* This is the latest installment of “Problematica.” It is based on a paper I wrote a few years back, which now resides in the PhilSci-Archive. Improbably, the paper seems to have attracted a (very) modest readership, probably because it has a fun title. It was even cited by the sneaky creationist website “EvolutionNews” in a story that alleges a Darwinian conspiracy against Mark McMenamin. (Nope!! People dunk on McMenamin because he says a bunch of silly shit. Also, my paper is cited out of context. The author makes it seem like I call the Triassic kraken hypothesis “dangerous” because it dares to speak heterodoxy to power. In fact, the term “dangerous” here means epistemically dangerous, or heedless of the basic norms of scientific inference.) Anyway, here is a lightly reworked version of the paper for your conspiratorial consideration. This is Part 1 of 2. (Click here for Part 2.) Problematica is written by Max Dresow…
Monday, October 10, 2011
The halls of the Geological Society of America meeting buzzed with anticipation.
“Have you heard?”
“About the kraken guy?”
“Mark McMenamin. Apparently he teaches at some little school out east.”
“I heard he’s a kook.”
“He’d have to be, wouldn’t he? Anyway, I’m going to head over early to make sure I get a seat.”
“Let me know how it goes. I’ll be doing, like, anything else.”
The talk on everyone’s lips began at two in the afternoon. Half an hour before, the medium-sized conference room had filled to capacity. Latecomers were forced to huddle outside its open doors and crane their necks at the spectacle. Later they would leave, snickering and shaking their heads. Serious minded geologists cried foul. Others cracked jokes. The press, who had caught wind of the talk in advance of the meeting, ate it up. Major outlets do not usually cover meetings of the GSA. The time when the general public cared about meetings of geologists had drawn to a close in the United States about 150 years ago. Still, even the most hardened philistine had to admit that giant sea monsters make great copy.
The talk bore the B-movie title “Triassic Kraken,” and the rather more academic subtitle “The Berlin Ichthyosaur Death Assemblage Interpreted as a Giant Cephalopod Midden.” Its abstract, co-authored by the husband and wife team of Mark McMenamin and Diane Schulte McMenamin, makes for good reading.
The Luning Formation at Berlin-Ichthyosaur State Park, Nevada, hosts a puzzling assemblage of at least 9 huge (≤14 m[eter]) juxtaposed ichthyosaurs… comparable to sperm whales… Adjacent skeletons display different taphonomic histories and degrees of disarticulation, ruling out catastrophic mass death, but allowing a scenario in which dead ichthyosaurs were sequentially transported to a sea floor midden [or refuse heap]. We hypothesize that the [ichthyosaurs] were killed and carried to this site by an enormous Triassic cephalopod, a “kraken,” with [an] estimated length of approximately 30 m[eters], twice that of the modern Colossal Squid Mesonychoteuthis. In this scenario, [the ichthyosaurs] were ambushed by a Triassic kraken, drowned, and dumped on a midden like that of a modern octopus.
The Berlin Ichthyosaur Death Assemblage in Berlin-Ichthyosaur State Park, Nevada
This is perhaps excitement enough for one talk, but the authors go on to note that the ichthyosaur vertebrae “are arranged in curious linear patterns with almost geometric regularity.” What follows would become an infamous claim:
The proposed Triassic kraken, which could have been the most intelligent invertebrate ever, arranged the vertebral discs in biserial patterns, with individual pieces nesting in a fitted fashion as if they were part of a puzzle. The arranged vertebrae resemble the pattern of sucker discs on a cephalopod tentacle… Thus the tessellated vertebral disc pavement may represent the earliest known self-portrait.
