Written in Stone: Evolution, the Fossil Record, and Our Place in Nature

by Brian Switek

  FIGURE 11 - Henry de la Beche’s cartoon of the “Awful Changes” that would occur if, according to Lyell’s ideas about the unfolding of the history of life, ichthyosaurs returned to the world during some future time.

  This attempt to obscure any notion of progression in the fossil record seemed so absurd that Lyell’s colleague, geologist Henry de la Beche, lampooned it in a widely circulated cartoon. Entitled “Awful Changes—Man Found Only In A Fossil State.—Reappearance of Ichthyosauri,” the scene depicted “Professor Ichthyosaurus” astride a podium apprising his class of a fossil human skull: “A lecture—‘You will at once perceive,’ continued Professor Ichthyosaurus, ‘that the skull before us belonged to some of the lower order of animals; the teeth are very insignificant, the power of the jaws trifling, and altogether it seems wonderful how the creature could have procured food.’” Even as the idea of evolution remained controversial, Lyell’s cyclical hypothesis for the pattern of life’s history could not mask the very real succession of fossil creatures paleontologists were beginning to uncover.

  There had to be some other explanation for this pattern in the rocks, some kind of natural law that regulated the appearance of organisms through time. Over the previous several hundred years naturalists had, bit by bit, substituted the direct actions of a deity with natural mechanisms (albeit ones put in place at the moment of Creation). A literalistic interpretation of Genesis was not sufficient to gain true knowledge of nature, but naturalists feared what they might find when considering the “species problem.” What was true for the origins of other animals would be true for our kind, too, and the prevailing religious sentiments of the day made naturalists uneasy about this concept. By the time Lyell published the first volume of Principles of Geology such a mechanism was still wanting, but it would be one of his own pupils who would supply it.

  Moving Mountains

  The theory of the transmutation of species . . . has met with some degree of favour from many naturalists, from their desire to dispense, as far as possible, with the repeated intervention of a First Cause, as often as geological monuments attest the successive appearance of new races of animals and plants, and the extinction of those pre-existing. But, independently of a predisposition to account, if possible, for a series of changes in the organic world, by the regular action of secondary causes, we have seen that many perplexing difficulties present themselves to one who attempts to establish the nature and the reality of the specific character.

  —CHARLES LYELL, Principles of Geology, Volume 2, 1832

  In the evening hours of January 19, 1836, at the height of the Australian summer, a young naturalist reclined on the bank of a sun-warmed river near Wallerang to ponder the weird and wonderful creatures of the great island continent. Earlier in the day he had taken part in a kangaroo hunt, and that afternoon he had seen one of the strangest of all Australia’s creatures, a duck-billed platypus, both of which were entirely unlike the animals he was familiar with from Europe. Reflecting on such animals, he could not help but think of Australia as a place created separately from the rest of the world. Later that night he wrote in his journal:An unbeliever in everything beyond his own reason, might exclaim “Surely two distinct Creators must have been [at] work; their object however has been the same & certainly the end in each case is complete.”

  But such a claim was obviously absurd, and the presence of a more familiar creature underlined the unity of design in nature. Lying in wait in a little sand pit near the riverbank was an antlion, a vicious insect larvae that sprays passing ants with sand until they tumble down the walls of the pit into its waiting jaws, and in it the naturalist again saw the imprimatur of the Creator: Without a doubt this predacious Larva belongs to the same genus, but to a different species from the Europaean one.—Now what would the Disbeliever say to this? Would any two workmen ever hit on so beautiful, so simple & yet so artificial a contrivance? It cannot be thought so.—The one hand has surely worked throughout the universe. A Geologist perhaps would suggest, that the periods of Creation have been distinct & remote the one from the other; that the Creator rested in his labor.

  This was the young Charles Darwin, pondering the handiwork of the Creator toward the end of his five-year journey around the world on the HMS Beagle.15 At twenty-seven, Darwin was a recent Cambridge graduate just one step away from becoming an Anglican parson, and he was an adherent of the English brand of natural theology that saw the will of God in all of nature. All he could ask for when he got home would be a quiet little country parish in which he could deliver sermons on Sunday and build his natural history collection during the rest of the week.

  Enlightened appreciation of nature had long been important to Christianity. During the second century there appeared a popular text in Greek called the Physiologus in which nature confirmed the raw power and creativity of God while serving as an allegory for the teachings more explicitly stated in the Bible.16 The trick was preventing curiosity about the natural world from turning into something pagan. Myth and reality were often bound up together, especially in representation of what existed in far off lands, and during the Middle Ages it became fashionable to store up collections of the weird and wonderful productions of nature. Cataloging and collecting became an activity of empire justified by the need to fully appreciate the Creation, and eventually fairy tales gave way to a natural theology that relied more on the interpretation of nature’s aesthetics. By the time Darwin sailed around the world in the early nineteenth century there was nothing untoward in a priest’s being preoccupied with collecting beetles, flowers, or fossils. Such activities only supplemented intellectual lessons about God’s work.

