The Nature of Emotions
From the Buddhist perspective emotions arise due to attraction and rejection. We are attracted to that which we need in order that our entity and the present identity/self-reference can survive and we reject anything, which seems to threaten the continuity of this identity/self-reference. This applies to everything, which has come into dual and samsaric existence.
The vast spectrum of emotions and feelings evolve and arise solely on the basis of our individual identities/self-references and it is only at the point of higher evolutionary development like ours this instinct for survival may develop into emotions.