Generative Entrenchment and the Possiblity of Inheritance.

[Nick Thompson]

Pat,

I agree that the view from under the surface is by far the more interesting
view.  But I am not sure I accept your conclusion about how natural
selection works on a system and its parts.    For the "whole thing to be
inherited",  doesn't it have to be the case  either that removing a
particular peg has an isolatable on the quality of the surface (which seems
to defy general principles of DST) or  that the effects of different peg
removal are additive and cumulative (quantitative inheritance aka trait
group selection.)

I think there is something mysterious going on here in our discussion of
causality.   It seems to me that one represent systems in two
similar-looking but logically different ways. If I write A arrow B I can
mean two quite different things: what goes on in the A thing effects the B
thing; or the A event at time 1 effects the likelihood of the B event at
time 2.  What reveals what is really meant is how the two kinds of diagrams
handle recursion.  The first kind, where the arrow is from one thing to
another,  handles recursion  by having arrows return to thing A.  But in
second kind of diagram, time flow prevents one from ever returning to the
same point in the diagram.  Recursion has to be represented as a series of
lines that keep coming back to the same "column" in a three dimensional
"fasces".  

Now the reason that I go to such  limits to explain this difference is that
i think it plays into our conversation about causal vs systemic thinking.
The contradiction between causal and systemic thinking is really just a
confusion between the two kinds of diagrams.  I have never met a systemic
thinker who was unhappy to draw a line between an event at time one and an
influence on the likelihood of an event at time two, which is what we mean
by causality, so long as that individual was allowed to draw as many of
such lines as he or she desires.  

I also agree with you about bottlenecks.  I was really impressed by Adrian
Kordlandt's craziness about repongification (or whatever he called it) in
African apes, for which he was mocked and which has turned out to totally
the right way to think.  But bottlenecks are not a plus vote for the power
of natural selection.

Which take me back to my original point about natural selection,
inheritance, and developmental systems theory: it is hard to see how we can
have all three, unless selection is presumed to acts to maintain traits as
modules..   In which case we have to ask, at what level does selection act
to do that, OR is there something Kaufmanny that gives us modularity for
free.

Nick

Nick  



I take your point about
Nicholas Thompson
nickthompson at earthlink.net
http://home.earthlink.net/~nickthompson


> [Original Message]
> From: Professor Patrick Bateson <ppgb at cam.ac.uk>
> To: <nickthompson at earthlink.net>
> Cc: <friam at redfish.com>; Jaan Valsiner <jvalsiner at clarku.edu>; lrudolph
<lrudolph at black.clarku.edu>; <dwilson at binghamton.edu>; <rsokol at clarku.edu>;
echarles <echarles at clarku.edu>; elescak <elescak at clarku.edu>; sbarr
<sbarr at clarku.edu>; jogreen <jogreen at clarku.edu>; Gbarker
<Gbarker at bucknell.edu>; <w-wimsatt at uchicago.edu>; <jcshank at ucdavis.edu>
> Date: 5/25/2006 12:45:04 PM
> 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