by Peter McGraw
That’s how we find ourselves on stage at an African burlesque show, staring at a room of frowning men gnawing on blackened animal pieces and wondering what the hell we’re doing up here, blocking their view. And so we dance. Pete waltzes with one of the dancers like he’s Al Pacino in Scent of a Woman. I play coy with the ladies on stage and shake my butt at the audience. Pete trots out “the lasso,” twirling an invisible rope and using it to capture one of the dancers. All for the sake of science.
We return to our seats amid the sounds of chuckles and claps. We weren’t the sexiest dancers to grace the stage, but we were the funniest. And that has to count for something, since humor wouldn’t have evolved in humans if it wasn’t appealing from a sexual-selection standpoint—if it weren’t, at some level, “sexy.”
Sure enough, a survey of 700 men and women discovered that people considered humor among the most important of all characteristics when choosing a partner, romantic or otherwise.6 And studies of happy marriages, especially those lasting more than a half century, find spouses often ascribe their marital bliss in part to laughing together.7 This finding makes sense, says Pete: if you and your partner can make each other laugh, that suggests you have a similar sense of humor and therefore share compatible values, beliefs, and interests. Plus you’re both adept at making the other person happy.
Unfortunately, research also suggests the opposite: humor can signal doom for a relationship. Studies have found that dating couples who exhibit strong senses of humor—and not mean-spirited humor, mind you, but positive and friendly humor—are more likely than others to break up. As paradoxical as that sounds, it’s not absurd. Since humor is such a highly regarded personal trait, it’s more likely that others will be enticed by these attractively funny people and will lure them away from their partners.8
But what, exactly, is evolutionarily attractive about a sense of humor? What use from a survival-of-the-species perspective is the ability to recognize what’s funny and then bark about it? Some evolutionary theorists have posited that humor must have developed to demonstrate intelligence and creativity through wit, while others see laughter as a vocal adaptation of social grooming, a way to build bonds with one another without having to pick critters off each other’s hides. The list of theories goes on: laughter could have been a “disabling mechanism,” a way to signal that poking that crocodile with a stick is so laughable it might threaten our genetic survival. Or it could have been a way to determine winners and losers on the social strata—differentiating between those who deserve to laugh at others and those who deserve to get laughed at without resorting to prehistoric gladiator battles.9 Or it could have been a signal of false alarm, a vocal demonstration that the rustling in the bushes wasn’t a saber-toothed tiger as expected, just a harmless antelope.10 One of the newest theories suggests that laughter could be the brain’s version of an error message, that it evolved as a way for the mind to notice, reward the discovery of, and verbally signal mistaken leaps to conclusion.11
All these ideas are compelling in their own ways, but most lack hard evidence to verify their claims. If Pete were a betting man, he’d put his money on an idea put forward in 2005 by an undergrad named Matthew Gervais and his advisor, evolutionary biologist David Sloan Wilson, at Binghamton University in New York. In 29 heady pages in the Quarterly Review of Biology, the two wove together findings from neuroscience and positive psychology and multilevel selection theory to synthesize a novel and compelling account of how and why we developed the ability to laugh. It’s the sort of virtuoso academic performance that makes a science geek like Pete gush, “That paper is amazing.”
What’s possibly most intriguing of all about their theory is that its key piece of evidence originated, of all places, from the work of a quirky nineteenth-century fellow named Guillaume Duchenne, a guy who went around zapping people’s faces with electrodes. Duchenne, a French physician, became obsessed with figuring out what happened to human bodies when he shocked them with the hot new gizmo of the time: a portable battery and induction cable. Luckily for him, he worked at a women’s hospice, so he had access to a lot of prone bodies to zap. He must have been quite the charmer. All the ladies wanted to be electrocuted by the “little old man with his mischief box.”
