O estatuto ontológico das espécies biológicas na sistemática filogenética

Abstract

One of the most discussed issues in contemporary Philosophy of Biology concerns the ontological status of biological species. By its means, philosophers and biologists want to summarize, in very general terms, the type of organization that certain biological theories prescribe to species. We can say that the most widespread theory about it says that species are natural kinds. This thesis gained much popularity with the work of Hilary Putnam (1975) and Saul Kripke (1980) at around the same time that, interestingly, it was facing resistance from some philosophers of biology. These, in particular Willi Hennig (1966), Michael Ghiselin (1974), and David Hull (1976), proposed the alternate theory that species are individuals. Our dissertation assesses whether species are natural kinds or individuals in the specific context of Phylogenetic Systematics, a biological classification methodology that was developed by Willi Hennig himself and is widely used today by the scientific community. Although Hennig has argued that species are individuals, he did not offer a systematic and philosophically clear account of the association between this thesis and his classification methodology. The defense and explanation for this relationship become necessary, especially since the thesis that species are natural kinds has been refined in recent decades, and with it, new criticism of the thesis that species are individuals have emerged. That said, our dissertation (i) explains the commitment of Phylogenetic Systematics to the thesis that species are individuals from the philosophical discussion about the identity criteria, (ii) refuses the recent attempt to characterize species through a new theory of natural kinds, namely, the theory of homeostatic property clusters (Boyd, 1999), (iii) assesses the problems associated with the thesis that species are individuals, in particular the concept of "cohesion" that is attached to it, suggesting a response pathway to these problems that is dependent on the use that scientists make of concepts such as "individual", "cohesion" and "species". Although the thesis called "species-as-individuals" is not free of problems, it remains the best alternative to be adopted. Moreover, their problems are instructive of how the debate about the ontological status of species can reap better fruits as it gets closer to scientific practice.