I don't think it came from any philosophical enigma or from certain bodily reactions (though both may add to it), but I think love transcends all of this.
It's not something you can define, not something you can control, nor discover its origin. It's apart of us. We're born and built to love, though many people turn away from deep passionate love that we're all capable of.
Sure, go ahead..tear that up, but at the end of the day, love is probably the only thing that matters. It's what makes us do what we do and makes us who we are, in a sense.
It's far greater than I can put it, and in my opinion, it's pretty lame to try to pinpoint the epicenter in concrete terms..it's so much greater..practically a mystery to us, though we're filled with it.
Is it that by its indefiniteness it shadows forth the heartless voids and immensities of the universe, and thus stabs us from behind with the thought of annihilation, when beholding the white depths of the milky way?
... You know how they derive statements as in "what you love destroys you, etc" or in life "you hate the people you love, etc".
What I'm saying is, those are just a petty excuses - when a person starts to love someone or something, it's a sign that he/she is being negligent of a particular belief/value system, or duty. Therefore (presumably), he/she is already in that state of negligence, which can be used as an excuse to 'self-destruct' having not gone higher for a purpose, or something. To sum it up, love is and always will be something 'personal' to a person - not going beyond a universal meaning for it, and it can neither be subjected as being 'innocent' nor 'guilty'... it's entirely how the individual 'sees' it.
... And that can happen at any time, has no particular 'origin' because as we've come to know - we are (naturally) quite selfish and arrogant creatures. Should love exist, I'd think it would exist in the context that I've given - it's around being self-centered.