The Improbability Pump

The Improbability Pump

Why has natural selection always been the most contested part of evolutionary theory?


Imagine for a moment that a large proportion of Americans–let’s say half–rejected the "germ theory" of infectious disease. Maladies like swine flu, malaria and AIDS aren’t caused by micro-organisms, they claim, but by the displeasure of gods, whom they propitiate by praying, consulting shamans and sacrificing goats. Now, you’d surely find this a national disgrace, for those people would be utterly, unequivocally wrong. Although it’s called germ theory, the idea that infections are spread by small creatures is also a fact, supported by mountains of evidence. You don’t get malaria unless you carry a specific protozoan parasite. We know how it causes the disease, and we see that when you kill it with drugs, the disease goes away. How, we’d ask, could people ignore all this evidence in favor of baseless superstition?

But that’s fiction, right? Well, not entirely, for it applies precisely to another "theory" that is also a fact: the theory of evolution. Over the past quarter-century, poll after poll has revealed that nearly half of all Americans flatly reject evolution, many clinging to the ancient superstition that the earth was created only 6,000 years ago, complete with all existing species. But as Richard Dawkins shows in his splendid new book, The Greatest Show on Earth, the theory of evolution is supported by at least as much evidence as is the germ theory of disease–heaps of it, and from many areas of biology. So why is it contemptible to reject germ theory but socially acceptable to reject evolutionary theory?

One answer is religion. Unlike germ theory, the idea of evolution strikes at the heart of human ego, suggesting that we were not the special object of God’s attention but were made by the same blind and mindless process of natural selection that also built ferns, fish and rabbits. Another answer is ignorance: most Americans are simply unaware of the multifarious evidence that makes evolution more than "just a theory," and don’t even realize that a scientific theory is far more than idle speculation.

While Dawkins has produced several brilliant books on the marvels of evolution and natural selection, he’s never before written at length about the evidence for evolution. The Greatest Show on Earth can be seen as his response to ongoing and nonscientific opposition to evolution. In his previous book, The God Delusion, Dawkins mounted a withering attack on belief that was surely motivated in part by his incessant battles with faith-based creationism. In The Greatest Show on Earth he finally addresses the problem of ignorance, drawing together the diverse evidence for evolution to show that "evolution is a fact. Beyond reasonable doubt, beyond serious doubt, beyond sane, informed, intelligent doubt, beyond doubt evolution is a fact." Dawkins has two goals here. The first is to change the minds of those who doubt or deny evolution by presenting them with more than 400 pages of scientific evidence. But changing minds is a big job, at least in the United States: in a 2006 Time magazine poll, 64 percent of Americans declared that if science disproved one of their religious beliefs, they’d reject the science in favor of their faith. (The British aren’t quite so defiant: one week after its publication, The Greatest Show on Earth debuted at No. 1 on the Sunday Times bestseller list.) More realistically, Dawkins hopes to bolster those who already accept evolution but "find themselves inadequately prepared to argue the case." And here he succeeds brilliantly.

In contrast, Jerry Fodor and Massimo Piattelli-Palmarini (hereafter "F&P") think the case should be dismissed. In their provocatively titled What Darwin Got Wrong they contend that ever since the 1859 publication of On the Origin of Species, scientists and laymen alike have been bamboozled by Darwin’s key idea: natural selection, which F&P see as logically incoherent and lacking in empirical support. Since the authors are neither creationists nor crackpots–Fodor, a respected philosopher of mind, and Piattelli-Palmarini, a cognitive scientist, both accept the fact of evolution–their arguments deserve careful scrutiny. Unfortunately, in the end their critique proves as biologically uninformed as it is strident, and despite their repeated avowals that Darwinism is dead, it refuses to lie down.

