Cousteau’s accounts are anecdotes, not scientific experiments. Yet, taken together, they capture three aspects of octopuses—some species of them, at least—that strike anyone who spends time in the water with them.

First, different individuals have different temperaments. Some are shy, some are bold; some are inquisitive, some aggressive. Because of this individuality, people who hang out with them, whether in the sea, at a public aquarium, or in the laboratory, tend to give them names—an honor normally reserved for mammals such as dolphins and chimpanzees. Cousteau spoke of an octopus called Octopissimus; one scientific paper I read referred to Albert, Bertram, and Charles.

Second, some octopuses will engage with you. They might reach out an arm and touch your hand. They will investigate an object you present to them, giving every impression of thinking about it as they do so. All the while, they will appear to watch you with their large, mobile eyes. Again, these are behaviors we associate with dolphins and dogs—but not with, say, fish, let alone animals such as sea urchins or clams.

Third, octopuses often behave in surprising ways. Although Albert and Bertram were prepared to pull levers to receive pieces of fish, Charles destroyed the experimental equipment—he pulled it apart with his arms—and repeatedly squirted the experimenter with water. On a recent diving trip, my partner and I came across a little octopus sitting in the sand, two of its arms holding a large half clamshell over its head like a roof. For a while, we looked at it, and it looked at us. Then it shifted. It must have been reaching down with its other arms, because suddenly, like a small animated bulldozer, it tossed up a heap of sand. It did this several times, watching us closely and giving us the sense that, though it was interested in checking us out, it was also ready, if necessary, to pull the shell down like a lid and disappear into the seafloor.

The animals also frequently change their skin color and texture—which, to creatures such as ourselves, fine-tuned to watch faces for frowns and smiles, blushes and blanches, gives the appearance of emotional expressiveness. In other words, an encounter with an octopus can sometimes leave you with the strong feeling that you’ve encountered another mind.

FSG

But that mind—if mind it is—has evolved along a route entirely different from the one that led to our own. The most-recent common ancestors of humans and octopuses lived about 600 million years ago, early in the evolution of animal life. Although much about our joint ancestors is obscure, they were probably small wormlike creatures that lived in the sea. This makes octopuses very different from other animals we suspect of sentience, such as dolphins and dogs, parrots and crows, which are much more closely related to us. In the words of Peter Godfrey-Smith, “If we can make contact with cephalopods as sentient beings, it is not because of a shared history, not because of kinship, but because evolution built minds twice over. This is probably the closest we will come to meeting an intelligent alien.”