First cephalopods (ammonites, nautiluses, squid, octopuses, cuttlefish); the term ammonite derives from the Egyptian god Amun, whose horns resemble the ammonite’s spiral. These were the first cephalopods, from which octopuses would soon evolve. Studies highlighted and conducted by Peter Godfrey Smith point to a complex intelligence on the part of modern octopuses, and probably even self-awareness. This therefore poses a dilemma: either self-awareness evolved independently at least two or three times (us, octopuses, crabs, etc.), or it evolved only once, but long ago, before the emergence of cephalopods. The last common ancestor between cephalopods and Homo sapiens dates back 600 million years. The octopus’s nervous system is very different from ours, essentially having a central brain (with two hemispheres and no corpus callosum connecting them above) and eight large groups of neurons distributed throughout each tentacle. It’s unknown how these eight “brains” interact, but one hypothesis is that different modalities are used in different circumstances (independence of the tentacles or central control of the brain in the octopus’s “head”). Octopuses also possess some characteristics found in other species (including Homo sapiens), such as REM sleep.
