The Panda’s Thumb (6 page)

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:

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.”

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 tasks 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:

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.

“
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.

The famous quotation from his notebook refers to Galapagos tortoises and to the claim of native inhabitants that they can “at once pronounce from which Island any Tortoise may have been brought” from subtle differences in size and shape of body and scales. This is a statement of different, and much reduced, order from the traditional tale of finches. For the finches are true and separate species—a living example of evolution. The subtle differences among tortoises represent minor geographic variation within a species. It is a jump in reasoning, albeit a valid one as we now know, to argue that such small differences can be amplified to produce a new species. All creationists, after all, acknowledged geographic variation (consider human races), but argued that it could not proceed beyond the rigid limits of a created archetype.

I don't wish to downplay the pivotal influence of the
Beagle
voyage on Darwin's career. It gave him space, freedom and endless time to think in his favored mode of independent self-stimulation. (His ambivalence towards university life, and his middling performance there by conventional standards, reflected his unhappiness with a curriculum of received wisdom.) He writes from South America in 1834: “I have not one clear idea about cleavage, stratification, lines of upheaval. I have no books, which tell me much and what they do I cannot apply to what I see. In consequence I draw my own conclusions, and most gloriously ridiculous ones they are.” The rocks and plants and animals that he saw did provoke him to the crucial attitude of doubt—midwife of all creativity. Sydney, Australia—1836. Darwin wonders why a rational God would create so many marsupials on Australia since nothing about its climate or geography suggests any superiority for pouches: “I had been lying on a sunny bank and was reflecting on the strange character of the animals of this country as compared to the rest of the World. An unbeliever in everything beyond his own reason might exclaim, ‘Surely two distinct Creators must have been at work.'”

Nonetheless, Darwin returned to London without an evolutionary theory. He suspected the truth of evolution, but had no mechanism to explain it. Natural selection did not arise from any direct reading of the
Beagle
's facts, but from two subsequent years of thought and struggle as reflected in a series of remarkable notebooks that have been unearthed and published during the past twenty years. In these notebooks, we see Darwin testing and abandoning a number of theories and pursuing a multitude of false leads—so much for his later claim about recording facts with an empty mind. He read philosophers, poets, and economists, always searching for meaning and insight—so much for the notion that natural selection arose inductively from the
Beagle
's facts. Later, he labelled one notebook as “full of metaphysics on morals.”

Yet if this tortuous path belies the Scylla of inductivism, it has engendered an equally simplistic myth—the Charybdis of eurekaism. In his maddeningly misleading autobiography, Darwin does record a eureka and suggests that natural selection struck him as a sudden, serendipitous flash after more than a year of groping frustration:

Yet, again, the notebooks belie Darwin's later recollections—in this case by their utter failure to record, at the time it happened, any special exultation over his Malthusian insight. He inscribes it as a fairly short and sober entry without a single exclamation point, though he habitually used two or three in moments of excitement. He did not drop everything and reinterpret a confusing world in its light. On the very next day, he wrote an even longer passage on the sexual curiosity of primates.

The theory of natural selection arose neither as a workmanlike induction from nature's facts, nor as a mysterious bolt from Darwin's subconscious, triggered by an accidental reading of Malthus. It emerged instead as the result of a conscious and productive search, proceeding in a ramifying but ordered manner, and utilizing both the facts of natural history and an astonishingly broad range of insights from disparate disciplines far from his own. Darwin trod the middle path between inductivism and eurekaism. His genius is neither pedestrian nor inaccessible.

Darwinian scholarship has exploded since the centennial of the
Origin
in 1959. The publication of Darwin's notebooks and the attention devoted by several scholars to the two crucial years between the
Beagle
's docking and the demoted Malthusian insight has clinched the argument for a “middle path” theory of Darwin's creativity. Two particularly important works focus on the broadest and narrowest scales. Howard E. Gruber's masterful intellectual and psychological biography of this phase in Darwin's life,
Darwin on Man
, traces all the false leads and turning points in Darwin's search. Gruber shows that Darwin was continually proposing, testing, and abandoning hypotheses, and that he never simply collected facts in a blind way. He began with a fanciful theory involving the idea that new species arise with a prefixed life span, and worked his way gradually, if fitfully, towards an idea of extinction by competition in a world of struggle. He recorded no exultation upon reading Malthus, because the jigsaw puzzle was only missing a piece or two at the time.

Silvan S. Schweber has reconstructed, in detail as minute as the record will allow, Darwin's activities during the few weeks before Malthus (The Origin of the
Origin
Revisited,
Journal of the History of Biology
, 1977). He argues that the final pieces arose not from new facts in natural history, but from Darwin's intellectual wanderings in distant fields. In particular, he read a long review of social scientist and philosopher Auguste Comte's most famous work, the
Cours de philosophie positive
. He was particularly struck by Comte's insistence that a proper theory be predictive and at least potentially quantitative. He then turned to Dugald Stewart's
On the Life and Writing of Adam Smith
, and imbibed the basic belief of the Scottish economists that theories of overall social structure must begin by analyzing the unconstrained actions of individuals. (Natural selection is, above all, a theory about the struggle of individual organisms for success in reproduction.) Then, searching for quantification, he read a lengthy analysis of work by the most famous statistician of his time—the Belgian Adolphe Quetelet. In the review of Quetelet, he found, among other things, a forceful statement of Malthus's quantitative claim—that population would grow geometrically and food supplies only arithmetically, thus guaranteeing an intense struggle for existence. In fact, Darwin had read the Malthusian statement several times before; but only now was he prepared to appreciate its significance. Thus, he did not turn to Malthus by accident, and he already knew what it contained. His “amusement,” we must assume, consisted only in a desire to read in its original formulation the familiar statement that had so impressed him in Quetelet's secondary account.