Published: 11/2007, with the Fodor’s article reprinted below.
Poor Fodor. He should have stuck to opera, a subject he seems to know something about. Instead of quoting from Die Meistersinger, it would have been more appropriate for him to have quoted from Matthew Arnold’s poem, “Dover Beach”:
For we are here as on a darkling plain
Swept with confused alarms of struggle and flight
Where ignorant armies clash by night.
Fodor is only the latest in rogues’ gallery of people with personal agendas of one kind or another who have used, or abused, Darwin’s theory – a practice that dates back to one of Darwin’s most vocal 19th Century champions, T.H. Huxley, whose interpretations of Darwin’s theory were seriously misleading. Darwin had the formidable challenge of trying to convey a very subtle idea to a largely ignorant and deeply prejudiced audience, and it seems that things haven’t changed very much since then.
Given the misunderstandings that are evident in Fodor’s essay (reprinted below), it’s worth re-stating Darwin’s basic idea. In a nutshell, he posited that the history of life on Earth has involved a very long, trans-generational process characterized by both continuities and “progressive” (and sometimes regressive) functional developments. Moreover, both the continuities and the changes that have occurred over time have been the ultimate result of a causal dynamic that is internal to the process itself. It was not imposed from outside.
In essence, this causal dynamic involves a process in which the outcomes (in terms of survival and reproduction) in each generation of living organisms are determined in situ by the functional relationships and interactions that occur between organisms and their specific environments. Both the organism and its environment are important players in this dynamic, and it is absolutely wrong to say that inanimate environments do any “selecting”. Even as a metaphor, this is misleading. Likewise, it is onerous to say that something is “selected for.” It implies premeditation.
Darwin characterized this dynamic as “natural selection,” but he well understood (despite his sometimes flagrant rhetoric – see the addenda below) that natural selection is not a “mechanism”, and it does not actually do anything. In fact, it is a metaphor based on an analogy with artificial selection by animal breeders. Nor did he claim that natural selection was the exclusive agency of evolutionary change; he was well aware of the complexities. And yes, it is an analogy, but it has withstood the test of time. Fodor is the one who is “misled”.
A crucial point about Darwin’s theory, which is often overlooked by his critics (Fodor is a case in point) is that it rests on the fundamental assumption that life is a contingent and often precarious process (a “struggle for existence” as Darwin put it) and that “earning a living” (and reproducing) in the “economy of nature” is the basic vocation for all life forms. In other words, in evolution there is no free lunch.
Given this premise, and given the well-documented fact that living systems can vary greatly in their functional capabilities – their ability to earn a living in a given environment – it follows that there will be differential success in surviving and reproducing. So natural selection refers to the survival/reproduction outcomes in each generation, including both the continuities and the changes — the weeding in as well as the weeding out. (I’m partial to Theodosius Dobzhansky’s distinction between “normalizing” or stabilizing selection, positive selection, and negative selection.) Darwin also adopted the Malthusian assumption of relentless population growth, which greatly intensifies competition for the means of susbsistence, but this assumption is not essential to the theory and is not always the case.
There’s much more that could be said, but it’s worth noting here that Darwin is not the last word on the subject, as some modern critics seem to think. Darwin had a peerless understanding of the natural science of his day, but we have learned vastly more about the evolutionary process (and natural selection) since then. Nevertheless, his core concept remains valid. To use an analogy, it’s rather like comparing Henry Ford’s Model-T to a modern automobile. There have been a great many refinements, but the basic principles remain the same.
Among the many problems with Fodor’s essay is the fact that he tacitly assumes away the basic survival problem – what I refer to as the “ground-zero premise” of evolutionary biology – and so do many theorists of the complexity school. Given the fact that life is preeminently a contingent “survival enterprise,” one cannot escape from the need for “adaptation” – the ongoing quest to satisfy an array of definable “basic needs.” (In the case of humankind, some 14 distinct basic needs “domains” have been identified.)1 Life is not always “nasty, brutish and short” (as Hobbes would have it), though the vast majority of the world’s teeming masses might think so, not to mention the hundreds of millions who have died prematurely in various wars and catastrophes during the past century alone. But nobody who is attuned to the history of life on Earth and the natural world can deny the primary importance of adaptation (more on this below). So happiness is hardly the be-all and end-all, as Fodor seems to imply. I’m reminded of the old saying: “What good is happiness, you can’t buy money with it.”
Another serious problem with Fodor’s essay is his assertion that we can’t get much help from science in terms of moral guidance. On the contrary, both the biological and social sciences have been making significant progress in recent years in elucidating how and why humans have moral values and, more important, what consequences they have for a species that depends on a highly organized, interdependent “collective survival enterprise.”
