You'll recall I asked you if this article had a sketch of the anatomy of the
thing, which is the all important question. You did not answer me, of course,
and now I know why. There isn't one! This was a 3 paragraph blurb in the front
of the magazine, that is entirely unhelpful on this issue.
We have to go back and recall how this all started. Gordon R. Taylor wrote in
his book:
<<The real obstacles to such a move were the massive structural changes needed
to make life on land worthwhile. To bein with, the fish would need legs simply
in order to relieve the pressure of its body on the ground, which would
compress the lungs. >>
And Glenn responded:
<<Sorry to interrupt Mr. Taylor, but you know? Snakes seem to get along just
fine breathing without legs. I can lay on my couch or the floor and breathe
just fine. I think this guy is wrong. >>
Well, it turns out a little research shows that Glenn is wrong. In a section
that Taylor himself could have written, Michael J. Benton talks about the
problems with the fish transition to land:
"The major problems with life on land relate to weight and structural support
as much as to the physiology of breathing air. A fish is buoyed up by the
water and its body weight may be effectively zero. On land, however, the body
as to be held up by some form of limbs, and the skeleton as all the internal
organs have to become structurally modified in order to cope with the new
downward pull of gravity. The backbone of a fish is adapted for the stresses
of lateral stretching and bending during swimming, but the main forces to
which a tetrapod is subject are caused by gravity. The vertebrae and the
muscles around the backbone have to become modified to prevent the body from
sagging between the limbs. The mode of locomotion of a tetrapod on land is
generally different from that of a fish in water." [Benton, Vertebrate
Palaeontology, Chapman & Hall 1990, pp. 46-47]
Unaware of this text, Glenn brought up the "walking" catfish (the quotation
marks around "walking" were put there by the writers of Scientific American,
not I). I asked Glenn for some more information. Didn't get it.
What I did get was an accusation that I had denied their existence (an
accusation Glenn now has to admit was baseless). What I actually said was this
example tells us nothing useful: nothing about its anatomy, but more
important, nothing about its origin. Glenn, of course, assumes it is the
product of evolution. He even assumes it is a transitional form, calling it a
"modern example of fish in transition." It is upon such assumptions that
evolutionary quackery is based. Always assume, never explain.
Anyway, in response to my asking for more information, Glenn starts screaming
"Why can't you admit you're wrong?" Like a latter day Torquemada, Glenn is
more concerned with a coerced confession than with reasoned argument. Well,
this sort of evolutionary fascism may work in Texas, but don't expect your
thumbscrew method of debate to move many in the high culture of L.A.
So I go to look up the article on the catfish. Nothing helpful. But I do
redeem the time by finding the Benton section. Benton goes on to describe the
various problems (echoing Taylor almost exactly) that had to be overcome.
Among them:
* New bones
* Defined elbows and wrists
* Humerus and shoulder joints
* Protective pectoral girdle ("This is because of the additional
forces imposed by the role of the hindlimb in walking and support. The weight
of the body would simply force the pelvic girdle of a fish upwards into its
body cavity if it moved on to the land, and the girdle would twist about
during walking." [p. 49])
"In addition to the problems of locomotion on land, the earliest
tetrapods had to modify the structures associated with feeding and
respiration." [p. 49], viz:
* Lungs instead of gills ("Living lungfishes have functional lungs, of
course, and the same is ASSUMED for osteolepiforms and indeed most other early
bony fishes" [pg. 50, emphasis added])
* Semi-permeable skin coverings to cut down on water loss.
And the BIG question is WHY? Why move onto land? The "classical"
theory (e.g., Romer, 1966), is that depleted water sources due to drought
forced changes in order to keep living in water ("Terrestrial locomotion
evolved as a means of staying in the water!" [pg. 50]), but this has been
criticized as lacking evidence. The "simplest" hypothesis, according to
Benton, is that there were new food sources on land. No evidence for this,
either. But the problems identified by Benton (and Taylor) remain.
In my original message I also pointed out that fish organs are located
ventrally, and thus are even more subject to gravitational pressure on land.
Well guess what? In the lungfish, the lung is located DORSALLY. See, e.g.,
Kenneth V. Kardong, Vertebrates: Comparative Anatomy, Function, Evolution,
(Wm. C. Brown, 1995). Further, the lung is subdivided internally, forming
faveoli which are most numerous in the ANTERIOR part of the lung, and thus
closer to the backbone.
Water breathing fish, however, are completely different. In the
sturgeon, for example, gill ventilation occurs when water enters the mouth,
moves across the gill curtain, and out the opercular opening (ventral).
[Ibid., pg. 414]
Also of interest is Kardong's admission at p. 334: "The musculature
associated with the fins of early crossopterygians (rhipidistians
specifically) was probably too weak to have supplied propulsive thrust
directly for transport on land or to have borne the weight of the body out of
water." He thinks the answer might be that their fins operated like "pegs"
allowing a "pivoting" out of water. This does not solve the pressure problem,
of course, which Taylor and Benton outline. On the next page, Kardong adds,
"Because no one was there to record events, we cannot be sure of the selective
pressures that favored the transition to land."
Of course not. But we can sure imagine some! And these we can call
"fact." And when people refuse to go along with our imaginings, we can accuse
them of "error." Great game. Reminds me of the card game they played in the
movie "Bang the Drum Slowly," called Tegwar. The players would find a rube to
play Tegwar, telling him how to play as they go along, getting him excited,
getting him to bet. He wins a few times. But when the stakes finally get
really high, he starts to lose. Why? Because "Tegwar" stands for "The Exciting
Game Without Any Rules." Those who run the game keep changing it around so
they win every time.
Now, getting back to fish-amphibia: where are the transitions?
Nowhere. Glenn mentions a "catfish" (actually, Sci-Am. said they "look" like
catfish) that we know nothing relevant about, accuses me (first) of denying
it exists (I didn't), but then of somehow being in error because I don't think
this example-we-know-nothing-about proves fish-amphibian evolution!
Sorry, this isn't Tegwar.
Brian wrote:
<<Glenn, you ignorant dork brained dufus headed dweeb nosed slob!!!
Quit begging already.>>
This is unfair. You nose is not "dweebed."
Jim