Bully for Brontosaurus

by Stephen Jay Gould

  Each profession treasures a classic, or canonical, version of the basic story. The paleontological “standard,” known to all my colleagues as a favorite campfire tale and anecdote for introductory classes, achieves its top billing by joining the most famous geologist of his era with the most important fossils of any time. The story, I have just discovered, is also entirely false (more than a bit embarrassing since I cited the usual version to begin an earlier essay in this series).

  Charles Doolittle Walcott (1850–1927) was both the world’s leading expert on Cambrian rocks and fossils (the crucial time for the initial flowering of multicellular life) and the most powerful scientific administrator in America. Walcott, who knew every president from Teddy Roosevelt to Calvin Coolidge, and who persuaded Andrew Carnegie to establish the Carnegie Institute of Washington, had little formal education and began his career as a fieldworker for the United States Geological Survey. He rose to chief, and resigned in 1907 to become secretary (their name for boss) of the Smithsonian Institution. Walcott had his finger, more accurately his fist, in every important scientific pot in Washington.

  Walcott loved the Canadian Rockies and, continuing well into his seventies, spent nearly every summer in tents and on horseback, collecting fossils and indulging his favorite hobby of panoramic photography. In 1909, Walcott made his greatest discovery in Middle Cambrian rocks exposed on the western flank of the ridge connecting Mount Field and Mount Wapta in eastern British Columbia.

  The fossil record is, almost exclusively, a tale told by the hard parts of organisms. Soft anatomy quickly disaggregates and decays, leaving bones and shells behind. For two basic reasons, we cannot gain an adequate appreciation for the full range of ancient life from these usual remains. First, most organisms contain no hard parts at all, and we miss them entirely. Second, hard parts, especially superficial coverings, often tell us very little about the animal within or underneath. What could you learn about the anatomy of a snail from the shell alone?

  Paleontologists therefore treasure the exceedingly rare soft-bodied faunas occasionally preserved when a series of unusual circumstances coincide—rapid burial, oxygen-free environments devoid of bacteria or scavengers, and little subsequent disturbance of sediments.

  Walcott’s 1909 discovery—called the Burgess Shale—surpasses all others in significance because he found an exquisite fauna of soft-bodied organisms from the most crucial of all times. About 570 million years ago, virtually all modern phyla of animals made their first appearance in an episode called “the Cambrian explosion” to honor its geological rapidity. The Burgess Shale dates from a time just afterward and offers our only insight into the true range of diversity generated by this most prolific of all evolutionary events.

  Walcott, committed to a conventional view of slow and steady progress in increasing complexity and diversity, completely misinterpreted the Burgess animals. He shoehorned them all into modern groups, interpreting the entire fauna as a set of simpler precursors for later forms. A comprehensive restudy during the past twenty years has inverted Walcott’s view and taught us the most surprising thing we know about the history of life: The fossils from this one small quarry in British Columbia exceed, in anatomical diversity, all modern organisms in the world’s oceans today. Some fifteen to twenty Burgess creatures cannot be placed into any modern phylum and represent unique forms of life, failed experiments in metazoan design. Within known groups, the Burgess range far exceeds what prevails today. Taxonomists have described almost a million living species of arthropods, but all can be placed into three great groups—insects and their relatives, spiders and their kin, and crustaceans. In Walcott’s single Canadian quarry, vastly fewer species include about twenty more basic anatomical designs! The history of life is a tale of decimation and later stabilization of few surviving anatomies, not a story of steady expansion and progress.

  But this is another story for another time (see my book Wonderful Life, 1989). I provide this epitome only to emphasize the context for paleontology’s classic instance of Sod’s law. These are no ordinary fossils, and their discoverer was no ordinary man.

