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Gallipoli, Canakkale, Turkey; close up of an octopus eye (Octopus vulgaris Cuvier, 1797). Generative AI
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Octopus Intelligence Shakes Up Darwin’s Tree

There does not seem to be a Tree of Intelligence, which deepens the mystery of intelligence

(This article was first published in Salvo 64, Spring 2023, as Spineless Wonders.)

The octopus presents a conundrum in animal intelligence: A highly intelligent invertebrate.

Common octopus in large sea water aquarium

We used to live in tidy world, where vertebrates, with backbones terminating in a brain, were more intelligent than invertebrates, with a variety of nervous system layouts and structures (or, in many cases, little or none thereof). Mammals and birds are, of course, highly favored for intelligence because they are warm-blooded (endothermic), and the brain is a high metabolic area. The traditional “tree of intelligence” makes sense, actually.

But then we got to know the octopus.

A “Second Genesis”

Called by some a “second genesis of intelligence”, the octopus is the hero or perp of many animal lab stories that would otherwise have featured, say, a dog or a chimpanzee. Here’s one: At the Sea Star Aquarium in Coburg, Germany in 2008, staff were puzzled when the electrical system shorted out two mornings in a row. The third night, when they took turns sleeping on the floor, they found the culprit: Otto, a six-month-old octopus. “He had crawled out of his tank and, using his siphon like a fire hose, aimed it at the overhead light. Apparently, it annoyed him or maybe he was just bored. As director Elfriede Kummer told The Telegraph, ‘Otto is constantly craving for attention and always comes up with new stunts… Once we saw him juggling hermit crabs in his tank.’”

The octopus brain is nothing like the mammal brain. The octopus has a central brain in its head, but each of the eight arms has a smaller “brain” to co-ordinate movement among the limbs and to manage the flow of information from the hundreds of suckers that work like thumbs.

Scientists clash over how octopuses got to be so smart. We can say, of course, that’s easy! They need to be smart in order to control all those limbs. But not so fast. Many life forms have many limbs. The less intelligent ones use their limbs for more mundane tasks than opening jars, as octopuses can do.

The fact that the octopus benefits from intelligence doesn’t automatically cause it to have intelligence. Many life forms that would benefit from greater intelligence, sadly, do not have it. Some have probably gone extinct on that account.

The octopus does not even live like a life form that we would expect to be intelligent. Most intelligent life forms — chimpanzees, elephants, whales, dolphins, crows, and parrots — are social animals that live a comparatively long time. The octopus, by contrast, is generally a loner who, to quote science writer Ed Yong, lives fast and dies young: “Most have life spans shorter than two years, and many die after their first bout of sex and reproduction.” Not only that, but whereas the chimpanzee’s relatives are mostly other smart primates, the octopus’s relatives include oysters, mussels, snails, slugs, nautiluses, and clams. Closer relatives, squid and cuttlefish, seems to be somewhat intelligent as well, though they have not been studied as much.

How did the octopus get to be so smart?

One hypothesis is that, in giving up its shell, the octopus had to become smart in order to survive. Almost every group of ocean predators eats octopuses and other cephalopods. The problem, says a critic, is that an octopus without a shell must avoid being eaten while still developing the intelligence to adopt other strategies. Thus, the intelligence must have preceded the loss of the shell. But then why would it have developed at all?

Researchers think they may have some clues as to how the intelligence developed, if not why. The octopus and the squid have very elastic genetic codes, relative to many similar life forms. A study of two species of squid showed that their genomes were highly rearranged. As one researcher put it, “You have this mosaic of chromosomes, where ancestral chromosomes were broken up and pieces randomly fused to each other, forming new chromosomes.” It’s suggestive that “jumping genes” (genes that move from one point to another) are as active in the cephalopod brain as in the human one. Octopuses have an exceptionally large number of microRNAs (miRNA) which affect genes after they have developed, a characteristic they share with vertebrates. From a media release for a miRNA study:

“This is the third-largest expansion of microRNA families in the animal world, and the largest outside of vertebrates,” says lead author Grygoriy Zolotarov, MD, a Ukrainian scientist who interned in Rajewsky’s lab at MDC-BIMSB while finishing medical school in Prague, and later. “To give you an idea of the scale, oysters, which are also mollusks, have acquired just five new microRNA families since the last ancestors they shared with octopuses – while the octopuses have acquired 90!” Oysters, adds Zolotarov, aren’t exactly known for their intelligence.

Identifying genetic traits in the octopus that are associated with intelligence doesn’t tell us how or why it came to be unusually smart, but they are a promising research avenue for animal intelligence in general.

Do octopuses feel pain or emotion?

First, how would we know? When researchers applied the same sentience criteria to octopuses as to dogs, they found strong evidence of sentience. So either dogs don’t feel pain or octopuses do. Another researcher put octopuses through the same pain awareness test as is used on lab rats: “Using detailed measurements of spontaneous pain-associated behaviors and neural activity, [Robyn] Crook has identified three lines of evidence that all indicate octopuses are capable of feeling negative emotional states when confronted with pain. These are the same characteristics that mammals show, despite the fact that the octopus nervous system is organized in a fundamentally different way to vertebrates.”

One recently observed trait, which suggests both intelligence and emotion, is octopuses throwing things at each other: “Underwater cameras captured the cephalopods collecting shells, silt and algae with their arms and hurling them at one another by using jets of water from their siphon to propel the scraps. The researchers even observed the receiving octopuses ducking to avoid a hit.” Unfriendly? However smart, octopuses are antisocial loners and not above cannibalism.

Should we eat octopuses?

Farming octopuses — octoculture — would provide a stable living for poor people in the many regions where the octopus is a delicacy but where ocean numbers are down. However, some researchers have spoken out against it for ethical as well as environmental reasons. That’s a sticky one. In the Western world, we eat pigs, considered highly intelligent, but we draw the line at dogs, cats, and chimpanzees.

In any event, the British government is now moving to protect octopuses from cruelty — as it would protect, say, pigs or cows:

Grilled octopus in cast iron grill pan.

Dr Jonathan Birch, Associate Professor at LSE’s Centre for Philosophy of Natural and Social Science and Principal Investigator on the Foundations of Animal Sentience project, said:

“I’m pleased to see the government implementing a central recommendation of my team’s report. After reviewing over 300 scientific studies, we concluded that cephalopod molluscs and decapod crustaceans should be regarded as sentient, and should therefore be included within the scope of animal welfare law.”

The Intelligence Enigma

If our moral compass expands to include octopuses, it nonetheless leaves us with some pointed observations and nagging questions: There does not seem to be a tree of intelligence, which deepens the mystery of intelligence. How exactly does a life form acquire the ability to process large amounts of information and use it to make intelligent decisions (and perhaps end up feeling pain as an inevitable outcome)? And why does intelligence (and sentience) develop strongly in one life form but not another, related one?

If intelligence was a fluke when generated among birds and mammals, what about the fact that it was generated again in the octopus, a neurologically very different life form? Flukes that repeat themselves may be forming a pattern, though it might take considerable research to determine what it is.

Scientists clearly enjoy tackling this mystery, but they should be careful. Some treasured evolutionary assumptions about randomness and meaninglessness might get blown up. If so, that’s the price of progress.

Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul; and with neurosurgeon Michael Egnor of the forthcoming The Human Soul: What Neuroscience Shows Us about the Brain, the Mind, and the Difference Between the Two (Worthy, 2025). She received her degree in honors English language and literature.

Octopus Intelligence Shakes Up Darwin’s Tree