Oxytocin has long been known as a hormone for love. This is because this hormone has an effect on how social bonds are formed and retained. In a related study, scientists have uncovered that there’s a possibility that this same hormone might be directly linked to monogamy: http://www.medicalnewstoday.com/articles/269365.php
The study was done by a team of researchers from the Bonn University Medical Center in Germany. Noting that monogamy is not all that common in mammals, they considered humans as one of the rare exceptions to this rule. Using this inspiration, they made a research in the hopes of uncovering the forces that may cause monogamy.
With the help of researchers from both Germany and China, the Bonn University Medical Center research team led by Dr. Rene Hurlemann, made an experiment involving 40 heterosexual men who are in permanent relationships with their partners. They showed photos of their female partners, their female acquaintances, and of other women. As an additional parameter, they did this experiment using 2 parameters; one group was administered oxytocin via nasal spray and the other group was administered with a placebo.
The researchers observed that men who received oxytocin have their brain reward centers more active when viewing the photos of their partners. As such, they find them more attractive than others. They also observed that the effect of oxytocin is actually selective towards their partners. They concluded that love, more than just familiarity, triggered the “bonding effect” of oxytocin. Therefore, the researchers concluded that oxytocin production has a strong effect on strengthening attachment to the partners, and subsequently fostering monogamy.