The Scala NaturaeOnline Biology Dictionary
Also known as "The Great Chain of Being," this system had religious roots and pictured beings rising in a linear order, starting with inanimate minerals, and rising through fossils (which were considered something between the mineral and the living) to plants, animals, humans, celestial beings, and ultimately, God (an 18th century conception of the scala is shown at right). As St. Albertus Magnus (De animalibus, thirteenth century A.D.) put it, Nature does not make [animal] kinds separate without making something intermediate between them; for nature does not pass from extreme to extreme without an intermediate."¹This is the so-called Law of Continuity ("Natura non facit saltum"), often cited by Darwin. In his De docta ignorantia (1440), the schoolman Nicolas of Cusa makes similar claims:
All things, however different, are linked together. There is in the genera of things such a connection between the higher and the lower that they meet in a common point; such an order obtains among species that the highest species of one genus coincides with the lowest of the next higher genus, in order that the universe may be one, perfect, continuous.² The scala naturae was long the dominant worldview of European thinkers.³, but was gradually abandoned during the eighteenth and early nineteenth centuries. Having never seen among plants a progression in perfection from "base" to "noble," botanists were the first to drop it as a criterion of classification.⁴
But the concept of a linear chain of order held sway among zoologists until Georges Cuvier published his authoritative classification of animals, Le Règne Animal, in 1817, in which he divided the Animal Kingdom on the basis of anatomy into four phyla of equal rank (vertebrates, mollusks, echinoderms, and arthropods). After Cuvier, no biologist would again assert an ordering principle of "growing perfection" constitutes an appropriate basis for constructing systems of classification. But the tendency lingers, even today, to think of a mammal as somehow more advanced than a bird, or of a reptile as more complex than a fish, and certainly, of an animal as more advanced than a plant, assertions that would not be easy to establish on an empirical basis.
Notes (Works Cited) 1. Translated in Lovejoy (1936: 79). 2. Translated in Lovejoy (1936: 80). 3. Lovejoy (1936). 4. Mayr (1982: 200). The Scala Naturae - © Macroevolution.net
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