The Tangled Tree

by David Quammen

  Again, this didn’t imply any heretical ideas about origins. Augier was no evolutionist before his time. His natural order wasn’t meant to suggest that all plants had descended from common ancestors by some sort of material process of transformation. God was their maker, shaping the varied forms individually: “It appears, and one can hardly doubt it, that the Creator, when making flowers, followed certain proportions and progressions in the number of their different parts.” Augier’s contribution, as he saw it, was discovering those proportions and progressions—design principles that had satisfied the Deity’s neat sense of pattern—and using them after the fact to organize botanical knowledge into a tidy system.

  Augier wasn’t the first naturalist to hanker for a natural order of nature’s diversity. Aristotle had classified animals as “bloodless” and “blooded.” In the first century of our era a Greek physician named Dioscorides, attached to the Roman army, gathered lore on more than five hundred kinds of plants, arranging them in a compendium mainly on the basis of their medicinal, edible, and perfumatory uses. That book, in various reprints and translations, served as a trusted botany text for the next fifteen hundred years. Toward the end of its run, around the time of the Renaissance, as people traveled more widely and paid closer attention to the empirical details of nature, old Dioscorides gave way to newer illustrated herbals. These were essentially field guides to botany, graced with better illustrations based on improvements in drawing and woodcut techniques, but still organized for convenience of use, not natural order. In the sixteenth century, Leonhart Fuchs produced one of those books, an herbal cataloging hundreds of plants, beautifully illustrated and arranged in alphabetical order. Two centuries later, the great systematizer Carl Linnaeus described a genus of plants with purplish red flowers, naming it Fuchsia in honor of Leonhart Fuchs (and hence we got also the color, fuchsia). Linnaeus himself, a Swede who traveled widely as a young man and then took up a professorial life in Uppsala, emerged from this herbalist tradition but went beyond it.

  Augier’s Arbre Botanique, 1801.

  Linnaeus’s Systema Naturae, as first published in 1735, was a unique and peculiar thing: a big folio volume of barely more than a dozen pages, like a coffee-table atlas, in which he outlined a classification system for all the members of what he considered the three kingdoms of nature: plants, animals, and minerals. Notwithstanding the inclusion of minerals, what matters to us is how Linnaeus viewed the kingdoms of life.

  His treatment of animals, presented on one double-page spread, was organized into six columns, each topped with a name for one of his classes: Quadrupedia, Aves, Amphibia, Pisces, Insecta, Vermes. Quadrupedia was divided into several four-limbed orders, including Anthropomorpha (mainly primates), Ferae (doggish forms such as wolves and foxes, plus cat forms such as lions and leopards, in addition to bears), and others. His Amphibia encompassed reptiles as well as amphibians, and his Vermes was a catchall group containing not just worms, leeches, and flukes but also slugs, sea cucumbers, starfish, barnacles, and other sea animals. He divided each order further into genera (with some recognizable names such as Leo, Ursus, Hippopotamus, and Homo), and each genus into species. Apart from the six classes, Linnaeus also gave a half column to what he called Paradoxa: a wild-card assemblage of mythic chimeras and befuddling but real creatures, including the unicorn, the satyr, the phoenix, the dragon, and a certain giant tadpole (Pseudis paradoxa, under its modern label) that, strangely, paradoxically, shrinks during metamorphosis into a much smaller frog. Across the top of the chart ran large letters: CAROLI LINNAEI REGNUM ANIMALE. His animal kingdom. It was a provisional effort, grand in scope, integrated, but not especially original, to make sense of faunal diversity based on what was known and believed at the time. Then again, animals weren’t Linnaeus’s specialty.

