Does such a procedure distort or limit the description of science? Of course it does. Every scientist knows that most activities, particularly the mistakes and false starts, don’t enter the published record, and that conventions of scientific prose would impart false views of science as actually done, if we were foolish enough to read technical papers as chronicles of practice. Bearing this self-evident truth in mind, I shall call upon a variety of sources as I proceed. But I prefer to focus on the monographic record for a particular, and largely personal, reason.
The psychology of discovery is endlessly fascinating, and I shall not ignore that subject. But the logic of argument, as embodied in published work, has its own legitimate, internal appeal. You can pull an argument apart into its social, psychological, and empirical sources—but you can also cherish its integrity as a coherent work of art. I have great respect for the first strategy, the mainstay of scholarship, but I love to practice the second as well (as I did in my book Time’s Arrow, Time’s Cycle, an analysis of the central logic in three texts crucial for geology’s discovery of time). Chronological change in a succession of arguments, each coherent at its own moment, forms a primary record of intellectual development.
The revision of the Burgess Shale involves hundreds of people, from the helicopter pilots who flew supplies in and out of Burgess base camp, to the draftsmen and artists who prepared drawings for publication, to an international group of paleontologists who offered support, advice, and criticism. But the research program of monographic revision has centered on one coherent team. Three people have played the focal role in these efforts: the originator of the project and chief force throughout, Harry Whittington, professor of geology at Cambridge University (that is, in British terminology, senior figure and department head), and two men who began as graduate students under him in the early 1970s and have since built brilliant careers on their researches in the Burgess Shale—Simon Conway Morris (now also at Cambridge) and Derek Briggs (now at Bristol University). Whittington also collaborated with two junior colleagues, especially before his graduate students arrived—Chris Hughes and David Bruton.
The seeds of conventional drama lie with these people, particularly in the interaction between Whittington and Conway Morris, but I have no such story to tell. Whittington is meticulous and conservative, a man who follows the paleontological straight and narrow, eschewing speculation and sticking to the rocks—exactly the opposite of anyone’s image for an agent of intellectual transformation. Conway Morris, before the inevitable mellowing of ontogeny, was a fiery Young Turk, a social radical of the 1970s. He is, by temperament, a man of ideas, but happily possessed of the patience and Sitzfleisch needed to stare at blobs on rocks for hours on end. In legend, the Burgess reinterpretation would have emerged as a tense synergism between these men—Harry instructing, pleading caution, forcing attention to the rocks; Simon exhorting, pushing for intellectual freedom, nudging his reluctant old mentor toward a new light. One can imagine the discussions, the escalating arguments, the threats, the near fracturings, the break, the return of the prodigal son, the reconciliation.
I don’t think that any of this occurred, at least not overtly. And if you know the British university system, you will immediately understand why. British doctoral students study in nearly complete independence. They take no courses, but only work on their dissertation. They agree on a topic with their mentor, and then start their research. If they are lucky, they may meet with their adviser once every month or so; once a year would be more likely. Harry Whittington, a quiet, conservative, and inordinately busy man, was not about to challenge this peculiar tradition. Simon has told me that “Harry didn’t like being disturbed,” for he “grudged every moment that he couldn’t get on with his research.” But he was, Simon insists, “a splendid adviser; for he left us alone and he got us support.”
I have questioned Harry, Simon, and Derek many times, trying to probe through my initial disbelief. They all insist that they never viewed themselves as a team with a coherent purpose or a general attitude. They were not striving actively to develop a central interpretation together. They never met regularly; in fact, they insist that they never met as a group at all. They didn’t even encounter each other on the one certain gathering ground of any British academic department—the almost unmissable daily ritual of morning coffee—for Simon, the social radical, had formed a rump group in his office, and never came, while Harry, who could always see essence beneath externality (the key to deciphering the Burgess animals, after all), never insisted on conformity of any kind. Oh, they all engaged in complex cross-fertilization—but as much, I suspect, by reading each other’s papers as by any programmatic or regular discussion. The most I could wrest from any of the trio was an acknowledgement by Derek Briggs that they developed “some corporate perception, even if not by daily interaction.”
The drama I have to tell is intense and intellectual. It transcends these ephemeral themes of personality and the stock stage. The victory at stake is bigger and far more abstract than any material reward—a new interpretation of life’s history. This goal, once achieved, brings no particular earthly benefit. Paleontology has no Nobel prizes—though I would unhesitatingly award the first to Whittington, Briggs, and Conway Morris as a trio. And, as the old clichés go, you can’t fry an egg with your new view of life, or get on the subway, unless you also have a token. (I don’t think it even gets you any frequent-flyer miles, though almost everything else does.) You do get the gratitude of your fellow paleontologists, and it doesn’t harm your job prospects. But the main reward must be satisfaction—the privilege of working on something exciting, the internal peace of accomplishment, the rare pleasure of knowing that your life made a difference. What more can a person want than to hear, from whatever source he honors as absolute and permanent, the ultimate affirmation that life has been useful: “Well done, thou good and faithful servant”?
