kw: book reviews, nonfiction, psychology, zoology, animals, experience
The title and cover art (a Leafy Dragon, a kind of seahorse) of MetaZoa: Animal Life and the Birth of the Mind, by Peter Godfrey-Smith promise good thing inside, and that promise is abundantly kept. Thinking about thinking is the highest human art, and while Sturgeon's Dictum ("90% of everything is junk") holds especially true in this field, when the right ideas come together, the synergy is wonderful.
Dr. Godfrey-Smith has a prior book particularly on the mind of the octopus, Other Minds, and the work there is a springboard to his thinking about the full range of cognition, from the first evolution of neurons onward. MetaZoa begins with the eukaryotic cell—it could have begun with prokaryotes, but that would have added little and taken much more space—, a cell that senses and reacts to the environment, and is complex in its own right. However, there seems to be nothing we can do (so far) to determine whether amoebas, or critters like Euglena and Paramecium, have "experiences" or a "sense of being" in any way comparable to ours. Thus, the discussion proper begins with the simplest metazoans, those without nervous systems (so far as we know): sponges and placozoans.
A sponge is a metazoan—a multicellular creature—at its most basic: a collection of cells of three (some say four) types of cells, that produce spicules composed of either calcite or silica to stiffen a roughly vase-shaped "body". There seems to be a very simple system of cell-to-cell communication that allows the animal to react, quite slowly, to certain stimuli, perhaps including light. We still don't know much about sponges. Working with them is very difficult.
A placozoan is one of nature's great secrets: an animal typically smaller than one millimeter in diameter and 1/10 millimeter thick, that creeps among sand and silt grains using cilia for locomotion. This also implies some kind of cell-to-cell communication to coordinate the cilia. There are no cells with long projections that could serve as nerves for longer-range communication across the body. They eat by creeping atop a bit of algae and excreting enzymes to digest it outside the body, absorbing the products of digestion directly. These are even harder to work with than sponges.
The book doesn't discuss that favorite of experimenters, the nematode Caenorhabditis elegans (usually C. elegans), which is less than 1/10th the mass of a placozoan but is much better organized. About a third of its 959 cells constitute its nervous system, including a 56-cell brain. The author chose instead to move right along to coral polyps and to cnidarians in general, which have a minimal nervous system (in terms of percent of body mass), a neural net (no brain) that coordinates swimming motions in swimming polyps and grasping motions in sessile polyps, and also feeding behaviors.
A point the author makes repeatedly in the first several chapters: we shouldn't think of sponges, placozoans, corals or jellyfish (or any other animals) as "primitive". They have four billion years of evolution in their history, the same as we do. They are successful in their environments, or they'd have been eliminated.
With these simple animals, their similarities and contrasts, we begin a journey around (not necessarily "up"!) the tree (or network) of life. The author wished to puzzle out the origin of experience. Looking from "our" end of things, we, and a number of other animals (maybe a very large number), have something we call "consciousness", sometimes described as a "here I am" feeling. Are there animals that don't have this feeling? The smaller an animal is, the less we think it is "like us", and therefore capable of consciousness. Is this so?
Our pet calico cat is rather touchy, even peevish: it doesn't take much of a transgression on my part for her to give me a hurt look and stalk off. Another cat I had long ago would run across a carpeted room onto the linoleum in the hallway, and find himself skidding past the turn into the bedroom. Once he came to a stop, he would stroll, the picture of dignity, in the direction of the skid, as though he'd intended to go there all along. Unflappable aplomb! These animals have a definite sense of being "who they are". I call it consciousness, even if it is simpler than a human's.
Think about that: olfactory learning. It sounds like a lot can go on in the brain of a honeybee. But does the bee have a sense of "here I am" or "this is me"? While it cannot have such a sense at a human level, or even a mammal level, perhaps it does.
An aspect that Dr. Godfrey-Smith turns to in the last two chapters is gradualism. My statement above, "…even if it is simpler…" is along this line. Much is made of the phrase, "the lights are on". Some claim consciousness is like pregnancy: "Can you be a little bit pregnant?" I think to take such a purist attitude is misguided.
There may be a threshold effect. Is the neural net of a coral polyp (there is no brain) enough to generate a sense of presence, of "I am here"? Are the 56 neurons of a C. elegans brain enough? The million neurons of a honeybee's brain? Right in the middle of such a spectrum is the octopus, which has half a billion neurons.
