Eight Little Piggies

by Stephen Jay Gould

  The primitive swim bladder, Darwin argues (and we may reverse the argument for lungs), may also have worked in a subsidiary way in gas exchange—and this latter role may have been intensified as the original use dropped out, in the evolution of the lung. But the one-for-two principle cannot resolve the problem of intermediary stages—for how could a fish breathe as the original lungs lost their primary function?

  Darwin therefore calls upon his second, coupled principle of two-for-one. Many vital functions are performed by two or more organs, and one can change so long as the other continues to play the needed role. We can breathe through both our nose and mouth—and thank goodness, or we would all be dead of colds:

  Two distinct organs sometimes perform simultaneously the same function in the same individual…. In these cases, one of the two organs might with ease be modified and perfected so as to perform all the work by itself;…and then this other organ might be modified for some other and quite distinct purpose.

  We can now understand why Darwin liked the example of lungs and swim bladders so much. He had made a reasonable conjecture about one-for-two in arguing for supplementary respiration in swim bladders, and he had definite evidence about two-for-one in the presence of numerous living fishes with dual systems of breathing—gills and lungs. (The official taxonomic name of the lungfishes, Dipnoi, means “two breathing.”) Thus, using lungs and swim bladders as his key example in a central defense of large-scale evolution, Darwin concluded:

  For instance, a swim bladder has apparently been converted into an air-breathing lung. The same organ having performed simultaneously very different functions, and then having been specialized for one function; and two very distinct organs having performed at the same time the same function, the one having been perfected whilst aided by the other, must often have largely facilitated transitions.

  Readers might fairly balk at this point. The argument coupling one-for-two and two-for-one is logically sound, but doesn’t it smack of special pleading and gross improbability? How often can you expect to find such a combination? Perhaps both situations are uncommon; their conjunction would then be nearly incomprehensible. Rare times rare equals rare squared, or effectively impossible.

  But we now come to the true beauty of Darwin’s argument. Neither situation is rare, and the two phenomena—one-for-two and two-for-one—are not really separate at all. Both are expressions of a deeper, and profoundly important, principle—redundancy as the ground of creativity in any form. They are two sides of the same coin—and the coin, although priceless in intellectual value, is as common as a penny.

  The notion that organs are “for” particular things, ideally suited for one and only one job, is a vestige of old-style creationism—the idea that God made each creature, fully formed and perfect in function. If each organ existed explicitly for a single role, then I suppose that one organ doing more than one thing would be rare, and that two organs doing the same thing might be even rarer. But organs were not designed for anything; they evolved—and evolution is a messy process brimming with redundancy. An organ might be molded by natural selection for advantages in one role, but anything complex has a range of other potential uses by virtue of inherited structure—as we all discover when we use a dime for a screwdriver, a credit card to force open a door, or a coat hanger to break into our locked car (not someone else’s, let us hope, and surely not, let us pray, for ending unwanted pregnancies in our newly dawning era of restrictions). Any vital function narrowly restricted to one organ gives a lineage little prospect for long-term evolutionary persistence; redundancy itself should possess an enormous advantage. (Redundancy in this form solves the otherwise intractable problem of evolution in mammalian jaws, as outlined above. Intermediary forms, as shown by direct evidence of fossils, not abstract conjecture, developed a second articulation between dentary and squamosal bones [the current mammalian jaw joint], and elements of the old articulation could then lose their former function and pass into the ear.)

  In fact, the swim bladder itself provides an excellent example of multiple possibilities as a norm. The swim bladder is primarily an organ of buoyancy in teleost fishes. By filling the bladder with gas, an animal that would otherwise sink becomes neutrally buoyant and can rest without expending energy in the midst of the water column. (In a related function, fishes at neutral buoyancy gain more power in forward motion because they need not divert energy into supplying lift to counteract sinking—see R. McNeill Alexander in the bibliography. Interestingly, some sharks are pelagic (floating) in habit; how can they stay up, since their entire lineage lost the organ that becomes a lung or swim bladder in other fishes? These sharks have enormous livers constructed largely of a hydrocarbon with a density considerably less than seawater—another good example of multiple use as a norm.

