

“Long before the birth of the modern American environmental movement, naturalists recognized the problem of human-caused extinction. Barrow offers a concise but richly detailed chronological history beginning with Thomas Jefferson and his interest in the fossils of woolly mammoths being discovered in the West.… Essential for anyone interested in our environmental past or concerned about our future.”—Library Journal, starred review “I fear we’ll have good reason to think more and more about extinction as this century progresses, and this fascinating (and rueful) history provides a good base for that reflection.”—Bill McKibben

An excerpt from Nature’s Ghosts Confronting Extinction from the Age of Jefferson

to the Age of Ecology Mark V. Barrow, Jr. The Discovery of Extinction Such is the economy of nature, that no instance can be produced of her having permitted any one race of her animals to become extinct; or her having formed any link in her great work so weak as to be broken.

—Thomas Jefferson, 1784 Jefferson’s Dilemma At the height of the American Revolution, while the outcome of the rebellion against Great Britain remained uncertain, Thomas Jefferson grappled with the problem of fossils. The specific context of his engagement with this thorny issue was a manuscript that he began sometime in the summer or early autumn of 1780. At the time the thirty-seven-year-old governor of Virginia and author of the Declaration of Independence already enjoyed a considerable reputation for accomplishment in the political sphere. Less well known to his contemporaries was his keen interest in science. Jefferson was an inveterate reader of scientific treatises, a zealous recorder of natural phenomena, and an eager correspondent with others who shared his enthusiasm. He would later reflect on his longstanding curiosity about the natural world by declaring that “Science is my passion, politics my duty.” In 1780, when the secretary to the French minister in Philadelphia, François Marbois, circulated a detailed questionnaire regarding the political and natural history of Virginia, Jefferson seized the opportunity to organize his abundant notes. Faced with a long series of personal and political crises—including the death of his daughter, the prolonged illness of his wife, a nasty injury sustained in a fall from his horse, forced retreat first from the state capital in Richmond and then from his estate in Monticello, and accusations that he had engaged in dishonorable conduct during the period of British occupation—Jefferson endured some of the darkest days of his entire life. Yet, at Popular Forest, his beloved rural retreat nestled in the Blue Ridge Mountains, he found solace in the hours devoted to fulfilling Marbois’s request. By the time he returned to Monticello in August 1781, he was nearly finished drafting the manuscript. The resulting publication, issued three years lateras Notes on the State of Virginia, proved the only book Jefferson would publish during his lifetime. It is now widely considered a classic, “one of America’s first permanent literary and intellectual landmarks.”

