Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. By Peter Godfrey-Smith. Farrar, Straus and Giroux; 255 pages; $27. To be published in Britain by William Collins in March 2017; £20.

LIKE life itself, the mind first emerged in Earth’s oceans. What is less well appreciated is that it evolved there in at least two distinct ways. One sentient branch of the tree of life is descended from the animals that crawled onto dry land hundreds of millions of years ago. It comprises humans and other mammals, and birds. The other branch remained water-bound and eventually produced another collection of creatures possessing higher intelligence: the cephalopods, a class of animals that includes squid, cuttlefish and octopus, probably the smartest of them all. In “Other Minds”, Peter Godfrey-Smith, a philosopher, skilfully combines science, philosophy and his experiences of swimming among these tentacled beasts to illuminate the origin and nature of consciousness.

An octopus’s body contains 500m neurons, roughly the same as a dog’s, but most of these reside in the cephalopod’s arms and allow the tentacles to act independently from the brain (their arms literally have a life of their own). The type of consciousness experienced by an octopus, then, is wholly alien to humans.

Early experiments assumed that the intelligence of animals could be estimated by their ability to carry out tasks, such as learning to pull a lever in exchange for food. Octopuses perform quite well in such tests but not as well as rats. Yet it is the anecdotes buried in research papers or related to him by scientists who work with animals that Mr Godfrey-Smith contends are often more revealing than the experiments themselves. One researcher told him of an octopus that expressed its displeasure with the lab food by waiting until she was looking before stuffing the unwanted scrap of squid down the drain.

According to the author, such behaviour shows octopuses are more intelligent than the scientific literature suggests. Despite these displays of chutzpah, however, they have failed to become as smart as mammals or birds because, as a short-lived and solitary species, they have not had to contend with the many challenges of social living that seem to drive the evolution of complex brains.

“Other Minds” presents an intriguing possibility in the form of Octopolis, off the east coast of Australia. A patch of sand a few metres in diameter covered in thousands of empty scallop shells, Octopolis appears to host up to a dozen or so octopuses at any one time and presents them with an opportunity to meet. “Some will pass by others without incident, but an octopus might also send out an arm to poke or probe at another,” Mr Godfrey-Smith writes. “An arm, or two, might come back in response, and this leads sometimes to a settling-down, with each octopus going on its way, but in other cases it prompts a wrestling match.” Could interactions like these lead, over many thousands of years, to the octopus becoming a brainier species? It might if there were thousands of such sites in the world’s oceans. Sadly, Octopolis is the only known example. If only, if only.