the biology of you and me
Kissing allows mates to smell and taste each other's pheromones for biological compatibility.
Women are more attracted to men whose major histocompatibility complex portion of their genome is different from their own, leading to offspring who will be resistant to a greater number of diseases due to heterosis, and thus having a better chance at survival...
You can always buy kisses, from fish that is.The hotspring kissing fish therapy has be proven effective to heal some skin disease such as psoriasis and dermatitis. The kissing fish are cyprinion macrostomus and garra rufa. Neat.