In this paper we discuss about the utility of the species concept as real definition, particularly the Mayr concept. We propose a method for the logical separation of taxa based in the statements of the logical mathematics and the application of the sets theory to the concepts in systematic. We attempt to provide an objective methodology for the interpretation of natural groups in biology including the species as a basic group in evolution. We introduce the concept of the hypothetical ancestor as a mathematical possibility derived from the use of matrix calculations for non square matrix.
Keywords: species concept, mayr, hypothetical ancestor, non square matrix