We’ve been trying to unlock the laugh for over half a century, and we’re finally forming some idea of where it comes from.
The purpose of the laugh, anthropologically, is to convey friendliness, cooperation and an absence of hostility.
“It is immediately clear and engaging and this is why it is still active.”Bubbling upThe first truly human laugh may have emerged only about two million years ago, when early hominids developed the ability to wilfully control facial motor systems.
“This can be considered counterintuitive, but it turns out that human laughter is also produced by incongruity,” says Dr Bellieni.
Blocking this region, the researchers state, in a study published in the journal Neuron in 2023, actually made the rodents less playful.
We’ve been trying to unlock the laugh for over half a century, and we’re finally forming some idea of where it comes from.
The earliest scientific research in this field was conducted in the 1960s, as part of gelotology, or the study of the psychological and physiological effects of humour. In one experiment, Stanford University professor William F Fry drew his own blood at intervals, while watching Laurel and Hardy films. Later analysis showed that laughter increased the activity of immune cells that kill infectious pathogens.
The experiment only confirmed what humans had instinctively known for millennia.
“A merry heart doeth good like a medicine,” goes a Biblical proverb. It likely gave us “Laughter is the best medicine” (traceable to the King James Bible, first published in 1611).
It is certainly a kind of medicine. Laughter releases a host of feel-good hormones, including endorphins and dopamine. It enhances the intake of oxygen, stimulates heart, lungs and muscles. The purpose of the laugh, anthropologically, is to convey friendliness, cooperation and an absence of hostility. It is a form of human bonding and intimacy. All these factors explain why children laugh so much during play.
But how old is it, and where does it come from?
It turns out that the laugh evolved from panting, which was the original mechanism for the release of pent-up positive emotion, as great apes indulged in rough-and-tumble play.
It evolved into today’s vocalisations, in a common ancestor of today’s apes and humans, between 10 and 16 million years ago, shows research conducted by psychologists and a zoologist (from the Universities of Portsmouth, Georgia State and Veterinary Medicine Hannover, published in the journal Current Biology in 2009).
In this study, the researchers showed that when they tickled great apes (chimpanzees, gorillas, orangutans and bonobos), their reaction was similar in acoustical properties to that of tickled babies. A computer program plotted these recordings on an evolutionary tree, based on similarities in sound, and concluded, based on the acoustic recordings alone, that all five species were linked to a common ancestor from the period mentioned, with the chimps’ laughter being the closest to that of the human babies. Chimpanzees, incidentally, even jut their lips out and blow raspberries, in an expression that humans still use.
Why would the laugh as an expression have survived? “Evolution tends to perpetuate those behaviours that offer an advantage for survival,” says Dr Carlo Valerio Bellieni, a professor of paediatrics at University of Siena in Italy, who has been studying the role of laughter. It helps humans communicate and bond, even within larger groups, in a way that words and even physical touch don’t.
Along with other vital non-verbal communication behaviours, such as reddening in the face, trembling with fear and crying, laughter is a primordial process that speaks without speaking, Dr Bellieni adds. “It is immediately clear and engaging and this is why it is still active.”
Bubbling up
The first truly human laugh may have emerged only about two million years ago, when early hominids developed the ability to wilfully control facial motor systems.
Laughter would have been used to express camaraderie, joy, mirth, embarrassment… and derision. It is from this point on that the “dark side” of laughter, unique to humans, emerged, say researchers from Binghamton University, in a 2005 study published in the Quarterly Review of Biology.
“Humans can now voluntarily access the laughter program and utilise it for their own ends, including smoothing conversational interaction, appeasing others, inducing favourable stances in them, or downright laughing at people that are not liked,” the Binghamton biologists Matthew Gervais and David Sloan Wilson noted, in a statement.
As language evolved, laughter would become attached to the spoken joke.
“This can be considered counterintuitive, but it turns out that human laughter is also produced by incongruity,” says Dr Bellieni. “We are generally programmed to react negatively when we find that something does not align in a situation. But if we see that this misalignment occurs in a safe context, we relax at once, and we want all the bystanders to know that all is okay. We do this with the non-verbal signal of laughter.”
Of mice and men
Primates aren’t the only animals with laughter-like vocalisation. About 65 species are known to use some form of this expression, ranging from chuckles and panting to whines, clicks and high-pitched ultrasonic squeaks, found a meta-study by scientists at University of California, Los Angeles, published in the journal Bioacoustics in 2021.
Species with such expressions include domestic cows and dogs, wild foxes, seals, mongooses, certain bird species (including parakeets and Australian magpies) and mice, whose squeaks, incidentally, are inaudible to humans.
“When we laugh, we are often providing information to others that we are having fun and also inviting others to join,” Sasha Winkler, a primatologist who worked on the study, said in a statement. “Some scholars have suggested that this kind of vocal behaviour is shared across many animals who play, and as such, laughter is our human version of an evolutionarily old vocal play signal.”
Rats, reportedly, “laugh” quite a lot. In 1997, neuroscientist Jaak Panksepp tickled some as a graduate student recorded their “laughter” for the first time, using bat detectors. “It sounded like a playground!” the researcher famously said.
Interestingly, a study conducted last year found that the link between laughter and fun works both ways. Researchers from Humboldt University in Berlin used electrodes to study rats’ brains, while they tickled them on their backs and bellies, and while the rats played with each other.
They found that a particular part of the brain lit up at such times: the periaqueductal gray or PAG region. This is the area that controls vocalisations. Blocking this region, the researchers state, in a study published in the journal Neuron in 2023, actually made the rodents less playful.
It’s something to hold on to, the laugh. It unites us with parts of the animal world, and with something even bigger: an ancient need to express a simple, welcoming emotion without the tangle that can result from words.
