Why Are Some Octopuses So Smart? The Answer Might Lie in a Never-Before-Seen Mutation That Helps Them Accurately Build Proteins

One species, the common blanket octopus, wields venomous tentacles ripped from the Portuguese man o’ war as weapons. Now, researchers have discovered a mysterious mutation in some octopuses that might explain their intelligence. A study published in the August 17 issue of the journal Current Biology reveals that the eight-limbed creatures can produce proteins with extreme accuracy thanks to a variation never seen in any other animal.

Although there is no direct evidence that the adaptation is linked to expanded octopus brainpower, only a lineage of creatures with enlarged nervous systems and can carry out complex behaviors appears to have the mutation. Scientists made this discovery by accident. About five years ago, study co-author Richard Han, then a graduate student at Harvard Medical School, was examining molecules called ribosomal RNA (rRNA) in tissues from the California two-spot octopus.

The molecules create a 3D scaffold for ribosomes, the cells’ protein factories. Many sequences of rRNA remain pretty much the same across all known animals. But Han noticed something unusual in those from the octopus: an unexpected gap that broke what’s usually one rRNA fragment in other creatures into two.

Further tests, however, confirmed that something else was going on. Inserting the same break in the ribosomes of Escherichia coli bacteria made the engineered cells produce proteins with about twice their usual accuracy. To examine when the strange rRNA feature evolved, the team compared two groups of octopuses that diverged more than 100 million years ago: incirrates, shallow-water octopuses with developed nervous systems that support complex behaviors, and cirrates, deep-sea creatures with simpler nervous systems adapted for slow swimming and passive feeding.

The rRNA break was present in all five examined incirrate species, the team found. But a sample from a cirrate—specifically, a dumbo octopus—lacked the gap. Squids, which diverged from octopuses about 300 million years ago, also didn’t have it.

Cephalopods, an animal group that includes octopuses, squids, cuttlefish and nautiluses, are masters of editing their own RNA—molecules that carry instructions from DNA to help build proteins. They do it far more often than other creatures do. In a study published in 2023, researchers reported that octopuses heavily edit RNA in their brains to brave frigid water.