  I can provide no better narration for the usual version than the basic source itself—the obituary notice for Walcott published by his longtime friend and former research assistant Charles Schuchert, professor of paleontology at Yale. (Schuchert was, by then, the most powerful paleontologist in America, and Yale became the leading center of training for academic paleontology. The same story is told far and wide in basically similar versions, but I suspect that Schuchert was the primary source for canonization and spread. I first learned the tale from my thesis adviser, Norman D. Newell. He heard it from his adviser, Carl Dunbar, also at Yale, who got it directly from Schuchert.) Schuchert wrote in 1928:

  One of the most striking of Walcott’s faunal discoveries came at the end of the field season of 1909, when Mrs. Walcott’s horse slid in going down the trail and turned up a slab that at once attracted her husband’s attention. Here was a great treasure—wholly strange Crustacea of Middle Cambrian time—but where in the mountain was the mother rock from which the slab had come? Snow was even then falling, and the solving of the riddle had to be left to another season, but next year the Walcotts were back again on Mount Wapta, and eventually the slab was traced to a layer of shale—later called the Burgess shale—3,000 feet above the town of Field, British Columbia, and 8,000 feet above the sea.

  Stories are subject to a kind of natural selection. As they propagate in the retelling and mutate by embellishment, most eventually fall by the wayside to extinction from public consciousness. The few survivors hang tough because they speak to deeper themes that stir our souls or tickle our funnybones. The Burgess legend is a particularly good story because it moves from tension to resolution, and enfolds within its basically simple structure two of the greatest themes in conventional narration—serendipity and industry leading to its just reward. We would never have known about the Burgess if Mrs. Walcott’s horse hadn’t slipped going downslope on the very last day of the field season (as night descended and snow fell, to provide a dramatic backdrop of last-minute chanciness). So Walcott bides his time for a year in considerable anxiety. But he is a good geologist and knows how to find his quarry (literally in this case). He returns the next summer and finally locates the Burgess Shale by hard work and geological skill. He starts with the dislodged block and traces it patiently upslope until he finds the mother lode. Schuchert doesn’t mention a time, but most versions state that Walcott spent a week or more trying to locate the source. Walcott’s son Sidney, reminiscing sixty years later, wrote in 1971: “We worked our way up, trying to find the bed of rock from which our original find had been dislodged. A week later and some 750 feet higher we decided that we had found the site.”

  I can imagine two basic reasons for the survival and propagation of this canonical story. First, it is simply too good a tale to pass into oblivion. When both good luck and honest labor combine to produce victory, we all feel grateful to discover that fortune occasionally smiles, and uplifted to learn that effort brings reward. Second, the story might be true. And if dramatic and factual value actually coincide, then we have a real winner.

  I had always grasped the drama and never doubted the veracity (the story is plausible, after all). But in 1988, while spending several days in the Walcott archives at the Smithsonian Institution, I discovered that all key points of the story are false. I found that some of my colleagues had also tracked down the smoking gun before me, for the relevant pages of Walcott’s diary had been earmarked and photographed before.

  Walcott, the great conservative administrator, left a precious gift to future historians by his assiduous recordkeeping. He never missed a day of writing in his diary. Even at the very worst moment of his life, July 11, 1911, he made the following, crisply factual entry about his wife: “Helena killed at Bridgeport Conn. by train being smashed up at 2:30 A.M. Did not hear of it until 3 P.M. Left for Bridgeport 5:35 P.M.” (Walcott was meticul
ous, but please do not think him callous. Overcome with grief the next day, he wrote on July 12: “My love—my wife—my comrade for 24 years. I thank God I had her for that time. Her untimely fate I cannot now understand.”)

  Walcott’s diary for the close of the 1909 field season neatly dismisses part one of the canonical tale. Walcott found the first soft-bodied fossils on Burgess ridge either on August 30 or 31. His entry for August 30 reads:

  Out collecting on the Stephen formation [the unit that includes what Walcott later called the Burgess Shale] all day. Found many interesting fossils on the west slope of the ridge between Mounts Field and Wapta [the right locality for the Burgess Shale]. Helena, Helen, Arthur, and Stuart [his wife, daughter, assistant, and son] came up with remainder of outfit at 4 P.M.

