Animal Life and the Birth of the Mind
The evolution of consciousness and the minds of animals: inspired by Metazoa by Peter Godfrey-Smith
I’ve previously written about ways we can get traction on studying consciousness: behavioral studies that present similar stimuli but elicit different experiences, or pathological cases where conscious experience breaks down in counter-intuitive ways. But these approaches focus on human consciousness. A powerful alternative way is to look to the animal world, and especially our evolutionary lineage.
Where and when did minds arise? By tracing our evolutionary history, we can identify the biological features that arose along the way and those pieces fit together into what we now call our minds. This is the approach Peter Godfrey-Smith takes in his book Metazoa.
Godfrey-Smith is an interesting character—he’s an avid scuba diver as well as a philosopher. His writing is full of colorful descriptions of animals: corals as clenching and unclenching hands, decorator crabs wearing coral or sponge as if they’re uniforms for secret societies, and the fighting between soft-bodied octopuses is likened to a pillow fight between pillows.
But my favorite are his passages about arthropods, which are described as like a Swiss army knife due to all of their limbs, amongst other fun analogies (quoted by Joseph Rahi in our Book Club discussion):
This emptied-out-toolbox appearance is fairly typical of arthropods. If we are building a hermit crab, why not put some things that look like spatulas on the top of the face? Why not? That is the arthropod way of evolving: when in doubt, add some legs. Add some spatulas to your head. [...] [T]here are some crustaceans that naturally have one small claw and one huge, outsize one, as if the animal bought it late at night online.
These descriptions of marine creatures play an important role in the case Godfrey-Smith is making. These aren’t just weird animals, they are examples of different ways of being.
It’s common in philosophy to imagine philosophical zombies: beings exactly like us, only completely “blank” on the inside. No experience or feeling of consciousness, but all the exact same behaviors—including, presumably, endlessly debating consciousness.
This imagining is central to many of the arguments about consciousness. One goal of the book is to replace the all-or-nothing imagining of the zombie with a more gradual transition by offering bridging concepts. By looking at evolution, we can look at the individual pieces that came together to form the human mind.
A sea sponge is multicellular, but there is only loose coordination among the cells. They pump water through to filter food, but the range of activity and level of coordination needed is limited.
Contrast this with cnidarians (jellyfish and the like). They have decentralized nerve nets that coordinate activity across the body to allow coordinated movement like the rhythmic contractions of muscles for swimming. If each part acted independently, the jellyfish would just flail in place.
The Cambrian period brought a massive change: the rise of arthropods. These critters (shrimps, crabs, and the precursors of bugs) had a very different way of being. Complex sense organs like eyes and feelers evolved, and limbs gave new ways of interacting with the environment.
The sensory information and the available actions were suddenly much more complex. The need for integration grew. Many movements, like swimming or scuttling along the sea floor, require coordination. But this isn’t just the synchronization of muscles like the jellyfish, goals also need to be integrated. You don’t want the legs to scuttle away while the arms and head have found something good to eat. Processing became a bit more centralized.
On top of this added complexity came a new sort of problem: how to tell apart self from other. Arthropods have feelers. How do they tell apart a feeler making contact because of self-movement, versus making contact because something in the environment has moved—potentially a predator? And, with all of the limbs arthropods have, how do you tell apart something interesting in the environment from your own body? Godfrey-Smith tells a charming story of watching a shrimp grab enthusiastically at one of its own limbs, before seeming to realize it was grabbing itself and backing off. And so, Godfrey-Smith argues, this arthropod way of being came along with a tacit sense of self—an ability to distinguish one’s own body and actions from the environment and integrate action accordingly.
A further step in the direction of humans came with the rise of vertebrates. We evolved from fish. Fish move quickly through the water, but they move as a unit. Fish interact with their environment with their jaw, which acts almost like an opposable thumb. Doing so requires a commitment of the whole body. Godfrey-Smith suggests this fishy ancestry is why vertebrates are so integrated.
As animals evolved, the environment became more complex—it became filled with other animals capable of complex sensing and behavior. This required much more sophisticated predictions and pattern finding in the world. Being able to change behavior flexibly became a requirement to survive clever predators and make use of symbiotic relationships.
The evolution of minds is a story of increasingly sophisticated sensing and behavior. These led to increased complexity of the range of states an animal can find itself in and the range of responses it can make. But this expansion comes with an important constraint: integration. The animal needs to act as a unit, it can’t be a bundle of disconnected reflexes. Centralized judgments about what is a good state or not need to be made, so action can be coordinated across the whole body towards a goal.