Demonstrating the truth of natural selection is just one of Dawkins’s aims, for the theory of evolution is composed of several more or less independent parts, which I like to describe in one longish sentence: "Life on earth evolved gradually, beginning with one primitive species; it then branched out over time, throwing off many new and diverse species–and the process producing the illusion of design in organisms is natural selection." This sentence constitutes a scientific theory, which is not just a guess but an informed statement about the general principles that explain many observations about nature.

Establishing that all these principles are true is a tall order, clearly demanding lots of evidence. And for most people, the evidence boils down to one thing: fossils. Although Darwin was faced with a scant fossil record (it played almost no role in his Origin of Species), since 1859 paleontologists have unearthed a wealth of fossils demonstrating not only gradual change of species over time but also the branching of lineages and the so-called "missing links" that connect major groups of animals. We see marine plankton, whose fossil record is superb, changing slowly and gradually, and early horses branching off into numerous descendants (only a few of which survive today). We have transitional fossils between fish and amphibians, mammals and reptiles, whales and their deerlike ancestors, birds and feathered dinosaurs, and, of course, fossils that link Homo sapiens to our cranially challenged ancestors. Evolution, you might say, is written in the rocks.

But as Dawkins points out, "we don’t need fossils in order to demonstrate that evolution is a fact. The evidence for evolution would be entirely secure, even if not a single corpse had ever fossilized." What is this other evidence?


One type lies within the bodies of living organisms. In a wonderful chapter called "History Written All Over Us," Dawkins shows that animal anatomy is like a medieval palimpsest, carrying traces of our evolutionary ancestry. Human goose bumps, for instance, serve no function: they’re remnants of the muscles used by our mammalian ancestors–and our living relatives like cats–to erect their fur, making them warmer and giving enemies the illusion of greater size. Modern genome sequencing has also uncovered vestigial DNA: useless, broken genes that are functional in our relatives and presumably were too in our ancestors. Our own genome, for instance, harbors nonfunctional genes that, in our bird and reptile relatives, produce egg yolk. Embryology–the study of development–brings more proof to the table. The pharyngeal arches of the early, fishlike human embryo are derived directly from the gill arches of fish, though they go on to become, among other things, our larynx and eustachian tube.

Even more evidence for evolution comes from the "bad designs" of animals and plants, which, Dawkins observes, look nothing like de novo creations of an efficient celestial engineer. His favorite example–and mine–is the recurrent laryngeal nerve, which runs from the brain to the larynx. In mammals it doesn’t take the direct route (a matter of a few inches) but makes a curiously long detour, running from the head to the heart, looping around the aorta and then doubling back up to the neck. In the giraffe, this detour involves traversing that enormous neck twice–adding about fifteen feet of superfluous nerve. Anyone who’s dissected an animal in biology class will surely agree with Dawkins’s conclusion: "the overwhelming impression you get from surveying any part of the innards of a large animal is that it is a mess! Not only would a designer never have made a mistake like that nervous detour; a decent designer would never have perpetuated anything of the shambles that is the criss-crossing maze of arteries, veins, nerves, intestines, wads of fat and muscle, mesenteries and more."

Creationists often object to this sort of argument, saying that it’s not scientific but theological. God is inscrutable, they claim, so how could we possibly know how he would or would not design creatures? But this misses the point, for the "bad design" we see is precisely what we’d expect if evolution were true. The laryngeal nerve takes that long detour because, in our fishy ancestors, it was lined up behind a blood vessel, with both nerve and vessel servicing the gills. As the artery moved backward during its evolution to the mammalian aorta, the nerve was constrained to move behind it, although its target (the larynx, an evolutionary descendant of the gill arch) remained up in the neck. If you insist that such designs reflect God’s plan, then you must admit that his plan was to make things look as if they had evolved.

Finally, Dawkins provides evidence from a completely different realm: that of biogeography, the study of how plants and animals are distributed over the earth. Why do volcanic islands like Hawaii have plenty of unique plants, birds and insects (most resembling species from the nearest mainland) but no native amphibians, freshwater fish or land mammals? Such patterns defy explanation by any form of creationism. Instead, they bespeak long-distance migration of ancestors to newly formed islands, followed by the evolution of new species.

