Mouth-to-mouth contact has been observed across multiple species, including fish, birds, and primates; its functions can range from exchange of food, to assessment of physical abilities. However, intimate kissing involving deliberate, prolonged tongue contact and saliva exchange, appears to be an adaptive courtship behaviour unique to humans. The fact that it is common in 90% of cultures is perhaps less interesting than the fact that it is not common in the remaining 10%.
Read More