This gradual development of complex sensing and agency, coupled with the need to integrate and act in a unified way, are suggested as pieces along the way to add up to our human experience. Consciousness isn’t just a sudden leap that began with us humans, but something that was built gradually from the pressures of coordinating an increasingly sophisticated suite of senses and actions.
Splitting apart the mind
Reading Metazoa came at a good time—I recently read A Philosophy for the Science of Animal Consciousness by Walter Veit (in preparation for my conversation with him, which you can see here).
Godfrey-Smith was one of Veit’s doctoral advisors, so it was a neat coincidence. More importantly, Veit’s book does a deeper dive on one of the topics of Metazoa: what are the different components of consciousness, and how did they come about?
Veit adopts a framework from comparative cognition researchers Birch et al., who frame consciousness as having five key dimensions: perceptual richness, evaluative richness, integration at a time, integration across time, and self-consciousness.
For Veit, evaluation is the core component. “Evaluative richness” refers to the valence of different states—fear, thirst, and pain feel bad. Comfort, love, and pleasure feel good. The valence of how we are feeling is a sort of “common currency”—overall, how much we value the state we are in.
This ability to integrate different aspects of a state into a valence judgment allows for integrated decisions—e.g. should I stay or should I go. This basic evaluation may have laid the foundation for the other dimensions. The ability to evaluate states is what organizes behavior and makes rich perceptual representations meaningful. There’s no point perceiving something approaching if you can’t also judge whether that’s good given your circumstances.
This move reframes consciousness as fundamentally affective—about emotional state—rather than about the sensory experiences that often take center stage in philosophers’ thought experiments.
The other dimensions—degrees of integration, self-consciousness, different perceptual abilities—give the unique “flavor” of the experience of different animals. It makes sense that consciousness has different components that built up over time—and that different animals may have different components in different degrees.
Consider octopuses. An octopus has a central brain, but the majority of its neurons are actually in its arms. This more distributed nervous system has advantages: each arm can react quickly on its own without routing every signal to the central brain and back. Just like our spinal reflexes that just send signals to our spinal cord that provoke quick responses, having the “decision” made closer to the extremity speeds it up.
The downside of this speed is the loss of integration. One tentacle doesn’t necessarily know what the other is doing. Octopuses are still capable of organized behavior, but they are a mix of central control and tentacles acting independently. It’s a more distributed way of being than our experience. An octopus isn’t as integrated a being as us.
This isn’t to say human consciousness is the pinnacle of consciousness, maxing out all of the dimensions. In some domains, other creatures surpass us. This is most obvious in the sensory dimension: hawks have more visual acuity than we have, bats can make many more auditory discriminations than we can, and various sea creatures can sense electrical fields in ways completely alien to us. The sensory richness of different animals is in many cases richer than what we have.
Our experiential world is shaped by what the evolutionary pressures required. Different ways of being require different experiences. Godfrey-Smith argues, for example, that insects may not feel acute pain. When an insect loses a limb, it doesn’t tend to the wound. It just gets on with it, using whatever it has left. This, the argument goes, is because there isn’t much else you can do with the hard chitin body of an arthropod—they don’t really heal.
Compare this to gastropods (slugs and the like). They have squishy outsides that can heal quite quickly. They do exhibit protective behaviors after being hurt—presumably because this has benefits, as the body can actually heal. Staying put, laying low, and protecting the wound will confer an advantage. Feeling acute pain has a role here.
While they may not experience acute pain, Godfrey-Smith suggests arthropods might have more diffuse affective states. Bees that have been shaken (simulating a predator attack) exhibit more pessimism, making them less likely to approach ambiguous stimuli, as if expecting bad outcomes. This makes ecological sense—if the environment is dangerous, you should bee more cautious. While they may not feel acute pain, in Godfrey-Smith’s view, they still feel in this more diffuse sense. Perhaps bees can feel sad.
This connects up with another distinction Godfrey-Smith draws: the difference between experience and consciousness. While these terms are often used interchangeably, he points out that we humans usually think of consciousness as just those things we are consciously attending to; the object of our focus. Experience, on the other hand, is evocative of something more diffuse and general, not necessarily what we’re paying attention to but all of the factors flavoring what we’re currently experiencing.
Attention itself is a mechanism—a form of centralization. Different animals might have this, but perhaps it makes sense to talk about experience without attention, this more diffuse sense. Godfrey-Smith encourages us to think more about internal, affective states, rather than the typical sensory examples, when thinking about experience. This, perhaps, helps us appreciate all of the mechanisms that gradually accumulated to produce our way of being.
Ethics and Animal Consciousness
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