Actually, Darwin himself introduced the subject in The Descent of Man, and there have been many other writers on the subject ever since. (Herbert Spencer was one of the most important early theorists.) More recently, Elliott Sober and David Sloan Wilson’s important book, Unto Others, sheds much light on this matter, as does Wilson’s work on the evolution of religion, especially in his recent book, Darwin’s Cathedral. Primatologist Frans deWaal’s delightful book, Good Natured, is an example of empirical work on primate behaviors that illuminates the origins and functions of moral behaviors in humans as well. Even game theory has made significant contributions to this subject. In short, “evolutionary ethics” is a well-defined subject area these days. (I agree with Wilson’s view that the anti-religion diatribes of Dawkins, Dennett and Hitchens are travesties.)2
As for the “is-ought” (fact-value) dichotomy, I can only say for shame! I thought we had long since moved beyond this hoary 19th century conceit. At least in the sciences these days, it states the obvious. On the other hand, the “facts” can have important implications for values and goals that are preexisting (that are themselves a “fact”). And, post-modernists to the contrary notwithstanding, it is naïve (and a throwback to the Behaviorist tabula rasa era in psychology) to imply that we come into this world, after many millions of years of evolutionary rigor, without a well-defined repertoire of predispositions, desires and, yes, basic needs that may then be molded and shaped by our diverse (and sometimes perverse) cultures. And these culturally-imposed “oughts” can have profound consequences for our very survival and reproductive success. (The 19th Century Shaker cult, with its celibacy rule, provides one extreme example; the polygamous ways of the old-order Mormons provides another example – among many.)
Not spandrels again! To mix a metaphor, that’s a red herring. Fodor would have been better served had he read the flood of writings that followed the publication of that important article by Stephen Jay Gould and Richard Lewontin (“The Spandrels of San. Marco and the Panglossian Paradigm”), most especially Ernst Mayr’s definitive essay on adaptation. Of course there are spandrels in the living world – though they are relatively few because natural selection also involves a rigorous cost-benefit analysis, and costly frills (or non-functional traits) are generally weeded out.
It’s also worth noting that the spandrels metaphor is really not a proper analogy. It’s the arches that were subject to functional (adaptive) “selection” by Medieval engineers. How many churches fell down before these buttresses were perfected? The spandrels, on the other hand, were low cost decorative add-ons that in no way affected the functional properties of the arches. Anything that was harmful would have been selected against!
So what on earth is Fodor’s point here? That some people might get confused about what is functional and what is not? Hardly. That’s why the spandrels made such an effective talking point in the Gould/Lewontin piece. I’m reminded of John Maynard Smith’s durable discussion of adaptation in his classic text, The Theory of Evolution. Among other things, Maynard Smith pointed out that many examples of adaptation are common sensical, and it would be a bit foolish to subject them to testing – why horses have legs or teeth, for example. It’s only when there is some doubt – and a debate – that appropriate tests of alternative hypotheses are important. In this light, surely the spandrels can be excluded. (I’m also partial to George Williams’ example in his classic Adaptation and Natural Selection. When a flying fish leaps into the air, this is the result of a “design for survival.” When the fish falls back into the water, it is not.)
It’s very odd that the silver fox study should be cited as a model for natural selection (or the lack thereof), since it is in fact a premier example of artificial selection – a context in which the normal pressures and constraints associated with the survival enterprise are removed. You can be sure that in the wild there would never be inbreeding for tameness, with all of its curious side-effects. So what’s the point here? That there are often genetic linkages between traits? This has been known for a hundred years.
So what about Fodor’s core point that nonadaptive changes from various sources may also be important causes of evolutionary change. Well, of course. This has been part of the dialogue among evolutionists ever since the publication of D’Arcy Thompson’s great treatise On Growth and Form (1917). His work was further elaborated upon by C.H. Waddington and Bernard Rench in the 1950s, by Niles Eldredge and Stephen Jay Gould, Mae-Wan Ho and Peter T. Saunders, and Brian Goodwin (among others) in the 1970s and 1980s, and, more recently Stuart Kauffmann, John Holland, Stanley Salthe and his colleagues, and others of the dynamical systems, structuralist, evo-devo and complexity schools. Yes, causation in evolution is immensely complicated and variegated. (For an insightful perspective on this work, see Scott Camazine’s book, Self-Organization in Biological Systems.
Kauffman has been perhaps the most visible and vocal (and contentious) among the current generation of theorists in proclaiming that much of what we see in the evolutionary process may be characterized as “order for free” – biological organization that arose independently of natural selection. However, Kauffmann has since retreated from this salient, and for good reason. To repeat a key point that was made earlier, one cannot exclude any trait from being “tested” in relation to its consequences for survival and reproduction without tacitly denying that survival is a problem — that the outcome could go either way. A spandrel may be neutral in its effect on the survival and reproduction. Nevertheless, it is tested anew for its neutrality in every generation.
On “minding” the gap (as Londoners would say), I’ll confess that I have always found the hypothesized environment of evolutionary adaptation (EEA) to be a construct that is of limited use as a heuristic tool, and Fodor should not make too much of it – for several reasons. One is that the human “mind” (not to mention our social, emotional and even moral equipment) evolved over a very long period, perhaps five million years, in frequently and radically varying environments. So which one do you choose?
