The Uncashed Metaphor of Natural Selection
Justin E. H. Smith
1.
In their classic 1979 article, "The Spandrels of San Marco and the Panglossian Paradigm," Stephen Jay Gould and Richard Lewontin fault the adaptationist program for its failure to distinguish current utility from reasons for origin; its unwillingness to consider alternatives to adaptive stories; its reliance upon plausibility alone as a criterion for accepting speculative tales, and, as they put it, for "its failure to consider adequately such competing themes as random fixation of alleles, production of non-adaptive structures by developmental correlation with selected features… the separability of adaptation and selection, multiple adaptive peaks, and current utility as an epiphenomenon of nonadaptive structures." They announce that in the critique they are offering, they are proceeding in the spirit of "Darwin's own pluralistic approach to identifying the agents of evolutionary change."
Spandrels, or the tapering triangular spaces formed by the intersection of two rounded arches at right angles, are, as they explain, "necessary architectural byproducts of mounting a dome on rounded arches." In other words, you can't have an arch without a spandrel, and you need an arch in order to support a roof. If you ask the architect why he put the spandrel there, he will tell you you don't understand architecture.
Gould and Lewontin believe that this architectural example has much to tell us about biological evolution. In particular, they believe that many of our efforts to account for some given trait of an organism as having been selected-for is a futile project: it is often the case that traits were never selected at all by environmental pressures, but only came into being, like the spandrels, as 'free-riders' on the traits that these pressures in fact selected. The beautiful paintings that cover the spandrels are in turn the architectural analogue of exaptations, that is, features that were never selected-for, but once having come into existence as free-riders on different selected-for traits, turn out to have some fortuitous utility.
How do we know which traits of an animal are like the arches, and which like the spandrels? This might be harder to determine than Gould and Lewontin's predecessors had thought, but the difficulty only means that greater attention should be played to the role that the Bauplan of the integrated whole plays in evolution, not that natural selection as such should be rejected.
Jerry Fodor in contrast --in several books, including The Mind Doesn't Work That Way (his response to Steven Pinker's How the Mind Works), as well as in a fiery polemic with Simon Blackburn, Philip Kitcher, Dan Dennett and others in several recent issues of the London Review of Books-- wants to say that since any trait is always coextensive with another, it is impossible to say which of the two (or more) was the one that was selected-for. This is not in his view an epistemological problem, but an ontological one: the problem is not that we cannot know which trait was selected, but that it is meaningless to talk about the one or the other being the trait that was selected. It's all spandrels, and it's all arches, and there's no architect we might ask to help us tell the difference. Fodor writes:
"Getting minds in general, and God's mind in particular, out of biological explanations is a main goal of the adaptationist programme. I am, myself, all in favour of that; since I'm pretty sure that neither exists, I see nothing much to choose between God and Mother Nature. Maybe one can, after all, make sense of mindless environmental variables selecting for phenotypic traits. That is, maybe one can get away with claiming that phenotypes are like arches in that both are designed objects. The crucial test is whether one's pet theory can distinguish between selection for trait A and selection for trait B when A and B are coextensive: were polar bears selected for being white or for matching their environment? Search me; and search any kind of adaptationism I've heard of. Nor am I holding my breath till one comes along."
The consensus among Fodor's critics is that he has systematically misunderstood the point of Gould and Lewontin's argument. My own impression is that his argument is either irresponsible and stupid or so subtle that none of his adversaries, defending a status quo interpretation of the theory of natural selection, have been able to get it yet. The principle of charity pushes in favor of the latter view.
What Fodor wants to know is whether the polar bear's coat was selected-for because it's white or because it matches its environment. According to Blackburn et al., the familiar adaptationist account, which they do not see as in need of revising, would have it that "[i]n some ancestral population there was a variant type that differed from the rest in ways that enhanced reproductive success. (White polar bears, for example, more camouflaged than their brown confrères, were better at sneaking up on seals, were better fed and left more offspring.) If the variant has a genetic basis, its frequency increases in the next generation." For Fodor however, this is a "potted polar bear history," since "for any trait X that was locally coextensive with being white in the polar bear’s evolutionary ecology[, s]election theory is indifferent between ‘the bears were selected for being white’ and ‘the bears were selected for being X.’" A good theory, Fodor thinks, should be able to generalize over possible but non-actual circumstances, that is, it should be able to support relevant counterfactuals, and this is something that natural selection doesn't do.
If you are not satisfied with the polar bear story, Fodor also offers a well-known example from the real world: in a certain variety of foxes, whenever they are bred (by humans) for tameness, the offspring come out not only tame, but also floppy-- floppy ears, floppy tails, etc. These are ancillary effects that are observed in many species of domesticated animal, and they are much harder to account for, Fodor thinks, than the fit between arches and spandrels, since the connection between tameness and floppiness is, he thinks, perfectly arbitrary. (Actually, I can think of a perfectly plausible potted story as to why floppiness and tameness go together: it is advantageous to a domestic animal to be cute; roundness and softness are more likely to get a domestic animal to reproductive age than jaggedness, prickliness, and other visible vestiges of its feral past.)
Fodor seems to have failed to note that in each of the three cases in question --the spandrels, the whiteness, and the floppiness--, at least three different kinds of coextensiveness seem to be in play. In the first, we are dealing with two traits that are non-identical but logically coextensive; in the second, with two traits that are in-this-world identical even if they support different counterfactuals; and in the third, with two non-identical and contingently linked traits. It could have been the case that the gene for floppy ears be located somewhere such that breeding for tameness would have yielded tame, pointy-eared foxes, but there is no possible scenario in which brown bears could have matched their snowy environment, even if counterfactually they could have had a non-snowy environment, and all this for reasons having nothing to do with genetics.
