This is the second of several excerpts from my book Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral. This is from Chapter Two. Series explained below; go here for context on this repub experiment.
2. Rumble at Glen Roy
© David Dobbs, all rights reserved
Like any decent scientist or curious human, Louis Agassiz could not resist seeking patterns in what he saw. And like Cuvier, he believed the taxonomic evidence showed no sign of transmutation and proved that species “changed” only by a series of mass extinctions and subsequent re-creations — a sort of global delete-and-replace pattern left by a God who revised his own work.
This vision raised an obvious and troubling question: What did God use for these waves of extinction and creation? The story of Noah’s flood could account for only one such revision (and hardly accounted for fish extinctions), and the fossil record showed at least several successions of similar species. This suggested either a continuous progression or (if you were determined to see waves of extinction and re-creation) at least several massive, worldwide revisions. If you wanted to buttress creationism with science, as Agassiz did, you had to come up with more than just a single catastrophe.
Agassiz soon stumbled on what seemed a likely answer. In one of his greatest contributions, he pioneered the idea of the Ice Age, expanding it from glacial studies in the Alps and receiving primary credit (albeit disputed) for a concept that would explain a huge range of phenomena. His development of the theory also showed a penchant for drama and controversy that would emerge repeatedly thereafter.
In the summer of 1836, Jean de Charpentier, a mining engineer and amateur geologist who ran a salt mine in the Rhone Valley, invited Louis to vacation at his house in nearby Vaud. He said he had some geology he wanted to show him. Louis had heard that Charpentier believed that the grinding action of glaciers was responsible for turning the Alps and surrounding areas into such grooved terrain, and that glaciers also created the landscape features that we now know of as glacial moraines and erratics — the fields of detritus and huge boulders, respectively, that in many areas seem to have fallen from the sky, so detached are they from any likely point of origin. Charpentier, observing the ice rivers still carving down many Alpine valleys and puzzling over the many erratics in the Rhone Valley, became convinced that larger glaciers had covered most of the Alps at some prior, colder time, carving deep valleys and leaving boulders and moraines across the region. This idea had actually been around for a few decades. But no one had investigated it as thoroughly as Charpentier.
In a series of hikes that summer, Charpentier slowly sold the idea to Louis, who was initially quite skeptical. Agassiz slowly overruled his reservations because, as many would experience in the years ahead, the glacial theory provided convincing explanations — a shock of recognition and clarity — for numerous landscape phenomena. It radically altered one’s view of the earth. Striated and polished rocks, boulders left in strange places, gravel ridges, block-shaped depressions, and countless other oddities all suddenly made sense. The Ice Age was one of those ideas that make everything fall into place and let you see things you hadn’t seen before. In that sense, it met the standard we generally use today for a useful theory: It provided the most plausible explanation for a breadth of data.
As Charpentier showed him around, Louis found the theory increasingly attractive, and when he got back to Neuchâtel he pondered it excitedly. Glaciers, he realized, could explain not only scratched rocks, erratic boulders, and kettles (the depressions where ice blocks melted), but the question of how God cleaned house and rebuilt. They were “God’s great plough,” as he would put it in his lectures, a biological eraser as effective as any flood, and their repeated, massive occurrences in successive Ice Ages (the term Eiszeit was coined by his friend Schimper as they discussed what Agassiz had seen) explained the gaps that he and other paleontologists had found in the fossil record. In these Ice Ages, he theorized, glaciers covered not just the mountains but all of temperate earth in huge sheets, reshaping the land and extinguishing almost all life.
It was a brilliant insight, and Agassiz’s application of it to the fossil record was especially inspired. This creative extension would have thrilled his mentor Cuvier. It ingeniously reconciled creationism with recent scientific principles such as uniformitarianism (also known as gradualism), which was the seminal argument, first made by geologist James Hutton in 1795 and then brilliantly deployed by Charles Lyell in his 1830 Principles of Geology, that natural science must base its theories on forces presently and observably in effect. Uniformitarianism was the latest step in science’s march toward empiricism — that is, toward theories based on demonstrable ties to observation. Western scientists (or “natural philosophers,” as they were called then) had practiced an increasingly self-conscious devotion to empiricism since Galileo’s time, and empirical principles had been especially boosted in Britain by the philosophy of John Locke in the 1700s. Hutton’s uniformitarianism was merely the geological expression of these principles. Just as Newtonian math rationalized physical phenomena in the 1600s and chemistry rose in the 1700s to replace alchemy, the gradualism of the 1800s offered a rational alternative to the prevailing catastrophism, which relied on spectacular, hypothetical one-time past events to explain the landscape.
This march toward empiricism — that is, toward a reliance on what could be shown through observation or experiment — had repeatedly threatened religious views of the world, for observations sometimes clashed with religious explanations. Thus Galileo paid dearly for elaborating Copernicus’s observations proving that the Earth circled the sun, rather than vice-versa. Louis’s Ice Age theory, however, posed no such threat. Instead, it reconciled gradualism with catastrophism, for it provided a catastrophe you could observe in action, in small scale, in every alpine glacier. Thus it seemed to support a central creationist dynamic with evidence drawn from direct observation. In a career built on reconciling empirical method with creationist vision, the Ice Age was Louis Agassiz’s first great stroke.
