Love is a bonding mechanism. It's a collection of irrational feelings that incline one to behave in ways that maintains a relationship to someone. This might manifest positively or negatively, since that could mean doing something like taking care of a person to keep them around, or attempting to possess them by force (as examples among many).
Since it seems to be in every culture in the world, and it is indeed a detectable biological phenomenon, I'm guessing it was evolved. Most of the time it doesn't last too long though. The most reasonable guess is that it would fascilitate serial monogamy.
Is it a universal truth? I don't even know what that means. Whatever it could mean I'm almost certainly guessing it's not. I also don't care. While love does compel people to do some crazy crap sometimes, I generally think it's nice due to its impact and more of it would be better. So, from a pragmatic perspective, it's worth believing in.
Althought I have some specifics about how I think love should work. I do not believe in unconditional love. I do not believe in discriminatory love. And so on.
I don't know if I've ever seen another thread title on this forum that screamed "HIPPIE!" as much as this one.