From “Intelligence is today’s unknown country” (Salvo 23)
Some invertebrates, especially mollusks, are also unexpectedly intelligent. Underwater footage shows that, in the first known example of tool use among octopi, one species of octopus has learned to dig up and use discarded halved coconut shells as a shelter. Neatly halved coconuts are a human discard, so the behavior may actually have been learned in recent millennia. Researchers think that the octopi were using some less satisfactory material before, but they had the intelligence to just switch. According to researcher Mark Norman,
They probe their arms down to loosen the mud, then they rotate them out.
After turning the shells so the open side faces upwards, the octopuses blow jets of mud out of the bowl before extending their arms around the shell—or if they have two halves, stacking them first, one inside the other—before stiffening their legs and tip-toeing away.
But intelligence is very unevenly distributed among invertebrates. Clams and oysters are also mollusks, and they are as sharp as marbles.
Too much effort is focused on trying to discover a continuum of intelligence leading all the way up to humans. Humans are just different, period. Octopuses are smarter than people think, but they do not build or program computers.
The reasons some animals have and others don’t have intelligence, in the same basic groups of life forms, pursued as a project in its own right, might yield more understanding of what intelligence is.