Jefferson with Declaration of Independence and scientific instruments, 1801. Engraving by Cornelius Tiebout. In addition to his considerable accomplishment in the political sphere, Jefferson was also a skilled naturalist who made early, important contributions to the field of paleontology. Courtesy of Prints and Photographs Division, Library of Congress, LC-USZ62-75384. Although he had long been fascinated with science, Notes on the State of Virginia signaled the beginning of Jefferson’s active interest in fossil vertebrates. Interspersed among his discussion of political philosophy, his ideas about religious freedom, and his famous condemnation of slavery, Jefferson meticulously cataloged the natural resources of his home state and the surrounding region. The first animal he described was also the one to which he devoted the most attention: “the Mammoth, or big buffalo,” a creature he judged to be “six times the size of an elephant,” which it seemed to resemble. What little was known about this “incognitum” (as it was often referred to at the time) came from tales about the beast that Indians had passed down through the generations and from fossilized remains that had been uncovered in America beginning in the early eighteenth century. Since that initial discovery, the creature’s teeth and bones had become highly sought after additions to institutional museums and private cabinets of curiosity on both sides of the Atlantic. In America, for example, not only Jefferson, but also George Washington and Benjamin Franklin owned prized specimens of the grinders from these mysterious beasts. For Jefferson, the incognitum proved not only an intrinsically fascinating creature, it also provided ammunition in an ongoing campaign to refute the theory of one of Europe’s most renowned naturalist during the second half of the eighteenth century, Georges Louise Leclerc, Comte de Buffon, who was Intendant of the Jardin des Plantes and Keeper of the Royal Cabinet of Natural History in Paris. In his best-selling, thirty-six-volume Histoire naturelle, générale et particulière (1749–89), Buffon argued that the New World’s generally cool and moist environment had forced its native inhabitants to degenerate over time, rendering them punier, less vigorous, and less fertile than their Old World counterparts. Stung by the assault on his homeland and its people, Jefferson felt compelled to respond. In a discussion with explicitly nationalistic overtones, he asserted the morality, fecundity, and intelligence of America’s aboriginal inhabitants. He also produced two tables showing that the mammals native to the land of his birth fared quite well when their weight or overall numbers were compared with those in Europe. The bones of the mysterious “incognitum,” the “largest of all terrestrial beings,” however, offered Jefferson with the strongest potential evidence in his bid to refute Buffon’s troubling theory. The problem was Jefferson could not prove that the prodigious beast still roamed the earth. For the remainder of his life, Jefferson vigorously pursued the American incognitum and other quadrupeds whose fossilized remains were periodically uncovered across North America. He not only personally financed numerous expeditions to retrieve fossil remains but also encouraged others to follow his lead. For example, on December 19, 1781, the day before he sent his completed Virginia manuscript to the French consul in Philadelphia, Jefferson wrote to General George Rogers Clark, an old friend, Abermarle County native, and the commanding officer of the Army of the West. Jefferson’s note, delivered by none other than Daniel Boone, asked Clark to venture to Big Bone Lick, Kentucky, on the banks of the Ohio River, to retrieve bones of the American incognitum. The threat of Indian attack kept Clark away from the area, so a year later Jefferson repeated his request, declaring: “A specimen of each of the several species of bones now to be found is to be the most desirable object in Natural History, and there is no expense of package or safe transportation which I will not gladly reimburse to procure them safely.” Despite his strict constructionist principles, as president of the United States Jefferson provided federal support so the Philadelphia artist, naturalist, and museum owner Charles Willson Peale could unearth a complete skeleton of the incognitum from a soggy marl pit along the Hudson River. With the bones he found, Peale mounted and displayed one of the earliest virtually intact fossil skeletons ever to be reconstructed, an outcome that thrilled Jefferson. Jefferson enjoyed collecting fossil vertebrates—and proudly displayed them at Monticello—but he was also quite interested in furthering scientific understanding of these mysterious creatures. In keeping with that goal, he freely placed prized specimens in the hands of museums at home and abroad. The bones of the American incognitum that he sent to the prestigious National Museum of Natural History in Paris, for example, proved useful to French naturalists working in the nascent fields of paleontology and comparative anatomy. He even published a paper of his own describing a new species of large fossil mammal, which he dubbed the megalonyx, based on bones recovered by workers digging saltpeter from a cave in Greenbrier County, Virginia (now West Virginia). Although he thought the megalonyx was a fearsome gigantic clawed beast that dwarfed the African lion, thereby providing additional evidence against Buffon’s theory of degeneracy, it later turned out to be a massive sloth that still bears his name, Megalonyx jeffersoni. Although it strikes the modern reader as rather odd, Jefferson also firmly believed these creatures still survived somewhere in the unexplored regions of the continent. In his table of American and European mammals found in Notes on the State of Virginia, Jefferson listed the mammoth first. In defense of this decision he wrote: “It may be asked, why I insert the Mammoth as if it still existed? It may be asked in return, why I should omit it, as if it did not exist? Such is the œconomy of nature, that no instance can be produced of her having permitted any one race of her animals to become extinct; of her having formed any link in her great work so weak as to be broken.” Beyond this basic philosophical objection to extinction was the “traditionary testimony of the Indians, that this animal still existed in the northern and western parts of America,” regions that remained “in their aboriginal state, unexplored and undisturbed.” To Jefferson and many of his contemporaries, the very idea of species extinction seemed anathema. Intellectuals of his day recognized that settlement often resulted in the local extermination of wildlife. But the complete disappearance of a species was another matter altogether. The loss of any organism across its entire range implied an unacceptable imperfection in God’s creation, while violating deep-seated assumptions about the balance of nature and the great chain of being that proved central to Western understandings of how that creation was ordered. In the hope that living examples of these beasts might still be found wandering somewhere in the unexplored