Among all the phenomena that humans can experience, an encounter with a cephalopod is the closest thing to making contact with an extra-terrestrial civilization.
Planet Earth is inhabited by many intelligent creatures. The vast majority of them are vertebrates; the last common ancestor of such creatures as humans, dolphins, cats, crows, large parrots and monitor lizards lived some 300 million years ago. It lived on land and already had a fairly well-developed nervous system.