On Tue, 01 Oct 1996 17:38:38 -0400 (EDT), lhaarsma@OPAL.TUFTS.EDU
wrote:
LH>One of the more popular versions of Progressive Creation and ID
>theory is what I would call, "'Supernatural genetic engineering' at
>strategic historical points to introduce biological novelty and
>complexity." (Novelty and complexity which, the argument goes,
>could not have arisen from natural mechanisms.) There is a good
>reason its popularity. It elegantly incorporates the fossil data
>and the genetic and developmental data supporting common ancestry.
>(It's my favorite alternative to evolutionary creationism.) Even
>so, it has a few less-elegant points which are worth probing.
As the old song goes, "You only build me up to let me down!" :-)
LH>A few months ago, Nicholas Matzke and Steve Jones were discussing
>lizards and birds. I broke into the discussion, and Steve responded
>to me thus:
>
>I've got a question for you, Steve. In your discussion with
>Nicholas Matzke regarding birds, dinos, and lizards, you seemed to
>come to agreement on at least this point: There are a number of
>late dino species with a few "bird" characteristics, and there are a
>number of early birds with many "dino" chacteristics; however, these
>(known) species do NOT clearly form an ancestral sequence. Is that
>accurate?
>SJ>You are right re "a number of late dino species with a few `bird'
>characteristics" but not about "a number of early birds with many
>`dino'. AFAIK we only discussed *one* bird species Archaeopteryx. I
>am not sure if other early birds have "dino" features, or if they do,
>whether we disussed them. But I do concede that Archaeopteryx has
>some "many `dino' chacteristics".
>LH>I'm guessing that you would argue that some of the changes
>necessary to go from dinos to birds (feathers, beaks, hips,
>breastbones, etc.) are non-trivial (mutationally), and would
>require "supernatural intervention at strategic points." Is that
>accurate?
>SJ>No. I would need to consider each feature on its merits. It may be
>that "beaks" are easy to develop by an extension of the palette and I
>note that octopi, dinosaurs, platypi, and of course birds all
>developed beaks. I am interested in the *first appearance* of a
>feature, as this represents the first expression of a new
>"sub-routine" in the genetic code. So if "feathers" first appeared
>in Archaeopteryx, then that is where I would assume (not "require")
>"supernatural intervention" at strategic points." If it is later
>found that an earlier reptile had a feather, then I would assume that
>is where the potential "supernatural intervention" occurred in a
>recoding of the genetic code:
>LH>Now here's the question: Suppose several late dino and several
>early bird species have a certain "bird" characteristic (e.g.
>beaks), but these species do not form an ancestral chain, would this
>require God to perform the same supernatural intervention at several
>different strategic points?
>SJ>...I would assume that only *one* "supernatural intervention"
>would be needed at *one* "strategic point" for the first appearance
>each new feature. One recoded, the code could remain dormant in the
>genome until needed again. BTW, I assume that birds and *reptiles*
>do "form an ancestral chain". I do not necessarily assume that
>birds and *dinosdaurs* "form an ancestral chain". I certainly do
>not believe that late dinosouars like Ornithomimus which developed a
>beak throws any light on the origin of birds.
LH>An excellent answer from Steve. Now let's carry it further.
>
>What about bats' wings? Their common ancestor with other winged
>creatures goes back *long* before bats' wings first appeared.
"bats' wings" are an entirely different principle from bird's wings.
They may be similar to winged reptiles (the pterosaurs). If they are,
I would assume a common genetic code.
LH>What about the squid eye and the vertebrate eye? Both are
>complex, but their common ancestor goes back a very long ways ---
>unless I'm mistaken, well before the appearance of any complex eyes.
>In fact, I believe that the fossil record suggests that complex eyes
>arose "independently" considerably more than just twice.
Actually, it is now believed that *all* eyes, invertebrate and
vertebrate, are derived from the *one* gene-complex, a stunning
confirmation of my theory and a non-prediction/expectation of
Neo-Darwinian "blind watchmaker" evolution:
===========================================================
DNA evidence of ancestral age
Andrew Luck-Baker
BECAUSE their construction is so different scientists have always
assumed that the multifaceted compound eye of flies and the single
lens eye of vertebrates evolved independently. However, this belief
has now been challenged Rebecca Quiring and Uwe Walldorf at the
University of Basel have found tantalising evidence that both types of
eye evolved from a common organ. Over hundreds of millions of
years, flies and vertebrates have retained the same genetic master
switch for eye development.
The gene in question is called Par-6; one of a family that ensures that
parts of the body emerge at the right time and place in growing
embryos. Developmental geneticists have known for a long time that
Pax-6 has a vital role in setting up vertebrate eyes. Human and mouse
embryos With defective versions never form eyes or else have small
eyes lacking irises.
