Meeting Abstract

P3.29A  Saturday, Jan. 5  A Cell-Cell Signaling Model for Metazoan Evolution TORDAY, John/S*; REHAN, Virender/K; UCLA; UCLA jtorday@labiomed.org

Natural Selection continues to be viewed retrospectively as descriptive analyses of phenotypes and genotypes, reasoning after the fact. If we think of life as an �arrow of time� moving in space from left to right, we must think about evolution progressing from left to right as well. Darwinism postdicts phylogeny- how can we perceive evolution in the forward direction, emulating how life evolved from unicellular organisms to metazoans? The advent of evolutionary-developmental biology and the effective application of molecular biology to decipher both phylogeny and ontogeny have helped to initiate this 180o turn- we know a lot about the cell-molecular mechanisms of embryogenesis from one to many cells; how genes determine structure and function, which can be used as an experimental basis for testing Natural Selection for gene regulatory networks (GRNs) that determine phylogenetic phenotypes. Exploitation of developmental models to test phylogenetic hypotheses will allow us to challenge evolutionary theory in Real Time. One set of molecular mechanisms common to both development and phylogeny are the cellular ligand-receptor interactions that mediate growth,differentiation,homeostasis and aging (Torday and Rehan 2007). These mechanisms are plastic,mediating the on-going interactions between the organism and its environment that are the core of evolution. Such a �middle out� strategy is superior to either a �top-down� or �bottom-up� approach to understanding evolution because it is based on what likely was and is the driving force for evolution, and does not require any a priori or a posteriori assumptions. This cell-cell signaling model for evolution could empirically resolve such paradoxes as canalization v novelty, reproduction v isolation, punctuated equilibrium v gradualism.