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

by Peter Godfrey-Smith

On our lineage, the chordate design emerges, with a cord of nerves down the middle of the animal’s back and a brain at one end. This design is seen in fish, reptiles, birds, and mammals. On the other side, the cephalopods’ side, a different body plan evolved, and a different kind of nervous system. These nervous systems are more distributed, less centralized, than ours. Invertebrates’ neurons are often collected into many ganglia, little knots that are spread through the body and connected to each other. The ganglia can be arranged in pairs, linked by connectors that run along the body and across it, like lines of latitude and longitude. This is sometimes called a “ladder-like” nervous system, and it does look like a ladder embedded within the body.