The hearsay principle in science
deutsche Version

Deviating from the rule that statements in scientific papers should be substantiated by one's own observations and logic, there is a considerable fraction of statements, interpretations, and suggestions that are essentially mere non-critical adoptions of what had been said or written before. Well, this may be not bad in itself since the very progress of science is based on the reliability of the results of previous scientific work. However, since not all scientific work is thoroughly reliable, one should not be surprised to meet lots of unsubstantiated stuff that survives in the scientific literature by way of repeated non-critical adoption.
It would be a waste of time to systematically collect and analyze examples of this kind but the few randomly selected items discussed below may draw the reader's attention to the broader malady which seems to more or less pervade all science.
What follows here may be regarded as complementary considerations concerning the "Misconceptions" and "Errors" chapters on this website.

Mineral deposition by circulating solutions
Apparently, some terms had been so cleverly coined that they seem to have got a self-explanatory power. The term "circulating solutions" is often used in a way as if it were an inherent property of solutions to circulate. Circulation needs a driving force, as a temperature difference. Warm ground water below and cold water above are not in equilibrium so that the cold water sinks down at some place while the warm water comes up at another place, cools down and joins the cold water above, thus sustaining a circulating flow. Minerals dissolve in the depth and precipitate above. This mineral deposition by circulating solutions has been proposed and repeatedly adopted as an explanation of agate formation in closed cavities and of flintstones in chalk deposits although no cause of a circulating flow is thinkable in those cases.
Apparently the proponents of the circulating solutions idea had not been familiar with the fundamental process of diffusion, hence they had been unable to imagine substance transport without fluid flow. Diffusional substance transport or flow proceeds through the solid substance and along the surface. Cracks and grain boundaries make easy diffusion paths in the solid. (Cracks can also act as diffusion barriers precluding a diffusional flow across.) Since diffusion in liquids is quicker than in solids, liquid-filled cracks facilitate substance transport also in the absence of liquid flow.
Finally it can be stated that the over-use of the favourite term "circulating solutions" must be avoided since it precludes understanding of what is really going on.

"Directed explosion pressure wave" of volcanic eruptions
The flattening of vegetation as a result of an explosive volcanic eruption has repeatedly been explained by a "directed explosion pressure wave", probably because this term gives rise to vivid imagination. Doubtless there are pressure waves emerging from eruptions: They are heard as a thunderung noise since pressure waves in air are known as sound. A propagating wave is always directed since it has a direction of propagation.
The ill-conceived term has occasionally been specified as "sidewards directed explosion pressure wave" in order to indicate that the verbal construct refers to a phenomenon whose destructive power affects only a strip on one side of the volcano. A volcano would never be able to emit a beam of sound which is both narrow and powerful enough to upset trees. What causes damage is of quite another kind, an avalanche-like phenomenon known as a pyroclastic flow. It can be imagined as a fast moving, hot heavy cloud of sputtered lava droplets. The strong turbulence prevents most of the droplets or grains from falling out and even enables
the flow to pick up matter from the ground. As soon as the flow has become too slow to sustain strong turbulence against the retarding action of friction, the droplets or ash particles simply settle down so what is left is hot air.
Calling a flow running down a slope a wave precludes understanding of what is going on. A wave in air propagates with the velocity of sound but a flow can have any velocity. Obviously, the initial direction of the flow is set by the slope. Once in motion, the heavy cloud keeps moving according to the acquired momentum which enables it to cover considerable distances and even run uphill on undulating terrain.
The flow is restricted laterally because an eruption is never quite symmetric with respect to the conic volcano, and often the volcano itself is not conic as a result of landslides on its slopes. It has been repeatedly claimed that a "sideward directed explosion pressure wave" had blown away one side of Mt. St. Helens but the succession of events had been the other way round: The swelling of the mountain foreboding the eruption caused a huge landslide which in turn caused the eruption and hence the pyroclastic flow to be "sidewards directed".
Needless to say that no "directed pressure wave" is required as an explanation of the upsetting of trees after an eruption. (See also Volcanism and Fossilisation.)