A METHODOLOGY OF RESEARCH
A common misconception holds that soft-bodied fossils are usually preserved as flat films of carbon on the surface of rocks. The Burgess organisms are, of course, strongly compressed—we cannot expect the preservation of much three-dimensional structure as the weight of water and sediment piles above an entombed body devoid of hard parts. But the Burgess fossils are not always completely flattened—and this discovery provided Whittington with the basis for a method that could reveal their structure. (Burgess soft parts, by the way, are not preserved as carbon. By a chemical process not yet understood, the original carbon was replaced by silicates of alumina and calcium, forming a dark reflective layer. This replacement did not compromise the exquisite preservation of anatomical detail.)
Walcott never recognized, or appreciated only dimly, that some three-dimensional architecture had been retained. He treated the Burgess fossils as flat sheets, and therefore worked by searching through his specimens for the ones preserved in the most revealing (or least confusing) orientation—usually, for bilaterally symmetrical animals, splayed out straight and flat (as in figure 3.1, a typical Walcott illustration). He ignored specimens in an oblique or frontal orientation, because he thought that the different parts and surfaces so encountered would be squashed together into a single uninterpretable film on the bedding plane; a top view, by contrast, would offer maximal resolution of separate features.
Walcott illustrated his specimens by photographs, often egregiously retouched. Whittington’s group has also used photography extensively, but mostly for publication, rather than as a primary research tool. The Burgess specimens do not photograph well (figure 3.2 is a magnificent exception), and little can be gained by working from prints, however enlarged or filtered, rather than from actual specimens. The aluminosilicate surfaces reflect light in various ways at different angles of illumination—and some resolution has been gained by comparing the dull images obtained at high angles of illumination with the bright reflections, obtained at low angles.
Whittington therefore used the oldest method of a
ll as his primary mode of illustration—patient and detailed drawing of specimens. The basic item of machinery, the camera lucida, is no different now from the model that Walcott used, and not much improved from its original invention by the mineralogist W. H. Wollaston in 1807. A camera lucida is, basically, a set of mirrors that can focus the image of an object onto a flat surface. You can attach a camera lucida to a microscope and cast the image under the lens onto a piece of paper. By simultaneously viewing the specimen and its reflection on paper, you can draw the animal without moving your head from the eyepiece. Whittington and his team adopted the procedure of drawing every specimen, at very large scale, for any species under investigation. You can study a set of drawings together, but you cannot easily make simultaneous observations on numerous tiny specimens, all needing magnification.
Whittington applied his camera lucida and skill in drafting to a set of methods all linked to his central recognition that the Burgess fossils retained some three-dimensional structure, and were not just flattened sheets on bedding planes. I shall illustrate the power of these simple procedures by showing their usefulness in the study of the largest Burgess arthropod, the species that Walcott named Sidneyia inexpectans to honor his son, who had found the first specimen. (I choose Sidneyia because David Bruton’s 1981 monograph on this genus is, in my opinion, the most technically elegant and attractive publication of the entire series by Whittington and his associates.) Consider the three main operations:
3.1. An attractive plate of Burgess photographs from Walcott’s 1912 monograph on arthropods. The photographs are extensively retouched. Canadaspis is at top left; Leanchoilia at bottom.
3.2. The best unretouched photo ever taken of a Burgess Shale organism. Des Collins took this photograph of a Naraoia, preserved in side view. This specimen does not come from Walcott’s quarry, but from one of the dozen additional localities for soft-bodied fossils recently found by Collins in the same area. Specimens from Walcott’s quarry do not photograph this well.
1. Excavation and dissection. If Walcott had been right, all anatomy would be compressed into a single film, and the task of reconstruction would be akin to reviving a cartoon character squashed flat by a steam-roller. But what works for Sylvester the cat in a world of fantasy cannot be duplicated for a slab of shale.
Fortunately, the Burgess fossils do not usually lie on a single bedding plane. Engulfed by the mud that buried them, the animals settled into their tombs at various orientations. The mud often infiltrated and sorted their parts into different microlayers, separated by thin veils of sediment—carapace above gills, and gills above legs—thus preserving some three-dimensional structure even when the muds became compressed later on.
By using small chisels or a very fine vibro-drill, not much different from the model in your dentist’s office, upper layers can be carefully removed to reveal internal parts beneath. (As these layers are often but microns thick, this delicate work can also be done by hand and with needles, grain by grain or flake by flake.)
3.3. Reconstruction of Sidneyia from a three-dimensional model built in sections by Bruton. (A) The entire animal. (B) The model in six segments, starting from bottom left—the head with its ventral covering plate below, the body in three sections, and the tail piece. (C) The head and front part of the body connected, with the head in the background and to the right. Note the biramous appendages with their walking legs below and gill branches above.
