How Carl Linnaeus Set Out to Label All of Life

The New Yorker · by Kathryn Schulz · August 14, 2023

For the Tyrannosaurus rex, as for Elvis and Jesus, being extremely dead has proved no obstacle to ongoing fame. Last seen some sixty-six million years ago, before an asteroid wiped out three-quarters of the life-forms on earth, it is nonetheless flourishing these days, thanks in large part to Michael Crichton, Steven Spielberg, and elementary-school children all over the world. In my experience, such children not only can rattle off the dinosaur’s vital statistics—fifteen feet tall, forty feet long, twelve thousand pounds—but will piously correct any misinformation advanced by their paleontologically passé elders. And here is the most surprising thing that all those ten-year-olds plus pretty much everyone else on the planet know about T. rex: the creature’s proper scientific name.

That name is itself properly called a binomen, the smallest unit in the vast system known as binomial nomenclature. You’ll remember the gist from basic biology: to eliminate any possible overlap or confusion, every species on the planet, whether extant or extinct, is assigned a full name, consisting of its genus (used here as a surname of sorts, indicating to what other creatures it is related) followed by its species, with both halves Latinized, and the genus sometimes reduced to just an initial, like Josef K. Thus: Tyrannosaurus rex, or T. rex, of the genus Tyrannosaurus and the species rex, known in full translation as King of the Tyrant Lizards.

Binomial names are extremely important to scientists but rarely used by the rest of us. Apart from T. rex, I am aware of only a few that crop up in everyday conversation. We know our own full name, of course—Homo sapiens, the last surviving species in a genus that once included Homo habilis, Homo floresiensis, Homo neanderthalensis, and several others—as well as that of the boa constrictor, a snake of the genus Boa, and E. coli, a bacterium of the genus Escherichia. You could argue based on those two examples plus T. rex that we speak respectfully of species that are potentially dangerous to us—not a bad policy, but also not a good argument, since a fourth example that comes to mind is Aloe vera. Also, almost no one outside scientific circles calls the great white shark Carcharodon carcharias.

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Inside scientific circles, however, binomial nomenclature still rules the day, lending concision and clarity to fields ranging from molecular biology to evolutionary ecology. It was developed, as you might also remember from your school days, by the Swedish botanist Carl Linnaeus in the middle of the eighteenth century, an era that was in thrall to the mighty project of trying to systematize all of nature. Appropriately for his line of work, Linnaeus’s name remains widely known, and he is hailed in his country of origin as his own kind of rex—the King of Flowers. But the details of his life and the nature of his scientific contributions are both less contemplated and more complicated, with his staunchest defenders characterizing him as an Enlightenment-era genius who paved the way for Charles Darwin, and his fiercest critics casting him as one of history’s most influential racists. A new biography, “The Man Who Organized Nature” (Princeton), written by Gunnar Broberg and translated from the Swedish by Anna Paterson, attempts to provide the fullest possible account of his life yet fails to grapple with the fundamental question it raises: if categorization is crucial to making sense of the world, how should we classify Carl Linnaeus?

The future father of modern taxonomy was born in Råshult, a village in southern Sweden, in 1707. His own father had originally been called Nils Ingemarsson, because he was the son of a man named Ingemar and most Swedes used a patronymic, but when Nils went off to university to study theology he was required to choose a new surname. For inspiration, he turned to a venerable linden tree on the land where he grew up—a lin, as it was known in the local dialect. Reborn as Nils Linnaeus, he was ordained in the Lutheran Church, got married, and had a son, Carl. Thus did the man who would name species get his name from a species.

It is a pretty bit of backstory, part and parcel of a thematically tidy childhood. Nils, himself an amateur botanist and an avid gardener, decorated his infant son’s crib with buds and blossoms. As the boy grew older and prone to the outbursts of toddlerhood, he could be calmed by being handed a flower, and from an early age he began helping in the garden. After his father reprimanded him for forgetting the name of a plant, he vowed never to do so again, and, soon enough, he could identify virtually everything that grew in his native region. Nonetheless, he was a middling student, and his parents were distraught when his teachers informed them that he was not fit to follow his father into the ministry. Linnaeus decided to study medicine instead, chiefly because it served as a side door into the study of botany. As Broberg writes in his biography, “Medicine demands two kinds of knowledge, of the body and of what cures ailments,” and the latter amounted to a mandate to continue learning about plants.

