Why can’t you tickle yourself?
It sounds like a silly question. Tickling is silly. But really, why can’t you tickle yourself? You can do everything else to yourself. You can talk to yourself, caress yourself, hit yourself, cut yourself, scratch yourself, hug yourself, you can even make yourself laugh by thinking of funny things. But you can’t tickle yourself.
The reason for this was debated by neuroscientists for decades. As often happens with questions like this, the scientific “answer” emerges, after a long series of observations and experiments. The technical “answer” has to do with parts of the cerebellum anticipating the actions of the other motor areas of the brain. But the sensible person is aware that this is not an answer, it is simply a re-description of the problem on a lower level. It’s like saying that the reason your boyfriend left you is that he went to the door and opened it and removed his belongings from your house, and then he put them in another house. He did it because he did it, in other words. That’s no explanation at all. We knew that there would be some sort of neural underpinning to the facts of our behavior, that much is obvious from a scientific view of life. What we want to know is why the cerebellum is configured this way, and what it means about the rest of the way our body works. Is it just a fluke? An accident? Does it matter? Why is it like this?
Most of us think about our bodies as a set of parts. We see each part as an object. We know these objects are connected, but still they look to us like individual pieces. I have hands, fingers, fingernails. I have a head, hair, ears, eyes, mouth, brain. Inside me I have other parts that I can’t see…heart, lungs, liver, intestines, and so forth. In my map of my body, most everything has a name, and I can imagine it sitting adjacent to the other things, like the funny song by the Delta Rhythm Boys “Dry Bones”… “the knee bone’s connected to the thigh bone; the thigh bone’s connected to the hip bone” … etc. All the parts of my body are individual objects, mashed together and pushing on one another in certain ways, like the axles and wheels and motor and steering wheel of a car.
Sometimes, if we imagine the body in a more holistic way, we realize that the parts are not really the point of the body. The point of the body is processes. If we think about the body as a whole, we find ourselves thinking about the paradox of the Ship of Theseus, the Greek parable that asks, “If Theseus goes on a long voyage, and along the way he replaces all the parts of his ship for new parts one by one as they wear out, can we properly say that he has the same ship when he returns as when he left?” We are aware that all the parts of the body change and morph, and that we lose molecules along the way and replace them with new molecules. The body-as-process seems really much closer to the truth about the mystery of life, that all things are replaced and renewed by living beings as they complete their mysterious cycles of metabolism and growth and development.
This body-as-a-process insight is a necessary first step. But I want to suggest that there is a further step, a step that makes the whole mystery of life begin to shine as bright as a torch, and gives us a much better language with which to contemplate our existence. If we study biology, we are vaguely aware that the body is not one process but many processes that are interconnected. The heartbeat, the inhalation and exhalation of the breath, the movement of the smooth muscle in the bowels, the excretions of the liver, the electrical pulses of the nerves, all these are happening simultaneously. Below these are many other processes, the Krebs cycle, the ion exchanges of the cell, the translation of the DNA into proteins and the degradation and recycling of those same proteins. What we want to know is how these processes are interrelated, why they work the way they do. Re-describing the processes on a lower level can be helpful in some medical interventions. But it leaves us still mystified as to the overall rationale of the organismic phenomenon, the purpose of life.
When I was a young boy, I wrote a letter to my uncle, who is a life scientist, to ask him questions about the body that my father felt he could not answer with enough specificity. They were very general questions, like “Why do we have blood?” and “How do we move?” I remember Uncle Robert’s answer to my question about movement. He wrote back, “Quickly and quietly so we’re not found out.” I remember the answer to this day because it surprised me that my uncle was joking, but even more, because it surprised me that the joke was not followed by an answer. My uncle intuited that an answer along the lines of “Your brain sends signals to your peripheral nerves” would not suffice. I wanted to know why. Why we have blood…he could answer that. It’s so that all the parts of our body can be supplied with the energy and nutrients they need to carry out their functions. But how do we move, and even more relevantly, why do we move, the answer to that question is a mystery to this day. We simply do not have an overarching scientific theory of how the body’s processes are linked together. In the words of Denis Noble, “The great shock of twentieth century science was that the human body was not susceptible to analysis.” The parts can be understood in tremendous detail, and many of their relations to other parts can be measured, but the whole is still unknown.
We do have a partial answer, an answer that is even more particulate. Neo-Darwinism, the dominant paradigm in evolutionary biology, explains that the human body is a machine for getting human DNA into the future. This subordinates all the other functions of the body to an ultimate rationale, genetic replication. Because this is enough of an answer for most people in the life sciences, we do not hear very much about the larger mystery. It is exceedingly rare for applied or even theoretical life scientists, let alone medical doctors, to acknowledge that this explanation is only partial. Inquiring about a further rationale for human life is viewed with suspicion, as if to be unsatisfied with the specificity of this description is un-scientific, and can only end in mysticism or appeals to organized religious theology.
