What an octopus can teach us about being human

Eight years ago, I went to Corsica with my now wife. I had brought my old snorkel and mask, and while she sat and read novels on a sunlounger I would pootle around the cool Mediterranean waters. Our hotel was on a headland; to the west was a rocky shore, the bottom plunging away, with teeming shoals of multicoloured fish. To the east was a great sandy bay. The beach was filled with sunbathing French families, but to a first glance, the bay itself was a desert.

That wasn’t true, of course; there was lots of life; at one point a ray scooted past me. But it felt featureless. I had been swimming around it for half an hour when I spotted a large rock underwater, a short swim away. It was the only thing breaking the monotony of the sea floor, so I swam closer, and saw a small hollow underneath. Around the hollow were dozens of empty clam shells. I swam down, and from under the rock, a pair of eyes – alien yet oddly human – stared back at me, nervously.

It was a common octopus. I’d love to say that I felt a connection, two intelligences communicating across half a billion years of evolution, but I’d probably be lying. Still, I was fascinated by it; I stayed there for some minutes, repeatedly duck-diving back down to stare once more into its lair.

In his book Other Minds: the Octopus and the Evolution of Intelligent Life, the philosopher Peter Godfrey-Smith describes many similar (but more impressive) experiences; indeed one of my lasting impressions of the book is the feeling of sharp and bitter envy that Godfrey-Smith has somehow made a career out of arguing about philosophy and snorkelling with octopuses around the coast of New South Wales. The book argues that cephalopods – octopuses, and their close relatives squid and cuttlefish – are the closest thing to alien intelligence that we will meet on Earth.

There are plenty of other quite bright animals around. Chimps, dolphins, dogs; some birds are surprisingly intelligent. But all of them are fairly closely related to us. The common ancestor of all of them lived, says Godfrey-Smith, about 320 million years ago. It would have looked a lot like a smallish lizard. It would have had four limbs and a head, and lived on land. Its brain would have had many of the same features that ours have. It had already taken many steps down the path towards an intelligence like ours. Almost all of its descendants, mammals, birds and reptiles, are relatively clever.

But the common ancestor we share with cephalopods, Godfrey-Smith points out, was much earlier – at least 600 million years ago – and much simpler. It was most likely a flattened worm-like thing a few millimetres long. It may have had a basic nervous system, it may have had light-sensitive patches as precursors to eyes. But it certainly was not “intelligent”. One branch of its descendants included the lizard-like thing that led to us; another includes all the molluscs, snails, clams, slugs and so on. In only one tiny sub-branch, the cephalopods, did impressive intelligence evolve, entirely separately from our own.

The book looks in fascinating detail at the research establishing the extent and nature of cephalopod intelligence. An octopus’s intelligence, he says, is more distributed than ours – each arm has a separate sub-brain, with some autonomy. They can communicate, in extraordinary changes of colour; they are curious and inquisitive, and have distinct personalities, including what seems very like a mischievous streak.

Godfrey-Smith uses their alien minds as a framework and means of illumination for what it means to be intelligent, and to have a “self”, unitary and bounded – if an octopus has eight sub-brains part-controlling its arms, does it have eight sub-personalities? How much is our own experience of a unitary self an illusion, if large parts of our own actions are (as they are) similarly outsourced to subroutines and automated processes?

By deploying octopuses, so different from humans, as a way into human consciousness he makes the book into something quite profound: about what it means to have an inner life, what it “feels like” to be something. He discusses psychological and philosophical theories of consciousness, from William James and David Hume to Daniel Dennett and Thomas Nagel, and by looking at the ways that octopuses behave and react to stimuli – including pain – is able to say something new and interesting about what it means to be human.

But it is not just a philosophical exercise. He very obviously cares deeply for the cephalopods, and has spent a lot of time in their world; he get to know, almost “befriends”, several, and is wounded by their deaths. Unusually, among intelligent creatures, octopuses are short-lived, only reaching a year or two: my Corsican friend is long dead, a fact I realised reading this book, and which I found surprisingly saddening. But I also know that my fascination, as I stared into its familiarly alien eyes, was entirely justified.

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Tom Chivers is a science writer. His second book, How to Read Numbers, is out now.

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