EVENTS

STOQ 2009 – THE STOQ INTERNATIONAL CONFERENCE ON
«BIOLOGICAL EVOLUTION. Facts and Theories»

Abstracts of the Lectures:

Stuart A. Newman, New York Medical College in Valhalla, USA

"Pattern Language" for Evolution and Development of Animal Form

Ancient animals arose from unicellular organisms that had billions of years of genetic evolution behind them. In this talk I will consider the role played by a core set of "dynamical patterning modules" (DPMs) in the origination, development and evolution of multicellular animals, the Metazoa. These functional modules consist of the products of certain genes of the "developmental-genetic toolkit," in association with physical processes and effects characteristic of chemically and mechanically excitable systems of the "mesoscale" (i.e., linear dimension ~0.1-10 mm). Once cellular life achieved this spatial scale by the most basic DPM, cell-cell adhesion, a variety of physical forces and effects came into play, including cohesion, viscoelasticity, diffusion, spatiotemporal heterogeneity based on lateral inhibition, and global synchronization of oscillatory dynamics. I will show how toolkit gene products and pathways that pre-existed the Metazoa acquired novel morphogenetic functions simply by virtue of the change in scale and context inherent to multicellularity. I will show that DPMs, acting singly and in combination with each other, constitute a "pattern language" capable of generating all metazoan body plans and organ forms. Another implication is that the multicellular organisms of the late Precambrian-early Cambrian were phenotypically highly plastic, capable of fluently exploring morphospace in a fashion relatively decoupled from both function-based selection and genotypic change. The stable developmental trajectories ("developmental programs") and morphological phenotypes of modern organisms would then have arisen by stabilizing selection that routinized the generation of morphological motifs that were originally manifestations of the physical properties of multicellular aggregates.

This perspective provides a resolution of the apparent "molecular homology-analogy paradox," whereby widely divergent modern animal types utilize the same molecular toolkit during development. It does so however, by inverting the neo-Darwinian tenet that phenotypic disparity was generated over long periods of time in concert with, and in proportion to, genotypic change.