Re: Evolution: A few questions

On Wed, 23 Jun 2004 08:49:38 -0400 Mccarrick Alan D CRPH
<MccarrickAD@nswccd.navy.mil> writes:
> Dave,
>
> I am also intrigued by the analogy of the survival of evolutionary
> transitional forms and the survival of metamorphic forms. I think
> that the differences between the two cases need to be clearly
> thought through:
>
> 1. Modern metamorphic changes are well orchestrated by complex
> genetic instructions that apparently have been in place for quite a
> while. True evolutionary transitions would appear to have no such
> internal controls to keep the critter alive. The exact process that
> allows a tadpole to survive the transition from herbivore to
> carnivore are probably rather complex.
>
> 2. (I don't know about this one) In metamorphosis, the end result
> is "known" or purposeful, while in evolutionary transitions, there
> is no goal (TE could insert something here).
>
> Al McCarrick
>
> -----Original Message-----
> From: bivalve [mailto:bivalve@mail.davidson.alumlink.com]
> Sent: Tuesday, June 22, 2004 18:59
> To: ASA
> Subject: Re: Evolution: A few questions
>
>
> > > In contrast even to a benign remodel, let me note what happens
> during the
> > > metamorphosis of a frog.
>
> An additional remodeling that occurs in the development of most
> tadpoles is the change from a vegetarian to a carnivore gut
> (relatively long to relatively short, etc.). Some species are able
> to make the change early, if algae is in short supply. In
> particular, certain species that breed in temporary ponds have
> tadpoles that are able to turn into cannibals if the pond is
> starting to dry up. This gives them an abundant supply of food so
> that they can grow fast and complete the tadpole stage before the
> pond dries up.
>
> Dr. David Campbell

Al,
You seem to be pushing my analogy beyond the scope I gave it. All I
claimed was that, if an aquatic tadpole can become a terrestrial frog
without complications from "bumps," an aquatic creature (minimally
characterized in the absence of many intermediate fossils) can become an
amphibian without difficulty from Vernon's repeated insistence that
"bumps" would render it impossible to survive. There obviously has to be
a great difference between developing what is contained in the genome,
metamorphosis, and the evolutionary development of a genome with the full
set of amphibian characteristics. My sole point is that both may proceed
smoothly.

Positing some control to keep the evolving creature alive makes no sense
within an evolutionary paradigm. The evidence of extinctions demonstrates
that there is no warrant of survival. Indeed, there is no warrant in any
genome that the creature will survive. There are lethal and semilethal
mutations in large numbers. I note that there are few American children
who are killed by predators. Modern medicine protects them from many
infectious diseases. But this was not a characteristic of human life
during most of its existence. Indeed, more primitive conditions exist
over a large part of the earth today.
Dave
Received on Wed Jun 23 15:49:31 2004