regions of North America, Jefferson urged the explorers Meriwether Lewis and William Clark to keep a sharp lookout out for species animals “deemed to be rare or extinct,” like the American incognitum, during their famous western exploring expedition. The Corps of Discovery found a host of new plant and animal species during their arduous two-year journey, but they encountered no lumbering elephants. While Jefferson’s doubts about the possibility of extinction remained commonplace at the time he penned Notes on the State of Virginia, by the time of his death in 1826, most naturalists on both sides of the Atlantic had experienced a sea change in their ideas on the subject. Central to this transformation was the work of the brash young French naturalist, Georges Cuvier. With access to specimens provided by a transatlantic fossil network and training from prominent German anatomists, Cuvier deployed the principles of comparative anatomy to offer convincing evidence that extinction had been a regular part of the earth’s history. Cuvier was the first naturalist to clearly distinguished between the two living species of elephant and two kinds of extinct fossil elephant, the mammoth and the mastodon, the latter of which he clearly differentiated and named in 1806. During the first several decades of the nineteenth century, he went on to describe a virtual zoo of lost creatures, thereby laying the foundations for modern paleontology. Within a surprisingly short period of time, the reality of extinction became central to most educated Westerners’ understanding of the earth’s history. Later in life, even Jefferson himself privately admitted that some species might have been lost. Yet, as we shall see later, some of the ideas that had led him and most other naturalists to deny the reality of extinction—for example, the notion of plentitude that proved central to the great chain of being and the idea that nature was finely balanced—remained important to thinking about the natural world long after the possibility of extinction became widely accepted. Providential Natural History and the Order of Nature Jefferson and most of his contemporaries were certain that the natural world was orderly, static, and new. Most importantly, and one of the beliefs undergirding these convictions, they also firmly believed that it was the product of a divine mind. One way to understand that mind, and at the same time to ensure that science and religion, reason and faith remained firmly reconciled, was a set of practices and beliefs known as natural theology. As with so many foundational concepts in the Western world, the basic idea of natural theology—that careful scrutiny of the natural world revealed attributes of its creator—dates back to the ancient Greeks. During the Middle Ages, Aquinas and the scholastics labored to show how reason melded harmoniously with faith to demonstrate the existence and attributes of a Christian god. At end of the seventeenth and the beginning of the eighteenth centuries, these ideas found full expression when the famed British naturalist John Ray published Wisdom of God Manifested in the Works of the Creation (1691). Ray’s influential, widely reprinted book combined observations and specific arguments made by previous authors with his own considerable knowledge of flora, fauna, and systematics. Ray leaned heavily on a line of reasoning central to the natural theology of his day: the argument from design. This argument held that since the obvious order and complexity of the world could not have possibly emerged from nature itself, an intelligent designer must have imposed it. Just as human-made buildings and machines “do necessarily infer the being and operation of some intelligent Architect or Engineer,” Ray argued, “why shall not also the Works of Nature, that Grandeur and Magnificence, that excellent contrivance for Beauty, Order, Use, &c., which is observable in them, wherein they do as much transcend the Effects of human Art as infinite Power and Wisdom exceeds finite, infer the existence of an Omnipotent and All-wise Creator?” Proponents of the argument from design applied it on multiple scales, ranging from individual organs (like the eye or the human hand) to particular species (like the honey bee or the beaver) to the larger patterns of relationship between species (e.g., the adaptations of prey to escape predation). In all cases, though, structure seemed to be perfectly adapted to function, while the order and complexity of nature was thought to reveal the wisdom, power, and beneficence of God. When it came to conceptualizing the specific patterns of relationship between species, however, many possibilities presented themselves. One deeply entrenched way of thinking about that order was the chain of being or scala naturae, the idea that the diversity of the natural world could best be understood as a long chain containing every possible kind of organism in a linear, continuous series. In its most expansive form, the great chain of being was thought to encompass not just living organisms, but all kinds of being from “nothing to the Deity.” The idea has its roots in the Platonic view that the world is full and all possible kinds of things exist (the notion of plentitude) and the Aristotelian belief that all creatures could be lined up in a hierarchical series, with no gaps between them (the notions of continuity and gradation). Well into the eighteenth century, naturalists struggled to reconcile the expanding, increasingly detailed observations of known organisms into a single, hierarchical, continuous series. The idea of the chain of being proved central, for example, to the renowned Swedish naturalist Carl Linnaeus, who not only introduced the binomial system of scientific nomenclature but also developed widely adopted systems of botanical and zoological classification. Linnaeus once wrote that “the closer we get to know the creatures around us, the clearer is the understanding we obtain of the chain of nature, and its harmony and system, according to which all things appear to have been created.” Similarly, in the preliminary discourse to his Histoire naturelle, Buffon argued that if man placed himself at the “head of all created beings, he would see with astonishment that one could descend by almost imperceptible degrees from the most perfect creature to the most shapeless matter, from the most organized animal to the crudest mineral; he would recognize that these imperceptible nuances were the greatest work of Nature.” Nor was the idea of the great chain of being confined to biological circles; rather, it remained the common cultural heritage of most educated Europeans and Americans until the end of the eighteenth century. The pervasive idea of the great chain of being had strong implications for how the notion of extinction was received. For if God had created every conceivable form and no discernable gaps existed between them, then the loss of any creature threatened to bring down the entire edifice. The British poet Alexander Pope simultaneously celebrated the chain of being while expressing concern about the implication of extinction in his Essay on Man (1733–34): Vast Chain of Being! which from God began,

