Re: Morphogenetic fields

From: Dace (
Date: Thu 12 Jun 2003 - 21:42:43 GMT

  • Next message: "Re: Morphogenetic fields"

    > From: Keith Henson <>
    > At 05:51 PM 10/06/03 -0700, Dace wrote:
    > ><Keith>
    > >
    > > > "Until recently, the interactions that constituted these fields could
    > >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
    > *way* back, to the common ancestor.

    Okay, if it's genes, then how is it that the same genes provide
    "instructions" for animals that in no way resemble each other beyond the most basic structure? What about all the things that distinguish us from insects, for example? Where does all that come from if the determinative
    (homeobox) genes are the same?

    You should be aware that nobody, not even Nobel Prize-winning biochemists, has been able to answer this question.

    > > > "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
    > > > from a single cell. That the same mechanism (hox genes) lays out the
    > > > developmental axis only indicates animals with bilateral symmetry had
    > > > 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).

    Indeed, it appears that no amount of reasoning can get past your memetic interference on this mater. This illustrates the importance of the distinction between standard ideas, which proliferate on the basis of their agreement with human reason, versus memetic ideas, which proliferate on the basis of their own momentum. In the case of standard ideas, it's humans who determine which ones succeed and which ones fail. This is what science is all about (at least in theory). In the case of memes, success depends on their ability to exploit our needs. Most of them are perfectly benign but a few become ingrained despite their malignancy. In the current example, the malignant meme is the equation of life with machine; autonomous with automatic. It's no surprise, then, that you link human with automaton, and why it makes no sense to you to distinguish between ideas we determine and ideas that determine us.

    What you're missing is the human dimension. For example, plenty of people have recognized that the state policies of Israel toward its Palestinian minority are criminal. To be anti-Israel, in this limited sense, results from subjecting beliefs to our innate capacity for reason. But some people criticize Israel, not out of reason, but out of a racist hatred of Jews. These are people who equate all Jews with Israel, though many Jews, even Israeli citizens, are appalled at the brutality of their government and their fellow citizens. The principled anti-Isreali stance is a result of human intelligence, not memetic struggle. The unprincipled anti-Israeli stance results from the success of the anti-Jew meme. Another unprincipled stance, which is pro-Isreali, depends on the success of the meme that equates all criticism of Israel with "anti-Semitism" (the irony being that Arabs are themselves Semitic).

    > From: Keith Henson <>
    > At 12:32 AM 11/06/03 -0400, Scott wrote:
    > snip
    > >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.
    > Thanks. I was looking for this:
    > (in the context of eyes which apparently evolved before the common
    > But it obviously doesn't happen that
    > often, and I ask him where his passion for
    > taxonomy and evolution came from. It
    > began, really, in 1994, he says. He
    > published a scientific correspondence in
    > Nature providing new evidence to shore
    > up an old idea, one that had surfaced in
    > the nineteenth century. Observations of
    > the bodies of many different species
    > suggested that at some point in evolution,
    > torsos had gotten turned around, that
    > insects' bellies became vertebrates' backs.
    > This could finally be substantiated
    > through genetic evidence, he discovered.
    > The genes that form the front of a wide
    > range of species are related to those that
    > form the backs of others, and vice versa.
    > "From then on I was hooked," he says.
    > Right on the segments business, and vertebrate ribs correspond to insect
    > legs in the Hox genes that code for them. Because the genes that set up
    > the gradients are on a row down the chromosome, swapping them around
    > is known to happen) will reverse the front to back gradients.

    The fact that the vastly different morphologies of insects and vertebrates depend on the same underlying structure is so baffling that, according to Enrico Coen, only cellular creativity can account for embryonic development. In *The Art of Genes* he uses the metaphor of painting a picture to illustrate development. What genes provide is akin to color schemes. What proteins provide is the canvas. Due its innate capacity for creativity, the cell elaborates on this simple color scheme, which is universal to animals despite their obvious morphological differences. It's the creativity innate to cells that enables those of a rabbit to build a rabbit while those of a turtle, starting from the same color scheme, build a turtle.

    Now, Coen is a respected theorist at the Genetics Department of the John Innes Centre, Norwich. He probably knows a little more about this than you'll learn tooling around Google, and yet he felt it necessary to concoct a seemingly bizarre theory about cellular creativity to explain the capacity of the same set of developmental genes to produce wildly different creatures.

    What Coen is missing from his theory is the factor that guides the creative function of cells. How do rabbit cells know to produce rabbits and not turtles? If they're so "creative," why don't they do something wacky once in awhile? Clearly, something is shaping their innate creativity toward a certain end-point, and this end-point is established by the memory inherent to living matter. Rabbits develop as they do because that's how their ancestors developed.

    > From: "Scott Chase" <>
    > 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
    > 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).

    Your use of the term "simplistic reductionism" demonstrates a serious lack of understanding. Reductionism, by definition, is a simplification. Complex living systems are reduced to particulate elements. What you're looking for is a reductionism that doesn't really reduce to anything but somehow remains true to its complex subject-matter.

    The question is whether organic form is determined holistically or mechanistically. There's no in-between, any more than there's a state halfway between alive and dead. You need to figure out which side you're on and stick with it.

    I don't mean to imply by this that organisms don't involve mechanisms. They certainly do, but what determines their characteristic forms is holistic, much like the holistic field of a compass magnet determining whether it points north or south.

    With or without the field concept, contemporary research is headed in the holistic direction, as demonstrated by the Scientific American article by Gibbs in August, 2001. We may regard the following quote from that article as an epitaph to mechanistic biology:

    "I could draw you a map of all the components of a cell and put all the proper arrows connecting them," says Alfred G. Gilman, a Nobel Prize-winning biochemist at the University of Texas Southwestern Medical Center at Dallas. But for even the simplest single-celled microorganism, "I or anybody else would look at that map and have absolutely no ability to predict anything."

    You can see why they're talking about "grand-scale Kuhnian revolution." You were the one, Scott, who complained about Robert Aunger being oblivious to basic facts of genetics. Memetics will get nowhere if it's out of touch with the reality of biological theory and research. Instead of helping this discussion along, you've caved in to peer pressure. One of the profound implications of memetics is that just because "everyone" believes something doesn't make it true. Sometimes monolithic agreement among people merely indicates their infection by the same virulent meme. This is especially apt when "everyone" does not necessarily include professionals in the field.

    > One of the best modern treatments of the field concept is a 1996 article
    > Scott Gilbert (a developmental biologist with his own textbook), John
    > 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
    > the journal _Developmental Biology_ (173): 357-72.

    I look forward to reading this. I was a bit disappointed by how little material in Gilbert's development textbook concerned field theory (though he does mention Weiss' "limb field"). Gilbert claims that genes are regulated by "morphogenic determinants." If these, in turn, are determined by genes, then we have a circular argument. Otherwise, it's just another term for morphogenetic fields.


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