I was listening to Quirks & Quarks on CBC radio in my car a few months ago and they were discussing the incredible intelligence of octopuses. As my old chemistry teacher would say, they can adapt: take whatever situation they’re in and turn it around to their advantage. For example:
In 2016, an octopus named Inky made a daring escape from the national aquarium in New Zealand. The eight-armed Houdini squeezed through a tiny gap a maintenance worker left at the top of its tank.
Inky slithered across the floor and made his escape down a drain pipe that exits into the ocean.Source: a CBC web page
The guest, Piero Amodio, was explaining that their high intelligence was surprising because as commenter Melo has noted, intelligence is often selected in social animals and octopuses are very solitary. Also, as r/K theory would predict, bigger brains are more common in long-lived species and octopuses have short lives.
But because intelligence is arguably the ultimate evolutionary adaptation, it seems to have evolved even under very different selection pressures from other intelligent animals like primates and crows.
One possibility suggested by Amodio is that octopuses needed to be smart because they didn’t have a shell to protect them from predators. If commenter RR were conducting the interview, he would immediately complain that that’s a just-so story as he does for all attempts to explain how intelligence evolved.
However Amodio plans to test the hypothesis by seeing if there’s a correlation between cephalopod brain size and the number and variety of predators in their environment. If a positive correlation is found, the hypothesis made a meaningful prediction and is not a mere just-so story. That wouldn’t satisfy RR, but it would satisfy the scientific community.
A lot of us tend to think of intelligence as a property of the brain but commenter Melo has argued it’s a function of the entire nervous system. I suspect Amodio would agree with Melo because an octopus can move its arms without getting signals from its brain, or one could even argue most of its brain is in its arms. Amodio states:
Two thirds of their neuron cells, they are not located in the brains, but they are located in their arms. In octopus, there is a big level of independence of movement for the arms. It’s something completely different from our way of thinking about brains and of course about apes and crows…
You can listen to the brief interview here.