title: Evolutionarily stable disequilibrium: endless dynamics of evolution in a stationary population.
abstract: Evolution is often conceived as changes in the properties of a population over generations. Does this notion exhaust the possible dynamics of evolution? Life is hierarchically organized, and evolution can operate at multiple levels with conflicting tendencies. Using a minimal model of such conflicting multilevel evolution, we demonstrate the possibility of a novel mode of evolution that challenges the above notion: individuals ceaselessly modify their genetically inherited phenotype and fitness along their lines of descent, without involving apparent changes in the properties of the population. The model assumes a population of primitive cells (protocells, for short), each containing a population of replicating catalytic molecules. Protocells are selected towards maximizing the catalytic activity of internal molecules, whereas molecules tend to evolve towards minimizing it in order to maximize their relative fitness within a protocell. These conflicting evolutionary tendencies at different levels and genetic drift drive the lineages of protocells to oscillate endlessly between high and low intracellular catalytic activity, i.e. high and low fitness, along their lines of descent. This oscillation, however, occurs independently in different lineages, so that the population as a whole appears stationary. Therefore, ongoing evolution can be hidden behind an apparently stationary population owing to conflicting multilevel evolution.
authors.affiliation: Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan Theoretical Biology and Bioinformatics Group, Utrecht University, Utrecht, The Netherlands takeuchi@complex.c.u-tokyo.ac.jp.
authors.forename: Nobuto
authors.initials: N
authors.lastname: Takeuchi
authors.affiliation: Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Kaneko
authors.affiliation: Theoretical Biology and Bioinformatics Group, Utrecht University, Utrecht, The Netherlands.
authors.forename: Paulien
authors.initials: P
authors.lastname: Hogeweg
mesh_terms: D005075:Biological Evolution; D008954:Models, Biological; D011157:Population Dynamics
keywords: RNA world; intragenomic conflict; major evolutionary transition; multilevel selection; prebiotic evolution