  A method based on mapping a symbolic sequence into a set of patterns (strings
resulting from the sequence parsing) is proposed as a tool for the
reconstruction of ancestral sequences. The set union of patterns comprises all
the patterns present in the family of related proteins sequences of an extant
species. The set of most frequent patterns among protein sequences is selected
and concatenated. The resulting sequence of amino acids is supposed to be the
ancestral protein of the family. No sequences alignment and phylogenetic tree
of the species family are necessary. The method is used for inferring the
ancestral amino acid sequences of thirteen mitochondria-encoded protein
families of mammal species. Statistical distribution of the similarity between
extant and ancestral sequences exhibits some structures related to
environmental changes in the past.
