Peter Godfrey-Smith

'Brilliant' Guardian Waterstones Non-Fiction Book of the Month (March) SHORTLISTED FOR THE 2017 ROYAL SOCIETY SCIENCE BOOK PRIZE What if intelligent life on Earth evolved not once, but twice? The octopus is the closest we will come to meeting an intelligent alien. What can we learn from the encounter?

The Octopus and the Evolution of Intelligent Life

Other Minds

Dhrumil Patel

In all but a few animals, the chemical interactions between some cells become the basis for a nervous system, small or large. And in some of these animals, a mass of such cells concentrated together, sparking in a chemo-electrical storm of repurposed signaling, become a brain.

Neurons cost a grecat deal of energy to run and maintain. Creating their electrical spasms is like the continual charging and discharging of a battery, hundreds of times cach second. In an animal like us, a large proportion of the energy taken in as food, nearly a quarter in our case, is spent just keeping the brain running.

The history of life is a history of intermediates, shadings-off, and gray areas.

The evolution of muscle, derived from tiny fiber-like elements inside cells, created a new means by which life impresses itself on the world. All living things affect their environment by making and transforming chemicals, and also by growing and sometimes by moving, but it is muscle that gives rise to rapid, coherent action on large spatial scales.

To some degree, unity is inevitable in a living agent: an animal is a whole, a physical object keeping itself alive. But in other ways, unity is optional, an achievement, an invention. Bringing experience together—even the deliverances of the two eyes—is something that evolution may or may not do.

How animals change color: The skin has an outer layer, a dermis, that acts as a covering. The next layer down contains the chromatophores, the most important of the color-control devices. A single chromatophore unit contains several different kinds of cells. One cell holds a sac of a colored chemical. Around it are muscle cells, one or two dozen of them, which pull the sac into different shapes. Those muscles are controlled by the brain. They stretch the sac to make its color visible, or relax it for the opposite effect.

David Hume in an attempt to find his self: "I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe any thing but the perception." These sensations or perceptions, he said, comprise him — nothing more. A person is just a bundle or collection of images and feelings, "which succeed each other with an inconceivable rapidity, and are in a perpetual fux and movement."

Why don't cephalopods live for a longer time? Why don't we all live for a longer time? On mountainsides in California and Nevada there are pine trees that were alive when Julius Caesar was wandering around Rome. Why do some organisms live for dozens, hundreds, or thousands of years while others, in the natural course of events, do not see even a single year pass?

The mind evolved in the sea. Water made it all possible. When you dive into the sea, you are diving into the origin of us all.

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