Sunday, February 05, 2006


Re: [evomech] The control of body size in insects (Dev Biol)

On 05/02/2006 Cliff Lundberg wrote:
> No doubt a lot of details are being learned about ontogeny
> and its regulation, but something's lacking in the general
> concept,
> namely, what it is that is being regulated.

I feel some consideration should also be given to exactly 'what' is doing the regulating! For example, in the press release from:

Researchers evolve a complex genetic trait in the laboratory

Nijhout is quoted as saying "...'It's long been known that polyphenisms are controlled by hormones, with the brain sensing environmental signals and altering the pattern of hormonal secretions,' said Nijhout. 'In turn, these hormonal patterns turn sets of genes on or off to produce different traits. However, we understood only the developmental mechanism, and how it is possible with a single genome in an animal to produce two very different phenotypes,' he said..."

Which part of the brain? its nature, characteristics? OMG - now I'll have to look up 'regulatory hierarchies' or something.. :)


What's being regulated
> is the expression of a primordial form, a form that has many
> parts, any of which may or may not be expressed. A form that's the
> basis for an arthropod, or a vertebrate, or some other segmented
> animal. Only something like this fits with those complex and
> characteristic types emerging gradually in development, yet
> suddenly in the fossil record. The basic forms are real,
> yet archetypal, and their origins as trains of identical segments
> were rapid processes of duplication. In a context where all
> changes are reductions and distortions, the progenitor is
> an archetype, underlying and explaining anatomy.
> Cliff

Model of an Internal Evolutionary Mechanism (based on an extension to homeostasis) linking Adaptive Mutations to the Baldwin Effect:

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