In the case of the polar bear, the traits are not entirely identical, since again, as Fodor puts it, being white and blending with the environment support different counterfactuals. The environment could have been orange. So it is not that coextensive properties are indistinguishable in principle, but only that there is something wrong with natural selection to the extent that it fails to distinguish between them. Yet, one might reply to Fodor, environmental pressures do not operate on counterfactual states of affairs, only on the actual one, and in the actual one no decision had to be made as between whiteness and blending. In the sort of counterfactual, experimental situation Fodor imagines --such as painting all the snow orange--, the decider would be whoever set up the experiment, and not nature. So we seem either to have an identity of coextensive traits, or we have human agency, in which case there is a fact of the matter as to which of the two coextensive traits was selected. We will return to this point shortly.
Fodor has certainly been right to draw inspiration from Gould and Lewontin's argument in his crusade against the rampant plague of just-so stories that one hears from evolutionary psychologists. This crowd often assumes that what homo sapiens is in its essence is a hunting-and-gathering species, and that therefore whatever it is that we do must have some adaptive explanation as being somehow beneficial for hunter-gatherers. The result is often a caricaturing of human behavior of the most transparently Flintstones variety.
Gould and Lewontin however did not want to reject adaptation tout court, but only the view that every trait must be accounted for in terms of selection-for. How though do we distinguish the traits that may be accounted for in this way? Blackburn et al. appear to want to say that it is just obvious, while Fodor responds that it never is. A moderate balance of these two approaches would be to hold that adaptationism seeks to offer plausible accounts, based on counterfactuals, of what selection pressures would have to have enabled to come into existence so that the currently existing species might persist in existence. Certainly, a different standard will be brought to bear here than in laboratory science --plausibility rather than falsifiability-- but what other choice do we have? Fodor's ahistorical approach to the philosophy of mind seems to lead him to the rather extreme view that the past must remain off limits to science because it demands a different methodology than the most secure and unproblematic disciplines, such as aerodynamics, that he habitually holds up as models for his own domain of inquiry.
It is, again, interesting to note that the one really useful example of coextensiveness of traits in the biological world comes from an example in which human beings --fox breeding scientists, in the event-- are making the decisions, just like the cathedral's architects. There is a way to distinguish, not just in principle but in fact, which of the two vulpine traits in question was selected, since it was humans who were doing the selecting. Indeed, one of Fodor's arguments for the incoherence of the adaptationist program, an argument in my view more compelling than the argument from the lack of support of relevant counterfactuals, points out that not just in the case of the foxes and the polar bears, but with respect to all observed traits we can only arrive at a secure understanding of what was selected-for when we are able to interrogate the selecter. This is of course something we are never able to do in non-experimental cases, and so, for Fodor, any talk of natural selection is strictly metaphorical, and a great problem with Darwinism is that it never gave us any instruction as to how to translate this metaphor into a proper scientific account of things.
2.
Fodor claims that history is not relevant to the philosophy of mind, but in the end relies on historical considerations much more than he himself notices, admittedly not concerning the evolution of species, but concerning the history of Victorian natural history, and Darwin's place in it. He writes:
"[T]he present worry is that the explication of natural selection by appeal to selective breeding is seriously misleading, and that it thoroughly misled Darwin. Because breeders have minds, there's a fact of the matter about what traits they breed for; if you want to know, just ask them. Natural selection, by contrast, is mindless; it acts without malice aforethought. That strains the analogy between natural selection and breeding, perhaps to the breaking point. What, then, is the intended interpretation when one speaks of natural selection? The question is wide open as of this writing."
Given that nature lacks a mind, it, or its environmental pressures, can't really 'select' anything, any more than the ball in a roulette machine can select a color to land on. Metaphors are fine things, Fodor acknowledges, and "science probably couldn't be done without them." But they are supposed to be the sort of things, he thinks, "that can, in a pinch, be cashed. Lacking a serious and literal construal of 'selection for', adaptationism founders on this methodological truism."
Fodor is absolutely right, and not just about the current Darwinist orthodoxy, but about the historical Darwin himself, who explicitly borrowed the notion of selection from the domain of animal husbandry, and left it to his followers to cash the metaphor. Few before Fodor have noticed just how problematic is the legacy that Darwin has bequeathed: on the one hand, a thorough-going naturalism about how animals come to have the traits they have, and on the other hand a fairly blatant personification of nature as breeder.
Surprisingly, Fodor's critique of natural selection on this point echoes in important ways certain pre-Darwinian arguments against natural theology, that is, against the view that God's wisdom can be discerned in the order of nature. Most early modern natural theology took it for granted that the relation that God bore to his orderly creation was something very like that of a machinist to his machine. In the Dialogues on Natural Religion, Hume has the natural theologian Cleanthes declare:
"Look around the world: Contemplate the whole and every part of it: You will find it to be nothing but one great machine, subdivided into an infinite number of lesser machines… All these various machines, and even their most minute parts, are adjusted to each other with an accuracy, which ravishes into admiration all men, who have ever contemplated them. The curious adapting of means to ends, exceeds the productions of human contrivance; of human design, thought, wisdom, and intelligence. Since, therefore the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of nature is somewhat similar to the mind of man; though possessed of much larger faculties, proportioned to the grandeur of the work, which he has executed."
