the human–octopus common ancestor?
No. The sources discussed here do not verify 518 million years as the precise date of the last common ancestor of humans and octopuses. A 2023 review describes cephalopod origins more than 490 million years ago, but that refers to early cephalopods, not to the date when the human and cephalopod lineages last shared an ancestor. Those are different evolutionary events.
The Max Delbrück Center describes the shared ancestor as a simple, wormlike animal. That distant relationship is real, but it does not mean the ancestor had a modern octopus-like or human-like brain. The exact 518-million-year figure should therefore be treated as unverified for this specific common ancestor, rather than as a settled scientific date.
What do octopus and human brains actually have in common?
Both lineages have nervous systems capable of complex behavior, but that similarity does not establish that their complex brains came from one complex-brained ancestor. A 2023 review discusses complex nervous systems as having evolved independently multiple times, including in cephalopods and vertebrates.
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Cephalopods include octopuses, squid, and cuttlefish. Their nervous systems are organized differently from vertebrate nervous systems. The resemblance between cephalopod and human camera-type eyes is another example of similarity that evolved independently, rather than proof that the animals share the same detailed anatomical design.
How is an octopus nervous system organized?
An octopus has a central brain and optic lobes, as well as extensive nerve cords running into its arms. In coleoids, the central brain is divided into supraesophageal and subesophageal masses, with optic lobes alongside it. Different regions are associated with functions such as learning and memory, motor control, and visual processing.
A 2023 review estimates that Octopus vulgaris has about 500 million neurons in total. Of these, about 200 million are in the optic lobes and central brain masses, while about 300 million are in the axial nerve cords of the arms. These are estimates for that species, not a universal count for every octopus. The distribution helps describe the animal’s unusual neural layout; neuron totals alone do not establish which animal is smarter.
What molecular changes might be related to cephalopod neural complexity?
MicroRNA families
A 2022 Max Delbrück Center account of work by Grygoriy Zolotarov and colleagues reported 42 novel microRNA families found specifically in cephalopod neural tissue, mostly in the brain. Their conservation was presented as evidence that the families may have functional importance. The finding offers a possible clue to cephalopod neural evolution, not proof that microRNAs alone caused intelligence or that humans and octopuses inherited complex brains from their shared ancestor.
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Other genomic changes
A 2015 Nature genome study reported expansions in protocadherins and C2H2 zinc-finger transcription factors, extensive RNA editing, cephalopod-specific genes, and genomic rearrangements. It found no evidence for the hypothesized whole-genome duplication in the octopus lineage. These are candidate pieces of an evolutionary explanation, not a settled single-cause account of cephalopod brain power.
Max Delbrück Center scientific director Nikolaus Rajewsky described the microRNA finding by saying, “So, this is what connects us to the octopus!” In context, the remark referred to expanded microRNA families; it should not be read as a claim that humans and octopuses share the same complex brain architecture.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How should the human–octopus comparison be understood?
| Comparison | Humans | Octopuses |
|---|---|---|
| Major lineage | Vertebrates | Molluscs; cephalopods |
| Nervous-system layout | Vertebrate brain organization | Central brain and optic lobes, with extensive nerve cords extending into the arms |
| What the evidence supports | Shares a deep evolutionary ancestor with cephalopods | Has a distinct nervous-system organization and molecular features researchers investigate in relation to neural complexity |
The comparison is most useful when it distinguishes shared ancestry from independent evolutionary change. A distant common ancestor links the lineages; it does not by itself explain the modern abilities of either animal.
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