We Are Not Alone

In 2009, 50 feet underwater in a bay off Australia's east coast, diver Matt Lawrence discovered a site where at least a dozen octopuses came to feed and nest on a bed of shells. The creatures grew accustomed to Lawrence, who returned regularly, sometimes with philosopher and fellow diving enthusiast Peter Godfrey-Smith. On one visit, an octopus took Lawrence's hand in one of its arms and led him on a walk across the sea floor for about 10 minutes, until they'd reached the cephalopod's den.

Such encounters at the spot divers came to call "Octopolis" helped inspire Godfrey-Smith's new book Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. The author, who teaches at the University of Sydney and the City University of New York, has produced a concise and elegant guide to evolution, consciousness, and marine biology: "The mind evolved in the sea," he writes. "Water made it possible."

The idiosyncratic sentience of the octopus, from whom we split on the evolutionary tree 600 million years ago, indicates that higher intelligence on Earth evolved not once, but twice, Godfrey-Smith argues, and in distinctly different directions. "An independent experiment in the evolution of large brains and complex behavior," the octopus is "the closest we will come to meeting an intelligent alien."

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

An octopus has about 500 million neurons, far short of our 100 billion, but well within the range of many mammals. A great many of the neurons are in the arms, which virtually have minds of their own, and so the animal lives with semi-autonomous limbs that, to its central brain, are both "self" and "non-self." Is the octopus aware of that? Does it have consciousness? That can't be definitively answered, but there are clues: Octopuses in captivity find ways to unscrew the tops of their containers and sneak away to find food. They've also figured out that if they spray a jet of water at an offending light bulb, it will short-circuit and turn off. More to the point, they are exceedingly skilled at detecting when they are and are not being observed, even for a moment.

Why does the octopus, with its intelligence and perhaps even consciousness, have an average life span of only about two years? Godfrey-Smith's short answer is that, because it must emerge from camouflage to hunt, it is vulnerable to predators. His long answer involves a deft exploration of the role of genetic mutation in evolution and aging. He suggests, however, that if a community like Octopolis could be maintained for thousands of generations, a longer life span for the octopus could evolve. That would enable further study, a prospect he'd relish because "if we want to understand other minds, the minds of cephalopods are the most other of all."

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