For a long time, historians thought that romantic love (as we understand it, in a Hallmark Valentine's kind of way) was a Western invention, constructed by the romantic troubadours in French courts of the thirteenth century (see this piece by Catherine Winter).
Recent years, and the rise of brain scanning technologies and evolutionary psychology, have seen the conventional wisdom shift. Most explanations of romantic love these days focus on serotonin and dopamine levels, blood flow and MRIs; and these biological mechanisms are postulated to have emerged early in human history to promote pair bonding and care of our especially helpless young.
But it does not have to be either social construction or evolutionary mandate. Social and psychological triggers can flip the switch on chemical processes in our brains. This is the argument I make on a new PRI show titled The Really Big Questions, hosted by Dean Olsher. My bit starts at 38:00 into the episode.
In previous posts I have argued that wellbeing requires a lot of not always pleasurable work. Fulfillment is distinct from giddy happiness; and it derives from the hard work of becoming the sort of person you want to be. Likewise, as I claim in the Love episode of The Really Big Question, more than biochemical, and it requires a lot of hard work.