Hume, in the guise of Philo, proffers several arguments in reply to Cleanthes, but certainly the one most relevant for our purposes is the argument from the incomplete analogy at the heart of natural theology: because of our experience with artefacts and their artisans, we can tell the difference between artefacts and natural objects, and give an account of how the former sort of thing came into being. But in order to properly pick out a designed universe, we would need to have an experience of that universe's maker, which we obviously don't have. If you find a watch in the forest, then you are entitled to infer to the existence of a watchmaker, but only because you already know quite a bit about not just watches but also about watchmakers themselves: you can go, and may already have gone, to check out their workshops and examine their tools. But in the case of the world, we only know the 'watch', and come to think of it, Philo muses, there is nothing particularly watch-like about this particular world. In fact, notwithstanding the fashion for the watch-world analogy that had found such eloquent defenders in Boyle, Newton, et al., Hume prefers to return to a much more ancient and deeply rooted vision of the cosmos as, in Aristotelian terms, a natural being rather than as an artefact:
"Now, if we survey the universe, so far as it falls under our knowledge, it bears a great resemblance to an animal or organized body, and seems actuated with a like principle of life and motion. A continual circulation of matter in it produces no disorder: a continual waste in every part is incessantly repaired: the closest sympathy is perceived throughout the entire system: and each part or member, in performing its proper offices, operates both to its own preservation and to that of the whole. The world, therefore, I infer, is an animal; and the Deity is the SOUL of the world, actuating it, and actuated by it."
One of the important implications of such a cosmological model, Philo soon realizes, is that it compels us to think of the order in the world not so much as made, but rather as generated:
"[I]n examining the ancient system of the soul of the world, there strikes me, all on a sudden, a new idea, which, if just, must go near to subvert all your reasoning, and destroy even your first inferences, on which you repose such confidence. If the universe bears a greater likeness to animal bodies and to vegetables, than to the works of human art, it is more probable that its cause resembles the cause of the former than that of the latter, and its origin ought rather to be ascribed to generation or vegetation, than to reason or design."
The design of the world, in short, is more like a physiological process than a mechanical one. It is not that it does not have order or design, but only that this does not come from a machinist. It comes from a progenitor.
Hume's rejection of the argument from design is connected, one might argue, as much with the decline of the 17th-century mechanical model of nature as it is with the skeptical concern about the incompleteness of the watchmaker analogy. A world-machine would need a maker, but a world-animal could in principle be immortal, as it had been for Plato and later for the Stoics. What we need to consider, then, in order to understand the continuities and discontinuities between natural theology and natural selection, is precisely the ontological difference between artefacts and natural beings, which at once dictates the degree of control the 'designer', whether mortal or divine, may have in each of the two cases. Most significantly, natural machines can at most be sculpted by environmental forces or by intervention; they cannot be brought into being in the first place.
In this connection, on the reading of Darwin I shall proceed to sketch out, natural selection isn't so much a shift from theological thinking about design in nature, as it is a demotion of the designer from the role of creator to the role of modifier, and from the relatively prestigious role, one might add, of inventor, to the relatively humble job of animal breeder.
3.
In the opening pages of his 1859 masterwork On the Origin of Species, Darwin praises the expert knowledge and artisan's skill of domestic pigeon breeders. Their expertise, Darwin thinks, lies in their ability to discern barely visible traits and to amplify them over the course of generations by selecting appropriate mates for the pigeons who display them. "The key is man's power of accumulative selection," Darwin writes, "nature gives successive variations; man adds them up in certain directions useful to him. In this sense he may be said to make for himself useful breeds." Darwin goes on to praise the great skill of England's finest breeders, who, while admittedly working with pregiven Baupläne, are able to achieve results comparable to those of a divine creator:
"Breeders habitually speak of an animal's organisation as something quite plastic, which they can model almost as they please. If I had space I could quote numerous passages to this effect from highly competent authorities. Youatt, who was probably better acquainted with the works of agriculturalists than almost any other individual, and who was himself a very good judge of an animal, speaks of the principle of selection as 'that which enables the agriculturist, not only to modify the character of his flock, but to change it altogether. It is the magician's wand, by means of which he may summon into life whatever form and mould he pleases.' Lord Somerville, speaking of what breeders have done for sheep, says: 'It would seem as if they had chalked out upon a wall a form perfect in itself, and then had given it existence.'" [Italics added].
While Darwin is impressed by the way in which some skilled breeders of pigeons and other domestic species choose to summon into life new forms, he is just as interested in the way in which domestication has led to the emergence of new and unforeseen traits in animals and plants. This is the result, Darwin thinks, of a sort of 'unconscious' selection on the part of the human masters of domesticated animals:
"At the present time, eminent breeders try by methodical selection, with a distinct object in view, to make a new strain or sub-breed, superior to anything existing in the country. But, for our purpose, a kind of Selection, which may be called Unconscious, and which results from every one trying to possess and breed from the best individual animals, is more important."
Darwin repeatedly mentions that 'even savages' grasp the basic principles of selection. "If there exist savages so barbarous as never to think of the inherited character of the offspring of their domestic animals," Darwin observes,
"yet any one animal particularly useful to them, for any special purpose, would be carefully preserved during famines and other accidents, to which savages are so liable, and such choice animals would thus generally leave more offspring than the inferior ones; so that in this case there would be a kind of unconscious selection going on. We see the value set on animals even by the barbarians of Tierra del Fuego, by their killing and devouring their old women, in times of dearth, as of less value than their dogs."
Why does this supposed practice of the Yaghan matter to him? Darwin seems to think that "savages" provide the sort of low-level, unconscious guidance of the breeding of animals for preferred traits that even more closely approximates the guidance provided by nature than, say, the highly developed science of animal breeding described by Youatt, Somerville, et al. Nature is in short the ultimate savage: though herself uncultivated, she can't help but cultivate. Her selections are not like the conscious moulding of new races by England's finest breeders. But neither are they totally unlike this either. They are rather a low-level, mind-like force guiding the emergence of orderly forms.
Even in the case of England's expert breeders, the creative capacity involved is rather less than that of the artificer. "Man can hardly select," Darwin notes, "any deviation of structure excepting such as is externally visible; and indeed he rarely cares for what is internal. He can never act by selection, excepting on variations which are first given to him in some slight degree by nature." Selection, then, involves in all cases less of the creative power of transferring an envisioned form into matter than had earlier been imagined in the model of nature as machine and God as machinist. The selections a savage makes, moreover, involve less conscious imposition of an envisioned form than the selections of a master breeder, and nature's selections even less still. Selecting, unlike making, has to proceed with some pregiven thing, within the limitations dictated by its preexisting Bauplan.