That proved difficult at Uppsala University, where Linnaeus got most of his higher education, and where he found the quality of the teaching abysmal; in all his time there, he never managed to hear a single lecture on botany. He did, however, meet someone who would change his life: Peter Artedi, a fellow-student and a budding ichthyologist, who, like Linnaeus, had disappointed his parents by failing to enter the ministry. The two became instant and devoted friends, and soon hatched, in the words of the twentieth-century botanist William Stearn, “the grand plan of revealing the works of the creator in a systemic, concise, and orderly fashion.” Like Spain and Portugal in the Treaty of Tordesillas, they divided up the world between them: Artedi, by many accounts the greater intellect, would take the fish, reptiles, and amphibians, while Linnaeus would take the birds, insects, and the majority of the plants, and the two men would collaborate on mammals and minerals. If either of them died before the project was completed, they pledged, the other would finish his work. That was in 1729. Six years later, Artedi, then thirty years old and temporarily living in Amsterdam, was out walking late one night when he fell into an unfenced canal and drowned.

Linnaeus kept his promise, although by then he was already well on his way to describing the entire world on his own. At Uppsala, he had availed himself of the lax school schedule to study more and more species. During a field trip to an island in Lake Mälaren, while most of the other students were picnicking and lazing about he walked, as he later wrote, the way a man might plow, “along and crosswise, back and forth, one of my paths ran hardly further from the earlier one than by two feet.” He documented eighty-eight species that day; another biological survey of the island conducted more than two hundred years later identified only seventeen that he had missed.

As word of Linnaeus’s gifts spread, he began acquiring friends in high places, including one who offered him a position delivering lectures at the university’s botanic gardens. That appointment earned Linnaeus some ire—it was normally reserved for academic elder statesmen, and he was still technically an undergraduate—but it further established his reputation as a rising star, and the talks he gave at the gardens routinely drew hundreds of people. That was in part because Linnaeus was advancing the theory that plants, like animals, reproduce sexually, their stamens releasing pollen to fertilize the ovules contained in pistils. That insight was crucial to the development of Linnaeus’s systematics; he began dividing flowering plants into classes based on their stamens, subdividing those classes into orders based on their pistils, then further subdividing them into genus and species. (The intermediary category “family” wasn’t widely used in Linnaeus’s time, and “phylum” would not be created until the eighteen-sixties.)

Useful as these ideas were, they scandalized some of Linnaeus’s contemporaries, not least because the plant kingdom, like the animal kingdom, proved to be sexually unruly. Linnaeus spoke tenderly of flower petals serving as a “bridal bed,” but close examination of the reproductive methods of plants revealed relations that looked less like heterosexual monogamy than like homosexuality, polygamy, miscegenation, and incest. “Who would have thought that bluebells, lilies, and onions could be up to such immorality?” one critic mocked.

Still, the whiff of scandal helped spread Linnaeus’s name. Bolstered by his newfound stature, he applied for funds from Sweden’s Royal Society of Science in order to journey to Lapland, today the northernmost portion of Finland—most of it lies north of the Arctic Circle—but then part of Sweden. The money came through in the spring of 1732, whereupon he set off, at the age of twenty-five, for the first major expedition of his lifetime.

It was also the last one. Linnaeus was not cut out for the kind of swashbuckling adventures undertaken by so many explorer-scientists of the eighteenth and nineteenth centuries. In Lapland, he admired the native Sami people for their health, fortitude, and fashion sense, returning home with a Sami outfit that he wore anytime he could gin up a plausible reason to do so, including while sitting for perhaps his most famous portrait. But he complained bitterly of the hardships of travel—“Had it been punishment for a capital offence,” he wrote of the journey, “it would still have been a cruel one”—and vowed never to undertake such a voyage again.

