The general inorganic nature of traditional selection theory (based on differential growth between any two systems) is pointed out, wherefrom it follows that this theory cannot provide explanations for the characteristics of organic evolution. Specific biophysical aspects enter with the complexity of macro-molecules: vital physical conditions for the perpetuation of the system, irrevocable extinction (= death) and random change leading to novelty, are the result of complexity per se. Further biophysical properties are a direct function of the pathway along which (...) random mutation in nucleic acids is converted into continuous protein — (specifically enzyme) — function, from there into organismic phenotype with fitness components which may, or may not, correspond to identifiable structural units in DNA. The general machine-like properties of enzymes, in that there is no additive relationship between structural (amino acid) composition and functional output, is discussed in more detail. The continuous growth functions of molecular concentrations, directed by enzyme turnover, determine simple laws of growth and morphogenesis in the organic hierarchy and thus of phenotype. Thus, the combined effect of DNA-structure and of environmental parameters (temperature, pressure, pH, etc.) on protein function determines ultimately the actual phenotype and hence, quality and intensity of genotypic selection. (shrink)

The dynamics of populations of self-replicating, hierarchically structured individuals, exposedto accidents which destroy their sub-units, is analyzed mathematically, specifically with regardto the roles of redundancy and sexual repair. The following points emerge from this analysis:0 A population of individuals with redundant sub-structure has no intrinsic steady-statepoint; it tends to either zero or infinity depending on a critical accident rate α c . Increased redundancy renders populations less accident prone initially, but populationdecline is steeper if a is greater than a fixed (...) value α d . Periodic, sexual repair at system-specific intervals prevents continuous decline and stabilizesthe population insofar as it will now oscillate between two fixed population levels. The stabilizing sexual interval increases with increased complexity provided this is accom-panied by appropriate levels of redundancy. The model closely simulates the dynamics of heterosis effects. Repair fitness is a population fitness: the chance of an individual being repaired is a functionof the statistical make-up of the population as a whole at that particular period. Populationsliving at α > α c either engage in sexual repair at the appropriate time or they die out. The mathematical properties of the model illustrate mechanisms which possibly played arole in the evolution of a mortal soma in relation to sexual reproduction. (shrink)