Human taxonomy
Linnaeus's system of taxonomy was the first to include humans (Homo) taxonomically grouped with apes (Simia), under the header of Anthropomorpha. German biologist Ernst Haeckel speaking in 1907 called this the "most important sign of Linnaeus's genius".
Linnaeus classified humans among the primates, beginning with the first edition of Systema Naturae. During his time at Hartekamp, he had the opportunity to examine several monkeys and noted similarities between them and man. He pointed out that they basically had the same anatomy; except for speech, he found no other differences. Thus he placed man and monkeys under the same category, Anthropomorpha, meaning "manlike". This classification received criticism from other biologists such as Johan Gottschalk Wallerius, Jacob Theodor Klein and Johann Georg Gmelin on the ground that it is illogical to describe man as human-like. In a letter to Gmelin from 1747, Linnaeus replied:
It does not please [you] that I've placed Man among the Anthropomorpha, perhaps because of the term 'with human form', but man learns to know himself. Let's not quibble over words. It will be the same to me whatever name we apply. But I seek from you and from the whole world a generic difference between man and simian that [follows] from the principles of Natural History. I absolutely know of none. If only someone might tell me a single one! If I would have called man a simian or vice versa, I would have brought together all the theologians against me. Perhaps I ought to have by virtue of the law of the discipline.
The theological concerns were twofold: first, putting man at the same level as monkeys or apes would lower the spiritually higher position that man was assumed to have in the great chain of being, and second, because the Bible says man was created in the image of God (theomorphism), if monkeys/apes and humans were not distinctly and separately designed, that would mean monkeys and apes were created in the image of God as well. This was something many could not accept.
After such criticism, Linnaeus felt he needed to explain himself more clearly. The 10th edition of Systema Naturae introduced new terms, including Mammalia and Primates, the latter replacing Anthropomorpha and giving humans the full binomial Homo sapiens. The new classification received less criticism, but many natural historians still believed he had demoted humans from their former place of ruling over nature. Linnaeus believed that man biologically belonged to the animal kingdom and had to be included in it. In his book Dieta Naturalis, he said, "One should not vent one's wrath on animals. 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."
Linnaeus added a second species to the genus Homo in Systema Naturae based on a figure and description by Jacobus Bontius from a 1658 publication: Homo troglodytes ("caveman") and published a third in 1771: Homo lar. Swedish historian Gunnar Broberg states that the new human species Linnaeus described were actually simians or native people clad in skins to frighten colonial settlers, whose appearance had been exaggerated in accounts to Linnaeus. For Homo troglodytes Linnaeus asked the Swedish East India Company to search for one, but they did not find any signs of its existence. Homo lar has since been reclassified as Hylobates lar, the lar gibbon.
In the first edition of Systema Naturae, Linnaeus subdivided the human species into four varieties: "Europæus albesc[ens]" (whitish European), "Americanus rubesc[ens]" (reddish American), "Asiaticus fuscus" (tawny Asian) and "Africanus nigr[iculus]" (blackish African). In the tenth edition of Systema Naturae he further detailed phenotypical characteristics for each variety, based on the concept of the four temperaments from classical antiquity, and changed the description of Asians' skin tone to "luridus" (yellow). While Linnaeus believed that these varieties resulted from environmental differences between the four known continents, the Linnean Society acknowledges that his categorization's focus on skin color and later inclusion of cultural and behavioral traits cemented colonial stereotypes and provided the foundations for scientific racism. Additionally, Linnaeus created a wastebasket taxon "monstrosus" for "wild and monstrous humans, unknown groups, and more or less abnormal people".
Linnaeus treated himself as the type specimen (holotype) of H. sapiens. In 1959, W. T. Stearn designated Linnaeus as the lectotype of H. sapiens, following the International Code of Zoological Nomenclature, since the sole specimen that he is known to have examined was himself.
