Originally published in Ways of Making and Knowing: The Material Culture of Empirical Knowledge, edited by Pamela H. Smith, Amy R. W. Meyers, and Harold J. Cook. Ann Arbor: The University of Michigan Press, 2014. 357–376.

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The Amphiroa Orbignyana

Among the natural objects Darwin collected during his world tour on the Beagle is a species named Amphiroa Orbignyana. Darwin came across this organism among other underwater forms of life that lived in the environs of seaweed, algae, and corals in January 1834 at the beach of Puerto Deseado in the province of Santa Cruz in Argentina. He included it in the family of organisms close to corals, but of smaller size, which Pliny the Elder had named Corallinae. When Darwin collected the piece, he was unsure as to which kingdom it belonged, that of plants or animals. All we can say is that Darwin judged this organism to be a member of the broad family of corallines.1

Its significance for the history of science is revealed in its contemporary definition. Darwin’s entries suggest that his interest in corals went beyond the question of their classification; rather, he aimed at the essence of nature and its metamorphosis. Through this, the Amphiroa Orbignyana is one of the hidden key objects of modern biology.

Early Sketches

In his notebook B, which he began in July 1837, Darwin gave the first visual formulations of natural selection in drawings.2 The upper drawing shows a vertical dotted line, which, as it is followed upward, fans out to three cords. These three solid lines represent the still-living species of the water, earth, and air,3 while the dotted line indicates extinct species.4

At the starting point of the lower sketch, there is already a ramification that shows a hypothetical line of descent in the line of dots branching off to the left. This structure tries to formulate the complex descent of birds. Here as well, the dots indicate the areas of extinct species, which have come down to us only through fossils.5

Both sketches are of rather poor quality. Nevertheless, they have a historico-scientific and historico-cultural importance that cannot be overstated, as they do not formulate the history of nature as a stable plan, but rather as a temporally developing process. The drawings encapsulate the most dramatic rupture with the story of Genesis in the Old Testament.

The Tree of Life

Again and again, the system of ramification has been understood as a tree-like scheme,6 the more so as, shortly before these sketches, Darwin mentioned the tree as a model of evolution in his notebook: “organized beings represent a tree. irregularly branched some branches far more branched.— Hence Genera.”7 A little later he speaks of “a triple branching in the tree of life owing to three elements air, land & water, & the endeavour of each typical class to extend his domain into the other domains. & subdivision three more, double arrangement.”8 With these remarks, Darwin substantiated his idea that the macroevolution of species does not proceed by parallel developments within single cords, but in the form of a branching structure.

With the “Tree of Life,” Darwin made use of the widespread model that had been evoked for all areas of knowledge from the social to the biological. In the case of the root of Jesse and the Christian tree of life, this tradition dated back to the early Middle Ages.9 The tree model of the Neoplatonist Porphyry (233–304),10 which was supposed to locate all parts and terms of nature, was even more important. Above the roots of the individual features, the trunk rises from the human species to the species of animals, the living thing and the body, up to the substance of the crowned genus. Thus the tree of Porphyry also proceeded upside down from genus to species, terms that have been used ever since.

The fundamental significance of this model remained undisputed until Jean-Baptiste Lamarck, in his Philosophie zoologique of 1809, discerned the idea of transformation in the form of a diagram that evolves from the underdeveloped to the more specific and higher-developed species. Even his more abstract tree still grows upside down. In his notebook Darwin repeatedly characterized Lamarck’s theory of the deliberate mutation of species as “absurd.”11 His use of dots and lines nevertheless shows that he adopted the elements of Lamarck’s tree model in order to surmount it.

The interpretation of his diagram as a traditional tree motif seemed obvious. It was taken as a tree all the more when, twenty years later in the Origin of Species, Darwin portrayed the tree of life in a sequence that is one of the most literal parts of all of his texts. Similar to the process of the growing of a tree, Darwin evokes “the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications.”12

The elements of graphic representations of evolution that Darwin added to the Origin of Species seemed so close to the early sketches that there could be no doubt about the tree structure of this figure. This diagram, that—aside from Copernicus’s orbits of the planets—is perhaps the most influential visual representation ever developed by natural science, was a model of the totality of nature and its transformational processes. The rising, broken lines show how the species diverge over a great period of time; in smaller units of time the horizontal zones show in exemplary fashion how, over tens of thousands of generations, they split up and develop, but also become extinct.

In his pages and pages of commentary, Darwin left no doubt that the diagram was meant to be a pictorial symbol of a nature that, in her limitless contingency, can be described only by means of a visual model. The most consistent description of nature does not deal with her directly, but with her diagrammatical visualization.13

The diagram was indeed taken to be a tree. By 1866 at the latest, when Ernst Haeckel changed the lines of the diagrams into trunks and boughs, the tree model had won. Although it produced critics from the beginning, in 2003 an entire issue of Science was dedicated to Darwin’s “Tree of Life, a cornerstone in evolutionary theory that, as well as classifying organisms, has the potential to make sense of all biology.”14

But a small problem still remains. Darwin, while describing the diagram, makes no mention at all of the tree motif; and on the other hand, he is at pains not to mention the diagram when conjuring up the tree of life in a metaphorical way. This semantic gap intensifies when looking back to the early sketches.

