jrg13 at psu.edu
Fri Sep 18 17:16:23 EDT 1998
Further discussion relating to comments by Rikki Hall
>Perhaps you should check out _Phenotypic_Evolution_ by Schlichting and
>Pigliucci as well as the numerous journals devoted to evolutionary
>theory. Laws of growth, ie. chromosomal organization, the
>genotype-phenotype gap, norms of reaction, ontogeny, these are all
>extremely active topics among those who study evolution.
Much of what you describe above relates more to what biologists often call
constraints on variation, but still regard no evolution taking place (in
without a natural selection process. I have not read Schichting and
Pigliucci, so will be pleasantly suprised if they give active disucssion to
orthogenetic processes. I will certainly check. Darwin, as I have
statements on laws of growth, was not simply referring to constraints.
>These things are probably not discussed in arguments with Creationists
>since those kind of arguments rarely reach a level of sophistication,
>rationality, or pertinence which might allow these more subtle issues to
>come up. Likewise with textbook writing, which is a highly politicized
I don't understand what's subtle about orthogenesis. Could you clarify please?
>But sure, there are plenty of biologists out there who wonder why
>butterflies haven't evolved a gene that will keep them out of the road,
>while not pausing for a second to consider where and how a gene could
>act to accomplish such a task.
Orthogenesis does not involve the production of genes to accomplish a
Still, I think that it is absurd to say that evolutionists ignore laws of
As above, I will look Schlichting and Pigliucci. If I said "evolutionists",
of course I made
an incorrect statement as there are evolutionists such as myself who do not
laws of growth.
>>These mechanisms, proposed by molecular geneticists change
>>the whole concept of mutation from as "random" to oriented process >(i.e.
>>there may be a bias in the mutation process in consequence of current
>Just because mutation is biased does not mean that mutations don't still
>happen by chance. It just means that the probability distribution
>function is not uniform across the DNA molecule. That is problematic
>for people doing molecular phylogenies, where a constant mutation rate
>is primary assumption, but it is hardly surprising or disrputive of
>evolutionary biology as a whole.
Perhaps I would agree with you on this, although it does not change
>The "force" of natural selection is reproduction and birth. Nothing
>alive gets here except by the force of natural selection. I don't
>understand what you are saying. Perhaps you could provide an example of
>a novelty arising by this other force you allude to. That way we could
>move from possibly considering your point to actually considering it.
A new mutation arises (chance or whatever) in an individual. This
with another. The offspring all have the mutation. These offspring mate
individuals without the mutation. All individuals of this generation also
the mutation. The mutation gradually spreads through the population without any
differentiatl success in the fecundity of those individuals with the
mutation, but all
offspring will have that mutation.
>Wings and leaves may have a common structure due to the ways in which
>one tissue type grows into another during development, but this is
>completely irrelevant in terms of the evolutionary origin of either
>structure. I think that you are conflating the developmental origin of
>a structure with its evolutionary origin.
Yes I am suggesting a historical relationship between developmental origin
and evolutionary origin. Its not just a common structure I am suggesting,
but that similar pathways developmentally and historically were involved. I
acknowledge we may disagree. I envisage the
possiblity that wings evolved through a series of mutuations arising and
without increasing the fitness of those individuals with the mutations
(series - assuming that
wings in their modern form did not arise in a single step).
Sincerely, John Grehan
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