Why do humans laugh?

The answer

Laughter is a universal human behavior that evolved primarily as a social bonding mechanism rather than a simple response to humor. Humans are 30 times more likely to laugh in social situations than when alone, and most laughter occurs during ordinary conversation rather than in response to jokes. Laughter triggers the release of endorphins, the brain's natural feel-good chemicals, which promote feelings of warmth and trust between people. Robert Provine's research showed that speakers laugh even more than listeners in conversations, suggesting laughter serves to regulate social dynamics. Laughter is also contagious due to mirror neuron activation, is present in human infants as early as 4 months, and has analogs in other social mammals including rats, which produce ultrasonic chirps during play.