  Plants were. His classification of the vegetable kingdom was more innovative, more comprehensive, and more orderly. It became known as the “sexual system” because he recognized that flowers are sexual structures, and he used their male and female organs—their stamens and pistils, those delicate little stems sticking up to present and receive pollen—for characterizing his groups. Linnaeus defined twenty-three classes, into which he placed all the flowering plants, based on the number, size, and arrangement of their stamens. Then he broke each class into orders, based on their pistils. To the classes, he gave names such as Monandria, Diandria, and Triandria (one husband, two husbands, three husbands), and, within each class, ordinal names such as Monogynia, Digynia, and Tryginia (numbers of wives, yes, you get the idea), thereby evoking all sorts of polygamous and polyandrous ménages that must have caused lewd smirks and disapproving scowls among his contemporaries. A plant of the Monogynia order within the Tetrandria class, for instance: one wife with four husbands. Linnaeus himself seems to have enjoyed the sexy subtext. And it didn’t prevent his botanical schema from becoming the accepted system of plant classification throughout Europe.

  Our man Augustin Augier, coming along a half century later with his botanical tree of classification, seems to have seen himself challenging Linnaeus’s overly neat sexual system. “Stamen number is a striking character,” Augier conceded, but “not when it comes to the examination of plants”—that is, not always unambiguous and therefore not reliable as a basis for organizing the great jumble of botanical life. He nodded respectfully to Linnaeus—also to the French botanist Joseph Pitton de Tournefort, who had sorted plants into roughly seven hundred genera based on their flowers, their fruits, and other bits of their anatomy—and offered his own system, using multiple characters for different levels of sorting and to resolve the ambiguities and fine gradations. “This figure, which I call a botanical tree, shows the agreements which the different series of plants maintain amongst each other, although detaching themselves from the trunk; just as a genealogical tree shows the order in which different branches of the same family came from the stem to which they owe their origin.” All discrete, yet all connected: bits of the same tree.

  But they weren’t connected, in Augier’s mind, by descent from shared ancestors. Despite the hint he gave to himself in his language about family trees—all branches divergent from “the stem to which they owe their origin”—there is no evidence in Augier’s writing or his tree figure that he had embraced, or even imagined, the idea of evolution.

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  That idea was coming soon, and, with its arrival, the tree of life would change meaning. The change was drastic, soul shaking to many people who lived through it, because it reflected a challenge to faith, and it met strong resistance. Jean-Baptiste Lamarck, France’s great early evolutionist, and Edward Hitchcock, an American who prided himself a “Christian geologist,” are the two scientists whose works—and whose graphic illustrations—best reflect how tree thinking shifted during the decades before Darwin unveiled his theory of evolution.

  Lamarck was a protean figure: a soldier from a family of soldiering minor nobility who transformed himself into a botanist, then into a professor of zoology at the Muséum National d’Histoire Naturelle in Paris, to which he was appointed in 1793, on the eve of the Reign of Terror. His title at the museum put him in charge “of insects, of worms, and microscopic animals,” three categories of life he had never studied, but he adapted fast, and even invented the word invertebrates to cover them. He abandoned plants and studied his invertebrates through the grimmest days of the French Revolution, earning a measly salary but at least keeping his head, as other scientists such as Antoine-Laurent Lavoisier went to the guillotine. Lamarck had probably helped his standing among the revolutionaries back in 1790 while employed at what was then the Jardin du Roi, when he urged dropping the royal label and renaming that institution the Jardin des Plantes. Clearly, he had good political instincts. He held the conventional view of species—that they were fixed forever and created by God—until 1797, but then his views changed, possibly as a result of his study of fossil and living mollusks, which seemed to show patterns of gradual transformation. He came ou
t as an evolutionist on May 11, 1800, in his first lecture for the year’s course on invertebrates. After that, he published three major works on evolutionary zoology, the most influential being his Philosophie Zoologique in 1809.

  Lamarck outlived four wives and three of his seven children, living beyond the revolution, through the Napoleonic era and most of the Bourbon Restoration, a handsome man with a downturned mouth, balding slowly across his pate, blind for his final ten years, his faithful daughter, Cornelie, giving her life to him and reading him French novels. He died at eighty-five and was eulogized by important colleagues such as Geoffroy St. Hilaire, after which things didn’t go so well: his remains were interred at the Montparnasse Cemetery in a common trench, not a permanent individual plot, and because such burial trenches were regularly recycled, his bones may have ended up in the Paris catacombs, along with those of thousands of paupers and other neglected folk. There was no Lamarck grave to visit. He became, according to one biographer, rather quickly “forgotten and unknown.” His fame would return, if not immediately, but still it was a cold finish for the world’s first serious evolutionary theorist.

