It’s a defining moment of any romantic relationship. But don’t you sometimes wonder how humans learned to derive shared pleasure from locking lips?
Suite101.com has a thorough article covering the anthropological origins of the kiss:
So who invented kissing? Anthropologists think kissing’s origins are to be found in primitive times when mothers chewed food and transferred it directly from their mouths to their babies’ mouths, a method of preparing baby food that is still practiced in some cultures today. Another theory comes from the Ziller Valley of Central Europe where pre-chewed tobacco was exchanged between males and females. The man would hold …read more

How do we categorise hand-holding? Have you ever wondered why such an act can trigger all sorts of emotions within you? What message do you relay when you hold another person’s hand?
Wikipedia lists the reasons and purposes when two or more people engage in the act of hand-holding and I’d like to cite some of them:

Rituals
Expression of friendship or love
Enjoyment of physical contact
Emotional support
Physical guidance
Dancing
Arm wrestling

With that said, I’d like to focus on it being an act of expression of friendship and love.