The Panda's Thumb: More Reflections in Natural History

by Stephen Jay Gould

  If Darwin had been distressed by his failure to impress Wallace with sexual selection, he was now positively aghast at Wallace’s abrupt about-face at the finish line itself. He wrote to Wallace in 1869: “I hope you have not murdered too completely your own and my child.” A month later, he remonstrated: “If you had not told me, I should have thought that [your remarks on Man] had been added by some one else. As you expected, I differ grievously from you, and I am very sorry for it.” Wallace, sensitive to the rebuke, thereafter referred to his theory of human intellect as “my special heresy.”

  The conventional account of Wallace’s apostasy at the brink of complete consistency cites a failure of courage to take the last step and admit man fully into the natural system—a step that Darwin took with commendable fortitude in two books, the Descent of Man (1871) and the Expression of the Emotions (1872). Thus, Wallace emerges from most historical accounts as a lesser man than Darwin for one (or more) of three reasons, all related to his position on the origins of human intellect: for simple cowardice; for inability to transcend the constraints of culture and traditional views of human uniqueness; and for inconsistency in advocating natural selection so strongly (in the debate on sexual selection), yet abandoning it at the most crucial moment of all.

  I cannot analyze Wallace’s psyche, and will not comment on his deeper motives for holding fast to the unbridgeable gap between human intellect and the behavior of mere animals. But I can assess the logic of his argument, and recognize that the traditional account of it is not only incorrect, but precisely backwards. Wallace did not abandon natural selection at the human threshold. Rather, it was his peculiarly rigid view of natural selection that led him, quite consistently, to reject it for the human mind. His position never varied—natural selection is the only cause of major evolutionary change. His two debates with Darwin—sexual selection and the origin of human intellect—represent the same argument, not an inconsistent Wallace championing selection in one case and running from it in the other. Wallace’s error on human intellect arose from the inadequacy of his rigid selectionism, not from a failure to apply it. And his argument repays our study today, since its flaw persists as the weak link in many of the most “modern” evolutionary speculations of our current literature. For Wallace’s rigid selectionism is much closer than Darwin’s pluralism to the attitude embodied in our favored theory today, which, ironically in this context, goes by the name of “Neo-Darwinism.”

  Wallace advanced several arguments for the uniqueness of human intellect, but his central claim begins with an extremely uncommon position for his time, one that commands our highest praise in retrospect. Wallace was one of the few nonracists of the nineteenth century. He really believed that all human groups had innately equal capacities of intellect. Wallace defended his decidedly unconventional egalitarianism with two arguments, anatomical and cultural. He claimed, first of all, that the brains of “savages” are neither much smaller nor more poorly organized than our own: “In the brain of the lowest savages, and, as far as we know, of the prehistoric races, we have an organ…little inferior in size and complexity to that of the highest type.” Moreover, since cultural conditioning can integrate the rudest savage into our most courtly life, the rudeness itself must arise from a failure to use existing capacities, not from their absence: “It is latent in the lower races, since under European training native military bands have been formed in many parts of the world, which have been able to perform creditably the best modern music.”

  Of course, in calling Wallace a nonracist, I do not mean to imply that he regarded the cultural practices of all peoples as equal in intrinsic worth. Wallace, like most of his contemporaries, was a cultural chauvinist who did not doubt the evident superiority of European ways. He may have been bullish on the capability of “savages,” but he certainly had a low opinion of their life, as he mistook it: “Our law, our government, and our science continually require us to reason through a variety of complicated phenomena to the expected result. Even our games, such as chess, compel us to exercise all these faculties in a remarkable degree. Compare this with the savage languages, which contain no words for abstract conceptions; the utter want of foresight of the savage man beyond his simplest necessities; his inability to combine, or to compare, or to reason on any general subject that does not immediately appeal to his senses.”

  Hence, Wallace’s dilemma: all “savages,” from our actual ancestors to modern survivors, had brains fully capable of developing and appreciating all the finest subtleties of European art, morality and philosophy; yet they used, in the state of nature, only the tiniest fraction of that capacity in constructing their rudimentary cultures, with impoverished languages and repugnant morality.

  But natural selection can only fashion a feature for immediate use. The brain is vastly overdesigned for what it accomplished in primitive society; thus, natural selection could not have built it:

  A brain one-half larger than that of the gorilla would…fully have sufficed for the limited mental development of the savage; and we must therefore admit that the large brain he actually possesses could never have been solely developed by any of those laws of evolution, whose essence is, that they lead to a degree of organization exactly proportionate to the wants of each species, never beyond those wants…Natural selection could only have endowed savage man with a brain a few degrees superior to that of an ape, whereas he actually possesses one very little inferior to that of a philosopher.

  Wallace did not confine this general argument to abstract intellect, but extended it to all aspects of European “refinement,” to language and music in particular. Consider his views on “the wonderful power, range, flexibility, and sweetness of the musical sounds producible by the human larynx, especially in the female sex.”

