Rats! Turns out a kiss is just a kiss
Research answers Victor ‘How did it happen that Hugo’s 19th century question their lips came together?’
THE ultimate romantic expression started out as a primitive, chemical form of communication between rat-like ancestors of humans, according to Roger Highfield, Daily Telegraph Science Editor.
A kiss is more than just a kiss. Kissing is a symbol of romance, love and affection. A polite peck is an accepted greeting between friends and family. A hungry snog a symbol of base desire. In the Bible, a sly smacker is even a symbol of betrayal.
Now the resources of science are being applied to shed new light on this most powerful gesture.
The question of ‘‘what’s in a kiss’’ has taxed lovers, poets and scientists throughout the ages.
Dr Henry Gibbons defined it as: ‘‘The anatomical juxtaposition of two orbicularis oris muscles in a state of contraction’’, while, in Cyrano de Bergerac, Edmond Rostand said it was a ‘‘rosy dot placed on the ‘i’ in loving’’.
The physical nature of a kiss was first revealed a few years ago in detail by an animated scan of a vertical cross-section through the head, made by Elaine Sassoon, Annabelle Dytham, Robert Scully and Professor Gus McGrouther at the Rayne Institute in University College London.
The scan revealed that a kiss is mostly due to the squashing of a pair of muscles with a J-shaped crosssection, drawing on all 34 facial muscles for success.
‘‘Not only do you use your facial muscles in kissing, but approximately 112 postural muscles as well,’’ added Professor McGrouther, now at the University of Manchester.
Kisses are ancient, an echo of a more primitive, chemical, form of communication, according to studies of mice by Kazushige Touhara and colleagues at the University of Tokyo.
The team has found non-volatile pheromones — signalling molecules — secreted from the eyes and transmitted by direct contact reveal what sex a mouse is to its peers. Although mice and humans are very similar at a genetic level, the gene encoding this pheromone does not exist in the human genetic make-up.
‘‘We lost this gene somewhere during evolution,’’ he said.
But mice and men are thought to share a common ancestor that lived between 75 and 125 million years ago, a rat-like creature called Eomaia scansoria ( Eomaia, Greek for ‘‘ancient mother’’ and scansoria, Latin for ‘‘climber’’) and Dr Touhara speculates that humans may retain a vestige of rodent behaviour because we still like to kiss or rub noses, depending on the culture, to maximise the chance of sampling another’s aroma, perhaps even to savour a non-volatile pheromone that signals desire.
In other words, a smooch, peck or smacker may be an echo of the way our furry ancestors once signalled to each other.
One head-turning observation of kissing was reported recently by Professor Onur Gunturkun of Bochum University in Germany, who had watched 124 couples in action at airports, railway stations, parks and beaches across the United States, Germany and Turkey.
His survey of 13 to 70-year-olds showed that twice as many people turned their heads to the right to kiss as to the left.
It is no accident that in Rodin’s masterpiece The Kiss, the lovers also turn their heads to the right. This is one of many examples of a righthanded preference: use of the right foot, eye and ear are also preferred with a ratio of 2:1.
During the final weeks in the womb, babies develop a preference for turning their heads to the right and his findings suggested that this preference lasts into adulthood, and, by setting up biases in movement and sensory perception, may influence other behavioural asymmetries.
Now this fascinating insight kissing has been confirmed.
‘‘A few weeks ago, an Irish study appeared that could show that kissing a doll’s face results in the same asymmetry as kissing a person,’’ he said.
Armed with this data, and from a new study he is conducting, Professor Gunturkun is able to predict overall kissing success rate, assuming that the individual kissing ‘‘head-motor bias’’ to the right is 2:1.
Of nine couples, four would both have the right bias, ensuring a successful kiss. One couple would have a left bias, again ensuring good initial contact. However, four couples would clash noses as they attempted a left/ right kiss and fail to ensure good initial lip-to-lip contact.
A few days ago, an insight into the enduring nose problem
intriguing was published in the journal Nature Neuroscience by Martin Sereno and Ruey-Song Huang of the University of California, San Diego. Planting a kiss on the lips, and avoiding the nose, requires ‘‘prompt, coordinated processing of spatial visual and somatosensory information,’’ said Dr Sereno. That co-ordination goes on in our heads, where we and our surroundings are represented.
Neurosurgeon Wilder Penfield is credited with establishing half a century ago that a map of the human body exists in the brain, with specific areas of the cortex processing information from different body areas. This is a topographic map of the body, where signals from adjacent fingers map to adjacent parts of the brain. Other parts of the brain contain maps of the retina, first revealed by the effects on vision of gunshot wounds to the head of World War I veterans. Using a brain scanner method called functional magnetic resonance imaging, the Californian team revealed changes in blood flow going to a part of the brain called the ventral intraparietal area. It integrates information relevant to the face (as distinct from the ‘‘fusiform face area’’ under the temporal lobe, that tells you whose face you are kissing).
As they did this, they varied the angle of air puffs to the face or moved segments of a video ( Xena: Warrior Princess) around on a screen close to the person’s face. They found aligned maps of touch and visual stimuli where nerve cells in the same region of the brain responded to either the touch or the sight of an object near the face, such as the brush of another’s lips on the upper right cheek, or the sight of those lips in the upper-right side of vision.
That region in the superior part of the postcentral sulcus may play a central role in planting a kiss, since it helps combine visual and touch information about objects.
‘‘The idea that the people who are clumsy with their head might have poorly tuned-up VIP/frontal circuitry is a natural hypothesis given what we have found,’’ said Dr Sereno.
Now we can answer the question posed in the by 19th century by the French poet Victor Hugo: ‘‘How did it happen that their lips came together?’’
We know exactly how. Exercise all 34 facial muscles, another 112 postural ones, turn the head to the right and move forward in one smooth movement to suction.
Pay tribute to that 125 millionyearclimbing-rat like mammal by savouring the non- volatile pheromones. It’s easy really.
Telegraph Group Ltd
SMOOCH: Planting a kiss on the lips requires prompt, coordinated processing of visual and sensory input. CULTURAL TRAIT: Rubbing noses, like a kiss, is an ancient practice and a way of sampling another’s aroma.
PECK: Genetically mice and humans are similar, and both kiss.