On Wed, 28 Aug 1996 21:09:09, Glenn Morton wrote:
[continued]
GM>You write:
SJ>Note: I do not rule out that tetrapods may have descended from an
>unknown fish common ancestor. But I do dispute that it is quite as
>"smooth" as some evolutionists like to portray it.
GM>You sure put on a good appearance of ruling out any form of
>evolution.
It depends on what you mean by "evolution"! :-) I do not rule out
micro-"evolution", nor do I rule out common ancestry. But common
ancestry alone is not "evolution", as Wilcox points out:
"Evidence for structural difference/descent does not constitute
evidence for the mechanism by which structural transformation took
place. Therefore, the sorts of evidence that simply indicate
relationship and/or descent from a common ancestor (e.g., molecular
clock data, fossil sequences, chromosomal banding, and other measures
of similarity) are not relevant to this question unless they indicate
the nature of the creative mechanism that produced novelty during
that descent. Evidence of ancestry does not imply knowledge of the
morphogenetic mechanisms that are able to produce novelty. This was
perhaps better understood in the nineteenth century than it is today
(Muller and Wagner, 1991). Indeed, by 1850, almost all researchers
accepted common descent (Gillespie, 1979; Desmond, 1989). The unique
implication of Darwin's theory was therefore not descent, but its
suggestion that the source of biotic order was to be found in the
natural (material) order." (Wilcox D.L. "A Blindfolded Watchmaker:
The Arrival of the Fittest", in Buell J. & Hearn V., eds.,
"Darwinism: Science or Philosophy?", Foundation for Thought and
Ethics: Richardson TX, 1994, p195)
What I do not accept (because to date I have seen no good evidence of
it) is that there is a plausible, fully naturalistic, step-by-step,
Darwinian random mutation + cumulative natural selection
*mechanism*, that can turn a fish into a reptile, or a reptile
into a bird.
GM>Here is the data references are provided so that one can look it
>up for themselves:
>
>378 MYR ago- Pandericthys--These are lobe-finned fish. Their brain case is so
>much like that of the earliest tetrapod, they were originally classified as
>tetrapods until a complete skeleton was found. Then is was proven that they
>were really still fish. (Ahlbert and Milner, 1994, p. 508). This fish also
>had lungs and nostrils (Schultz and Trueb, 1991, p.87) These things really
>looked like tetrapods until you see the fins. The teeth had infolding enamel
>which is identical to that of the earliest tetrapods. Unlike all fish but like
>the tetrapods, the Panderichthys have lost the dorsal and anal fins, leaving 4
>fins in the place where legs would be in the Tetrapods.(Ahlberg and Milner, p.
>508. This contradicts Gish's claim that there is no fossil which shows loss of
>fins. (Gish, 1978, p. 78-79).
Glenn should bring his references to Gish up to date. He refers to
"Gish, Evolution: the Fossils say No. 1978" but Gish in 1985 wrote
an update of that book called "Evolution: the Challenge of the
Fossil Record". In it Gish says:
"According to the assumed evolutionary sequence of life, fish gave
rise to amphibia...The fossil record has been diligently searched for
a transitional series linking fish to amphibian, but as yet no such
series has been found. The closest link that has been proposed is
that allegedly existing between rhipidistian crossopterygian fish and
amphibians of the genus, Ichthyostega. There is a tremendous gap,
however, between the crossopterygians and the ichthyostegids, a gap
that would have spanned many millions of years and during which
innumerable transitional forms should reveal a slow gradual change of
the pectoral and pelvic fins of the crossopterygian fish into the
feet and legs of the amphibian, along with loss of other fins, and
the accomplishment of other transformations required for adaptation
to a terrestrial habitat. What are the facts? Not a single
transitional form has ever been found showing an intermediate stage
between the fin of the crossopterygian and the foot of the
ichthyostegid. The limb and the limb girdle of Ichthyostega were
already of the basic amphibian type, showing no vestige of a fin
ancestry. There is a basic difference in anatomy between all fishes
and all amphibians not bridged by transitional forms. In all
fishes, living or fossil, the pelvic bones are small and loosely
embedded in muscle. There is no connection between the pelvic bones
and the vertebral column. None is needed. The pelvic bones do not
and could not support the weight of the body. There are no walking
fishes, including the "walking catfish" of Florida. These latter
fish do not walk, but slither along on their belly, using the same
type of motion they use in the water. In tetrapod amphibians, living
or fossil, on the other hand, the pelvic bones are very large and
firmly attached to the vertebral column. This is the type of anatomy
an animal must have to walk. It is the type of anatomy found in all
living or fossil tetrapod amphibians but which is absent in all
living or fossil fishes. There are no transitional forms." (Gish
D.T., "Evolution: the Challenge of the Fossil Record", Master
Book Publishers: El Cajon CA, 1985, pp72-73).