Quiring and Walldorf identified a gene in the fruit fly drosophila
which is homologous or virtually identical to the Pax-6 genes of
humans, mice, quails and zebra fish. Bases are the molecular letters
that spell out the genetic code. Also, after consulting records of fruit
fly gene defects, the researchers found that the position of their gene
in the drosophila geno]ne matches that of a mutation called eyeless,
which makes fruit flies develop without eyes.
In vertebrates, Pox-6 codes for a protein, called a transcription factor,
which switches on other eye genes. It triggers a cascade effect
through a series of genes which, step by step, make cells differentiate
and build the emerging eye. In the fly Pax-6 has the same role and
triggers the same genetic developmental path, even though the end
result is very different. However, Walldorf says that the case is not
yet watertight. He plans to find out if adding normal mammal Pax-6
genes to fly embryos with defective eyeless genes will mean two
normal eyes in the adult flies.
The researchers have yet to pinpoint exactly when Pax-6 starts its
work, though they know that it is active in the very early stages of
eye formation. According to Charles Zuker of the University of
California, San Diego, the gene establishes two undifferentiated eye
sites in vertebrates. "It targets areas of the embryo telling them, 'your
job is to become part of the mature eye"' he says. "It activates sets of
genes which are the doers of the final job."
In the embryonic fly eye, the Basel team discovered that Pax-6 is at
work ahead of and just inside the so-called morphogenetic furrow.
This is a wave front of cell specialisation that sweeps across the
developing eye from the back to the front.
According to Zuker other research indicates that fruit flies and
vertebrates share another genetic switch called sine oculis which is
further along the pathway of eye development. It comes into play in
both eye designs as cells begin to specialise. The Pax 6 and sine oculis
discoveries hint that, like architects, flies and vertebrates use the same
foundations and girders for a framework but opt for different sized
rooms, numbers of windows and styles of furniture. "We are nothing
but big flies," he says .
The search is now on to find homologous Pax-6 genes and discover
their roles in other animals. Walter Gehring, who heads the Basel
group, has tracked it down in the common squid. Squid, and their
octopus and cuttlefish cousins, have eyes with a retinal backcloth, a
single lens and an iris very much like vertebrates. The close similarity
has always been pointed to as a classic example of convergent
evolution. Pax-6 hints at more than coincidence.
The Swiss group has also found DNA sequences similar to Pax-6 in
flatworms, which are among the most primitive of animals to have
eyes. Flatworms are blessed with just two featureless patches of
photosensitive cells, called eyespots. If Pax-6 tums out to be crucial
in forming these simple organs that distinguish between light and
shade, Walldorf and his colleagues say that scientists must rethink the
dogma that eyes of invertebrates and vertebrates evolved completely
independently.
(Luck-Baker A., "DNA Evidence of Ancestral Age", New Scientist,
10 September 1994, p15)
===========================================================
Berlinski comments:
"I am in agreement with Mr. Gross when he refers to "new and
astonishing evidence" about the origin of the eye. Herewith the
facts. Halder, Callaerts, and Gehring's research group in
Switzerland discovered that the ey gene in Drosophila is virtually
identical to the genes controlling the development of the eye in mice
and men. The doctrine of convergent evolution, long a Darwinian
staple, may now be observed receding into the darkness. The same
group's more recent paper, "Induction of Ectopic Eyes by Targeted
Expression of the Eyeless Gene in Drosophila" (Science 167, 1988) is
among the most remarkable in the history of biology, demonstrating as
it does that the ey gene is related closely to the equivalent eye
gene in Sea squirts (Ascidians), Cephalopods, and Nemerteans. This
strongly suggests (the inference is almost irresistible) that ey
function is universal (universal!) among multicellular organisms,
the basic design of the eye having been their common property for
over a half-billion years. The ey gene clearly is a master control
mechanism, one capable of giving general instructions to very
different organisms. No one in possession of these facts can imagine
that they support the Darwinian theory. How could the mechanism of
random variation and natural selection have produced an instrument
capable of anticipating the course of morphological development and
controlling its expression in widely different organisms?"
(Berlinski D., "Denying Darwin: David Berlinski and Critics",
Commentary, September 1996, p28)
LH>Suppose we have a complex biological feature which we believe
>probably required supernatural intervention. Now suppose this
>feature is found in multiple groups whose common ancesters go back
>well before the first appearance of that feature? Should we
>hypothesize multiple instances of supernatural intervention to
>achieve similar features? Does this seem less "elegant" than a
>single intervention? Should we hypothesize a single intervention
>with a very long dormancy? Or would this pattern suggest to you
>that, perhaps, that *particular* feature probably arose through
>natural mechanisms? If so, why?
I would assume "a single intervention with a very long dormancy". It
may even be that all the entire gene complexes in the animal kingdon
were built-in right from the Cambrian Explosion, but only activated
or unmasked later when needed. In fact, that would be my (but not
necessarily God's) preferred most "elegant" method.
God bless.
Steve
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