New research suggests that the origins of kissing may be linked to body hair. According to primatologist Adriano Lameira, kissing could have evolved from adult apes cleaning each other's fur to remove parasites and debris. This "kissing" behavior would have been a sign of social bonding and kinship ties in ancestral ape communities. While this theory doesn't necessarily mean that kisses are inherently romantic or hygienic today, it provides an interesting perspective on the origins of our most intimate expression of affection.

Source: https://www.popsci.com/environment/ape-grooming-kissing/