From Aristotle to Linnaeus The basic idea of a ranking of the world's organisms goes back to
Aristotle's biology. In his
History of Animals, where he ranked animals over plants based on their ability to move and sense, and graded the animals by their reproductive mode, live birth being "higher" than laying cold eggs, and possession of blood, warm-blooded mammals and birds again being "higher" than "bloodless" invertebrates. Aristotle's non-religious concept of higher and lower organisms was taken up by
natural philosophers during the
Scholastic period to form the basis of the
Scala Naturae. The
scala allowed for an ordering of beings, thus forming a basis for classification where each kind of mineral, plant and animal could be slotted into place. In medieval times, the great chain was seen as a God-given and unchangeable ordering. In the
Northern Renaissance, the scientific focus shifted to biology; the threefold division of the chain below humans formed the basis for
Carl Linnaeus's
Systema Naturæ from 1737, where he divided the physical components of the world into the three familiar
kingdoms of minerals, plants and animals.
In alchemy Alchemy used the great chain as the basis for its cosmology. Since all beings were linked into a chain, so that there was a fundamental unity of all
matter, the transformation from one place in the chain to the next might, according to alchemical reasoning, be possible. In turn, the unit of the matter enabled alchemy to make another key assumption, the
philosopher's stone, which somehow gathered and concentrated the universal spirit found in all matter along the chain, and which
ex hypothesi might enable the alchemical transformation of one substance to another, such as the base metal
lead to the noble metal
gold.
In evolution back to
amoeba shown as a reinterpreted chain of being with living and
fossil animals. From a critique of
Ernst Haeckel's theories, 1873. The set nature of species, and thus the absoluteness of creatures' places in the great chain, came into question during the 18th century. The dual nature of the chain, divided yet united, had always allowed for seeing creation as essentially one continuous whole, with the potential for overlap between the links. Radical thinkers like
Jean-Baptiste Lamarck saw a progression of life forms from the simplest creatures striving towards complexity and perfection, a schema accepted by zoologists like
Henri de Blainville. The very idea of an ordering of organisms, even if supposedly fixed, laid the basis for the idea of
transmutation of species, whether progressive goal-directed
orthogenesis or
Charles Darwin's undirected theory of
evolution. The chain of being continued to be part of
metaphysics in 19th-century education, and the concept was well known. The geologist
Charles Lyell used it as a metaphor in his 1851
Elements of Geology description of the
geological column, where he used the term "
missing links" about missing parts of the continuum. The term "missing link" later came to signify
transitional fossils, particularly those bridging the gulf between man and beasts. The idea of the great chain, as well as the derived "missing link", was abandoned in early 20th-century science, as the notion that
embryonic development recapitulates "lower" forms was abandoned in biology, to be replaced by an
evolutionary tree supplemented by
horizontal gene transfer, as well as more complex
web structures. The idea of a certain sequence from lower to higher complexity and fitness is still popular, as is the idea of
progress in biology. == Political implications ==