The alleged self-portrait juxtaposed with a modern octopus’s arm
Media reports of the talented cephalopod began to trickle out before the talk was even over. All relied on the press release from the GSA and presented the case for the “kraken” in a generally positive light. However, with the entry of the science blogs into the picture, the tone of coverage took a turn. Biologist PZ Meyers (Pharyngula) called the whole thing “rather pathetic,” and complained that the evidence for self-portraiture was particularly thin. “[D]ump a pile of Necco wafers on a table, and I’ll see a picture of squid suckers.” Freelance writer Riley Black (then writing under the name Brian Switek) added a piece for WIRED titled “The Giant Prehistoric Squid That Ate Common Sense.” She too was critical of the evidence, but reserved her harshest criticism for science journalists: “Whether you think the ‘kraken’ story should have been reported or ignored due to lack of evidence, the fact remains that journalists should have actually done their jobs rather than act as facilitators of hype.” Finally, the vertebrate paleontologist Donald Prothero weighed in on the blog of the Skeptic Society. His piece, titled “Octopus’ Garden in the Shale?,” is perhaps most notable for its assessment of McMenamin himself:
The minute I saw the press release, I suspected something like this was going to happen. McMenamin is well known for his, shall we say, bizarre ideas or unorthodox ways of thinking… Those of us with a history in the profession know better than to take his wild claims too seriously.
Major outlets, alas, were not so wary. And so the Triassic kraken was released on a rapt but ingenuous public.
The kraken was not long for the news cycle, but this was hardly the end of the line for the prehistoric beast. It first resurfaced in a magazine article summarizing evidence for the hypothesis (McMenamin 2012), before showing up for a second romp at the GSA in 2013 (McMenamin and Schulte McMenamin 2013). Another round of media attention followed, centered on McMenamin’s claim to have found independent evidence for the kraken in the form of a beak. Eager to forestall the hype, the Paleontological Society issued a response by David Fastovsky, which appeared in most news stories discussing the abstract. Then things settled down. The kraken was last seen in the ninth chapter of McMenamin’s book, Dynamic Paleontology, where it is claimed that the Triassic kraken hypothesis “has survived all tests to date, and currently stands alone as the best explanation for the strange collection of large ichthyosaur bones at Berlin-Ichthyosaur State Park” (McMenamin 2016, 131). Few outside McMenamin’s household seem to share this assessment.
What's the Matter with a Giant Kraken?
The Triassic kraken hypothesis is almost certainly wrong. As critics observed, evidence for a kraken is wholly circumstantial (pace later reports of a beak), and the idea that the bonebed is a midden flouts the principle of parsimony. Claims of hyper-intelligence are particularly extravagant. Writes Black, “I guess a giant, ichthyosaur-eating ‘kraken’ wasn’t enough. A squid with a stroke of artistic genius was clearly the simplest explanation for the formation of the bonebeds.”
But so what? It is no sin for a scientific hypothesis to be wrong. Nor is it necessarily wicked to sin against parsimony. It is true that simplicity provides a convenient standard for evaluating explanatory claims. But it is hardly unheard of for more complicated hypotheses to win out over simpler ones. Even a seemingly implausible hypothesis may have its virtues. In a famous paper, the American geologist William Morris Davis defended the value of “outrageous” hypotheses on the grounds that judgements of outrageousness are calibrated to contemporary knowledge, which is fallible (Davis 1926). As he observes, many things that geologists now take for granted were once regarded as outrageous. But this just means that many advances in geology were “made by outraging in one way or another a body of preconceived opinions” (464). It follows that scientists should speculate—wildly, even—assuming their speculations do not controvert robustly established results (and sometimes even then). Adrian Currie has recently made a similar suggestion: “Especially when the going gets tough… historical science should be wild, messy and creative [i.e., speculative]” (Currie 2018, 291).