True to his word, Linnaeus left his native land only once more, and not for the wilds of South Africa or Surinam or the New World, where people kept encouraging him to go, but only across the North Sea to the Netherlands, at the time one of the leading scientific centers of Europe. At a Christmas party shortly before he left, he met an eighteen-year-old named Sara Elisabeth Moraea, and just after the new year he came courting at her door, dressed in his complete Laplander outfit (never mind that some of it was women’s wear). Three weeks later, he proposed to her; she accepted, and her parents blessed the union on the condition that the wedding not take place for three years. Linnaeus vowed eternal fidelity to her, then promptly left the country.

The geography of the rest of Linnaeus’s life is quickly told. He spent most of that premarital interlude in the Netherlands, living on the property and payroll of George Clifford, a wealthy director of the Dutch East India Company and Linnaeus’s most generous patron. Linnaeus helped tend Clifford’s fabulous gardens, wrote a book about their contents (“Hortus Cliffortianus”), and astonished his fellow-botanists by coaxing a banana tree into producing fruit well north of the fiftieth parallel. (He sent the results of a subsequent and equally successful experiment to the Swedish royal family, the only people to eat bananas there for almost two hundred years.) Then, in 1738, he returned to Sweden, began working as a doctor—a sluggish career that took off only when he started treating young libertines for gonorrhea—and finally married Sara Elisabeth. Together they had a son, also named Carl, followed by six more children, two of whom died before the age of four. When Linnaeus was appointed professor of botany and medicine at his alma mater, a job he had coveted since his student days, the family settled back in Uppsala, where, between a house in town and an estate on the outskirts, they lived the rest of their years.

Gunnar Broberg’s biography dutifully accompanies Linnaeus every step of the way, trekking through his life for four-hundred-plus pages. These are not, unfortunately, a pleasure to read. A representative sentence: “That the printing plans did not become reality, however, is not a sign of failure but rather that he tested the wind and his own ability and examined what he wanted to say.” Who knows whether prose like that is the fault of the writer or the translator, but the latter definitely can’t be blamed for the most ironic weakness of “The Man Who Organized Nature,” which is that it suffers from a problem of organization. Like most biographers, Broberg structures his book chronologically—a time-honored strategy, but a limited one, since it dictates only the order of the material, not what to leave out and what to put in. Those decisions must be made separately, according to some principle of salience, but no such discernment seems to have shaped Broberg’s book, which is full of things we don’t need to know, including the height and hair color of fleeting friends from Linnaeus’s undergraduate years.

The main problem with “The Man Who Loved Nature,” though, is not all the things in it we don’t need to know but all the things we need to know that aren’t in it. We care about Linnaeus today for his outsized role in the grand project of trying to systematize nature—a project that, for good and ill, changed the way we think about the world. Broberg, a Swedish professor of the history of science who died last year, should have been well positioned to explore that project and its impact, but his book never substantively strays from biography to intellectual history. Nor does Wilfrid Blunt’s 1971 “The Compleat Naturalist: A Life of Linnaeus, ” the definitive English-language account of the great taxonomist. The first book is a laborious account of Linnaeus’s life, the second a lucid one, but neither succeeds at the fundamental task of biography: to show us why that life mattered.

The impulse to impose order on nature is an ancient one. Aristotle tried to do it; so did his contemporary Theophrastus, often considered the father of botany; so did the first-century polymath Pliny the Elder, whose “Naturalis Historia” was enormously influential, albeit mostly wrong; so did the countless medieval monastics who carefully arranged all of creation in a “Great Chain of Being,” positioning each entity in accordance with its imagined proximity to God—beginning with seraphim and cherubim, continuing on to humans, and descending all the way down through oysters, mushrooms, moss, and rocks.

That system, as much a moral order as a biological one, began to erode only under the combined influence of the Scientific Revolution, the Age of Exploration, and the Enlightenment. The first brought with it technological innovations that radically enhanced the observational powers of naturalists—including the microscope, although Linnaeus himself never used one. The second vastly expanded the number of known species, as travellers in foreign lands described or brought home previously unfamiliar plants and animals. The third, with its emphasis on reason, made it possible to conceive of organizing nature according to its observable properties, rather than in purely theological terms.