Louis lost no time developing the idea. He immediately began buttressing it with his own observations and set about making the theory his. A year after visiting Charpentier, at the July, 1837 meeting of the Swiss Society of Natural History, he gave a talk announcing his discovery that in a prehistoric Ice Age, a huge sheet of ice had covered the earth from the North Pole at least as far south as the Mediterranean, and that this accounted for much of Europe’s physiognomy. This lecture significantly extended Charpentier’s theory, which mainly concerned central and western Europe.
Louis began spending most of every summer in the Alps studying glaciers. In his frequent travels around Europe to look at fossil fish, he took every chance to seek more evidence of glaciation and to publicize his new ideas about the Ice Age. His lectures and field trips fascinated everyone, spreading his reputation spectacularly. (For Agassiz, a visit and a field trip threw far more influence than any number of published papers — one reason he talked more than he published.) After one of his visits to England, the British biologist Edward Forbes wrote him, “You have made all the geologists glacier-mad here, and they are turning Great Britain into an ice-house.” Though his ideas met some resistance in Britain because they contradicted Charles Lyell’s flood-based theories, Lyell himself as well as other leading geologists and naturalists soon agreed that Louis’s ice accounted for much of what they saw in the landscape. In a country thick with geologists, Louis’s Ice Age insights made him one of the most renowned,.
One of his more intriguing triumphs came from applying the Ice Age theory to the mystery of the “parallel roads” of Glen Roy. These “roads,” so called because local lore pegged them as ancient trade or hunting paths, consisted of a series of three parallel terraces running along both sides of the Scottish valley of Glen Roy. Each terrace is roughly sixty feet wide and dead level. The highest lies 80 feet above the middle one, which runs about 200 feet above the lowest. British scientists had been puzzling over them since the 1700s. Given the roads’ lack of slope and sand-and-gravel composition, most scientists agreed they were shorelines. But how did lake or seawater reach several hundred feet above the valley floor and almost two thousand feet above sea level? The puzzle drew guesses from all quarters.
Passing judgment on Glen Roy, in fact, had been a sort of rite of passage for British geologists for almost a century. Charles Darwin took his turn in 1838, when he visited it not long after returning from the Beagle voyage. “I wandered the mountains in all directions,” he wrote Lyell, “and … without any exceptions, not even the first volcanic island [he saw on the Beagle voyage], the first elevated beach, or the passage of the [Andean] Cordillera, was so interesting to me as this week. It is by far the most remarkable area I ever examined.” In the Andes three years before, Darwin had found seashells at 8000 feet, convincing him that those mountains had risen from the sea, and he had been fascinated ever since with geological uplift and subsidence. Even as he walked Glen Roy, this fascination was leading Darwin to the subsidence theory of coral reef formation that Alexander Agassiz (just three years old at this point) would grapple with years later.
Here at Glen Roy, however, Darwin saw not subsidence but uplift. Specifically, he theorized that the entire valley had once been at or under sea level, and that the three sets of terraces were former shores that rimmed a saltwater sea or inlet as the land rose in three subsequent surges. This fit into a larger theory of raised sea levels that Charles Lyell had posited to explain phenomena such as erratic boulders, moraines, and other out-of-place items, and it fit nicely into Darwin’s own obsession with rising landforms.
Darwin promptly wrote a 90-page paper detailing this theory. It was his first paper of length — the first time he’d applied his considerable powers of theoretical imagination and published the results — and it brought him much satisfaction and recognition. The Royal Society accepted the paper early in 1839 and elected him a Fellow a week later. The paper secured his entry, independent of his Beagle investigations, into the upper strata of British science.
A year later, Louis Agassiz toured Britain for the third time to examine fish fossils and talk Eiszeit. On visiting Glen Roy he declared that it was not a raised seabed but a valley that had been blocked at its ends by ice during the Ice Age, creating a freshwater lake that left shorelines (the “roads”) as it drained in three warming events — somewhat like a filled tub with its plug thrice pulled and replaced. This explanation had roots only marginally less speculative than Darwin’s, rising as much from Louis’s belief in glaciation as Darwin’s did from his belief in uplift. However, Louis cited substantial evidence that Darwin had either underplayed or overlooked — a complete absence of marine fossils, for instance, which Darwin had noted but chosen to ignore, and signs of ancient outgoing streams that Darwin had missed.
