Wonderful Life: The Burgess Shale and the Nature of History (3 page)

This book has three major aims. It is, first and foremost, a chronicle of the intense intellectual drama behind the outward serenity of this reinterpretation. Second, and by unavoidable implication, it is a statement about the nature of history and the awesome improbability of human evolution. As a third theme, I grapple with the enigma of why such a fundamental program of research has been permitted to pass so invisibly before the public gaze. Why is
Opabinia
, key animal in a new view of life, not a household name in all domiciles that care about the riddles of existence?

In short, Harry Whittington and his colleagues have shown that most Burgess organisms do not belong to familiar groups, and that the creatures from this single quarry in British Columbia probably exceed, in anatomical range, the entire spectrum of invertebrate life in today’s oceans. Some fifteen to twenty Burgess species cannot be allied with any known group, and should probably be classified as separate phyla. Magnify some of them beyond the few centimeters of their actual size, and you are on the set of a science-fiction film; one particularly arresting creature has been formally named
Hallucigenia
. For species that can be classified within known phyla, Burgess anatomy far exceeds the modern range. The Burgess Shale includes, for example, early representatives of all four major kinds of arthropods, the dominant animals on earth today—the trilobites (now extinct), the crustaceans (including lobsters, crabs, and shrimp), the chelicerates (including spiders and scorpions), and the uniramians (including insects). But the Burgess Shale also contains some twenty to thirty kinds of arthropods that cannot be placed in any modern group. Consider the magnitude of this difference: taxonomists have described almost a million species of arthropods, and all fit into four major groups; one quarry in British Columbia, representing the first explosion of multicellular life, reveals more than twenty additional arthropod designs! The history of life is a story of massive removal followed by differentiation within a few surviving stocks, not the conventional tale of steadily increasing excellence, complexity, and diversity.

For an epitome of this new interpretation, compare Charles R. Knight’s restoration of the Burgess fauna (figure 1.1), based entirely on Walcott’s classification, with one that accompanied a 1985 article defending the reversed view (figure 1.2).

1.The centerpiece of Knight’s reconstruction is an animal named
Sidneyia
, largest of the Burgess arthropods known to Walcott, and an ancestral chelicerate in his view. In the modern version,
Sidneyia
has been banished to the lower right, its place usurped by
Anomalocaris
, a two foot-terror of the Cambrian seas, and one of the Burgess “unclassifiables.”

2.Knight restores each animal as a member of a well-known group that enjoyed substantial later success.
Marrella
is reconstructed as a trilobite,
Waptia
as a proto-shrimp (see figure 1.1), though both are ranked among the unplaceable arthropods today. The modern version features the unique phyla—giant
Anomalocaris; Opabinia
with its five eyes and frontal “nozzle”;
Wiwaxia
with its covering of scales and two rows of dorsal spines.

3.Knight’s creatures obey the convention of the “peaceable kingdom.” All are crowded together in an apparent harmony of mutual toleration; they do not interact. The modern version retains this unrealistic crowding (a necessary tradition for economy’s sake), but features the ecological relations uncovered by recent research: priapulid and polychaete worms burrow in the mud; the mysterious
Aysheaia
grazes on sponges;
Anomalocaris
everts its jaw and crunches a trilobite.

4.Consider
Anomalocaris
as a prototype for Whittington’s revision. Knight includes two animals omitted from the modern reconstruction: jellyfish and a curious arthropod that appears to be a shrimp’s rear end covered in front by a bivalved shell. Both represent errors committed in the overzealous attempt to shoehorn Burgess animals into modern groups. Walcott’s “jellyfish” turns out to be the circlet of plates surrounding the mouth of
Anomalocaris
; the posterior of his “shrimp” is a feeding appendage of the same carnivorous beast. Walcott’s prototypes for two modern groups become body parts of the largest Burgess oddball, the appropriately named
Anomalocaris
.

Thus a complex shift in ideas is epitomized by an alteration in pictures. Iconography is a neglected key to changing opinions, for the history and meaning of life in general, and for the Burgess Shale in stark particulars.

1.1. Reconstruction of the Burgess Shale fauna done by Charles R. Knight in 1940, probably the model for his 1942 restoration. All the animals are drawn as members of modern groups. Above
Sidneyia
, the largest animal of the scene,
Waptia
is reconstructed as a shrimp. Two parts that really belong to the unique creature
Anomalocaris
are portrayed respectively as an ordinary jellyfish (top, left of center) and the rear end of a bivalved arthropod (the large creature, center right, swimming above the two trilobites).

