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Thursday, 30 April 2015

Humour and Laughter

My April 29 blog on kissing also mentioned laughter as a unique human trait. That remark made me wonder about its origin in human evolution. "The use of language-based jokes is clearly unique to humans," according to Dunbar, an evolutionary psychologist. "There is some suggestion that apes 'play practical jokes' or laugh at another's misfortune, such as the banana skin situation, but these are only casual observations." Human laughter still has an animalistic quality, in the sense that it involves a series of rapid exhalation-inhalation cycles comparable to other primate sounds; it's louder than human speech; and, like sneezing, laughter is contagious. (source)

"We think laughter long predates the appearance of language in human evolution, and was co-opted from play as a mechanism to allow bonding between larger numbers of individuals," Dunbar explained. "Laughter triggers the release of endorphins, which are the neurochemicals used in bonding in monkeys and apes. Laughter allows us to increase the size of the bonding group because several people can laugh together; whereas grooming is, even in humans, a one-to-one activity, with only the recipient gaining the benefit of the endorphins." (source)

The 19th-century French physician Guillaume Duchenne discovered two kinds of smiling: the voluntary kind, the type of expression we produce when we a grin to be polite, and a second variety of smiling and laughing, one that occurs when we find something truly entertaining or funny. This expression is more complex and includes the muscles that form crow’s feet around your eyes. It’s why people say a real smile is in the eyes. Duchenne was never able to reproduce this second form of expression - now known as a Duchenne smile or Duchenne laughter - and he came to believe it was “only put at play by the sweet emotion of the soul.” (source)

Evolutionary theory is rife with possible explanations, but one of the most compelling was put forward in a 2005 Quarterly Review of Biology article by Gervais and evolutionary biologist Wilson. It’s based on the efforts of Duchenne. Gervais and Wilson saw Duchenne’s discovery as evidence that laughter evolved at two different points in human development. (source)

First, they posited, at a point sometime between 2 million and 4 million years ago, came Duchenne laughter, the kind triggered by something funny. An outgrowth of the breathy panting emitted by primates during play fighting, it likely appeared before the emergence of language. This sort of laughter was a signal that things at the moment were OK, that danger was low and basic needs were met, and now was as good a time as any to explore, to play, to socialise. (source)

But then, sometime in the hundreds of thousands of years after that, theorised Gervais and Wilson, the other sort of laughter emerged—the non-Duchenne sort, the kind that isn’t dependent on something being funny. As people developed cognitively and behaviourally, they learned to mimic the spontaneous behaviour of laughter to take advantage of its effects. (source)

Laughter is more than just a response to humour. It’s a primal human tool, one of the building blocks of society. It taps into the core of what we are as social creatures, expressing from one person to another what often cannot be said in any other way: either that everything is in good fun or that something is very, very wrong. (source)

To illustrate this, please see Mark Gungor's A Tale of Two Brains (short 1, short 2, short 3full).