Applying the prongs of his mischief box to people’s faces, Duchenne evoked and captured one kind of smiling—the voluntary kind, the type of expression we produce when we grin or chortle to be polite. This mannerism, he discovered, involves the face’s zygomatic major muscles raising the corners of the mouth. But Duchenne discovered there was a second variety of smiling and laughing, one that occurs when we find something truly entertaining or funny. This expression was more complex, utilizing both the zygomatic major muscles and the orbicularis oculi muscles that form crow’s feet. It’s why people say a real smile is in the eyes. Duchenne was never able to reproduce with his electrodes 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.” It was one of many scientific discoveries by the erstwhile electrocutioner, though Duchenne might have taken things too far in his book The Mechanism of Human Physiognomy. He had a beautiful model pose as Lady Macbeth while he zapped her face into different theatrical expressions.12
More than a century later, Gervais and Wilson saw Duchenne’s discovery as evidence that laughter evolved at two different points in human development. First, they posited, at a point sometime between 2 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 okay, that danger was low and basic needs were met, and now was as good a time as any to explore, to play, to start laying the social groundwork that would lead to civilization. And this part of laughter’s evolution could tie with Pete’s idea that humor is elicited by benign violations, said Gervais, now a doctoral candidate in biological anthropology at UCLA. “There could be a violation or incongruity of expectation going on, but what’s being signaled by the laughter is that it’s not serious, or it’s benign,” Gervais told me. “What the humor is indexing and the laughter is signaling is, ‘This is an opportunity for learning.’ It signals this is a non-serious novelty, and recruits others to play with and explore cognitively, emotionally, and socially the implications of this novelty.
“I think it’s an important part of the human story that humans are learners,” he continued. “And something like an appreciation of humor is a process that encouraged exploration and learning for a species that has a brain built to learn.”
But then, sometime between 2 million years ago and the present, theorized 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 behaviorally, they learned to mimic the spontaneous behavior of laughter to take advantage of its effects. They couldn’t get it right—they couldn’t simulate the eye-muscle movements of real laughter and smiling—but it was close. It’s similar to the way some moths evolved “owl eye” patterns on their wings to scare away predators—but in the case of non-Duchenne laughter, the point wasn’t to scare away, it was to bring others closer. Mimicked laughter was a way to manipulate others, to hot wire their vulnerability to be entertained—sometimes for mutually beneficial purposes, sometimes for more devious reasons. As Gervais and Wilson put it in their paper, “non-Duchenne laughter came to occur in aggressive, nervous, or hierarchical contexts, functioning to signal, to appease, to manipulate, to deride, or to subvert.”13
It’s a compelling, if not the most cheerful, account of why we laugh. If Gervais and Wilson are right, what about the laughs we inspired at the African strip club? Were the chuckles the old kind, the involuntarily stuff of genuine amusement? Or the non-Duchenne, darker version—laughter meant to appease, or wor
se still, to deride? I’m hoping for the former, but I have a feeling it might be the latter.
Since we’re in Africa, we figure we ought to go on a safari. Rutta is happy to oblige, one morning aiming the van toward Rubondo Island National Park, a 176-square-mile nature preserve off the coast of Lake Victoria. As we zoom up and down the rolling green hills skirting the lake, Pete fires up some Tupac Shakur on his iPod. “In the citaaay, the city of Compton!” sings Rutta, a big hip-hop fan, as we blow past longhorn cattle and vervet monkeys scampering about on the side of the road. “You know,” Rutta says to Pete, “most professors don’t act like you.”
“Thank you,” says Pete.
We eventually stop at a small, mud-bedraggled port, where we charter a small red-and-white motorboat to take us across a thin strait to Rubondo Island. Two somber-faced men in gray parkas sit behind us in the boat, armed with sizable old machine guns. We decide not to ask what threat, human or animal, necessitates that kind of firepower. When we reach the island, a four-wheel-drive safari jeep takes us through its densely forested interior. As we rumble down a two-track dirt road, foliage whipping at the windows and overhead vines sliding along the roof, I eye Rutta’s stylish camouflage shirt-and-pants combo and safari vest. As usual, he’s dressed for this excursion far better than we are.
