The concept of species and the foundations of biology, a case study: the Callithrix jacchus group (Primates-Platyrrhini).

The axiomatic theory presented in Galleni and Forti [1999], being part of the foundational programme of Ennio De Giorgi, is based on the fundamental notions of quality, relation, operation and collection, and provides a very general axiomatization of the biological notions of living object, generation, species and speciation. Within this theoretical framework we consider here a difficult case of classification of species: the Callithrix jacchus group of the New World monkeys. Although the morphological analysis strongly suggests the individuation of six different species, nevertheless several experiments of crossing give evidence to fertility of hybrids. Since both the morphological and the hybridological criteria have shown to be of enormous importance in actual classification of species, this apparent contradiction seems very disappointing. Our axiomatization of speciation processes as operations acting in special time intervals permits to avoid the contradiction by allowing for individuals which, during such special periods, may belong to more than one species. Therefore we assume that one or more speciation processes are developing, starting from a unique protospecies and differentiating in six new ones. In order to obtain more evidence of these processes, new observations and suitable experiments are needed.