QUOTE : Absorption of parental care into adult human relationships is evident from the widespread use of infantile names (such as "baby") for mates and lovers, and the special high-pitched voice that we reserve for both young children and intimate partners. In this context, Eibl-Eibesfeldt mentions the kiss, which probably derives from mouth-to-mouth feeding of masticated food. Kissing without any transfer of food is an almost universal human expression of love and affection, which, according to the ethologist, resembles kiss feeding "with one partner playing the accepting part by opening the mouth in a babyish fashion and the other partner performing tongue movements as if to pass food." Significantly, chimpanzees both kiss feed their young and kiss between adults. A close relative of the chimpanzee, the bonobo, even tongue-kisses.