Natures aetherial, human, angel, man,

Beast, bird, fish, insect, what no eye can see,

No glass can reach; from Infinite to thee,

From thee to nothing.—On superior pow’rs

Were we to press, inferior might on ours:

Or in the full creation leave a void,

Where, one step broken, the great scale’s destroyed:

From Nature’s chain whatever link you strike,

Tenth or ten thousandth, breaks the chain alike. The great chain of being offered one widely adopted model for thinking about the apparent order of the world; the notion that nature was balanced provided a different (though complimentary) way of conceptualizing that order. Not surprisingly, the idea that nature exists in some kind of overall balance also has deep roots in antiquity. Indeed, as the historian of ecology Frank Egerton has argued, “In one way or another a balance-of-nature concept is part of most cosmologies.” Early discussions of the idea tended to be vague and general, but by the end of the seventeenth and the beginning of the eighteenth centuries, naturalists like Ray began to marshal specific biological evidence—like the existence of finely tuned predator-prey relationships—to show how God ensured nature’s balance. Perhaps not surprisingly, the inveterate namer and classifier Linnaeus first provided a title for the balance-of-nature concept, while at the same time laying down the early foundations for the science of ecology. In 1749, he published an influential essay, “The Oeconomy of Nature,” which declared that everything in the universe was “chained together” and that this interconnection demonstrated the “infinite wisdom of the Creator”: “To perpetuate the established course of nature in a continued series, the divine wisdom has thought fit, that all living creatures should constantly be employed in producing individuals, that all natural things should contribute and lend a helping hand toward preserving every species, and lastly that the death and destruction of one thing should always be subservient to the restitution of another.” We see hints of the chain of being in this statement, which appeared in the introduction to the essay, but here Linnaeus is much more interested in the functional relationship between organisms in a given environment than a simple recounting of the series of creation. Central to this functional relationship is the observation that each animal not only feeds upon its own distinct prey but also is preyed upon by other species. Linnaeus offered several examples of this general phenomenon, including one that included multiple layers of predation: “Thus the tree-louse lives upon plants. The fly called musca aphidivora lives upon the tree-louse. The hornet and wasp fly upon musca aphidivora. The dragon fly upon the hornet and wasp fly. The spider on the dragon fly. The small birds upon the spider. And lastly, the hawk kind on the small birds.” In effect, what Linnaeus did here was delineate the ecological concept of the food chain, though naturalists would not adopt that precise name until nearly two centuries later. Linnaeus also enumerated other patterns within the “economy of nature.” Predators have fewer offspring, are less numerous in overall population size, and tend to live shorter lives than their prey. Each species exists within its own geographic range and eats a certain kind of food. Even particularly voracious “wild beasts and hawks” cannot “destroy a whole species.” Rather, Providence has created an order that continually ensures a “just proportion among all the species,” an order in which the complete loss of any species is inconceivable. Linnaeus believed that ultimately this entire interconnected world had been made for the sake of humans—both to provide the things they need to survive and to offer a tangible reminder of God’s power and glory. Thus the wide acceptance of the chain of being and notions of a balanced nature both contributed to a generally static view of the world. Species could not go out of existence or come into being without fundamentally threatening that natural order. Ray, for example, remained unequivocal on this point: “The Number of true species in nature is fixed and limited, and as we may reasonably believe, constant and unchangeable from the first creation to the present day.” By the second half of the eighteenth century, some naturalists became more receptive to the possibility of limited change in organic nature. Linnaeus and his students, for example, toyed with the idea that hybridization might produce new species, while Buffon argued that the diversity of the natural world evident in his day was the result of the degeneration of a discrete number of basic forms. But most naturalists refused to entertain the possibility of dramatic change in organic nature, and the complete loss of any species remained extremely problematic. Scientists and other intellectuals in the West not only saw the world as static; they also believed it was relatively young. Scriptural tradition played a central role in this assessment; the Bible recorded that the world had been