I have to agree that happiness (and other emotions) have come to have a strong signaling component. I'm now even more interested than before about the mechanism by which it operates - just what triggers this emotion. I've also been thinking quite a bit about grief, which didn't fit as a pure feedback mechanism (otherwise you'd expect to have the same emotion for a person going away for life and that person dying), and your comments on that finally drove the point home.

I will need to consider all this further and revise my hypothesis. Thanks again for the insight!