  Given that Darwin’s father was a physician and his brother had already taken the same path, however, medicine had been his initial choice of profession. Darwin had cut his teeth as an assistant to his father during house calls in 1825, when he was 16 years old, and in the fall of that year he started his formal training at the University of Edinburgh. He quickly learned that he was not cut out for medicine. The demonstrations in the operating chamber before the advent of anesthesia were horrible spectacles of gore and violence that he could not bear. He remained at the school until 1827 before his father grew frustrated with his lack of progress and made him reappraise his options.

  But Darwin’s time at Edinburgh had not been wasted. Not only had he learned the finer points of taxidermy from a freed slave, John Edmonstone, but he also became heavily involved in the natural history clubs there. In fact, it was in the school’s Plinian Society that he presented one of his first scientific discoveries: that what had previously been thought to be some kind of spore in oysters were in fact the eggs of a skate leech. During this time Darwin also studied under the Scottish naturalist Robert Edmund Grant, an advocate of Jean-Baptiste Lamarck’s view of evolution and the transmutationist speculations presented by Darwin’s grandfather, Erasmus, in verse. As Grant and Darwin walked to the seashore together the elder naturalist sang the praises of the French transformists and pondered how all life had arisen from a simple common ancestor. (Hence, Grant’s preoccupation with sponges, regarded as among the most primitive of organisms.)

  Darwin was an attentive student of Grant’s, assisting the elder naturalist with research and practicing French so that he, too, could understand what authorities on the continent were talking about, but he was more in awe of Grant than a direct adherent to his views. That species were mutable was still a highly controversial idea. Naturalists were free to consider the heretical notion on their own time, but they could expect fierce public opposition from the social conservatives that controlled the country (as Grant himself most certainly did).

  But despite Darwin’s aptitude as a budding naturalist he still had to choose an occupation that would gain him the respectability that could never be achieved by searching tide pools and stuffing birds. Since he had neither interest, nor the temperament, for becoming a soldier or a lawyer, this left the Church of England as a relatively safe, easy
, and honorable way for him to find his place in society. Although he came from a liberal Whig family full of Unitarians, and would be entering a profession dominated by social conservatives, as long as he did his duty on the Lord’s Day he could hunt birds and study sea slugs as much as he liked during the rest of the week. His habits, a liability in the pursuit of almost any other career, would not be a hindrance in the Anglican Church.

  Since Darwin’s cousin, William Darwin Fox, was already at Christ’s College at Cambridge, it was decided that he should do the same. (At the very least, there would be someone there to make sure he was not spending too much time away from his studies.) He started afresh there in early 1828, and though Darwin did prefer his hobbies, especially his new avocation of beetle collecting, he did not wash out of Cambridge as he had Edinburgh. In early 1831, as planned, he passed his final exams and attained his Bachelor of Arts degree. The question was what was to come next, and Darwin would have to wait in Cambridge until June for graduation. He used this time to simultaneously feed his interest in nature and prepare for taking the holy orders.

  The Anglican theologian William Paley’s Evidences of Christianity had been required reading for the finals, and Darwin was so struck by it that picked up Paley’s Natural Theology during his spring break. No other book could have suited Darwin better. In The Evidences of Christianity Paley was primarily interested in standard proofs of God such as miracles; in Natural Theology he turned his attention to nature. According to Paley the whole of nature was fine-tuned and harmonious, and each intricately designed part worked with the others to achieve a designed purpose. He summarized this view at the outset in what would become known as the watchmaker argument:In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there, I might possibly answer, that, for any thing I knew to the contrary, it had lain there for ever: nor would it perhaps be very easy to shew the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be enquired how the watch happened to be in that place, I should hardly think of the answer which I had before given, that, for any thing I knew, the watch might have always been there. Yet why should not this answer serve for the watch, as well as for the stone? Why is it not as admissible in the second case, as in the first? For this reason, and for no other, viz. that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that, if the several parts had been differently shaped from what they are, of a different size from what they are, or placed after any other manner, or in any other order, than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use, that is now served by it.

  Clearly the watch had been designed, its many parts working together for one purpose, whereas the stone was just some uninteresting pebble. (I can only imagine what a geologist would say to this latter point.) Applied to nature, Paley’s argument was similar to that which Georges Cuvier had made about the stability of species. Organisms had to be organized in a precise fashion, and any change to those anatomical plans would cause a disequilibrium in which the organism would break down. Whereas Cuvier demurred on how these forms were made, however, Paley had no qualms about attributing their creation to God. The intricate nature of living things attested to what Christians took by faith.

