The caresses, the embraces, the kisses, the embracing of the hands, all these gestures of affection that we use to signify to the elected or the elected of our heart that we love him, to show him all the feelings that drive us seem so natural that we believe them to be innate. But are these gestures really inscribed in our biology, in our genes? Scientists are trying to demystify the origin of these gestures that provide the much sought-after bliss.
Affectionately touching the people we love is certainly a widespread behavior throughout the world. “Everywhere, humans touch people [qu’ils apprécient] to express the affection they feel for them. This behavior is universal. We see this behavior not only across different human cultures, but also across species. This universality indicates that this propensity for affectionate touch is hardwired into our biology and that some of the mechanisms that drive these behaviors have been conserved through evolution,” says Kristina Tchalova, a research associate in social psychology at McGill University. .
However, there would be some cultural differences in the way we express our affection through touch. These distinctions would manifest according to what a culture considers appropriate in terms of the type of touch, the intensity of the touch, and the place (in public or strictly in private) to lavish these marks of attachment.
But what are the biological mechanisms that would allow us to affirm that the use of touch to express the love we feel for someone is probably inscribed in our genes?
Mme Tchalova first recalls that the skin of mammals is endowed with a class of receptors and nerve fibers, called tactile afferents C, which react specifically to stimulation combining light pressure and a slow speed of about three centimeters per second, which correspond to those of a gentle caress most often perceived as pleasant. “It’s exactly the pressure and speed of touch that people tend to use instinctively when caressing their loved one while sitting on the sofa, for example. We all instinctively know how to touch our loved one in a way that specifically stimulates the nerve fibers that communicate with the parts of the brain that induce pleasure,” she points out.
In addition, several species of non-human primates practice social grooming where two individuals apply themselves to cleaning the fur of the other and to ridding it of parasites. This activity, which involves abundant tactile stimulation and which is known to strengthen relationships between individuals, also shows that the use of touch is universal, even across species, underlines the scientist.
Researchers have found that a social grooming session induces the release of beta-endorphin, an endogenous opioid that induces a pleasant, soothing and analgesic sensation, in animals that practice it. They also observed that when they administered naloxone, a drug that neutralizes the effects of opioids, to young monkeys, the latter always demanded more contact and grooming time with their mother. “The little monkeys were desperately trying to regain the pleasant and soothing effect they usually experienced when they were cuddled and groomed by their mother,” says Ms.me Tchalova.
“This biological mechanism ensures that we stay close to the individual with whom we have a relationship. [Et pour maintenir ce lien], we need to receive a reward, to feel good close to the other, but also to feel pain when the other is far from us or when we are separated from them. Pain is a very important part of attachment,” notes the researcher.
However, the opioid system is responsible for the pleasant effect and it also plays a role in pain, she points out. “When the animals were separated from the individual to which they were attached, a phenomenon similar to the opiate withdrawal syndrome occurred which contributed to this sensation of pain which caused the animals to try to reestablish proximity with the object of attachment. Although all these observations have been made in non-human species, we assume the existence of an almost similar phenomenon in humans”, specifies the scientist.
Babies and children are completely defenseless and entirely dependent on their mother for protection. “In the past, when there weren’t these nice daycares and humans lived in more dangerous environments where predators roamed, children absolutely had to stay close to their mothers. For this reason, we believe that these biological mechanisms are written into our genetic code,” says Ms.me Tchalova.
We also know that certain tactile stimuli cause the release of oxytocin, which was once called the love hormone. In non-human species, oxytocin has been shown to promote social bonding. In humans, its action would be more complex. Oxytocin would elevate our sensitivity to social stimuli present in our environment and increase our motivation to engage if the nature of our social environment is adequate. “Opioids and oxytocin probably work together. Maybe if you’re with your partner, the oxytocin focuses your attention on him and the opioids tell you that this interaction is very pleasant, ”says the researcher.
This instinctive propensity to touch the loved one therefore has the function of cementing our relationships with the other, of motivating us to stay close to them. But it also has another physiological function, that of “helping us regulate our response to stressful events. It tends to remind us that we are safe with our loved one. Experiments have shown that the ventromedial prefrontal cortex, which plays a role in sending these safety signals, activates when we see danger moving away, as well as when we see images of the person we are with. attached,” emphasizes the researcher.
Touch is unquestionably vital in the development of attachment and therefore its use is undoubtedly universal. “Given its importance, given that non-human primates also use it, we can fairly safely assume that our ancestors used touch to show affection,” says Ms.me Tchalova.
The forms of touch would be more cultural. The romantic kiss, for example, would not be practiced in the majority of human societies (46% of the 168 cultures studied by William R. Jankowiak, of the University of Nevada in Las Vegas). Today’s hunter-gatherer populations in particular do not kiss. The prevalence of its use appears to be correlated with the social complexity of society. “The more socially complex a culture, the higher the frequency of romantic kissing,” Jankowiak and his colleagues noted in their study.
The romantic kiss where the lips and the tongue of the two partners are in contact would probably result from a maternal behavior of infant care “practiced from the beginning of the evolution of hominids in the Paleolithic and still today by certain cultures”, recalls Iulia Badescu, assistant professor in the Department of Anthropology at the University of Montreal.
The parents chewed the food, then pushed it with their tongues into their infant’s mouth. “This mouth-to-mouth sharing of pre-chewed foods was probably the first type of complementary feeding [au lait maternel] given to infants, which made it possible to wean children more quickly from breast milk and thus contributed to the demographic growth of hominids at the beginning of the Paleolithic period,” remarks Ms.me Badescu.
One thing is certain, the need for love is universal.