But more important, we are still evolving; our evolution didn’t stop 150,000 years ago. It seems Fodor is not aware of E.O. Wilson’s ten-generation rule – micro-evolution under circumstances in which there is a very strong selection coefficient. Or Ernst Mayr’s “founder principle,” which refers to the rapid evolutionary divergences that can occur in small, isolated populations. (Indeed, the evidence for Mayr’s principle is all around us in our own species, where significant micro-evolutionary differences have arisen in various parts of the world just within the past 10,000 years.) Nor, it seems, is Fodor aware of the important work in behavioral ecology, symbiogenesis theory, gene-culture coevolution theory, niche construction theory, and what I call Neo-Lamarkian theory (AKA the Baldwin Effect). In other words, organisms are not passive actors but are themselves agents of evolutionary innovation and change. Only now are living organisms themselves being given the credit they are due for the active role they have played in influencing the course of the evolutionary process. A bit of history might be in order here.
It was Lamarck who first postulated that changes in an animal’s “habits” might be the initiating cause of evolutionary change. Darwin didn’t disagree, though he suggested that it is often difficult to tell which happens first, a change in morphology or a change in behavior. Perhaps, he suggested, they are closely linked in a sequence of progressive directional changes. The idea lay fallow for several decades but was resurrected by the so-called Organic Selectionists at the turn of the 20th century, who posited that a change in behavior can alter an organism’s relationship to its environment and thus create a new “selective screen” for natural selection.
The idea was set aside once again during the heyday of population genetics, but it was tentatively reincarnated by George Gaylord Simpson in the 1950s under the term “Baldwin Effect” (so named for one of the prominent Organic Selectionists). Ernst Mayr picked up this theme in his landmark article on “The Emergence of Evolutionary Novelties,” where he flatly asserted that a change in behavior is one of the most important sources of evolutionary change. Again there was a hiatus, but in recent years we have seen a proliferation of writings, and research, on what psychologist Donald Campbell felicitously characterized as “downward causation” in evolution.3 Some of the important nodes in this area were cited above. To this listing I would add my own work on the causal role of synergistic effects of various kinds (including especially behavioral forms of cooperation) in evolution. Maynard Smith has dubbed it “synergistic selection.”4
However, none of this contradicts, subverts or weakens the role of natural selection in evolution. I like to characterize the overall process as an admixture of “chance, necessity, teleonomy, and selection” (an expansion on the Nobel Prize-winning geneticist Jacques Monod’s famous slogan), with “teleonomy” as a place-holder for the “internal” needs, goals and behavioral propensities of living organisms themselves.
So, let’s stop beating up on natural selection, even as we acknowledge the many causal influences – from genes to ecosystems — that have shaped the evolutionary process and determined the outcomes of the selection process. But to deny natural selection is to deny the ultimate fragility of the human condition and, indeed, of life on Earth.
One final observation about Fodor’s folly. If you want to diagnose the various forms of “madness” that are rampant in the world, you would do well to weigh very carefully the combined influence of nature and nurture, for the many degrees of freedom in our cultures, our economies, and our politics are at least as important as our biology – as many (most?) biologists these days would readily attest. (Indeed, even where “nature” is concerned, the influence of individual differences is still underrated.) It is not that our minds are ill-adapted to our cultures, as Fodor would have it, but the other way around. (Anthropologist Robert Edgerton’s classic, Sick Societies, provides a book-length treatment of this subject.)
Poor us. It seems we, and our social theorists, are congenitally unable to get beyond what Mayr called “one long argument” about evolution. The reasons are many, I think. To cite just a few: There is, first, the fact that we are often the victims of poor (and biased) scholarship. There ought to be a rule against writing about the subject without first “doing your homework” in a vast and often conflicted literature. Equally important is the deep “political” implications of evolution. We are all subject to the agendas of big egos and big institutions with big constituencies. And evolution via natural selection rivals many other claims to what is “the truth and the way.”
Another difficulty, already discussed, is the very subtlety of the idea. Evolution is a functionally-oriented historical process that is always context specific and does not in fact involve a discreet causal agent. The centrality of relationships and functional interactions in nature is difficult for many to grasp, including (in truth) some of the more mechanistically-inclined evolutionary biologists over the years, who have had various axes to grind. In the end, we can only hope that Darwin’s middle way, and reason, will prevail.
For an in-depth treatement of this subject, see the chapter on “Biological Adaptation in Human Societies: A ‘Basic Needs’ Approach,” in my most recent book Holistic Darwinism: Synergy, Cybernetics and the Bioeconomics of Evolution (University of Chicago Press, 2005). It’s a reprint of an article that first appeared in the peer-reviewed Journal of Bioeconomics.
Evolution and ethics is discussed at length in an article of mine by that title, which appeared in two parts in the Journal of Social and Evolutionary Systems (1996, 1997). It is reprinted in my most recent book, Holistic Darwinism. Another contribution to this effort is the article of mine which appeared in the journal Politics and the Life Sciences in 2003 under the title (with the editor’s prompting) of “Fair Shares: Beyond Capitalism and Socialism, Or the Biological Basis of Social Justice.” It is reprinted in Holistic Darwinism with the more modest title: “Fair Shares: A Biological Approach to Social Justice.”