Mark McMenamin, professor of geology at Mount Holyoke College in Massachusetts
This essay is about wild, messy, and creative speculation in geohistory. Specifically, it is about what I call dangerous speculation and the circumstances under which it is likely to be well-received. Dangerous speculation is speculation that departs from an ideal of well-controlled speculation in one or more of several ways. These departures correspond to familiar epistemic sins and are individually sufficient to render a hypothesis suspect. But an epistemically suspect hypothesis may still be regarded as viable under certain circumstances. This essay explores this phenomenon using examples from geohistory. All are outrageous and almost certainly wrong; in addition to the Triassic kraken, I will consider the “Nemesis” (or “Death Star”) hypothesis, as well as Adolf Seilacher’s interpretation of the Ediacaran biota (the “vendobiont hypothesis”). But these outrageous hypotheses elicited very different reactions from the paleontological community. Why? What accounts for the relatively enthusiastic reception of the vendobiont hypothesis, the more complicated reception of Nemesis, and the heckling dismissal of the Triassic kraken? And what epistemic lessons, if any, can be extracted from the comparison?
This essay has two parts. In the remainder of Part 1, I introduce the remaining outrageous hypotheses, paying special attention to their motivation and reception. Then, in Part 2, I develop my account of “well-controlled” and “dangerous speculation” and use it to analyze the reception of the three hypotheses.
Death Star and the Quilted Pneu
The Nemesis Hypothesis
Few paleontological phenomena are as dramatic as mass extinction. Although the category is inherently fuzzy, paleontologists recognize five major extinction events in the past half billion years, with species losses ranging from sixty to ninety percent per event (Marshall 2023). There are also a host of smaller extinctions in the fossil record, including some that may warrant the epithet “mass extinction.” It has long been suspected that these extinctions occur more or less randomly throughout the geological column. However, in the 1980s, two paleontologists produced an analysis suggesting that major extinctions have occurred with an approximately 26-million-year periodicity over the past quarter billion years. This is the source of what has been called “the Nemesis affair” (Raup 1999); but before coming to Nemesis itself, it will be useful to fill in a bit more of the historical context.
The study of mass extinction was forever changed in 1980 when Walter Alvarez and colleagues proposed that a large body impact polished off the non-avian dinosaurs (and many other groups) at the end of the Cretaceous Period (Alvarez et al. 1980). Prior to this time, most geologists favored earthbound causes for major extinctions: shifts in climate, worldwide mountain-building episodes, volcanism— pretty much anything you can think of. Yet as evidence mounted for an impact at the end of the Cretaceous, a vogue set in for extraterrestrial causes of the catastrophic sort (Sepkoski 2020). Not a few paleontologists wondered if large body impact might explain all the major extinctions in the fossil record: a possibility Alvarez and colleagues suggested in observing that the number of major Phanerozoic extinctions (five) “matches well the probable interval of about 100 million years between collisions with 10-km-diameter objects” (Alvarez et al. 1980, 1107).
Jack Sepkoski (left) and David Raup (right)
One of the people who wondered about this was David Raup. A leading analytical paleontologist, Raup was greatly exercised by the excitement surrounding the Alvarez hypothesis. In addition, he was interested in the waxing and waning of taxonomic diversity over time: an interest he shared with his junior colleague J. John (“Jack”) Sepkoski, Jr. (Sepkoski 2012). Like Raup, Sepkoski was an analytical paleontologist, who had become well known for compiling data on the stratigraphic ranges of all known marine fossil families. Using these data, Raup and Sepkoski published an analysis in 1982 purporting to show that “five mass extinctions are clearly defined in the [marine fossil record]” (Raup and Sepkoski 1982, 1502). But the duo was not finished, and two years later, they returned with an altogether more startling conclusion. Based on a qualitative examination of patterns in Sepkoski’s data, Raup and Sepkoski noticed that “[major] extinctions seemed to be regularly spaced in time, or at least far more regularly spaced than if they had been placed at random” (Raup 1999, 115). Intrigued, they used “every standard and non-standard mathematical technique [they] could find or devise” to refute the hypothesis, but to no avail (122). This led them to claim that “a 26-[million-year] periodicity” is an “inescapable” feature of the post-Permian extinction record (Raup and Sepkoski 1984, 804). Somehow, like clockwork, the earth had tipped into calamity at regular intervals over a quarter billion-year period, with only two “misses” against eight statistically significant “hits.”
