Laughing and smiling
Babies smile, adults smile when flirting (Professor Irenaeus
Eibl-Eibesfeldt published a lot about that), and/or when they are
embarrassed, ashamed or out of politeness and so on. Laughing can be
aggressive, exclude or expel people from a group, it can serve to build
a hierarchy in groups of humans without using physical force. Maybe
smiling and laughing has its origins in evolution out of snarling in
animals (showing teeth)- aggression against a common enemy can create a
bond- this idea, by the way, is not from Konrad Lorenz but from Niccolò
Machiavelli (”Il Principe”). Laughing can punish dissidents in groups of
humans and promote uniform opinions. Women and girls laugh, smile and
giggle more than men do.