But there is still an empirical mystery, not just a religious or moral one. Why do we get chronic inflammation? What causes cancer? Obesity? Why does exercise make us healthier? How can a set of molecules heal itself? We do not understand the basic reactions and interactions of the body as a whole system. We do not know what causes what. If we did, we could design drugs off the bench that would immediately work, as we design airplane engine turbines. Instead, drug design involves laborious and expensive controlled randomized trials to determine whether they will work, and if they are safe. When a drug company fields a new drug for trials, in spite of having often already invested millions in its development, they still have very little idea of whether the drug will work as intended. Imagine if we tested turbines this way…sending thousands of airplanes up to see if any of them crashed before the turbine could be sold. Some life scientists today write off much of this mystery as “stochasticity,” which is the scientist’s respectable word for the unknown.
To get beyond the body-as-process, we have to make a great leap of imagination. This new paradigm of life science, the one that will be unfolding over the twenty-first century, is going to wrap some of this mystery into a package that we can swallow and digest. It will help us enormously, but it will require the opposite habits of mind from the ones that brought us to the technological peak that we are sitting on today. We got where we are in science by breaking everything into little pieces, into tiny problems, to be analyzed. This is called reductionism. The only way to move further is through the opposite procedure. We must move into the age of holism, of integrationism. There is no other move that will help us. This does not mean abandoning the scientific appeal to facts, or data, or logic. It simply means developing holistic theories and testing them, hypotheses that stretch much further than the piecemeal theories we have today.
To return to my question, why can’t you tickle yourself, I have a though experiment. It comes from The Tree of Knowledge, and I have mentioned it before in this channel. Imagine the nervous system as a submarine operator who never knows that he is in the sea. He simply reads the instrument panel charts on his desk and turns the control knobs to keep the submarines most critical readings in line with their most important values. If any of them strays from the ranges prescribed, if he is too low or too high, or too near some line marked on his map, he adjusts the knobs and proceeds. For him, the operator, the knobs, the submarine, and the sea are one interconnected system of interactions. There is no sea, other than the changes on his instrument panel, nothing else exists for him. Only from the outside, from the perspective of the observer, can someone make a distinction between the submarine and its environment. For the operator there is no such distinction.
Since Plato, we are so accustomed to thinking as reality in terms of an objective “out there” and a subjective “in here” that we have forgotten that our nervous systems are set up like this. All organisms can only detect what they are set up to detect. None of them detect anything that occurs for another organism; they only detect what occurs for them. The photons that strike my eye are not the ones that strike your eye, the sound waves that I hear sound different for you, because you are in a different position in the room. What this means is that the outside of our bodies is not the outside of our organismic system. It is only an arbitrary division made by the observer. The true outside of our organismic system has a name, a scientific name. It is called the ecological niche.
The niche is not the whole environment. As Karl Popper quipped, “The spider that shares my bedroom shares my space, but it cannot hear my alarm clock because it does not share my niche.” The niche is not just the space the organism inhabits…it is all the sensitivities of an organism, and the way those sensitivities compel the organism to act. The niche is a way of relating to the environment that makes certain things possible. A mousehole is part of a mouse’s niche in a very different way than it is part of my niche. I cannot squeeze into a mousehole and take refuge from the cat. The cat, the mousehole, and the idea of refuge are connected in a very different way for me than for the mouse because we have different roles in the ecology of our environments.
The new scientific paradigm in biology will be a mode of thinking that takes account of this subjectivity of niches. It will be a mode, no less empirical and rational, that recognizes that there are differences between organismic systems that are defined by their limits, and those limits are not the limits of their bodies but the limits of their perceptions. We are affected and shaped by everything that we experience, not simply by the intereactions of molecules underneath our skins.
Organisms have not made sense to us yet because we have not looked at them as integrated parts of a whole system, we have seen them as discrete objects in the objective reality of the world around them. We can never progress further while we maintain this view. Organisms are not part of a generalized objective reality that we can measure, they are parts of a niche that only they can measure. Only the organism’s body itself is set up to detect with precision its whole niche…that’s the definition of the niche.
It’s not enough to simply note in general that everything in Nature is connected in some way to everything else. We have to pay close attention to how it is connected. In order to see anything about the outside of its organismic system, we have to use our imagination. We can see the organism’s skin, its boundary, its cell membranes. These divisions are important, but they are nevertheless arbitrary, because energy and matter are continually passing through them, and what matters is how they do so. Although there are myriad interrelations between forms of life in an ecosystem, a niche is not infinite. A niche is only the set of interactions that provide motivations for an organism. For example, the wild yeast that lived on bread and other carbohydrate substances was presumably making penicillin for thousands of years
before we discovered its life-saving antibiotic properties. The yeast was in our environment, but it wasn’t really part of our niche, because it didn’t mean much to us. For most of recorded history, we never even expected the molds on bread to be caused by tiny animals, much less for those animals to produce a compound that could prevent infection. When we learned this, we began to behave differently toward certain parts of Nature.
These parts of Nature that we respond to are our niches. They form an envelope around us that we can never really escape from, and no one else can really inhabit with us. They form the boundary of stimuli that change our behavior, and in the larger sense, as a whole they provide our sense of purpose. To study the organisms body in isolation from its niche is like studying the excitation of cardiac cells without a view to the purpose these cells serve in contracting the heart muscle, pumping the blood, and allowing the organism to move. As Noble points out, if you looked at the cardiac cell alone without reference to the system it is nested in, its behavior would make no sense. But when you see that its behavior serves a function in the whole system, you can predict more or less how it will act.
