Fascinating. I am particularly intrigued by the separate evolution of their intelligence and neurons in their arms. A different type of consciousness indeed, I wonder if it is even possible to comprehend what their experience of the world might be like.
The independent nervous system in an octopus' arm (which continues to operate after an arm has been severed) reminded me of the independent nervous system in the human gut:
"The enteric nervous system has been described as a 'second brain' for several reasons. The enteric nervous system can operate autonomously. It normally communicates with the central nervous system (CNS) through the parasympathetic (e.g., via the vagus nerve) and sympathetic (e.g., via the prevertebral ganglia) nervous systems. However, vertebrate studies show that when the vagus nerve is severed, the enteric nervous system continues to function."[1]
It's remarkable how two nervous systems that evolved separately share this kind of similarity.
The idea that octopi evolved their intelligence due to increased mobility after losing their ancestral shell is consistent with findings about the human brain, which are that brains are used for movement.
I highly recommend Daniel Wolpert's talk about this idea:
