Laughter is one of the most familiar sounds in the world, yet it remains surprisingly mysterious. We laugh many times a day, usually without deciding to, and we find it almost impossible to stop once we start. Babies laugh months before they can speak a single word. Why should a species that values language so highly communicate so much through a sound that carries no words at all?
One clue comes from our animal relatives. When young chimpanzees and gorillas play-fight or are tickled, they make a breathy panting sound, which many researchers regard as an early form of laughter. Even more surprising was the discovery by the neuroscientist Jaak Panksepp that rats produce high-pitched chirps when they are tickled, sounds too high for human ears to hear. The rats chased the hand that tickled them and seemed to enjoy the game. Findings like these suggest that laughter is far older than humanity, and that it began not as a reaction to jokes but as a signal during play: this is fun, not a real fight.
That idea is supported by the work of the psychologist Robert Provine, who spent years listening to people laughing in shopping centers, on university campuses and on city streets. He discovered that most laughter does not follow anything particularly funny. Instead, it follows ordinary remarks such as "See you later" or "I know what you mean." He also found that people are around thirty times more likely to laugh when they are with others than when they are alone. Laughter, in other words, is less about humor than about relationships.
This social function may explain why laughter is so contagious. Hearing someone laugh activates areas of the brain that prepare us to join in, which is why television comedies have long used recorded laughter. A shared laugh tells others that we are relaxed, friendly and on the same side. It can reduce tension after an argument and make strangers feel like members of a group.
Laughter seems to benefit the body as well. In experiments led by the British researcher Robin Dunbar, people who had just watched a comedy could tolerate more pain than those who had watched a serious documentary. Dunbar suggested that the physical effort of laughing triggers the release of endorphins, the brain's natural painkillers, which also create feelings of warmth and closeness.
None of this means that humor is unimportant. Jokes and comedy are among the great achievements of human culture. But the deepest roots of laughter lie elsewhere, in the simple pleasure of play and the need to connect. The next time you laugh with friends at something that is not even funny, you need not feel foolish. You are taking part in one of the oldest conversations on Earth.