1.2. A modern reconstruction of the Burgess Shale fauna, illustrating an article by Briggs and Whittington on the genus
Anomalocaris
. This drawing, unlike Knight’s, features odd organisms.
Sidneyia
has been banished to the lower right, and the scene is dominated by two specimens of the giant
Anomalocaris
. Three
Aysheaia
feed on sponges along the lower border, left of
Sidneyia
. An
Opabinia
crawls along the bottom just left of
Aysheaia
. Two
Wiwaxia
graze on the sea floor below the upper
Anomalocaris
.

Familiarity has been breeding overtime in our mottoes, producing everything from contempt (according to Aesop) to children (as Mark Twain observed). Polonius, amidst his loquacious wanderings, urged Laertes to seek friends who were tried and true, and then, having chosen well, to “grapple them” to his “soul with hoops of steel.”

Yet, as Polonius’s eventual murderer stated in the most famous soliloquy of all time, “there’s the rub.” Those hoops of steel are not easily unbound, and the comfortably familiar becomes a prison of thought.

Words are our favored means of enforcing consensus; nothing inspires orthodoxy and purposeful unanimity of action so well as a finely crafted motto—Win one for the Gipper, and God shed his grace on thee. But our recent invention of speech cannot entirely bury an earlier heritage. Primates are visual animals par excellence, and the iconography of persuasion strikes even closer than words to the core of our being. Every demagogue, every humorist, every advertising executive, has known and exploited the evocative power of a well-chosen picture.

Scientists lost this insight somewhere along the way. To be sure, we use pictures more than most scholars, art historians excepted.
Next slide please
surpasses even
It seems to me that
as the most common phrase in professional talks at scientific meetings. But we view our pictures only as ancillary illustrations of what we defend by words. Few scientists would view an image itself as intrinsically ideological in content. Pictures, as accurate mirrors of nature, just are.

I can understand such an attitude directed toward photographs of objects—though opportunities for subtle manipulation are legion even here. But many of our pictures are incarnations of concepts masquerading as neutral descriptions of nature. These are the most potent sources of conformity, since ideas passing as descriptions lead us to equate the tentative with the unambiguously factual. Suggestions for the organization of thought are transformed to established patterns in nature. Guesses and hunches become things.

The familiar iconographies of evolution are all directed—sometimes crudely, sometimes subtly—toward reinforcing a comfortable view of human inevitability and superiority. The starkest version, the chain of being or ladder of linear progress, has an ancient, pre-evolutionary pedigree (see A. O. Lovejoy’s classic,
The Great Chain of Being
, 1936). Consider, for example, Alexander Pope’s
Essay on Man
, written early in the eighteenth century:

And note a famous version from the very end of that century (figure 1.3). In his
Regular Gradation in Man
, British physician Charles White shoehorned all the ramifying diversity of vertebrate life into a single motley sequence running from birds through crocodiles and dogs, past apes, and up the conventional racist ladder of human groups to a Caucasian paragon, described with the rococo flourish of White’s dying century:

1.3. The linear gradations of the chain of being according to Charles White (1799). A motley sequence runs from birds to crocodiles to dogs and monkeys (bottom two rows), and then up the conventional racist ladder of human groups (top two rows).

This tradition never vanished, even in our more enlightened age. In 1915, Henry Fairfield Osborn celebrated the linear accretion of cognition in a figure full of illuminating errors (figure 1.4). Chimps are not ancestors but modern cousins, equally distant in evolutionary terms from the unknown forebear of African great apes and humans.
Pithecanthropus
(
Homo erectus
in modern terms) is a potential ancestor, and the only legitimate member of the sequence. The inclusion of Piltdown is especially revealing. We now know that Piltdown was a fraud composed of a modern human cranium and an ape’s jaw. As a contemporary cranium, Piltdown possessed a brain of modern size; yet so convinced were Osborn’s colleagues that human fossils must show intermediate values on a ladder of progress, that they reconstructed Piltdown’s brain according to their expectations. As for Neanderthal, these creatures were probably close cousins belonging to a separate species, not ancestors. In any case, they had brains as large as ours, or larger, Osborn’s ladder notwithstanding.