Peripatus may walk prouder in the pleasures of pedigree. We humans, as intellectual descendants of Aristotle, the original peripatetic, might consider a favorite motto from “the master of them that know”—well begun is half done (from the Politics, book 5, chapter 4). Apply it first to the onychophorans themselves—for in a tough world dominated by contingent good fortune in surviving extinction, a strong beginning of high diversity affords maximal prospect for some legacy long down the hard road. But apply it also to us, the paleontologists who strive to understand this complex history of life. By turning Hallucigenia upside down, we have probably taken a large step toward getting the history of life right side up.
7 | Revising and Extending Darwin
25 | What the Immaculate Pigeon Teaches the Burdened Mind
TWO SUCCESSIVE symbols of Saint Louis typify the passages of our century. Saarinen’s magnificent arch, gleaming and immaculate, seems to soar from the Mississippi River into heaven (an optical illusion, in large part, cleverly produced by a gradual decrease in edge length from 54 feet at the base of the structure to 17 feet at the summit. Our minds expect a constant size, and the marked decrease therefore makes the summit seem ever so much higher than its actual 630 feet—the size of an ordinary skyscraper in a modern city). By contrast, St. Louis’s older symbol, an equestrian statue of the eponymous Louis IX, the only canonized king of France, still stands in front of the art museum in Forest Park. It is anything but immaculate, thanks to that primary spotting agent of all cities—pigeons.
As a team, pigeons and the statue of Saint Louis go way back. The current statue is a 1906 recasting in bronze of the impermanent original made for the main entrance to one of the world’s greatest expositions—the 1904 World’s Fair held to celebrate (if just a bit late) the centenary of the Louisiana Purchase. The fair must have been spectacular; my wife’s family, raised in Saint Louis, still mentions it with awe in stories passed down through three generations. The fair gave us iced tea, ice cream cones, and a great song, “Meet Me in Saint Louis, Louis” (many folks don’t even know the next line—“meet me at the fair”).
A ferris wheel stood twenty-five stories high; Scott Joplin played his rags. The Pike, main street of the amusement area, featured daily reenactments of the Boer War and the Galveston Flood. The world’s greatest athletes came to participate in the third Olympic Games. The fairgrounds, bathed at night in the newfangled invention of electric lighting, inspired Henry Adams to write: “The world has never witnessed so marvelous a phantasm; by night Arabia’s crimson sands had never returned a glow half so astonishing [a statement that will need revision after the night bombing of Desert Storm], as one wandered among long lines of white palaces, exquisitely lighted by thousands and thousands of electric candles, soft, rich, shadowy, palpable in their sensuous depths” (from The Education of Henry Adams). This statement also makes sense of the next two lines of the famous song: “Don’t tell me the lights are shining/Any place but there.”
Intellectuals must be constantly clever and industrious. We know that we are peripheral to society’s main thrust, and we must be constantly vigilant in seeking opportunities to piggyback on larger enterprises—to find something so big and so expensive that prevailing powers will grant us a bit of space and attention at the edges. The hoopla and funding of major exhibitions often gives us a little room for a smaller celebration in our own style. I was invited to give a speech at something called the “Academic Olympiad” in Seoul during the last Olympic games. (I wasn’t able to go and never heard boo about the outcome—though television deluged us with details about javelins and the hop, step, and jump.) Similarly, since the 1904 World’s Fair set up shop right next to Washington University, academicians rallied to hold a “Congress of Arts and Science” at the Universal Exposition (as the fair was officially called). At this collocation, the great American biologist Charles Otis Whitman gave a leading address with the general title: “The Problem of the Origin of Species.” He spoke primarily about pigeons.
Whitman’s work, while treating so humble a subject, had a certain panache and boldness. He wrote at a time when biologists, though fully confident about the fact of evolution, had become very confused and polemical about the causes of evolutionary change. Darwin’s own theory of natural selection had never commanded majority support (and would not emerge as a general consensus until the 1930s). As visitors ate their ice-cream cones on the Pike, at least three other theories of evolutionary change enjoyed strong support among biologists—(1) the inheritance of acquired characters, or Lamarckism; (2) the origin of species in sudden jumps of genetic change, or mutationism; (3) the unfolding of evolution along limited pathways set by the genetic and developmental programs of organisms, or orthogenesis (literally, “straight line generation”). Whitman, who had been raising and breeding pigeons for decades, wrote his article to defend the last alternative of orthogenesis, thereby relegating Darwinian natural selection to a small and subsidiary role in evolution.
Whitman’s boldness did not lie in his choice of the orthogenetic theory—for this argument was a strong contender in his day, though probably the least popular of the three major alternatives to Darwinism. We judge a man intrepid when he uses his adversary’s tools or data to support a rival system. A famous story about Ty Cobb tells of his disgust with Babe Ruth’s new style of power hitting (Ruth swatted more home runs per year all by himself than most entire teams had formerly managed in a season). Cobb, the greatest and most artful practitioner of the earlier style of slap, hit, and scramble for a run at a time, held his hands apart, slipped them together high on the bat as the pitch came in (thus achieving maximal control while sacrificing power), and then slapped the ball to his chosen spot; Ruth, by contrast (and following the strategy of all sluggers), held the bat at the end and swung away, missing far more often than he connected. Cobb regarded this style as easy and vulgar, however effective. One day, near the end of his career, and to show his contempt in the most public way, Cobb ostentatiously held the bat in Ruth’s manner, hit three home runs in a single game and then went right back to his older, favored style forever after.