Darwin's 'Mother Nature' then, as Fodor understands it, even if a theological hold-out or a metaphor still in need of cashing, is given a role in the designing of creatures rather less fundamental than that of the creator in natural theology. But it is just a metaphor, for all that, and Fodor is absolutely right to call it by its name. Fodor is right, I add, in just the same way that Hume was right to inveigh against the argument from design as resting upon an incomplete analogy.
Since, as Fodor might say, we can be morally certain that Hume never read Darwin, it might seem that what is at stake here is not so much the viability of Darwinism, but rather only of a certain philosophical position that has often been associated with Darwinism but that can exist without the fundamental insights of the theory of evolution and that indeed precedes that theory. Darwinism would then only be in serious trouble if it necessarily relies upon this philosophical position in order to explain the particular features of the world its defenders hope to make it explain. Kitcher and Coyne believe that "selecting-for" is largely a philosopher's invention, and would probably maintain that even if Darwin allowed nature to remain a bit too motherly in failing to cash the metaphor with which he begins the Origin, this in no way compromises the basic insight at the heart of the book, namely, that traits emerge gradually as individual members of a population that prove to be more fit for survival in given environmental circumstances manage to reproduce in greater numbers. They apparently do not expect Darwin the humble naturalist to offer a satisfying metaphysics of evolution, but only to tell us how evolution works. Fodor disagrees, on the grounds that unless a certain metaphysics is defended --that is, the one on which nature continues to have at least some minimal motherly capacity to guide the emergence of traits-- then we cannot coherently speak of one trait's being selected rather than another coextensive one. Therefore, Fodor thinks, natural selection does not support relevant counterfactuals, and is bad science.
4.
I will not come down on one side or the other, but instead will wrap things up by a brief consideration of what I take to be the alternative path Fodor would like to see the philosophy of mind, and perhaps all disciplines concerned with humanity and its place in nature, go down. Fodor mentions evolutionary developmental biology, or evo-devo, as a promising new path of scientific research, seemingly taking it to be a radical break with the Darwinian orthodoxy of the past 150 years, rather than taking it, as leading scholars in the field such as Sean Caroll do, as a supplementation of the adaptationist program. For Fodor, evo-devo appears to point to a way of accounting for adaptive phenomena largely by appeal to endogenous constraints on phenotypes, though he also admits that this is at best a plausible guess.
In the end, Fodor doesn't really believe that he or anyone else needs to come up with a convincing alternative to adaptationism in order for him to keep on doing what he does best, since in his ideal version of the science of explaining both behavioral and physiological traits, the function of a trait could come to be understood in the absence of any understanding of its evolutionary history.
But can this really be done? Fodor rightly notes that evolutionary explanation is always diachronic: it tells you what an organ's function is now by giving an account of what it "was selected for way back then." He goes on to ask:
"Imagine, just as a thought experiment, that Darwin was comprehensively wrong about the origin of species (we all make mistakes). Would it then follow that the function of the heart is not to pump the blood? Indeed, that the heart, like the appendix, has no function, and that neither does anything else in the natural order? If you're inclined to doubt that follows, then the notion of function you have in mind probably isn't diachronic; a fortiori, it probably isn't Darwinian."
Fodor considers the example of William Harvey's discovery of the circulation of the blood, announcing that "Harvey didn't have to look outside physiology to explain what the heart is for." But is that really the case? Did Harvey understand the function of the heart? He discovered the circulation of the blood, but he also thought that the blood was returning to the heart because in some deep sense comprehensible only within the framework of Aristotelian natural philosophy, it longed to return home. In other words, Harvey looked way outside of physiology in order to explain what the heart is for.
While we're at it, we may as well also ask whether a modern-day creationist can understand the function of the heart. It depends what you mean by 'understand'. Fodor and a pentecostal preacher in Alabama would both agree that the heart is for pumping the blood, but would surely disagree as to why the blood is being pumped at all. My hunch is that Harvey's complete account probably has more in common with that of the preacher than it does with Fodor's own. Yet it seems that Fodor is not interested in complete accounts, or at least not in accounts complete enough for the differences between his, Harvey's, and the modern-day creationist's respective opinions as to why the blood is circulating to come into focus.
Fodor disagrees with Dennett's assertion that "Darwin didn't show us that we don't have to ask ['why questions']. He showed us how to answer them." The disagreement seems to stem from a deep conviction on his part that in order to understand a thing one need not consider that thing's history, that an adequate explanation of a thing's nature does not require an inquiry into that thing's origins. It is a deep, deep question whether this is true or not. It seems that as a programmatic point, the rejection of historical considerations might be perfectly acceptable for the purposes of psychology and the philosophy of mind. But Fodor wants to move from the partis pris he had earlier taken up in his groundbreaking work in these areas in order to denounce diachronic accounts not just of human minds but of biological entities in general. Indeed, as a result of his aversion to just-so stories, Fodor seems positively hostile to the scientific effort to --as Elliott Sober describes the task of evolutionary theory-- reconstruct the past.
But if diachronic considerations are excluded outright from the scientific answer to the 'why' questions concerning the nature of animals and humans among them, non-scientists will be more than happy to offer their own diachronic considerations, in the form of biblical citation and crypto-creationist ID-theory, in their own very different answers to the very same 'why' questions. It is the minimalist answer to the 'why' questions --it is, in other words, the naturalistic account of functions-- that the adaptationist program makes possible, and that is all too easy to give up once it is assumed --and not just as a thought experiment-- that Darwin was comprehensively wrong about the origin of species. This is not to say that natural selection should be retained as the myth the naturalists offer up in answer to that of the supernaturalists. It should be retained as the most plausible hypothesis, towards which the consilience of all sorts of inductions invariably points, even if Fodor's concern --like that of Gould and Lewontin-- about runaway adaptationism is a legitimate one, and even if we must acknowledge with Fodor that there are some scientific, and naturalistic philosophical, endeavors, in which evolutionary considerations have no place.