  Lamarck nowadays is commonly associated with what his name came to represent: Lamarckism, an easy but imprecise label for the idea of the inheritance of acquired characteristics. Many people are vaguely aware of him as a predecessor to Darwin; he is seen as a forerunner whose theory was provocative but wrong, refuted by later evidence because it depended, as Darwin’s did not, on that illusory notion of acquired traits being heritable. (The real facts aren’t so simple. For instance, Darwin himself included the inheritance of acquired characteristics as a force in evolution, under the label “use and disuse.”) The most familiar example of such inherited adjustments, which Lamarck himself offered, is the giraffe. The proto-giraffe on the dry plains of Africa stretches to reach high foliage, its neck lengthens (supposedly) from the effort, its front legs lengthen too, and therefore (again supposedly) its offspring are born with longer necks and front legs. Lamarckism, in that cartoonish form, has been easy to despise but harder to kill off entirely.

  Lamarck’s tree of dots, 1809.

  It came back into fashion during the late nineteenth century, when the general idea of evolution gained acceptance but the crucial details of Darwin’s particular theory, offering natural selection as the primary mechanism, were widely rejected. Natural selection just seemed too mechanistic, too stark and unguided, and many evolutionists found it unpalatable. This situation went on for decades—the world accepting Darwin’s idea of evolution but not his explanation of how it occurs—though only historians remember that now. Lamarckism became neo-Lamarckism and seemed a less nihilistic alternative. It has continued to linger as a dubious but ineradicable notion—embodied in that single tenet, the inheritance of acquired characteristics—enjoying small surges of reconsideration even down to the present day.

  But that single tenet was never Lamarck in totality. He had other ideas, some even worse. He believed in spontaneous generation. He disbelieved in extinction, at least as a natural process. He argued that “subtle fluids,” surging through the bodies of living creatures, helped reshape them adaptively.

  In one of his earlier botanical works, before the shift to animals and the epiphany about evolution, Lamarck had arranged plants in what he called “the true order of gradation”: from least perfect and complete to most, ascending along an old-fashioned ladder of life. He matched that with a separate ladder for animals, a “counterpart” arrangement, showing an ascending series of forms: from worms, through insects, through fish and amphibians and birds, to mammals. Neither of those ladders hinted at divergence from common ancestors or transformation. But in the 1809 book Philosophie Zoologique, he included a different sort of figure, subtle yet dramatic, depicting animal diversity. It was a branched diagram, descending down the page, with major animal groups connected by dotted lines, like one of those connect-the-dots games for kids on the paper placemats at a pancake house. Connect the dots and discover that the secret shape is . . . an airplane! Or . . . an elephant! Or . . . George Washington’s head! In Lamarck’s dotted figure, the secret shape was a tree.

  Birds sat perched on a branch divergent from reptiles. Insects had diverged from the main trunk before it yielded mollusks. Walruses and other marine mammals lay farther along that trunk, beyond which still other branches led to whales, then to hoofed mammals, and finally to all other mammals. Wrong though it was about the particulars, and despite being upside down, this figure marked an important transition in scientific thought. Scholars tell us that it was the earliest evolutionary tree.

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  Edward Hitchcock stands as a counterpoint to Lamarck, with that first evolutionary tree, in that Hitchcock offered a last pre-evolutionary tree in the decades before Darwin changed everything. In fact, Hitchcock presented two separate trees of life, one for animals, one for plants, in his 1840 book Elementary Geology, which became a successful and often-reprinted text in the mid-nineteenth century. Hitchcock’s trees were also innovative—among the first based on deep knowledge of fossils, not just close observation of living creatures. He called his illustration a “Paleontological Chart,” and what it shows is diversification of the animal and plant kingdoms charted against geological time, from the Cambrian period (beginning about 540 million years ago) to the present.