Fossils, embryology, bad design, molecular biology, vestigial traits, biogeography–all conspire to demonstrate the truth of evolution. All are described in Dawkins’s famously lyrical prose and lavishly illustrated with color photos. Two chapters stand out. One, "You Did It Yourself in Nine Months" (the title is a reprise of evolutionist J.B.S. Haldane’s reply to a woman who insisted that it was impossible for evolution to change a single cell into a complex human body), is simply the best existing description of how a linear DNA sequence codes for a three-dimensional body. The other deals with "Evolutionary Theodicy," Dawkins’s idea that ecosystems reflect not harmonious central planning but inefficient natural selection. In an efficiently designed world, for instance, trees would be only a few feet tall; in an evolved one, natural selection among individuals competing for sunlight produces a lot of extra wood.

Dawkins’s specialty has always been exploring and extolling natural selection, and this is where The Greatest Show on Earth really shines. But first, since selection is so uncontroversial to Dawkins yet so maligned by F&P, it behooves us to understand what it is. In principle, natural selection is simple. It is neither a "law" nor a "mechanism." It is, instead, a "process"–a process that is inevitable if two common conditions are met. First, some genes must harbor variation because of mutation; and second, some of those mutant genes must be better at replicating than others–usually because they improve the survival and reproduction of their carriers. Suppose, for instance, that the brown-colored ancestors of the polar bear included some carrying mutations in "pigment genes" that gave them lighter coats. These mutant bears would have an advantage: being more camouflaged in the snow than their darker confreres, they’d be able to sneak up on seals more easily and so get more to eat. Because well-fed individuals leave more offspring, over time the bear gene pool would become increasingly enriched in light-color genes. Eventually the species would evolve the familiar white polar bear coat. And this is the way, we think, that all organisms acquire that appearance of "design" that, before Darwin, was attributed to God.

Although we evolutionary biologists might describe the polar bear scenario as "natural selection acting on coat color," that’s only our shorthand for the longer description given above. There is no agency, no external force of nature that "acts" on individuals. There is only differential replication of genes, with the winners behaving as if they were selfish (that’s shorthand, too).

Dawkins describes selection as an "improbability pump," for over time the competition among genes can yield amazingly complex and extraordinary species. Here’s how he describes the evolution of tigers:

A tiger’s DNA is also a "duplicate me" program, but it contains an almost fantastically large digression as an essential part of the efficient execution of its fundamental message. That digression is a tiger, complete with fangs, claws, running muscles, stalking and pouncing instincts. The tiger’s DNA says, "Duplicate me by the round-about route of building a tiger first."

Only Dawkins could describe a tiger as just one way DNA has devised to make more of itself. And that is why he is famous: absolute scientific accuracy expressed with the wonder of a child–a very smart child.


Natural selection has always been the most contested part of evolutionary theory. Many people who have no problem with evolution bridle at the thought that it’s all driven by a mindless and unguided natural process. Indeed, while most scientists accepted the notions of evolution and common ancestry soon after Darwin proposed them in 1859, natural selection wasn’t widely accepted by biologists until about 1930. The main problem was, and still is, a paucity of evidence. While the idea of natural selection seems eminently sound, people want to see it actually changing species in nature. And since the process is usually very slow, that evidence is hard to get for living organisms and nearly impossible for fossils.

It’s this difficulty that leads Dawkins to observe that natural selection is on wobblier legs than the other tenets of evolutionary theory, such as evolutionary change and the branching pattern of life. "Nowadays it is no longer possible to dispute the fact of evolution itself–it has graduated to become a theorum," Dawkins writes, using a neologism for a scientific theory, "or obviously supported fact–but it could (just) be doubted that natural selection is its major driving force."

