"We hold these truths to be non-evident" ... beliefs held with no visible means of supportPeople often hold (and may fiercely defend) beliefs that are utterly lacking in supporting evidence (in the conventional sense of scientifically-admissible, independently-verifiable evidence). For example, many Americans believe in: the existence of guardian angels (65%), and that some god is responsible for their existence and plight and answers their prayers (92%), and UFOs (34%), and ghosts (34%).
People tend to hold their non-evident beliefs even in the face of direct evidence to the contrary although they cannot provide evidence in support of their belief. These beliefs are often contentious and dividing, and they are often expressed as negative beliefs, i.e., beliefs against a given proposition such as: evolution (39%), or that humans are contributing to global warming, etc. This last example is useful here. Experts in global warming are not unanimous; they present competing explanations, often with distinct lines of evidence, then debate how to resolve the discrepancies, which often requires additional evidence gathering. Occasionally the arguments reduce to heated ad hominem attacks on the advocate of an opposing view, but generally that is seen for what it is.
There's another sort of non-evident belief that should be mentioned, that being a belief that is held during a period of one's life (Easter Bunny, Santa Claus, Tooth Fairy) until the need for the belief passes, and what remains is a quaint fable. The former-believer might later feel they were duped by the agents (parents or institutions) responsible for pushing that belief. Of course, more insidious beliefs than Easter Bunnies are held life-long, and initially pushed on the naive, then repeatedly reinforced precisely because they are very useful. So why do so many believe sauropods went around with their necks pointing up in the air?
the non-evident belief that sauropods held their heads high
Consider the belief that sauropods held their heads up high off the ground (some believe they held their necks like that of a swan or giraffe, others believe the neck was just cranked upward a bit at the base, which was the new look for last year's spring fashion parade). In light of how many rubber dinosaurs have been given to children over the decades, the percentage of the lay pubic that holds this belief is likely quite high (the poll data has not in for this particular belief, but I would presume it's up with belief in angels, and way more than belief in alien abductions).
Belief in Elevated Sauropod Necks (ESN) has three versions, or sects:
The three sects of ESN belief are meant to be mutually exclusive. But there might be some devout believers that sauropods had vertebrae that bent the neck up, assisted by thick wedges of cartilage, and a behavioral propensity to further crank the neck up to vertical, or beyond. Some have even created artwork depicting their visions.
So considering the evidence, are these beliefs non-evident in the sense of the Easter Bunny (no direct evidence exists one way or the other, but the story is nice), or does it require a certain state of denial to maintain the belief? Consider them one at a time:
ESN v.1. Hard osteological evidence for wedge-shaped vertebrae at the cervicodorsal transition is either apocryphal or outright fabricated (out of plaster or pen-and-ink). Fabrications can be revealed for what they are, but if people want to belief that some necks were actually bent to point the neck up in the air, well, those are the true believers in ESN v.1. Consider, for instance, the Camarasaurus at the Smithsonian displayed on its side about to be dismembered by an Allosaurus. The original fossil material (DNM 24) is in the USNMH collections of the USNMH as a block, with the vertebrae preserved in a death pose with the zygapophyses displaced out of articulation. But the reconstruction on the display floor depicts, with some artistic license, the same curve to the neck with the zygapophyses all in articulation and undeflected (falsely suggesting ONP). Similarly, the Yale Peabody Museum's Apatosaurus excelsus is mounted with a lovely sigmoid curve to the neck. The neck appears to be in ONP, with the zygapophyses all aligned and the vertebrae apparently undeflected. But ascend a ladder to get close to the cervical vertebrae of this historic specimen, and close inspection revealed that under layers of dark varnish, the vertebrae were heavily restored. Many of the zygapophyses were real, but embedded in artfully sculpted plaster. The curve of the neck came first, apparently, and the sculpting then created to make the vertebrae all fit together (unfortunately, as if in ONP). Tapping on the bones revealed what was real and what was "artistic restoration". So much for looking at "original specimens" (unless you are allowed to tap on them). ESN v.1 is slowly dying out, at least among those who examine the actual osteological evidence. As regards artwork, illustrations that depict osteological adaptations (keystone or otherwise distorted vertebrae at the base of the neck), e.g., of Brachiosaurus, Euhelopus and Mamenchisaurus, might be regarded as "artist's impressions" of how the neck would look if only it had a neck that bend upwards, analogous to visions depicted in religious iconography.
