Re: 'Directed' evolution?

Keith B Miller (
Tue, 22 Sep 1998 22:00:50 -0600

Howard wrote:

>It may be the case that Denton's _Evolution: A Theory in Crisis_ was either
>misunderstood or misrepresented by many. Correct me if I am wrong on this,
>but I believe his criticisms there (whether valid or not is another
>question) were mostly about undirected Darwinian gradualism. He had no
>objections to the concept of evolutionary continuity, just to certain types
>of attempts to give a scientific account of it.

If you read his chapter on the fossil record (Chapter 8), for example,
there is simply no way to read it other than as an argument _against_
common descent and genetic continuity. He goes out of his way to dismiss
all transitional forms. He eliminated them by appealing to typology, by
excluding character mosaics, by appealing to convergence (p. 181), and
finally by demanding what the fossil record cannot provide. After
describing clear intermediate forms from the fossil record he states (p.
176-177), ".. the point at issue here is that skeletal characteristics
alone are insufficient for designating a particular organism or species as
intermediate." And " is not sufficient to find in the fossil record
one or two types of organisms of doubtful affinity which might be placed on
skeletal grounds in a relatively intermediate position between other
groups." Since the only evidence available from the fossil record is
skeletal, except in rare circumstances, no fossil can be designated an
intermediate form by his definition regardless of its intermediate skeletal

His argument for a typological view of nature (chapter 5) is also founded
on the idea that taxonomic groups are distinct entities unrelated by common
descent. Denton states: "According to the typological model of nature all
the variation exhibited by the individual members of a particular class was
merely variation on an underlying theme or design which was fundamentally
invariant and immutable" (p. 94). And: "Becasue no member of any defined
class could stray beyond the confines of its type in terms of its basic
characteristics, then no class could be led up to gradually or linked to
another class through a sequence of intermediates....Typology implied that
intermediates were impossible, that there were complete discontinuities
between each type" (p. 96). He then spends a whole chapter arguing that
this view of nature is correct!

His genetic argements are also an attempt to support a typological
(non-evolutionary) view.

He makes numerous statements that clearly show organic continuity and
common descent to be the object of his critque.

For example:"It is clear that there are formidable problems in interpreting
evidence for continuity on the basis of skeletal remains. Consequently if
the fossil recxord is to provide any grounds for believing that the great
divisions of nature are not the unbridgeable discontinuities postulated by
Cuvier [typological model], it is not sufficient that two groups merely
approach one another closely in terms of their skeletal morphology. The
very least required would be an unambiguous continuum of transitional
species exhibiting a perfect gradation of skeletal form leading unarguably
from one type to another." He then spends a whole chapter defeating this
paper tiger, thus demonstrating the validity of Cuvier's view.

It can't be argued that Denton is only attacking hypergradualism. He also
specifically dismisses any form of saltation. He states: "Such major
discontinuities simply could not, unless we are to believe in miracles,
have been crossed in geologically short periods of time through one or two
transitional species occupying restricted geographic areas. Surely, such
transitions must have involved long lineages including many collateral
lines of hundreds or probably thousands of transitional species. To
suggest that the hundreds, thousands or possibly even millions of
transitional species which must have existed in the interval between vastly
dissimilar types were all unsuccessful species occupying isolated areas and
having very small popluation numbers is verging on the incredible!"
(P.193-4). He also previously argued that an appeal to an imperfect fossil
record was not acceptable. In other words, to bridge very dissimilar
species would have required a multitude of transitional forms. These are
not found, therefore the species are not related by common descent.

In conclusion, after mentioning fossils that appear "to some extent
intermediate," he states: "As evidence for the existence of natural links
between the great divisions of nature, they are only convincing to someone
already convinced of the reality of organic evolution"( P. 195).

How can any of this not be understood as an argument against common descent
and organic evolution in the broadest sense?


Keith B. Miller
Department of Geology
Kansas State University
Manhattan, KS 66506