From: Scott Chase (firstname.lastname@example.org)
Date: Thu 19 Jun 2003 - 22:33:01 GMT
>From: "Dace" <email@example.com>
>Subject: Idea, habit, meme
>Date: Thu, 19 Jun 2003 12:54:25 -0700
> > From: "Ray Recchia" <firstname.lastname@example.org>
> > Subject: Re: Precision of replication
> > All of this gets back to Manfred Eigen's notion of 'quasi-species' which
> > can be identified mathematically using the concept of a
> > fitness landscape. In a fitness landscape, higher points in one
> > dimension of the landscape indicate more reproductive success while
> > points in that dimension indicate lower reproductive success. Offspring
> > placed higher at the top of a fitness peak will be more successful than
> > those at the bottom. Because variation is constantly occurring, no
> > particular member of a species is exactly the same as any other but all
> > hover about the same fitness peak. Species then becomes defined by the
> > presence of a group of organisms sitting on a slope that is directed
> > towards the same local peak.
>Very interesting. What intrigues me about Eigen's model is that it's
>exactly the opposite of C.H. Waddington's model of development. Waddington
>also uses a hill to illustrate his point, except that in this case the goal
>is to go down the hill rather than up. Picture a hillside with many
>("chreodes") carved into it. If an embryo has gene A, it will take one set
>of grooves down the hill, and if it has gene B, it will take a different
>to the bottom, where it will land at a different place, i.e. it will end up
>with a different set of characteristics.
Didn't Sewall Wright use the metaphor of adaptive landscapes in his theoretical work on drift and selection? I would think he gets priority over Eigen or anybody else, if so. Yes, Waddington used the reversed metaphor in his delelpmental landscape, down versus up.
In an adaptive landscape a population can drift downward instead of being
pulled to a local or global optimum. I'd assume much of evolution is just
getting by "satisficing". Optimality is thus a progressivist claptrap.
In the developmental landscape certain factors could yank an embryo out of a
gulley it's moving down into another gulley, plus certain phenotypic
outcomes can mimic the action of genes typcally associated with these
outcomes (phenocopies *sensu* Goldschmidt, genetic assimilation of
Waddington, or the Baldwin effect).
Thus, this mimicry facilitted by phenotypic plastcty could allow population
members to move towards a peak and the genetic undercurrent can catch up
later, mny generations down the line if this phenotypic outcome is selected
an recombination plus mutation allow for genetic combos to arise that are
specific for this adaptive phenotypic outcome.
Thus, adaptive landscapes can be theoretically melded with adaptive
landscapes. I'm not married to this melding, but have taken it out to dinner
on occasion ;-)
>It makes perfect sense to envision evolution as an uphill climb while
>looking at development as a downhill descent.
Wrong. Adaptation is uphill towards the local optimum. Evolution
(definitionally the change in allelic frequencies within a population over generational time) can go up or down on the adaptive landscape (up if selection is the primary factor; down if genetic drift is the primary factor). QED.
>The reason is that evolution
>is a struggle to attain greater fitness in order to be environmentally
Like hell. Evolution is NOT synonymous with adaptation.
>Development, on the other hand, is all about following the path
>of least resistance. You simply slide down the trail your ancestors blazed
>before you. To a limited degree, development is a recapitulation of
>evolution, except that instead of forging a path through struggle over many
>generations, an embryo merely follows the path already laid out.
Ugghh! Ontogeny is NOT a recapitulation of phylogeny. I sentence you to read some Stephen Gould on this one. _Ontogeny And Phylogeny_ would be a great start. Recapitulation itself is a putative mode of heterochronic change, but neoteny is another. Garstang, a champion of neoteny and paedomorphosis, said something to the effect that ontogeny creates phylogeny, which turns Haeckel's simplistic nonsense on its head.
>is all about creativity (the true "creationism"), while development is all
>about following ingrained habit. Individuals can be regarded as belonging
>to a common species when: 1) they reside on slopes directed to a common
>fitness peak and 2) their offspring descend through a common developmental
Whither interbreeding and reproductive isolating mechanisms? Oh yeah, we might have to talk about cumulative genetic differences between populations. Sorry, I forgot.
>Culture involves the same dual process. On the one hand, we create and
>promote ideas based on their fitness. On the other hand, when an idea is
>repeated enough, it becomes habitual, and our thinking merely follows the
>synaptic patterns already laid out for it. When a habitual pattern of
>thought is transmitted and becomes a culturally-shared habit, it's a meme.
Why shhould fitness be the exclusive concern. Didn't Darwin himelf hold that selection is primary but not exclusive?
>My point is that "habit" is the missing middle term in memetics. While a
>new idea must be consciously reconstituted each time it appears, a habit of
>thought takes on a "life of its own" and continues promoting itself long
>after its originator has consciously forgotten it. A meme, then, is simply
>a habit of thought that replicates across many minds as it becomes
Would you hold that an idea, when ingrained deep enough, can jump Weismann's barrier?
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