There was a problem, however. Assuming extinction periodicity is real, what on earth could have caused it? Raup and Sepkoski could think of no earthbound process that operates regularly over so long an interval. So they reasoned that a non-earthbound cause was more likely, like “the passage of our solar system through the spiral arms of the Milky Way” (Raup and Sepkoski 1984, 804). This seemed to operate on about the right time scale, and would be suitably periodic in its effects on the biosphere. However, the suggestion served mainly as an example of the kind of cause that might be implicated in producing a pulse of extinction every 26 million years. In Raup and Sepkoski’s words, “much more information is needed before definitive statements about causes can be made.”
A graph of major extinctions showing apparent periodicity, from Raup and Sepkoski (1984)
The publication of Raup and Sepkoski’s paper caused a stir, in part because it appeared in PNAS and so evaded the scrutiny of an ordinary review process (Raup 1999). Paleontologists were quick to criticize it, claiming, for example, that the data were too incomplete to permit a demonstration of periodicity, or that uncertainties in dating scuttled the whole enterprise (Hallam 1984; Hoffman 1985). Lurking behind these objections was the intuition that extinction cannot be periodic in a world governed by haphazard Darwinian processes. Yet scientists outside of paleontology evidently lacked these hang-ups, and seemed to take claims of periodicity at face value. Astronomers in particular were well disposed, and in the April 19, 1984 issue of Nature, five papers appeared that proposed extraterrestrial mechanisms for periodic extinction. Two of these proposed that extinctions were caused by the movement of the sun relative to the galactic plane (Schwartz and James 1984; Rampino and Stothers 1984); but given that the sun is now close to the galactic plane, and we are not due for another extinction for 14 million years, these faced serious difficulties. Two others summoned a companion star to do the killing (Davis et al. 1984; Whitmire and Jackson 1984). One even gave the star a name: Nemesis. Perhaps inevitably, it was later vulgarized to the “Death Star” hypothesis.
The Death Star hypothesis imagines a dim companion star to our sun traveling on a highly eccentric (non-circular) orbit. Once per revolution— that is, once every 26 million years— the star passes through the Oort cloud: a hypothetical envelope of comets lying beyond the edge of our solar system. This produces a gravitational disturbance that sends a shower of comets hurtling into the space of the inner planets. It is the impact of one or more of these comets with the earth that triggers mass extinction, although the comets may also miss the earth or fail to trigger an extinction, accounting for anomalies in the 26-million-year pattern.
A graphic about the Nemesis hypothesis, from the December 18, 1984 issue of The New York Times
Now, this must rank as an outrageous hypothesis, not only because it accepts the evidence for periodicity at face value, but also because it presses into service two hypothetical entities, Nemesis and the Oort cloud, one of which is known only from the extinction data. For some, this was all it took to rule the hypothesis out of court. An anonymous New York Times editorialist ended their letter by scoffing that “Astronomers should leave to astrologers the task of seeking the cause of earthly events in the stars” (Anonymous 1980). The jeer was not representative of the generally positive treatment Nemesis received in the popular press. Yet it probably captured the dominant feeling among paleontologists, many of whom had yet to warm to the Alvarez hypothesis, to say nothing of extinction periodicity (Raup 1999). British paleontologist Anthony Hallam stated the obvious when he wrote that “[in] assessing the value of these1 [astronomical hypotheses] it is clearly necessary first to scrutinize the Raup and Sepkoski analysis on which it is based” (Hallam 1984, 686). His skepticism seemed to be confirmed when paleontologist Anthoni Hoffman published an analysis purporting to show that “evidence for [periodicity] is strongly contingent on arbitrary decisions concerning the absolute dating of stratigraphic boundaries, the culling of the database and the definition of what is mass extinction as opposed to background extinction” (Hoffman 1985, 659). At least this indicated that it was overzealous to claim, as Raup and Sepkoski had, that periodicity is an “inescapable” feature of the post-Permian fossil record.
