Human sex is mysterious. We've never officially isolated a human pheremone, nor demonstrated that they can influence human behavior. We still don't know why external stimulation produces orgasms, or why some women can't orgasm from intercourse. And what's up with kissing? It's a practice demonstrated by some primates, but is it simply a meaningless courtship ritual?
A recent study may be able to give us a clue. Recent research conducted by Rafael Wlodarski, a DPhil student in the Department of Experimental Psychology at Oxford University, and Professor Robin Dunbar sought to find clues to the evolutionary rationale for kissing. Does it allow us to assess the genetic mojo of potential mates? Is it just a stimulating routine that preludes sex, or does it function to keep mates together longer?
Wlodarksi and Dunbar surveyed over 900 adults online about their kissing habits and its importance in their relationships. They found that women rated kissing as generally more important than men. Additionally, men and women who thought of themselves as attractive, or had more short-term relationships and casual sex, also thought kissing was more important.
On top of that, people in long-term relationships rated kissing as more important, and kissing frequency also correlated to relationship satisfaction. Good lovin', it turns out, does keep a home together.
The researchers are publishing their findings in two papers in two journals, Archives of Sexual Behavior and Human Nature. In the latter paper, Wlodarksi and Dunbar report that menstrual cycles also play a role in making out, as women tended to rate kissing as more important during the late-follicular phase, when they were more likely to conceive.
But what does all this mean? Mammalian females, and humans in particular, typically spend a long time gestating and then breastfeeding their offspring, and thus may be more selective in choosing mates. There's an evolutionary rationale to this, of course — you don't want to waste your time nursing poor-quality DNA, which is not useful to the longevity of the species. Previous research has suggested that women tend to be more selective than men in choosing partners, as do attractive people and people who engage in more casual sex (i.e. mate more). Because those groups correlate with the people who rate kissing as more important in the Oxford study, the researchers suggest that kissing is an important factor in "mate-assessment."
Translation: Locking lips might be evolution's way of helping you find the appropriate sex partner, and keep him or her around after the deed is done.