Purpose and Desire Read online

  It is one thing to say that there is an intelligible sequence of connected events that leads living things to appear to strive, just as in a machine, cogs turn axles that turn other cogs, ad infinitum. But that appearance of striving in no way negates the quality—the reality—of the striving of something that is alive. Machines might appear to strive, they may come unnervingly close to actually striving, but it strains credulity to assert that a machine can ever want anything, to have desire. Indeed, it actually seems more straightforward simply to acknowledge life’s actual striving and desire, compared to some of the tortuous reasoning that today goes into denying it.

  The stumbling block, of course, is that it seems hard to attribute striving and desire to anything living without getting into unscientific ways of thinking. How do you do an experiment with desire? To be sure, you can tweak chemicals in the brain and body or tickle a nerve cell here and there and see what happens. But, in doing so, have you really gotten to the nub of what striving and desire are? In short, we find ourselves at the Hobson’s choice I introduced in the Preface: either acknowledge striving and desire as real but sacrifice being a scientist, or become a scientist and deny the reality, independent of mechanism, of striving and desire. That’s a devil’s bargain we don’t have to strike, though, because there actually is a rational explanation for striving and desire, and the font of that living desire is this strange and misunderstood concept of homeostasis. This makes homeostasis a very subversive idea, quite unlike today’s tamed and neutered version of it.

  The credit for the concept of homeostasis goes to Charles Darwin’s French contemporary, the great physiologist Claude Bernard (1813–1878). I will have more to say about Bernard momentarily, but for now let us simply state the matter as he did, in a famous aphorism from his 1865 master work Introduction à l'étude de la médecine expérimentale (Introduction to the Study of Experimental Medicine): “La fixité du milieu intérieur est la condition d’une vie libre et indépendante.” Or, in English, “The constancy of the internal environment is the condition for a free and independent life.”

  To approach homeostasis as a problem of mechanism, as we do today, you necessarily see it as an outcome of a type of causation: how event A (say, reduced body temperature) leads to event B (sensing the change of body temperature) and hence to event C (shivering to heat the body) and … back to A (restored body temperature). If you parse Bernard’s aphorism carefully, though, you can see that was not really the meaning Bernard intended to convey.

  Bernard did not phrase his aphorism as an invitation to discover a mechanism of life. Rather, his aphorism is a statement of the nature of life. Specifically, homeostasis is not the outcome of life; it is life’s antecedent, and the question that Bernard is really inviting us to explore is more the “why” rather than the “how”: Why should body temperature be regulated? Not how is it regulated? Bernard’s focus on the “why” is what makes homeostasis as profound an idea as Darwin’s, which was also, at root, a theory of “why.”

  “Why” questions can be deeply unsettling, for within them lurks subtlety and beauty, and perilous truth. This is why Daniel Dennett famously characterized natural selection as a “dangerous idea.”3 Its “how” dimension is simple almost to the point of triviality, but its “why” dimension undermined most of the comfortable assumptions that prevailed in Darwin’s day about life, its purpose, and its past. In fact, it undermined them so completely that we now inhabit an entirely new intellectual landscape, one that is so comfortable to us today that we scarcely notice anything strange about it. But it is a landscape that would be quite alien to most of Darwin’s contemporaries.

  So it is with homeostasis. Its operation—its “how” dimension—is mere mechanism, but its implications for the “why” of life—Bernard’s main point, after all—is deeply subversive of the comfortable assumptions about mechanistic life that presently reign. It is, arguably, “Bernard’s dangerous idea,” the tonic that quenches Darwinism’s universal acid before it cuts too deeply. To fully understand life in all its manifestations—its function, its evolution, its origin—we need to unpack the wonderful subtlety of homeostasis, as Bernard himself intended.

  We can illuminate the strangeness of homeostasis with a little thought experiment. In southern Namibia, near the tiny town of Asab, there stood for many millions of years a famous rock formation, commonly known as the “Finger of God,”* although it was officially known by its more descriptive Nama* name, the Mukurob, which means “Bottle.”* The Mukurob was a 34-meter-tall column of sandstone, supported on a thin pillar of softer mudstone below (Figure 2.1a). The softer rock had been relentlessly eroded by wind, leaving the Mukurob perched on an increasingly precarious pedestal, until the thing finally collapsed in 1988 (Figure 2.2). Before that, it had been one of the most photographed rock formations in the world.