Well, maybe, but I think Dawkins is a bit too timid in his defense of natural selection. While biologists agree that natural selection is not the only cause of genetic change in populations, the evidence is strong that it’s the only one that can produce the remarkable adaptations of animals and plants to their environment–the elephant’s trunk, the cactus’s spines, the tiger’s fangs and so on–the designlike quality of organisms that, as Darwin put it, "most justly excites our admiration." For one thing, none of the alternatives seem to work. A once-popular rival of natural selection, for instance, was Lamarckism, the idea that the changes acquired by an individual during its lifetime could somehow be imprinted onto its genes and passed on to succeeding generations. This idea failed for two reasons. First, it is incapable of explaining "design" in general: most adaptations, like the tiger’s fangs and cactus’s spines, can’t be credibly explained as acquired changes that later became genetic. Further, it turns out that almost no acquired changes are inherited. One example: despite millenniums of circumcision, Jewish boys are still obstinately born with foreskins.

In contrast, artificial selection has been stunningly successful. Virtually everything that we eat, grow or pet has involved transforming a wild species, through selective breeding, into something radically different. (Bear in mind that the ancestor of the Chihuahua is the wolf.) And of the thousands of selection experiments performed on species in the laboratory, I know of fewer than a dozen that have failed to elicit a response. Why is this relevant to natural selection? As Dawkins observes, "Artificial selection is not just an analogy for natural selection. Artificial selection constitutes a true experimental–as opposed to observational–test of the hypothesis that selection causes evolutionary change." That’s because both processes inexorably result from genetic variation that is adaptive in the current environment, with the "environment" in one case dominated by humans who decide which individuals get to live and breed.

Further, the kinds of adaptations that we find–and don’t find–in nature are precisely what we’d expect if they were built by natural selection. Natural selection, for instance, can’t produce features in one species that are good only for members of a different species. And we never see such features: if one species does something that helps another species, it also helps itself (cleaner fish remove parasites from other species, but thereby get a free meal). Natural selection also predicts that "altruistic" behaviors should be preferentially directed at relatives, who carry the same genes. This, too, is what we see, starting with one’s closest relatives–siblings and children. Natural selection builds features that benefit individuals, not populations or species. As expected, we find features beneficial to individuals but harmful to groups (when male lions usurp a pride of females, they kill the females’ cubs, earning them the right to reproduce but reducing the population of lions).

Finally, we’ve observed natural selection in real time: bacteria evolve resistance to antibiotics, plants to herbicides, insects to insecticides. This is genuine natural selection, even though the species are responding to human interference with the environment. And if you don’t like those, biologists have cataloged dozens of "real" cases of natural selection in which species ranging from plants to birds adapt to natural changes in the environment.

Of course, it’s impossible to prove that every useful feature of organisms was built by selection. The evolution of some species happened when we weren’t around, and other species are impossible to experiment on. Nevertheless, the evidence for selection is sufficiently strong that, although Dawkins notes that the importance of selection might "(just) be doubted," he also observes, "All reputable biologists go on to agree that natural selection is one of [evolution’s] most important driving forces, although–as some biologists insist more than others–not the only one."

Although F&P aren’t biologists, they couldn’t disagree more. While accepting the notion of evolution (grudgingly admitting that it’s "perfectly possible–in fact entirely likely"), they assert, loudly and repeatedly, that natural selection is not just wrong but "quite possibly fatally wrong," not just flawed but "irredeemably flawed." They conclude that natural selection "falls radically short of explaining the appearance of new forms of life."


Could biologists really have been so mistaken these past 150 years? It seems unlikely, but scientific consensus has been wrong before (the idea of continental drift, for instance, was once widely rejected), so let’s examine F&P’s claims. These fall into two groups. The first is that scientists have recently discovered a lot of things about genetics and development that make natural selection look ineffective:

Contrary to traditional opinion, it needs to be emphasized that natural selection among traits generated at random cannot by itself be the basic principle of evolution. Rather, there must be strong, often decisive, endogenous constraints and hosts of regulations on the phenotypic options that exogenous selection operates on.

