The answer to this question depends on your definition of kiss, says Sheena Harvey. Strictly speaking, you need to possess lips in order to kiss if you stick to the dictionary definition, which is a touch or caress to greet another person, express love or sexual desire.
But if you consider ‘kiss’ to refer to a physical demonstration of the desire to mate, to reinforce bonds and relate to family and pack members, then having two fleshy folds that surround the opening to your digestive system is not a primary requirement.
Do animals kiss?
By and large, mammals have lips of varying thicknesses and sensitivity. These are designed to give the animal the ability to grasp food items and communicate, both visually and with a variety of sounds, as the lips change shape. They are also used to feel, as they contain a huge number of nerve endings – in humans, lips are 100 times more sensitive than fingertips.
So all mammals could, theoretically, derive pleasure from using their lips to caress another of their species, but mostly they don’t. The reason for this is that a majority of mammals have a much more acute sense of smell than humans possess.
They can detect when a potential mate is receptive to them without needing to be given a physical affirmative. And they know when an approach is a friendly one by reading body language much better than we do.
Human perceptions and noses are quite crude by comparison, so we have to establish that our advances are welcome by the fact that we are allowed to touch lips or kiss cheeks.
Mammals also express kinship through vocalising, licking and grooming so they have no need of kissing. The only exception is our nearest relation in the primate world, the bonobo, that seems to use kissing in a way similar to ours, to offer comfort to another bonobo.
So far as other animal groups are concerned, some insects share food and communicate with each other by touching lipless mouths, but there is no evidence that emotion is involved.
Reptiles don’t have lips, either, so kissing is impossible, although they are known to nuzzle with their mouths and lick in an apparent show of ‘affection’. However, these are more likely to be submissive actions to a superior or a way of bonding with a mate or offspring.
Some fish do have a form of lips but they use them for foraging and cleaning off parasites rather than snogging. The so-called kissing gourami from southeast Asia does lock lips with other kissing gouramis but this is the opposite of affectionate behaviour. Their lips are lined with horny teeth and clamping them to another’s mouth is a form of ritual aggression, establishing dominance.