  Figure 2.1

  The Mukurob. a, As it stood before 1988. b, Equilibrium of forces in the static disequilibrium of the Mukurob. The Mukurob’s center of mass is represented by the target. c, The Mukurob as a focus of dynamic disequilibrium.

  The Mukurob’s collapse was an economic blow to the impoverished Nama sheepherders who lived nearby, because it had provided a modest stream of revenue from tourists willing to part with a little cash for an enterprising guide, or a springbok skin rug thrown into the bargain. Once the Mukurob toppled, the trade in photography of unusual rock formations shifted north in Namibia to the Vingerklip (“Finger Rock”), which has been a boon to the more northern Damara tribes on whose land it sits. The Nama have not taken this lying down, though: by the peculiar logic of ecotourism, this has led to an effort to erect a fiberglass replica of the Finger of God, an idea that was shelved for a time as being a little on the crass side but that, as of this writing, was enjoying a comeback.*

  Figure 2.2

  The Mukurob in 1998. The remnants of the mudstone pedestal still stand at the summit. The Mukurob itself at equilibrium consists of the rubble field strewn to the left down the slope.

  I am telling you about the Mukurob because it offers some interesting object lessons in matters of stability, equilibrium, and disequilibrium—matters in which homeostasis is deeply embedded and which are easily and often confused. To clarify why homeostasis should be seen as something more than mere mechanism, we need to unpack those assumptions.

  Let’s start with the idea of stability, to which homeostasis is often likened. We describe something that is unchanging as “stable,” so when we observe, say, a body temperature that is unchanging, we naturally speak of a “stable” body temperature. Stability, meanwhile, is often conflated with a state of equilibrium, balance, or repose. A “stable” body temperature is somehow an equilibrium body temperature. Therein lies the first trap.

  All physical systems tend to go naturally from instability to stability, and it is the Second Law of Thermodynamics that tells us so. Stability and equilibrium thus do indeed go together, but this usually comes about when a system comes to rest at some minimum state of repose. This description applies to the rubble pile now strewn at the base of the erstwhile Mukurob’s mudstone pedestal. However, this state does not apply to the Mukurob as it once stood. The Mukurob itself came to be at a stable equilibrium in 1988 when gravity, erosion, and a nudge from a temblor eventually brought it stably to rest as a rubble pile at the lowest position it is likely to occupy. In a living system, this kind of stability is not homeostasis; it is death.*

  A somewhat more subtle idea is that homeostasis is a peculiar kind of instability. That’s a better way to think about it, but instability comes in a variety of flavors, some of which qualify as homeostasis, and some of which do not. For example, it is clear in hindsight that the Mukurob was unstable. Before its collapse, the Mukurob seemed to be stable, but this state was maintained through a straightforward balance of just two static, but precariously opposed, forces. Gravity pulled the Mukurob down with a force directed vertically downward through its center of mass. The Mukurob neverthel
ess stayed steadily in place because its weight was met by an equal and opposing force pointing upward from the mudstone base (Figure 2.1b). As long as these two forces met head-on, the Mukurob stood—steadily out of equilibrium.

  Now here is the crucial thing to understand. As long as the forces were aligned, the Mukurob’s disequilibrium stood steadily with no effort being exerted to maintain it. It did, however, take effort to undermine the stability. The Mukurob collapsed following some perturbation, an earthquake or an errant gust of wind, which set the Finger of God wagging ever so slightly until its center of mass was pushed sufficiently out of line with its mudstone base so that it toppled over. So, we can say that before its collapse, the Mukurob was in a kind of static disequilibrium, persisting as long as the precarious balance of forces was maintained but collapsing catastrophically when the balance was sufficiently perturbed.

  This doesn’t seem to fit homeostasis very well either: the most striking thing about life is how robust it is in the face of perturbation, compared with how frail the Mukurob’s fragile static disequilibrium turned out to be.

