Other Minds The Octopus and the Evolution of Intelligent Life

Peter Godfrey-Smith is popularly known as the scuba-diving philosopher and has just published his new book Metazoa, in which he plumbs the evolutionary origins of minds. In preparation for reviewing that book, I am (finally) turning my attention to his initial 2016 bestseller Other Minds. Here he beholds the octopus, only to find that, behind those eight tentacles, an intelligence quite unlike ours beholds him in turn.

It is hard not to be familiar with at least anecdotal evidence that octopuses are unusually smart and inventive creatures. Stories from aquarium owners and results from behavioural experiments make for popular fodder in (science) news outlets. Sy Montgomery’s incredibly touching The Soul of an Octopus, which I read some years ago, only added to this impression. And lacking a true case of “first contact”, Russel Powell mentioned in Contingency and Convergence that coleoid cephalopod mollusks “are rightfully considered intelligent aliens on Earth” (his p. 140). But if like me, you have not read up on the more technical literature on their behaviour and cognition, it is hard to really fathom the octopus.

To make the reader appreciate just how different their intelligence is, Godfrey-Smith therefore first takes the reader down the evolutionary tree of life, back to our last common ancestor some 600 million years ago. Before the explosions of body plans in the Cambrian, the Ediacaran fauna consisted mostly of mats of bacteria and algae grazed by crawling invertebrates – a seemingly tranquil tableau dubbed the Garden of Ediacara by one author. The likely sequence of events that led, quite literally, to the rise of the cephalopods involved the development of buoyant shells, the invention of jet propulsion, and, in some groups, the almost complete loss of the protective shell.

Godfrey-Smith only touches on those stages of cephalopod evolution that are relevant to his story here, which allowed Danna Staaf in 2017 to complete that picture with her magnificent book Monarchs of the Sea. What he is interested in is what the development of such utterly flexible bodies meant for brain development. First off, octopus brains are quite unlikely any others: their oesophagus runs through a ring-shaped central brain (with attendant risks when swallowing spiky prey), while their arms all contain large numbers of neurons. It seems that, at least part of the time, the arms “enjoy considerable independence” and “seem “curiously divorced” from the brain” (p. 67), suggesting a mix of top-down control by the central brain and a certain neural autonomy in each arm.

What lifts Other Minds above mere slack-jawed voyeurism at nature’s weirdness typical of fluffy pop-science books is that Godfrey-Smith, as a philosopher, is both interested and capable of exploring this far deeper. Yet, he does this with a style that, for want of a better description, feels kind and caring. So, when on page 24 he talks of the sensory-motor view of nervous systems, he bothers with a polite footnote: “If you’ve seen the word “sensorimotor” instead, please treat this as the same“. Thus, when he introduces the psychological concept of embodied cognition, you can rest assured that, as a reader, you will not be left feeling out of your depth. This refers to the notion that some of our smartness is encoded in our body rather than our brain. The constraints imposed by the joints and angles of our limbs make walking a rather natural solution to the problem of moving around. But how does this work for an octopus, whose body has no fixed shape? Their embodiment is different, to say the least, but Godfrey-Smith takes it a step further, arguing that “The octopus lives outside the usual body/brain divide” (p. 76).

These and other observations lead to the question of what it feels like to be an octopus. This is where Other Minds dives deeper, pondering the evolution and nature of consciousness and experience, and how octopuses experience the world given their hybrid centralised-decentralised nervous system. He takes a particularly close look at the fantastic colour-changing capabilities of cuttlefish, the most expressive of the cephalopods. This is all the more surprising given that they are effectively colour-blind, as they possess only one kind of photoreceptor (versus three in humans). Part of the answer to this puzzle was revealed by recent research on a different octopus species that showed that light-sensitive molecules in its skin allow it to both sense light (yes, with its skin) and respond with colour changes.

The theoretical and philosophical ponderings here are pleasantly lightened up with anecdotes from Godfrey-Smith’s observations on wild octopuses while scuba-diving at an underwater site in Australia dubbed Octopolis. Due to its high density of octopuses, this is a particularly interesting and rare study site in itself, as he reveals here.

All of the observations and studies mentioned here make for an even more bizarre picture once you realise that most octopus species live only a few years, with females breeding once and then dying. Why such neuronal profligacy? A quick tour into the evolution of senescence leads Godfrey-Smith to a neat explanation that takes on board the peculiarities of their evolutionary history. Here is an organism in which the loss of its shell led to the unusual combination of a complex nervous system to control a body of unbounded possibility, with a life-fast–die-young approach to reproduction due to an increased vulnerability to predation.

So I ask you again, what is it like to be an octopus? Once you reconsider this question towards the end of the book, you will realise that what Godfrey-Smith has been doing here, chapter by chapter, is gently blowing your mind. The subject matter is fascinating in itself, but it is his light touch and deft handling of complex and sometimes abstract concepts that make it easy to see why Other Minds was such a runaway success. Can he pull this off again and continue to captivate his audience? I will turn to his new book Metazoa next to find out just that.