Carl Linnaeus

• 1. Introduction

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  Carl Linnaeus, born on the 23rd of May 1707 in the village of Råshult, in the countryside of Småland, southern Sweden, gave the living world a name for every creature in it. He built the system that scientists still use today: a two-part Latin name for every organism on Earth, from the smallest moss to the human being. That system is called binomial nomenclature, and before Linnaeus, nothing like it existed. By the time he died in 1778, he was one of the most acclaimed scientists in Europe, known as the "father of modern taxonomy" and celebrated by admirers as Princeps botanicorum, the Prince of Botanists.

  His life raises questions that go far beyond the naming of plants. How does a pastor's son from a remote Swedish village end up reshaping the way all of humanity understands nature? How did a young man so disinterested in his schoolwork that his own professors thought he would never amount to anything become the scientist who Jean-Jacques Rousseau called the greatest man on Earth? And what do we make of a thinker whose greatest achievement, the ordering of all life, also laid some of the groundwork for ideas about human races that later generations would put to harmful use?

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• 2. The Pastor's Son

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  Nils Linnaeus, Carl's father, was the first in his family line to adopt a permanent surname. Before him, ancestors had used the Scandinavian patronymic system, taking their father's given name as their own last name. When Nils enrolled at Lund University, he needed a family name and chose a Latinate word derived from a giant lime tree, lind in Swedish, that grew on the family homestead. That name, Linnæus, spelled with the æ ligature, passed to his son.

  Nils was a Lutheran minister and an amateur botanist who spent much time in his garden showing plants to young Carl and telling him their names. Whenever the boy was upset, he was given a flower, which immediately calmed him. Nils soon gave Carl his own patch of land to grow plants. These were the earliest lessons in a curriculum that would consume the rest of Carl's life.

  Carl's formal schooling was a different story. Sent to the Lower Grammar School at Växjö in 1717, he rarely studied, preferring to wander the countryside looking for plants. His father visited and, hearing critical reports from his teachers, seriously considered apprenticing his son to a cobbler. What saved Carl was a headmaster named Daniel Lannerus, who noticed the boy's passion for botany and introduced him to Johan Rothman, the state doctor of Småland and a teacher at Katedralskolan in Växjö. Rothman broadened Linnaeus's botanical interests, helped him develop an interest in medicine, and eventually offered to have the teenager live with his family. By age 17, Linnaeus had read deeply in the existing botanical literature and could cite it from memory.

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• 3. Mentors and Libraries

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  Rothman's most consequential advice came in August 1728, when he urged Linnaeus to transfer from Lund University to Uppsala University. Rothman had a specific reason: two professors at Uppsala's medical faculty, Olof Rudbeck the Younger and Lars Roberg, represented the best available teaching in medicine and botany. By the time Linnaeus arrived, however, Rudbeck no longer gave public lectures and had others stand in for him.

  At Uppsala, though, Linnaeus found a new patron in Olof Celsius, a professor of theology and amateur botanist who took Linnaeus into his home and gave him access to what was described as one of the richest botanical libraries in Sweden. In 1729, Linnaeus wrote a thesis on plant sexual reproduction, Praeludia Sponsaliorum Plantarum, and it caught Rudbeck's attention. By May 1730, Rudbeck selected Linnaeus to deliver lectures at the university, even though the young man was only a second-year student. His lectures drew audiences of around 300 people.

  That same winter, Linnaeus began to doubt the classification system of Tournefort, which he had been taught, and decided to build one of his own. His plan was to divide plants by the number of stamens and pistils. He began writing several works that would eventually become Genera Plantarum and Critica Botanica. A new tension arrived in March 1731 when Nils Rosén, a colleague with a freshly earned medical degree, returned to Uppsala and attempted to take over Linnaeus's botany lectures. Rudbeck blocked the move. By December of that year, Linnaeus had a falling-out with Rudbeck's wife and was forced to leave his mentor's house, though his relationship with Rudbeck himself seems to have survived intact.

