Premastication or pre-chewing is the act of chewing food for the purpose of physically breaking it down in order to feed another that is incapable of masticating the food by themselves. This is often done by the mother or relatives of a baby to produce baby food capable of being consumed by the child through the weaning process. The chewed food in the form of a bolus is transferred from the mouth of one individual to another, either directly mouth-to-mouth, via utensils, hands, or further cooked or processed prior to feeding. [1] [2] Many modern societies have strong aversions toward premastication, which has been compared to the aversion towards breastfeeding in the same societies during previous generations.[3]
Premastication and mouth-to-mouth feeding in humans is postulated to have evolved from the regurgitation of food from parent to offspring or male to female (courtship feeding) and has been been observed in numerous mammals and animals of other species.[4]
In many human cultures, the act of premastication and direct mouth-to-mouth feeding is linked with the showing of affection, known as kiss feeding. This form of feeding is believed to have evolved into the modern human acts of kissing and french kissing.[5]
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The act of premastication is commonly found in all human societies and populations, although less prevalent in some than others. The evolution and selective advantage of premastication behaviours is that doing so allows in infant to supplement breast milk for nutrition by providing access to more macro and micro-nutrients. Although disease can be transmitted through saliva in the pre-chewed foods, these benefits conferred outweighed any risks of the practice faced during the evolution of humans.[3]
Premastication/kiss-feeding or kissing has between mother and infant has been observed in all human cultures, with kissing believed to be a socially ritualized from of feeding premasticated food.The similarity between kiss-feeding and human kisses (e.g. French kiss) are very similar in its execution; in the former, the tongue is used to push food from mother to child with the child receiving both the mother's food and tongue in sucking movements, and the latter simply forgoes the premasticated food.[5] In fact, observations across various species and cultures confirms that the act of kissing and premastication have most likely evolved from the similar relationship-based feeding behaviours.[4][5]