Next, consider ESN v.2, the belief that wedges of cartilage were responsible for bending the otherwise straight neck into an upward curved. This has actually appeared in print, but usually the belief is expressed as a negative belief, e.g., when a museum curator pontificates "we really don't know about how much cartilage was between those vertebrae, so perhaps there was enough of a wedge to force the neck up into the air, ladies and gentlemen. I'll take one more question. Yes, you in the back." This belief seemed the last refuge for those who believe sauropod necks bend skyward without effort, until ESN v.3 emerged.
So, regarding ESN v.3, the true believers might well agree that the bones and joints of the base of the neck are straight (either straight and horizontal for a diplodocid, or straight and slightly upward sloping for a camarasaurid or brachiosaurid just because the forelimbs are so tall) but they bend upward because of propensity to elevate the neck by dorsiflexion (some might call it extending) the neck at the base. Maybe even "maximally dorsiflexing", as in lifting the neck as much as the joints would permit, all at the base of the neck. Believers cite positive supporting evidence, in the form of the behaviour of modern animals. But the manner in which carefully selected supporting evidence is presented while counter-evidence is suppressed, will be addressed elsewhere. Here, I focus on the ideas behind the beliefs, not the validity of the beliefs.
I should place myself in this space of beliefs. I firmly believe (but am willing to have my belief shattered) that as regards both osteology and arthrology all sauropod necks are straight extensions of the anterior dorsal column So I am a devout non-believer in v.1 and v.2. Regarding v.3, the behavioral option, that sauropods would hold their heads up, ... well okay, some of the time, otherwise they'd likely not have had any ability to dorsiflex. But how high, and how frequently, and why, ... we'll get back to you on that.
Mike Parrish and I conjectured that ONP is the "characteristic pose" (CP) of an animal, meaning not just the way that their axial skeletons are mounted without deflection in museums, but how they would be found alive and alert, just standing around and not engaged in much anything. Based on our sampling of birds, reptiles and mammals, we believed that ONP is a reliable predictor of the animal's behaving "characteristic" or "neutral" pose. Andreas Christian and Gordon Dzemski showed, however, that an ostrich does not characteristically hold is neck in a neutral (undeflected) state. So much for our sweeping statement that ONP = CP for all vertebrates ("with no known exceptions"). The ostrich is indeed a clear exception, and seemingly an exception of some importance because of its similarity to sauropod necks. Since then, a few other exceptions have emerged. So what do these exceptions mean? Exceptio probat regulam in casibus non exceptis?
Mathematically, exceptions can be used to disprove some conjecture of the form: ∀ x: P(x). But we are dealing not with mathematics, but with organisms. If finding a counterexample (or a few counterexamples) were able to invalidate or disprove a general trend in biology, then one could play that game in either direction. So the conjecture that "all tetrapods maximally extend (dorsiflex) their necks at the base", and our being tetrapods, would suggest we go around like this
And one more thing. Beliefs are often applied without regard for consistency. Imagine one holds the belief that all tetrapods bend their necks up maximally at the base (and then bend down again at the head end to keep the head level, of course). You believe it whether extant and extinct. Well, that would allow one to believe that their brontosaurus rubber toy was accurate, standing proud with head in the air. But what about all the other dinosaurs? Triceratops and Ankylosaurus, for example, were always posed with necks that were straight or even even drooped down slightly from the shoulders. So does one then believe their necks also bent upward stiffly? That would be a particular problem for Triceratops, because its cranial cervicals were fused into a solid bar, so its head would be stuck pointing up in the air, not horizontally and looking all mean. And what about the fierce Tyrannosaurus rex? Its neck was already bent into an aesthetically-pleasing sigmoid curve. So would one then believe it was kinked into an even tighter curve when just hanging around? No, the problem with beliefs, especially beliefs that don't hold up to scrutiny, is that they have to be applied selectively.
Copyright © 2011 Kent A. Stevens, University of Oregon