  Darwin was delighted by this.17 Paley’s view of a benevolent, carefully designed nature perfectly married his Cambridge studies with his ambitions to be a clergyman naturalist like his teacher John Henslow. Henslow, a botanist at the college, was an enthusiastic supporter of students who took an interest in natural history, and Darwin’s zeal for the subject matter made them close friends. Just as with Grant, Darwin supplemented the formal parts of his study by discussing natural history on long strolls with Henslow, and did so often enough that Darwin became known as the “man who walks with Henslow.” During the months that he was required to stay at Cambridge Darwin saw Henslow frequently, and through his combination of clerical and natural knowledge Henslow seemed like the perfect person for Darwin to emulate.

  But Darwin was not ready to jump into the service of the church just yet. Among the other books he read while waiting for graduation day was the Personal Narrative of the German naturalist Alexander von Humbolt. Despite its dull title, the massive volume was an exciting account of the natural wonders of South America, and it sparked Darwin’s interest in the tropics. There was so much to see outside England, and as much fun as scrounging for beetles in the English countryside was, he imagined how much grander it would be to find dozens of new varieties on a far-off continent! He did not have the funding for such a long voyage, but a trip to someplace a little closer to home did not seem out of the question. Tenerife, off the northwest coast of Africa, seemed like the perfect destination. Darwin was able to interest Henslow and three other students in participating, too, and his reticent father agreed to underwrite the trip. (After all, his brother Erasmus toured the European continent when he graduated.) Darwin talked almost incessantly about the trip and could not wait to go.

  To get Darwin up to speed before the trip, Henslow introduced him to another cleric-cum-naturalist, Adam Sedgwick, who was an expert on geology. Darwin began attending Sedgwick’s lectures that spring and was exhilarated by just how much there was left to discover, and he took as avidly to mapping the geology of the countryside around his family’s home as he had to beetle collecting. The expedition to Tenerife could not leave soon enough.

  Darwin remained steadfast in his ambition, even as most of the members of the trip backed out, including Henslow, but the unexpected death of the last of the willing adventurers stalled Darwin’s plans. It was now apparent that if there was going to be any expedition at all he would have to go alone. Conflicted, Darwin rode home to the family manor, but when he arrived there was a fat envelope for him from Henslow. It was an invitation to an even grander adventure; a potential slot on a survey to South America on the HMS Beagle.

  The Royal Navy ship the HMS Beagle had been built in 1820, but other than taking part in the celebration of the coronation of King George IV it had simply sat at the docks, unused. An expedition launched in 1826 would give it new purpose. South America was open for trade, and knowledge of the continent’s waterways was essential for British merchants to compete with other Europeans. The Beagle was fixed up and refitted to accompany the HMS Adventure on a survey of the waters and coast of southern South America, a vast expanse of mountains and sparse grasslands.

  It was not an easy journey. The isolation faced at sea proved to be too much for the captain of the Beagle, Pringle Stokes, who shot himself just over two years into the trip. In the wake of this tragedy the ship came under the command of a young officer named Robert FitzRoy. After he took over, FitzRoy spent a great deal of time trying to recover a small boat that had been stolen by some of the native Fuegians and, in his frustration, FitzRoy took several of their children hostage. They were to be educated in England and returned as missionaries, it was decided, and while the official reason for the second voyage of the Beagle was to continue the hydrographical survey, an equally important impetus was the return of the abducted children to England.

  Given that the fate of the Beagle’s earlier captain, FitzRoy knew all too well the way the isolation of a long sea voyage could prey on the mind. He cast about for a suitable gentleman companion to accompany him. Leonard Jenyns, a clergyman naturalist, was among the first to be tapped, but he demurred, as did Henslow. Both were already established and had other duties at home. The offer trickled down to Darwin through his connection to Henslow, and he seemed like a perfect choice because he was not married and not yet a member of the clergy. After convincing his father that the trip would be beneficial, on December 27, 1831, twenty-two-year-old Charles Da
rwin left London for South America and points beyond.

  It was not a pleasant trip for Darwin (at least while he was at sea). Lacking a bunk, he slept in a hammock strung high above the floor of his cabin, and he constantly battled with seasickness. Still, Darwin’s onshore journeys made the entire ordeal worth while. The wonders of South America were open to him, giving him the chance to make new discoveries in a place most of the naturalists back home had never been.

  After reading the first volume of Charles Lyell’s Principles of Geology the young naturalist was enthusiastic about fieldwork in a distant land. Henslow had warned Darwin not to take Lyell too seriously, as Lyell was proposing a dressed-up version of Hutton’s old ideas that did not leave room for great catastrophes to shape the earth, but Darwin drank deeply from the pages of Lyell’s work. It made more sense that the rocks of the earth should have been historically shaped by causes now in operation. Even if large scale changes seemed slow, local events could occur very rapidly.

  On the morning of February 20, 1832, Darwin was lying down in the woods around the town of Valdivia, Chile, when the ground began to shake. The earthquake was so severe that he could not stand until it was over, and when it abated he ran into the town to see people running about slanted houses that had been upright the night before. The damage was even worse in the city of Concepción, which the Beagle reached two weeks later. The city was in shambles, an enormous smoldering pile of rubble.