A Quantitative Evaluation of the Iron-Sulfur World and Its Relevance to Life's Origins

Abstract

The significance of Wächtershäuser's iron-sulfur world to the origin of life and the limits to its notional autocatalytic cycles are examined in kinetic simulations of the chain polymerization sequence: primitive materials-->amino acids-->oligomers. The simulations were run for the formation of all oligomers up to the 20-mer over a 1 Gy interval from the end of the period of heavy bombardment, during which period life emerged. Upper-limit rate constant estimates developed from the studies of Huber and Wächtershäuser were employed. The simulations showed that oligomer production consistent with life's start within that interval emerges only with an autocatalyst exhibiting a catalytic proficiency comparable to that of contemporary enzymes. The simulations, moreover, ignored likely thermodynamic and statistical burdens which, if included, would have led to the need for catalytic capacities well in excess of those in present-day enzymes. Prebiotic oligomers with such levels of activity are clearly not likely, and it is apparent that the iron-sulfur scheme could not have played a role in life's beginnings.