March 2025

My reflections on the books I read this month

(Scroll down for a list of the books I’m currently reading.)

Metazoa: Animal life and the birth of the mind

• by Peter Godfrey-Smith.

As the book’s subtitle suggests, Godfrey-Smith presents here his understanding of how consciousness emerged in evolutionary development. He’s arguing here for a position he calls (and others call) biological materialism, a view that differs starkly from the dualism of philosophers like Descartes. The “project is to show that somehow a universe of processes that are not themselves mental, or conscious, can organize themselves in a way that gives rise to felt experience. Somehow, a part of the world’s often-mindless activity folded itself into minds” (p. 19). In short, he says, minds emerged in biological evolution, not as something different from or somehow produced by material processes, but rather as those processes themselves: “Brain processes are not causes of thoughts and experiences; they are thoughts and experiences” (p. 20).

In this work he draws not only on scientific research, but also on a wide range of philosophical reflection. He complements this research and reflection with examples from his own observations of animals in the sea and on land. He makes his way through time and the many branches of the evolutionary tree, drawing comparisons and contrasts between different elements that might be called the precursors of experience and consciousness in animals and even, at some points, in plants. Along the way, he highlights developments of these precursors that he says anticipate something like the experience of contemporary animals generally and/or human beings in particular.

That’s the structure of his presentation generally stated; I found some of the particular discussions along the way to be especially interesting.

I’m particularly fascinated by his rather extensive discussion of research on split-brain patients, human beings whose connection between the two hemispheres of the brain has been severed. This severance has often been done in order to treat humans suffering from severe seizures. Severing the connection prevents a seizure that starts on one side of the brain from spreading to the entire brain. Work with these individuals highlights the fact that each of the two hemispheres specializes (to some extent) in particular tasks.

For example, in some studies, researchers ask a subject to describe an object that’s presented only to the left visual field, which feeds it to the right side of the brain. They then ask the subject to describe the object. However, speech function is centered in the left side of the brain, so the subjects are unable orally to describe the object that they see. Research by philosopher Elizabeth Schlechter points to “improvised communication between the two halves of the brain that takes place in the public world. For example, in a number of documented cases, the right side of a patient’s brain, which cannot speak, has tried to convey messages to the left side by writing with a finger of the left hand onto the back of the right hand. If the right hemisphere knows the answer to something and the left does not, the right may try to get a message across in this way. This was sometimes an attempt to subvert the point of an experiment, as the aim was to show images to the right side and see how much the left could say about them. The experimenter would see the finger writing and say, ‘Don’t write!’” (p. 152).

In other research the hemispheres are “disconnected” using with anesthesia, in one stage putting one side of the brain to sleep and in the next stage putting the other side of the brain to sleep. “At each stage the patient is tested on their use of language, to see what they can do with one half of their brain asleep. In most cases, when the left side is asleep the patient can’t speak. But the patient is still conscious, or seems so, at both stages: ‘During the test he would show me something, ask me to identify it and whether he had showed it to be before. …For the right side of the brain I didn’t notice anything different. For the left side — wow! When he showed me an object I looked at it and had that feeling you get when you can’t think of a word, like it’s on the tip of your tongue. Only that was true for all words — it was amazing! I had no words” (pp. 153f).

Some of the same specialization in the two hemispheres is apparently present in non-human animals, animals in which the connection between the two hemispheres isn’t as strong. Consider the toad: “If prey is brought from out of view into the left side of a toad’s field of vision, where most information goes to the right side of the brain, the toad usually won’t strike at the prey until it has crossed into the other half of the visual field, engaging the left side of the brain. The left, again, is the side that specializes in identifying food. The opposite applies, roughly speaking, when what is seen is a competitor toad rather than food” (p. 239). Godfrey-Smith suggests that the heightened skill in food recognition by the left side of the brain offsets the cost of the right side’s not recognizing prey as prey.

Another interesting point is the relationship between social engagement and brain development. Simply put, some animals are gregarious, preferring to stay in larger groups, often to provide a measure of protection against predators. “A complex social environment makes it worthwhile to develop recognition, memory, and strategic skills” (p. 181). (Interestingly enough, experiments with fish suggest that some are able to use this pattern-recognition ability to distinguish between blues and classical music.) It’s worth noting that many researchers suggest a similar process early in the evolutionary process leading to humans, when our predecessors moved out of forests into the Savannah, where they gradually developed cooperative skills (and the brains to manage them) that allowed them to flourish. Those who are more adept in such relationships have an evolutionary advantage — they’re more likely to survive long enough to pass these skills on to their offspring. (And, it seems, many human beings can also learn to distinguish between blues and classical music.)

These are just a couple of examples of the research Godfrey-Smith describes as he develops his argument for biological materialism. He makes what I think is a convincing case that experience itself emerged gradually as increasingly complex organisms developed more sophisticated ways of taking information about the external world in and then manipulating that world. He develops a simmilar narrative that shows how particular elements — “new kinds of engagement with the world through the senses and action…, subjectivity and agency…, [and] a tacit sense of self” (p. 258f) — eventually came together in human beings as what we now call consciousness or mind. He readily admits that there remain many questions to explore about this. And he argues that something like consciousness is more broadly distributed across animals and even insects than is commonly thought. There is, however, one way in which human consciousness is different from that of other animals, at least to some extent: “A feature of human cognition that really does seem to differ greatly from what goes on in other animals is something psychologists call ‘executive control,’ the ability to direct oneself on a task, suppress momentary urges, and marshal one’s various abilities in pursuit of a consciously represented goal. Through this side of human cognition, in concert with tools such as language as an organizer of thought, we can deliberately induce and control our offline journeys, rather than just having them happen. We can set out deliberately to some particular elsewhere, though we might also meander, drift off, and dream” (p. 258). As I read him, though, he sees this more as a difference in degree rather than an absolute contrast. Just as both experience and consciousness emerged gradually, so that there’s no particular moment which marked the move from absence of either to its full presence, so the line dividing our ability to focus from that of other animals is rather fuzzily and broadly drawn.

Surely it’s clear that I’m not a biologist. Nor am I conversant with the details of evolution generally or human evolution in particular. I’m not in a position to evaluate the soundness of his entire discussion. But I found the book to be extremely engaging, both in its general argument and in the particular examples he introduces along the way.

Currently reading

What to Save and Why: Identity, authenticity, and the ethics of conservation

• by Erich Hatala Matthes

A Series of Fortunate Events: Chance and the making of the planet, life, and you

• by Sean B. Carroll

A. J. Ayer: A life

• by Ben Rogers

Saving Time: A life beyond the clock

• by Jenny Odell

The Serengeti Rules: The quest to discover how life works and why it matters

• by Sean B. Carroll