Ten Naturalists Who Learned to Sort the Living World, From Aristotle to Haeckel

Aristotle organized the differences among animals in his Historia Animalium across four categories: parts, activities, ways of life and character traits. He rejected simple either-or classification and grouped animals by clusters of shared, stable traits, which is why the atlas treats him as the starting point of the scientific study of life.

Theophrastus, Aristotle's student and successor at the Lyceum, turned the same method on plants. His Historia Plantarum and De Causis Plantarum classified more than five hundred species by observable traits such as leaf and fruit structure, and nothing of comparable scope appeared until the sixteenth century.

John Ray set out in his three-volume Historia Plantarum, published from 1686 to 1704, to classify and catalog every known plant. He grouped plants by overall structure rather than by any single feature and is credited with establishing the split between monocotyledons and dicotyledons that is still used.

Francis Willughby worked with Ray on the idea that nature should be classified by physical characteristics rather than by folklore, myth or alphabet. His Ornithology, published by Ray in 1676 four years after Willughby died, aimed to describe all the birds then known and is credited with founding scientific ornithology.

Pier Antonio Micheli showed in his 1729 Nova Plantarum Genera that fungi reproduce from spores rather than arising by spontaneous generation, using melon slice experiments. Of the nearly nineteen hundred plants the book covers, about nine hundred were fungi and lichens, which is why he is regarded as the father of modern mycology.

Carl Linnaeus replaced the long descriptive Latin phrases of earlier naturalists with a two-part name, a genus followed by a specific epithet. His Species Plantarum of 1753 is the official starting point for plant scientific names, and the tenth edition of his Systema Naturae in 1758 does the same for animal names.

Josephus Nicolaus Laurenti coined the term herpetology in his 1768 book on reptiles and established the class Reptilia. He defined thirty genera where Carl Linnaeus had recognized ten a decade earlier, extending the Linnaean framework to a new group of animals.

Jean-Baptiste Lamarck coined the term biologie in 1802 and argued that species are not fixed but descend from earlier forms, changing as organisms adapt. His later rejected mechanism of inherited acquired traits was still a first coherent theory of species transformation, and he organized the study of invertebrates as a professor in Paris.

Georges Cuvier founded comparative anatomy and vertebrate paleontology on the principle of the correlation of parts, that every part of a functioning body constrains the others. He showed from fossil elephant remains that some species had gone extinct, and he opposed Lamarck by holding that species were fixed.

Ernst Haeckel, in his 1866 Generelle Morphologie der Organismen, named a new science Oecologie and defined it as the study of the relationships of an organism to its surrounding organic and inorganic environment. He also coined terms still in use such as phylum, and this stop closes the path where classification becomes the study of relationships.