Chemical reaction by science
Nonono, you're supposed to say "Baby don't hurt me"
Anyways, love in itself is nature's extra push to make us have love. Or, more so, stay near somebody to have love with. When you start getting an animal that's too intelligent to just run around raping each other, nature has to allow that being to have complex emotions like love. Love isn't as much of a way to increase reproduction drive, just to ensure that when the time comes, the opposite love will always be right at hand.
IMO, that is.
