Purpose and Desire Read online

  Except . . . the clockwork homeostasis model for body temperature regulation actually has not stood up well, not because it was unsuccessful, but because its success was always imperfect. Thanks to Norbert Wiener and his formulas, one could, in principle, predict the behavior of any cybernetic system from the system’s measurable parameters of operation: the sensitivity of the sensors, the responsiveness of the controllers, the time lags between sensing and response. If body temperature was controlled by a cybernetic controller, then Wiener’s mathematical formulas should enable one to calculate the specific response of body temperature to known perturbations. That opened the door to some real science: one could predict the behavior and see experimentally how close the agreement was between predicted behavior and reality.

  Figure 4.5

  An early cybernetic model of temperature regulation, elaborated to include inputs of skin temperature with brain temperature in the preoptic anterior hypothalamus, feeding into “blackbox” integrating centers for heat loss and heat conservation.

  Invariably, these experiments showed encouraging agreement with the cybernetic model, but also some significant departures. What, then, should a “real”—that is, a reductionist—scientist do? Do we question whether the beautiful model is a reliable facsimile of the real system at work, or do we tweak the model to make it behave “properly,” that is, more like the observed behavior? Invariably, tweaking the model was the preferred choice, which meant generating a more complex cybernetic model that, it was hoped, could more precisely model the actual behavior (Figure 4.5). And again, invariably, these new models produced some agreement, and new discrepancies, which necessitated more complex models, which led to new discrepancies, and . . .

  Figure 4.6

  A more complex modern model of the clockwork homeostasis for body temperature regulation. The details are less important than the gestalt: the complexity, the large numbers of question marks, and the dotted lines with arrows that indicate an uncertain neural pathway.

  You get the idea. This endless tweaking and fixing of the purported cybernetic machinery of thermoregulation proliferated into baroque assemblages of multiple controllers, sensors, and effectors distributed throughout the nervous system and body, all arising ad hoc as explanatory needs multiplied (Figure 4.6).25 If this sounds familiar, it should: it is the same motivation that led to the eighteenth-century proliferation of vital essences that so perturbed François Magendie. Now, one can convincingly argue that this is nothing to be troubled over. Are not organisms extraordinarily complex? Would not we then expect their cybernetic control systems to be commensurably complex? And is it not perfectly natural that the “proper” scientific trajectory should be to ever more complex cybernetic models until they ultimately match the complexity of the thing being modeled? For the scientist working today, this logic is sound and compelling. But models can be a siren song, particularly if the model is beautiful, and this can lead scientists into an unreal realm where the model supersedes the thing it seeks to explain.

  There certainly is historical precedent for this, for it was this very cycle of seduction, disappointment, and requital that drove and sustained for centuries the unreal Ptolemaic picture of the geocentric solar system. Slight discrepancies in the motions of planets and stars could be fixed by just adding one orbital epicycle here, but that’s not quite right, so just another epicycle there will fix the problem, and so forth and so on. These accumulated fixes and tweaks made for a remarkably accurate model for the motions of the heavenly bodies, even as they made the Ptolemaic model physically absurd.*26

  Similarly, the search for the clockwork thermostat has led to ever more complex and sophisticated cybernetic models, until the clockwork thermostat finally converged on the ultimate complexity of the “many little lives” metaphor. Rather than nerve cells and sensors serving as dedicated components in neural “circuits” that are wired together into a well-tuned cybernetic computer, there are innumerable little conversations, spreading of gossip and vague rumors, and the “weather” inside the brain. Individual nerve cells seem to be homeostatic agents unto themselves, capable of sensing temperature, making comparisons, and even bringing about a degree of self-maintenance of temperature on their own.27 Just as Henderson and Cannon had been led by their studies back to the “many little lives” metaphor, there too has the cybernetics of thermoregulation been led. There is no master thermostat; every cell is a “-stat” of some sort. The steady temperature of the body somehow emerges from the endless conversations and negotiations between these innumerable many little “-stats.”

