Elsberry reviews Johnson
Quite thorough and to the point but I would like to focus on this section
The fossil record and natural selection
When dealing with the fossil record, Johnson takes as disconfirming data the
current observed ratio of transitional sequences to non-transitional,
based upon the assertion that under Darwin's views we should expect many
more.
Darwin's theory predicted not merely that fossil transitionals would be
found; it implied that a truly complete fossil record would be
mostly transitionals, and that what we think of as fixed species would
be revealed as mere arbitrary viewpoints in a process of
continual change. (p.48, 2nd ed.)
Johnson's assertion is false. We can tell that it is false because we can
read Darwin's own words and find that Johnson's summary fails to represent
what Darwin said. Johnson never went to the trouble of attempting to derive
an expected ratio of transitional fossils to non-transitional fossils from
what Darwin actually said. Let me demonstrate by example the derivation of an
expectation of the ratio of transitional fossils to non-transitional
fossils from what Darwin wrote. Darwin stated that natural selection would
work intermittently, and often only at long intervals.
On the other hand, I do believe that natural selection will always act
very slowly, often only at long intervals of time, and generally on
only a very few of the inhabitants of the same region at the same time.
(CR Darwin, Origin of Species, 1st ed., p.153)
Darwin addressed geographical distribution of fossils as a factor.
One other consideration is worth notice: with animals and plants that
can propagate rapidly and are not highly locomotive, there is
reason to suspect, as we have formerly seen, that their varieties are
generally at first local; and that such local varieties do not spread
widely and supplant their parent-forms until they have been modified and
perfected in some considerable degree. According to this
view, the chance of discovering in a formation in any one country all
the early stages of transition between any two forms, is small, for
the successive changes are supposed to have been local or confined to
some one spot. Most marine animals have a wide range; and
we have seen that with plants it is those which have the widest range,
that oftenest present varieties; so that with shells and other marine
animals, it is probably those which have had the widest range, far
exceeding the limits of the known geological formations of Europe,
which have oftenest given rise, first to local varieties and ultimately
to new species; and this again would greatly lessen the chance of
our being able to trace the stages of transition in any one geological
formation. (CR Darwin, Origin of Species, 1st ed., p.306)
In his famous section on the imperfection of the geological record, Darwin
gave several further reasons to doubt that we would ever have a
complete record of past life.
I have attempted to show that the geological record is extremely
imperfect; that only a small portion of the globe has been geologically
explored with care; that only certain classes of organic beings have
been largely preserved in a fossil state; that the number both of
specimens and of species, preserved in our museums, is absolutely as
nothing compared with the incalculable number of generations
which must have passed away even during a single formation; that, owing
to subsidence being necessary for the accumulation of
fossiliferous deposits thick enough to resist future degradation,
enormous intervals of time have elapsed between the successive
formations; that there has probably been more extinction during the
periods of subsidence, and more variation during the periods of
elevation, and during the latter the record will have been least
perfectly kept; that each single formation has not been continuously
deposited; that the duration of each formation is, perhaps, short
compared with the average duration of specific forms; that migration
has played an important part in the first appearance of new forms in any
one area and formation; that widely ranging species are those
which have varied most, and have oftenest given rise to new species; and
that varieties have at first often been local. All these causes
taken conjointly, must have tended to make the geological record
extremely imperfect, and will to a large extent explain why we do not
find interminable varieties, connecting together all the extinct and
existing forms of life by the finest graduated steps. (CR Darwin,
Origin of Species, 1st ed., pp.340-341)
Given these views of Darwin, we can derive an expectation of the ratio of
transitional to non-transitional fossils found. I include in the following
only
those factors which yield a differential expectation of discovery of
transitional fossils displaying the action of natural selection.
EFR = (NSTP * NSPP * AP * SEVR * FSDP)
and
ETF = EFR * OFS
where EFR is the "expected fossil ratio",
NSTP is the "natural selection time proportion",
NSPP is the "natural selection population proportion",
AP is the "area proportion",
SEVR is the "subsidence vs. elevation variation ratio",
FSDP is the "formation to species duration proportion",
ETF is the "expected number of transitional fossils",
and OFS is the number of "observed fossil species".
Now, we can assign some estimated numbers to the variables listed above.
Because Darwin said "often only at long intervals", NSTP should be
small. Let's assign a relatively large "small" value of 0.1. Since Darwin
said that natural selection operates on only a very few inhabitants at a time,
NSPP should be smaller still than NSTP. Let's assign a value of 0.01. For AP,
the area proportion between the geographic extent of a widely
ranging species and its local variety, a value of 0.1 is probably an
overestimate, but let's leave it at that for the moment. For SEVR, Darwin's
text
would indicate a value of 0.25 or less would be reasonable. FSDP is something
best estimated by a geologist, but Darwin probably felt it to be
under 0.5. Replacing values, we find that
EFR = 0.1 * 0.01 * 0.1 * 0.25 * 0.5
EFR = 0.0000125 = 1/80,000
David Raup has estimated the number of catalogued fossil species at 250,000.
This allows us to generate an estimate for number of transitional
sequences expected under Darwin's own views as:
ETF = EFR * OFS = 0.0000125 * 250,000 = 3.125
Roger Cuffey's 1974 paper on paleontologic evidence listed references for at
least 139 fine-grained species to species transitional sequences.
According to an expectation derived from Darwin's own words and values from
the real world, it can be seen that the fossils have been rather more
forthcoming that one would expect, not less. Johnson's assertion of the
opposite is not credible and flies in the face of both Darwin's views and
real-world data.
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Does this lay to rest the often heard assertion from creationists about
transitional fossils? I doubt it, but it surely undermines their argument
even further,
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