One of the most compelling examples of downward causation and the pacemaker effect can be found in “Darwin’s finches” — some 14 species of closely related finches in the Galápagos Islands, first observed by Darwin, that diverged from a common ancestor which, most likely, migrated into the islands in recent times from the mainland of South America. In a long-running research program conducted by zoologist Peter Grant and his wife and various associates, micro-evolution has been observed repeatedly in these species, especially in beak sizes and shapes, in response to climate fluctuations. For instance, during drought periods, larger birds with bigger, stronger beaks are able to survive better because they can eat the large, tough seeds that are relatively more abundant.
These and many other matters are covered extensively in my two most recent books: Nature’s Magic: Synergy in Evolution and the Fate of Humankind (Cambridge University Press, 2003) and Holistic Darwinism: Synergy, Cybernetics and the Bioeconomics of Evolution (University of Chicago Press, 2005). Also relevant is my just published article, in the Journal of Bioeconomics, entitled “Synergy Goes to War: A Bioeconomic Theory of Collective Violence.”
a.. Fodor also got Dobzhansky’s famous quote wrong. Dobzhansky wrote: “Nothing in biology makes sense except in the light of evolution.” He emphatically didn’t say “in the light of natural selection” This amounts to a serious misrepresentation.
a.. Darwin’s critics often cite his most flagrant bit of anthropomorphism in The Origin of Species as evidence for a mechanistic view of natural selection. In his peroration, he wrote: “It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working. Despite his vivid rhetoric, however, he did not literally believe in a selecting agent. Actually, in a later edition, Darwin inserted the qualifier: “It may metaphorically be said.”
a.. I’m uncomfortable with hearing talk about there being evolutionary “attractors” out there in nature, as if there is some invisible force at work (which only our dynamical systems equations can illuminate). Better said, nature is full of round holes, and square holes and holes of many other shapes that are available for round pegs, square pegs, etc., to occupy if they should happen to find them. (They are commonly referred to as “niches”.) — London Review of Books 29(20):19-22, 18 October 2007
Why Pigs Don’t Have Wings by Jerry Fodor
Die Meistersinger is, by Wagner’s standards, quite a cheerful opera. The action turns on comedy’s staple, the marriage plot: get the hero and the heroine safely and truly wed with at least a presumption of happiness ever after. There are cross-currents and undercurrents that make Meistersinger’s libretto subtle in ways that the librettos of operas usually aren’t. But for once Nietzsche is nowhere in sight and nobody dies; the territory is closer to The Barber of Seville than to The Ring. Yet, in the first scene of Act 3, the avuncular Hans Sachs, whose benevolent interventions smooth the lovers’ course, delivers an aria of bitter reflection on the human condition. It comes as rather a shock:
Wherever I look . . . .
People torment and flay each other
In useless, foolish anger
Till they draw blood.
Driven to flight,
They think they are hunting.
They don’t hear their own cry of pain . . . .
When he digs into his own flesh,
Each thinks he is giving himself pleasure.
So ‘what got into Sachs?’ is a well-known crux for Wagner fans, and one the opera doesn’t resolve. (By Scene 2 of Act 3 Sachs is back on the job, arranging for Walther to get his Eva and vice versa.) Sachs isn’t, of course, the first to wonder why we are so prone to making ourselves miserable, and the question continues to be pertinent. We have just seen the last of a terrible century with, quite possibly, worse to come. Why is it so hard for us to be good? Why is it so hard for us to be happy?
One thing, at least, has been pretty widely agreed: we can’t expect much help from science. Science is about facts, not norms; it might tell us how we are, but it couldn’t tell us what is wrong with how we are. There couldn’t be a science of the human condition. Thus the received view ever since Hume taught that ought doesn’t come from is. Of late, however, this Humean axiom has come under attack, and a new consensus appears to be emerging: Sachs was right to be worried; we are all a little crazy, and for reasons that Darwin’s theory of evolution is alleged to reveal. What’s wrong with us is that the kind of mind we have wasn’t evolved to cope with the kind of world that we live in. Our kind of mind was selected to solve the sorts of problems that confronted our hunter-gatherer forebears thirty thousand years or so ago; problems that arise for small populations trying to make a living and to reproduce in an ecology of scarce resources. But, arguably, that kind of mind doesn’t work very well in third millennium Lower Manhattan, where there’s population to spare and a Starbucks on every block, but survival depends on dodging the traffic, finding a reliable investment broker and not having more children than you can afford to send to university. It’s not that our problems are harder than our ancestors’ were; by what measure, after all? It’s rather that the mental equipment we’ve inherited from them isn’t appropriate to what we’re trying to do with it. No wonder it’s driving us nuts.
