Wonderful Life: The Burgess Shale and the Nature of History (59 page)

†
Walcott had placed two species in the genus
Yohoia
—
Y. tenuis
and
Y. plena
. Whittington realized that the two animals are distinct and belong in different genera.
Y. plena
, which has antennae, is a phyllocarid, one of the arthropods with a bivalved carapace soon to be studied by Derek Briggs. Whittington removed this species from
Yohoia
and established a new genus,
Plenocaris. Yohoia tenuis
is the oddball, and subject of the 1974 monograph.

*
I view this as a crucial and favorable feature for the general story of this book—because you can be sure that Whittington came to his new interpretation of the Burgess from an accumulating weight of evidence, not from any
a priori
desire to go down in history as a radical reformer.

*
The leading British professional association of paleontologists. They call themselves the “pale ass” for informal fun—a name even more humorous to an American, since the title only refers to a donkey in England (where your nether end is your arse).

*
A. M. Simonetta, an Italian paleontologist, deserves a great deal more credit than this book has space to provide. He alone, after Walcott and before Whittington, attempted a comprehensive program of revision for Burgess arthropods. He worked as Walcott had, and with Walcott’s specimens, treating the fossils essentially as films on the rock surface and attempting no preparation of specimens. He therefore made many mistakes in a long series of papers published during the 1960s and 1970s. But he also provided substantial improvements upon several earlier studies, and through his comprehensive efforts reminded paleontologists about the richness of the Burgess Shale. Since science is a process of correction, Simonetta’s errors also provided an important spur to Whittington and his colleagues.

*
My Catholic friends may cite Pius IX and December 8, 1854, for the last item in my list, but
Ineffabilis Deus
was an official resolution under the rules of the institution, and no one could pick one moment as paramount in a millennium of previous debate. On Darwin’s long and complex struggle to develop the theory of natural selection, see Howard Gruber,
Darwin on Man
. (New York: Dutton, 1974).

*
Since Simon and Derek began working with Harry Whittington in 1972, the year of the infamous laughter over
Opabinia
at the Oxford meeting, I had assumed that their prodding must have convinced Harry to take the drastic step of declaring
Opabinia
as a unique anatomy of phylum-level status. This is how the script is supposed to go—the Young Turks dragging the old farts into the light of exciting modernity. Terrible screenplay, not at all like complex life. Simon may be ideologically radical, but he is one hell of an excellent descriptive anatomist—and anyone who would be fooled enough by externalities to rank Harry as an old fart understands nothing about the multifarious nature of genius. In any case, all three protagonists assure me that Harry worked out the interpretation of
Opabinia
without any hectoring or encouragement from radicals on the sidelines. The converse is equally true and contrary to script. Harry neither discouraged Simon as he wrote his five papers, nor helped with frequent counseling. Harry played virtually no role in Simon’s first forays. He can remember only one intervention—an insistence that Simon use his techniques of dissection to excavate the spines of
Hallucigenia
right to the point of their connection with the body. Damned good advice, but scarcely the stuff of general guidance.

*
I don’t say this in a critical, revelatory, or muckraking mood. Journalistic traditions properly match their assigned roles. I only point out that different approaches see only restricted parts of a totality—as in the overworked simile of the blind men and the elephant—and that one can get something gloriously wrong by mistaking a small and biased segment for an entity.

*
The mouth parts of arthropods have been given the same names as functionally comparable structures in vertebrates—maxilla, mandible, and so forth. Similarly, the parts of insect legs bear the same names—trochanter, tibia—as their vertebrate counterparts. This is an unfortunately confusing nomenclature, for whatever the functional similarities, the structures have no evolutionary connection: insect mouth parts evolved from legs; vertebrate jaws from gill arches.

