Other Minds

^z 12th October 2023 at 3:01pm

Peter Godfrey-Smith's 2016 book Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness is a fun, fast romp through evolutionary biology, philosophy of mind, neurophysiology, and the author's personal relationships with cephalopods as a scuba diver. It raises an ocean of questions and suggests some potential answers. As Godfrey-Smith says in the first chapter, "Doing philosophy is largely a matter of trying to put things together, trying to get the pieces of very large puzzles to make some sense." Some big takeaways from Other Minds include:

  • maybe we can better understand neural activity by looking at how it arose in distinct branches of the tree of life that forked hundreds of millions of years ago – among vertebrates (mammals, birds, fish, ...) and more distantly among mollusks (especially octopuses, cuttlefish, and squid)
  • nervous systems have two main functional purposes:
    • sensory-motor — to link data perceived from the environment with muscular responses
    • action-shaping — to coordinate and enable complex or large-scale motions based on local micro-acts of body parts
  • "inner speech" and spatial imagery seem to be important parts of human cognition, but "very complex things go on inside other animals without the aid of speech"
  • consciousness and more general subjective experiences may arise along a continuum, not abruptly — "There's a smooth transition from minimal kinds of sensitivity to the world to more elaborate kinds, and no reason to think in terms of sharp divides" — beginning perhaps with "primordial emotions" such as pain, thirst, suffocation, hunger, sexual arousal, etc.
  • lifespans of creatures are driven by evolution and the cost-benefit tradeoffs of mutations on different timescales

Godfrey-Smith summarizes near the end of Chapter 7:

The lifespans of different animals are set by their risks of death from external causes, by how quickly they can reach reproductive age, and other features of their lifestyle and environment. That is why we can live for about a century, a nondescript fish can live for twice as long, a pine tree's life can run from John the Baptist's to your own, and a giant cuttlefish—with its wild colors and friendly curiosity—arrives and is gone in a couple of summers.

In the light of all this, I think it is becoming clearer how cephalopods came to have their peculiar combination of features. Early cephalopods had protective external shells which they dragged along as they prowled the oceans. Then the shells were abandoned. This had several interlocking effects. First, it gave cephalopod bodies their outlandish, unbounded possibilities. The extreme case is the octopus, with almost no hard parts at all, and neurons spread through the body instead of bones. Back in chapter 3 I suggested that this open-endedness, this sea of behavioral possibility, was crucial to the evolution of their complex nervous systems. It's not that the loss of a shell alone created the evolutionary pressure leading to those nervous systems. Rather, a feedback system was established. The possibilities inherent in this body create an opportunity for the evolution of finer behavioral control. And once you have a larger nervous system, this makes it worthwhile to further expand the body's possibilities—collecting all those sensors on the arms, creating the machinery of color change and a skin that can see.

The loss of the shell also had another effect: it made the animals much more vulnerable to predators, especially fast-moving fish, with bones and teeth and good vision. That put a premium on the evolution of wiles and camouflage.

But there is only so much those tricks will achieve, only so many times they will save the animal. An octopus can't expect to live a long time, especially as they must be active as predators themselves. They can't just hide in a hole and wait for food to come to them. They have to be out and about, and once in the open they are vulnerable. This vulnerability makes them ideal candidates for the Medawar and Williams effects to compress their natural lifespan; a cephalopod's lifespan has been tuned by the continual risk of not making it to the next day. As a result, they have ended up with their unusual combination: a very large nervous system and a very short life. They have the large nervous system because of what those unbounded bodies make possible and the need to hunt while being hunted; their lives are short because their vulnerability tunes their lifespan. The initially paradoxical combination makes sense.

And besides conceptual insights, Other Minds also has lots of stories and photographs of cute octopuses!

(cf Bits of Consciousness (2000-01-21), Suffer the Animals (2000-06-11), Drawing the Line (2004-07-11), ...) - ^z - 2023-10-12