Some arthropods are fairly flat, but Sidneyia, as the reconstruction shows (figure 3.3), possessed considerable relief; its carapace, or outer covering, formed an arched semicylinder over the soft parts beneath.* In some specimens the underlying gills and legs protrude through a broken carapace, for natural compression and fracturing of specimens is extensive. But Bruton found that he had to go digging in order to reveal an anatomical totality. The appendages of many marine arthropods contain two branches (see pages 104–5, in the inset on arthropod anatomy)—an outer branch bearing gills, used for respiration and swimming, and an inner branch, or walking leg, often used in feeding as well. Hence, as you cut through the outer covering over the center of the body, you first encounter the gill branches, then the leg branches. Bruton found that he could begin with a complete outer covering (figure 3.4), and then dissect through to reveal a layer of gills (figure 3.5), followed by a set of walking legs (figure 3.6). (These drawings are all done directly from the fossils themselves, using a camera lucida attached to a binocular microscope.) Bruton described his method in the conventional passive voice of technical monographs:
Preparation of specimens shows features … to occur at successive levels within the rock and these can be revealed by carefully removing one from above the other, or by removing the thin layer of sediment that separates them.… The method of approach has been to remove successively first the dorsal exoskeleton … to reveal the filaments of the gills, and then those to expose the leg. Adjacent to the midline where the limb is attached, all three successive layers, dorsal exoskeleton—gill—leg, lie directly upon each other and it is a matter of hopefully removing an infinitely thin layer of material with the aid of a vibro-chisel (1981, pp. 623–24).
3.4. Camera lucida drawing of a complete specimen of Sidneyia, showing the outer covering intact.
3.5. Camera lucida drawing of a Sidneyia specimen, primarily showing the gill branches of the appendages underneath the carapace. The incomplete trace of the gut (center) is indicated by oblique stripes. The gill branches are the delicately fingered structures labeled g (the number that follows identifies the body segment).
3.6. The walking legs are exposed underneath the gill branches. In this camera lucida drawing, the legs are labeled Rl, for “right leg” (the number that follows identifies the body segment).
Other rewards lie beneath the outer covering. The alimentary canal runs just beneath the carapace, along the midline. One excavated specimen (figure 3.7) revealed a tiny trilobite right in the canal, near the posterior end—a remnant of Sidneyia’s last meal before the great mudslide.
2. Odd orientations. Since the phyllopod bed was formed by several fossilized mudslides, animals are entombed in a variety of orientations. The majority were buried in their most stable hydrodynamic position, for the mud settled gradually and animals drifted to the bottom. But some came to rest on one side or at an angle—twisted or turned in various ways. In his monograph on the enigmatic Aysheaia, Whittington illustrated both the “conventional” orientation, with the animal lying flat, its appendages splayed to the sides, and one of the rarer positions, with the animal twisted and sideways, so that appendages from both sides are compressed and jumbled together (figure 3.8).
Walcott collected specimens in odd orientations, but he tended to ignore them as less informative, and even uninterpretable in their overlapping of different surfaces on a single bedding plane. But Whittington realized that these unusual orientations are indispensable, in concert with specimens in the “standard” position, for working out the full anatomy of an organism. Just as you could not fully reconstruct a house from photos all taken from a single vantage point, “snapshots” at many angles must be combined to reconstruct a Burgess organism. Conway Morris told me that he managed to reconstruct the curious Wiwaxia—an animal with no modern relatives, and therefore no known prototype to use as a model—by drawing specimens that had been found in various orientations, and then passing countless hours “rotating the damned thing in my mind” from the position of one drawing to the different angle of another, until every specimen could be moved without contradiction from one stance to the next. Then he finally knew that nothing major was missing or out of place.
3.7. This specimen of Sidneyia reveals its last meal, a tiny trilobite preserved in the rear end of the alimentary tract. The trilobite lies in the small exposed portion of the gut (labeled al), just above the first abdominal segment (ab1).
3.8. Two figures from Whittington (1978), illustrating the preservation of Aysheaia in various positions. (A) The con
ventional orientation: we look down on the dorsal, or top, side; the appendages are splayed out in both directions. (B) A much less common orientation: the animal was buried on its side, and the resulting fossil shows one flank, with the appendages of both sides compressed together.
Most specimens of Sidneyia are preserved in full, flattened view—as if we were looking down from above (as in figure 3.5). This orientation reveals, better than any other, the basic dimensions of body parts, but must leave several questions unresolved, particularly the degree of relief, or rounding, of the body. In this orientation, we can’t tell whether Sidneyia was a pancake or a tube. Frontal views are needed to reconstruct the basic shape, and to determine some crucial aspects of anatomy not well seen “from above”—the form of the legs in particular.
Figure 3.9, a view from the front, shows the rounded shape of the head, and the positions of insertion for the single pair of antennae and the eyes. Figure 3.10, a head-on view from farther back, illustrates both the rounded shape of the body and a sequence of legs, with their numerous spiny segments all well preserved. We also note the dimensions of the central food groove, running between the coxae, the first segments of the legs, on each side. The gnathobases, the spiny edges of the coxae, border the food groove and give us some appreciation for the probable predatory or scavenging habits of this largest Burgess arthropod. We must assume that large pieces of food were passed forward to the mouth—no wimpy filtrate for this creature. Figure 3.11 shows a close-up of a walking leg, also in frontal orientation.
Wonderful Life: The Burgess Shale and the Nature of History Page 8