A new study from researchers at Oxford University suggests kissing helps us evaluate potential partners and keep them around once in a relationship.

“Kissing in human sexual relationships is incredibly prevalent in various forms across just about every society and culture,” says Rafael Wlodarski, the student who conducted the research in the Department of Experimental Psychology at Oxford University. “Kissing is seen in our closest primate relatives, chimps and bonobos, but it is much less intense and less commonly used.”

“So here’s a human courtship behavior which is incredibly widespread and common and, in extent, is quite unique. And we are still not exactly sure why it is so widespread or what purpose it serves.”

Wlodarski and Professor Robin Dunbar set up an online questionnaire that over 900 adults answered. It contained questions about the importance of kissing in both short and long term relationships.

Wlodarski explains, “There are three main theories about the role that kissing plays in sexual relationships: that it somehow helps assess the genetic quality of potential mates; that it is used to increase arousal and that it is useful in keeping relationships together. We wanted to see which of these theories held up under closer scrutiny.”

The survey responses showed that women rated kissing as generally more important in relationships than men. Men and women who rated themselves as attractive or tended to have more short term relationships and casual encounters also rated kissing as being more important.

In humans, just like all mammals, females invest more time than males in having offspring. Previous studies have shown that women tend to be more selective when choosing a partner initially. Men and women who are more attractive or have more casual sex partners also tend to be more selective in choosing potential mates as well. The specific groups that valued kissing more in their survey responses suggest that kissing helps in assessing potential mates.

It has been suggested previously that kissing may allow people to subconsciously assess a potential partner through taste or smell by allowing them to pick up on biological cues for compatibility, genetic fitness or general health.

Researchers reported their findings in two different papers, the journal Archives of Sexual Behavior and the journal Human Nature.