Owing to all this, by the seventeen-thirties, when Linnaeus began his taxonomic work in earnest, the study of nature had reached a curious fulcrum. For perhaps the first time in history, the practical, political, and intellectual conditions existed for entirely reimagining the relationships among living beings; for perhaps the last time in history, it was possible to believe that a single person might do so. This was Linnaeus’s ambition. An exact contemporary of Denis Diderot, he wanted to become, in the words of William Stearn, “the great biological encyclopaedist.”

He succeeded, but the innovation for which he is best remembered today, binomial nomenclature, was merely a side effect of that goal. Before he came along, species’ names often ran long; plain old peppermint, for example, was Mentha floribus capitatus foliis lanceolatis serratis subpetiolatis. (Roughly: “Mint, crowned with flowers, with sawtooth, lance-shaped leaves and very short petioles.”) Names like that were full of information but unwieldy and impossible to remember, let alone to write down while, say, doing field work in the pouring rain. Linnaeus’s great insight was that this method was trying to accomplish two separate and competing aims: precise description and clear identification. He promptly separated those objectives, rendering distinct the two fields now known as classification and nomenclature. The former required carefully characterizing each plant or animal, but the latter required only that each species be given a bespoke, non-overlapping name. Thus liberated from description in matters of nomenclature, you could name a flower for a friend, a weed for an enemy.

Whatever a species’ name was, Linnaeus determined that for brevity it should always be a single word, and, for universal comprehensibility, it should be rendered in Latin—at the time, the lingua franca of the scholarly world. (Among his other contributions, Linnaeus essentially created botanical Latin, which is as distinct from classical Latin as modern Hebrew is from the liturgical variety.) Having established those basic rules, he then set about, like Adam in the garden, naming all of creation.

Although Linnaeus was a wildly prolific writer, producing everything from scholarly tomes to vanity projects, coffee-table books, and self-help guides, his most important contributions to the world of science are contained in just two works: “Species Plantarum,” a two-volume, twelve-hundred-page compendium of plant species, published in 1753, and “Systema Naturae,” which was originally published in 1736 as fourteen folio pages but grew across twelve editions and thirty years into three volumes and twenty-three hundred pages. It is these two books which established the basis for, respectively, modern botanical nomenclature and modern zoological nomenclature. In them, Linnaeus listed every organism then known to exist, and personally coined names for more than twelve thousand species of plants and animals. But what was prodigious in his day is paltry in ours; today, his system of nomenclature has been used to distinguish more than one and a half million species—that is, if such a thing as a species even exists.

What Linnaeus sought to do was organize nature according to its fundamental, intrinsic divisions—to carve it at the joints, in Plato’s famous formulation. But what he actually did, for the most part, was impose artificial categories on the natural world for the convenience of scientists. His use of stamens and pistils to classify flowering plants, for instance, was incredibly useful: it meant that a fellow-botanist facing an unknown plant could simply assess those parts to determine its order, class, and genus. But this system was also entirely arbitrary, in that it disregarded every other part of the plant, including those which might be more salient to understanding its place in the natural order of things.

This is not a retroactive assessment; Linnaeus himself knew full well the limitations of his classification method. To achieve a system completely in accordance with nature was, he wrote, “the first and last wish of botanists.” But the more closely you looked at her bounty the more difficult that prospect became—so, in the meantime, “artificial systems are absolutely necessary.”

In philosophy, this tension between intrinsic and imposed categories takes the form of a debate between nominalism and realism. Realists, whose ranks include everyone from strict creationists to Stephen Jay Gould, believe that nature is full of real and discrete categories, from “amphibian” to “zinc,” and that the job of the scientist is to discern them accurately. Nominalists believe that nature lacks clearly defined categories, and that we simply impose those distinctions upon it—creating, as it were, the illusion of joints where none really exist. This is not just the position of French theorists and post-truth relativists. “I look at the term ‘species’ as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other”: that is Charles Darwin, in the second chapter of “On the Origin of Species.”

