Shhhh. There is this mythic creature called love or romance. People think they thought it up themselves. They don’t like to think that there’s something in the background pulling all the strings.
Well, not all the strings. More like we have built in potentials for all kinds of things, and depending on our environment, various emotions are triggered. We experience them as volitional. The idea that our emotions are some kind of chemistry that determines our thoughts and actions is pretty horrifying.
I think there is some element of volition in this, but it’s a lot less than we’d like to believe. So, yeah, humans have a lot of programs built in, and some of them have to do with reproduction and raising of offspring. It seems love helps with this, and so folks who could love have been selected through the evolutionary process. People who didn’t love very well just didn’t make it.
Where chemistry leaves off and volition takes over—I can’t tell you. All I know is they both play a role.