Generative Entrenchment and the Possiblity of Inheritance.

[Nick Thompson]

Oh, and one more point.  

I think I agree with your critique of eric's comments, but only if we
concede that a system that is not highly canalized in most respects cannot
be available for mutation and selection in any.  

Nick

Nicholas Thompson
nickthompson at earthlink.net
http://home.earthlink.net/~nickthompson


> [Original Message]
> From: Professor Patrick Bateson <ppgb at cam.ac.uk>
> To: Eric Phillip Charles <ECharles at clarku.edu>
> Cc: ForwNThompson <nickthompson at earthlink.net>; <friam at redfish.com>; Jaan
Valsiner <JValsiner at clarku.edu>; lrudolph <lrudolph at black.clarku.edu>;
<dwilson at binghamton.edu>; Sokol, Rosemarie <rsokol at clarku.edu>; Lescak,
Emily <ELescak at muse.clarku.edu>; Barr, Shawn <SBarr at muse.clarku.edu>;
Green, Jonathan <JOGreen at muse.clarku.edu>; Gbarker <Gbarker at bucknell.edu>;
<w-wimsatt at uchicago.edu>; <jcshank at ucdavis.edu>
> Date: 5/26/2006 12:00:47 PM
> Subject: RE: Generative Entrenchment and the Possiblity of Inheritance.
>
> Replying quickly to Eric's argument, I don't think it follows that,
because
> a developmental system is buffered, any change (genetic or environmental)
> that can break down the buffering will necessarily be catastrophic. Often
> maybe, but not always. If the outcome were always disastrous, how is it
> that organisms can evolve resistance to compounds designed to destroy
them?

> It's easy to forget that evolution is not determined by probabilities but
> by the few individuals that make it through a potential extinction event
> like the massive change in ocean acidity in the Permian. So, I repeat, no
> paradox.
>
> Pat
>
> On May 25 2006, Eric Phillip Charles wrote:
>
> >Hey all,
> >    I understood the "fundamental" problem of entrenchment to be a bit
> > different than what either Nick or Pat have presented. The complexity

of

> > a generative system can be thought of as "entrenchment" because it acts
> > to buffer against change (it creats trenches in the epigenetic
> > landscape). The reason this occurs is because, as the system gets more
> > and more complex (read - convoluted), it is increasingly likely that a
> > random change (in genes OR environment) will be catastrophic. Further,
> > when we think of whole organisms, rather than individual traits, it
> > becomes obvious that the generation of traits become entangled in the
> > entrenchement.
> >
> >     Imagine that we humans routinely develop an ancient mammalian Rube
> > Goldberg machine that takes 46 steps to make sure we were born with

five
> > fingers. Imagine too, that more recent evolution had connected one part
> > of the old machine with a new machine that shrinks our upper jaws
(giving
> > us chins), two parts are now co-used with the machine that determines
how
> > quickly we learn a language, one of the language/finger overlap parts
has
> > also become crucial to the otherwise ancient machine that makes sure we
> > have sweat pores, etc., etc. It is bizzarely unlikely that any change
in

> > the system will result our developing the same machine at a "cheaper"
> > cost, or developing a machine that produces more beneficial outcome. It
> > is also unlikely that any change in the machine will effect change in
> > only one trait. The claim that evolution must be "predominantly
> > accretionary", means to point out that such system are unlikely to be
> > modified adaptively, except by adding another step at the end of the
> > machine (thus increasing complexity yet again).
> >
> >     The "GE paradox" is thus that: 1) We accept that Darwinian
> > evolutionary processes should almost inevitably lead to genearative
> > entrenchment. 2) Entrenchment makes future changes very difficult

without
> > catastrophy. 3) Entrenchment makes modular change particulary
difficult.
> > 4) Darwinian selection seems weakened if only accretionary change is
> > allowed. 5) Darwinian selection seems cripled if selection cannot act
on
> > traits in a relatively modular fashion. 5) We think Darwinian selection
> > has been happening for a long time, is happening now, and will continue
> > to happen into the future. ---- But, if Darwinian selection leads to
> > conditions which counter Darwinian selection, will it not eventually
> > grind itself to a halt?
> >
> >     The two most likely solutions to the parodx seem to be: a) We have
> > not reached the halt point yet, but it is coming, i.e., point 5 is
wrong;

> > or b) What seems the case is not the case, i.e., points 3 and 4 are
> > wrong.
> >
> >Just hoping to clarify the problem.
> >
> >Eric
> >
> >
> > P.S. Note that the machine "develops", thus avoiding giving special
> > credit to genes or environment in its existance. A major change in
> > environment should effect a new machine just like a major change in the
> > genes. Here, minor changes in the environment (defined circularly by
> > non-effect) are equivalent to genetic changes which do not alter