That book, of course, trumpeted to the world a very large problem with the entire notion of a species. Like nearly all previous and contemporaneous scholars, Linnaeus believed (with the occasional pang of doubt) that at creation God established each species in the exact form we know it today. But that idea was incompatible with evolutionary theory, according to which species are constantly changing—emerging, diverging, going extinct.

“On the Origin of Species” was published in 1859. In the century and a half since then, advances in biology have radically changed the way scientists characterize species, with the result that once-established categories have fallen apart. The giraffe, for instance, known since Linnaeus’s time as the single species Giraffa camelopardalis, is today recognized by geneticists as four distinct species, while the linden tree for which Linnaeus was named now belongs to a different biological family from the one to which he assigned it. Even the broadest distinctions among living beings have changed enormously over time. Following Aristotle, Linnaeus placed all life-forms in three kingdoms: animal, vegetable, and mineral. Today, most scientists recognize either five or six kingdoms (Animalia, Plantae, Fungi, Protista, and Monera, with the last group sometimes divided into Archaebacteria and Eubacteria). Meanwhile, scientists have superimposed over those kingdoms the higher rank of domain, which, depending on whom you ask, consists of two divisions, Archaea and Bacteria, or those two plus a third, Eukarya.

Nor is it just specific species or even specific kingdoms that have changed. The very concept of a species is in radical flux, too, with more than twenty competing definitions in circulation. The one most familiar to laypeople regards a species as a population of individuals that reproduce only with one another. (One obvious problem with that definition: plenty of life-forms reproduce asexually.) Choosing a definition is not just a matter of what goes in the dictionary under “species”; which one you use will determine how you divide up nature, such that a group of creatures that would be regarded as a species by one standard might not merit the label by another. All this confusion comes, as Darwin wrote, “from trying to define the undefinable.” Yet committed realists continue to promulgate more and more definitions, in the belief that one of them will map perfectly onto some intrinsic and stable feature of nature. Darwin called that idea “laughable,” a word that captures the impossibility but not the gravity of arbitrarily imposing categories on living beings.

Of all the species Linnaeus set out to define, the most troubling by far—in his time and ours—was Homo sapiens. In earlier taxonomies, we humans had enjoyed a category unto ourselves, morally superior to and ontologically distinct from all other animals. This bothered Linnaeus, who recognized the extensive similarities between us and apes. Accordingly, in later editions of “Systema Naturae,” he placed humans among the primates, in his newly created category of Mammalia. (That category replaced Quadrupedia, after Linnaeus, who in his free time lobbied against the upper-class practice of using wet nurses, determined that suckling the young was a more salient distinction than possessing four legs.) That classification ran contrary to the long-standing Christian insistence that humans ranked above rather than among other animals, but although Linnaeus was himself a devout Lutheran, he never backed down from his conviction about our place in the order of things. Those of his compatriots who read his “Fauna Svecica” might have been surprised to find that he included Swedes in his account of the fauna of Sweden.

For most people, though by no means all, our fellowship with primates is no longer as troubling as it was in Linnaeus’s time. What disturbs us today is not how he categorized us among other animals but how he categorized us among ourselves. In the first edition of “Systema Naturae,” he listed four variations of the human species, based on geographic distribution: Americanus rubescens, Europaeus albus, Asiaticus fuscus, and Africanus niger. Those modifiers correspond to colors—red, white, yellow, and black—even though he wrote in “Philosophia Botanica” that “color is wonderfully variable and hence of no value for definitions.” But what applied to flowers apparently did not apply to humans.

Still, those differences in coloration were basically innocuous, a reflection of the broadly correct theory that skin color corresponded to climate. It was not until the tenth edition of “Systema Naturae” that Linnaeus linked his divisions within Homo sapiens to character traits: Homo americanus was “unyielding, cheerful, free”; Homo europaeus was “light, wise, inventive”; Homo asiaticus was “stern, haughty, greedy”; and Homo africanus was “sly, sluggish, neglectful.”