  Hitchcock’s trees weren’t classically tree shaped, spreading outward into a canopy like a maple or an oak. Each of the two, the one for animals and the one for plants, looks more like a windbreak of tightly placed Lombardy poplars grown to maturity along a roadway. The base of each windbreak is a thick, solid trunk from which rise slender stems, fluffy with foliage but without much branching as they ascend. Vertical, parallel, they seem independent: crustaceans, worms, bivalves, vertebrates. The vertebrate stem does branch into several shafts. The shaft leading up to modern mammals culminates in the word Man, atop which sits a regal crown adorned by a cross.

  The crowned “Man,” with its cross, tells us what we need to know about Hitchcock’s sense of hierarchy in the living world. He grounded his geology firmly within the tradition known as natural theology, meaning science purposed to illuminate the power and wisdom of God as creator of all, with humans as the culmination of that divine creativity. He was a devout, driven New England Yankee, and his “Paleontological Chart” reflected his view of humans as the apogee of creation, as well as his findings in geology.

  Hitchcock was born to a poor family in Deerfield, Massachusetts, his father a Revolutionary War veteran and a hatter by trade, with debts and three sons, who found just enough money to see his boys through primary school and some time at the local academy. After that, as Hitchcock recalled, “nothing was before me but a life of manual labor.” He balked at the idea of apprenticing as a hatter, to his father, or in any other trade. Instead he worked on a farm—it was rented land, cropped by one of his brothers—for a period that stretched on so long, or what felt like so long, that later he claimed not to remember how many years. With his free time, especially rainy days and evenings, young Edward studied science and the classics. Ambitious and hungry, he thought he was preparing himself for Harvard. Under the influence of an uncle, he took up astronomy. Then came the great comet of 1811, a celestial passerby that reached its peak of brightness in the north sky during autumn that year, when Hitchcock was eighteen. He borrowed some instruments from Deerfield Academy and spent night after night measuring its progress. “I gave myself to this labor so assiduously that my health failed,” he wrote later.

  The health crisis brought on a religious conversion: from Unitarianism, into which he had drifted, back to the Congregationalism of his father. That passed for a drastic rethink in Edward Hitchcock’s life. In lieu of Harvard, he returned to Deerfield and somehow got hired, at age twenty-three, as principal of the academy. Then he studied for the ministry, was ordained, and became pastor of a Congregationalist church in Conway, Massachusetts, just up the road from Deerfield. Thro
ughout these years and for the rest of his life, Hitchcock remained an invalid in self-image if not bodily, obsessed with his own fragility, continually complaining that he felt death nearby, although he lived to be seventy. One scholar, having looked into his life and work, called him “a hypochondriac of the first rank.”

  Hitchcock’s “Paleontological Chart,” 1857 version.

  Conveniently for his scientific career, he was “dismissed” from the Conway pastorate in autumn 1825 on the grounds of impaired health and imminent death if (according to his own worried judgment) he didn’t stop preaching, circuiting the parish, and running revivals. Amherst College, recently founded, hired him to teach chemistry and natural history, and he stayed there the rest of his life, serving later as professor of natural theology and geology, and for one nine-year stretch also as president. The early years of Hitchcock’s career at Amherst spanned the period when Charles Lyell, in England, published his multivolume Principles of Geology, a radical work that challenged Scripture-based interpretations of the geological record, including Hitchcock’s own.

  The conventional school of thought, known as catastrophism, saw Earth’s history as a series of cataclysmic upheavals cast down like thunderbolts by the Creator, such as the bolt that brought forty days and forty nights of rain, documented in Genesis as Noah’s flood. These catastrophes were considered directional and purposeful, in the sense that God used them as occasions for purging the planet of some creatures (dinosaurs, begone) and adding new creations (mammals, arise). Lyell’s alternative view was uniformitarianism, insisting that the processes and events that shaped Earth in the past were physical, such as erosion and deposition, as well as the occasional volcanic eruption—things that continue to occur in the present at roughly the same rate they did in the past. Those forces caused extinctions, among other effects. Second thoughts by God about what fauna and flora should exist, according to Lyell, did not enter into it.