Periodicity had at least one prominent advocate, however, and it just so happened to be the paleontologist with the biggest platform of all. This was Sepkoski’s PhD supervisor Stephen Jay Gould, who threw his considerable weight behind the Nemesis hypothesis in an essay of 1984. Gould stopped short of saying that he expected Nemesis to be found. He only said that he hoped it would be found, and that he regarded the prospect as a respectable one. He pleaded, however, that if astronomers should discover the star, they would not name it after the “personification of righteous anger” (Gould 1985, 447). This would only reinforce an outdated view of mass extinction in which the vanquished literally get what they deserve. The new scientific understanding of mass extinction demanded a more apt name. Gould recommended “Siva,” the Hindu god of destruction, whose “placid face represents the absolute tranquility and serenity of a neutral process, directed toward no one but responsible for maintaining the order of the world” (450). He added, blushingly, that “I can only hope that I will not be remembered as the man who campaigned with a new name for [a] nonexistent [star].”
Alas, it has been almost forty years, and no sign of Nemesis has been found. This is not for want of effort. Multiple astronomical surveys since the 1980s have searched for a companion star or similar celestial object, and all have come up empty. It thus seems that Nemesis does not exist. The hypothesis of extinction periodicity, on the other hand, refuses to go away. Most recently, Adrian Melott (an astrophysicist) and Richard Bambach (a paleontologist) argued for a 27 million year periodicity in extinction spikes, although not necessarily for periodic mass extinctions (Melott and Bambach 2010). Their preferred explanation is that “some periodic stress… at a 27 [million year] period, adds a background on which a variety of pulse events from a variety of causes [may be] promoted to major extinctions events by the additional stress” (Melott and Bambach 2017, 919). They place no bets on the identity of the stressor, but mention Nemesis only in passing, in a sentence stating that any mechanism for periodicity should “require no new physics and avoid the irregularities that beset the Nemesis and galactic oscillation models” (see also Melott and Bambach 2010). The Nemesis affair is accordingly over.
The Vendobiont Hypothesis
The soft-bodied organisms of the Ediacaran biota are an enduring puzzle in evolutionary paleontology. Dating from just before the Cambrian Explosion, they are preserved as a collection of shallow casts and molds resembling no living animals in particular. They came to prominence through the efforts of Martin Glaessner, an Austrian paleontologist who assigned most taxa to living groups on the basis of supposed structural homologies. Pancake-like Dickinsonia he described as a segmented worm (Glaessner 1961). Foliate Rangea he described as a soft coral or “sea pen” (Glaessner 1959). Slug-like Kimberella he assigned to the medusoids (Glaessner and Wade 1966). And the enigmatic Parvancorina and Praecambridium he assigned to the arthropods (Glaessner and Wade 1971). Glaessner’s interpretation was not quite uncontested. In the early 1970s, a German paleontologist working in present-day Namibia proposed that a group of frondose Ediacarans were actually colonial organisms lying between animals and plants on the evolutionary tree. These challenges notwithstanding, Glaessner’s interpretation was so successful that he could claim near the end of his life that “no major changes in the assessment and composition of the fauna have been made in the last 25 years” (Glaessner 1984, 51).
Iconic Ediacaran fossils, including Spriggina (top left), Kimberella (left center), Avalofractus (bottom [far] left), Aspidella (bottom [center] left), Charnia (center), Dickinonia (top right), and Parvancorina (bottom right)
Glaessner wrote these words in 1984. At the time, the basics of his interpretation seemed unassailable. Awards and recognition rolled in. The future of Ediacaran paleontology looked to be a glorified exercise in what Thomas Kuhn called “mopping up work.” Then came Adolf Seilacher.
