ethan@utastro.UUCP (Ethan Vishniac) (04/22/85)
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Paul Dubois has recently posted a long series of articles, in which,
among other things, he declares that evolution is a vacuous theory which
is incapable of making testable predictions.
Some clarification may be in order. The following points are parts of
scientific theories that have been lumped under the name of "evolution" for
the purpose of most of the discussion in this group.
1) Current cosmology [ nothing in this really matters except the overall
age of the universe which is in excess of 10 billion years]
2) Astrophysics of stars and our galaxy. [Ditto for this one]
3) Age of the solar system. [About 4.56 billion years from nuclear dating
of meteorites. Stellar evolution gives a consistent but less precise
age for the sun, from 4 to 5 billion years.]
4) Geology and the history of the Earth. The crucial issue here is, again
age, although a number of phenomena are included here which require a
large age, and therefore play a subsidiary role in the argument.
5) The idea that all life shares a common ancestry. [This idea is
pre-Darwinian]
6) Darwinian evolution i.e. change through the operation of natural
selection on populations with varying characteristics.
Most of the creationists on the net take exception to the current state of
scientific theory in all 6 categories. A few creationists, perhaps including
some on the net, are willing to pass on 1-4 and take serious exception only
to 5 and 6.
Now Paul's recent diatribe on evolution repeatedly makes the claim the
natural selection is inadequate as a theory because it makes no testable
predictions, and then proposes to substitute "scientific creationism"
in its place, a hypothesis which stands in contradiction to points 1-5
above. Similary, in earlier postings he has noted that there is some
uncertainty about point number 6 among scientists and then blithely
equated that to the uncertainty in his mind about *how* God works his
magic.
I'm afraid it's not in me to be charitable on this. This is a ludicrous
stand. Without going into points 1-3 (although I could, being an expert on
1 and fairly knowledgeable on 2 and 3), it should be clear that numbers 4 and
5 do not stand or fall on the success of 6. The reverse is true.
How well do we know 4 and 5? I note that 4 and 5 are easily falsifiable
points. An earlier discussion in this group pointed out that the concept of
the geological column predates Darwin. This idea not only explains the
nature of geological strata but makes some specific predictions. The most
straightforward is that, given a means of determining the ages of rocks, the
lowest layer in the geological column will be the oldest and so on down to
the highest and youngest layer. The discovery of radioactivity and its
application to the ages of rocks has allowed us to verify this prediction.
Point 5, which seems to be what most people mean when they say evolution,
got started as an attempt to explain the ordering of fossils in the geological
column. It also involves specific predictions. The one that was clear
in Darwin's time was that the fossil record should not include glaring
anachronisms. This constraint has become much more restrictive as our
knowledge of lineages has improved. It is trivial to see that this involves
the possibility of falsifying evolution. Just find me a homo skeleton
fossilized in a Mesozoic stratum. An additional, and unforseen, test has
arisen with modern biochemistry. Several people have already noted that
biochemical similarities are strongly correlated with relationships deduced
from morphology and from the fossil record. (No, Mr. Samuelson, this is not
circular reasoning. The prediction preceded the test.) This having been
established one can turn this discovery on its head and use biochemistry
to predict kinships not already confirmed through fossils. This constitutes
a prediction of further fossil finds. As an example, morphology indicates
that the great apes are our nearest relatives. The fossil record for the
upper primates is affected by a severe gap between the present and about
8 million years ago (which corresponds to a reduction in the habitat of
the great apes). It has not been possible to assign fossils of >8 million
years of age to any living group of great apes (or humans) with any
confidence. Therefore the degree of relationship between homo and the
various kinds of apes was undetermined. Recent biochemical work has indicated
a set of relationships. (Paul caught me on this one earlier. I said it
was clear that chimpanzees are our closest relatives. Not so, it is
not quite certain whether gorillas, humans, and chimps are all equally
related or whether chimps and humans are significantly closer. On the
basis of very recent work I believe my original statement will prove to
be correct.) Rarity of fossils is not the same as their nonexistence. I
expect that as fossils showing the human lineage between 3.5 and 8 million
years ago are found they will confirm the biochemical evidence. If not,
this will cast doubt on the validity of the biochemical argument.
Point number 6 is the real work of Darwin. He showed that there is
a naturalistic explanation for the origin of species. His argument rested
on the idea that variations within a species are continually being created.
This was an idea for which no basis existed *at the time*. We have one
now. The idea that natural selection accounts for the rest of the process
of evolution is a seductive explanation, but is indeed difficult to falsify.
This has lead to continual speculation on other mechanisms as well as an
enlargement of what is meant by "natural selection" (e.g. sexual selection).
I think that it is reasonable to count the discovery of mutation as a
confirmation of a prediction of Darwin's theory. Further tests of the
efficacy of natural selection will be possible only as our knowledge of
the relationship between genetic structure and the details of organisms
increases. We do know that it is possible for humans to practice selection
to great effect. (Consider the development of corn from primitive grasses
or the differentiation of cabbage, cauliflower, kale and broccoli.)
Notice that none of this says anything about increasing "complexity" or
"degeneracy" of any particular lineage. The fact that the complexity
of the most complex organism increases with time does not imply anything
about the evolution of any particular lineage.
A large submission of Paul's had to do with many people believing in
evolution on inadequate grounds. I am quite confident that this is true and
regrettable. It is also irrelevant. I'm sure you've all heard the joke:
" They laughed at Galileo! They laughed at Einstein! They laughed
at Murray Katz!"
"Who's Murray Katz?"
"My uncle. He *really* was crazy."
One final note, Paul has dredged up again the old saw about creationism
being the only alternative to evolution. This has a certain appeal.
The only alternative to the natural is the supernatural. However, evolution
does not exhaust the possibilities of the natural, and "scientific" creationism
does not denote the class of all possible supernatural theories.
"Don't argue with a fool. Ethan Vishniac
Borrow his money." {charm,ut-sally,ut-ngp,noao}!utastro!ethan
Department of Astronomy
University of Texas