 In
neo-Darwinism, evolution is explained by the natural selection of small
mutational changes in the "genetic programs" that allegedly control
embryonic development.
But mutations that produce major changes
in development are invariably deleterious, and are thus weeded out by
natural selection; so neo-Darwinism assumes that evolution proceeds only
(or primarily) through minor changes.
DNA mutations that are beneficial (and
thus likely to be naturally selected in the appropriate environments) have
been observed, but only at the biochemical level; beneficial mutations in
developmental programs have not been observed. In the absence of evidence,
the neo-Darwinian view rests entirely on the assumption that genetic
programs MUST control development.
This assumption, however, is not
supported by the evidence.
To be sure, genes (DNA sequences) affect
development, but many lines of research suggest that body plans and other
morphological features are laid down prior to and largely independently of
gene expression. Genetic mutations affect development primarily by (a)
damaging molecules needed for normal development, and (b) damaging binary
switches that direct development along pre-determined lines that are not
controlled by the genes themselves.
The first effect is analogous to damaging
building materials during the construction of a house; if 2x4s that should
be eight feet long are actually shorter or
of varied lengths, the shape of the house will be affected.
The second effect is analogous to
damaging switches in a railroad switchyard; if cars carrying heating oil
destined for Iowa are sent down a siding meant for an Amtrak Metroliner,
they will end up in the wrong place.
Features of the fertilized egg that seem
to be more fundamental than the genes in controlling development include
patterns imprinted on the membrane by the mother, and cytoskeletal
patterns generated by centrosomes. In order for evolution to occur, these
features (and whatever other features may turn out to be involved) would
have to change in concert with the genes.
A neo-Darwinian
explanation based on simple changes in DNA sequences is fundamentally
incapable of accounting for evolutionarily significant changes in
development. Within a neo-Darwinian framework, the organism can't get
there from here.
*Presented by Jonathan
Wells at a Discontinuity seminar, Friday, August 17, 2001, Cedarville
University, Cedarville, Ohio. Dr. Wells is a
postdoctoral biologist and senior fellow at the Discovery Institute, and
hold Ph.D.s from both Yale University and the University of California at
Berkeley. His recent book, Icons of Evolution,
published by Regnery, has attracted international endorsement. |