Seilacher’s interpretation of the Ediacaran biota was based on what he termed “constructional morphology” (Seilacher 1989). Regarded as a method, it involved the analysis of form in relation to three factors: history (“phylogenetic tradition”), adaptation (“biological function”), and Bautechnik (“morphogenetic fabrication”). The actual analytic procedure was often opaque, but what was clear was that its purpose was to avoid the pitfall of treating any one factor as the key to understanding. This is what Glaessner had done when he focused on structural homologies (phylogenetic tradition) to the neglect of functional and fabricational considerations. Seilacher, by contrast, set out to interpret the impressions on “purely constructional principles”— an “uncomfortable” strategy, he admits, but one that is presumably necessary since “modeling the Ediacaran body impressions in terms of modern phyla appears to be in conflict with basic functional necessities” (Seilacher 1989, 232).
It is important to be clear about what it means to interpret fossils on “purely constructional principles.” Basically, it means to reconstruct the morphological design of extinct taxa without the help of metazoan analogies, and then to interpret this design in functional terms, again, without the help of metazoan analogies. This is indeed an “uncomfortable” strategy, since it practically requires interpretations to be highly speculative. But it’s also just plain difficult, since in eschewing comparisons with living organisms, it declines the assistance of a powerful method for constraining interpretations. It’s a bit like fighting with an arm tied behind one’s back— something that’s generally a bad idea, unless one is in the habit of using that arm to punch oneself in the nose.
Seilacher’s illustration of “vendozoan” morphology, based on the shared constructional element of the pneu structure (middle row, center). From Seilacher (1989)
In any event, Seilacher’s constructional analysis is a particularly outrageous bit of paleontological speculation. It holds that many iconic Ediacaran fossils are examples of an “exotic principle of organismic construction” unique to the Ediacaran interval (Seilacher 1989, 230). This principle is based on a shared constructional element called a “pneu structure,” which Seilacher describes as a cylindrical tube filled with jelly. Ediacaran organisms were compounded of many such structures, quilted together to produce “carpets” reminiscent of air mattresses (see the figure, above). It is not immediately clear how they made a living. They evidently lacked mouths and anuses, and led a sessile existence on the seafloor. Perhaps they fed upon the microbial mats that lined the sea bottom like a sticky film, but Seilacher’s hunch was that they harbored microbes capable of extracting energy from seawater (a conjecture dreamed up by none other than Mark McMenamin!). Whatever the story, it is at this juncture that “the disadvantage of [the purely constructional] approach” is most evident, since all the investigator has to go on are the “basic principles of physiology,” and these provide little guidance for interpreting particular specimens (236–7).
Seilacher (1989) did not venture a guess as to where his vendobionts resided on the tree of life. However, in his (1992) he made the suggestion that they constitute a new kingdom of life (the Vendobionta) that became extinct at the end of the Precambrian.* Possibly this is because the lifestyle permitted by their “quilted hydrostatic construction” became obsolete with the advent of mobile predators in the early Cambrian. Vendobionts simply could not hack it in a world of jaws, muscles, and eyes and for that reason perished en masse around the time of the Cambrian radiation. But why? A big reason was that vendobionts were unicellular (Seilacher thought), and this limited their capacity to mount an evolutionary response to predation pressure. Multicellular organisms have a capacity for tissue differentiation and specialization that the vendobionts simply lacked, and because of this, vendobionts were basically a buffet line for early bilaterian predators. Bummer.
[* Seilacher would later revise this interpretation, first reinterpreting the Vendobionta as an extinct animal phylum (Buss and Seilacher 1994), and then as an extinct class of giant rhizopod protists (Seilacher et al. 2003).]