created in six days, and it provided a written account of the early generations of patriarchs. In the seventeenth century, Archbishop James Ussher tried to nail down the exact date of creation by tracing these lineages while cross-referencing the people and events named in the Bible to the (still sketchy) historical record available at the time. Ussher’s estimate—that the world began on the nightfall preceding Sunday, October 23, 4004, BC—gained further credence when church authorities incorporated it into annotated editions of the influential King James Bible translation. While not everyone accepted Ussher’s overly exact calculation, until the end of the eighteenth century, most educated Westerners seemed to embrace the notion that earth history and human history were roughly coeval and that the age of the earth was scarcely a few thousand years old. The Problem of Fossils The discovery of fossils challenged firmly entrenched ideas about the order, stability, and age of the earth. Fossils—which we now define as the preserved remains of once living beings—had long been noticed, if not accurately identified. In a fascinating recent book, the folklorist Adrienne Mayor has documented the deep interest in fossils in the ancient world, where the “bones of gigantic beings were treasured as relics of the mythic past and displayed as natural wonders in temples and other public places.” She argues that many of the mythical beasts from this period—the griffin, the centaur, and others—had their origins in fossil skeletons that were widely collected, measured, and displayed throughout the lands known to the Greeks and Romans. That knowledge about fossil beings seems to have been largely forgotten, though, until the Renaissance, when the science of paleontology first began to stir. By then, the term “fossil” denoted any distinctive object found below the earth or lying on its surface. It thus referred not only to fossils in the modern sense, but also to mineral ores, crystals, and rocks of all sorts. During the sixteenth century, the systematic study of fossils first took off when Conrad Gesner and other scholars began amassing large collections of these curious stones, producing illustrated publications describing them, and corresponding with individuals who shared their interests. These fossil objects tended to be interpreted within either Neoplatonic frameworks—which saw a correspondence between the hidden and visible worlds while positing a pervasive molding force or “plastic virtue” responsible for that correspondence—and Aristotelian frameworks that saw simple fossils as spontaneously generating and more complex ones as growing from a specific “seed” within the earth. Whichever explanation sixteenth-century naturalists adopted for the origin of fossils, they failed to show a particular interest in discriminating between organic and inorganic objects. And neither explanation for their origin raised the touchy issue of extinction. During the seventeenth century, naturalists not only began to take more interest in the resemblance between fossil forms and living forms, but also began to call those with a significant likeness to living beings “organized fossils” or “extraneous fossils.” As historian of science Martin Rudwick notes in his pioneering study on the origins of paleontology, interpreting the meaning of these apparently organic fossil forms posed difficult challenges for early modern naturalists. While it was relatively easy to make the connection between so-called tongue stones and the teeth of living sharks, for example, other fossils presented difficulties because of confusing modes of preservation or a lack of familiarity with the organisms from which they had originated. Even in the case of fossils that clearly resembled living species, explaining their position (e.g., shells embedded high on mountaintops) proved difficult without adequate models to explain geological change. And in cases of fossils that appeared to be organic but did not seem to have living analogs, like ammonites, the specter of extinction haunted naturalists because it challenged deeply held notions about plentitude, the balance of nature, and the age of the earth. One scholar who struggled mightily with the problem of fossils in the late seventeenth century was John Ray. Ray was too accomplished a naturalist not to appreciate the strong resemblance between many fossil and living forms; moreover, his commitment to natural theology suggested to him that nothing in nature had been done in vain. He also benefited from the earlier publications of Nicolas Steno and Robert Hooke, who had argued convincingly for the organic origins of certain fossils in the 1660s and 1670s by using examples of remains whose form, composition, and position were relatively easy to account for. Following a tour on the Continent, Ray completed an essay on the problem of fossils in which he called the hypothesis of organic origin the most “probable opinion,” but one which he nonetheless found troubling. First, the morphological differences between