Encyclopedia of Evolution.pdf - Online Reading Center

e exactly the right ones. Bovine insulin, for example, differs
from human insulin by two amino acids (about a four
percent difference) yet for most diabetics bovine insulin
works as well as human insulin. Substitutability of different
proteins has been confirmed by genetic engineering, in
which the protein used by one species can substitute for the
corresponding (and structurally different) protein in another
species (e.g., human genes in transgenic mice). Another
example is found in the evolution of the eye. Crystallins are
transparent, light-refracting proteins found in the lens of
an eye. Animal species employ a wide variety of different
protein types as crystallins. In all cases, the proteins were
“co-opted” from different sources. In vertebrates, some
crystallins evolved from heat shock and other stress proteins,
while in insects, they evolved from proteins that are
part of the external skeleton (see table). ID theory makes
no allowance for the possible substitutability of different
components of a supposedly “irreducibly complex” system.
• Duplication and horizontal transfer of components of systems,
or of entire systems. New genes can arise from the
duplication and modification of old genes (see DNA [raw
material of evolution]). Behe mentions this, then ignores
it. Most ID theorists consider photosynthesis to be irreducibly
complex. Photosynthesis of cyanobacteria, green algae,
and plants has two phases. Some bacteria, however, have a
simpler version of photosynthesis that closely resembles one
of these systems (see photosynthesis, evolution of). It is
certainly possible that cyanobacteria (the ancestors of chloroplasts;
see symbiogenesis) obtained this subcomponent
by horizontal gene transfer from these other bacteria.
Behe admits that prokaryotic cells are simpler, and the role
of symbiogenesis in the origin of eukaryotic cells, but refuses
to admit this as an explanation for the supposed irreducible
complexity of the eukaryotic cell. When Behe describes
the complex cascade of reactions involved in the formation
of a blood clot, he refers to the proteins involved without
mentioning that these proteins are variant forms of serine
proteases, enzymes that have functions other than blood
clotting. The blood clotting genes arose as duplications of
serine protease genes, followed by mutations.
• A creator. Behe and other ID theorists insist that you need
not specify who or what created the irreducible complexity.
Therefore, ID theorists insist that it is not creationism.
As a result, ID theory posits a very large brick wall
with a sign on it, “No scientific inquiry past this point.”
This is, ultimately, what makes ID nonscientific (see scientific
method). Of what kind of Creator might Behe
be trying to persuade his readers? He refers to the cascade
of events in blood clotting to be a Rube Goldberg apparatus,
which makes it sound as if the irreducible complexities
of the biological world are the product of a silly God.
The Creator posited by ID also created parasites and
allowed extinctions. Behe includes suffering and death as
an aspect of the design of life, but he is no more successful
than anyone else at explaining why a good God would
have done this (see essay, “Can an Evolutionary Scientist
Be Religious?”).
Origins of Visual Crystallin Proteins
in Different Animals (from True and Carroll)
Crystallin Found in Derived from
intelligent design
α vertebrates small heat shock proteins
β vertebrates similar to bacterial stress
proteins
γ vertebrates other similar to bacterial stress
than birds proteins
ρ frogs NADPH-dependent
reductase
δ turtles, lizards, arginosuccinate lyase
crocodiles
τ turtles, lizards α enolase
π lizards glyceraldehyde phosphate
dehydrogenase
ε crocodiles, birds lactate dehydrogenase
μ kangaroos similar to bacterial
deornithine aminase
η humans aldehyde dehydrogenase
ζ guinea pigs, camels alcohol dehydrogenase
λ rabbits hydroxyacyl-CoA
deyhydrogenase
L squids aldehyde dehydrogenase
S octopuses glutathione S-transferase
Ω octopuses aldehyde dehydrogenase
O octopuses similar to yeast TSFI
droso-crystallin fruit flies insect cuticle protein
J1 jellyfishes similar to chaperonin heat
shock protein
Evolutionary scientists have been very vocal in attacking
ID theory in general and Behe’s book in particular. Among
the reasons are:
• Behe implies that the evidence usually cited in favor of evolution
does not matter (see above). It may very well be that
paleontological and comparative evidence does not alter his
particular argument. But by ignoring the evidence that evolution
has, in fact, occurred, Behe perpetuates the misconception,
prevalent in the general public, that such evidence
does not exist.
• Behe does use one other creationist argument that has
been repeatedly discredited. He suggests that, when evolutionary
scientists disagree, they must all be wrong. He
cites the controversy over symbiogenesis (see Margulis,
Lynn), and the controversy over punctuated equilibria
(see Eldredge, Niles) to prove that all sides of these
arguments must be wrong. He suggests, incorrectly, that
Margulis and Eldredge have rejected natural selection. He
compared the arguments of Margulis and the evolutionary
biologist Thomas Cavalier-Smith, and said, “Each has
pointed out the difficulties in each other’s model, and each
is correct.” His conclusion is that “the natives are restless,”
that is, evolutionary scientists are becoming dissatisfied