Life undersea has a mesmerizing strangeness, from glass sponges—lacy matrices draped with cellular nets—to rococo sea dragons and soft corals like trees in a slow wind. It’s the stuff of a thousand documentaries, but for Peter Godfrey-Smith the spectacle is a curtain-raiser to a profound scientific drama, in which the lives of quite un-human creatures illuminate deep mysteries about the nature of sentience, and what it means to possess a mind.
In “Metazoa,” the scuba-diving historian and philosopher of science tackles these questions with eloquent boldness, reminding us that “life and mind began in water.” Mr. Godfrey-Smith continues the journey he began in “Other Minds” (2016), which focused on the octopus, the closest we have to an “intelligent alien”: an invertebrate with a big, complex nervous system and capacities for play and adaptation. Now he expands the exploration to multicellular animals as a group—the Metazoa of the title—homing in on those marking key transitions in the evolution of mind.