--
Berlin, April 22, 2008
For an extensive archive of Justin Smith's writing, please visit www.jehsmith.com.
Justin,
Thanks for this thoughtful piece. It really is the first account I've seen to try to make sense of Fodor's recent work on evolution rather than dismissing it out of hand. One question: you argue near the end that Fodor wants to reject historical explanation entirely. My recollection however is that he accepts Darwin's account of common descent--accepts the historical narrative--while rejecting the mechanism that subserves the narrative. He's interested in "evo-devo" therefore because he thinks it might account for common descent in terms of endogenous variables.
Incidentally, I saw Fodor present some of this material last fall. In conversation, he likened Darwin to Skinner and himself to Chomsky on the particular point of the relevance of the environment.
Posted by: Jonathan | Monday, April 28, 2008 at 08:57 AM
Elegant and riveting!
In matters of evolution is fair to remember: Post hoc ergo propter hoc...
Posted by: Felix E F Larocca MD | Monday, April 28, 2008 at 09:07 AM
The example of the tame foxes is one that I've thought about before. It seems that in this case the traits could all be connected as a suite of characteristics exhibiting neotony; the carryin of juvenile traits in to adulthood. In the case of foxes it was selection by humans, but perhaps humans themselves selected neoteonal characteristics when the human social structure was becoming a genuine advantage early in our species history. As an example, a sociable adult in the reproductive stage has a mating advantage over an antisocial anti-social rival when in the context of the social group, in which there is little doubt, modern humans, in the inate gregariousness, are.
Posted by: doug l | Monday, April 28, 2008 at 12:00 PM
Can I make a donation to the 3QD copyeditors fund? Pieces as good as this should not make their readers guess at misspelled or missing words. (Also, wolves are lupine; foxes are vulpine.)
The difficulty with understanding "design" in nature (a problem bequeathed to the naturalists by Judeo-Christian theology) is that one must explain who or what did the designing. This (as Hume saw) is just hermeneutically incorrect. Fodor gets just as tripped up in it as the adaptationists (or the intelligent designists). Kitcher and Coyne's way out is to rehabilitate the old tautology that those that survive to produce more offspring survive to produce more offspring. And that's "how evolution works." This satisfies only those who secretly (even to themselves) believe in an invisible hand.
Design-talk is a dead end because there are no goals in nature; nothing to be designed for (not even survival, which is as transient as death.) This is where religion, at its best, still gets it right: everything passes away.
And even if there were some task to fulfill, could natural selection really be pulled off? With machines (as with breeding) we are continually at the mercy of best laid plans. The biosphere, for which no one has viable intentions, is in a constant state of negotiation at every level of examination. Nature's genius is in being creative and novel, in knowing how not to follow instructions.
Posted by: Chris Schoen | Monday, April 28, 2008 at 03:47 PM
Interesting post. Rather than take on the main issues, I'd like to interject a comment about the kind of evolution typically discussed in these philosophical essays. Discussion typically focuses on what practitioners call macroevolution, i.e the large changes in organismal phenotypes over very long periods of time. Why are polar bears white, why do tetrapods have four limbs, that sort of thing. My suggestion is that we can learn a lot about evolution from the study of microevolution, i.e. changes in the genetic make-up of populations over shorter periods of time. For example, the effects of harmful mutations are well studied: in every organism, in every generation, new DNA mutations arise, the vast majority of which are harmful to the organism. And, every generation, some percentage of these harmful mutations is eliminated from the population by natural selection. There is no great mystery to the operation of natural selection here...if an individual has a variant of a gene that reduces its chances of survival or reproduction, then fewer copies of that gene will exist in the next generation. This is called 'balancing selection', because here the result of natural selection is to remove new, harmful gene variants. If somehow this kind of selection stopped operating...if somehow every organism were mandated to have the same reproductive success regardless of its phenotype, then very quickly every species on the planet would turn in to mush, due to the accumulation of so many harmful mutations. So, the take-home message here is when considering the ceaseless generation of harmful DNA changes, natural selection has a very obvious, dominant role to play in evolution. Or else we'd all be mush.
Posted by: kyle | Monday, April 28, 2008 at 06:28 PM
Fantastically interesting, Justin -- thanks!
Posted by: Elatia Harris | Monday, April 28, 2008 at 10:05 PM
Great, thought provoking essay, but I think you are too charitable to Fodor. His argument is either far too subtle or too weak to have much meaning. You addressed some of those flaws in your essay, but I would like to toss in a few more.
Natural selection like Adam Smith’s invisible hand may be a bit of a truism – that which succeeds succeeds; that which fails fails, but that does not mean it is without value. Truism or not, it was not recognized until Darwin and he set off a cascade of new scientific thought. The idea that diversity could be explained by unconscious mechanisms, whose results were a reaction to and not in anticipation of changes in the environment, is quite remarkable given the entrenched views of the day. Scientific progress often challenges established orthodoxies, but the hand of God is about as big as they come.
Darwin’s theory of natural selection is, of course, not the end state of things. His gradualism has been supplemented by punctualism. Genetics has revealed much of the physical mechanism of natural selection which Darwin saw as the glaring hole in his theory. Evolutionary Developmental Biology (Evo Devo) has begun to take our understanding of evolution’s toolbox to new heights. Importantly, our extended Theory of Evolution still supports Darwin’s basic notion of what drives evolution and diversity.
Fodor seems to see Evo Devo as a challenge to natural selection. In fact, it is a very important extention of the “How” behind natural selection. The fact that it adds nuance to our understanding does not mean the basic premise is wrong.
