Other Minds: The Octopus and the Evolution of Intelligent Life

by Peter Godfrey-Smith

Even if Ediacaran life was not as peaceful as has sometimes been supposed, a very different world was around the corner. The “Cambrian explosion” began around 542 million years ago. In a relatively sudden series of events, most of the basic animal forms seen today arose. These “basic animal forms” did not include mammals, but did include vertebrates, in the form of fish. They also included arthropods – animals with an external skeleton and limbs with joints, such as trilobites – along with worms, and various others. Why did it happen then, and why did it happen so fast? The timing may have had to do with changes to the Earth’s chemistry and climate. But the process itself may have been largely driven by a kind of evolutionary feedback, due to interactions between organisms themselves. In the Cambrian, animals became part of each other’s lives in a new way, especially through predation. This means that when one kind of organism evolves a little, it changes the environment faced by other organisms, which evolve in response.