So how does an organism relate to its niche as whole? What is the manner in which it is embedded? What drives the organismic processes as a whole? What gives us our life’s purpose? The answer is expectation.
We think of evolution as the history of changes in an organism’s body over the long term. But a niche-centered view of this process gives a whole different sense. The body has changed, but why? It has changed because over time, the niche has changed.
An organism’s body is set up for two purposes, to maintain homeostasis and to reproduce. Because the dynamics of reproduction and the replication of DNA are bottom-up processes that unfold from the consequences of small parts (the base pairs of the genome) they are easy for our scientific paradigm to study. But the dynamics of homeostasis are the opposite. Homeostasis emerges through a balancing act of all the stimuli in the niche as whole. The organism stays within its critical limits of temperature, pH, salinity, electric charge, and so on through myriad feedback mechanisms, none of which makes any sense in isolation. Every cell is cycling energy and nutrients in a highly dynamic, variable way according to a complex calculation. How does it all stay in balance? What controls them? What are all these homeostatic processes doing?
I am going to introduce a difficult idea here, but if you get it, it will change the way you see biology forever. There is not a good word for what I am describing, but the closest two are “guess” or “expectation.” The processes of homeostasis are acting in concert in the way that the words of a sentence stating an expectation are acting in concert. Each part only has meaning in terms of the whole. If I say I expect that “the sun will come up before I have breakfast,” I am relating the ideas of sun, time, myself, and breakfast in a certain way that has an internal logic. If it turns out that I eat the next day before sunrise, that logic will have been broken. The internal logic of my sentence only survives if each piece of its architecture is sustained by events. The whole thing has to survive as a functional unit. This is exactly the way that an organism has to survive. The body is a guess.
What is the body guessing about? How do you read its logic? The body is guessing about conditions inside its niche. It’s guessing about the presence of certain types of food, about predators, about air, water, shelter, locomotion. It’s guessing about the possibilities that it will encounter to do certain things to survive. The body of an organism is a hypothesis about how events will unfold inside the set of interactions that form its niche. When those conditions are just as the body expects them to be, the organism is at rest. Imagine a well-fed, well-rested lion lying in the sun with his mates, indolent and passive. Anything that is unexpected, anything which poses a threat to the internal logic of that organism, that disrupts the stability of that set of guesses, is highly significant for the organism, and causes a violent reaction. Imagine the scent of a man with a gun drifts into the nostrils of the sleeping lion. He leaps to attention, and runs away or fights.
This way of thinking explains several peculiar features about organisms. For one thing, any guess has a time dimension. If I say, “I think it will rain,” I must specify when I think it will rain for that to be a very useful guess, since it will eventually rain almost everywhere on earth someday. Will it rain today? In the next week? in the next year? The general statement that it may rain can’t be used to predict much, therefore nothing can be built from it. If I say, “I think it will rain approximately every 2.7 days according to a Poisson distribution,” I am saying something much more useful, that could be used to design many further guesses about gutters, drainage lines, irrigation systems, and so forth. This is why every organism, no matter how simple or small, has a circadian rhythm. Complex organisms, like ourselves, have multiple clocks in different organ systems. Our gut has a clock, our liver has a clock, our heart, which needs extra-good timing, has five separate clocks for redundancy, and the brain has a master clock in the suprachiasmatic nucleus that sets the whole system in motion all together in synchrony.
A circadian rhythm gives the time component to the organism’s guesses. The cells of the body can expect certain things to happen at certain times, and they all coordinate their activities accordingly. The liver cells expect the heart to beat at regular intervals to send them blood, and expects that that blood has been supplied with nutrients from the gut. The heart expects the lungs to breathe at certain times. The lungs expect oxygenated air in the niche. The whole body sleeps and wakes together, guessing that nighttime is the safest time to sleep. All of the chains of causation that support homeostasis run into and out of the body, but they all depend on clocks to stay in logical order. If the air in the room has less oxygen, the lungs breathe deeper and the heart beats faster. If heart beats too slow, the liver cells will die, along with the rest of the body. So each part of the system is highly sensitive to the other parts, and it tries to maintain its activity within the ranges that support all the other parts of the system. The system as a whole defines the purpose of each part.
Physicists understand that every physical system has boundaries, and that you have to define the boundaries in order to understand the behavior of the system. But the boundaries of a homeostatic living system are invisible. They exist, but you cannot see them or measure them precisely. Our current scientific methods have enormous trouble with quantities like this. Studying them empirically is hard, but not impossible. We know that a bat, for example, has hearing in a certain set of ranges, and we can set up a microphone to detect that range of sound. But in order for it to approximate the sound niche of the bat, the microphones will have to be placed in each of the bat’s ears, in such a way that they don’t interfere with its behavior and it can hear and interact normally.
This way of thinking also makes sense of conscious perception itself.
To be continued…