How were these conjectures received? Certainly they raised some hackles. Emblematic was the response of Jim Gehling, an Ediacaran paleontologist whose affability is as fabled as Seilacher’s observational powers. In a festschrift honoring Martin Glaessner, Gehling subjected Seilacher’s conjectures to a searching examination and critique. His basic claim was that attempts to assess “[the] construction and life style of Ediacaran organisms should be preceded by a close study of the preservational characteristics of particular taxa, from as many different settings as possible” (Gehling 1991, 185). In South Australia, for example, many Ediacaran impressions are found in trace-fossil bearing sandstones: an unlikely repository for soft-bodied fossils. This suggests that one of two things must be the case. Either “something was different about the Ediacaran organisms” (Seilacher’s position) or “the process of preservation was different.” Gehling favored the latter view, in part because “sandstones of Ediacaran age bear textures rarely described in both older and newer sediments.” Particularly noteworthy are the elephant skin textures indicative of the “prolific development of cyanobacterial mats” (218). These would have served “both to erosion proof the substrates occupied by the organisms [after burial]… and to initiate immediate mineral encrusting of organic surfaces.” This meant that there was no need to resort to exotic conjectures to explain the fossilization of Ediacaran organisms. Unusual taphonomic conditions could do the job.
Dickinsonia menneri from the White Sea coast of northern Russia. This specimnen shows signs of damage and regeneration on one end
This was probably Gehling’s most damning criticism, since Seilacher was a leading expert in the science of fossil preservation. But no less serious were his allegations that Seilacher misinterpreted the fossils themselves, perhaps because he was not sufficiently acquainted with them. Writing of Dickinsonia, Gehling observed that “[e]xamination of several hundred specimens of this taxon reveals the presence of several characteristics that the ‘air mattress’ model cannot accommodate” (Gehling 1991, 195, emphasis added). For example, most specimens show a clear distinction between their front and back ends, contrary to Seilacher’s claims. Some specimens also exhibit a crinking of individual segments suggestive of muscular contraction and the possibility of locomotion. In Gehling’s view, these features “point to Dickinsonia as a functioning coelomate-grate [animal], able to react to sensory input” (198). Similar difficulties attached to other of Seilacher’s interpretations, leading Gehling to conclude that it is “[o]nly with a very broad brush [that] all Ediacaran organisms [can] be represented as fractal growth variations based on the same units of construction” (202).
Despite these criticisms, the vendobiont hypothesis “initially attracted considerable support from paleontologists (Dunn and Liu 2019, 513). Arthropod specialist Jan Bergström observed in 1991 that “many of the [Ediacaran] organisms… probably belong to a group of ‘quilted organisms’ which may not be animals and exhibit no close similarity to bilaterians” (Bergström 1991, 32). Guy Narbonne made a similar claim in 1998, arguing that some Ediacarans probably represented “a failed experiment in Precambrian evolution” (Narbonne 1998, 1). These remarks show that certain components of Seilacher’s interpretation found uptake among Precambrian paleontologists. Yet arguably a more significant effect of Seilacher's work was to “turn the discussion of Ediacaran affinities from a monolith [into] a free-for-all” (Narbonne 2005, 431). In the fifteen years following (Seilacher 1989), members of the Ediacaran biota were interpreted as protists, lichens, fungi, colonial prokaryotes, and extinct photosynthetic “metacellulars” (the last suggestion was McMenamin’s). At the same time, the vendobiont hypothesis “stimulated research in comparative biology, taphonomy, and ecology in an attempt to deduce the affinities of these pivotal fossils.” This has undermined the vendobiont hypothesis in anything resembling its provocative, original form. Still, what is perhaps more significant is that research on diverse aspects of Ediacaran biology remains a going concern. Today there are more researchers studying Ediacaran fossils than ever before, and this seems unlikely to change any time soon.
* * *
So much for the outrageous hypotheses. In Part 2, I will review some recent philosophical work on speculation in geohistory and develop my account of “well-controlled” and “dangerous speculation.” Then, I use these resources to analyze the reception of the outrageous hypotheses and to extract some provisional epistemic conclusions.
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