Apart from some rear-guard behaviorists, few people hesitate to ascribe empathy to their dogs. But then dogs are man's best friend, freely credited with lots of human sentiments. For as much as we empathize with our canines, we have been stingy about recognizing empathy elsewhere in the animal kingdom, reserving it as a human trait. This belief is changing, however, as a growing line of research demonstrates not just empathy's existence in other animals but its subtleties and exceptions as well. And they shed some interesting light on how we developed our capacity for caring for others.