In other words, Darwin’s assertion that species are "quite plastic" is wrong: organisms are so constrained by their biological nature that they’re not free to change, even if it would be good for them to do so. So what are these "constraints" and "regulations" that render natural selection impotent? F&P proffer a long list (I count at least two dozen items), including the following phenomena: horizontal gene transfer (movement of DNA between individuals of the same generation and between different species), alternative splicing of genes, robustness, modularity, molecular drive, entrenchment, developmental noise, phenotypic plasticity and self-organization. To the layman, this salvo of arcane terms is daunting, and even I, an evolutionary geneticist of forty years’ standing, was taken aback. But not for long, because on close inspection we find that none of these phenomena put much of a brake on natural selection.

Let’s look at one of these: phenotypic plasticity. This refers to the ability of a phenotype–an observable trait or characteristic of an organism–to change within a single generation in response to environmental fluctuations. This is what happens, for instance, when you get a tan. If you have an outdoor cat, its fur gets thicker in winter. The plumage of Arctic animals like the ptarmigan, ermine and Arctic hare changes color from brown to white as winter comes on. Even the lowly brussels sprout has sophisticated plasticity: when it detects that a sprout-eating butterfly has laid eggs on the plant, it changes its leaf chemistry to attract parasitic wasps that destroy those eggs.

F&P imply that somehow–they’re not clear about how–this ability to undergo adaptive developmental change within a generation prevents natural selection from causing genetic change between generations. But that isn’t the case. In fact, far from being an impediment to natural selection, the ability of an individual to adapt to a changing environment is a product of natural selection! Individuals who can tan in the sun (and thus prevent melanomas) have an advantage over those whose pigmentation is fixed. Cats are better off if the length of their fur suits them to the seasons. Genes that are able to respond to predictable variation in the environment will always outcompete those that produce only a fixed (and hence episodically maladaptive) trait.

And so it is with all the "constraints" on selection detailed by F&P. A reader lacking training in science might skim over the rather tedious discussion of these phenomena and assume that F&P know what they’re talking about. That reader would be wrong. Look at it this way: if there really were so many constraints on selection, and if development really were so complex and tightly interconnected that organisms could not respond to natural selection, then why would artificial selection be so effective at changing animals and plants?

Indeed, virtually none of the biologists who study the "constraints" described by F&P share their dim view of natural selection. That’s because, over and over again, selection has wrought the most improbable and unpredictable changes in animals and plants. F&P claim, for example, that selection could never produce winged pigs because of developmental constraints: "Pigs don’t have wings because there is no place on pigs to put them. There are all sorts of ways you’d have to change a pig if you wanted to add wings. You’d have to do something to its weight, and its shape, and its musculature, and its nervous system, and its bones; to say nothing of retrofitting feathers."

Haven’t F&P heard of bats? Bats evolved from small four-legged mammals, probably resembling shrews. You could say the same thing about shrewlike beasts that F&P did about pigs: how could they possibly evolve wings? And yet they did: selection simply retooled the forelegs into wings, along with modifying the animal’s weight, shape, musculature, nervous system and bones for flying (no feathers needed). One of the great joys of being a biologist is learning about the many species in nature whose evolution would appear, a priori, impossible.

Beyond distorting the scientific literature, F&P make a number of claims that are simply silly. I mention just one: "The textbook cases of Mendelian inheritance, in spite of their great historical and didactic importance, are more the exception than the rule." This came as a surprise to me. In fact, cases of Mendelian inheritance (the random assortment of parental genes into sperm and eggs) are the rule; if they weren’t, genetic counseling would be useless. Statements like this typify the authors’ attitude toward science throughout their book: they seize on some new wrinkle in the scientific literature, like a rare gene that doesn’t behave according to Mendel’s rules, and interpret it as a revolution that nullifies all of mainstream biology. This lack of grounding is often seen in work by science journalists who make their living touting "revolutionary" new findings, but it is inexcusable in a supposedly serious book written by academics.

