On Sat, 22 Jul 2000 08:33:16 -0400 "Howard J. Van Till"
<hvantill@novagate.com> writes:
> Bert,
>
> >> Bob Dehaan wrote:
> >>
> >> > I would be happy to take
> >> > macroevolution seriously if there were empirical evidence that
> natural
> >> > selection played a significant *creative* role in it.
> >>
> >> Let me suggest some modification of vocabulary here. I would say
> that
> >> natural selection does nothing whatsoever that is authentically
> *creative.*
> >> Rather, it acts as a positive feedback mechanism in the context
> of a search
> >> program. Briefly here is why I say this:
> >
> > ******
> > Not so fast--Lets substitute for "creative" a different word.
> Yes, there is
> > undeniably a "potentiality space" of viable creatures. Not an
> arugement. The
> > issue is that of a mechanism to shuffle the genes of a given
> animal to move
> > towards the genes of another animal with the second animal having
> some
> > substantial new feature. Now what is "move towards" and how does
> this work.
> > Well, "natural selection" is posited as a selection mechanism and,
> while I do
> > not accept its efficacy in getting the animal through a long path,
> let me set
> > this aside. What I need is
> >
> > 1. A mechanism that can make substantial genetic changes in step
> wise fashion.
> >
> > 2. The existence of a gene trajectory path from animal A to animal
> B with each
> > change being large and benficial enough to modify reproduction
> rates for the
> > animal with the genetic benefits.
> >
> > 3. A quickly acting mechanism to make this happen which is
> triggered by
> > something to be identified because the fossil evidence is for
> stasis with
> > punctuated and rapid changes.
> >
> > What I do not accept is the efficacy of small genetic changes
> which change the
> > general modifiers of a given body plan (a monkey with a longer
> tail) as
> implying
> > the exisitence of the above.
> >
> > This is the issue.
>
> OK, at least we are getting away from the loose and theologically
> provocative use of the word "creative."
>
> If I understand you correctly, you are suggesting that the
> formational
> capabilities of the Creation are inadequate to accomplish what the
> macro-evolutionary paradigm presently envisions. Or are you saying
> that if
> the Creation was given a robust formational economy by its Creator,
> it must
> have important contributions that we have not yet discovered?
>
> My own expectation is that the Creation was gifted from the outset
> with a
> robust formational economy (adequate to make the remarkable process
> of
> macro-evolution possible), much of which remains to be discovered.
>
> Howard Van Till
>
> PS: Sorry I won't be able to answer for a couple of weeks.
I'm not a geneticist, so this is subject to correction. But I recall that
the gene that structures the compound eye in the fruit fly is virtually
identical to the one that structures the retina in both molluscs and
vertebrates. I think the mammalian gene was substituted in a fruit fly
knockout and functioned. I don't know what the gene triggers, or how it
is triggered, to produce these rather different structures. But radical
change is possible. However, probably no one yet knows the intermediate
steps in the shift. Yet this sounds reasonably close to a
macroevolutionary shift within "natural" parameters.
I believe the visual pigments are similar from bacteria to mammals. Where
they are localized to eyes, however structured, there is an advantage to
color vision over simple monochromatic sensation. I believe that both the
original sensory pigments in vertebrates are autosomal. Duplication of
the gene producing blue-sensitive pigment to the X-chromosome and
mutation gave better discrimination. A second duplication (and there may
bve more) produced trichromatic vision. This is distinctly advantageous.
However, the multiple pigments require some "rewiring" in the brain. I
wonder if anyone knows how this is produced, and how the visual areas of
New World monkeys with two pigments differ from the apes with three.
I understand that homeoboxes contain genes which are triggered
successively to produce a pattern of development. I think the fruit fly
has only one, but that it is triggered at least twice, with obviously
different results. Vertebrates have multiple homeoboxes, in keeping with
their more complex structures. However, I have encountered no information
about their triggering. But I will guess that triggering the same set in
different developmental environments may be paralleled by multiple
triggerings of several sets to produce effects so different as to be
totally unexpected. We are just beginning to unravel the complexities.
I recall the professor in a zoology class that I took commenting on the
"bloomin', buzzin' confusion" of everything going on simultaneously to
transform a zygote into an embryo and fetus. "How can we explain it?" he
asked. "God." In other words, it was entirely beyond science to explain
at the time. "Apoptosis," for example, had not occurred to anyone as a
partial explanation for some aspects of development. We are just
beginning to get a handle on some of the "controls." If the speed of
discovery that I have observed over some 50 years continues for the next
50 or so, I expect that we will understand that these duplications and
those mutations produced the major developmental changes from one type of
creature to another, with specifically beneficial states at each step.
Will we unravel the origin of life? I have no way of knowing. But I have
found that we are learning more and more about catalysis, and may stumble
across the process that could have occurred way back when. So I am not
demanding a detailed blueprint before recognizing the strong probability
of divinely installed natural patterns from the earliest beginning to the
present.
Dave
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