Whitman’s assault on Darwin’s theory from within was far bolder and more sustained, if not quite so showy. For Whitman had chosen, for study over decades, the very organisms that Darwin had selected as the primary empirical support for his own theory—pigeons.
Darwin stated in chapter 1 of the Origin of Species:
Believing that it is always best to study some special group, I have, after deliberation, taken up domestic pigeons. I have kept every breed which I could purchase, or obtain, and have been most kindly favored with skins from several quarters of the world…. I have associated with several eminent fanciers, and have been permitted to join two of the London Pigeon Clubs.
Darwin states an excellent reason for his choice in the next sentence:
The diversity of the breeds is something astonishing. Compare the English carrier and the short-faced tumbler, and see the wonderful difference in their beaks…. The common tumbler has the singular and strictly inherited habit of flying at a great height in a compact flock, and tumbling in the air head over heels…. The Jacobin has the feathers so much reversed along the back of the neck that they form a hood…. The fantail has thirty or even forty tail-feathers, instead of twelve or fourteen, the normal number in all members of the great pigeon family; and these feathers are kept expanded, and are carried so erect that in good birds the head and tail touch.
These breeds are so different that any specialist, if “he were told that they were wild birds,” would assume major taxonomic distinction based upon substantial differences. “I do not believe,” Darwin writes, “that any ornithologist would place the English carrier, the short-faced tumbler, the runt, the barb, pouter, and fantail in the same genus.”
And yet, demonstrably by their interbreeding and their known history, all these pigeons belong to the same species, and therefore have a common evolutionary parent—the rock-pigeo
n, Columba livia. Darwin writes: “Great as the differences are between the breeds of pigeons, I am fully convinced that the common opinion of naturalists is correct, namely, that all have descended from the rock-pigeon (Columba livia).” (Darwin might have chosen the even more familiar example of dogs to make the same point, but he was not convinced that all dog breeds came from a common wolf source, whereas the evidence for a single progenitor of all pigeons seemed incontrovertible.) Only one step—the key analogy that powers the entire Origin of Species—remained to secure the most important argument in the history of biology, and to make pigeons the heroes of reform: If human breeding, in a few thousand years at most, could produce differences apparently as great as those separating genera, then why deny to a vastly more potent nature, working over millions of years, the power to construct the entire history of life by evolution? Why acknowledge the plain fact of evolution among pigeons, and then insist that all natural species, many no more different one from the other than pigeon breeds, were created by God in their permanent form?
Whitman, of course, did not disagree with Darwin’s focal contention that pigeons had evolved, but he strongly questioned Darwin’s opinion on how they and other species had arisen. Charles Otis Whitman (1842–1910), though scarcely a household name today, was the leading American biologist of his generation. He was, perhaps, the last great thinker to span the transition from the pre-Darwinian world to the rise of twentieth-century experimental traditions—for he had studied with Louis Agassiz, the last true creationist of real stature, and he lived to found and direct the symbol of rigorous modernism in American biology, the Marine Biological Laboratory at Woods Hole, still very much in vigorous operation. In his research, Whitman gained fame for meticulous work on cell-lineage studies in embryology—tracing the eventual fate of the first few embryonic cells in forming various parts of the body. In promoting this form of research as canonical in Woods Hole, and in establishing at his new laboratory the finest young American biologists, Whitman succeeded in bringing to this country the experimental and mechanistic traditions championed as the soul of modernism in Europe.
In this light, I have always had trouble remembering that Whitman’s main love in research lay in the opposite camp of “old-fashioned” and largely descriptive natural history—decades of work on the raising, breeding, and observation of pigeons. This passion even led to his death. In Chicago (where he served as professor of Biology at the University), on the first chill day of December, 1910, Whitman worked all afternoon in his backyard, hastily preparing winter quarters for his pigeons to save them from the cold. As a result, he developed pneumonia and died five days later. F. R. Lillie, once his assistant and then his successor at Woods Hole, eulogized his old boss: “In his zeal for his pigeons, he forgot himself.”
Unfortunately, Whitman died before completing and integrating his lifelong work on pigeons. He had published a few preliminary addresses (most notably, his offering in Saint Louis), but never the promised major statement. I can’t help thinking that the history of evolutionary thought might have been different had Whitman lived to promulgate and proselytize his non-Darwinian evolutionary ideas. His colleagues did gather his notes and data into a three-volume posthumous work on pigeons, finally published in 1919. But this work (the basis for my essay) was too disjointed, too incomplete, and, above all, too late to win its potential influence.