What are we to make of these invidious and uninformed distinctions? Broberg dismisses them with a wave of the context wand. “Labels such as ‘racism’ and ‘racist’ are frequently misleading when applied to circumstances and people in the past,” he writes—a curious defense, given that the misleading application of labels is precisely what is at issue here. It’s true that the word “racist” did not exist in the eighteenth century, but the era was hardly free of racial prejudices; those are exactly what Linnaeus absorbed and then presented as scientific absolutes. He could not have been oblivious of the consequences of doing so, not least because “the circumstances of the past” include, in this case, Sweden’s profitable involvement in the Atlantic slave trade, the proponents of which, like proponents of racial hierarchies in every time and place, looked to nature to try to legitimatize their bigotry and cruelty.

And yet it is true that Linnaeus’s legacy on matters of race is a complicated one. He was not antisemitic, despite the prevailing sentiments of his time and place; indeed, he sought out Jewish communities in Holland and wrote about their customs with fair-minded attentiveness. In Lapland, he regarded the Sami with admiration, felt that they were in many respects superior to Scandinavians, and recorded with dismay the brutality to which Christian Swedes resorted while trying to convert them. Perhaps most striking, he seemed to view nurture as more determinative than nature when it came to distinctions among people. In that same edition of “Systema Naturae” where he linked geography to character, he also added another subvariety of human being, Homo monstrosus—which, surprisingly, referred not to people with congenital abnormalities but, rather, to those who were “deformed” by their environment. By way of example, he cited, among others, wasp-waisted, corset-wearing European women.

That strange category gestures toward the most paradoxical fact about a man who unquestionably helped lay the groundwork for future generations of “scientific” racists. Again and again, Linnaeus insisted that we humans—literally over and above our distinctions—are all one species, fundamentally deserving of being treated as the same. We cringe today, reading him on what he saw as the huge gap between the “Hottentot” and the “highly enlightened prime minister in Europe”—but his point was that the gap was less extreme than his contemporaries imagined, that the two of them, like all of us, are equally sapient, equally human.

It is consistent with the rest of Linnaeus’s life that his legacy on race is so contradictory; seldom has a more paradoxical person existed. He was a lovely writer (“The corn-frogs croak toward evening,” he once observed, “making a sound like big bells rung three or four miles away”), but his most influential books are deadly dull. He was admired for his supremely orderly mind yet prone to outbursts of temper that startled and dismayed his students. He depended on the generosity of countless mentors to achieve his success yet was profoundly ungenerous in return, refusing to share specimens from his collection and appropriating without credit the work of other botanists and illustrators. He was committed to exactitude yet inclined to hyperbole and dishonesty; in his report to the Royal Society on the Lapland journey, he exaggerated the distance he covered, and described the mountains in the region as higher than Everest. He was a central figure of the Enlightenment but cared not at all for philosophy or politics—or, for that matter, for art, literature, music, or theatre. He regarded himself as just a humble servant of God, doing his best to reveal the order in divine creation, but was a shameless megalomaniac whose boasts could form their own taxonomic kingdom. (He claimed to have “discovered in the field of natural history more than anyone could have believed possible”; his books were, variously, “the greatest achievement in the realm of science,” “the fairest jewel in medicine,” “a masterpiece that no one can read too often.”) He was a committed homebody, and yet his work and legacy depended on the global travels of scores of “apostles,” as he called them, who performed the dual function of sending specimens back home and evangelizing for his system abroad.

Those apostles performed their duties admirably. Linnaeus lived to see his system adopted almost universally, his praises sung just as far, and his own nomenclature updated, upon his ennoblement by the King of Sweden, to Carl von Linné. That is, perhaps, the most fundamental paradox of Linnaeus’s life: that so much fame could be achieved through such fundamentally humdrum work. It is true that he was an exceptional botanist with remarkable powers of observation and incredible stamina; it is also true that he was mostly a kind of biological Marie Kondo, endlessly sorting and systematizing, and that his scholarship was ultimately more bureaucratic than profound. Those limitations have grown only more obvious with time, because, for all intents and purposes, the world as Linnaeus described it no longer exists. Only the system he devised to do the describing endures. ♦