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.