Sunday, February 26, 2006


Epigenetic Mechanisms of Character Origination

[Newman & Muller/Müller, J. Experimental Zoology, '00]


"The close mapping between genotype and morphological phenotype in
many contemporary metazoans has led to the general notion that the
evolution of organismal form is a direct consequence of evolving
genetic programs. In contrast to this view, we propose that the
present relationship between genes and form is a highly derived
condition, a product of evolution rather than its precondition.
Prior to the biochemical canalization of developmental pathways, and
the stabilization of phenotypes, interaction of multicellular
organisms with their physico-chemical environments dictated a many-to-
many mapping between genomes and forms. These forms would have been
generated by epigenetic mechanisms: initially physical processes
characteristic of condensed, chemically active materials, and later
conditional, inductive interactions among the organism's constituent
tissues. This concept, that epigenetic mechanisms are the generative
agents of morphological character origination, helps to explain
findings that are difficult to reconcile with the standard neo-
Darwinian model, e.g. the burst of body plans in the early Cambrian,
the origins of morphological innovation, homology, and rapid change
of form. Our concept entails a new interpretation of the relationship
between genes and biological form."

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