The Garden of Ediacara
by Mark A. S. McMenamin,
Columbia University Press, New York
1998, xvi + 295 pp.
ISBN 0-231-10558-4, $29.95 (US).
Reviewed by Ben Waggoner
Department of Biology, University of Central Arkansas, Conway, AR 72035, USA.
It always comes up eventually, after I’ve been introduced to people, once they find out what I do. "Oh, what fossils do you study?" (This is after we’ve established that paleontologists don’t work on arrowheads, potsherds, or Stonehenge. That usually takes a minute.)
"You know that book Wonderful Life by Stephen Jay Gould?"
"Yes." (Hopefully. If they say "No," I have a bit more explaining to do.)
"Well, the fossils I work on are just a bit older than that. You see, even before the earliest animals with skeletons, there were these soft-bodied creatures. . ."
Having to explain things that way gives me a touch of chagrin, in part because we Ediacara-ologists have had no book comparable to Wonderful Life that lets our even weirder wonders find a wider audience. But it also shows just how much impact Wonderful Life has had. Not only did it draw a lot of public attention to Cambrian fossils and evolutionary events, but it also sparked an ongoing, sometimes fierce, but quite productive debate within the paleontological community on the issues Gould raised. Regardless of whether you love or hate the book—not many books can both engage the general public and stir up the specialists.
Mark McMenamin apparently tries to do the same thing with The Garden of Ediacara. This is the first English-language book to focus on the Ediacara biota since Glaessner’s excellent but now outdated The Dawn of Life (Glaessner 1984). Its intended audience is much wider than The Dawn of Life; McMenamin includes everything from descriptions to theories and speculations to philosophy to travelogues to anecdotes and biography. But the crux of the book is McMenamin’s triumphal announcement that he has found the solution to the Great Mystery: he knows what these fossils are. He boldly traces the evolutionary and philosophical consequences of his momentous discovery. Unfortunately, The Garden of Ediacara falls as flat as a week-old Dickinsonia roadkill, because it doesn’t really do anything very well. Scientists and laymen alike will be turned off by the book’s jagged organization, stylistic weaknesses, constant horn-blowing, and endless speculation.
There are three major problems with the book as a whole. The first serious flaw is the relatively small number of photos of the Ediacaran fossils. Most of its illustrations are fairly simple, unshaded line drawings, which aren’t always accurate—I know that Bomakellia doesn’t have the ornamented glabella-like thingamajig that figure 5.7 illustrates. A book that purports to solve the Mystery of Ediacaran Life really ought to include more photographs, camera lucida drawings, and professional-quality reconstructions of the specimens—as did The Dawn of Life, Wonderful Life, The Fossils of the Burgess Shale (Briggs et al. 1994), The Crucible of Creation (Morris 1998), and so on.
The second problem, more stylistic than scientific, is that the tone constantly swings from chatty to lyrical to technical. There’s nothing intrinsically wrong with writing in any of these tones, but the stylistic leaps and lurches interfere with the flow of ideas. Chapter 8, for instance, starts with a cheerful account of how the Proterozoic supercontinent Rodinia was prophesied in the New Age religion of Urantia—and ends with a discussion of Precambrian crust that sounds like part of a review paper. It’s as if neither McMenamin nor the publishers really knew who their intended audience was meant to be.
Thirdly, this choppiness extends to the overall organization of the book. Most of the chapters focus on specific case studies done by McMenamin or his colleagues, and there’s not much continuity between them. This gives the book the feel of certain doctoral dissertations (including mine, I admit). While it’s natural for any author to focus on what he knows first-hand, this approach doesn’t really give a balanced view of the current state of the field. For instance, almost all the discussion centers around the biotas of Namibia and southwest North America, while the biotas and localities of Australia, north Russia, Siberia, etc. receive much less attention. It also heightens the book’s jagged, cobbled-together feel. The broad philosophical chapters never quite mesh with the detailed chapters, and there isn’t much solid middle ground between them.
Chapters 1 and 2 are reviews of the biota, illustrated primarily with line drawings. These are fairly good summaries (if a trifle self-serving) of what the Ediacaran fossils look like, and they mention some of the newer directions in the field. Chapter 3 deals with McMenamin’s interpretation of the fossil Vermiforma, first described from North Carolina and now re-re-described from Mexico. Like much of this book, it’s interesting enough, but suffers from the absence of key data. McMenamin’s interpretation of his Mexican specimen hinges on geopetal structures in the slab, but he doesn’t figure them, giving only two previously published photos of the same face of the specimen (one of which has an incorrect scale bar).