Symmetry of palaeozoic tree fern sporangia
Symmetry is a fundamental concept in physics but in biology it is not. A popular example is the clover leaf which normally is composed of 3 leaflets but occasionally of 4 or even more. Among flowers with 4 equal petals in regular arrangement so that there are 4 mirror planes and a 4-fold axis, the same species may occasionally produce a flower with 5-fold symmetry. 5-fold specimens of the herb Paris quadrifolius mingle with the 4-fold ones.
The spore capsules of the palaeozoic tree fern Scolecopteris elegans, for example, grow in clusters (synangia) of 3 to 6, very rarely 7, without caring much about symmetry. While the most abundant 4-fold 
synangia, like the flower with 4 petals, usually do not much deviate from the symmetry type of the square, the symmetry of the 5-fold ones is most often reduced to only one mirror plane or to no symmetry at all.
6-fold synangia with the symmetry of the 6 dots on a dice have been called "bilaterally symmetric". Bilateral symmetry means the presence of at least one mirror plane, and since mirror planes can be present in various arrays of any number of sporangia, even or odd, the term is unsuitable here. It irks the reader to come across a term which is right but trivial and is used as if it were not trivial.
Perhaps it is a desire for simplicity which tempts people to suspect symmetry principles being at work where they are not. 3- or 4-fold synangia are often arranged such that they show a 3- or 4-fold axis of rotation. This has been generalized into the idea that
"radial symmetry" is an inherent property of synangia. As a consequence, explanations had to be thought up why reality is different. It has been proposed that asymmetry is due to squeezing but closer inspection of the fossils shows that there is asymmtry also without squeezing, and that symmetry, if there is any, is more incidental.
As to the individual sporangia, they are said to be spindle-shaped, or fusiform, although they are obviously not. Their cross-section is not circular but has two plane sides making an angle of 120 or 90, depending on whether the synangium consists of 3 or 4 sporangia. Furthermore, they are not attached with their bottom but sideways. Nevertheless, the shape of the sporangia has repeatedly been likened to the cylindrical symmetry of a spindle.
One wonders why the notions of radial symmetry of the clusters called synangia and of fusiform sporangia have persisted in the palaeobotany literature up to now, despite of ample
contrary evidence. There is an explanation: In order to avoid potential trouble resulting from contradiction, it is advisable to repeat what is there in print, and if this is not compatible with reality, to interpret reality as a deviation from the rule: synangia being squeezed into asymmetry, and sporangia being not fusiform due to mutual contact.
Introducing symmetry and considering deviations in reality is an appropriate approach when talking about crystal shapes, for example. In the above case of species identification by means of shape and arrangement of plant organs it is an unnecessary and deflecting detour brought about by obeying the hearsay principle.

Wondrous adaptations or no mite coprolites
When in the 1990s palaeontologists noticed that the tiny dark clots often seen in damaged tissue of fossil plants are compatible with the size of oribatid mites, it seemed to be a good idea, with other explanations lacking, to promote the oribatid mite coprolite hypothesis although the mites themselves remained elusive. One could have hoped then that they would turn up sooner or later. The hypothesis became increasingly popular by way of hearsay while evidence was accumulating which should have given rise to doubt:
Clots were found within tiny closed spaces where no mite could have crept, and the mites never turned up. Clots of two sizes in one sample were interpreted as evidence for the presence of two species of mites.
By looking not only at the clots but at their vicinity one would have seen that often the clot sizes agree with the cell sizes. For any clot size one can likely find a damaged tissue nearby with fitting cell size. Even the shapes of the alleged coprolites can agree with the cell shapes of the "eaten" tissue. There are polygonal ones with one or two acute angles: strange coprolites indeed, wondrous conformity of faeces and food.
Despite of these facts, some paleobotanists
stubbornly adhere to the coprolite hypothesis, eventually substituting "unknown creatures" or "new detritivores" for oribatid mites, while others seem to be inclined not to mention the subject any more, hoping the oribatid mite coprolites will fall into oblivion.
With coprolites being ruled out, the clots have to be interpreted: The damaged tissue with clots resembles some type of extant wood rot.
For completeness it is mentioned here that there seem to be more than one type of clots misinterpreted as coprolites: Some are essentially globular inside the infected cell, others fill the cell cross-section, become angular,
and remain so when the cell wall breaks down, or they expand the cell so that finally they are bigger and rounded. What remains to be done is to find the organism responsible, and one can be sure it is no creature.

H.-J. Weiss     2013

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