The Coral Models

These drawings do not show trees, but corals. At the top of both sketches, Darwin has recorded the following succinct remark: “The tree of life should perhaps be called the coral of life.”15 In the image of coral, the fossils of extinct species received a striking visual form: they were to be interpreted as the dead trunk. Darwin thereby possessed a model of evolution that was able to symbolize at a glance the separation of living and extinct species.

Another no less important motive for replacing the model of the tree with one of coral was added. Even the second sketch of a coral already shows off-shooting branches more reminiscent of a bush than of a tree. The ramifications of Darwin’s third sketch seemingly want to proliferate not only upward, but in all directions. The richness of random movements, as described in this image of the coral, testifies to evolution as a free struggle for existence much better than the hierarchy of trees does. So coral is not only capable of mediating the image of evolution as a battle painting with living victors and fossilized dead in a vivid manner, but, with its anarchic form, it also stands for a free kind of growth. In this, it could correspond to the “principle of chance” that Darwin believed works in nature.

The Iconology of the Coral

However, there must have been a particular reason why Darwin was inspired by corals and reefs as a model of evolution. Darwin’s first publication, The Structure and Distribution of Coral Reefs (1842), contains passages of description that come close to veneration: “… everyone must be struck with astonishment, when he first beholds one of these vast rings of coral-rock, often many leagues in diameter, here and there surmounted by a low verdant island with dazzling white shores, bathed on the outside by the foaming breakers of the ocean, and on the inside surrounding a calm expanse of water, which, from reflection, is generally of a bright but pale green colour.”16

Darwin is even more impressed by the miraculous-appearing strength of the soft corals: “The naturalist will feel this astonishment more deeply after having examined the soft and almost gelatinous bodies of these apparently insignificant coral-polypifers, and when he knows that the solid reef increases only on the outer edge, which day and night is lashed by the breakers of an ocean never at rest.”17 The corals gave Darwin the opportunity to pacify the conflict between the ocean’s force and the land. However tiny, biological activity had been superior to every mechanical force. The coral’s miles-long construction, erected over thousands of years, arisen from a host of tiny processes, seemed to Darwin like cathedrals of evolution.

With his hymn to the coral, Darwin takes up one of the longest-discussed and most prominent topics of natural metaphorics. Even since antiquity, corals have been of great importance, being used as talismans in Christian cults as well as in natural philosophy. The coral was able to symbolize the whole world because it seemed to be meant for two spheres and elements: the water and the air. Appearing as soft and shimmering polyp and plant when under water, it hardens to precious stone in the sun. Because of this double destiny, the coral has been adored since antiquity. Ovid described its adaptability in the oft-cited lines: “The coral still remains with its same nature: / they harden when breathing air and what has been branches under water / becomes, once relieved of the water, stiff stone.”18

In this tradition, the coral appears as an epigraph of nature that has made peace with humankind. With its reconciliation of ocean and land, the coral seems to present a counterimage to the destructive forces of nature as a whole. For instance, Pietro da Cortona’s painting The Coral Fisherman shows a Triton presenting water coral to a land nymph as a symbol of marriage between ocean and land. Thus the coral becomes a symbol of peace and harmony between humankind and a kind of water-nature, which, instead of dying, is transformed into a magnificent gift when exposed to the air.19 Since it was regarded as a symbol of metamorphosis more generally, coral was used to carry out particularly precious and artificial transformations, as in this combination of a nautilus shell and a coral. Able to mutate from a living creature of the ocean into a very beautiful mineral in air, corals have been a preferred collector’s item.20

In the nineteenth century, this admiration for the coral increased in many ways. Among the most popular books of natural history was Karl Gottfried Wilhelm Vollmer’s Das Wunder der Urwelt (The wonder of the primeval world), published in 1880, which went through more than fifty editions and was translated into several languages. Furnished with a multitude of woodcuts, the book celebrated the power of the weak coral, which built entire reefs and seamounts by working untiringly in the shadows of the sea, thus decisively contributing to the artistic formation of the face of the earth. It is obvious that this eulogy to the industrious little polyp contained a metaphoric praise of democracy as a political form.21

This characteristic trait is laid out in Jules Michelet’s opus La Mer, published in 1861, which made a major contribution toward transforming the existing fear of the ocean into admiration for the gentle “mother nature” of the sea. It initiated almost a cult of the coral. In the central chapter of the book dedicated to this species, Michelet never grows tired of transferring his soft spot for the polypian shadow beings onto the coral and of conjuring up their mutual felicity. Working untiringly and eagerly, they appear as creators of colossal edifices: architects and artist-gods of the highest quality possible, at the same time existing in modest harmony and beauty: “All sculptors would admire the forms of this magnificent art.”22

In the nineteenth century this admiration for the coral was enhanced by the fact that it became a part of a rising passion for aquariums, which had conquered England and then France starting in the 1850s. For the open-mouthed spectators, who regarded the aquarium as the model of all analysis of the living, the interior of a small, inexplicable, mystically colored world was suddenly revealed, bearing corals as especially spectacular forms.23

From Corals to Trees

Considering this tradition of the coral as a symbol of the totality of nature, of peace between nature and man, of modern democracy, and of transmutation, it is by no means surprising that Darwin chose the coral as a model of nature and evolution. When formulating the theory of natural selection for the first time and overcoming the traditional tree model, he could not have chosen a more fitting species as a symbol of the survival of the fittest than the weak little coral resisting the sublime powers of the ocean and creating areas of peace.

