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 is further cooked or processed prior to feeding.
[10] 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.
[10] Many Western societies have strong aversions toward premastication, which have been compared to their similar criticisms and aversion towards breastfeeding in previous generations for similar rationale,[3] with the same societies finding breastfeeding to be a disagreeable practice performed only by the uneducated lower classes or foreign cultures[24] and altering health policies to the detriment of infant health.
[25] In the late 1800s the medical community of Texas was embroiled in a debate on premastication, with those supporting the practice arguing its benefits and those against it stating that it is "filthy and repulsive and...
The evolution and selective advantage of premastication behaviours is that it supplements the infant diet of breast milk by providing access to more macro- and micro-nutrients, as well as digestive enzymes.
[4] Although disease can be transmitted through saliva in the pre-chewed foods, the benefits conferred outweighed any risks of the practice during the evolution of human behaviour.
[26] In populations with healthy caregivers, premastication is not correlated with negative health consequences,[27] with potential benefits and pitfalls of this practice greatly depend on the dietary and medical circumstances of the provider and child.