The use of Markov chain models in studying the evolution of the proteins

In a recent paper Giulio & Caldararo (1987) used a Markov chain model to study the evolution of proteins. Unfortunately, their use of a first-order Markov chain model at the amino acid level is incorrect. The model has to be applied at the codon level [Jorre & Curnow (1975a)] followed by amalgamation of the codon states corresponding to each amino acid and of the three codons specifying termination. The model is correctly applied in this paper. The results obtained do not differ substantially from those obtained by Giulio & Caldararo (1987). The interpretation of the results as supporting the neutralist view of protein evolution is criticized.