At the time Gish wrote this in 1985, it was presumably correct
regarding " along with loss of other fins"? Glenn's references to
"(Ahlbert and Milner, 1994, p. 508)" and "(Schultz and Trueb, 1991,
p.87)" postdate Gish's latest book on this topic. Gish's remaining
points appear to be still valid.
But I am not a YEC like Gish and will concede that this is good
evidence for an "unknown fish common ancestor" between the
lobe-finned fishes and the tetrapods. This is common ground between
us, even though there still may be major problems in time-frames if
the earliest lobe-finned fish are contemporaneous with the earliest
tetrapods. In "this argument" we had "here a year ago", Ashby Camp
posted:
--------------------------------------------------------
As Ahlberg and Milner point out (p. 507), the oldest panderichthyids
currently known date from the Lower Frasnian (Upper Devonian - about
375 mya). There is solid evidence, however, for the existence of
tetrapods back to the Lower Devonian, some 25 million years earlier
(Anne Warren, Robert Jupp and Barrie Bolton, "Earliest tetrapod
trackway," _Alcheringa_ 10: 183-86 [1986]). This rather
inconvenient piece of data was omitted from the Ahlberg and Milner
review. If tetrapods existed millions of years before
panderichthyids, then tetrapods either evolved in more than one line
or panderichthyids had nothing to do with their evolution.
--------------------------------------------------------
If indeed tetrapod tracks exist from "the Lower Devonian, some 25
million years earlier" than "the oldest panderichthyids...from the
Lower Frasnian (Upper Devonian...), then there is still a chronology
problem. In that case, Pitman's point is still valid:
"Although newt-like Ichthyostega has 'fin-bones' in its tail, it is
very different from a coelacanth, lungfish or Eusthenopteron. It has
a true neck, limbs, fingers, toes and a greatly modified skull.
Since the earliest tetrapods are found in upper Devonian rocks,
contemporary with the fish from which they are supposed to have
descended, some unseen line is supposed to have evolved from
lobe-fins." (Pitman M., "Adam and Evolution", Rider & Co: London,
1984, p199)
Of course this may all eventually be cleared up and a good series of
links between the lobe-finned fish and the earliest tetrapods,
showing a gradual and progressive transformation of fins into feet,
complete with pelvic girdle, in the right time-frame (it may be
nearer than you think - a few days ago I saw a brief TV news clip of
a major Devonian fossilised fish find at Eden in SE New South Wales
with whole fish fossilised), but even then it would not prove
"evolution". What I want to see is a plausible fully naturalistic
"blind watchmaker" *MECHANISM* that can transform a fish into a
tetrapod, with no supernatural intervention needed. The traditional
Darwinian "just-so story" was that a fish gradually developed lung
from a swimbladder and legs from fins as it adapted to inland pools
drying up:
"It is one of those fixed images of evolution: adventurous fish
managing to hoist themselves onto their stubby fins and crawling
clumsily out of the swamps to forage for food. Once these primeval
creatures were on terra firma, their offspring began to adapt to
their new environment, natural selection (over tens of millions of
years) favoring those that developed features well suited to life on
land: paws, hooves, knees, joints, fingers and thumbs. Thus, as
generations of schoolchildren have learned, did these marine
creatures give rise to frogs, birds, dinosaurs and all the rest."
(Nash J.M. , "Where Do Toes Come From?", Time, August 7, 1995, p68)
But, in fact the first tetrapod fish ancestor grew toes and feet
while it was still in the sea, millions of years *before* it needed
them for moving about on land:
"There's only one problem with this familiar version of how our
distant ancestors emerged from the sea: it's probably wrong. For
one thing, the first creatures to waddle ashore were arthropods with
well- developed legs and pincers. For another, newly assembled
fossils-in particular, a 360 million-year-old salamander-like aquatic
animal called Acanthostega- strongly suggest that toes and feet were
developed before the first relatives of fish climbed onto land, not
after. Moreover, in shape and function, Acanthostega's fully jointed
toes bear no resemblance to the spiky, fanlike fins of a fish."
(Nash J.M. , "Where Do Toes Come From?", Time, August 7, 1995, p68)
This was already apparent in 1983, and was included by the
non-creationist Taylor in one of his great evolution mysteries:
"And then, of course, there is the problem of the legs themselves.
Before ever the fish reached the land the structure of its fins began
to change. Instead of rays, a series of bones corresponding to the
tibia, radius and ulna of the arm appeared. Digits, tarsals and
metatarsals evolved (so it is now generally conceded) as wholly new
structures, though the point - unwelcome to Darwinians - was hotly
contested in the 1930s...Though we have this clue in the
bone-structure of the crossopterygian fin there are no intermediate
forms between finned and limbed creatures in the fossil collections
of the world. Once again the critical evidence for gradual evolution
is missing." (Taylor G.R., "The Great Evolution Mystery", Abacus:
London, 1983, p60)
All this is good evidence for prior planning by a far-sighted
Intelligent Designer, not for "blind watchmaker" Darwinian
adaptation-driven macro-evolution.
[continued]
God bless.
Steve
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