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• 4. The Lapland Expedition

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  On the 12th of May 1732, just before he turned 25, Linnaeus set out from Uppsala on foot and horseback for Lapland, carrying his journal, botanical and ornithological manuscripts, and sheets of paper for pressing plants. The Royal Society of Sciences in Uppsala had awarded him a grant for the journey. His predecessor Rudbeck had made the same journey in 1695, but the detailed results of that earlier expedition were lost in a fire seven years afterward, making Linnaeus's trip all the more necessary.

  Near Gävle, he discovered large quantities of Campanula serpyllifolia, later known as Linnaea borealis, the twinflower that would become his favourite plant. He travelled clockwise around the Gulf of Bothnia, making inland detours from Umeå, Luleå and Tornio. Six months and over 2,000 kilometres later, he returned in October having described around 100 previously unidentified plants, which became the foundation of his book Flora Lapponica.

  Botanical historian E. L. Greene later called Flora Lapponica "the most classic and delightful" of Linnaeus's works. The account covered 534 species and applied Linnaeus's emerging classification system in practice for the first time, making it what scholars describe as the first proto-modern Flora. It was Augustin Pyramus de Candolle who credited the book with founding the botanical genre of Flora writing.

  The expedition also sparked a sudden insight about mammals. Seeing the lower jawbone of a horse by the roadside, Linnaeus reflected that if he knew how many teeth and teats every animal had, and where they were placed, he might be able to work out a perfectly natural system for classifying all quadrupeds. That roadside observation would eventually feed into the category he named Mammalia.

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• 5. The Dutch Years

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  In April 1735, Linnaeus and Claes Sohlberg, the son of a mining inspector, set out for the Dutch Republic. Linnaeus intended to earn his medical degree at the University of Harderwijk, a place known for awarding degrees in as little as a week, while tutoring Sohlberg in exchange for an annual salary. On the way, the pair stopped in Hamburg, where the mayor proudly showed off what he believed to be a taxidermied seven-headed hydra. Linnaeus quickly identified the specimen as a fake assembled from the jaws and paws of weasels and the skins of snakes. He made his observations public, threatening the mayor's hopes of selling the hydra for an enormous sum, and the two men had to flee Hamburg in a hurry.

  At Harderwijk, Linnaeus submitted a dissertation arguing that malaria arose only in areas with clay-rich soils. He failed to identify the mosquito as the true vector of transmission, but he did correctly predict that Artemisia annua, or wormwood, would become a source of antimalarial medications. Within two weeks he had passed his oral and practical examinations and held a doctoral degree.

  That summer, Linnaeus reunited with his friend Peter Artedi, with whom he had once made a pact that the survivor of the two would finish the other's unfinished work. Ten weeks later, Artedi drowned in the canals of Amsterdam, leaving behind an incomplete manuscript on fish classification.

  Linnaeus then met Johan Frederik Gronovius, who was so impressed by one of the manuscripts Linnaeus had brought from Sweden that he offered to help pay for its printing. With an additional contribution from the Scottish doctor Isaac Lawson, the manuscript was published in 1735 as Systema Naturae. In August of that year, Linnaeus met George Clifford III, a director of the Dutch East India Company who owned a rich botanical garden at his estate of Hartekamp in Heemstede. Clifford took him on as personal physician and curator of his herbarium at 1,000 florins a year with free board and lodging. Linnaeus later described his time at Hartekamp as "the happiest time of my life".

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• 6. Naming All Life

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  The first edition of Systema Naturae, printed in 1735, ran to just twelve pages. By the time it reached its tenth edition in 1758, it classified 4,400 species of animals and 7,700 species of plants. People from all over the world sent specimens to Linnaeus to be included. When he began work on the twelfth edition, the sheer volume of material required a new invention to stay organised: the index card.

  Species Plantarum, published in 1753, is now internationally accepted as the starting point of modern botanical nomenclature. The first volume appeared on the 24th of May, the second on the 16th of August. The work ran to 1,200 pages across two volumes and described over 7,300 species. That same year, the Swedish king made Linnaeus a knight of the Order of the Polar Star, the first civilian in Sweden to receive that distinction. He was rarely seen afterward without its insignia.