The octopus's brain is quite different from a vertebrate brain. A ring of nerve tissue surrounding the gullet contains about 140 million neurons. A ganglion near the big end of each arm has about 45 million; those 360 million (45x8) plus those in the ring brain add up to 500 million. There is a lot of text in MetaZoa about whether this is a 1+1 situation, or 1+8, because the eight arms seem to act semi-independently. As I read, I remembered that 75% or more of human brain neurons are in the cerebellum, which runs the body, the "autonomic system". Our vaunted reasoning abilities, plus systems for vision, speech, sound, and the interpretation of our senses use 20% or so (16-18 billion neurons), and our emotions primarily reside in the limbic system, which has around a billion neurons. That in itself indicates that, if our feelings are entirely in the neurons, and primarily those of the limbic system (this is by no means certain), we use two whole octopus nervous systems to run our emotional being. So of course, octopus emotions (and they definitely have some!), belong to a much smaller set of neurons. But the octopus does behave as we'd expect of an animal that has a sense of self. Does a fish, or a bee? We can't say "Definitely not." Not yet, anyway.
Here I lean a lot on a concept I developed over many years. It is not anthropomorphism to attribute feelings and thoughts to animals. I look at it from the other end. The reason humans have feelings, thoughts, a sense of presence, and so forth is because our genetic ancestors had them, as do the other descendants of those ancestors. Have we developed all these things further than the rest? Some of them, at least, but perhaps not all!
This sense of being we have, which I consider belongs also to many animals, how far back does it go? When did an animal first experience it? We get a hint from electrical activity in brains themselves. When any neuron-containing animal is idle, a kind of synchronized cycling occurs throughout the nervous system. In humans, when we close our eyes we soon enter a state called "alpha", characterized by an overall brain rhythm around 10 Hz (it ranges from 8-13). Open the eyes, and the frequency roughly doubles to the "beta" rhythm. Pay attention to something, or get into problem-solving mode, and it doubles again, or more; the "delta" rhythm ranges from 30-140 Hz, usually centering around 40Hz. Do these patterns have meaning?
I immediately thought of regeneration and superregeneration in radio receivers (I am a radio amateur). Regeneration occurs when a tuned system oscillates in the absence of a signal. That is bad for radio reception, though it is what we want to happen in the signal generator of a radio transmitter. Regeneration also happens if a weak signal arrives in a system tuned to nearly self-oscillate; it is quickly triggered to oscillate. The stronger the incoming signal is, the more rapidly the oscillation begins. A superregenerative radio receiver is set to just barely self-oscillate, but the power supply is interrupted frequently (in old CB radios, this "squelch" occurred 30,000 times per second). During each short period, the oscillation's strength depends on the strength of the weak signal the receiver is tuned to detect. The resulting series of little peaks is filtered to remove the high frequencies (usually, above 5,000 or 10,000 Hz), and what comes through the filter is the audio that was carried on the incoming signal. This may sound complicated, but it is a cheap way to make a very sensitive receiver. It is an example of the use of a "keep alive" signal to enhance the system's performance. I suspect the various brain rhythms are akin to this, the beta rhythm being the main "detector". It is well known that our basic reception is limited to noticing fewer than 20 things per second, and the beta rhythm may be why.
I want to comment on one other matter. Vertebrate brains in particular are divided, at least in their upper sections, the cortex in mammals for example (the limbic system is only partly divided). When the connections between the cerebral hemispheres are cut, as is sometimes done to treat epilepsy, a split-brain person sometimes behaves as if there are two minds in one body. Certainly, if the brain of any smaller animal has sufficient "heft" to support a mind, there is room in half a human brain for a distinct mind. In an endnote to the chapter on the octopus, the author mentions a neuroscientist, Semir Zeki, who defends the view that we have several, or even many, distinct consciousnesses. Whether that is so, it does open the door to considering what happens in dissociation, in which a person develops "extra personae" as a response to extreme abuse. This used to be called multiple-personality disorder, but is now called dissociative disorder. The notion of true multiple personalities is mostly pooh-poohed, but it does seem to exist in some cases.
This and all notions that one brain can host multiple consciousnesses lend weight to gradualism. If there is a threshold below which a brain cannot support consciousness, it must be less than one-third of the 16-18 billion neurons of the typical human cortex, based on The Three Faces of Eve by Thigpen and Cleckley. I wouldn't have a clue where to place such a threshold, and Dr. Godfrey-Smith also declines to do so. He points out that, if lab rats and other smaller animals have a sense of self, we need to develop a better set of ethical standards for how we treat them. We have come a long, long way from the day René Descartes kicked a dog at a lecture and claimed that its cries of distress were "automatic" and did not signal pain or suffering.
It is worth considering that a smaller brain may actually be capable of thoughts that we would consider very high level, but they just take a lot longer to occur, given the smaller amount of "machinery" involved. However, time and time again our author expresses that more is going on than raw computation, and he explicitly denies strong AI, and equally denies that "uploading" the contents of a brain to a supercomputer will allow someone's consciousness to continue to run, unimpeded by having been removed from the body. Maybe we must have the computer also simulate all the rest of the body (endocrine systems at least!) for uploading to work, but I don't think so even then. That is a philosophical end of things that gets beyond how the mind came to be. It'll take another book (I hope he will) to delve into the future of the mind.
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