  The metaphor of the clockwork homeostasis runs into deeper trouble when it ventures beyond the sheep and dogs that served as the early “model” organisms for cybernetic body temperature regulation. Creatures such as these were well-suited as experimental “test beds” for exploring the clockwork thermostat, because they have in common one style of temperature homeostasis, namely, high and steady body temperature that is controlled by high rates of internal heat production—the internal “fire of life” that, for a mammal like a sheep or a dog, burns off directly as heat as much as 90 percent of the energy in the food consumed.28 This “style” of temperature regulation, called endothermic homeothermy, describes our own form of temperature homeostasis, so it’s very important to us; but endothermic homeothermy actually is rare among the animals. It is found mainly among mammals and birds, but for the rest of the animal kingdom, a broad diversity of body temperature “styles” prevails, ranging from just drifting along with the temperature of the environment to actively seeking thermal comfort29 to occasionally taking a kind of regulatory respite, as torpid animals do.

  Among these diverse styles of thermoregulation is a body temperature that is determined not by internal heat generation, as it is in mammals and birds, but by the clever exploitation of external sources of heat. Creatures that regulate their body temperatures in this way were long called “cold-blooded,” but this is a misrepresentation. Many lizards, for example, can maintain impressively high and steady body temperatures through the day.30 Where a mouse in the cold morning might burn through its food reserves to warm its body, a lizard might spend the early morning hours sunning itself on a rock, capturing solar heat to offset its body’s heat loss to the cool morning air. Once the lizard’s body has warmed sufficiently, it may begin making forays into cool parts of its territory to find food, cooling as it forages. When it starts feeling too cold, the lizard might then find a sun fleck to soak up a bit of heat to warm its body, then go off into the cool to forage some more. By shuttling all day between hot spots and cool spots, warming up a little now, cooling a little then, again and again, the lizard can keep its body within a narrow band of temperatures.31 In short, a supposedly “cold-blooded” lizard not only can be “warm-blooded,” it can be remarkably adept at regulating its temperature behaviorally.*

  Behavioral regulation of body temperature poses some interesting challenges to the cybernetic metaphor for homeostasis. Like mammals, lizards also have a POAH in their brains, and as in mammals, the lizard POAH seems to play a role in the lizard’s regulation of its body temperature.32 The behavioral dimension of lizard thermoregulation throws a spanner into the cogs, however, and it’s well-illustrated by the matter of fever. Lizards that have a bacterial infection also develop fevers, and their fevers are simultaneously like and unlike the fevers of endothermic homeotherms such as ourselves.33 Whereas a febrile homeotherm drives up its body temperature by ramping up its heat production, a lizard develops a “behavioral fever” that is brought about by adjusting its shuttling schedule so that it spends proportionally more time in warmer environments and less time in cooler environments than it would if it were healthy. Thus, the febrile lizard’s body temperature oscillates around a higher mean value than a healthy lizard’s does. So far, so good: we can imagine that the lizard has a “behavioral thermostat” that has been turned up by fever, just as in a febrile rat.34

  There’s a subtle problem with
this analogy, though, because the notion of a cybernetic “controller” becomes blurred when the thermoregulation is behavioral. A cybernetic thermostat is an attractive metaphor when it is the physiology of the body that is being driven by the cybernetic machine. There, the cybernetic machine holds the whip in its hand—that’s why it’s called a controller, after all. When I have a fever, I have no choice in what my body temperature is. It simply is what it is; my body temperature is controlled by the machine running my body, set at whatever the machine says, irrespective of time of day, how I’m feeling, what I’ve recently eaten, and so forth. This is not the case with behavioral fever, nor is it, as we shall see, the case for behavioral thermoregulation in general. A febrile lizard has a high body temperature because, in some sense, it wants to have a high body temperature, and it acts on this desire in a way that is impossible for me to do. In what sense, then, is the lizard’s brain “thermostat” driving its body temperature in the same way my brain “thermostat” supposedly does?