Fodor makes much of his argument about pigs not having wings. Yet this is a flawed argument. He says: “To add wings to a pig, you’d also have to tinker with lots of other things. In fact, you’d have to rebuild the pig whole hog: less weight, appropriate musculature, an appropriate metabolism, an apparatus for navigating in three dimensions, a streamlined silhouette and god only knows what else; not to mention feathers. The moral is that if you want them to have wings, you will have to redesign pigs radically. But natural selection, since it is incremental and cumulative, can’t do that sort of thing.” This is simply wrong. Whales’ distant ancestors developed lungs and legs and emerged from the sea. Subsequent ancestors developed fins, and returned to the sea. They had to be rebuilt wholehog: more weight, more blubber, the ability to withstand great pressures in deep water, the ability to remain hydrated in salt water and to locate food in dark waters. It didn’t happen quickly, but it happened. This is just one of many such examples. The mechanisms of regulatory DNA that are being revealed by Evo Devo help explain just how such incredible transformations of form can occur.
Earlier in his essay Fodor says, “It’s true, of course, that breeding, like evolution, can alter phenotypes over time, with consequent effects on phylogenetic relations. But, on the face of it, the mechanisms by which breeding and evolution operate could hardly be more different. How could a studied decision to breed for one trait or another be ‘the very same thing’ as the adventitious culling of a population?” This point is also wrong. The mechanisms are precisely the same – genetic inheritance. Breeders are simply exploiting the mechanism by which natural selection occurs. Natural Selection is not a mechanism it is a process driven by a mechanism. Darwin recognized that the breeders were applying artificial conditions to select for traits, but this concept of artificial controls and the isolation of variables is the basis of the scientific method. In that sense, all experiments testing natural phenomena are simply analogies for the real thing.
Posted by: Chris Jones | Tuesday, April 29, 2008 at 01:14 AM
Even after a couple of readings, I am not sure I've gotten things straight, but it seems to me that you pretty much refute the main point in Fodor when you write that:
Fodor seems to have failed to note that in each of the three cases in question --the spandrels, the whiteness, and the floppiness--, at least three different kinds of coextensiveness seem to be in play. In the first, we are dealing with two traits that are non-identical but logically coextensive; in the second, with two traits that are in-this-world identical even if they support different counterfactuals; and in the third, with two non-identical and contingently linked traits. It could have been the case that the gene for floppy ears be located somewhere such that breeding for tameness would have yielded tame, pointy-eared foxes, but there is no possible scenario in which brown bears could have matched their snowy environment, even if counterfactually they could have had a non-snowy environment, and all this for reasons having nothing to do with genetics.
It cannot possibly be (because Fodor is a smart guy) that the problem is just that we describe the workings on nature through natural selection in intentional linguistic terms (used as metaphors) and are then puzzled that there is no agent there exercising the seeming agency that we have brought into being through our descriptions. (The sorts of confusions we have been very familar with since Dawkins was disastrously misunderstood to have attributed intentionality to genes.) But damn! I really can't see what else the problem is. The fact that we choose to describe organs, say, in language that drips with purposiveness, intentionality, and functionality, doesn't after all mean that these things couldn't in principle be described as a bunch of atoms alligned in such a way that other atoms in the vicinity tend to persist in a given configuration for longer periods of time in an environment of other atoms in the surroundings.
In other words, if all humans were to disappear from the Earth today and tomorrow my Timex was still ticking, it would clearly have no function (since there's no one who needs to know the time), but its movement could still be described physically, in addition to the historical narrative which explains it in human terms. And no, I am not espousing a scientistic realism in saying this. Even a holistic account is compatible with such a description.
Haven't we been through all this before? Didn't Dennett take care of much of this kind of stuff in The Intentional Stance and elsewhere? As the cliched example goes, even a thermostat is more felicitously described in intentional terms (but only as a metaphorical short form, and with the appropriate caveat). Why is the physical process of certain molecules developing according to known physical laws any different?
I have a bad feeling that I am not getting something very fundamental here, but damn if I know what Fodor is getting at. Further enlightenment from you will be appreciated.
Posted by: Abbas Raza | Tuesday, April 29, 2008 at 01:46 AM
Thanks for the thorough and penetrating comments. Sorry about the little "lupine" lapse. Somebody fix that!
I am travelling in deepest Transylvania right now, and will not be able to offer any replies until I am safely back in Germany next week.
Posted by: Justin Smith | Tuesday, April 29, 2008 at 05:07 AM
Have fixed "lupine." Chris, please forward your donation for copyediting directly to me. :-)
Posted by: Abbas Raza | Tuesday, April 29, 2008 at 05:19 AM
Great post. I think the real flaw in Fodor’s argument is his dismissal of the idea of the Universe having a knowable “mind” or selecting mechanism. He is forgetting Maxwell’s Demon and Information theory.
Maxwell’s Demon sits in a narrow tube connecting 2 chambers selects between 2 different types of molecule that pass by her, by closing the passage to molecules of type A and opening it for type B. This thought experiment was supposed to show that she could reduce the entropy in both chambers without spending energy, but in fact it turns out that the Demon would indeed need to expend energy (and so increase universal entropy) in order to identify each molecule as it past by her ( as well as to open and close the passage door (even if she got a male demon to do that for her, entropy would still be increased)) .
Thermodynamics predicts that things will evenly distribute themselves if no force is acting upon them (e g: gas molecules in a bottle). Any selection process requires energy to change that even distribution. As an example of a truly mindless selector mechanism, consider a rough mountain slope with large boulders and small pebbles rolling down it. The selection method here is the friction on the slope, which is proportionately greater for small pebbles, which therefore tend to stop rolling downhill, than it is for large boulders, whose greater momentum carries them all the way down to the bottom. Like with Maxwell’s Demon, energy must be spent to achieve this rough sorting according to size: the kinetic energy of the boulders and pebbles.
