Having never seen among plants a progression in perfection from "base" to "noble," botanists rejected the scala as a basis of classification at an early date. And, since the law of continuity requires that when the essential attributes of one being approximate those of another all the properties of the one must likewise gradually approximate those of the other, it is necessary that all the orders of natural beings form but a single chain, in which the various classes, like so many rings, are so closely linked one to another that it is impossible for the senses or the imagination to determine precisely the point at which one ends and the next begins. Thus men are linked with the animals, these with the plants and these with the fossils, which in turn merge with those bodies which our senses and our imagination represent to us as the absolutely inanimate. Thus, in describing the scala, the seventeenth century philosopher Gottfried Wilhelm Leibniz used many of the same terms ("chains," "missing links," "gradation,"…) later used in the context of neo-Darwinian theory:Īll the different classes of beings which taken together make up the universe are, in the ideas of God who knows distinctly their essential gradations, only so many ordinates of a single curve so closely united that it would be impossible to place others between any two of them, since that would imply disorder and imperfection. To a great extent, the view of evolution expressed in the Origin is a temporalization of a previously static scala, 4 which is to say that it used the same sort of terminology and made many of the same assumptions, but placed the discussion in a temporal context. 3 It was strongly associated with the ideas of divine order, perfection, continuity, and gradualism. The scala naturae was the dominant worldview of European thinkers for centuries. 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.
Albertus Magnus ( De animalibus, thirteenth century A.D.) put it,Īll things, however different, are linked together. Also known as "The Great Chain of Being," this system had religious roots and pictured beings rising in a linear order of perfection, 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 (this scale is illustrated at right).Īs St. When zoology was emerging as a science in the eighteenth century, its practitioners arranged their taxonomies in accordance with an age-old ordering principle handed down from medieval times, the scala naturae (literally, "the ladder of nature"). What, then, is the motivation for the many, apparently unsubstantiated assertions that animal hybrids and the evolution of animals are somehow fundamentally different from those of plants? Is it perhaps the self-flattering notion that animals are somehow special, higher, nobler? In particular, is such reasoning simply a manifestation of the ancient tendency to place Homo sapiens above other, supposedly baser types of organisms?
Scala naturae (Bonnet Œuvres d'histoire naturelle et de philosophie, 1781)Īnother representation of the scala naturae ( Liber de ascensu et decensu intellectus of Ramon Llull, written 1304, first published 1512).
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