A group of intrepid (and, ironically, male) scientists have set out to figure out why the hell women get PMS, and they think it's to test our boyfriends.
Research from McQuarie University in Australia says that couples that are not a good genetic match are more likely to break up when stress—or raging bitchiness—is put on the relationship. The researchers write that "animosity exhibited during PMS is preferentially directed at current partners."
So no need to apologize to your partner for calling him a dick because he didn't pick up his phone when you were trying to call him while you're on your period. If he's sweetly understanding about your PMS, it's just proof that nature wants you guys to be together.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.