From: alanf@tekig6.PEN.TEK.COM (Alan M Feuerbacher)
Newsgroups: talk.origins
Subject: Re: Origin of carniverous plants
Date: 26 Sep 92 18:37:28 GMT
Organization: Tektronix, Inc., Beaverton,  OR.

In article <Bv4A3p.H3B.2@cs.cmu.edu> kck+@cs.cmu.edu (Karl Kluge) writes:
>> Subject: Origin of Carnivorous Plants
>> [....]
>> I have some questions for evolutionary biologists about convergent
>> evolution in carnivorous plants.....
>
>When the radial seismoid (sp?) bone evolved in the bears, what selective
>advantage might be proposed to carry that along until Pandas came along and
>mutated to eat bamboo? You are assuming that those features survived so that
>one grand and glorious day they could combine to produce a carnivourous
>plant. You are assuming that evolution works by evolving towards something.
>It doesn't. I could try to construct "just-so" stories, but I won't. I'll
>simply point out that any theory to explain the advantage of these partial
>stages has the advantage over creationism of being testable. 
>
>Why do you think this is a new argument?

I'm well aware this is not a new argument.  It's just that in my
attempt to understand evolution (admittedly incomplete) I don't recall
reading a really good explanation of the problem, by which I mean one that
I finished reading with a feeling that I really understood the answer.

This sort of problem is much more severe with typical creationist writings.
I've never read a creationist book that really addresses the relevant issues.
I always get the feeling the writers are trying to put one over on the reader.

>                                         Many plants independently evolved
>many sorts of complex contrivances to get insects to aid in their
>pollenation. All of them involve the adaptation of preexisting structures to
>do the trick. A creator isn't constrained to work that way. Evolution is. 

I understand the idea of adapting preexisting structures.  Let me try to
better explain my difficulty in understanding.  First let me state that I
reserve judgement about whether a creator exists or not, and that I accept
all the evidence that evolution has occurred.  It was, in fact, the discovery
that my former religion had completely misrepresented the evidence for
evolution, as well as about other things in science, that led me to give
it up.

There are an extremely large number of possible mutations, given the
complexity of DNA.  I would think that if were true that a major mechanism
for evolutionary change is the adaptation of preexisting structures to new
uses, most populations would display a tremendous number of structures
that are partially formed, in the sense of not being used, such as the
radial seismoid bone in bears.  It's not that such things don't exist,
but that I would expect there to be a *lot* more of them.  Only then would
there be enough "raw material" to adapt to a random environmental change.
Maybe I don't have enough knowledge of examples of such things, but I am
not aware of very many structures that are useless, or even that don't work
well.  Nearly all structures I'm aware of are said to be the result of long
ages of refinement by natural selection, rather than excess baggage being
carried along.

You said above:

>            I could try to construct "just-so" stories, but I won't. I'll
>simply point out that any theory to explain the advantage of these partial
>stages has the advantage over creationism of being testable. 

Can you point me to examples in the literature where such a theory has
been proposed and tested?

If I am misunderstanding these points, please help to clear them up.

Alan Feuerbacher
alanf@atlas.pen.tek.com