Given F&P’s expertise, you’d expect them to be on firmer ground with their second objection to natural selection, which is philosophical. But again they founder, making illogical arguments and distorting how biologists work. Natural selection is philosophically incoherent, they claim, because it doesn’t "support counterfactuals." (A counterfactual is a conditional statement about what hasn’t happened but could if certain conditions were met. The paradigmatic example is Tevye’s song "If I Were a Rich Man," from Fiddler on the Roof.) What F&P mean is that in real organisms, evolution often involves simultaneous changes in several features, and we simply don’t know which changes reflected natural selection (that is, which traits had variation that directly affected survival or reproduction) and which traits were what they call "free riders": features that weren’t subject to selection but were carried along, perhaps as nonadaptive byproducts of genes that evolved.

Here’s an example: during the evolution of mammals from reptiles, several features changed at the same time. The limbs moved underneath the body, the teeth became differentiated, some jawbones shrank and the braincase got bigger. Now, which of these traits evolved by natural selection, and which, if any, might have only been byproducts? Maybe selection acted to enlarge the cranium but the reduced jawbones were only a passive, nonselected byproduct of "braincase" genes.

Even single traits have several effects that could, in principle, respond differently to natural selection. The hemoglobin in our blood, for example, carries oxygen but also happens to be red. How do we know that selection didn’t favor the color itself (perhaps to make anger or blushing more evident) rather than the oxygen-transport ability?

Finally, some "traits" are inseparable even in principle: how can we tell whether the ancestors of whales experienced selection for "swimming" as opposed to "flapping their flukes up and down?" Fluke-flapping, of course, causes swimming. Evolutionary biologists aren’t much concerned with this sort of distinction, and I won’t consider it further.

Because biologists can’t make any of these distinctions, say F&P, natural selection is incoherent. They call this the "selection-for" problem. And they add that artificial selection doesn’t suffer from this problem. Since animal and plant breeders consciously select for certain traits, like higher milk yield or uglier bulldogs, we know exactly which features experience selection (the bulldog’s puggish face) and which are byproducts (the respiratory problems that come with puggish faces). F&P therefore find Darwin’s analogy between artificial and natural selection dubious, for "only minds are sensitive to distinctions among counterfactuals," and "natural selection doesn’t have a mind." In the end, declare F&P, natural selection cannot be true because "a theory that doesn’t determine the truth values of relevant counterfactuals cannot explain the distribution of traits in the actual world."

But wait a minute. If you translate that last sentence into layman’s English, here’s what it says: "Since it’s impossible to figure out exactly which changes in organisms occur via direct selection and which are byproducts, natural selection can’t operate." Clearly, F&P are confusing our ability to understand how a process operates with whether it operates. It’s like saying that because we don’t understand how gravity works, things don’t fall.


What’s worse is that, contra F&P, evolutionary biologists have grappled for decades with the question of how to decide which evolving features of species experience natural selection and which do not. And they’ve devised observational, experimental and statistical ways to make this distinction. In the case of hemoglobin, the answer is obvious: selection couldn’t act on color because in many animals the blood can’t be seen through the skin. More important, mutant hemoglobins that have lost their ability to carry oxygen but remain red are invariably lethal.

Here’s a more realistic example. Perhaps the most famous case of natural selection in action is the color change that occurred in Britain’s "peppered moth" over the past 150 years. Before the Industrial Revolution, these moths had white wings speckled lightly with black, although avid collectors found a few all-black mutants. As pollution from manufacturing increased the concentration of suspended particles in the air, black moths became more numerous, and eventually predominated in many places. When clean air laws reduced Britain’s pollution in the 1950s, the evolution of wing color reversed, and in most places the white color once again became common. The difference between white and black moths was shown to reside at a single gene.