  Things get fuzzier still when we explore how lizards maintain their body temperatures in the real world. There, body temperature is not just physiology; it is a broader ecological problem because the body temperature affects nearly all aspects of how the lizard fits into its environment: its adaptation, in a word. A lizard’s body temperature affects how fast it can move, how big its territory is, how intelligent it is, how successful it is at catching prey, how effectively it digests its food, and how successfully it reproduces.35 What temperature the lizard maintains is therefore the result of a careful balancing of benefits against cost.36 Some of these are so-called opportunity costs. When a lizard basks on a rock, it is forgoing opportunities to catch food, to find mates, and to fend off rivals. There is also frank risk. Because good sun-basking sites are often well-exposed sites, this makes the lizards that use them conspicuously visible and susceptible to being snatched up by a sharp-eyed predator. What temperature a lizard maintains will therefore be determined by a balance sheet of sorts. If, for example, sunny spots are abundant, as they might be in an open desert, the risk of predation that accrues to sun-basking in any one spot is low: every place in an open desert is equally visible, so there is small additional risk to basking in a particularly nice spot. Opportunity costs might be similarly low: a lizard lying on a rock in an open desert landscape can easily keep a watchful eye out for potential morsels of food strolling by while it basks and it can easily pounce when something juicy turns up.

  The balance sheet can change quite a bit for lizards living in more sheltered environments. If you live near some woods, take a walk through them and look around as if you were a lizard looking for a place to bask in sunlight. In a typical forest, suitable basking spots are limited to the scarce flecks of sunlight that stream between gaps in the forest canopy. Now try to take the lizard’s-eye view of how to maintain a particular body temperature. The scarcity of suitable basking spots boosts the frank risks to a basking lizard because this makes any prospective predator’s job easier. If the predator wants lunch, it just needs to find a sun fleck, hang around there, and the probability will be high that a tasty lizard will take the chance and try to bask there: dinner is served. There are also increased opportunity costs. When sun flecks are scarce, the lizard must leave a large territory unpatrolled while it takes time out of its day to bask.

  This leads to an interesting prediction. In an open sunny environment, there are few costs to pay and small risks to take if a lizard living there wants to have a high body temperature. A lizard living in a forest where sources of heat are scarce pays stiff penalties to attain the same temperature. The actual body temperature a lizard maintains should therefore correlate with those costs, so that lizards in open and sunny environments should sustain higher and steadier temperatures than do lizards in more sheltered environments. At least for lizards inhabiting Puerto Rico, the prediction is largely borne out.37 Furthermore, there appears to be little genetic variation that accounts for the different body temperatures maintained by lizards inhabiting different environments.38

  It appears, then, that lizards actively take stock of their environments and determine what temperature they will sustain based upon a perceived matrix of costs, benefits, and risks. If the costs are low, then get that body temperature right up! You’ll be faster, more agile, more intelligent, and you’ll go through your meals more quickly. But if the risks are too high, the lizard will let its body temperature slide. Now, I have to make the obligatory disclaimer that I am not saying that the lizard actually thinks these things. The point I’m trying to make is that the body temperature of a lizard is not so much the outcome of a machine regulating it, but is a kind of cognitive state.39 This is where things begin to get even more metaphysically hairy for the metaphor of the clockwork homeostasis, because it opens the door to that anathema of modern biology, intentionality.

  In The Tinkerer’s Accomplice, I argued that cognition and intentionality are flipsides of the same underlying phenomenon of homeostasis. Cognition involves forming a coherent mental image of the “real” world, and the coherence of that mental image depends upon a homeostatic brain. Intentionality is the obverse of this: intentionality is the reshaping of the real world to conform to a cognitive mental image. This also depends upon a homeostatic brain. In short, all homeostasis involves a kind of wanting, an actual desire to attain a particular state, and the ability to create that state. The nexus of strivings and desires in, say, a lizard might be completely alien and inaccessible to the strivings and desires in, say, ourselves, but they are no less strivings and desires all the same. A clockwork vision of homeostasis cannot ever hope to capture this dimension of the problem, because in what way can a thermostat “want” to achieve a particular temperature in the same way, say, a lizard might “want” to do the same?

