This article intends to challenge the commonly admitted assumption that the Aristotelian treatment of emotions in his biology is teleologic. My proposal is that this sort of functional explanation of emotions in nature is rather to be found in Aquinas, Descartes, and especially in Darwinian and Neo-Darwinian theories of emotions. In section 2, I present the sorts of teleological explanations that Aristotle admits and uses in his biological writings. I section 3, I analyze Descartes' and especially Darwin's account of emotions and show that they fit the Aristotelian explanatory model presented in 2. Then, in section 4, I offer several arguments based on an analysis of Aristotles' biological treatises in order to show that this sort of teleological or functional explanation of emotions is not present in them. Instead, what we find in these writings are materialist explanations of the diverse characters and emotions of animal species. Finally, I suggest the idea, to be pursued further, that there is an asymmetry between the natural, non-teleologic treatment of emotions in Aristotle and the function he assigns to them from the point of view of practical rationality.