  The habits of savages give no indication of how this faculty could have been developed by natural selection, because it is never required or used by them. The singing of savages is a more or less monotonous howling, and the females seldom sing at all. Savages certainly never choose their wives for fine voices, but for rude health, and strength, and physical beauty. Sexual selection could not therefore have developed this wonderful power, which only comes into play among civilized people. It seems as if the organ had been prepared in anticipation of the future progress in man, since it contains latest capacities which are useless to him in his earlier condition.

  Finally, if our higher capacities arose before we used or needed them, then they cannot be the product of natural selection. And, if they originated in anticipation of a future need, then they must be the direct creation of a higher intelligence: “The inference I would draw from this class of phenomena is, that a superior intelligence has guided the development of man in a definite direction, and for a special purpose.” Wallace had rejoined the camp of natural theology and Darwin remonstrated, failed to budge his partner, and finally lamented.

  The fallacy of Wallace’s argument is not a simple unwillingness to extend evolution to humans, but rather the hyper-selectionism that permeated all his evolutionary thought. For if hyper-selectionism is valid—if every part of every creature is fashioned for and only for its immediate use—then Wallace cannot be gainsaid. The earliest Cro-Magnon people, with brains bigger than our own, produced stunning paintings in their caves, but did not write symphonies or build computers. All that we have accomplished since then is the product of cultural evolution based on a brain of unvarying capacity. In Wallace’s view, that brain could not be the product of natural selection, since it always possessed capacities so far in excess of its original function.

  But hyper-selectionism is not valid. It is a caricature of Darwin’s subtler view, and it both ignores and misunderstands the nature of organic form and function. Natural selection may build an organ “for” a specific function or group of functions. But this “purpose” need not fully specify the capacity of that organ. Objects designed for definite purposes can, as a result of their structural complexity, perform many other ta
sks as well. A factory may install a computer only to issue the monthly pay checks, but such a machine can also analyze the election returns or whip anyone’s ass (or at least perpetually tie them) in tic-tack-toe. Our large brains may have originated “for” some set of necessary skills in gathering food, socializing, or whatever; but these skills do not exhaust the limits of what such a complex machine can do. Fortunately for us, those limits include, among other things, an ability to write, from shopping lists for all of us to grand opera for a few. And our larynx may have arisen “for” a limited range of articulated sound needed to coordinate social life. But its physical design permits us to do more with it, from singing in the shower for all to the occasional diva.

  Hyper-selectionism has been with us for a long time in various guises; for it represents the late nineteenth century’s scientific version of the myth of natural harmony—all is for the best in the best of all possible worlds (all structures well designed for a definite purpose in this case). It is, indeed, the vision of foolish Dr. Pangloss, so vividly satirized by Voltaire in Candide—the world is not necessarily good, but it is the best we could possibly have. As the good doctor said in a famous passage that predated Wallace by a century, but captures the essence of what is so deeply wrong with his argument: “Things cannot be other than they are…. Everything is made for the best purpose. Our noses were made to carry spectacles, so we have spectacles. Legs were clearly intended for breeches, and we wear them.” Nor is Panglossianism dead today—not when so many books in the pop literature on human behavior state that we evolved our big brain “for” hunting and then trace all our current ills to limits of thought and emotion supposedly imposed by such a mode of life.

  Ironically then, Wallace’s hyper-selectionism led right back to the basic belief of the creationism that it meant to replace—a faith in the “rightness” of things, a definite place for each object in an integrated whole. As Wallace wrote, quite unfairly, of Darwin:

  He whose teachings were at first stigmatized as degrading or even atheistical, by devoting to the varied phenomena of living things the loving, patient, and reverent study of one who really had faith in the beauty and harmony and perfection of creation, was enabled to bring to light innumerable adaptations, and to prove that the most insignificant parts of the meanest living things had a use and a purpose.

  I do not deny that nature has its harmonies. But structure also has its latent capacities. Built for one thing, it can do others—and in this flexibility lies both the messiness and the hope of our lives.

  5 | Darwin’s Middle Road

  “WE BEGAN TO sail up the narrow strait lamenting,” narrates Odysseus. “For on the one hand lay Scylla, with twelve feet all dangling down; and six necks exceeding long, and on each a hideous head, and therein three rows of teeth set thick and close, full of black death. And on the other mighty Charybdis sucked down the salt sea water. As often as she belched it forth, like a cauldron on a great fire she would seethe up through all her troubled deeps.” Odysseus managed to swerve around Charybdis, but Scylla grabbed six of his finest men and devoured them in his sight—“the most pitiful thing mine eyes have seen of all my travail in searching out the paths of the sea.”

  False lures and dangers often come in pairs in our legends and metaphors—consider the frying pan and the fire, or the devil and the deep blue sea. Prescriptions for avoidance either emphasize a dogged steadiness—the straight and narrow of Christian evangelists—or an averaging between unpleasant alternatives—the golden mean of Aristotle. The idea of steering a course between undesirable extremes emerges as a central prescription for a sensible life.

