The hearsay principle in science
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