Re: The evolution of "evolution"

From: Scott Chase (
Date: Thu 13 Oct 2005 - 13:58:15 GMT

  • Next message: Joel.M Dimech: "Re: The evolution of "evolution""

    --- Derek Gatherer <> wrote:

    > and the very last one:
    > on an eye development paper I mentioned:
    > >As you can see, the authors make no claim for
    > having discovered a design for
    > >the eye of any species. They merely point out what
    > has long been
    > >established, namely that genes "regulate" or
    > influence development. What
    > >genes do is to cause development to go down one
    > path as opposed to another.
    > >By causing some proteins to be produced but not
    > others, genes distinguish
    > >individuals from each other. They do not provide
    > the overall plan of
    > >development, only tweaking it one way or another.
    > Oh come on, this is a sophistry! When the gene
    > regulatory network is
    > controlling every single aspect of the developmental
    > process, it is
    > equivalent to design. Developmental biologists can
    > _redesign_ flies
    > at will by manipulating gene expression. Want a fly
    > with feet
    > sticking out of its head, 4 wings and a double
    > abdomen with no
    > vibrissae and and excessive number of hairs? No
    > problem. As an
    > extra we could even make it homosexual and perform a
    > repetitive dance
    > for no apparent reason and show an inordinate
    > fondness for the smell
    > of ether. Think that's science fiction? No, that's
    > the extent of
    > our current control over Drosophila embryogenesis.
    > That's
    > design. What do you think design should be?
    > >Genetic reductionism is problematic to say the
    > least. First starters, as
    > >Harry Rubin points out, the sequential combination
    > of genes required to
    > >produce even the simplest organic compounds is
    > vastly more complex than the
    > >sort of physical problems that yield to
    > calculation. Gene combinations are
    > >"transcalculational."
    > That's just wrong.
    Come on Derek. Dace's allusions to action at a distance and organic memory are unhelpful to say the least, but I think you're going too far the other way. You fail to distinguish between gene action and morphology or gene action and behavior. Genes do strongly influence processes leading to eye morphology or to exhibition of certain behaviors (Jonathan Weiner's _Time, Love, Memory_ has an informative treatment of this latter relationship as studied by Seymour Benzer and others), but don't make the reductionist error of conflating the two. Reduction is important to understanding a process, because it's simpler to look at the effect of single factors on a process at a given time, but chopping something out of context can lead to distortion. Genes play a central role in cellular processes but from my recollection it's the cell-cell interaction level where many important things happen (see cell adhesion molecules).

    Ernst Mayr talked about a "somatic program" which I think is a helpful concept for placing gene action in cellular processes in proper perspective. Mayr was a field biologist with some minor apprehensions about genocentric thinking, but well versed in many aspects of biology.

    Take the whole Pax-6 thing for instance. This gene might be shared across phyla and play a significant role in eye development, but I think factors like this can get blown out of proportion, especially in the popular imagination. Headlines read "Gene for eyes discovered". Well are we talking *the* gene for eyes or *a* gene influencing eye development? Surely other genes play a role too. And when comparing the complex eye morphology of an octopod versus a human, there's still some convergence involved so Mayr wasn't completely wrong about convergence across species. There are genes important for eye development that share a deep seated homology across phyla, but there's some convergence at the morphological level
    (vertebrates versus cephalopods). Thus one should distinguish between gene action and resulting morphology lest they oversimplify.

    When genes are manipulated to "redesign" (yuck) organisms, the developmental pathways are being modified. If a Hox gene is tweaked, isn't an early developmental "choice point" being altered, thus resetting the context for subsequent processes, involving the interplay of gene *products* at the cellular level? Cells need a "lexicon" to talk to each other during development. Alteration in a key word can cause some "confusion" and disrupt subsequent communications. It's the conversation that's important though and as there are synonymous words, there's some degree of genetic redundancy. You could knock a gene out, yet very little difference in results because another gene has enough overlap in function to serve as a surrogate. If there were no redundancy (something that overzealous Darwinists might assume as slop that all-pervasive selection should act to remove) there would be no functional shift and thus no evolution. Genes duplicate by unequal crossing over at meiosis and then can diverge, one gene maintaining original function and the other shifting function without causing problems for organismic survival and reproduction.

    I agree for the most part with your pointing out Dace's errors in the way he overlooks crucial work that has been done in understanding development, but don't let your reaction to him cloud your own judgement.

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