Kissing feels so tied to human life that it can seem almost impossible to separate from romance, family, grief, ritual, or desire. It sits inside wedding vows and movie endings, in greetings, apologies, and quiet moments that do not need words. Yet mouth-to-mouth contact did not begin with people, and it does not belong to us alone. Across the animal kingdom, behaviors that look a lot like kissing appear in species as different as bonobos, prairie dogs, doves, wolves, and dogs. The meanings shift from one species to another. Some use it to calm tension. Others use it to recognize a familiar neighbor, court a mate, or signal submission. Humans may not be unique for kissing, only for the layers of feeling and symbolism we attach to it. A recent comparative analysis out of the University of Oxford pushes that idea much deeper into the past. Using a narrow definition, non-aggressive mouth-to-mouth contact between members of the same species, involving the lips or mouthparts and excluding food transfer, the researchers concluded that kissing likely reaches …