  But the swim bladder performs at least three other important but secondary functions in many species of teleost fishes:

  (1) Most curiously, perhaps, the swim bladder has reacquired a supplementary respiratory function in several lineages of fishes, all living in swampy or stagnant waters, where gulping air at the surface might be an important alternative to breathing with gills.

  (2) Many teleosts use their swim bladder as an organ of sensation. Since gas is so responsive to changes in pressure, some fishes can judge their depth in the water column with receptors embedded in the wall of their swim bladder. Many other fishes use their swim bladder as an accessory organ of hearing. Gases are more compressible than water, and sound vibrations may be recorded more sensitively in their impact upon swim bladder gases than upon any other part of the body. Supplementary hearing has evolved in at least two strikingly different ways. Some fishes have developed thin forward extensions of the swim bladder; these pass through openings of the skull and make direct contact with the ear. In another major group, the cypriniforms (including most of the world’s freshwater fishes), vibrations from the swim bladder are transmitted to the ear via a chain of three separate bones located on either side of the vertebral column and called Weberian ossicles to honor the German scientist who recognized their mode of operation in 1820. (Darwin used this example of multiple function in the Origin of Species.)

  (3) Sound production: Again, several lineages use the swim bladder either to enhance sounds made by other parts of the body or as a direct agent of production. (Some fishes are essentially silent, but many make sounds, especially in courtship or in aggressive displays.) The triggerfish Balistes (another lovely name) stridulates by rubbing its postclavicle bone against its cleithrum—but this otherwise minor sound is greatly amplified by resonance from the adjacent swim bladder. Another group of fishes grates its pharyngeal teeth and also turns a little rumble into a modest roar by resonance of the swim bladder. In other fishes, the swim bladder produces sounds directly by expulsion of gas bubbles. T. H. Huxley once wrote a special note to Nature (in 1881) to describe what can only be called herring farts. These fish expel gas in pulses from the swim bladder out an orifice adjacent to the anus. In the oh-so-proper style of scientific reporting, a British review article of 1953 described Huxley’s suggestion “that the mouse-like squeaks made by captured herring might be caused by the escape of gas through the posterior opening.”

  If I may move, in conclusion, from minor end rumblings to a renewed assault upon the high ground, I don’t know if the Origin of Species contains an argument more general or more important than Darwin’s recognition that pervasive redundancy makes evolution possible. If animals were ideally honed, with each part doing one thing perfectly, then evolution would not occur, for nothing could change (without losing vital function in the transition), and life would quickly end as environments altered and organisms did not respond.

  But rules of structure, deeper than natural selection itself, guarantee that complex features must bristle with multiple possibilities—and evolution wins its required flexibility thanks to messiness, redundancy, and lack of perfect fit. Human creativity is no different, for I think we are dealing wit
h a statement about the very nature of organization—something so general that it must apply to any particular instance.

  How sad then that we live in a culture almost dedicated to wiping out the leisure of ambiguity and the creative joy of redundancy. These days, even the most complex concepts must be reduced to photo opportunities and sound bites, and elections are decided by fifteen-second images of men surrounded by flags and alleged criminals walking through symbolic revolving doors. We may be creating a generation of sheep—and although these pleasant mammals outnumber New Zealanders by almost twenty-five to one, I rather suspect that Homo sapiens, properly nurtured by redundancy and ambiguity, will continue to prevail.

  Redundancy, and its counterpart of ambiguity in multiple meaning, are our way, our most precious, most human way. We rail at computers because for all their awesome power, they do not grasp our essential ambiguities. They cannot adequately translate one of our languages into another, and we must speak to them in a way utterly unnatural for us—that is, without ambiguity (hence an entire industry devoted to debugging). Faced with La Guardia’s or Darwin’s errors, they grind to a halt. We adjust, we parry, we prevail, we transcend. It could be one hell of a partnership, so long as we keep the upper hand. I shall place my bets on the shepherds of New Zealand and hope that the analogy holds.

