A common octopus brain has 500m neurons, a “smartness” that ranks alongside dogs and even a three-year-old child. They also developed large brains to compensate for their new vulnerability. Then they discarded their shells the first octopus probably appeared 290m years ago. Its ancestors evolved defensive shells and became the first predators: the frills of these snail-like creatures, which crawled on the ocean floor, became tentacles and they began to swim. In the same way, the octopus’s fluidity seems like a collation of the sea itself.

We can get by on land only by carrying a huge amount of salt water around with us.” “The chemistry of life is an aquatic chemistry. He takes us through those early stirrings in the seas of deep time, from bacteria that sense light and can taste, to cnidarian jellyfish, the first organisms to exhibit nervous systems, which he describes wonderfully: “Picture a filmy lightbulb in which the rhythms of nervous activity first began.” The ocean itself became the conduit for evolution we feel a magnetic attraction to the vast waters that gave us birth because we still carry the sea inside us. The beauty of Godfrey-Smith’s book lies in the clarity of his writing his empathy, if you will. ‘The body itself is protean, all possibility’ … an octopus hunting in a lagoon on the island of Mayotte near Madagascar. His book stands alongside such recent works as Hal Whitehead and Luke Rendell’s The Cultural Lives of Whales and Dolphins as evidence of new and unconstrained thinking about the species with which we share our watery planet.

This is why they present themselves as a fascinating case study to Godfrey-Smith, who is a philosopher of science – because of what can be learned from them about the minds of animals, including our own.

Cephalopods – octopuses, squids and nautiluses – “are an island of mental complexity in the sea of invertebrate animals”, he writes, having developed on a different path from us, “an independent experiment in the evolution of large brains and complex behaviour”. Peter Godfrey-Smith’s brilliant book entirely overturns those preconceptions. Perhaps that’s why we look on the octopus as an eldritch other, with its more-than-the usual complement of limbs, bulbous eyes, seeking suckers and keratinous beaks voraciously devouring anything in its slippery path. ‘Yea, slimy things did crawl with legs / Upon the slimy sea.” Coleridge’s lines evoke those Precambrian depths where sensate life first stirred, and which remain lodged atavistically in our collective imaginations.

Other minds the octopus the sea