Pant Before the Word

The Stand-Up Spark

Eli: Sophie Scott's first stand-up gig was in a pub in central London. She told the Guardian she stood there thinking, "what have I done?" Then the room laughed. It was, she said, "a great kick when people laughed." And when she came off stage, her main thought was that she wanted to do it again.

Mara: A listener sent us a question that starts right there: why do humans laugh, and do other animals laugh too? Today's angle is why humans laugh and whether other animals laugh too.

Eli: The trail runs from that pub to a lab full of tickled rats, to bonobos and orangutans hearing recorded giggles, and deep into the primate family tree. And one part is still argued over: whether what animals do counts as laughing at all.

Mara: Fitting that the person hooked on the laugh is the one taking it apart.

Eli: That's her day job. Scott is Director of Cognitive Neuroscience at UCL, and she's spent her career on laughter. Her view is that it isn't mainly about jokes. "We use laughter communicatively and to try and deal with tension," she says. "So, for a very simple emotional vocalization, it's an unbelievably complex behaviour for human adults."

Mara: Tension as the trigger, not punchlines. Classicist Inger Kuin points to nervous laughter, the kind people use to smooth over a conversation.

Eli: And then there's the plain part. "It also feels good to laugh," Scott says, and laughter gives people a kick. Same word she used for that night in the pub.

Mara: So, Eli, the kick lands before anyone has picked a joke apart. That leaves a real split: laughter as a clever reply to humour and words, or a play signal far older than either.

The Sidewalk and the Squeak

Eli: Start with the jokes, then. One psychologist spent years noting when adults actually laugh in everyday life. His first lesson was that laughter is, above all, social. Then came the surprise. In 85 percent of the cases he studied, nothing funny came before the laugh. People were just talking.

Mara: Company matters too: Scott reckons people are thirty times more likely to laugh with someone than alone.

Eli: And it spreads on its own. His blunt summary was that laughter is all it takes to set off more laughter. No joke required, no punchline, just somebody else laughing nearby.

Mara: That's a lot of social machinery for a sound Scott called simple. If comedy isn't the source, the origin has to sit somewhere else entirely.

Eli: Jaak Panksepp went looking in rats. Put young rats together and they start tussling at once. But to anyone standing there watching, the play looks silent. Panksepp had spent about six years recording rat play with ultrasonic equipment when, as he recalled it, he woke one morning with a thought: "My God, what if that's laughter. What if that sound is laughter?" He and a colleague went and tickled the rats straight away.

Mara: They listened with a bat detector; ultrasonic vocalizations sit too high for human ears.

Eli: Under the fingers, the rat made the same chirp it made in play, only louder and more continuous. When Panksepp stopped, one rat followed his moving hand. In one experiment, tickling drew more than twice as many calls as play the rats started themselves. It is contested whether those calls sit around fifty kilohertz, both under tickling and in rough-and-tumble play with other rats.

Mara: On Panksepp's reading, the rats ask for it: tickling works as a reward worth learning for.

Eli: That word, laughter, is exactly where the argument begins. Whether those chirps are laughter, or just the noise rough play makes, is still fought over.

Play Calls and Optimistic Choices

Mara: Those chirps have an address in the brain. In a later study, researchers let rats get used to a new space for a few days, then played chase the hand with them and tickled their backs and bellies. Tickling and play both drew strong responses in the same spot: the lateral column of the periaqueductal gray. That's an old hub in the midbrain that handles instinctive responses, calls included. Quiet that column, and play falls apart and contested fifty-kilohertz calls drop off.

Eli: Which is Panksepp's old argument: physical play comes from the brain's most primitive parts.

Mara: And the sound reaches whoever hears it. Kea parrots have a play call. Researchers played recordings of it, and kea that weren't playing started. Many of them didn't join a game already going. They found another idle bird, or played with an object, or launched into aerial acrobatics. That made the kea the first non-mammal reported to have an emotionally contagious call. Laughter setting off laughter, in a bird.

Eli: Though that count is contested, one review reported play sounds in at least sixty-five species.

Mara: Mostly mammals, but birds too: two parrot species and Australian magpies.

Eli: Then the apes. One team played bonobos recordings of other bonobos laughing, or of wind, and then offered an ambiguous grey box that might or might not hold a reward. After hearing laughter, the bonobos approached those boxes more often. Erica Cartmill, one of the researchers, said that optimism suggests the sound alone put them in a positive emotional state. It was described as the first study to show cognitive and emotional effects of ape laughter like those seen in humans.

Mara: So a recorded laugh tilted the choice before the bonobos touched anything.

Eli: In 2026 a team tried orangutans. Right before showing them bowls, the researchers played either orangutans playing and laughing, or sounds like wind. Each soundtrack went with one of two coverings over the food. On the fifth day, both bowls held a treat, one under each covering, and the apes had to pick. Overall they went for the laughter bowl. Four of the six showed a clear preference. The lead researcher said that, hearing others clearly having a good time, they effectively ordered whatever the others were having.

Mara: Six orangutans is a small sample, and a food choice isn't a feeling.

Eli: How far back in the primate line it runs, and whether it came before words, is still open.

The Fifteen-Million-Year Turn

Mara: Here's how one team went after the depth. They recorded tickling and play with young orangutans, gorillas, chimpanzees and bonobos, and with human infants, all with people they knew. They pulled out 140 laughter sequences and measured the gaps between bursts. Then came a phylogenetic analysis, which means sorting traits onto an evolutionary family tree. The tree built from laughter matched the one geneticists had already drawn for apes and humans.

