There is disagreement in the literature about the exact nature of the phenomenon of empathy. There are emotional, cognitive, and conditioning views, applying in varying degrees across species. An adequate description of the ultimate and proximate mechanism can integrate these views. Proximately, the perception of an object's state activates the subject's corresponding representations, which in turn activate somatic and autonomic responses. This mechanism supports basic behaviors that are crucial for the reproductive success of animals living in groups. The Perception-Action Model, (...) together with an understanding of how representations change with experience, can explain the major empirical effects in the literature. It can also predict a variety of empathy disorders. The interaction between the PAM and prefrontal functioning can also explain different levels of empathy across species and age groups. This view can advance our evolutionary understanding of empathy beyond inclusive fitness and reciprocal altruism and can explain different levels of empathy across individuals, species, stages of development, and situations. Key Words: altruism; cognitive empathy ; comparative; emotion; emotional contagion; empathy ; evolution; human; perception-action; perspective taking. (shrink)