This picture ‘Äì that our minds were formed by processes of evolutionary adaptation, and that the environment they are adapted to isn’t the one that we now inhabit ‘Äì has had, of late, an extraordinarily favourable press. Darwinism has always been good copy because it has seemed closer to our core than most other branches of science: botany, say, or astronomy or hydrodynamics. But if this new line of thought is anywhere near right, it is closer than we had realised. What used to rile Darwin’s critics most was his account of the phylogeny of our species. They didn’t like our being just one branch among many in the evolutionary tree; and they liked still less having baboons among their family relations. The story of the consequent fracas is legendary, but that argument is over now. Except, perhaps, in remote backwaters of the American Midwest, the Darwinian account of our species’ history is common ground in all civilised discussions, and so it should be. The evidence really is overwhelming.
But Darwin’s theory of evolution has two parts. One is its familiar historical account of our phylogeny; the other is the theory of natural selection, which purports to characterise the mechanism not just of the formation of species, but of all evolutionary changes in the innate properties of organisms. According to selection theory, a creature’s ‘phenotype’ ‘Äì the inventory of its heritable traits, including, notably, its heritable mental traits ‘Äì is an adaptation to the demands of its ecological situation. Adaptation is a name for the process by which environmental variables select among the creatures in a population the ones whose heritable properties are most fit for survival and reproduction. So environmental selection for fitness is (perhaps plus or minus a bit) the process par excellence that prunes the evolutionary tree.
More often than not, both halves of the Darwinian synthesis are uttered in the same breath; but it’s important to see that the phylogeny could be true even if the adaptationism isn’t. In principle at least, it could turn out that there are indeed baboons in our family tree, but that natural selection isn’t how they got there. It’s the adaptationism rather than the phylogeny that the Darwinist account of what ails us depends on. Our problem is said to be that the kind of mind we have is an anachronism; it was selected for by an ecology that no longer exists. Accordingly, if the theory of natural selection turned out not to be true, that would cut the ground from under the Darwinist diagnosis of our malaise. If phenotypes aren’t selected at all, then there is, in particular, nothing that they are selected for. That applies to psychological phenotypes inter alia.
In fact, an appreciable number of perfectly reasonable biologists are coming to think that the theory of natural selection can no longer be taken for granted. This is, so far, mostly straws in the wind; but it’s not out of the question that a scientific revolution ‘Äì no less than a major revision of evolutionary theory ‘Äì is in the offing. Unlike the story about our minds being anachronistic adaptations, this new twist doesn’t seem to have been widely noticed outside professional circles. The ironic upshot is that at a time when the theory of natural selection has become an article of pop culture, it is faced with what may be the most serious challenge it has had so far. Darwinists have been known to say that adaptationism is the best idea that anybody has ever had. It would be a good joke if the best idea that anybody has ever had turned out not to be true. A lot of the history of science consists of the world playing that sort of joke on our most cherished theories.
Two kinds of consideration now threaten to displace natural selection from its position at the centre of evolutionary theory; one is more or less conceptual, the other is more or less empirical.
The conceptual issue. There is, arguably, an equivocation at the heart of selection theory; and slippage along the consequent faultline threatens to bring down the whole structure. Here’s the problem: you can read adaptationism as saying that environments select creatures for their fitness; or you can read it as saying that environments select traits for their fitness. It looks like the theory must be read both ways if it’s to do the work that it’s intended to: on the one hand, forces of selection must act on individual creatures since it is individual creatures that live, struggle, reproduce and die. On the other hand, forces of selection must act on traits since it is phenotypes ‘Äì bundles of heritable traits ‘Äì whose evolution selection theory purports to explain. It isn’t obvious, however, that the theory of selection can sustain both readings at once. Perhaps the consensus view among Darwinists is that phenotypes evolve because fit individuals are selected for the traits that make them fit. This way of putting it avoids the ambiguity, but whether it’s viable depends on whether adaptationism is able to provide the required notion of ‘selection for’; and it seems, on reflection, that maybe it can’t. Hence the current perplexity.
History might reasonably credit Stephen J. Gould and Richard Lewontin as the first to notice that something may be seriously wrong in this part of the wood. Their 1979 paper, ‘The Spandrels of S. Marco and The Panglossian Paradigm: A Critique of the Adaptationist Programme’, ignited an argument about the foundations of selection theory that still shows no signs of quieting. A spandrel is one of those more-or-less triangular spaces that you find at the junctures of the arches that hold up a dome. They are often highly decorated; painters competed in devising designs to fit them. Indeed (and this is Gould and Lewontin’s main point), casual inspection might suggest that the spandrels are there because they provide the opportunity for decoration; that, an adaptationist might say, is what spandrels were selected for. But actually, according to Gould and Lewontin, that gets things backwards. In fact, spandrels are a by-product of an arch-and-dome architecture; decide on the latter and you get the former for better or worse. Arches were selected for holding up domes; spandrels just came along for the ride.