Louis’s better-supported argument triumphed, though only after a debate that burned hot at first and then flared sporadically over the next two decades. The originality of Agassiz’s argument impressed everyone immediately, but in Britain it initially convinced only a few. Fortunately for Louis, these few included some of the country’s most prominent scientists, including William Buckland, an Oxford professor and mentor of Lyell who wrote two papers supporting Agassiz’s view. Others came around more slowly. Lyell and Sedgwick, for example, initially resisted Louis’s Glen Roy account even though they generally accepted his Ice Age theory. But as observations made by other investigators over the next two decades seemed to support Agassiz’s explanation more than Darwin’s, most of the doubters, including Lyell, came to agree with him about Glen Roy. Darwin eventually did as well .
Louis’s insight at Glen Roy accelerated acceptance of his Ice Age theory. It also greatly distressed Darwin, who watched in agony as his first child, as he once called his Glen Roy theory, stumbled and fell. He suffered less from shame of error than from horror at the realization that he had speculated too freely. A brilliant, imaginative theorist all his life, Darwin was at this stage still learning to rigorously test his creative ideas. (He was 31 when he published the paper.) His shorter coral reef paper, presented in 1837 to the Geological Society, had met little criticism precisely because he had tested it sharply against the available evidence before publishing. (It helped too that though he had seen only a few coral reefs, few Brits had seen more.) Now he feared that he had grown too bold. He feared in particular he had too readily dismissed a shortage of supporting evidence, such as the lack of marine fossils at Glen Roy, as a “meaningless absence.” At a time when he was struggling to test and develop his theory of natural selection — a view he knew would be profoundly controversial — the thought that he was using faulty logic terrified him. He had left himself out on a limb, and Louis Agassiz had sawn it off. What faults might he be overlooking in his nascent evolution theory?
These doubts did not hit Darwin all at once. They accumulated sickeningly over a twenty-year span. For a time he tried to fend Agassiz off, arguing that while both his seashore theory and Agassiz’s glacial-lake theory had problems, his had fewer. But as most scientists moved to Agassiz’s view, Darwin slowly let go of his theory. After two decades he finally surrendered completely when a comprehensive review by the respected geologist Thomas Jamieson found for Agassiz. Even then, he wrote Lyell, he was pained: “I am smashed to atoms about Glen Roy.… My paper was one long gigantic blunder. Eheu! Eheu!”
Years before, however, he had surrendered to Agassiz on the larger point of glaciation, and as often occurs, the defeat taught more to the loser than the winner. In 1842, at the time Louis was turning England into an ice house, Darwin had undergone a sort of Eiszeit conversion when he took a long walk in Wales and, in an area he had walked a decade before with Adam Sedgwick, saw signs of glaciation everywhere. He was stunned that he could have missed them before. “Eleven years ago I spent a whole day in [this] valley,” he wrote a friend, “where yesterday everything but the ice of the glacier was palpably clear to me, and then I saw nothing but plain water and bare rock.” As he later recalled in his autobiography, “Neither [Sedgwick nor I] saw a trace of the wonderful glacial phenomena around us [on the earlier trip]; we did not notice the plainly scored rocks, the perched boulders, the lateral and terminal moraines. Yet these phenomena are so conspicuous that … a house burned down by fire did not tell its story more plainly than did this valley.”
Thus Louis’s glacial theories brought Darwin an epiphany on one hand and, several years later, humiliation on the other. It was the first in a strange, irony-laced series of encounters between the minds and legacies of these two men. Their reactions to these early clashes are revealing. For Darwin, the explanatory power of Louis’s larger glacier theory, witnessed so starkly on his Wales walk, confirmed a vital lesson: Productive observation actually rises from sound theory — not the opposite, as Louis would assert. A mere idea could transform the world, making palpable features and dynamics previously hidden. Darwin’s later long, slow defeat on Glen Roy, on the other hand, led him to test his theories more rigorously and hold himself to a higher level of proof. This lesson, added to Darwin’s habitual caution, doubtless contributed to his 23-year hesitation in publishing his theory of evolution. But both it and the revelations he saw in the Eiszeit hypothesis helped Darwin forge the distinctive theoretical approach — imaginative in spawning ideas, rigorous in testing them — that let him develop the evolution theory that would negate much of Louis’s work.
Thus Darwin learned both boldness and caution from his encounters with Louis’s Ice Age work. Louis, however, took from Glen Roy an opposite lesson: He felt emboldened to push his speculative theories ever further. At Glen Roy, Darwin had stumbled, collected himself, and adjusted his gait. Louis had sprung across a valley and landed safely. He would soon put so much faith in his leaps that even when his support was delusory, he would land and feel solid ground.
*This series of excerpts is an experimental act of re-publication; over the next several week I will run a dozen or so of these, partially serializing the book. Each post will stand on its own as an intriguing story within a larger context: the struggle of some of history’s smartest and most determined people, including Charles Darwin, to figure out how to do science — to look at the world accurately, generate ideas about how it works, and test those ideas in a way that gives you reliable answers. This was usually (certainly not always, as we’ll see) a polite debate. Yet it was also, always, a high-stakes war about what science is, and that war continues today. In this case it revolved around two of the 19th century’s hottest scientific questions: the origin of species, and the origin of coral reefs.
Read what Oliver Sacks and others have to say about Reef Madness.