  Homeostasis is also a form of disequilibrium, but to appreciate how it differs from the Mukurob’s static disequilibrium, we must let our imaginations run loose a bit. Now, imagine the Mukurob not as a solid mass of sandstone sitting on its narrow pedestal but comprising an ephemeral cloud of loose sand grains arranged in the Mukurob’s distinctive shape. In this fantasy, there is nothing holding these sand grains together, and so gravity pulls them down in a sandy cascade raining down from the imaginary ephemeral Mukurob (the “outward disorganizing flow” in Figure 2.1c). Ordinarily, this ongoing loss of sand would make the Mukurob disappear, but—here is the strange part—imagine the Mukurob persisting, seemingly stable in its appearance, despite the cascade of sand falling from it. How can this happen?

  There is only one way: the continual loss of sand must be offset by another stream of sand flowing into the imaginary Mukurob, just as fast as it is lost (the “inward organizing flow” in Figure 2.1c). Even stranger, for the imaginary Mukurob to retain its distinctive appearance, this cloud of sand streaming into the Mukurob must become organized in precisely the shape and orientation of the sand grains that have fallen away. Even stranger still, this persists even in the face of the high winds, pelting rains, or baking heat and shaking earth that ordinarily would (and ultimately did!) perturb the real formation’s shape.

  Our imaginary Mukurob is not so much a thing, therefore, as it is a process—a continual flow of sand that first becomes highly organized and then dissipates into disorder as it falls, all the time maintaining a persistent state of highly specified and complex organization. In short, our fantastic Mukurob is not in a state of static disequilibrium, as the real Mukurob was, but is actually in a state of dynamic disequilibrium.* And whereas the static disequilibrium of the real Mukurob did not require any effort to maintain, work has to be continually done to sustain our imaginary Mukurob: the sand might fall out on its own, but it takes effort to lift and precisely arrange those innumerable sand grains streaming into the Mukurob’s particular form.

  This is the essential nature of homeostasis: it is life as a persistent dynamic disequilibrium. Remember this phrase and let us reflect on its meaning, for we will be coming back to it again and again through this book. Our imaginary Mukurob was a fantastic realization of this idea. Yet that self-adjusting confluence of forces is precisely what living things do as a matter of routine. It is what distinguishes the living from the inanimate world, and that world’s relentless slump into equilibrium and death. As I’ve said, homeostasis is an exceedingly strange idea.

  This brings us to the dilemma posed by Bernard’s dangerous idea. If we were wandering in the desert and came across our imaginary Mukurob, the continually self-correcting rock of our fantastic imagination, we would probably assert that it is a trick and someone is secretly manipulating the sand. Or we may start believing it is governed by magical forces. The beauty of homeostasis as Bernard phrased it—as the constancy of the internal environment as a condition for life—offers us a way to avoid falling into that trap, but it means we have to think about life and its nature in some unaccustomed and perhaps uncomfortable ways.

  Yet open any modern textbook on physiology, and you will not find any strangeness there. This is because the weird mystery of homeostasis has been captured, corralled, and tamed behind a philosophical fence of mechanism, concerned only with the “how” questions, not the “why.”

  Being a physiologist, I can hardly disagree with this: the elegant and complex workings of homeostasis are endlessly fascinating, something akin to how a mechanic must feel when he or she opens the hood of, say, a Lamborghini Murciélago.* Once the thrill passes, though, both the physiologist and the mechanic are charged with focusing on practical things. Wonder will not tell us how the Lamborghini works or how to fix it; mechanism will. Indeed, wonder can positively get in the way. Still, one cannot look at a beautiful creation like the Murciélago and not see in it a kind of beautiful soul. Ah, we sigh as we awaken from our reverie and snap ourselves back to cool rationality, which is the talk of the romantic, not the scientist or mechanic. To talk of souls is to tread into the realm of the religious, of spirits, spooks, and goblins defining life, areas where the scientist or the mechanic is not allowed to go.

