Jaak Panksepp's most excellent book was a stunningly thorough explication of a particular view of emotions---that they originate in evolutionarily ancient neural pathways which are profitably studied using animal models. The conclusion is immediate: animals such as dogs, cats, rats, and apes most likely do experience emotional states, and moreover homologous systems mediate human emotions.
The systems Panksepp details in fine neurochemical, neuroanatomical, and behavioral detail are SEEKING, RAGE, FEAR, LUST, CARE, PANIC, and PLAY, capitalized to distinguish the theoretical construct from the common use of these terms. Uniting experimental results from animal research with common psychopathologies, Panksepp self-consciously makes the necessary conceptual steps to paint a fascinating picture of the neurobiological basis of human affect.
Best read in a long time; very highly recommended. More here.