Call me crazy, but I'm pretty sure from my understanding of human history and primate evolution that "long-term sexual/romantic partner" is, in fact, one of the basics.
Absolute one of the most basic cornerstones of psychology.
romantic? really?
I had an assumption that most of human history, marriage was more of an arranged marriage thing. With a lot of "women being treated as property", "heirs required for transfer of wealth", etc notation.
And there were also societies that were polyamorous in nature?
We are in a new world now, there is no need to force traditions (or worse yet, false traditions) that frankly doesn't seem to work anymore
At the individual level the pinnacle of happiness is teenage years and early adulthood.
Why wouldn't a rational individual not seek to prolong the behaviors in which one engaged during the pinnacle of happiness