Self-replicability is the unique attribute observed in all the living
organisms and the question how the life was physically initiated could be
equivalent to the question how self-replicating informative polymers were
formed in the abiotic material world. It has been suggested that the present
DNA and proteins world was preceded by RNA world in which genetic information
of RNA molecules was replicated by the mutual catalytic function of RNA
molecules. However, the important question how the transition occurred from a
material world to the very early pre-RNA world remains unsolved experimentally
nor theoretically. We present an onset model of mutually catalytic
self-replicative systems formed in an assembly of polynucleotides. A
quantitative expression of the critical condition for the onset of growing
fluctuation towards self-replication in this model is obtained by analytical
and numerical calculations.Comment: 13 pages, 10 figures. Accepted for publication in Physical Review