I assume that Gould and Lewontin got their architectural history right, but it doesn’t really matter for the purposes at hand. What matters is that though spandrels survived and flourished, nothing at all follows about what, if anything, they were selected for. To a first approximation, you have spandrels if and only if you have a dome that’s supported by arches; the two are, as logicians say, coextensive. Is it, then, that selection for arches explains why there are spandrels? Or is it that selection for spandrels explains why there are arches? It looks, so far, as though the story could go either way; so what tips the balance? Surely it’s that domes and arches are designed objects. Somebody actually thought about, and decided on, the architecture of San Marco; and what he had in mind when he did so was that the arches should support the dome, not that they should form spandrels at their junctures. So that settles it: the spandrels weren’t selected for anything at all; they’re just part of the package. The question, however, is whether the same sort of reasoning can apply to the natural selection of the phenotypic traits of organisms, where there is, by assumption, no architect to do the deciding. If cathedrals weren’t designed but grew in the wild, would the right evolutionary story be that they have arches because they were selected for having spandrels? Or would it be that they have spandrels because they were selected for having arches? Or neither? Or both?
It’s a commonplace that Darwin constructed the theory of natural selection with an eye to what breeders do when they choose which creatures to encourage to reproduce. This reading of Darwin is by no means idiosyncratic. Darwin ‘argues by example, not analogy,’ Adam Gopnik wrote in the New Yorker in October last year. ‘The point of the opening of “The Origin” isn’t that something similar happens with domesticated breeds and natural species; the point is that the very same thing happens, albeit unplanned and over a much longer period.’ 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? Gopnik doesn’t say.
The 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.
The answers that have been suggested so far have not been convincing. In particular, though there is no end of it in popular accounts of adaptationism, it is a Very Bad Idea to try and save the bacon by indulging in metaphorical anthropomorphisms. It couldn’t, for example, be literally true that the traits selected for are the ones Mother Nature has in mind when she does the selecting; nor can it be literally true that they are the traits one’s selfish genes have in mind when they undertake to reproduce themselves. There is, after all, no Mother Nature, and genes don’t have, or lack, personality defects. Metaphors are fine things; science probably couldn’t be done without them. But they are supposed to be the sort of things that can, in a pinch, be cashed. Lacking a serious and literal construal of ‘selection for’, adaptationism founders on this methodological truism.
There are delicious ironies here. 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 empirical issue. It wouldn’t be unreasonable for a biologist of the Darwinist persuasion to argue like this: ‘Bother conceptual issues and bother those who raise them. We can’t do without biology and biology can’t do without Darwinism. So Darwinism must be true.’ Darwinists do often argue this way; and the fear of hyperbole seems not to inhibit them. The biologist Theodosius Dobzhansky said that nothing in biology makes sense without Darwinism, and he is widely paraphrased. The philosopher Daniel Dennett says that ‘in a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning and purpose with the realm of space and time, cause and effect, mechanism and physical law.’ (Phew!) Richard Dawkins says, ‘If superior creatures from space ever visit earth, the first question they will ask, in order to assess the level of our civilisation, is: “Have they discovered evolution yet?”‘ Shake a stick at a Darwinist treatise and you’re sure to find, usually in the first chapter, claims for the indispensability of adaptationism. Well, if adaptationism really is the only game in town, if the rest of biology really does presuppose it, we had better cleave to it warts and all. What is indispensable therefore cannot be dispensed with, as Wittgenstein might have said. The breaking news, however, is that serious alternatives to adaptationism have begun to emerge; ones that preserve the essential claim that phenotypes evolve, but depart to one degree or other from Darwin’s theory that natural selection is the mechanism by which they do. There is now far more of this sort of thing around than I am able to survey. But an example or two may give the feel of it.
Adaptationism is a species of what one might call ‘environmentalism’ in biology. (It’s not, by any means, the only species; Skinnerian learning theory is another prime example.) The basic idea is that where you find phenotypic structure, you can generally find corresponding structure in the environment that caused it. Phylogeny tells us that phenotypes don’t occur at random; they form a more or less orderly taxonomic tree. Very well then, there must be nonrandomness in the environmental variables by which the taxonomic tree is shaped. Dennett has put this idea very nicely: ‘Functioning structure carries implicit information about the environment in which its function “works”. The wings of a seagull . . . imply that the creature whose wings they are is excellently adapted for flight in a medium having the specific density and viscosity of the atmosphere within a thousand metres or so of the surface of the Earth.’ So, phenotypes carry information about the environment in which they evolved in something like the way that the size, shape, whatever, of a crater carries information about the size, shape, whatever, of the meteor that made it. Phenotypes aren’t, in short, random collections of traits, and nonrandomness doesn’t occur at random; the more nonrandomness there is, the less likely it is to have been brought about by chance. That’s a tautology. So, if the nonrandomness of phenotypes isn’t a reflection of the orderliness of God’s mind, perhaps it is a reflection of the orderliness of the environments in which the phenotypes evolved. That’s the theory of natural selection in a nutshell.