  On the next day, they had clearly discovered a rich assemblage of soft-bodied fossils. Walcott’s quick sketches (see figure) are so clear that I can identify the three genera he depicts—Marrella (upper left), the most common Burgess fossil and one of the unique arthropods beyond the range of modern designs; Waptia, a bivalved arthropod (upper right); and the peculiar trilobite Naraoia (lower left). Walcott wrote: “Out with Helena and Stuart collecting fossils from the Stephen formation. We found a remarkable group of Phyllopod crustaceans. Took a large number of fine specimens to camp.”

  The smoking gun for exploding a Burgess Shale legend. Walcott’s diary for the end of August and the beginning of September, 1909. He collected for an entire week in good weather. SMITHSONIAN INSTITUTION.

  What about the horse slipping and the snow falling? If this incident occurred at all, we must mark the date as August 30, when Walcott’s family came up the slope to meet him in the late afternoon. They might have turned up the slab as they descended for the night, returning the next morning to find the specimens that Walcott drew on August 31. This reconstruction gains some support from a letter that Walcott wrote to Marr (for whom he later named the “lace crab” Marrella) in October 1909:

  When we were collecting from the Middle Cambrian, a stray slab of shale brought down by a snow slide showed a fine Phyllopod crustacean on a broken edge. Mrs. W. and I worked on that slab from 8 in the morning until 6 in the evening and took back with us the finest collection of Phyllopod crustaceans that I have ever seen.

  (Phyllopod, or “leaf-footed,” is an old name for marine arthropods with rows of lacy gills, often used for swimming, on one branch of their legs.)

  Transformation can be subtle. A snow slide becomes a snowstorm, and the night before a happy day in the field becomes a forced and hurried end to an entire season. But far more important, Walcott’s field season did not finish with the discoveries of August 30 and 31. The party remained on Burgess ridge until September 7! Walcott was thrilled by his discovery and collected with avidity every day thereafter. The diaries breathe not a single word about snow, and Walcott assiduously reported the weather in every entry. His happy week brought nothing but praise for Mother Nature. On September 1 he wrote: “Beautiful warm days.”

  Finally, I strongly suspect that Walcott located the source for his stray block during the last week of his 1909 field season—at least the basic area of outcrop, if not the very richest layers. On September 1, the day after he drew the three arthropods, Walcott wrote: “We continued collecting. Found a fine group of sponges on slope (in situ) [meaning undisturbed and in their original position].” Sponges, containing some hard parts, extend beyond the richest layers of soft-bodied preservation, but the best specimens come from the strata of the Burgess mother lode. On each subsequent day, Walcott found abundant soft-bodied specimens, and his descriptions do not read like the work of a man encountering a lucky stray block here and there. On September 2, he discovers that the supposed shell of an ostracode really houses the body of a Phyllopod: “Working high up on the slope while Helena collected near the trail. Found that the large so-called Leperditia-like test is the shield of a Phyllopod.” The Burgess quarry is “high up on the slope,” while stray blocks would slide down toward the trail.

  On September 3, Walcott was even more successful: “Found a fine lot of Phyllopod crustaceans and brought in several slabs of rock to break up at camp.” In any event, he continued to collect, and put in a full day for his last hurrah on September 7: “With Stuart and Mr. Rutter went up on fossil beds. Out from 7 A.M. to 6:30 P.M. Our last day in camp for 1909.”

  If I am right about his discovery of the main beds in 1909, then the second part of the canonical tale—the week-long patient tracing of errant block to source in 1910—should be equally false. Walcott’s diary for 1910 supports my interpretation. On July 10, champing at the bit, he hiked up to the Burgess Pass campground, but found the area too deep in snow for any excavations. Finally, on July 29, Walcott reports that his party set up “at Burgess Pass campground of 1909.” On July 30, they climbed neighboring Mount Field and collected fossils. Walcott indicates that they made their first attempt to locate the Burgess beds on August 1:

  All out collecting the Burgess formation until 4 P.M. when a cold wind and rain drove us into camp. Measured section of the Burgess formation—420 feet thick. Sidney with me. Stuart with his mother and Helen puttering about camp.

