Re: Morphogenetic fields

From: Scott Chase (ecphoric@hotmail.com)
Date: Wed 11 Jun 2003 - 04:32:00 GMT

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    >From: Keith Henson <hkhenson@rogers.com>
    >Reply-To: memetics@mmu.ac.uk
    >To: memetics@mmu.ac.uk
    >Subject: Re: Morphogenetic fields
    >Date: Tue, 10 Jun 2003 23:15:58 -0400
    >
    >At 05:51 PM 10/06/03 -0700, Dace wrote:
    >><Keith>
    >>
    >> > "Until recently, the interactions that constituted these fields could
    >>not
    >>be
    >> > identified. However, the discovery of the homologous pathways of
    >>development
    >> > has given us new insights into how these fields are established and
    >> > maintained."
    >>
    >>Okay. And what determines the "homologous pathways of development?"
    >>Genes
    >>or fields?
    >
    >"Homologous pathways of development" = similar pathways of development
    >between insects and mammals. I.e., body plan genes that "instruct" (via
    >chemical gradients) a hollow ball of cells into becoming an animal go back,
    >*way* back, to the common ancestor.
    >
    >>Whatever answers researchers come up with cannot help but be
    >>provisional. Every answer merely moves the question back a step.
    >>Ultimately, the information is either particulate or holistic.
    >>Ontogenesis
    >>is either bottom-up or top-down. Since biochemists are no closer than
    >>they
    >>were forty years ago to providing a detailed picture of how genes build
    >>bodies, there's no reason not to explore other possibilities. Indeed,
    >>this
    >>is the general trend of contemporary biology.
    >>
    >> > I really wish you would use Google more.
    >>
    >>You're playing a trick on yourself-- digging up a little sliver of
    >>information that confirms your prejudice and then imagining you've solved
    >>the case.
    >
    >I am citing web locations we can both locate to show that what I understand
    >from decades of reading details about these areas of science is commonly
    >accepted knowledge. Also, I don't have the time to type in all the
    >supporting details, so I cite others who say what I would say if I had
    >time.
    >
    >> > > > Sample articles
    >> > > >
    >> > > > Reference: Scientific American February 1994 PAGES 58-66
    >> > > > Articles Name- The Molecular Architects of Body Design.
    >> > > > By William McGinnis and Michael Kuziora
    >> > > > Jest of Article- Putting a human gene into a fly may sound like the
    >> > basis
    >> > > > for a science fiction film, but it demonstrates that nearly
    >>identical
    >> > > > molecular mechanisms define body shapes in all animals.
    >> > >
    >> > >If the molecular mechanisms are the same, and the organisms are
    >>radically
    >> > >different, doesn't that demonstrate that organisms are not a product
    >>of
    >> > >molecular mechanisms? This is a huge problem for the mechanistic
    >>theory
    >>of
    >> > >life.
    >> >
    >> >
    >> > Hardly. "Body shapes" at the level of having a head to tail, left to
    >>right
    >> > and front to back are common from insects to elephants and they all
    >>start
    >> > from a single cell. That the same mechanism (hox genes) lays out the
    >> > developmental axis only indicates animals with bilateral symmetry had a
    >> > common ancestor.
    >>
    >>It says we have a common ancestor, and there's no discernible reason why
    >>we
    >>don't look like flies.
    >
    >Your above conclusion convinces me (as to the usefulness of further
    >discussion).
    >
    >
    Aren't flies and humans segmented (though not as obvious in post-embryonic humans with skin covering) pointing to early acting and homologous developmental processes and a phylogenetically early common ancestor? I vaguely recall a term for a hypothetical common ancestor called
    *Urbilateria*. Google that one for kicks.

    You'll get nowhere with Dace on this one so don't sweat it. You've done a great job of countering his rhetoric. Psi phenomena have no place in developmental biology. Whatever use morphogenetic fields have as a concept, they are probably best considered as placing genes in a developmental context and as a way of getting away from simplistic reductionism (perhaps even as far as putting the "selfish" evolutionary gene of Dawkins and Williams in its place, taking some wind out of its rhetorical sails).

    One of the best modern treatments of the field concept is a 1996 article by Scott Gilbert (a developmental biologist with his own textbook), John Opitz, and Rudolph Raff (a developmental biologist with a book that attempts to popularize evolutionary developmental biology called _The Shape of Life_) called "Resynthesizing evolutionary and developmental biology" appearing in the journal _Developmental Biology_ (173): 357-72.

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