title: Multi-hit theory of the origin of life: problems of growth rate of protobionts and of speed of earliest evolution. I.
abstract: The previously proposed theory of biogenesis being a multi-hit process (due to random assemblage, within an aggregate of abiogenic nucleic acids (NAs) and proteins, of a set of functional molecules necessary for primitive life) is developed further taking into account speed of reactions and reproduction of protobionts, random distribution of functional molecules in protocell fission, and speed of earliest evolution. A hypothetical model of a protobiont being possibly ancestral to "our" life is designed. Probabilities of a multi-hit origin of such protobionts are estimated accounting not only for inclusion by chance of functional protein and NA molecules but also for exclusion of deleterious enzymes, and respecting the number of possible primitive codes. It is shown that "fluid organisms" are impossible and that individuation is a key structure of life. Life based on only NA (genobiosis) in contrast to life with genotype (NA) plus phenotype (protein) being infinitely evolvable (holobiosis), and life based on proteins alone are discussed. It is shown that protein + NA-life is in favour to those other life forms, and that the probability of origin of at least simple types of of holobiotic protobionts might be high enough for repeated biogeneses under early earth conditions. Though protobionts may have had generation times of 10(3) years speed of early evolution as well as stability of functional molecules could have been sufficient for allowing of evolution to reach the level of procaryots within the 10(8) to 10(9) years available.
mesh_terms: D005075:Biological Evolution; D008962:Models, Theoretical; D009696:Nucleic Acids; D000069497:Origin of Life; D011506:Proteins
chemical_list: D009696:Nucleic Acids; D011506:Proteins