[graycat]

> Octopus, as mollusks, are very far away on the evolutionary tree.

Yes, but for some fast, short, rough guesses, regard intelligence as thinking that yields advantages in surviving in the real world. Then guess that in general intelligence is a source of effective response to the real world. Then, whatever the size of the evolutionary and/or genetic tree, notice that we are all in the same real world. So, all of our examples of intelligence are effective responses to the same real world and, thus, the many examples might have a lot in common.