There is an inextricable connection between science and emotions. The main theory that scientists have according to researches in oxford (see me for link) is that, humans tend to want to serve their primary function, which is the perpetuation of the species, basically the biological function. The connection with this and emotions is often hard to find, as many emotions can be illogical and irrational. Sometimes what is most logical for one to do, when serving their function, does not occur. Thus the subject pursues the illogical pattern, due to love or other feelings rather than following a more logical and rational pattern. Often this is the females, as they tend to be far more irrational at times compared to their counter-part according to oxford researches.
Emotions have scientifically been determined as impulses in the body that mimic thoughts or are believed the mimic thoughts, to the persons perspective of what emotions are.
Although this view has been subject to much controversy because the question is raised whether or not one can feel emotions, where no impulses are present. For example what if they cannot feel butterflies in their stomach? The fact is that people who generally appear to be incapable of feeling, can actually become depressed due to loneliness, but they are also capable of expressing love according to their ablity to do so. There is an extremely large capacity for the human body to express love and other emotions, to an extent where scientists are incpable of thinking it could happen but yet it does. This goes to show the lack of understanding science has over the ability of the human potential to express emotions.
Good question by the way but it is very difficult to explain i hope that helped a bit.