Once you have cleared up the mystery from a simple mechanical sorting/selection process, you have explained the “unknowable” ‘mind’ that Fodor brings up in his objection to the natural selection model. Animals’ sex/hunt/eat/flight decisions and the selections made by the human mind itself are all descended from and dependent upon simple physical processes like the slope and the rocks. All these processes consume energy to put things into some sort of order or combination, such as eggs + sperm, food in stomach, writing on page etc.
So Darwin is still OK.
Posted by: aguy109 | Tuesday, April 29, 2008 at 06:33 AM
As usual, an excellent essay by Justin Smith and an equally excellent comment by Chris Jones.
The most intriguing statement however is in the comment by Chris Schoen:
(not even survival, which is as transient as death.)
Death, transient? Wow. And hope springs eternal?
Posted by: Ruchira | Tuesday, April 29, 2008 at 11:00 AM
Ruchira, thanks for reading the fine print.
Death is not reversible, of course, but neither is it permanent. That's just to say that nothing stands still, that yesterday's corpse is today's breakfast.
Chris Jones,
You write that
But isn't it true that Adam Smith's work (in conjunction with Malthus) was a great influence on Darwin's thought? In other words, Darwin's leap wasn't to introduce the notion of an invisible hand, but rather to apply it to nature, rather than culture.
(Furthermore it might not even be a truism. Quoting Joseph Stiglitz: "the reason that the invisible hand often seems invisible is that it is often not there." )
You're correct to call remarkable, given the philosophical climate of Darwin's day, "the idea that diversity could be explained by unconscious mechanisms, whose results were a reaction to and not in anticipation of changes in the environment." But this is an idea which science has long since rejected. Life does not passively respond to changes in the environment; rather it interacts with it, doling out as many lumps (and as many caresses) as it takes.
Fodor seems to be merely asking just how much of Darwin we want to carry forward into the 21st century, much as we asked about Newton at the beginning of the last century.
Posted by: Chris Schoen | Tuesday, April 29, 2008 at 11:59 AM
It will probably take at least a week to digest the ideas you've brought up here, so I welcome the delay in response. But do get back to Germany safely Justin (hope you are not driving) and be on guard for that hypnotic adapter: Canis Nosferatus Lupus. I wouldn't put floppy ears past him.
Posted by: Jesse | Wednesday, April 30, 2008 at 03:39 AM
Chris Schoen,
You are correct that Adam Smith and Malthus clearly influenced Darwin's thinking. I would argue that Joseph Stiglitz's quote: "the reason that the invisible hand often seems invisible is that it is often not there," applies to economics precisely because there is conscious premeditation by monopolies, governments, manipulators, etc.
You are also correct that organisms influence their environment. Infact, any organism's environment is in part made up of the other organisms in it. I did not use the word passive in my argument. I used the word unconscious. My point being that there is no forethought or premeditation in evolution. Evolutionary change is generally a REACTION to changes in the environment which favor some traits over others in regard to reproductive fitness. Science has not rejected this idea.
Science has added to Darwin's original ideas. Natural Selection remains the dominant process of evolution, but other processes such as genetic drift do play supporting roles in evolution.
If Darwin were alive today, I think he would be excited by the nuance that has been added to his idea. Had he known about DNA, he might well have thought of some of these concepts himself.
Fodor goes much further than asking the question you attribute to him when you say, "Fodor seems to be merely asking just how much of Darwin we want to carry forward into the 21st century, much as we asked about Newton at the beginning of the last century." He suggests that Darwin is on the way out. He states, "Most immediately, it’s that the classical Darwinist account of evolution as primarily driven by natural selection is in trouble on both conceptual and empirical grounds." He then goes on to site Evolutionary Developmental Biology as supporting his claim. If anything, Evo-Devo provides new insight into how genetic heredity is a powerful enough mechanism to create the diversity and complexity that exists through the process of natural selection.
It would be silly to suggest that we have not advanced our understanding of evolution in all this time. But Darwin's work and ideas remain the very solid foundation upon which current gentecs, evo-devo and all modern biology stand.
Posted by: Chris Jones | Sunday, May 11, 2008 at 09:43 PM
Thanks again for all these comments. It's interesting to me that after presenting a version of this post as a colloquium paper here in Berlin, and after getting feedback here, in both cases my hearers and readers have focused on the least original part, namely, the explication of Fodor's argument, while remaining silent on the material on Darwin himself. It was this latter material that I myself took to be the paper's real contribution. What I wanted to show is that in the context in which Darwin was writing there was an important shift taking place away from mechanistic cosomogonical models, and that Darwin's own work represents a sort of culmination of this trend, in which the designer is not so much eliminated from explanations of design in nature as he or it is reconceived on the model of a different line of work: from the clockmaker of the 17th century, to the breeder of the 19th.
Abbas is certainly correct to say that Fodor's argument has to be more than just this: evolutionary explanation falls back on an uncashable metaphor, therefore it is bad. Fodor does think that there is something wrong with the metaphor not just qua metaphor but in view of the fact that we do not seem to have any idea of what it is that the metaphor is supposed to be standing in for. The core of his argument has to do with the impossibility of choosing the trait that was selected from among coextensive traits, such as being white and matching the environment. As some of my German colleagues pointed out, Fodor's unease here could easily be generalized into a much broader concern about the meaningfulness of causal explanations. Fodor has been known to express this unease, and it seems to me that as a philosopher he is right to do so. But causal explanations are in no danger of being purged from science --even if Bertrand Russell, and before him, in their own way, Malebranche, al-Ghazali, etc.-- thought that causality was on its way out of fashion. I can't think of any reason why his concern about coextensive traits and "the support of relevant counterfactuals" should have any more of an impact on science.
Posted by: Justin Smith | Monday, May 12, 2008 at 05:14 PM
Justin,
Thanks for your latest comments. I find Fodor's essay rather impenetrable, so your thoughts have been helpful. I came upon an online interview with Fodor's collaborator Massimo Piattelli-Palmarini at http://www.scoop.co.nz/stories/HL0805/S00106.htm I don't agree with many of his conclusions, but I find his discussion far more lucid and thought provoking.