But as soon as it’s put that way, it’s seen not to be the only possibility. External environments are structured in all sorts of ways, but so, too, are the insides of the creatures that inhabit them. So, in principle at least, there’s an alternative to Darwin’s idea that phenotypes ‘carry implicit information about’ the environments in which they evolve: namely, that they carry implicit information about the endogenous structure of the creatures whose phenotypes they are. This idea currently goes by the unfortunate soubriquet ‘Evo-Devo’ (short for ‘evolutionary-developmental theory’). Everybody thinks evo-devo must be at least part of the truth, since nobody thinks that phenotypes are shaped directly by environmental variables. Even the hardest core Darwinists agree that environmental effects on a creature’s phenotype are mediated by their effects on the creature’s genes: its ‘genome’. Indeed, in the typical case, the environment selects a phenotype by selecting a genome that the phenotype expresses. Once in place, this sort of reasoning spreads to other endogenous factors. Phenotypic structure carries information about genetic structure. And genotypic structure carries information about the biochemistry of genes. And the biochemical structure of genes carries information about their physical structure. And so on down to quantum mechanics for all I know. It is, in short, an entirely empirical question to what extent exogenous variables are what shape phenotypes; and it’s entirely possible that adaptationism is the wrong answer.
One can think of the Darwinian account of evolution as prompted by the question: why are some phenotypes more similar than others? Darwin’sanswer was that phenotypic similarity is, pretty generally, explained by common ancestry; and the more similar two creature’s phenotypes, the less remote is the nearest ancestor that they share. There are isolated examples to the contrary, but there’s no serious doubt that this account is basically correct. And, if it’s not the best idea anybody ever had, it’s pretty good by any of the local standards. When you ask Darwin’s question ‘Äì why are phenotypes often similar? ‘Äì you do indeed get Darwin’s answer. But if you ask instead why it is that some phenotypes don’t occur, an adaptationist explanation often sounds somewhere between implausible and preposterous. For example, nobody, not even the most ravening of adaptationists, would seek to explain the absence of winged pigs by claiming that, though there used to be some, the wings proved to be a liability so nature selected against them. Nobody expects to find fossils of a species of winged pig that has now gone extinct. Rather, pigs lack wings because there’s no place on pigs to put them. 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. Evolution by natural selection is inherently a conservative process, and once you’re well along the evolutionary route to being a pig, your further options are considerably constrained; you can’t, for example, go back and retrofit feathers.
That all seems reasonable on the face of it; but notice that this sort of ‘channelling’ imposes kinds of constraint on what phenotypes can evolve that aren’t explained by natural selection. Winged pigs were never on the cards, so nature never had to select against them. How many such cases are there? How often does a phenotype carry information not about a creature’s environment but about aspects of its endogenous structure? Nobody knows.
But it bears emphasis that, on this way of thinking about evolution, the mechanisms by which phenotypes are constructed may very well be numerous and heterogeneous. This is one of the important ways in which evo-devo differs from adaptationism. Darwinists generally hold that natural selection, even if it isn’t all there is to evolution, is vastly the most important part. By contrast, channelling couldn’t conceivably explain the structure of phenotypes all by itself. But that leaves it open that channelling might be one among many mechanisms by which phenotypes express endogenous structure, and which, taken together, account for (some? many? all of?) the facts of evolution. If, as I suggested, the notion of natural selection is conceptually flawed, such alternatives would be distinctly welcome.
Here’s another kind of process that appears to explain some (very striking) facts about phenotype formation, but is quite different from either adaptation or channelling. In fact, it takes us back to spandrels. Gould and Lewontin say that spandrels are an artefact of selection for arches. Lacking arches, domes fall down; so arches are selected for supporting domes. But arches are linked to spandrels for reasons of geometry; so spandrels aren’t selected for, they are ‘free riders’ on selection for arches. The moral is that phenotypic traits can carry information about linkages among the mechanisms that produce them. Free-riding is always suggestive of such linkages, and free-riding is ubiquitous in evolution.
There’s a really lovely experiment that provides an example. The working hypothesis was succinctly summarised by Lyudmila Trut in American Scientist in 1999: ‘Because behaviour is rooted in biology, selecting for tameness and against aggression means selecting for physiological changes in the systems that govern the body’s hormones and neurochemicals. Those changes, in turn, could have had far-reaching effects on the development of the animals themselves, effects that might well explain why different animals would respond in similar ways when subjected to the same kinds of selective pressures.’ In the vocabulary I’ve been using: one might expect a galaxy of other phenotypic traits to be endogenously linked to tameness, and hence to free-ride on selection for it. Such properties would co-evolve with tameness even if they have little or no systematic effect on fitness; in effect there would be evolution without adaptation. Moreover, insofar as the genetic and physiological mechanisms that link tameness to its free-riders hold across a range of species, one might expect that selecting for tameness will have similar phenotypic by-products in creatures of quite different kinds.