The question of why Darwin shifted from the coral model to the tree motif is all the more pressing. The reason for his change of mind was his panic when he realized in June 1858 that Alfred Russel Wallace, who was fourteen years younger, seemed to be formulating his theory of evolution on his own and even surpassing him. Darwin began dealing with the two articles Wallace had written in 1855 and 1856, in which Wallace had used the metaphor of the oak tree to show clearly the affinity between the species and their evolution.24 Darwin summarized Wallace’s article of 1855 with Wallace’s own words, “His general summary ‘Every species has come into existence coincident in time and space with pre-existing species,’” and commented that Wallace “[u]ses my simile of tree.”25

A tiny, scarcely visible drawing in the margin of Wallace’s text, which consists of a simple forking branch, builds a bridge back to the inconspicuous little drawing in Darwin’s notebook B of 1837, which is presented upside-down here. In this situation of competition in which the tree model seemed to be succeeding, Darwin himself propagated this image of evolution as a tree, changing his own metaphor of the coral into a forerunner of his competitor’s tree model. In a letter to Asa Gray dated September 1857, he passed the tree motif off as his own invention: “This, I believe, to be the origin of the classification or arrangement of all organic beings at all times. These always seem to branch and sub-branch like a tree from a common trunk; the flourishing twigs destroying the less vigorous—the dead and lost branches rudely representing extinct genera and families.”26 This was the crucial moment at which the coral metaphor turned into the tree metaphor.

The Coralline Tree

The story could end here. However, Darwin seems to have been unhappy about his tree fixation, which he had put forward against his true conviction. He thought of alternatives to the tree that would better demonstrate the anarchic abundance of variety: “Tree not good simile—endless piece of seaweed dividing.”27 The idea that seaweed could be a symbol of the whole of nature justifies calling Darwin a genius of imagination.

The same impression arises when looking back at the Amphiroa Orbignyana. With its ramifications, it bears atmospheric similarities to the diagram of the tree of life. The branch on the right makes one even more suspicious of the connection. Putting the branches on top of each other, the outline of the coral or seaweed is roughly congruent with the graphic of species I in figure 5. The individual parts of the Amphiroa Orbignyana form lines of pearls that branch out; Darwin must have had this phenomenon in mind, since it fit beautifully with his concept of marking the lines of evolution with points and lines. By doing so, Darwin obviously smuggled a variant of the coralline alternatives to the tree into his model of the whole of the nature.

Obviously, Darwin used a rough drawing of the Amphiroa Orbignyana, which was then transferred to the plate and then printed in reverse. That Darwin possessed such drawings is suggested by letters to physiologist William Benjamin Carpenter, in which Darwin talks of corallines, articulata, and mollusks that he and the artist Samuel William Leonard were sketching: “When I was drawing with Leonard, I was so delighted with the appearance of the objects, especially with their perspective, as seen through the weak powers of a good compound Microscope that I am going to order one.”28

We can conclude that Darwin did not turn his back on the natural-philosophic tradition, but completed it. Darwin saw in the coral all the qualities that had been linked to it in premodern natural philosophy. For him, it was the symbol of all life, which was capable of resisting everything that was mechanical and was able to solve the conflict between the sea and the land. For Darwin, the coral and its products belonged unquestionably to the arts: “Let the hurricane tear up its thousand huge fragments; yet what will this tell against the accumulated labour of myriads of architects at work night and day, month after month. Thus we do see the soft and gelatinous body of a polypus, through the agency of the vital laws, conquering the great mechanical power of the waves of an ocean, which neither the art of man, nor the inanimate works of nature could successfully resist.”29 With its untiring activity over long periods of time, but according to Darwin in effective steps, the coral has built enormous constructions, more impressive than the greatest ancient ruins. Darwin also compares the circular reefs that wrap around an interior reef needle (the “needle” in the center of a coral ring) to a work of art: “Can any thing be more singular than this structure? It is analogous to that of a lagoon, but with an island standing, like a picture in its frame, in the middle.”30

All this is not insignificant. For Darwin, the coral was part of a semantically laden and artistically enchanted world. If Darwin’s original coral model of evolution had been noticed, social Darwinism could hardly have referred to him. As I hope to have shown, a theory of nature will hardly be able to understand objects like the Amphiroa Orbignyana in their fullest sense if it does not face this semantic power. Anyone who examines how Darwin dealt with the coral will consider the current struggle between anti-Darwinian creationists and Darwinian evolutionists as a product of a post-Darwinian impoverishment.31 Not the tree, but the coral, as Darwin originally suggested, might be the coming symbol of nature.32

© Bard Graduate Center, Horst Bredekamp.

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