  Yet the nagging doubt remains. There is an awful* beauty in the Lamborghini that makes it somehow more than a machine, something infinitely richer than a mere machine. The same, exponentially squared, can be said of life’s awful beauty, and this was Bernard’s whole point. A rich understanding of life somehow has to account for this awful beauty. Where does it come from? What does it mean? More to the point, what if a relentless focus on mechanism leads us to a crabbed and impoverished view of what a Lamborghini is? Wouldn’t we have a richer understanding if we could know the soul of the Murciélago—even better, to know its soul, not just as a romantic, but as a mechanic?

  This is the dangerous dilemma that homeostasis poses to the modern science of life. We are called to focus only on the cogs and gears, but when we do so, we strip away a soul. We shove into the back of our minds something fundamental and enriching about the “why” of homeostasis, something that will give us the key to understanding its abiding strangeness. The dilemma is made all the more acute when we look back and see what Bernard was trying to convey: he was not asking us to admire cogs and gears, he was inviting us to contemplate a beautiful soul.

  In the Preface, I promised you strangeness, and we have indeed wandered into some very strange territory: of fantastic rocks, soulful automobiles, and wonderful life. I have led you here for a purpose, though, because abiding strangeness has permeated our thoughts about life for millennia. We do not teach students much about this strangeness. Rather, we dismiss it as an antiquated distraction from the real business of becoming scientists. We ignore this history at our peril, though, because the strangeness of the living organism was at the heart of Bernard’s dangerous idea.

  3

  Many Little Lives

  It is important that we get to know Claude Bernard and his thought a little better. His fame rests upon his founding of the science of experimental physiology, which is reflected in the title of his 1865 work Introduction to the Study of Experimental Medicine. The book is, in its own way, as foundational a work for medicine as Darwin’s 1859 On the Origin of Species was for evolution, and for similar reasons. Just as Darwin supposedly banished the ineffable from the phenomenon of evolution (a claim that we shall see is not quite true), so too did Bernard supposedly banish the ineffable soul from the phenomenon of life. Armed with a sharp mind, and sharper surgical tools, Bernard is renowned as the rationalist warrior who banished forever the ghosts and vital spirits that had, until then, haunted physiology and medicine.1 After Bernard, we would never go back to that world. Just to underscore the triumph, we have a scarlet letter we can pin on those tempted to backslide. It is a scarlet V, for vitalism, the V-word, to be pr
ominently worn as a warning to anyone who flirts with the idea to venture there, lest they, like Nathaniel Hawthorne’s Hester Prynne, be shamed and shunned.*

  But hold on. In the last chapter, didn’t I just write that Bernard was asking us to contemplate the beautiful soul of the organism? How does that square with the conventional narrative of Claude Bernard as the killer of vitalism? How can beautiful souls even have a place in such a mind as Bernard’s?

  But beautiful souls do belong, and here is why. If we shift the light slightly on Bernard’s hagiographic portrait, some interesting wrinkles pop out. During Bernard’s lifetime, for example, what we now regard as his signature idea—homeostasis—had almost no effect and was almost never mentioned or discussed by his contemporaneous colleagues. Nor was it mentioned by his eulogists.2 Indeed, physiologists didn’t really pick up on the idea until some seventy years after Bernard published his famous aphorism. When homeostasis did reemerge, early in the twentieth century, it was in a cramped and desiccated form, detached from Bernard’s original intent (more on that in the next chapter). Even today, there seems to be an enduring ambivalence about Bernard’s signature idea:3 a memoir of him published as recently as 1989 does not even mention the word “homeostasis” or refer to the idea.4 It’s almost as if we’re ever so slightly—embarrassed? And perhaps there’s reason to be, because Bernard, far from being the scourge of the V-word, was actually its vindicator.

  The roots of this contrarian conclusion are to be found in vitalist thought as it was transformed through the eighteenth and early nineteenth centuries.5 This is a history we generally do not teach to students today, in part because of the bad odor that presently clings to vitalism; but it also stems from the imagined separateness of science from all other intellectual endeavors. While historians and philosophers might find the history of vitalism a fit subject, we scientists might say this attention to finding the secret ingredient for explaining life would only be a distraction for those interested in “real” biology, which must be impeccably mechanistic and divorced from philosophy.6