The experimental investigation of these hypotheses involved forty years of inbreeding for tameness in thirty or so generations of silver foxes. The results are impressive. On the one hand, foxes that were bred for tameness also tended to share a number of other phenotypic traits. Unlike their feral cousins, they tend to evolve floppy ears, brown moulting, grey hairs, short curly tails, short legs and piebald coloration (in particular, white flashes). Inbreeding for tameness also had characteristic effects on the reproductive cycles of the foxes and on the average size of their litters. And these are all traits that other domestic animals (dogs, cats, goats, cows) also tend to have. An adaptationist might well wonder what it is about dogs, cats etc that makes curly tails good for their fitness in an ecology of domestication. The answer, apparently, is ‘nothing’. Curly tails aren’t fitness enhancing, they just happen to be linked to tameness, so selection for the second willy-nilly selects the first.
This case is much like that of spandrels, but much worse from an adaptationist’s point of view. You can explain the linkage between domes, arches and spandrels; the geometry and mechanics of the situation demands it. But the ancillary phenotypic effects of selection for tameness seem to be perfectly arbitrary. In particular, they apparently aren’t adaptations; there isn’t any teleological explanation ‘Äì any explanation in terms of fitness ‘Äì as to why domesticated animals tend to have floppy ears. They just do. It’s possible, of course, that channelling and free-riding are just flukes and that most or all of the other evolutionary determinants of phenotypic structure are exogenous. It’s also possible that palaeontologists will someday dig up fossilised pigs with wings. But don’t bet on it.
So what’s the moral of all this? 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. Darwin was too much an environmentalist. He seems to have been seduced by an analogy to selective breeding, with natural selection operating in place of the breeder. But this analogy is patently flawed; selective breeding is performed only by creatures with minds, and natural selection doesn’t have one of those. The alternative possibility to Darwin’s is that the direction of phenotypic change is very largely determined by endogenous variables. The current literature suggests that alterations in the timing of genetically controlled developmental processes is often the endogenous variable of choice; hence the ‘devo’ in ‘evo-devo’.
But I think there’s also a moral about what attitude we should take towards our science. The years after Darwin witnessed a remarkable proliferation of other theories, each seeking to co-opt natural selection for purposes of its own. Evolutionary psychology is currently the salient instance, but examples have been legion. They’re to be found in more or less all of the behavioural sciences, to say nothing of epistemology, semantics, theology, the philosophy of history, ethics, sociology, political theory, eugenics and even aesthetics. What they have in common is that they attempt to explain why we are so-and-so by reference to what being so-and-so buys for us, or what it would have bought for our ancestors. ‘We like telling stories because telling stories exercises the imagination and an imagination would have been a good thing for a hunter-gatherer to have.’ ‘We don’t approve of eating grandmother because having her around to baby-sit was useful in the hunter-gatherer ecology.’ ‘We like music because singing together strengthened the bond between the hunters and the gatherers (and/or between the hunter-gatherer grownups and their hunter-gatherer offspring)’. ‘We talk by making noises and not by waving our hands; that’s because hunter-gatherers lived in the savannah and would have had trouble seeing one another in the tall grass.’ ‘We like to gossip because knowing who has been up to what is important when fitness depends on co-operation in small communities.’ ‘We don’t all talk the same language because that would make us more likely to interbreed with foreigners (which would be bad because it would weaken the ties of hunter-gatherer communities).’ ‘We don’t copulate with our siblings because that would decrease the likelihood of interbreeding with foreigners (which would be bad because, all else being equal, heterogeneity is good for the gene pool).’ I’m not making this up, by the way. Versions of each of these theories can actually be found in the adaptationist literature. But, in point of logic, this sort of explanation has to stop somewhere. Not all of our traits can be explained instrumentally; there must be some that we have simply because that’s the sort of creature we are. And perhaps it’s unnecessary to remark that such explanations are inherently post hoc (Gould called them ‘just so stories’); or that, except for the prestige they borrow from the theory of natural selection, there isn’t much reason to believe that any of them is true.
The high tide of adaptationism floated a motley navy, but it may now be on the ebb. If it does turn out that natural selection isn’t what drives evolution, a lot of loose speculations will be stranded high, dry and looking a little foolish. Induction over the history of science suggests that the best theories we have today will prove more or less untrue at the latest by tomorrow afternoon. In science, as elsewhere, ‘hedge your bets’ is generally good advice.
As for Sachs, I wouldn’t think of arguing that we are either mostly happy or mostly good. But I doubt that’s because of what our minds were selected for. Maybe the real trouble is that our neurones aren’t hooked together quite right, or that some of our hormones aren’t entirely reliable; with the effect, in either case, that getting some of the things we want isn’t compatible with getting the others. Or that some of them we can’t have at all. Anyhow, for what it’s worth, I really would be surprised to find out that I was meant to be a hunter-gatherer since I don’t feel the slightest nostalgia for that sort of life. I loathe the very idea of hunting, and I’m not all that keen on gathering either. Nor can I believe that living like a hunter-gatherer would make me happier or better. In fact, it sounds to me like absolute hell. No opera. And no plumbing.
Jerry Fodor is collaborating with Massimo Piattelli-Palamarini on a book about evolution without adaptation.