  The Linnaean system organised nature within a nested hierarchy starting with three kingdoms, which were divided into classes, then orders, then genera, then species. For animals, the higher groupings Linnaeus created still form the skeleton of modern classification, even if they have been significantly modified since. Among his quieter but lasting contributions was his popularisation of the Mars and Venus symbols, the male and female signs now used universally in science and beyond.

  Genera Plantarum, first published in 1737, described 935 plant genera. The most important edition, the fifth, appeared in 1754 and divided the plant kingdom into 24 classes. One of those classes, Cryptogamia, gathered all the plants with concealed reproductive parts: algae, fungi, mosses, liverworts and ferns.

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• 7. Placing Humans in Nature

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  From the first edition of Systema Naturae, Linnaeus placed humans alongside apes under the classification Anthropomorpha, meaning "manlike". During his time at the estate of Hartekamp, he had examined several monkeys and concluded that, apart from the capacity for speech, he could find no anatomical difference between them and human beings. German biologist Ernst Haeckel, speaking in 1907, called this the "most important sign of Linnaeus's genius".

  The reaction was fierce. Critics including Johan Gottschalk Wallerius, Jacob Theodor Klein and Johann Georg Gmelin argued that calling humans "manlike" was illogical. In a letter to Gmelin in 1747, Linnaeus replied with unusual candour: "I absolutely know of none. If only someone might tell me a single one!" He acknowledged the theological problem clearly: placing humans at the same level as apes threatened the idea that humans held a spiritually elevated place in the order of creation, and complicated the biblical claim that man was made in the image of God.

  In the tenth edition of Systema Naturae, Linnaeus introduced the terms Mammalia and Primates, the latter replacing Anthropomorpha, and gave humans the full binomial name Homo sapiens. He also, in that same edition, detailed phenotypical characteristics for four human varieties, linking them to the four temperaments of classical antiquity and assigning different skin-tone descriptors to each. The Linnean Society has acknowledged that this categorisation, with its focus on skin colour and inclusion of cultural and behavioural traits, laid foundations for what later became scientific racism.

  In his own book Dieta Naturalis, Linnaeus wrote: "Theology decrees that man has a soul and that the animals are mere 'automata mechanica', but I believe they would be better advised that animals have a soul and that the difference is of nobility."

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• 8. Legacy and Collection

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  After Linnaeus died on the 10th of January 1778 at his estate of Hammarby, his library and natural history collections passed to his widow Sara and their children. His son Carl refused an offer from the eminent botanist Joseph Banks to purchase the collection and instead moved it to Uppsala. Carl died in 1783, and Sara inherited everything, having outlived both her husband and her son. When she tried to sell the collection to Banks, he was no longer interested. Instead, a 24-year-old medical student named James Edward Smith purchased the entire collection: 14,000 plants, 3,198 insects, 1,564 shells, around 3,000 letters and 1,600 books. Five years later, Smith founded the Linnean Society of London.

  During his years as professor and rector at Uppsala University, Linnaeus trained 17 students he called his "apostles". He sent them across the world to collect and organise specimens according to his system. The first, Christopher Tärnström, a 43-year-old pastor with a wife and children, died of a tropical fever on Côn Sơn Island in 1746 before reaching his destination of China. His widow blamed Linnaeus for making her children fatherless, and after that Linnaeus preferred to send younger, unmarried students. Six other apostles died on their expeditions.

  Perhaps the most far-ranging was Carl Peter Thunberg, who embarked on a nine-year expedition in 1770, spending three years in South Africa before travelling to Japan, where all foreigners were confined to the small island of Dejima outside Nagasaki. Thunberg persuaded local translators to bring him plants and found others growing in the gardens of Dejima, returning to Sweden in 1779, a year after Linnaeus's death.

  Philosopher Jean-Jacques Rousseau wrote of Linnaeus, "I know no greater man on Earth." Johann Wolfgang von Goethe placed him above almost everyone except Shakespeare and Spinoza as an influence. The Linnean Society of London has awarded the Linnean Medal for excellence in botany or zoology since 1888, and in 2010, Växjö University and Kalmar College merged to form Linnaeus University. Linnaeus designated himself the type specimen of Homo sapiens, a status formally confirmed in 1959 when W. T. Stearn designated Linnaeus as the lectotype of the species under the International Code of Zoological Nomenclature.

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