Laughter is a form of social bonding because it is contagious and allows us to show that we are non-threatening.
We laugh when we see or hear something funny. We laugh to show that we are being silly.

Laughter as a method of bonding

Self Improvement

Many anthropologists believe that language existed and evolved in the past few thousand years, but there is evidence suggesting that laughter arose from millions of years ago because we share the same structure of laughter with the great apes.

Laughter came before language

From a historical perspective it is ironic that tickling in the modern era is considered to be a way to bond for parents and their children because a few centuries back tickling was a form of punishment.
Thanks to evolution laughter became a way for people to enjoy each other&#39;s company without any danger or injuries.

Why tickling makes us laugh

What's the point of laughter? - BBC Science Focus Magazine

As the old saying goes, "life's better when you're laughing" -- and no one knows that more than good-humored individuals. Those who have a good sense of humor not only see the value in making others laugh, but they prioritize laughter themselves. And as a result, they're healthier and happier for it. Studies show that smiling <a href="https://www.huffpost.com/entry/mood-booster_b_4268889">instantly boosts your mood </a>and laughing can <a href="http://www.mayoclinic.org/healthy-living/stress-management/in-depth/stress-relief/art-20044456">soothe tension and melt stress </a>.

You make laughing a priority

Not all of us can be a person who is so open to their faults that they publicly make fun of their pitfalls, but people with a light-hearted attitude do practice more self-acceptance than most. Good-humored individuals embrace their flaws and laugh them off (and let them go) in a healthy way. And it's something others should work toward: Self-acceptance is a <a href="http://www.sciencedaily.com/releases/2014/03/140307111016.htm" rel="noopener noreferrer" target="_blank">key to a happier life, but it's not always practiced all that often </a>.

You practice self-acceptance

It takes a lot of mental energy to come up with quick-witted quips that keep grins on others' faces. Those who have a good sense of humor <a href="http://www.pbs.org/thisemotionallife/topic/humor/benefits-humor">tend to be more creative </a>. And that's not the only cognitive benefit: One 2014 study found that laughter can also lead to a <a href="http://abcnews.go.com/Health/laughing-makes-brain-work-study-finds/story?id=23393053">sharper short-term memory </a>.

You're creative

There's a line between well-intentioned humor and mean-spirited jokes, and those with good humor know the difference. "Most comedy is based on getting a laugh at somebody else's expense. And I find that that's just a form of bullying in a major way," <a href="http://www.cbsnews.com/news/ellen-degeneres-my-jobs-to-make-you-happy/" rel="noopener noreferrer" target="_blank">comedian Ellen DeGeneres told CBS News in 2012 </a>. "So I want to be an example that you can be funny and be kind, and make people laugh without hurting somebody else's feelings."

You‘re conscientious

Overall, humor can benefit us physically and emotionally, according to Peter McGraw, Ph.D., an associate professor at University of Colorado Boulder who studies emotions. "When done well, humor can have a significant positive effect on your life.By developing a better understanding of humor we believe we can then suggest ways that people can live better lives -- from helping them cope with pain and stress to encouraging people to use humor to criticize brands that have done them wrong."

You have good physical well-being. 

While most people fret with each passing birthday, good-humored individuals take it all in stride. Those "over the hill" cards? The jokes about looking older? Child's play -- and that light-hearted attitude may help you live longer. Research suggests that a <a href="http://www.ncbi.nlm.nih.gov/pubmed/20848871">sense of humor increases longevity into retirement </a>. Bring it on, birthdays.

laughter

Laughter as a method of bonding

What's the point of laughter? - BBC Science Focus Magazine

You make laughing a priority

6 Signs You Have A Good Sense Of Humor