Darwin’s pigeon agenda extended beyond the simple demonstration of evolution. He also wished to promote his own theory about how evolution had occurred—natural selection. Again, he relied on argument by analogy: Pigeon breeds had been made by artificial selection based on human preferences for gaudiness (pouters, fantails) or utility (carriers, racers)—see figure. “When a bird presenting some conspicuous variation has been preserved, and its offspring have been selected, carefully matched, and again propagated, and so onwards during successive generations, the principle is so obvious that nothing more need be said about it.” (This quotation comes from Darwin’s most extensive discussion of pigeons—two long chapters in his 1868 book on The Variation of Animals and Plants under Domestication. Other statements in this essay are cited from the Origin of Species, 1859). But if selection is so undeniably the cause of small-scale evolution over millennia, why deny to nature the power for similar, but far greater, transformation over eons: “May not those naturalists who…admit that many of our domestic races have descended from the same parents—may they not learn a lesson of caution, when they deride the idea of species in a state of nature being lineal descendants of other species?”
Orthogeneticists like Whitman did not deny natural selection, but viewed Darwin’s force as too weak to accomplish anything beyond a bit of superficial tinkering. Natural selection, they argued, can make nothing and can only accept or reject the variation that arises naturally among differing organisms in an interbreeding population. If the genetic and embryological systems of organisms prescribe a definite direction to this variability, then natural selection cannot deflect the course of evolutionary change. Suppose, for example, that size in offspring only varied in a single direction from parental dimensions—that is, all kids ended up either the same size or taller than their folks. What could natural selection do? Darwin’s force could hasten an inherent trend by favoring the taller offspring. At most, selection could prevent a trend and keep the population stable, by eliminating the taller offspring and preserving only those of parental dimensions. But selection could not work counter to the inherent direction of variation because no raw material would be available for trends in any direction other than increasing size. Thus, selection would be a force subsidiary to an internal tendency for directional variation—or orthogenesis.
Darwin’s illustration of the showiest of all pigeon breeds—the English fantail. This figure comes from his 1868 book: The Variation of Animals and Plants Under Domestication. Courtesy of Department of Library Services, American Museum of Natural History.
Darwin, of course, was well aware of the logic of this destructive argument. He countered by claiming that, in fact, variation has no inherent direction and occurs “at random” relative to the favored path of natural selection. (This debate set the context for Darwin’s confusing claim that variation is random, a statement that has led many people into the worst vernacular misconception about Darwinism: the false belief that Darwin viewed evolutionary change itself as random, and that the manifest order of life therefore disproves his theory. In Darwin’s scheme, variation is random, but natural selection is a deterministic force, adapting organisms to changes in their local environments. In fact, Darwin upheld the randomness of variation in order to empower natural selection as a directional agent.) If variation is only random raw material, occurring in no favored direction relative to environmental advantages, then some other force must shape this formless potential into adaptive change. Random raw material requires another mechanism to supply direction by carving out and preserving the advantageous portion—and natural selection plays this role in Darwin’s system. But orthogenetically directed variation requires no other shaping force and can set an evolutionary trend all by itself.
Whitman therefore set out to prove that an inherent trend in variation pervades the pigeon lineage—a trend too powerful for natural selection to alter in direction or even to slow substantially. Whitman based his argument on patterns of coloration and began by reversing Darwin’s assumption about the plumage of parental forms.
The feral pigeons that speckle our public statuary show two basic color patterns in their extensive repertoire of variation. Some have two black bars on the front edges of their wings and a uniform gray color elsewhere; others develop black splotches, called checkers, on some or all wing feathers, but also retain the two bars (though usually in more indistinct form). The bars, in any case, are composed of checkers (on several adjacent feathers) that line up to produce the impression of a broad continuous stripe (see figures taken from Whitman’s posthumous monograph).
Darwin h
ad assumed that ancestral pigeons were two-barred and that checkers represent an evolved modification by intensification of coloration. Whitman cleanly reversed Darwin’s perspective:
The latter [two-barred] was regarded by Darwin as the typical wing pattern for Columba livia; the former [checkered] was supposed to be a variation arising therefrom, a frequent occurrence but of no importance. Just the contrary is true; the checkered pigeon represents the more ancient type, from which the two-barred type has been derived.
Whitman’s figure of the two-barred wing pattern, which he regarded as an advanced state in his orthogenetic sequence. Courtesy of Department of Library Services, American Museum of Natural History.
Whitman’s illustration of the checkered pattern—the primitive state in the evolution of pigeon wing colors. Courtesy of Department of Library Services, American Museum of Natural History.
This reversal is of no great significance in itself, unless you happen to be a pigeon fancier devoted to the peculiarities of these generally unloved creatures. But Whitman properly made much of his inversion because his favored sequence of checkers-to-bars formed the major part of his proposed (and inexorable) orthogenetic sequence of internally prescribed variation—an evolutionary pattern inherent in the biological organization of pigeons and quite beyond the power of natural selection to deflect. The orthogenetic trend, Whitman argued, moved from original diffusion to later concentration of color. Checkers plus indistinct bars must precede clear bars and no checkers. In the lines following the quotation just cited, Whitman writes:
The direction of evolution in pattern in the rock pigeons has been from a condition of relative uniformity to one of regional differentiation.
Eight Little Piggies Page 35