Eli: So the laugh carries the family tree inside it.

Mara: That's the researchers' reading: a shared origin. The basic rhythm, evenly spaced bursts, is estimated at about fifteen million years old. One of the study's authors, a primatologist, put it simply: we've been laughing much like the other great apes for that whole stretch.

Eli: And every living great ape still does it, mostly in one-on-one play.

Mara: Where it came from is breath. The idea is that laughter grew out of the laboured breathing of rough play. A chimp's pant-pant and a human ha-ha both mark that rowdy origin. Play calls in primates and other mammals often include panting. And that kind of call may go back to the ancestor humans share with the great apes.

Eli: That's what Scott's phrase, emotional vocalization, really names. A burst of sound that carries a feeling out with no words at all.

Mara: A feeling made audible. No grammar required.

Eli: And built in, not learned. The kick Scott described from that stand-up audience runs on a pant older than humans. It's also why those bonobos and orangutans reacted to recordings: they were hearing a signal their ancestors already shared.

Mara: The rhythm hasn't stood still, though. Humans laugh faster than the great apes. Chimpanzees and bonobos laugh faster than gorillas and orangutans. And timing gets more variable in the closer relatives, which the researchers read as growing control. As one author put it, the rhythm of laughter is accelerating with evolution.

Eli: Jonathan Marks and Marina Davila-Ross stress that among the great apes, only humans tune laughter to context.

Mara: Humans even laugh faster when tickled than in play. Then the dates. Human-like laughter most likely appeared with the genus Homo, about two and a half million years ago. And speech comes far later. Its earliest likely date is around six hundred thousand years ago, with archaic humans. By then, laughter had been running through most of our genus's history. So laughter wasn't a by-product of talking. It was already old when speech arrived. Researchers hypothesize that early hominins, our ancestors on the human branch, co-opted ancestral play panting to bond larger social groups as vocal grooming replaced physical touch.

Eli: What's still unknown is how one brain runs an ancient pant and much newer speech through the same throat. Two systems sharing one voice is the puzzle left standing.

Dual Circuits and Vocal Grooming

Mara: Greg Bryant and a colleague describe two systems. Spontaneous laughter, the kind that escapes, comes from a vocal system shared across mammals. Volitional laughter, the deliberate kind people use to keep a conversation moving, comes from the speech system, which is unique to humans. The old route runs through that periaqueductal gray and down to nuclei in the medulla, at the base of the brain. There, motor neurons switch breathing from passive to active and set the larynx and pharynx. Mechanically, a laugh is short repeated bursts of breath pushed out. The ancestral pant, still wired in.

Eli: So the giggle that escapes and the polite chuckle aren't even the same machine.

Mara: And that older network is involved in other emotional expressions too, like crying.

Eli: And Scott says laughter happens mainly around members of our own species, particularly the people we know and like. Friends, in other words. One brain-scanning study used PET, positron emission tomography, which tracks chemical activity, on people who had watched comedy with close friends. Afterward, their brains showed endorphins being released. Those are the body's own feel-good chemicals, the kind that can ease pain or stress. A 2017 study put the finding right in its title: "Social laughter triggers endogenous opioid release in humans."

Mara: That's the tension Scott talked about at the start, with chemistry behind it.

Eli: And it scales. Laughing together can set off endorphins in nearly three times as many people as grooming does in one interaction. That's the heart of the vocal grooming idea. Robin Dunbar argues that shared pleasures, laughing, singing, dancing and eating, drive social bonding through endorphins. A hand can only groom one back at a time. A laugh reaches the whole group at once.

Mara: In people, a scanner can catch that rush. In a tickled rat or a laughing ape, there's still no way to ask what it feels like from the inside.

The Deep Mammalian Chorus

Eli: So here's where the listener's question lands. People laugh mainly as an innate social play signal, run by ancient brain pathways, that eases tension and binds a group. And other animals have something like it. Primates and rodents show resembling behaviours and share the circuitry underneath. Their play calls tell a partner that rough play is harmless, and help keep it from tipping into a real fight. Peter Gärdenfors goes further: "Almost all mammals laugh silently or in other ways to humans. The exceptions are elephants and sea lions, which laugh out loud, just like us."

Mara: And that psychologist's lesson holds: like small talk, laughter solidifies friendships and pulls people in.

Eli: The live fight is over one word, homologous. It means two signals inherited from the same ancestor, not just alike by coincidence. Jaak Panksepp, Frans de Waal, Gärdenfors and Greg Bryant read rat chirps and ape pants that way, sharing deep circuitry with human laughter. Bryant describes "a phenomenon once thought to be particularly human" that turns out tied to species separated from humans "by tens of millions of years."

Mara: Eli, Marks and Davila-Ross hear distinct reflex sounds there, and warn against calling them laughter.

Eli: And a shared sound isn't a shared sense of humour. Whether animal minds include what people would call one is unknown. Scott's night in that pub shows the human end of it: a crowd laughing together, and a kick riding on wiring older than speech. Two things to watch. Whether comparative cognition research can tell if animals feel amusement at all. And whether genetic and acoustic studies can link a rat's chirp directly to a primate's laugh.

Mara: For more on the sounds themselves, look into emotional vocalization.

Eli: Follow science with us as researchers explore how ancient signals shape human connection.

Mara: That's all for this one. I'm Mara.

Eli: And I'm Eli. Thanks for listening to Angle. Until next time.