*
As an indication of how much struggle and effort can underlie the conclusions stated so briefly in my text, consider this interesting note that Derek Briggs wrote to me as a reaction to this passage when I sent the manuscript of this book to him: “The work on
Canadaspis
became a hunt for the first crustacean.… By then the expectation was that the odds on any of the arthropods falling into living groups were very low. The problem with
Canadaspis
was finding the critical evidence of the posterior cephalic [head] appendages. USNM 189017 [catalog number of a key specimen in the United States National Museum] is the best of only about 3 (out of thousands) specimens which show these limbs in lateral view (they are almost without exception totally obscured by the carapace, compaction etc.), and as you can see on Plate 5 (Briggs 1978) it was a huge job preparing the specimen to show them. In my view figs. 66–69 on that plate represent the peak of what can be achieved by preparing part and counterpart in tandem. I then had a major job convincing Sidnie Manton (Harry’s arthropod guru) that I did indeed have the critical evidence—at the time I considered that an enormous achievement! [Manton was the world’s greatest expert on the higher-level classification of arthropods—and one tough lady.] It was not just a case of the evidence of the specimens; it was necessary to argue that the first two pairs of a series of 10 pairs of similar biramous appendages belonged to the head—although they remain primitive in not being significantly differentiated from those which follow.”

*
I am as committed as anyone to “ecology” (in the vernacular and political meaning of leaving nature alone), and I certainly believe in respecting the nearly sacred integrity of national parks. But a fossil on the ground is worth absolutely nothing. It is not an object of only pristine beauty, or a permanent part of any natural setting (especially for fossils exposed in quarry walls). If free on the ground, it will probably be cracked and frost-heaved into oblivion by the next field season. Controlled collecting and scientific study are the proper roles, intellectually and ethically, for the Burgess fossils.

*
The status of the Onychophora, probable taxonomic home of
Aysheaia
, remains controversial. Some experts regard the Onychophora as an entirely separate phylum, no closer to the uniramians than to any other group of arthropods. If this solution is correct, my argument here is wrong. The two other major solutions both support my argument: first, that Onychophora should rank within the Arthropoda on the uniramian line; second (and probably the predominant view), that onychophorans deserve separate status, but lie closer to the uniramians than to any other group of arthropods. (This last argument assumes a separate evolutionary origin for several, perhaps all four, of the great arthropod lines—with uniramians arising in genealogical proximity to onychophorans.)

*
A small and little-known molluscan group called the Aplacophora does seem more similar in its elongate, wormlike body, sometimes covered with plates or spicules, but Conway Morris enumerates an impressive list of detailed differences in his monograph.

*
If I wished to play devil’s advocate against my own framework, I would argue that the criterion by which we make the claim of twenty losers and only four winners is falsely retrospective. By patterns of tagmosis, modern arthropods are surely strikingly less disparate than Burgess forebears. But why use patterns of tagmosis as a basis for higher-level classification of arthropods? A nearly microscopic ostracode, a terrestrial isopod, a planktonic copepod, a Maine lobster, and a Japanese king crab span more variety in size and ecological specialization than all the Burgess arthropods put together—though all these modern creatures are called Crustacea, and display the stereotyped tagmosis of this class. A paleontologist living during the Burgess might consider the arthropods as less varied because he had no reason to regard patterns of tagmosis as a particularly important character (for the utility of tagmosis in distinguishing major genealogical lines only became apparent later, after most alternatives were decimated and stereotypy set in among the few surviving and highly disparate lines).

I regard this argument as a poor case. If you wish to reject tagmosis as too retrospective then what other criterion will suggest less disparity in the Burgess? We use basic anatomical designs, not ecological diversification, as our criterion of higher-level classification (bats and whales are both mammals). Nearly every Burgess genus represents a design unto itself by any anatomical criterion. Tagmosis does stabilize in post-Burgess times, as do arrangement and forms of appendages-while no major feature of arthropod design can distinguish broad and stable groups in the Burgess.

*
Many of Walcott’s cruder errors, on the other hand—confusing the sclerites of
Wiwaxia
with setae of polychaetes, and the lateral Haps of
Opabinia
with arthropod segments represented a more basic failure to distinguish analogy from homology.

