According to this research, birds experience an emotional response to bird song in a manner akin to how humans emotionally experience music. If a female bird is primed with estrogen to simulate a breeding state, the same region of her brain is activated as is in humans listening to pleasant music. And if a male bird is primed with testosterone and exposed to the song of another male bird, the emotional region of its brain concerned with danger is activated, just as the human brain is activated when exposed to scary music.
In the mainstream way of thinking of evolution, this can be interpreted as emotion having evolved in service to the mandates of reproduction and survival. But there is a more logical interpretation given the fact that people are having these same emotional responses to music independent of their breeding status and in the absence of a life-threatening situation. Why assume therefore that these emotional responses are first and foremost in service to reproduction and survival? It's more logical that while emotion does indeed solve the problems of reproduction and survival, its fundamental function is to create a universal medium for the communication of information, a code of conduct by which emotion can be exchanged and emotional bonds created across species lines. In this interpretation we find that emotion is characterized by two basic "poles," the preyful polarity, as in hearing that lonesome whistle blow as a train recedes into the distance as when a movie wants to evoke a romantic state of yearning (sound waves elongating), and then the predatory pole as when the train suddenly rushes from a tunnel right at the movie watcher pinned in their seat (sound waves compressing). In this interpretation we find that emotion moves in a specific direction, as does all energy in nature, from a place or pole of high density, to a pole of lesser density. And because emotion has discrete thermodynamic properties, this means that pressure, and release from pressure, can serve as a universal form of communication that can allow any two beings, no matter their genetic makeup, to connect and bond, while simultaneously equipping them with a means of navigating the world so as to avoid predators, seek nourishment and pick a mate. The most logical interpretation of this evidence is that the fundamental function of emotion is as a universal medium that enables networking.