Re: [2] The evolution of "evolution"

From: Scott Chase (osteopilus@yahoo.com)
Date: Sat 15 Oct 2005 - 13:00:07 GMT

  • Next message: Scott Chase: "Re: Re[2]: [2] The evolution of "evolution""

    --- Chris Taylor <christ@ebi.ac.uk> wrote:

    > Now normally I'd just sit back and watch you take on
    > everyone
    > else with your usual joie de vivre, but I have an
    > issue:
    >
    > > Once environmental conditions change
    > sufficiently, the
    > > organism is free to ignore its heritage and try
    > something
    > > novel. Underneath the principle of memory lies
    > the principle
    > > of freedom.
    >
    > I confess I didn't read the article as I'm a bit
    > snowed at the
    > moment, so if it addresses the above then sorry
    > but...
    >
    > What exactly is involved in 'trying something
    > novel'?
    >
    > Are we talking fuzzy broadcasting, or deliberate
    > (evolvable?)
    > variance? Random, or directed on some meta-level of
    > ever
    > higher-order patterns?
    >
    Too bad humans aren't free to ignore their heritage. Lower back bain is a serious reminder!!!

    Why do human embryos go through the trouble of developing stuff similar to other vertebrate embryos if they are free to forget their heritage? Why a notochord? Do we develop this so we can harbor the remnant stucture within our intervertebral discs
    (pulpy nuclei)? Ouch! Why the pharyngeal arches? Why are our ear ossicles homologous to jaw structures in distant ancestors, modern reptiles
    (articular-quadrate) and sharks? Sounds like a
    *Bauplan* to me.

    "Novelty" tends to be nothing more than taking old stuff and using it differently. Stuff with an origin for something entirely different (jaw articulation) can shift function and have current utility for hearing. Yet the embryonic origins are pretty much the same. *Amphioxus* has a notochord. We have slipped discs. Ouch!

    Try as we might, we can't escape our past. When you hear victims of thw great white shark scream in
    _Jaws_, you are using ear structures related to the jaw stuctures the shark is using to make them scream. Gould's essay "Earful of jaw" is co-optable for the obvious pun and useful for a better explanation of this relationship than I can muster. Oh, I'm using his ideas of historic origin versus current utility too. Kent and Miller's _Comparative Anatomy of the Vertebrates_ is useful for the gory details. Gotta love morphology there gene boy :-)

    Wait, Hox clusters are archetypal too. Don't leave them out.

      

                    
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