You're right, he doesn't, but Denton clearly implies just this in his
chapter "A Biochemical Echo of Typology" (Denton, 1986, pp. 274-307). His
argument goes like this:
"the new molecular approach to biological relationships could potentially have
provided very strong, if not irrefutable, evidence supporting evolutionary
claims. Armed with this new technique [sequencing proteins of various species and
comparing the differences], ALL THAT WAS NECESSARY TO DEMONSTRATE AN
EVOLUTIONARY RELATIONSHIP WAS TO EXAMINE THE PROTEINS IN THE SPECIES CONCERNED
AND SHOW THAT THE SEQUENCES COULD BE ARRANGED INTO AN EVOLUTIONARY SERIES"
(277)
He then provides examples of letter chains that are intermediate between other
chains. An intermediate in the middle chain makes it transitional between the
1st and 3rd chains, and suggests evolution. His point is that traditional
evolutionary sequences (from big: "cyclostome --> fish --> amphibian --> reptile -->
mammal" (284) to "relatively trivial" (287) - eg, monkey --> apes --> man)
SHOULD be deducible from protein sequences IF evolutionary theory is correct.
Thus, amphibians would have a sequence intermediate between that of fish and
reptile (or, monotremes should be intermediate between reptiles and placentals
- my example, not Denton's, but it uses identical logic).
This is the straw man that Denton sets up: the problem is that the proteins
sequenced were all of living organisms NOT ancestral to each other, but
descended from the SAME ANCESTORS. Thus frogs are not a rung on a ladder
between fish and mammals; rather, fish, frogs, and mammals are all twigs on a
tree, with frogs and mammals sharing a branch. Denton acts all surprised when
he does not find sequence, but sequence (between present-day organisms) is not
what evolution predicts. It predicts sequence between ancestors (which,
unfortunately, cannot easily have their DNA sequenced).
The same argument of direct evidence of intermediates (either with protein
sequences, or fossils, or physical study of living organisms) being the ONLY
valid evidence for evolution is the trap that Stephen falls into. There are
other forms of evidence. MY point is that if we can find either modern-day or
fossil creatures that exhibit some characteristics of one lineage and some of
another, the best explanation is that they are descendants (or offshoots close
to the split) of that ancestor that is intermediate between the lineages. For
some reason (in the case of monotremes, geograpic isolation and lack of
competition) they retain some of the traits that were lost in the now-common group
(placentals).
As to Stephen's (and Denton's, p. 109 and thereabouts) point that, with
monotremes, the individual characteristics are either reptilian or mammailian,
I do not think that is a problem: why should all mammalian charactistics evolve
at once? Besides, the statement is not quite true: playpi do not have mammary
glands in the same sense as placentals: the babies "lap milk from their
mother's abdomen" rather than sucking on nipples, my trusty World Book
Encyclopedia says. Also, monotremes are not fully warm blooded - their body
temperatures vary somewhat with the outside temperature (but not to the degree
that reptile temperatures do) - if this is not a case of an intermediate trait,
I don't know what is. I admit that platypi lay their eggs in a fully reptilian
manner - but echidnas (World Book again): "lay one egg a year. The egg has a
tough, leathery shell and hatches in a pouch that forms on the female's belly
each mating season. The young echidna remains in the pouch for several weeks
and feeds on the mother's milk."
sequence from reptile to mammal - but it does show that the existence of fully
functional, natural intermediates is possible, and it suggests to us reasonable
paths of evolution from one lineage to another that do not require supernatural
explanation.
On the same ground, I can say that a bird-like dino with a beak is at least
suggestive of kinship between birds and dinos. Other evidence was asked for,
and here is what I know: Cretaceous waterbird fossils have been found that have
a whole head of teeth. Some dinos (T-rex was the example I heard) have large
breastplates (necessary, in birds, for the attachment of wing muscles). Some
ratites (ostriches, emus, and other ground birds) have vestigial claws on their
wings. The fast moving, bipedal dinos were probably warm-blooded. Baby birds
have a tooth they use to break out of their eggshell.
All of this together with Archyoptryx still not proof, by any means,
and is certainly not showing "how a bird could evolve from a dino by 100%
naturalistic proccesses" - an unattainable goal for ANY natural process, if
you take it to mean knowing the changes in genetic code for each member of each
ancestral population, the reason for the spread of the change, etc. We can
make pretty good guesses on some issues - the evolution of flight or the
modification of a lung are certainly not on the same level of difficulty as the
evolution of an eye, and THAT can be reasonably explained by naturalistic
processes (although deciding the exact path for each eye in each lineage is
probably beyond our powers). If someone can propose a better theory for the
evolution/creation of birds that better explains the evidence, I'm open to hear
it. This tentative hypothesis seems to be the best we've got, though.
The overall key to resolving this seems to be resolving where Stephen
draws the line at what he thinks is possible for natural evolution to
accomplish, and what he thinks requires direct supernatural input.
Certainly, some degrees of change are bigger than others, and some
transitions have far better evidence than others. Reptile-->mammal and
reptile-->bird seem roughly equivalent, although the evidence for mammal
evolution is much more comlete. If Stephen would allow (I don't know that he
does) that mammal evolution can be fairly well explained by natural means,
shouldn't he also admit that the evolution of birds is equally possible, even
if the evidence is not yet in? If he sets the level of supernatural
intervention
at that above the Biblical "kind", then we need to define what approximate
taxanomic level "kind" is. As my last post showed (I hope), if kind=order,
then humans could have evolved naturally, and it would be up to him to show
evidence that they did not that contradicts the evidence that they did.
(Actually, this gets worse if you consider that,
using protein sequences, chimps appear to be more closely related to us than to
gorillas and other apes. Thus, since chimps and gorillas are in the same
family, we should logically either be in their family, or chimps should be in
ours.) If kind=family (as I understand many creationists of all types
accept) then there is evidence of interbreeding (rarely, as reported on the
server) between kinds without detectable supernatural intervention making it
possible (maybe we should look harder; presumably, if God occaisionally
intervenes to make new kinds, we should eventually be able to document a case).
Since I finally (and belatedly; sorry :-( ) replied to Stephen's post, perhaps
he'd like to take a jab at my last one :-).
Sincerely,
Nick