We hope to spot some of the chimpanzees that inhabit the island, maybe even get a chance to tickle them. As we’ve noted, it’s believed that human laughter evolved from the distinctive panting emitted by our great-ape relatives during rough-and-tumble play to signal it’s all in good fun and nobody’s about to tear anybody else’s throat out. In a clever bit of scientific detective work, psychologist Marina Davila-Ross of the University of Portsmouth in the United Kingdom digitally analyzed recordings of tickle-induced panting from chimps, bonobos, gorillas, and orangutans, as well as human laughter, and found the vocal similarities between the species matched their evolutionary relationships. Chimps and bonobos, our closest relatives, boasted the most laughter-like kind of panting, while the noises of gorillas, further down our family tree, sounded less like laughing. Orangutans, our truly distant ancestors, panted in the most primitive way of all.14
Even if we don’t find one of our hairy relations out here in the jungle, maybe we can at least find a rat or two and tickle them. There are scientific antecedents to support such a venture. In 1997, psychologist Jaak Panksepp entered his lab at Bowling Green State University in Ohio and told undergrad Jeffrey Burgdorf, “Let’s go tickle some rats.” The two and their colleagues had already discovered that lab rats emitted a unique ultrasonic chirp in the 50-kilohertz range when they played. Now they wondered if they could prompt these squeaks through tickling. Sure enough, when the researchers began poking at the bellies of the rats in their lab, their ultrasonic recording devices picked up the same 50-kilohertz sounds. The rats eagerly nestled their fingers for more. Soon, as the news media trumpeted the existence of rat laughter, people the world over were opening up their rat cages and engaging Pinky and Mr. Pickles in full-scale tickle wars.15
“I don’t necessarily call it laughter; I call it a signal of positive affect,” Burgdorf told us when we visited him at Northwestern University’s Falk Center for Molecular Therapeutics in Chicago, where he now works as a biomedical engineering professor. Burgdorf’s careful choice of words makes sense. He and Panksepp faced serious critical pushback when their rat-tickling activities first went public. But whatever you want to call it, Burgdorf, a quick-witted guy with a boyish face and a sign on his office door that reads “Know-It-All,” has been obsessed with that strange rat noise he first stimulated in 1997. “How do I know that it’s really a sign of positive affect?” he said to us. “That’s been the question of my career.”
So far, it seems he’s on to something. He found the 50-kilohertz chirping changed when one of the animals involved in rough-and-tumble play was much larger than the other, when it was no longer fun and games and instead outright bullying—or as Pete would say, when the physical violations were no longer benign. And when given a choice, Burgdorf’s rats would push a bar to play a recording of the 50-kilohertz chirp as opposed to other rat noises, suggesting they had a preference for the sound. Finally, when Burgdorf and his colleagues used electrodes, opiates, and other manipulations to stimulate the reward centers of rats’ brains, the rats produced that same laughter-like noise.
And now, here in this lab, with its key-card-required security doors and freezers of bio samples and warning signs for radioactive materials, Burgdorf is using his rats and their special squeaks to test a new depression medication designed to increase positive mood. Clinical trials are already in phase two, and if all goes well, the drug might hit the shelves in three or four years. That’s right: Big Pharma is using laughing rats to develop a happy pill.
Tickle-loving rats, joke-playing gorillas, even stories of dog laughter—these reports could just be the beginning, said Marc Bekoff when we met him at a coffee shop in Boulder, Colorado. Bekoff, a colleague of Pete’s at the University of Colorado, where he’s a professor emeritus of ecology and evolutionary biology, is one of the world’s foremost experts on animal emotions. And he, for one, believes we’re on the cusp of discovering that lots of animals have a sense of humor, maybe even all mammals. He pointed to Darwin’s idea that the difference between human and animal intelligence is a matter of degree, not of kind. Or as Bekoff put it, “If we have a sense of humor, then non-human animals should have a sense of humor, too.” Considering the groundbreaking discoveries that ethologists like Bekoff are making about animal behavior, from dogs understanding unfairness to baby spiders displaying different temperaments to bees being taught to be pessimistic, the idea of thousands of inherently funny species might not be all that far-fetched.
