Considerations of Stability in Models of Primitive Life: Effect of Errors and Error Propagation
Models of simple self-replicating systems that represent a primitive form of life are investigated with the main aim of finding conditions for the occurrence of stable, self-sustained states. Such conditions are provided by requirements for ‘food molecules’, i.e. activated monomers, which build up the self-replicating polymers. For this, kinetic equations are used that explicitly contain both growth and degradation terms of all substances including the food molecules which are assumed to be created by some energy-driven process. The conditions for self-sustained states are essentially that the concentration of the food molecules must be large enough to allow growth of the polymers. In particular, we are interested in how these conditions change with the length of the polymers, with the complexity of the system and with the accuracy of the synthesis. For a system of independent self-replicating units, there do not seem to be any severe obstacles in reaching a stable state with errors taken into account even in a primitive system, provided the polymers are not too long. In such systems, a description of molecular evolution is relatively straightforward. On the other hand, in a system with cooperative units, the situation is more complex. A particular situation is studied with polymers built up by an adaptor (tRNA or a precursor of that). Here errors and the occurrence of error propagation are important features that should be properly understood in a description of the first cooperating forms of life.
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