A new study detailed in Hormones and Behavior explains a strong correlation between hormones, how hot your dude is, and how happy you are in your relationship. (Sorry, LGBT, this survey only focused on the heterosexual woman.) Simply put, if a lady thinks her man is a hunk, when she nears her period, she is happier and feels closer to him. On the other hand, if a girl generally acknowledges her main squeeze isn't exactly the pick of the litter, she becomes more critical and feels more distant as she ovulates.
Apparently, this all harkens back to evolution, when a woman paired with a less sexually satisfying mate might want to stray to more virile partners, in order to increase the likelihood of insemination. (Read: This means you can blame any cheating on evolution. Your wacky, uncontrollable lady hormones made you do it!)
While this makes sense — those who are sexually satisfied (i.e. with a partner whose genetic material is ideal for making babies) want to have babies with their partners. But the way in which science continues to be fascinated with how female ovulation makes us feel feelings has always felt a little problematic. Sure, PMS can actually have some very valid effects, but the experimentation and investigation of the link between our OUT-OF-CONTROL emotions and menstruation may be just a tad outdated. (LiveScience)