What an ape’s laugh can teach us about human language

There’s something profound that humans and all the other great apes share: We all laugh. 

Now, scientists have determined that our closest relatives laugh with a similar rhythm to us—and that this way of laughing goes back 15 million years. The study opens a window into the past that suggests how laughter, and also speech, has evolved.

“Maybe we don't think about it in everyday life, but we are able to laugh in so many different ways,” says Chiara De Gregorio, a primatologist at the University of Warwick and author of the new study. “And each one of them communicates something about our state.”

De Gregorio and her team compared laughter—known to occur in apes during play—across species of great apes, aiming to understand similarities, differences, and the evolutionary path of human laughter and speech. The findings are reported in Communications Biology. 

The team used recordings from great apes in zoos—four orangutans, two gorillas, three bonobos, and four chimpanzees—as well as four human children, all ranging in age from 6 months to 7 years old. 

The laughs were recorded in two different contexts: during regular play and during tickling. 

In total, the team examined 140 sequences of laughs, analyzing each sound to look for differences and similarities in the rhythm across species. “It was striking,” De Gregorio says. “Once you really focus on that, you see how similar it is to our kind of laughter.” 

In fact, when they were tickled, laughter from both apes and humans was isochronous, meaning that the laughs followed a rhythmic pattern. In other words, the same amount of time passed between each “burst” of the laugh, like the ticking of a clock.

The pattern of that laugh allowed the team to compare this kind of laughter across species. When compared with the ape laughter, the human laughter outpaced other species. And species closer to humans, such as bonobos and chimpanzees, were able to laugh faster than gorillas or orangutans. “The rhythm of laughter is accelerating with evolution,” says De Gregorio.

The similarities between our laughter and that of all other species show that the evolution of these traits might go back to a shared path, all the way to a common ancestor around 15 million years ago. “In a way, still our rhythm is the same of 15 millions of years ago,” says De Gregorio. 

But the differences between humans and other species implies that during our evolutionary path, humans probably evolved with more vocal flexibility in the way we laugh, and the ability to laugh differently depending on the context. This, in turn, might have led to the evolution of speech and language.

By analyzing laughter during play, the team detected another difference. Humans, in fact, were the only species who seemed to be able to modulate laughter based on the context— for example our laughter sounds different during tickling than during play. 

“We are able to laugh in a polite way in front of the queen, but then when we are with our friends at the pub, we can laugh in a totally different way,” De Gregorio says.

Kristin Sabbi, a primatologist at Harvard University who wasn’t involved in the study, says laughter “feels like a very solid link between humans and nonhuman primates.” 

But while the new study add some pieces to the puzzle, some questions remain unanswered, she says. For example, Sabbi notes that an interesting next step would be to investigate how the flexibility of laughter would change over the course of an ape’s lifetime, as this study looked at younger individuals. She would be curious to know how, during their lifetime, great apes might in fact be able to learn and develop more control in their laughter—in short, just like us.