What caused these evolutionary changes? There were several theories. One was that the target of selection wasn’t the moth’s color but the survival of caterpillars that, while not showing the color differences of adults, happened to be affected by the same gene. Another suggestion was that natural selection acted on color: perhaps sharp-sighted birds picked off moths whose color contrasted with that of the trees on which they rested. In unpolluted woods, lichen-covered trees are light-colored but turned black as pollution increased. This would give a selective advantage first to the dark-colored moths and then, as pollution abated, to light-colored moths.

F&P would presumably counsel us to give up at this point, since we can’t, they say, distinguish between the counterfactuals of selection "for" larval survival and "for" adult color. But we can! Breeding experiments in the laboratory showed that the survival of caterpillars couldn’t explain the increase and subsequent decline of the black form. In contrast, field experiments that involved observing predation on dead moths of different colors fastened to trees of different colors, and on live moths of different colors released in unpolluted woods, showed that selection on color was strong, easily able to explain the evolutionary changes observed in nature.

And we now have dozens of similar studies–in fish, birds, insects and plants–all successfully distinguishing those traits experiencing natural selection from those that are "free riders." Sadly, F&P show no awareness of this literature, which is hardly obscure, since it includes some of the famous cases, like the peppered moth, that we use to teach evolution to undergraduates.

Of course, in many cases we’ll never know exactly which features experienced direct natural selection or how that selection worked. We can’t return to the Jurassic, for instance, and find out why the stegosaurus had those big plates on its back. Were they radiators for regulating body temperature? Did they fend off predators? Or were they only a byproduct of some other adaptive change in the skeleton? Our inability to understand all the details, though, is hardly a reason to claim that natural selection doesn’t work.

So if natural selection played at best a trivial role in evolution, what do F&P offer as an alternative explanation for the marvelous adaptations of plants and animals? Nothing. They finally admit that "we don’t know what the mechanism of evolution is. As far as we can make out, nobody knows exactly how phenotypes evolve. We think that, quite possibly, they evolve in lots of different ways." After much demurring, they float the idea that "organisms ‘catch’ their phenotypes from their ecologies in something like the way that they catch their colds from their ecologies." Although this "explanation" links evolution to ecology, it’s completely meaningless. How did ancestral whales catch their flukes and flippers from the water? How did ancestral birds catch their wings from the air? F&P don’t say.

I’ve pondered long and hard how two thoughtful intellectuals could go so wrong. Behind much of F&P’s animus toward natural selection, it seems, is their disdain for evolutionary psychology, which sees much of modern human behavior as the product of natural selection acting on our ancestors. (What Darwin Got Wrong includes an appendix of quotations from evolutionary psychologists, whom F&P label "unabashed adaptationists.") Here F&P have a point, for while much of evolutionary psychology is interesting, worthwhile science, it includes a speculative fringe (especially inviting to journalists) that proposes fanciful stories about how natural selection could produce behaviors like music-making, rape, clinical depression and even religion.

Fodor has long been an extreme rationalist who believes the mind is a logic machine and that the orderliness of our world must be deducible a priori from elegant laws. It’s no surprise, then, that F&P produce a long diatribe against B.F. Skinner’s behaviorism, the theory that animals (including humans) initially behave randomly and then repeat those behaviors that get rewarded. In its randomness, messiness and contingency, behaviorism resembles natural selection. And F&P are clearly infuriated by evolutionary psychologists’ use of natural selection to explain not only human behavior but the human mind.

But evolutionary psychology is a red herring here. F&P are surely entitled to criticize evolutionary psychology, and evolutionary psychologists may be expected to reply. Motivations aside, F&P’s attempt to undermine evolutionary biology is a quixotic and misguided undertaking. Their claim to have nullified 150 years of science, and one of humanity’s proudest intellectual achievements, with some verbal legerdemain, is not only breathtakingly arrogant but willfully ignorant of modern biology. In the end, F&P’s contrarian efforts are all belied by the world of Richard Dawkins–the flourishing field of modern evolutionary biology, where natural selection remains the only explanation for the wondrous adaptive complexity of organisms.




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