Chapter 4, the book’s longest, is McMenamin’s travelogue of Dolf Seilacher’s expedition to Namibia in 1993, in which Dolf took along McMenamin, Bruce Runnegar, Jim Gehling, Friedrich Pflüger, and others, using his Crafoord Prize money. This chapter is at its best when it reports the conversations and debates of the scientists involved. We get good glimpses of new ideas being created and hammered out in discussions among the leaders in the field. It also includes more and better photos than most of the rest of the book. In the narrative of the trip, McMenamin includes a great deal of natural history, human history, anthropology, and local color, much of it rich and fascinating, about a place quite unfamiliar to most English speakers. However, there can be too much of a good thing. In places the narrative bogs down in a morass of details. Do we really need to know that on August 6, 1993 the author purchased a package of SAD (South African Dried Fruit Co-op, Ltd.) Safari Pitted Dates, Produce of Iraq, in the Bäckerei Celbrodt grocery store in Lüderitz, Namibia? Or the precise workings of parking fee collection in the parking lot of the Coney Island Hot Dog restaurant in Worcester, Massachusetts? In some places, this chapter sounds like Jack Kerouac without the swing. Still, it’s the best part of the book.
The next four chapters report on various aspects of McMenamin’s research program: Chapter 5 on the Garden of Ediacara hypothesis, Chapter 6 on Cloudina, Chapter 7 on Lynn Margulis’ work on the "green jelly ball" ciliate Ophyridium, and Chapter 8 on reconstructions of the Proterozoic supercontinent Rodinia. But the "dramatic heart" of the book is Chapter 9; McMenamin’s account of his discoveries in Precambrian rocks of Sonora, Mexico. The first part of this chapter is a tale of the field trip on which the specimens were found, complete with flat tires, cactus, hostile gatekeepers, and other desert hazards. The specimens McMenamin and colleagues found in the Sierra el Rajón—ostensibly representing several genera of body and trace fossils—are claimed to be the oldest Ediacara-type fossils known. Then some triumphal crowing: McMenamin "deserve[s] to gloat a bit—we’ve been completely vindicated." There’s a contemptuous dismissal of the "Twitya discs," the most plausible rivals for the title of "Oldest Ediacaran Fossils" (Hofmann et al. 1990). There’s the tale of how the venomous reviewers who’d been turning down McMenamin’s grant proposals have been vanquished utterly by his momentous accomplishment. There is also a reproduction of a newspaper clipping about the find, with a color picture of a grinning McMenamin holding one of the fossils, and the sub-headline "Fossils may be Earth’s oldest." (Ouch!) AND, on page 210, there is a page-long footnote, listing by name one hundred and four newspapers around the world that carried the story of McMenamin’s discovery. And after all this fanfare, the Mexican finds hardly appear in the rest of the book—except in Chapter 10, where they form part of his argument to revive Walcott’s old Lipalian Era, with the Sonora section as the stratotype.
What infuriated me, and will infuriate some other readers, is that there is exactly one photograph of one of the Sonora specimens in the entire book (Figure 2.1)—and it’s already been published (McMenamin 1996, Figure 1). Most of the genera that McMenamin claims to have found are not figured at all. There is no information that would let anyone evaluate McMenamin’s finds; readers will just have to take his word that he’s found what he says he has. Several papers with fuller descriptions are apparently in the works—this book could have been worlds better if McMenamin had presented some of that material, or at least waited for it to appear in print. McMenamin smugly recounts an ongoing controversy with a "well-known geologist of the Boston area" over the age of these finds. But a more serious concern that he doesn’t mention is what the "fossils" actually are. The original report of these fossils in Proceedings of the National Academy of Sciences just wasn’t very convincing. While a few seem at least plausible to me, most are indistinct bedding-plane blobs that could easily be artifacts—microbial mat wrinkles, gas escape structures, load casts, or just random marks on bedding planes. Even if they are biogenic, I doubt whether the body fossils can be firmly assigned to the genera that McMenamin has used. Without more data, I don’t really know—but that’s exactly my point: the book presents almost no data, and instead wallows in gleeful self-congratulation. "Perhaps the best thing about paleontology is that the rivals depend on one another for new data," McMenamin says at the end of Chapter 9. True, but he’s not holding up his side of the bargain.
