I do not think that the definitions of evolution or of science
being used here have all been made explicit, making
communication a bit difficult.
In general, biological systems are too complex for precise
prediction, although probabilistic models can be given in
many cases. This is also true of much of physics. Even a
relatively straightforward system such as gravitational
attraction between bodies becomes intractible if there are
enough objects and enough time involved. Fluid dynamics
become problematic with a much more restricted
reference. It is simpler to predict the rate of establishment
of mutations in a population than to predict details of
eddies and currents in fluid flow. As noted in my previous
post, it is also straightforward, though potentially
time-consuming, to experimentally test the evolution of
organisms in controlled settings. A range of predictions
can be made and tested.
Charting the course of evolution of organisms over
geologic time, on the other hand, obviously requires
historical evidence. This is subject to predictions that can
be tested using the available evidence. For example, there
is general agreement between the results of study of the
fossil record and molecular comparisons. Another
prediction that can be made and tested is that older rocks
should generally have fewer modern forms and fewer
complex organisms. The presence of transitional forms is
another prediction of evolutionary theory confirmed by study
of the fossil record. Functional constraints provide another
evolutionary prediction that can be made. Stronger legs
and feet are of great advantage for rapid terrestrial
locomotion, and we can predict that organisms adapting to
life in open areas will show locomotion-related evolutionary
changes. We do not always have a way to predict whether
a given lineage will specialize for leaping, bipedal running,
or quadrupedal running. However, there are some strong
phylogenetic trends, suggesting that structural and
selective pressures play an important role. For hominids,
the use of hands for grasping probably ruled out
quadrupedal locomotion, and similar selective constraints
would influence other lineages. Bipedal locomotion was
the principle way of achieving more rapid locomotion in
archosaurs; perhaps they are structurally well-suited for
this approach. A good example of a prediction based on
evolutionary theories and tested against the fossil record is
Vermeij's idea of escalation and extinction. Predators and
prey, or herbivores and plants, are in an evolutionary arms
race. Over time, or in places with higher pressure, more
defenses will evolve in the prey and new ways of
circumventing them in the predator. This can be seen (or
felt, as Vermeij is blind and came to the idea by his
examination of shells from different regions) by
comparison of modern habitats. Algae from the
Indo-Pacific have levels of toxins high enough to deter most
temperate grazers, yet are gobbled up by the tropical
species used to such defenses. Extinction, however, may
throw a wrench into the process. If you put lots of energy
into building impenetrable defenses, you may not have
enough energy left over to deal with environmental
catastrophes. Thus, Vermeij predicted that the fossil
record would have a cyclic pattern of increasing buildup of
protective features, with crashes at times of major
extinction. Examination of fossil faunas has provided
mixed assessment of the idea so far.
It should be emphasized, especially by Christians, that
historical evidence is valid. It is not subject to experimental
replication in some ways, but at least some aspects of the
events can be replicated.
Dr. David Campbell
Old Seashells
46860 Hilton Dr #1113
Lexington Park MD 20653 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand
Exalted Periwinkle of the Mystic Order of Whelks-P.G.
Wodehouse, Romance at Droigate Spa
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