The act of kissing, a human behavior that feels so natural yet seemingly defies explanation, may be a bit strange if you think about it. Why do we put our mouths together and consider it loving and even romantic cross-culturally? Researchers from Oxford University may have some clues on why a smooch is so important in the process of human male selection, BBC News reports.

From data collected in an online survey of 900 adults, researchers discovered that kissing may be a way to assess the "value" of a potential partner, a behavior that has evolutionary roots, as our distant chimp and bonobo cousins are known to partake in the occasional smooch.

Men and women surveyed who placed a higher value on kissing tended to be more attractive, have more frequent casual sex partners and be pickier in choosing their long-term mate, suggesting that kissing helps humans "size up" a potential partner.

"Initial attraction may include facial, body and social cues. Then assessments become more and more intimate as we go deeper into the courtship stages, and this is where kissing comes in," Robin Dunbar, a professor from the department of experimental psychology at Oxford University, told BBC News of the complex rituals in human courtship.

"In choosing partners, we have to deal with the 'Jane Austen problem': How long do you wait for Mr Darcy to come along when you can't wait forever and there may be lots of you waiting just for him? At what point do you have to compromise for the curate?"

Researchers concluded that kissing many different people may be quite helpful in choosing the right person.

Kissing allows us to get closer while scrutinizing our partner, not only playing a key role in the process of developing romantic attachment and affection, but also allowing us to quite literally "sniff" and "feel out" our mates first-hand. Pheromones and chemical signals are transmitted during an intimate kiss, and release the calming hormone oxytocin when we are feeling close and comfortable with someone.

As for how we developed the practice of kissing, the current dominant theory suggests that it evolved from mothers passing along chewed food to their babies via the mouth, making lip-to-lip contact essential for survival and an integral part of social bonding.

The latest study has been published in the journal Archives of Sexual Behaviour.

*This article has been updated to note a few changes.