  We now come to the nub of the problem that will occupy the rest of this book. I mentioned in the first chapter that Darwinism, as Darwin himself conceived it, was primarily a theory of evolution driven by adaptation. Without adaptation, natural selection cannot work. Darwinian evolution therefore relies upon a coherent theory of adaptation.

  As we have seen, physiology already has in its pocket a robust theory of adaptation in the living organism. It is the Bernardian concept of homeostasis, the self-driven tendency of living things toward apt form and function. The question we address for the remainder of this book is whether the physiologist’s conception of adaptation can be useful to modern Darwinism’s conception of adaptation. The prevailing answer to this question among evolutionists has long been “no.” Adaptation is certainly relevant to the Darwinian idea, so the argument goes, but it is not adaptation per se that is important, but heritable adaptation. Both physiologist and evolutionist may use the same word—adaptation—but they mean very different things by it. When we are talking about physiology, or day-to-day life, or adaptation in the physiological sense, we can tentatively speak of purpose and desire and still remain on the right side of intellectual respectability. We welcome as fellow scientists the practitioners of psychology, behavior, sociology, and economics—disciplines we sometimes indulgently call “soft” science, compared to the “hard” science (i.e., strictly mechanistic) many biologists yearn to practice.

  It’s a different story altogether when it comes to the problem of evolutionary adaptation. Speak of purpose and desire for evolutionary adaptation and you’ll be quickly lumped in with God-botherers and other intellectually malodorous tribes. There’s a reason for this: the physics envy that permeated biology in the early twentieth century has, among other things, driven a thick wedge between physiological adaptation and evolutionary adaptation. This is the fractiousness that comes with epistemic closure: it is one reason why we do not presently have a coherent theory of adaptation, nor a coherent theory of life, nor a coherent theory of evolution.

  The path to a coherent theory of life, and hence a coherent theory of evolution, therefore depends upon there being a coherent theory of adaptation. As we hav
e seen, physiology has such a theory but it contains at its core a difficult-to-digest nut. Adaptation in the physiological sense is really a phenomenon of cognition, striving, and desire. Living systems have to be aware of their surroundings, to be aware of what they are, and to strive, like the imaginary Mukurob of Chapter 2, to a particular state. This is the radical implication of Bernard’s dangerous idea.

  Modern Darwinism rejects this solution to its adaptation problem precisely because it contains those troubling concepts of purpose and desire. Modern evolutionism rejects this solution, not because it has disproved it, but because it is philosophically inconvenient. The virtue of natural selection is that it reduces evolution to the operation of a machine, and it is impossible to attribute purpose and desire to mere machines; therefore, there can be no purpose and desire in evolution, as the Four Horsemen of the Evocalypse have instructed us.

  Yet, Darwinism, and evolutionism in general, did not always have trouble with the idea of evolution as a purposeful, striving phenomenon. As you might suspect, there is a narrative afoot intended to make us think otherwise.

  5

  A Mad Dream

  Enduring brutal winters is a point of perverse pride in upstate New York, where I now live. Since I grew up in coastal California, winter’s charms are mostly alien to me, but I am certainly not immune to the charms of winter’s end. After months of lowering gloom, the sunlight suddenly just seems a little more . . . optimistic. There’s the first day you can leave the house unburdened by the heavy winter coat and the several layers of insulation you have to carry. Taking a deep breath outside suddenly no longer feels like shooting back a slug of white lightning but more like savoring a snifter of fine cognac, with the air redolent of the hebetic aroma of soil suddenly unlocked from winter’s icy embrace. The experience is all the more intense for having endured the winter, which I suspect is the real source of the pride, a pat-on-the-back for all the shoveling and salting and deicing that are now over, at least until the next bout with winter, queued up to start again in about six months’ time.