  3 | Vox Populi

  Evolving Visions

  8 | Men of the Thirty-Third Division: An Essay on Integrity

  MY FATHER, like so many men of his generation, lost the opportunity for a college education through a conspiracy of circumstances—first the depression, then a stint in the war, and finally too much time gone and too many kids to feed when the external hurdles finally dropped. But Leonard Gould was a man of great intellect, keen perception, and broad interests. Late in his life, and largely in response to my concerns, he became enthralled with human evolution and spent much of his retirement reading—with his characteristic, consummate care—the literature, both popular and technical, of paleoanthropology.

  One day, during a visit, he approached me in great frustration. Spread before him were the latest books of America’s two greatest anthropologists. “Look,” he said, “Professor Uno ridicules Professor Due for believing such a silly idea, but Due really says something quite different; look right here on the page. Meanwhile Due excoriates Uno for speaking nonsense, but look here, Uno doesn’t say any such thing. Now what am I misunderstanding?” My heart would sink whenever my father attributed the carelessness of scholars to his own ignorance based on lack of professional training. I could never get him to understand that advanced degrees and letters after a name guarantee no new level of wisdom and that, in the end, there is no substitute for old-fashioned careful reading. I could never convince him that he had a far better chance than Uno or Due to grasp the integrity of another man’s argument. After all, he had the prerequisites of basic intelligence and adequate knowledge of jargon; and he possessed, in addition and in abundance, two cardinal traits rarely encountered in active scholars: time to read carefully, and lack of distorting preconceptions. I read the two books. He was right again. Uno and Due were ripping apart the nonexistent caricatures of each other’s ideas.

  I’ve been in this business for nearly a quarter century now, and nothing depresses me more than the rampant, seemingly inveterate mischaracterization that lies at the core of nearly every academic debate. We are not incapable of arguing about intellectual substance and empirical reality, but we sure seem to prefer misunderstanding as a subject for invective. The root of this lamentable behavior can only lie in careless habits of reading and thinking (or, worse, in our willingness to argue without reading at all).

  The foundation of my distress is a moral position traditionally precious to the world of intellectuals. What do we have for judgment, worth, and honor but the integrity of our ideas—using integrity both in the moral meaning of honesty in argument and, even more importantly, in the literal sense of uniting our various notions into coherent intellectual structures? We may define brilliance in scholarship as the surprise, power, and beauty of such integrity at its finest. The truly awesome intellectuals in our history have not merely made discoveries; they have woven variegated, but firm, tapestries of comprehensive coverage. The tapestries have various fates: Most burn or unravel in the footsteps of time and the fires of later discovery. But their glory lies in their integrity as unified structures of great complexity and broad implication.

  Yet, in our harried world of sound bites and photo ops, we focus on anecdote rather than structure, and scholars are identified by items rather than by their precious tapestries. Lavoisier discovered oxygen, Darwin evolution; an apple fell in Newton’s sight, and Mozart had a dirty mind. Bad enough in the hagiographical mode, when good intentions accompany items meant as emblems of valor. But what of the dark side, so pervasive in academic life? What can be more destructive of our fragile community than the mode of criticism that slices a jagged hunk out of the tapestry, misreads and simplifies the item as a strawman in a campaign of destruction, and then tries to define the scholar by the misappropriated patch? He who steals my purse does steal trash, but he who slices and dices my tapestry cuts out my heart.

  May I honor my father’s respect for integrity by correcting a legend rooted in the slice-a-patch method of commentary, and involving the founder of the field represented by squabbling Professors Uno and Due—the study of human fossils.

