In 2001, neuroscientist Robert Provine and his team observed over 1,200 people spontaneously laughing in different locations and noted several interesting things:

Laughter is found in humans of all cultures.
People can't laugh on command without it being fake.
People laugh 30 times more often when with others
Laughter is contagious.
Babies show laughter in as early as 4 months
Only 20% of laughter is from jokes! Most actually follows normal conversations and actually bonds people socially.
People tend to laugh at the end of sentence rather than in the middle.
Women laugh more than twice as much as men.
The higher up in social status you are the less you will laugh.