It certainly seems that way. Rosenthal and Eisenberg found that RNA editing is especially rife in the neurons of cephalopods. They use it to re-code genes that are important for their nervous systems—the genes that, as Rosenthal says, “make a nerve cell a nerve cell.” And only the intelligent coleoid cephalopods—octopuses, squid, and cuttlefish—do so. The relatively dumber nautiluses do not. “Humans don’t have this. Monkeys don’t. Nothing has this except the coleoids,” says Rosenthal.

It’s impossible to say if their prolific use of RNA editing is responsible for their alien intellect, but “that would definitely be my guess,” says Noa Liscovitch-Brauer, a member of Rosenthal’s team who spearheaded the new study. “It makes for a very compelling hypothesis in my eyes.”

Chambered nautilus. (Michael Bentley / Flickr)

Here’s how RNA editing works. Genes encode instructions in the form of DNA—in the sequence of four building blocks represented by the letters A, C, G, and T. For those instructions to be used, the DNA must first be transcribed into a similar molecule called RNA, which contains roughly the same building blocks. The RNA is then translated and used to build proteins—the molecular machines that carry out all the important jobs inside our cells. So DNA stores information, RNA carries it, and proteins are the result of it.

That’s the simple version. But the RNA often gets altered before it’s used to make proteins. Some of the changes are big—large sections are cut out, and the remaining pieces are glued back together. Other changes are small—sometimes, a single A gets converted into an I (which is functionally equivalent to a G). That’s RNA editing. It’s performed by a group of enzymes called ADARs, which recognize specific sequences of RNA and makes those A-to-I changes.

But to what end? RNA editing is still mysterious, and its purpose unclear. Technically, an animal could use it to change the nature of its proteins without altering the underlying DNA instructions. But in practice, this kind of recoding is extremely rare. Only about 3 percent of human genes are ever edited in this way, and the changes are usually restricted to the parts of RNA that are cut out and discarded. To the extent that it happens, it doesn’t seem to be adaptive.

In cephalopods, it’s a different story. Back in 2015, Rosenthal and Eisenberg discovered that RNA editing has gone wild in the longfin inshore squid—a foot-long animal that’s commonly used in neuroscience research. While a typical mammal edits its RNA at just a few hundred sites, the squid was making some 57,000 such edits. These changes weren’t happening in discarded sections of RNA, but in the ones that actually go towards building proteins—the so-called coding regions. They were ten times more common in the squid’s neurons than in its other tissues, and they disproportionately affected proteins involved in its nervous system.