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Re: Sci. Am. - present. [long]



Andrew Robinson wrote:
>As an Amateurid (hopefully Gottaclueidae), 
        I have a bad feeling that this is gonna get real old. The first post
was pretty funny, though...

>this timing issue is the one thing that bothers me about the birds from
>dinosaurs hypothesis.
        Yeah, it's pretty annoying. However, this is one instance where
overwhelming biological evidence overrides geological interpretations. Not
that there *is* any geological evidence against the dinosaur-bird link
(there cannot be, how do you prove the non-existance of something?). What we
have is a phylogenetic hypothesis which does not necessarily correspond to
the stratigraphic sequence of the fossils. We also have the rather
well-founded observation that the terrestrial vertebrate fossil record is
very incomplete, the intervals of relatively higher completeness are
restricted as far as variety of ecosystems recorded, and are sporadic in
temporal distribution. This leads readily to the conclusion that the
paleobiological conclusion (which is, again, well founded) is closer to
being correct than conclusions based on stratigraphic distributions.

>However, this type of response from the BFD camp bothers me even more.
        I've been accused of being a cat, a whale, a bull in a china shop,
and dozens of other things, but never before have I been called a camp. :)
        As for everyone else who buys this line of reasoning, they do so
because of years of experience dealing with the aforementioned incomplete
vertebrate fossil record. I find "this type of response" to be intuitively
pleasing, because it accounts for the morphological and stratigraphic data
in a manner which makes sense.
        Try this: Take forty shoe boxes, fill them with marbles, yellow
marbles for birds, blue for very close bird relatives, red for other
theropods, white for everything else. Fill each shoe box with marbles
(dinosaurs). Each should have 200 marbles, of which some will be colored
(for theropods). In the first box, the colored marbles will only be red.
Fill the colored ones as follows. Note that, since non-avian theropods are
in competition, their total numbers remain about the same:

Box: 1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20+

r:  20 19  18 18 18 18 18 18 18 18 18 18 17 16 15 14 13 12 11 10
b:   0  1   1  2  2  2  2  2  2  2  2  2  3  4  5  6  7  8  9 10
y:   0  0   0  1  1  3  5  7  9 11 13 14 15 15 15 15 15 15 15 15
        
        Next, shake up the box, and remove any yellow marbles you can see at
the surface (represents differential preservation of bird fossils). Now,
divide the boxes into groups of five. Randomly select 4 of the groups of
five and remove them from the experiment. Select two boxes from each of the
remaining four groups of five boxes. These are your bone-bearing formations.
Now, stick your hand into each of the eight shoe boxes you have and pull out
a handfull of marbles. Reconstruct the evolutionary sequence using only
those marbles. A few repetitions should convince you that this won't work.

>It reminds me of arguments by the Aquadic 
>Ape enthusiasts on sci.archology, "We must be right because 
>there are no fossils to prove us wrong."
        Actually, this statement reminds me more of the BCF argument, except
that would be phrased as "We must be right because there will never be
fossils to prove us wrong."
        For the conventional dinosaur-bird hypothesis, the argument is: "the
fossils we have say we are right, we just haven't found all the fossils."

>Why not just admit that this is a problem and that you are working to
resolve >it?
        No one is denying that it is inconvenient, and some would go so far
as to say that it's a problem, but resolution may never come. If one waits
for the right fossils to come along, one may be waiting a long long time.

        Wagner
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
              "I'm being nibbled to death by cats" - L. Molari