*
Thus, we can take some steps to resolving the genealogy of Burgess organisms. We can eliminate some resemblances based on analogy-setae of polychaetes and sclerites of Wiwaxia, for example. We can also eliminate some shared-but-primitive characters that do not define genealogical groups-bivalved carapaces and “merostomoid” body form. But the identification of shared-and-derived characters has been largely unsuccessful so far. Homology of shared-and-derived frontal appendages may unite Leanchoilia with Actaeus (and perhaps also with Alalcomenaeus). The lateral Raps with gills above may be shared-andderived characters in Opabinia and Anomalocaris, thus constituting the only genealogical linkage between two of the weird wonders.

*
Technical footnote: Several efforts have been made to construct a cladogram for the Burgess arthropods (Briggs, 1983, and in press). These have, so far, been conspicuously unsuccessful, as the different possibilities do not satisfactorily converge. If the grabbag model is correct, and each maior feature of each new lineage arises separately from a suite of latent possibilities common to all, then genealogical connectivity of phenotypes is broken, and the problem may be intractable by ordinary cladistic methods. Of course, some continuity in some genuinely nested sets of characters may well exist, but the appropriate features will be difficult to identify.

†
I exaggerate to make a point. Rules of construction and order pervade nature. Not all conceivable combinations can work, nor can all amalgams be constructed within the developmental constraints of metazoan embryology. I use this metaphor only to express the vastly expanded range of Burgess possibilities.

*
Biology textbooks often speak of variation as “random.” This is not strictly true. Variations are not random in the literal sense of equally likely in all directions; elephants have no genetic variation for wings. But the sense that “random” means to convey is crucial: nothing about genetics predisposes organisms to vary in adaptive directions. If the environment changes to favor smaller organisms, genetic mutation does not begin to produce biased variation toward diminished size. In other words, variation itself supplies no directional component. Natural selection is the cause of evolutionary change; organic variation is raw material only.

*
I retranslate here, hoping not to repeat one of the greatest absurdities I ever encountered—Milton’s
Paradise Lost
translated into German as part of the libretto for Haydn’s
Creation
, then retranslated as doggerel for a performance in English that could not use Milton’s actual words and still retain Haydn’s musical values.

*
Perhaps the most touching document in the Walcott archives at the Smithsonian Institution is the highly personal note of condolence written to Walcott by Roosevelt upon the accidental death of Walcott’s second wife.

*
Yes, this is William Howard Taft, then ex-president, and acting chief justice of the United States, who introduced this memorial meeting for Walcott.

*
I do not like to discuss intellectual issues as abstract generalities. I believe that conceptions are best appreciated and understood through their illustration in a person’s idea, or in a natural object. Thus, I am charmed and fascinated by Walcott. I have rarely “met” a man so out of tune with my own view of life—and I do feel that I know him after so much intimacy from the archives. Yet 1 have gained enormous respect for Walcott’s integrity and demoniacal energy in research and administration. I do not particularly like him (as if my opinion mattered a damn), but I am mighty glad that he graced my profession.

*
Walcott is identified on this manuscript as “of the Geological Survey and Honorary Curator of Paleozoic Fossils in the National Museum.” He held the honorary curatorial post from 1892 until he became secretary of the Smithsonian in 1907. I assume that he had not yet been appointed director of the Survey, for he would have been so identified. Since he became director in 1894, the date of the lecture must be between 1892 and 1894.

*
One tangential point before leaving this rare example of a public address by such a private and imperious man. Walcott was a clear but uninspired writer. So many professionals make the mistake of assuming that popular presentations of science—particularly writing about nature—must abandon clarity for overblown, rapturous description. A Wordsworth or a Thoreau can pull it off; the great majority of naturalists, however great their emotional love for the outdoors, cannot—and should not try, lest the ultimate in unintended parody arise. Besides, audiences do not need such a crutch. The “intelligent layperson” exists in abundance and need not be coddled. Nature shines by herself. But, in any case, and with some embarrassment, I give you Charles Doolittle Walcott on the Grand Canyon at sunset: