Peter Godfrey-Smith’s new book, “Other Minds,” delves into the deep mysteries of the octopus, both its evolution and its many marvelous abilities. Godfrey-Smith appears Thursday, Dec. 8, at Town Hall Seattle.

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‘Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness’

by Peter Godfrey-Smith

Farrar, Straus and Giroux, 254 pp., $27

Two animals more unalike than humans and octopuses are hard to imagine. Where we have a brain, spine and central nervous system, octopuses are “probably the closest we will come to meeting an intelligent alien,” writes Peter Godfrey-Smith, an award-winning author of four books.

Octopuses have neither skeletons nor shells, can squeeze through a hole the size of their eyes, have three hearts with copper-rich blue-green blood, and are apparently color blind but somehow change colors to communicate or camouflage themselves. Their brains are a rudimentary clump through which their esophagus passes, meaning if they choke on something, it can cause brain damage.

But octopuses have a half billion neurons — cells that process and transmit information — in a net covering their entire body. Their eight arms, only partially dependent on the central brain, can taste, smell, sense light and move of their own volition. Like lizards able to detach their tails to escape predators, octopuses can jettison arms, which grow back. Generally, they’re territorial, more active at night and solitary except to mate.

Author appearance

Peter Godfrey-Smith

The author of “Other Minds” will appear at 7:30 p.m. Thursday, Dec. 8, at Town Hall Seattle, 1119 Eighth Ave. Tickets are $5 at and at the door. Information: 206- 652-4255.

Godfrey-Smith, a scuba diver and also professor of philosophy at both the City University of New York and University of Sydney, began diving with a friend off Australia’s east coast at a site discovered in 2009. They named it Octopolis. Fifty feet below the surface, it was a rare place, for in a thick layer of scallop shells discarded after the meat had been eaten, the animals lived in a city of dens and interacted far more than usual.

Exploring Octopolis led Godfrey-Smith to explore the evolution of its otherworldly inhabitants. His book begins roughly 600 million years ago during the last time humans and octopuses shared a common ancestor, a flat wormlike thing a few millimeters long with light-sensitive patches, possibly nets of nerves or perhaps a tiny neural cluster of a brain. How, he wondered, did consciousness arise from these raw materials?

Even earlier than these worms were creatures whose fossils were found in the outback’s Ediacaran Hills in 1946. They provide “our first direct evidence” about life from about 635 million to 542 million years ago. Then suddenly, at least in geologic terms, the majority of animal phyla developed in the Cambrian period, and some seem to have been vertebrates.

Octopuses weren’t among them. They are cephalopods, a kind of mollusk. In the Cambrian, mollusks had shells. Gradually, octopuses’ single foot became tentacles, they lost their shells and their large nervous systems enabled uncommon intelligence, memory and the ability to learn, although researchers now call them “slow learners.” Despite that description, they recognize people; at those they dislike when in captivity, they squirt jets of water. Good navigators, they easily find their way home from foraging trips.

Godfrey-Smith discusses the mysteries of changing color, cognitive evolution and communication. He wonders how language evolved. Why is there such sophisticated talk among creatures not noted for sociable natures? He compares complex baboon behavior, which he says relies on only a few sounds, with octopuses, whose skin color patterns seem peculiarly elaborate for animals with a mere two-year life span.

At times, the science of this book is daunting, but its study subject is so amazing, it’s hard not to be drawn along, just as Godfrey-Smith was when he extended a hand to an octopus and it reached out to return his touch, echoing his interest.