  (“Measuring a section” is geological jargon for tracing the vertical sequence of strata and noting the rock types and fossils. If you wished to find the source of an errant block dislodged and tumbled below, you would measure the section above, trying to match your block to its most likely layer.)

  I think that Charles and Sidney Walcott located the Burgess beds on this very first day, because Walcott writes for his next entry of August 2: “Out collecting with Helena, Stuart, and Sidney. We found a fine lot of ‘lace crabs’ and various odds and ends of things.” “Lace crab” was Walcott’s informal field term for Marrella, and Marrella is the marker of the mother lode—the most common animal in the Burgess Shale. If we wish to give the canonical tale all benefit of doubt, and argue that these lace crabs of August 2 came from dislodged blocks, we still cannot grant a week of strenuous effort for locating the mother lode, for Walcott writes just two days later on August 4: “Helena worked out a lot of Phyllopod crustaceans from ‘Lace Crab layer.’” From then on, until the end of summer, they quarried the lace crab layer, now known as the Burgess Shale.

  The canonical tale is more romantic and inspiring, but the plain factuality of the diary makes more sense. I have been to the Burgess ridge. The trail lies just a few hundred feet below the main Burgess beds. The slope is simple and steep, with strata well exposed. Tracing an errant block to its source should not have presented a major problem—for Walcott was more than a good geologist; he was a great geologist. He should have located the main beds right away, in 1909, since he had a week to work after first discovering soft-bodied fossils. He was not able to quarry in 1909—the only constraint imposed by limits of time. But he found many fine fossils and probably the main beds themselves. He knew just where to go in 1910 and set up shop in the right place as soon as the snows melted.

  Memory is a fascinating trickster. Words and images have enormous power and can easily displace actual experience over the years. As an intriguing testimony to the power of legend, consider the late memories of Walcott’s son Sidney. In 1971, more than sixty years after the events, Sidney wrote a short article for Smithsonian, “How I Found My Own Fossil.” (The largest Burgess arthropod bears the name Sidneyia inexpectans in honor of his discovery.) Sidney must have heard the canonical tale over and over again across the many years (think of him enduring mounds of rubber chicken and endless repetitions of the anecdote in after-dinner speeches)—and his actual experience faded as the conventional myth took root.

  Sidney’s version includes the two main ingredients—serendipity in the chance discovery of a dislodged slab blocking the pathway of packhorses, and assiduous effort in the patient, week-long tracing of block to source. But Sidney places the packhorse incident on his watch in 1910, not on his mother’s the previous year:

 
Father suddenly told me to halt the packtrain. I signaled, and the horses started to browse at the side of the trail. Often on our summer camping trips I had seen Father throw stones and logs out of the trail to make the going a bit easier for the horses. So it was no surprise to see him upend a slab, worn white by the shoes of horses slipping on it for years. He hit it a few times along its edge with his geological hammer and it split open. “Look Sidney,” he called. I saw several extraordinary fossils on the rock surface. “Let’s look further tomorrow…. We won’t go to Field tonight.” To our family, back in 1910, it seemed a miracle that Father’s simple act of thoughtfulness for the comfort and safety of a few packhorses led to this discovery.

  A lovely story, but absolutely nothing about it can be true Sidney knew the canonical yarn about slabs and packhorses, but moved the tale a year forward. We cannot believe that slabs could have blocked paths for two years running, with fossils always on their upturned edges, especially since an unanticipated discovery in 1909 precludes a similar surprise the next year. Moreover, Sidney could not have remembered an actual incident of the first season, and then mixed up the years, because he wasn’t there in 1909!