As for why they might fall in love faster, Marissa says women are evolutionarily more cautious—with good reason. "I think women unconsciously postpone love compared to men. Women have a lot more to lose reproductively by committing to the wrong man. They are born with a finite number of eggs, yet men produce millions of sperm on a daily basis."If women commit to and get pregnant by an unworthy mate [with] no help rearing a child, that would be very costly, time- and resource-wise."Ingrid Collins, a psychologist at the London Medical Centre, says male behavior showcases an aspect of nature that is also played out in the animal kingdom. "The male is usually the hunter and is more likely to be immediately stimulated. The woman is more focused on long-term stability because that's better for child-rearing."
Men are far more inclined to get fired up about a mate but also more likely to look around.
If that wasn't enough of a romance killer, "falling in love" quickly might also be a method of claiming territory, says Neil. "For males, the drive will be to secure a bond as quickly as possible and with less pressure of 'getting it right' the first time, compared to the potentially greater physical and emotional investment involved for women."As for the actual act of saying "I love you," Neil believes men tend to get there first because, once again, women are generally more risk-averse: "So [they] can be less likely to express such deeply felt emotions until they feel safe and secure enough in the relationship to do so. Revealing to your significant other that you love them risks vulnerability, because we can never be entirely sure they feel the same."Evolutionary essentialism aside, it could also be because men are just taught to be dominant. "You could argue that it's considered a 'male trait' to be assertive and to lead, and so this can be societal norms at play."However, just because a heterosexual man thinks he's in love, that doesn't guarantee the love is going to last for long. "In my experience as a therapist, men are far more inclined to get fired up about a mate but also more likely to look around more," Ingrid says.
While Marissa's research did not study whether heterosexual men fell out of love faster, she thinks they are more likely to move on from a relationship more quickly than their female partners. "For example, a man could have sex with five women at the same time and they might all become pregnant, whereas a woman could have sex with five men at the [same] time and she would only become pregnant by one man," she says.But she also stresses that this doesn't mean infidelity can—or should—be chalked up to survival instincts. "Today, if a man commits to a woman, and vice versa, one's modern frontal cortex should allow them to keep that commitment. That is, I am not saying evolved drives confer a license to infidelity or abandonment of one's partner."Translation: men can't excuse their cheating because of their drive for "species survival" or evolution because, well, men aren't actually cavemen anymore—their brains have evolved to control their urges.But, they're still more likely to say "I love you" first.