Chapter 11 gives us the "Eureka moment" in which our hero solves the affinity of the entire Ediacara biota. "I have cracked the code of the Ediacaran puzzle," he exults. Briefly, the Ediacaran organisms were multicellular, related to animals but outside of the Animalia. The body organization was established early in development by individual progenitor cells giving rise to separate, nearly independent populations of cells. These populations then grouped together to form the organisms, in a scheme known as "metacellularity." One population made up Cyclomedusa; two growing in one plane would produce Dickinsonia, three in one plane would yield Tribrachidium, three with "bipolar iteration" would yield the frond Pteridinium, and so on. There is even a "gradogram" to present the classification scheme (which isn’t all that original; Zhuravlëv [1993] presented a similar "periodic table of the Ediacarans"). McMenamin concludes that the Ediacarans never went through blastula stage, and so cannot be animals (never mind the fact that not all animals go through typical blastula stages either; e.g. Buss 1987). But he fancy-foots around a great, gaping hole. His grand hypothesis is based on the cell and developmental biology of organisms that are almost exclusively known from fossil impressions of mature organisms in fairly coarse sediments. There is little indication of how on Earth this "metacellularity" is to be tested, or what could ever falsify it. Recent discoveries of phosphatized embryos in the Precambrian (e.g., Xiao et al. 1998) suggest that perhaps it could be tested—or at least that new data could be brought to bear on McMenamin’s hypothesis, even if a formal test isn’t possible. So could better assessment of the anatomy of adults—such as Jenkins’ (1996) discovery of Dickinsonia with what look like internal caecae crossing the external segmentation lines. If Jenkins' interpretation is correct it would hurt "metacellular" interpretation for Dickinsonia. But McMenamin is mostly silent on the matter. He does suggest that more detailed anatomical studies could force us to rethink his theory—and then hands us a quote on p. 213 that "Too slavish an adherence to the doctrine of falsifiability and testability can blind one to the more intuitive (and often ultimately more successful) approaches to scientific work." Oh, well. Those of us who don’t have easy access to the cinnamon rolls and espresso of The Hungry Mind coffee shop in Mount Holyoke (which McMenamin credits for inducing his "Eureka moment") will have a hard time swallowing this chapter.
The rest of the book goes downhill from there, with a blizzard of references, allusions, and quotes from Modern Synthesis dissenters, from Vernadsky to Driesch to Schindewolf to Bergson to Teilhard de Chardin. Ediacaran organisms were not animals, but their convergent evolution of heads shows that they were cephalizing and gaining intelligence, independently of the animals. They communicated with each other chemically, creating the beginnings of a "chemonoösphere." They were replaced by metazoans with even more centralized and complex nervous systems, leading to progressive evolution of ever more complex brains. Convergence is extremely frequent in evolution (which means, by the way, that McMenamin can always quietly explain away any specifically metazoan-like features in any Ediacaran fossil, as he does in footnote 24 to Chapter 11). Thus, there is some vital evolutionary force—more accurately, something inherent in the structure of matter and life—that propels lineages down similar paths each time. [Note: Why this is different from the much less radical concept of evolutionary constraints, I’m not really sure.] Consequently, the neo-darwinian orthodox paradigm is inadequate, neo-darwinism is dead, neo-vitalism triumphs, yadda, yadda, yadda.
Again and again—the whole grand scheme rests on hypotheses that may not be testable at all, and McMenamin usually doesn’t even bother to suggest possible tests. Some real difficulties appear when McMenamin’s ideas are critically examined. For instance, McMenamin states that "cephalo-Ediacarans" such as Spriggina bore a differentiated "head" with sense organs. That implies fairly sophisticated embryonic development, as well as something like nerves for transmitting sensory impulses. Could an organism made up of nearly autonomous, "selfish" cell families have undergone any developmental process like that? And, given a "metacellular" body plan, how likely would the evolution of an integrated nervous system be? Far deeper than questions like these, implicit in the entire book, is an enormous unquestioned assumption (not, to be fair, unique to McMenamin) briefly brought up in Chapter 4 and then accepted without criticism for the rest of the book. The assumption is that all "Ediacara fossils" are members of the same high-level taxon, and must fit the same plan of construction. Surely this is grand-scale "shoehorning," as Gould put it. It’s clearly not true for, say, the Burgess Shale. Why should it apply to the Ediacarans? In fact, if convergence is so widespread in evolution, why assume that the Ediacarans form only a single clade with a single bauplan? But none of this seems to bother the author: "Intuition trumps reason," he writes on p. 267.
"If we try to purge science of the irrational and to banish intuitive approaches in science, as many orthodox neo-darwinists have tried to do," McMenamin says on p. 266, "we risk destroying science." That’s indisputable. Science is a human activity and it draws on all the faculties of the human mind, including the irrational, intuitive, and creative. But that doesn’t mean that intuition and irrationality should be allowed to bounce around, unrestrained and untested. That, if it ever came to pass, could also wreck science. Scientific creativity, as precious as it is, must ultimately be subject to the humdrum business of reasoning, testing, and falsification. Otherwise, there’s no difference worth mentioning between The Origin of Species and Naked Lunch. There has to be some balance among the different human faculties—and The Garden of Ediacara never finds it. To reverse a Russian proverb: the book’s occasional pieces of valuable data and flashes of insight are kak lozhka myoda v bochke dyogta—like a spoonful of honey in a barrel of tar.
See References.
Copyright: Palaeontologia Electronica, 15 March 1999