  Only two substantial discoveries of human fossils predate Darwin’s great book on the Descent of Man (1871), and neither offered any evidence for human ancestry. The Neanderthals, widely misinterpreted at first as modern skeletons with deformation or disease, represent a very late side-branch in the tale of human evolution, while the Cro-Magnons, living even closer to the present time, are already us in all crucial aspects of anatomy and brain size.

  Eugène Dubois, a medical officer in the Dutch army, found the first fossils of an old and truly ancestral human in 1891 and 1892, ten years after Darwin’s death. The tale of his discovery ranks among the best in the annals of scientific perseverance and perspicacity. Dubois (1858–1940), a physician and lecturer in anatomy at Amsterdam University, became enthralled with the new science of evolution and longed to find the greatest desideratum of all, the closest paleontological equivalent to the holy grail—the “missing link” (to use the antiquated terminology of Dubois’s day). Accepting the usual view that tropical Asia offered greatest promise, and taking advantage of his nation’s colonial presence in Indonesia, Dubois resigned his post in Amsterdam and signed up for an eight-year hitch as medical officer second class in the Royal Dutch East Indies Army, with the clear ulterior motive of using every spare moment in the search for human ancestors. He was disappointed on Sumatra from 1887 to 1890, but then struck pay dirt in Java two years later along the Solo River near the village of Trinil. There, in October 1891, Dubois’s workmen found a skull cap and later, in August 1892, a femur of a primate with marked human affinities. The thigh bone could scarcely be distinguished from our own, but the skull cap belonged to a creature with a brain of some 900 cm3, or roughly two-thirds modern size. (The romantic image of field work depicts our hero, sleeves rolled up, pickaxe in hand, and sweating bullets in the scorching sun as he unearths his precious find. The realities of colonial life and complex expeditions dictate less inspiring but more realistic scenarios. Dubois entrusted the day-to-day digging to convict laborers commanded by two army sergeants. The fossils, packed in teak leaves, then accumulated on the veranda of Dubois’ headquarters, where he presumably first saw his quarry.)

  Dubois reconstructed this greatest of nineteenth-century discoveries as a human of about our bulk and build, fully erect in posture (judging from the femur), but with a brain two-thirds our size—in short, an excellent “missing link” on the theory, already popular in Dubois’s time and now well established, that upright posture preceded, and may have triggered, the enlargement of the human brain. Dubois named his creature Pithecanthropus erectus,
or the ape-man who walked upright. We continue to regard Dubois’s species as our direct ancestor, though a revised notion of even closer affinity led to a redesignation as Homo erectus. This species has now been found throughout the Old World, both elsewhere in Asia (initially as the famous Peking Man, discovered during the 1920s) and, more recently, in its original African home. Dubois’s beginning, a skullcap and femur from Java, has blossomed into a well-documented ancestor, widely spread over three continents.

  Such an auspicious start might have brought only honor and further triumph, but a witches’ brew of scientific contentiousness, temper of the times, and quirks in Dubois’s own psyche soon derailed any pleasant development and turned Dubois’s bounty into bitterness. He returned from Java in 1895 and began to display his specimens at scientific meetings. He received much warm support and several overt testimonials in medals and honorary doctorates. But he also generated a firestorm of doubt and protest in this perennially contentious field. Some labeled his find “merely” an ape, others a diseased modern skeleton, still others a false jumble of a modern human femur with an ape’s skullcap.

  At this point, we encounter the canonical legend of Dubois—the story that I shall attempt to refute by replacing the slashed patch of its content back into Dubois’s intellectual tapestry. The basic facts are not in dispute; the traditional interpretation, however, is not only wrong, but perversely backwards.

  At the turn of the new century, Dubois withdrew the Trinil bones, locked them away, and refused access to all scientists for nearly a quarter century. Finally, in 1923, spurred by entreaties and pressured from high places (inquiries in Parliament and representations from the Royal Dutch Academy of Sciences), Dubois relented and brought his specimens back to scientific scrutiny. But now, he pulled the ultimate volte-face and declared in his final publications that the Trinil skullcap and femur belonged to a giant gibbon!