living and fossil species were enough to suggest that the latter were the remains of species that were extinct, a conclusion that flew in the face of some of Ray’s most cherished assumptions. And second, the appearance of fossils in highly elevated areas, like the Alps, was difficult to explain using ideas of mountain upheaval as generally understood at the time, or by invoking the Great Flood, which soon became a common means of addressing this particular issue. As Rudwick points out, “the only way out of the dilemma was to argue that fossil species might not really be extinct at all” a conclusion that he terms “perfectly justifiable” at the time. Most of the organisms in dispute were marine animals, which were little studied, especially those forms inhabiting remote areas. For the specific case Ray mentioned, fossil stalked crinoids, Ray’s sense that it was too early to write off the species as lost gained vindication fifty years after his death by the discovery of living examples in the West Indies. The problem of fossils continued to challenge naturalists throughout the eighteenth century. The general confusion they provoked is amply illustrated in an episode from the early part of that century, when purported fossil remains became the center of a notorious scientific hoax. Johann Bartholomew Adam Beringer, senior professor and dean of the faculty of medicine at the University of Würzberg, was a well-known collector of and expert on fossils. In May 1725, he hired three young men to excavate a promising site, a hill about a mile outside the town where the university was located. Over the next six months, his assistants dug up hundreds of fossil mollusks and small figured fossils from this site. But there was something odd about these particular stones: they featured a dazzling variety of forms, including a radiant sun with a human face, stars and comets, lizards, fishes, bees, frogs, and even Jehovah’s name in Hebrew! Beringer was suspicious, as he should have been. Nonetheless, a year after he began trying to make sense of the bizarre stones, he published an illustrated book featuring more than two hundred specimens from this site. After considering and rejecting various explanations for the fossils, he ultimately concluded that they had been created by “the Author of Nature” but were not the remains of any living creature. Only later did he discover that he had been the victim of an elaborate hoax perpetrated by two jealous colleagues. Nonorganic explanations for fossils died out slowly during this period, and, if Rudwick is correct, the humiliation that Beringer suffered may have played a small role in their decline. Yet, until the end of the eighteenth century, relatively few naturalists seemed willing to entertain the idea that fossils represented the relicts of extinct species. Linnaeus, for example, wrote of the fossil Anomiae: “the animals which inhabited these ‘wild mussels,’ as well as unaltered shells, are nowadays unknown to us … , nor do we know what in the world may have become of them. Still, we shall never believe that a species has entirely perished from the earth.” Some naturalists at the time did begin arguing that the age of the earth was much greater than the generally accepted date of only several thousand years old. Based on estimates of the earth’s cooling rate and his knowledge of fossils and sedimentation rates, in the late 1770s, Buffon argued that the world was more than seventy thousand years old, while privately speculating that the deposition of known geological strata would have required at least 10 million years. Buffon thus became one of the first major Western thinkers to appreciate the concept of “deep time,” a wonderfully evocative phrase coined by the twentieth-century American writer John McPhee. The Scottish geologist James Hutton went even further in his landmark book Theory of the Earth (1795). There he argued that much of the earth’s surface consisted of the relicts of sea animals that had been deposited on the ocean floor, consolidated into strata, and then pushed upward by the heat of the earth. All this took so much time, Hutton argued, that when it came to estimating the age of the earth, there was “no vestige of a beginning,—no prospect of an end.” Even with these and other expansions in the earth’s time scale, though, resistance to the idea of extinction remained solid. As Rudwick summarizes the situation at the end of the eighteenth century: “Whether any species had truly been ‘lost’ from the world thus remained a question as uncertain and debatable at the end of Buffon’s life as it had been nearly a century earlier at the end of Ray’s. Many groups of fossils, such as ammonites and belemnites, were now recognized beyond all doubt as organic remains differing radically from any known living animals; but it could still be asserted with good reason that they might be living in deep water or in some remote part of the world.” The discovery and careful examination of large fossil mammals would soon present insurmountable obstacles to that claim.

