Other Minds

Mammals and birds are usually counted as the smartest animals, but a far-off branch of the tree of life has produced high intelligence too: the cephalopods, meaning squid, cuttlefish and above all the octopus. Captive octopuses have picked out individual keepers, raided nearby tanks for food, switched off lightbulbs with jets of water, plugged drains and escaped.

Peter Godfrey-Smith, a philosopher of science and a skilled scuba diver, considers what it means that evolution built minds at least twice. He treats the octopus as the nearest thing humans will meet to an intelligent alien, and weighs what the meeting can teach.

The book follows the ocean history of subjective experience. Clumps of seaborne cells learn to live together, sense, act and signal. The first nervous systems appear, probably in ancient relatives of jellyfish. Cephalopods begin as small mollusks, then leave their shells and rise off the sea floor to hunt.

Godfrey-Smith draws on current research and his own dives to probe open puzzles. One is how a solitary animal becomes so smart. Another is what it is like to have eight arms so full of neurons that they nearly think for themselves. A third is why some octopuses leave their hermit habits and gather off the coast of Australia.

The aim is to trace inner life to its roots and set humans beside their strangest animal relatives, so that the octopus mind sheds light on our own.