protein
> > structure.
> >
> >
> >
> >
> > -----Original Message----- From: Professor Patrick Bateson on behalf of
> > Professor Patrick Bateson Sent: Thu 5/25/2006 10:45 AM To:
ForwNThompson
> > Cc: friam at redfish.com; Jaan Valsiner; lrudolph; dwilson at binghamton.edu;
> > Sokol, Rosemarie; Eric Phillip Charles; Lescak, Emily; Barr, Shawn;
> > Green, Jonathan; Gbarker; w-wimsatt at uchicago.edu; jcshank at ucdavis.edu
> > Subject: Re: Generative Entrenchment and the Possiblity of Inheritance.
> >
> >Dear Nick
> >
> >Apologies for the delay in replying. I have been at a conference - on
the
> >evolution of intelligence.
> >
> > As you will have guessed from our previous exchanges on this issue. I
> > think the paradox is illusory. Wimsatt and Shanks' notion of
entrenchment
> > is very similar to Waddington's notion of canalisation. However, he
> > didn't share your difficulty (and that of Wimsatt & Shanks) in
> > understanding how the trajectory of development might be changed.
> > Famously, in iluustrating how his image of the epigenetic landscape
might
> > reconfigure, Waddington drew another picture of the landscape from
> > underneath. A series of pegs, representing genes, are tied by guy ropes
> > to the underside of the tent giving it its shape. (To instantiate the
> > image ties on the upper side of the landscape are needed in order to
> > create the valleys that canalise development - which makes a nice
> > didactic point!) Anyway Waddington supposed that if the guy ropes were
> > tightened or slackened (corresponding to mutation or epigenetic
change),
> > then the shape of the landscape could be altered. As in any other
dynamic
> > system, some alterations in conditions generating the outcome of the
> > developmental process produce no effect. Other alterations can have a
> > dramatic effect. The system may be relatively stable but it isn't
> > impervious. If a change in the outcome is beneficial and alteration in
> > the factor instigating that change is a gene, then the whole system
will

> > be inherited. If you stop thinking in terms of causal arrows between
> > genes and phenotypes as being the only way of obtaining adaptations and
> > start thinking in terms of systems, then your paradox evaporates.
> >
> >Warmest
> >
> >Pat
> >
> >On May 20 2006, Nicholas Thompson wrote:
> >
> >>Dear Loose group of Correspondents,  
> >>
> >> For a couple of years now, you all have been suffering with my
> >> inability to state what seems to me a fundamental paradox arising from
> >> the Developmental Systems Theory: that natural selection is impossible
> >> without inheritance and inheritance seems increasingly impossible

given
> >> the complexity and chaos of developmental systems as we are coming to
> >> know them. I have just come across a clear statement of this paradox
in
> >> Wimsatt, W. C. and Shank, Jeffrey C. (2004). Generative entrenchment,
> >> Modularity, and Evolvability; When Genic Selection Meets the Whole
> >> Organism. In, Schlosser, G. and Wagner, G. P. Modularity in
development
> >> and evolution. Chicago: University of Chicago Press. The title would
> >> seem to suggest that the problem they identify relates ONLY to the
> >> relation between the organismic and the genic level, but in fact it is
> >> potential troublesome at all levels of selection.
> >>
> >> The generative structure of the system (including the organism plus
> >> relevant aspects of its environment) has a characteristic set of
causal
> >> interactions which could be variously represented. One of the simplest
> >> representations is a directed graph, where nodes are parts, processes,
> >> or events, and arrows are consequences of the presence or operation of
> >> notes on other nodes. For each node, consider how many other nodes can
> >> be reached from it by following the arrows. This indicates how much of
> >> the phenotype is downstream of, causally dependent on, or affected by
a
> >> given node. We define Generative Entrenchment as the magnitude of this
> >> downstream dependence. [Page, 360, Caps and italics by nst]
> >>
> >> Darwinian processes should almost inevitably give rise to generative
> >> structures (Wimsatt 2001). However, we are still left with two
> >> perplexing questions: How can complex adaptive systems evolve and
> >> continue to evolve in any other than a predominantly accretionary way
if
> >> their generative elements become increasingly entrenched with
increasing
> >> complexity (Shank and Wimsatt 2000). How does this permit continued
> >> modular evolvability? It is no surprise, therefore, that fundamental
> >> research focus of the evolutionary sciences is to figure out how
complex
> >> systems can continue to evolve when evolutionary processes generically
> >> give rise to entrenched structures. We call this the G[enerative]
> >> E[ntrenchment] paradox. [Page 363
> >>
> >> In these passages, Wimsatt and Shank lay out with perfect clarity the
> >> problem I have been fumbling with. However, by focusing on Generative
> >> Entrenchment, they conceal one startling implication that I see in
their
> >> view (possibly because they don't believe it). Generative Entrenchment
> >> threatens Natural Selection because Natural Selection requires some
sort
> >> of inheritance, and, so far as I can see, any trait that is
Generatively
> >> Entrenched cannot be inherited at the level at which it is entrenched.
I
> >> think I perhaps have a solution to this problem, but I will hold off
> >> offering it until I have convinced anybody of the existence of a
problem

> >> to be solved.
> >>
> >>I apologize for intruding on your otherwise Peaceful saturday.
> >>
> >>Nick
> >>
> >>
> >>Nicholas Thompson
> >>nickthompson at earthlink.net
> >>http://home.earthlink.net/~nickthompson
> >
> >