Apparently, laughter predates human speech by perhaps millions of years. It would have been a form of communication. "Most laughter is not in response to jokes or humor," says Robert R. Provine, a professor of psychology and neuroscience at the University of Maryland Baltimore County. Professor Provine has done studies of laughter, and also authored a book "Laughter: a Scientific Investigation." Apparently, people who are born deaf and blind still laugh, which shows that laughter is not learned, but innate. We’re born with the capacity to laugh.
As for the inappropriate laughing? Laughter isn't under our conscious control, and this would explain why we laugh at the most awkward times.
Laughter is contagious, and this is due also to evolution! If one of us laughs at something, others will laugh as well - ever noticed how much funnier things seem when someone else is laughing with you?There have even been laughter epidemics! I am not kidding you! One, quoted by WebMD was in 1962, in the African country that is now Tanzania. Three school girls began to laugh uncontrollably. Within a few months, about two-thirds of the students had the symptoms, and the school closed. The contagion spread, and eventually affected about a thousand people in Tanzania and neighboring Uganda. There were no long-lasting effects, but it shows how responsive people can be to seeing another person laugh.
Many researchers believe that the purpose of laughter is related to making and strengthening human connections. "Laughter occurs when people are comfortable with one another, when they feel open and free. And the more laughter [there is], the more bonding [occurs] within the group," says cultural anthropologist Mahadev Apte.
The first laughter appears at about 3.5 to 4 months of age, long before we’re able to speak. Laughter, like crying, is a way for an infant to interact with the mother and other caregivers. When we laugh, we’re often communicating playful intentions. So laughter has a bonding function within individuals in a group. It’s often positive, but it can be negative too. There’s a difference between “laughing with” and “laughing at.” People who laugh at others may be trying to force them to conform or casting them out of the group.
Scientists know very little about the brain mechanisms responsible for laughter. But they do know that laughter is triggered by many sensations and thoughts, and that it activates many parts of the body. When we laugh, our facial expressions alter, and we make sounds. If we laugh exhuberantly, the muscles in the arms, legs and trunk are involved. Laughter also requires us to modify our breathing pattern.
And laughter is supposed to have health benefits as well - laughing 100 times is equivalent to a 10-minute workout on a rowing machine, or to 15 minutes on a stationary exercise bike. Laughing exercises the diaphragm, as well as the abdominal, respiratory, facial, leg, and back muscles.
Another benefit of laughter is that it improves our over-all mental health. Pent up negative emotions, such as anger, fear, and sadness, can cause biochemical changes in our bodies that can produce a harmful effect. Laughter provides a harmless outlet for these negative emotions, and provides a coping mechanism for dealing with difficult or stressful situations.
Laughter also has a very dark side, as Professor Povine stated:
"When gangs or groups of militants attack someone, they are often reported to laugh while doing it." It's the sinister aspect of laughter's power to form group cohesion. Sometimes, those bonds can be used to exclude or persecute others."
Much more research has yet to be done about laughter, but some researchers believe that the two types of laughter -- spontaneous and nonspontaneous -- actually have different origins in the brain. The spontaneous laughter originates in part from the brainstem, an ancient part of the brain. So it might be a more original form of laughter. The other type of laughter comes from parts of the brain that developed more recently, in evolutionary terms.