Kissing is used to assess a partner and find a suitable husband or wife, according to a recent study.
According to the study, kissing is also instrumental in bringing about feelings of attachment in a couple and to speed up sexual arousal.
A survey of over 900 men and women found that women place more value on kissing in relationships than men and especially value the first kiss.
"Kissing serves the function full mate assessment," the authors of the study said with women placing more importance on the activity than men.
Speaking to the Independent, one of the authors, Professor Dunbar, said mate choice and courtship in humans is complex and it involves a series of periods of assessments where people ask themselves 'shall I carry on deeper into this relationship?'
He added that while the initial attraction may include facial, body and social cues, the assessments become more and more intimate people go deeper into courtship, and this is where kissing comes in.
The study published in the Archives of Sexual Behaviour journal found that men thought kissing was more important in established relationships.
According to the study, how often a couple kissed showed their satisfaction in the relationship.
The study concluded that - contrary to popular belief - the primary function of kissing is not sexual arousal.
In a past article, psychologist Chris Hart wrote: "... if that first kiss was magic, chances are your subconscious has decided you’re going to be OK together. So don’t put off the moment! Especially until after your wedding, as a few people argue you should. Because it you don’t find your partner’s kisses irresistible, chances are you’ll never be completely happy together. And that’s something you should know as soon as possible – certainly long before you contemplate getting married."