[From Rick Marken (980615.1230)]
Bob C.(980614.1122 PT) --
I'm not sure how much neo-darwininian theory would have to be
altered to be consistent with PCT, and I'm more interested in
seeing a selectionist model consistent with PCT.
I'm more interested in seeing models that are consistent with the
observations.
I think that the question of whether selection is internal or
external is probably one of those misleading dichotomized
questions.
The "internal" vs "external" dichotomy I'm talking about has to
do with the _selection mechanism_. In "natural selection" models
the selection mechanism is _external_ to the organism; it is the
environment. "Darwin's Hammer", that selects; "fit" organisms
survive and reproduce; "unfit" organisms die. In the "purposeful
selection" model the selection mechanism is inside each organism --
probably inside the cell of each organism; the selection mechanism
is equivalent to a set of reference signals specifying the required
state of some set of critical variables; the greater the deviation
of the state of the critical variables from the reference state,
the more likely a genetic mutation. So the internal selection
mechanism (reference signals) selects the genetic similarity of
offspring to parents; if critical variables match references,
offspring will be very similar parents (population rate of mutation
will be low); if critical variables deviate from references,
offspring will be somewhat different from parents (population rate
of mutation will be high).
Best
Rick
ยทยทยท
--
Richard S. Marken Phone or Fax: 310 474-0313
Life Learning Associates e-mail: rmarken@earthlink.net
http://home.earthlink.net/~rmarken
[From Bob C. (980616.0015)]
Rick Marken (980615.1230)
In the "purposeful
selection" model the selection mechanism is inside each organism --
probably inside the cell of each organism; the selection mechanism
is equivalent to a set of reference signals specifying the required
state of some set of critical variables; the greater the deviation
of the state of the critical variables from the reference state,
the more likely a genetic mutation. So the internal selection
mechanism (reference signals) selects the genetic similarity of
offspring to parents; if critical variables match references,
offspring will be very similar parents (population rate of mutation
will be low); if critical variables deviate from references,
offspring will be somewhat different from parents (population rate
of mutation will be high).
If I understand you correctly, what you have proposed is a mechanism which
varies the rate of mutation according to the error of critical variables.
Such a mechanism might exist and accelerate evolution in a time period, but
I'm not sure I'd call this a selection mechanism as it seems more of a
variation mechanism. In any case it is what it is. Further, I don't not see
how this makes unessisary the contribution of external factors in selection.
It seems to only beg the question of why there would be a large error in
critical variables in the first place. Probably because individuals in a
given population are having trouble controlling variables/countering
disturbances in the external world which they need to do in order to survive
and reproduce. In your model, if the world were compliant, there would be no
variation and hence no selection. The only way an animal survives and
reproduces is via interaction with environment and I don't see any way around
it.
Bob C.