In reading his arguments, I keep coming to the same conclusion: that he is confusing the process for the mechanism driving the process. Traits do not originate from natural selection, they originate from changes in genes or gene expression. Once they emerge, however, they are generally favored or not favored by natural selection in regard to reproductive fitness. With each incremental change new traits emerge through mutation, recombination etc. Over time these favored traits can diverge dramatically from the earlier sets of traits.
What is exciting about Evo Devo is that apparently it is far easier for new forms to emerge than was at first imagined. Again weather through mutation or recombination, minor changes in regulatory DNA (which acts like switches turning gene expression on and off) can have dramtic impacts on form. This makes the development of complex forms much easier to understand. Certainly, Darwin's tiny increments of change may often be larger than we previously thought. In this regard, there is no doubt that evo-devo has ushered in a revolutionary change in our understanding of the mechanisms driving evolution just like the works of Mendel and Watson and Crick did. But with each change in form, the pressure of natural selection will determine if that change thrives or diminishes. Genetics and Evo-Devo help explain the mechanisms behind the emergence of new traits. The process of natural selection largely determines which traits survive.
As to Fodor's concerns about demonstrating causality, this is always problematic in complex systems. I agree with your conclusions.
Posted by: Chris Jones | Tuesday, May 13, 2008 at 05:31 PM
Chris Jones,
It's true that you did not use the word "passive," but is passivity not implied in the following?
You write that "science has not rejected this idea" but I think it has just done so too quietly to hear. There is abundant literature on the active and inter-relational role of organisms in their environments. We may prefer to look at evolution as a passive phenomenon because doing so guards against animism, but it is no longer a defensible position.
On evo-devo, you write that it
and later that
These seem to me the wrong conclusions to draw from this field. The study of biological development emphasizes the inherent robustness of the organism in resiting influences from the environment (both internal and external). The principles involved are not well understood, but biologists dating back to the mid-20th century (e.g. Waddington and Weiss) have remarked extensively on organisms' ability to stay "on track" despite significant environmental disruptions and perturbations.
As Brian Goodwin and others have noted, genes alone cannot account for form. Evo devo at its most valuable and interesting is the study of nongenetic and epigenetic factors in the development of form. Fodor's language on this is odd (for example, he calls canalization "channeling") but I think this is the area of study he is trying to address.
Posted by: Chris Schoen | Thursday, May 15, 2008 at 05:48 PM
Chris Schoen,
In your last post you said, “There is abundant literature on the active and inter-relational role of organisms in their environments. We may prefer to look at evolution as a passive phenomenon because doing so guards against animism, but it is no longer a defensible position.” I agree there is ample literature about interactions of organisms, but the term environment can be defined as the sum of all external conditions and influences, including other organisms, that affect the development and survival of an organism or group of organisms. With regard to evolution being “passive”, I simply mean it lacks any sort of foresight. In other words, an organism doesn’t sit around thinking, “I should evolve an opposable thumb.” It also doesn’t consciously evolve a symbiotic relationship.
Later in challenging two of my statements: that evo-devo “provides new insight into how genetic heredity is a powerful enough mechanism to create the diversity and complexity that exists through the process of natural selection.” and that, “what is exciting about Evo Devo is that apparently it is far easier for new forms to emerge than was at first imagined,” you responded that, “The study of biological development emphasizes the inherent robustness of the organism in resisting influences from the environment (both internal and external). The principles involved are not well understood, but biologists dating back to the mid-20th century (e.g. Waddington and Weiss) have remarked extensively on organisms' ability to stay "on track" despite significant environmental disruptions and perturbations.”
Let me clarify my initial points before responding to your assertion. When I used the term “genetic heredity” in my first statement, I meant to include both genes and the regulatory “switches” which control their expression, although this was admittedly unclear. The point of my second statement was that it would seem a lot easier to develop diversity and complexity if, for example, you didn’t need to evolve a new gene for a new set of limbs, but instead needed only to reactivate existing switches for an existing gene’s expression. I know my example here may be a gross oversimplification reminiscent of “hopeful monsters,” but it helps to make a point.
I am not ignoring epigenic factors. They clearly play an important role in development, witness the differentiation of our own cells (eye, skin, nerve, etc) which all contain the same genes. These factors may also play a more important role in evolution than was previously expected, but this remains a relatively new area of exploration.
Recent studies in canalization are intriguing, but a lot of work needs to be done before we can know for sure what its evolutionary purpose and impact is. At least a few alternative hypotheses exist for the role of canalization. One can certainly imagine that organisms might evolve robust traits to mitigate the deleterious impact of harmful mutations. The buffer provided by a complex regulatory system to control gene expression, might be very favorable and thus selected for.
Let us suppose epigenic factors do play a major role in evolution. Does this mean that Natural Selection is on the way out? I don’t think so. Much to his own consternation, Darwin never knew about genetics or epigenics. Genetics and epigenic factors may both play an important role in the emergence of new traits. Natural Selection doesn’t create traits, it simply sorts out which traits (genetic or epigenic) will thrive.
If Fodor is suggesting that there needs to be a new “New Synthesis,” I would suggest it is already well underway even if it has not been named. But Fodor’s rhetoric suggests that he would like to reject natural selection altogether and that seems to be unsupported.
Posted by: Chris Jones | Tuesday, May 20, 2008 at 09:57 PM
I have come along late, and im probably talking to myself here, but I don't think that most people are understanding Fodor's argument. His point is that the "theory" of natural selection is not really a scientific theory in any legitimate sense- it doesn't do any real work. It is used to give a sheen of scientific respectibility to historical narratives that are, in essence, speculative.
Posted by: Ryan | Wednesday, November 25, 2009 at 05:44 AM