  The nature of scientific creativity is both a perennial topic of discussion and a prime candidate for seeking a golden mean. The two extreme positions have not been directly competing for allegiance of the unwary. They have, rather, replaced each other sequentially, with one now in the ascendency, the other eclipsed.

  The first—inductivism—held that great scientists are primarily great observers and patient accumulators of information. For new and significant theory, the inductivists claimed, can only arise from a firm foundation of facts. In this architectural view, each fact is a brick in a structure built without blueprints. Any talk or thought about theory (the completed building) is fatuous and premature before the bricks are set. Inductivism once commanded great prestige within science, and even represented an “official” position of sorts, for it touted, however falsely, the utter honesty, complete objectivity, and almost automatic nature of scientific progress towards final and incontrovertible truth.

  Yet, as its critics so rightly claimed, inductivism also depicted science as a heartless, almost inhuman discipline offering no legitimate place to quirkiness, intuition, and all the other subjective attributes adhering to our vernacular notion of genius. Great scientists, the critics claimed, are distinguished more by their powers of hunch and synthesis, than their skill in experiment or observation. The criticisms of inductivism are certainly valid and I welcome its dethroning during the past thirty years as a necessary prelude to better understanding. Yet, in attacking it so strongly, some critics have tried to substitute an alternative equally extreme and unproductive in its emphasis on the essential subjectivity of creative thought. In this “eureka” view, creativity is an ineffable something, accessible only to persons of genius. It arises like a bolt of lightning, unanticipated, unpredictable and unanalyzable—but the bolts strike only a few special people. We ordinary mortals must stand in awe and thanks. (The name refers, of course, to the legendary story of Archimedes running naked through the streets of Syracuse shouting eureka [I have discovered it] when water displaced by his bathing body washed the scales abruptly from his eyes and suggested a method for measuring volumes.)

  I am equally disenchanted by both these opposing extremes. Inductivism reduces genius to dull, rote operations; eurekaism grants it an inaccessible status more in the domain of intrinsic mystery than in a realm where we might understand and learn from it. Might we not marry the good features of each view, and abandon both the elitism of eurekaism and the pedestrian qualities of inductivism. May we not acknowledge the personal and subjective character of creativity, but still comprehend it as a mode of thinking that emphasizes or exaggerates capacities sufficiently common to all of us that we may at least understand if not hope to imitate.

  In the hagiography of science, a few men hold such high positions that all arguments must apply to them if they are to have any validity. Charles Darwin, as the principal saint of evolutionary biology, has therefore been presented both as an inductivist and as a primary example of eurekaism. I will attempt to show that these interpretations are equally inadequate, and that recent scholarship on Darwin’s own odyssey towards the theory of natural selection supports an intermediate position.

  So great was the prestige of inductivism in his own day, that Darwin himself fell under its sway and, as an old man, falsely depicted his youthful accomplishments in its light. In an autobiography, written as a lesson in morality for his children and not intended for publication, he penned some famous lines that misled historians for nearly a hundred years. Describing his path to the theory of natural selection, he claimed: “I worked on true Baconian principles, and without any theory collected facts on a wholesale scale.”

  The inductivist interpretation focuses on Darwin’s five years aboard the Beagle and explains his transition from a student for the ministry to the nemesis of preachers as the result of his keen powers of observation applied to the whole world. Thus, the traditional story goes, Darwin’s eyes opened wider and wider as he saw, in sequence, the bones of giant South American fossil mammals, the turtles and finches of the Galapagos, and the marsupial fauna of Australia. The truth of evolution and its mechanism of natural selection crept up gradually upon him as he sifted facts in a sieve of utter objectivity.

  The inadequacies of this tale are best illustrated by the falsity of its conventional premier example—the so-called Darwin’s
finches of the Galapagos. We now know that although these birds share a recent and common ancestry on the South American mainland, they have radiated into an impressive array of species on the outlying Galapagos. Few terrestrial species manage to cross the wide oceanic barrier between South America and the Galapagos. But the fortunate migrants often find a sparsely inhabited world devoid of the competitors that limit their opportunities on the crowded mainland. Hence, the finches evolved into roles normally occupied by other birds and developed their famous set of adaptations for feeding—seed crushing, insect eating, even grasping and manipulating a cactus needle to dislodge insects from plants. Isolation—both of the islands from the mainland and among the islands themselves—provided an opportunity for separation, independent adaptation, and speciation.

  According to the traditional view, Darwin discovered these finches, correctly inferred their history, and wrote the famous lines in his notebook: “If there is the slightest foundation for these remarks the zoology of Archipelagoes will be worth examining; for such facts would undermine the stability of Species.” But, as with so many heroic tales from Washington’s cherry tree to the piety of Crusaders, hope rather than truth motivates the common reading. Darwin found the finches to be sure. But he didn’t recognize them as variants of a common stock. In fact, he didn’t even record the island of discovery for many of them—some of his labels just read “Galapagos Islands.” So much for his immediate recognition of the role of isolation in the formation of new species. He reconstructed the evolutionary tale only after his return to London, when a British Museum ornithologist correctly identified all the birds as finches.