Unfortunately, cruising through the wild kingdom of Rubondo Island in our safari jeep, we don’t spot any chimps, rats, dogs, or other animals to tickle. So we park the vehicle by a guesthouse near the water, and Rutta suggests the three of us go bushwhacking. We set off into the woods, climbing over tree trunks and pushing through foliage, hot on the trail of . . . well, anything at all safari-worthy. Along the way, Rutta points out a heaping pile of elephant dung, which Pete nearly steps in. Then Pete tries swinging Tarzan-style from a hanging vine, and somehow doesn’t end up killing himself. After that, Rutta guides us to a shallow cave in a cliffside he’s visited before, pointing out a collection of bones scattered about its floor. “Dead people,” he explains, remnants of a time when foreigners like us weren’t so welcome on the island. Now I’m starting to wonder about those rifles our escorts brought along.
“If I don’t almost get eaten, I will be disappointed,” declares Pete as we tromp through the underbrush. A few minutes later, I feel a stinging pain on my leg, then another. Looking down, I find black soldier ants swarming my feet and legs, crawling into my shoes and under my socks and biting hard any time they come across skin. Pete’s covered in them, too. We slap at our legs, cursing in pain as the little buggers make a meal of our calves. Meanwhile Rutta, diligent safari guide that he is, pulls out his camera and starts taking photos of our misery.
Our walk in the jungle a bust, we return to the guesthouse and try a different tack: we pay the pilot of a small dinghy moored by the shore to take us around the island’s shoreline. Motoring along the coast, we find wildlife: cormorants and egrets and ibis perched by the shore, African fish eagles swooping overhead, hippo snouts bobbing among the waves, and giant crocodiles slipping into the greenish water as we cruise by. Off in the distance, we glimpse a freakish sight: gigantic black clouds rising from the water’s surface, as if the lake were on fire. These are African lake flies, explains Rutta, hatching by the millions. But then our pilot notices another kind of cloud forming overhead—storm clouds.
He turns the boat around and heads back, but he’s not fast enough to outrun the storm. The wind whips up, and rain begins pelting our faces. The pilot guns the outboard motor, but that just sends more wat
er sloshing into the boat. The rain beats down harder and harder, and soon we’re plowing through an endless gray curtain of water. “These are three-foot, four-foot swells!” hollers Pete over the engine as the dinghy rocks wildly back and forth in the waves. Suddenly, in the midst of our soggy misery, I start laughing. Maybe it’s the absurdity of the situation, or maybe I’m going insane with fear. Either way, Pete joins in, and Rutta does, too. Here we are, facing a possible watery grave in the middle of Lake Victoria, and we’re cackling like maniacs. And we can’t seem to stop.
We make it back to shore just as the squall moves on. As the sun reemerges from the clouds, we strip to our pants and lay out our waterlogged clothes out on the shore to dry. “I was thinking, ‘Is this a good thing or a bad thing?’ until I heard you laugh,” Pete tells me as we stretch out in the sun, his iPod blasting more 1990s hip-hop. “It’s an example of how laughter signals things are okay.”
Rutta has another interpretation. “It’s omuneepo!” he declares, nodding his head to Biggie Smalls.
When the Kashasha boarding school shut down during the laughter outbreak in 1962, the schoolgirls went home—and along with them went omuneepo. At Rwamishenye girls’ middle school just outside Bukoba, a third of the 154 pupils came down with symptoms after several of the Kashasha students returned to their homes nearby. That school closed, too, and one of the pupils from that institution returned to her village twenty miles away, where she spread the ailment to her family, including a relative who’d walked ten miles to witness the symptoms. Soon two boys’ schools nearby were overrun and shut down, too. “At the time of writing this paper the disease is spreading to other villages, the education of the children is being seriously interfered with, and there is considerable fear among the village communities,” noted Rankin and Philip in their Central African Journal of Medicine article. There’s no indication when, exactly, the laughing finally stopped or how many people were affected, but some reports put the total at approximately 1,000 victims.
