> Thanks for your response to my earlier post. Your input is welcome.
> In a message dated 9/11/98 you wrote:
[my stuff cut out...]
> My problem with the various concepts of evolution that you mentioned
> --neutral drift, syntheticism,
"Syntheticism" is the idea that selection plays the most important
role in things like speciation and in the acquisition of new
traits. I might be wrong, but I think this view is sometimes
called, "ultra-Darwinism".
> change in gene content and frequency
> within populations, self-regulated chromosomal rearrangements--is that
> they seem to have no relationship to each other or to Neo-Darwinism.
> Are they alternatives to ND, as I suspect they are? Are they subsets
> of ND? Are they back-up concepts, or fall-back positions, to be used
> when ND fails as an explanatory concept?
I see them as arising from interactions and mechanisms that were not
previously understood. Simply put, the biology of life (including
genetic and regulatory systems) is not simple and therefore the actual
paths taken during evolution are going to by highly context dependent.
All these things, neutral drift, rearrangements, & etc. have been
observed. Neo-Darwinian mechanisms are simply part of a larger milieu
which can affect the evolution of organisms & species.
For the question, "What shaped the evolution of life?", neo-Darwinism
is just one of the mechanisms. It represents a subset that will
presumably be a part of a package of evolutionary mechanism.
> Let me propose this: They are all ad hoc concepts that evolutionary
> biologists call on when natural selection, i. e., Neo-Darwinism, is
> unable to account for change or development. I would appreciate your
> response, if you will, to that proposition.
That may be true in some cases. But I think what more often happens is
that someone finds another mechanism that can influence how certain
traits are distributed in a population. This makes the picture more
complicated.
Think of meteorology. One mechanism that influences the weather is
the diffence in temperatures between the sea and land. However, that's
not the only thing that determines whether it will rain next Tuesday.
> My oversimplified understanding of the history of science is that in
> order to explain a new, complex phenomena, a plethora of theories are
> first proposed. After repeated observation and discussions, (sometimes
> rancorous) the one best theory is winnowed out from all the alternatives.
> That becomes the standard theory.
>
> This is in essence what Darwin and later the synthecists did. They ruled
> out all competing theories and declared natural selection the standard
> theory.
I think the first and most important theory developed was common descent
(I know that Darwin wasn't the first to think of this). The next step
was to look for what the mechanisms were behind common descent. Natural
selection was part of what Darwin championed, which at the same time
provided a possible mechanism for common descent and increased the
likelyhood of evolution's general acceptance.
> Simpson is very clear on this. Now, however, we have again a plethora
> of theories, not competing with natural selection, but in some un-
> specified way, perhaps related to it, or supplanting it. But there is
> no theoretical framework in which these various concepts fit, except
> for the vague umbrella concept of evolution. I find this unsatisfactory
> theoretically, although some evolutionist depict this as a gain over
> the older concept of natural selection? Is it?
There is an empirical "framework" (ie. what we've know about organisms and
their histories) in which these concepts must fit. The umbrella concept
is evolution, which is not vague.
What is vague is how all these mechanisms operate (or have operated)
in various organisms and populations to produce the diversity of
life seen today. For example, evolution is going to proceed very
differently for one species in which all genes are under selection
vs. another where a fewer proportion of genes are capable of being
selected. It's also going to proceed differently in an organism
that can shuttle bits of genomic information between its neighbors
vs. one that can't.
> Moreover, I find little, if any relating of the concepts of evolution
> to observed data in concrete ways. Take Shapiro's four categories of
> molecular discoveries--genome organization, cellular repair capabilities,
> mobile genetic elements, and cellular information processing. Can anyone
> account for them with current definitions of evolution?
"Account for them by" or "work them into" evolutionary mechanisms?
If anything, and if true, the mechanisms and systems cited by Shaprio
might make it easier for organisms to evolve. In a way that leads
to the question of whether "evolvability" can evolve -- which was the
topic of the PNAS paper I cited.
> Thanks for any enlightenment you can give me on these matters.
I'm probably providing more smoke than light...
Regards,
Tim Ikeda (tikeda@sprintmail.hormel.com) despam address before use