Ever notice a time you were hanging out with your boyfriend or a girlfriend was hanging out with her guy and in an instant he transformed from a normal dude to a super-macho lunkhead after other attractive guys came close–for instance, he tried to out-drink the other men, he began bragging big-time about his motorcycle or high school sports record, or he suddenly dropped to the floor and did 20 push-ups…10 with one hand?
A new study pinpoints a possible reason for this unusual transition: Ovulation.
Reporting in the journal Hormones and Behavior, UCLA researchers discovered that when a woman is ovulating and guys come close who her male partner perceives as possible competition, he experiences a surge in testosterone–a hormone that amps up assertiveness, aggression and competitiveness.
Men likely evolved to pump up their dominance around other men during a woman’s most fertile time of the month to help keep other potential suitors when pregnancy is a possibility.
And, frankly, this was probably a wise move on Mother Nature’s part since other research shows women are far more likely to fantasize about other partners, flirt with other cuties and even stray during their ovulatory phase than at any other point in their cycle.
This study also had a bit of good news for lads who fly under the radar: If your guy doesn’t perceive another man as a romantic rival–for instance, because of his age or appearance–his testosterone level remains unchanged. So, your partner will remain his friendly self even as you exchange flirty glances with the new guy!