Abstract In contradistinction to the suggestion that peptide synthesis occurring nonenzymically on the primitive Earth would be a totally random event, evidence is presented that the interaction of any one given amino acid with another follows well-defined statistics based on the relative reactivity of each amino acid. The effects of environment, pH, side chain, and the characteristics of the portion of the polymer already produced were studied. The results lead to the conclusion that, based on the relative reactivities of the amino acids, a population of polypeptides of specific sequences could have been abiotically produced without the involvement of nucleic acids. The relevance of this observation to prebiotic chemical evolution is discussed.