From: Dace (email@example.com)
Date: Thu 26 Jun 2003 - 23:39:38 GMT
> From: "Scott Chase" <firstname.lastname@example.org>
> >From: "Dace" <email@example.com>
> > > From: "Ray Recchia" <firstname.lastname@example.org>
> > > Subject: Re: Precision of replication
> > >
> > > All of this gets back to Manfred Eigen's notion of
> > > 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.
> > > placed higher at the top of a fitness peak will be more successful
> > > those at the bottom. Because variation is constantly occurring, no
> > > particular member of a species is exactly the same as any other but
> > > hover about the same fitness peak. Species then becomes defined by
> > > 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
> >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
> >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
> >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
> >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
> 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
> 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
> members to move towards a peak and the genetic undercurrent can catch up
> later, mny generations down the line if this phenotypic outcome is
> 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
> 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
> >before you. To a limited degree, development is a recapitulation of
> >evolution, except that instead of forging a path through struggle over
> >generations, an embryo merely follows the path already laid out.
> Ugghh! Ontogeny is NOT a recapitulation of phylogeny. I sentence you to
> some Stephen Gould on this one. _Ontogeny And Phylogeny_ would be a
> start. Recapitulation itself is a putative mode of heterochronic change,
> 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
> >about following ingrained habit. Individuals can be regarded as
> >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 pathway.
> Whither interbreeding and reproductive isolating mechanisms? Oh yeah, we
> might have to talk about cumulative genetic differences between
> 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
> Why shhould fitness be the exclusive concern. Didn't Darwin himelf hold
> 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
> >thought takes on a "life of its own" and continues promoting itself long
> >after its originator has consciously forgotten it. A meme, then, is
> >a habit of thought that replicates across many minds as it becomes
> >culturally ingrained.
My comment stands. Roughly speaking, evolution is about *rising* to the
challenge of environmental pressure, while development is about *descending*
through a pre-established "path of least resistance." I bring up this
interesting duality because it applies equally well to cultural evolution
and can tell us a great deal about the role of memes. Like natural
evolution, cultural evolution proceeds primarily through creative struggle.
If an idea is to succeed, we must determine consciously whether it's useful.
Once it's well-established, it becomes a habit. A meme is nothing more than
a habit that's become ingrained among numerous people. Therefore memes
represent the developmental (downhill) side of culture rather than the
evolutionary (uphill) side. While memes can accidentally mutate in their
replication, this can never be more than a peripheral source of evolutionary
change, while the main source remains human creativity. This is why
memetics can never adequately describe cultural evolution by itself. As
memes fall on the developmental side of the ledger, it can never be anything
more than a side note in the story of cultural evolution.
I'm well aware that evolution cannot be perfectly equated with adaptation,
but since I'm just making an analogy here, a little simplification is
certainly in order. As to your point regarding Haeckel, there's no sense
trying to refute the rather obvious fact that Haeckel was *essentially*
correct, even if he did fake the evidence in order to amplify his point.
Embryos start out the same regardless of what species they belong to. You
can't tell a human embryo from a fish embryo at a certain stage of
development, and though the gill slits don't actually do anything in human
embryos, nonetheless it's rather striking that even nonfunctional
equivalents of gills are to be found in them. Later on human embryos are
almost indistinguishable from rabbit embryos, and the same holds for human
and monkey embryos at a still later stage. Clearly, *in a limited sense*
embryos recapitulate the evolutionary path that produced the species to
which they belong.
This is way too much detail for a simple analogy. The point I'm making is
about memes, not biology.
What's really interesting about memes is not that they explain cultural
evolution (they do not) but that when they become malignant they explain so
much about the degeneration of culture into cult.
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